Remarques intéressantes
Article de Friedman : prognostic of initial endodontic therapy
Also, intracanal medicaments used in the studies may have been ineffective. Intracanal medicaments
are critical for controlling root canal infection (29,56–61), but not all are equally effective. The
antimicrobial efficacy of ‘classical’ medicaments, such as camphorated phenol and
paramonochlorophenol, iodine potassium iodide and formocresol, is shortlived (62–64), and may be
insufficient for in-between-sessions disinfection of canals associated with apical periodontitis (59).
These ‘classical’ medicaments have been used in many studies (3, 9–12, 14,
15, 17–19, 24), where they may have compromised the results. The more effective calcium
hydroxide.
Healing of apical periodontitis is a dynamic process, and sufficient time is required to evaluate its
progression and completion (1, 29, 42). Observations after a short follow-up may demonstrate only
signs of healing (1, 37, 40, 42) (Fig. 4). Therefore, results of studies with short follow-up periods
(Table 1) may be skewed and not reflect the true prognosis (1, 54, 55,
71). Follow-up of at least 1year is required to reveal meaningful changes (34, 42), but extension of
the follow-up to 3 or 4years (Fig. 5) may be required to record a stable treatment outcome (1, 17, 29,
42,
Because with time, endodontically treated teeth are subject to adverse effects of periodontal and
restorative
deterioration, extensive follow-up periods are more likely to reveal the influence of those effects
on the outcome. Comparing the 4-year and the final follow-up, Strindberg (1) observes a difference
in healing rates of 16%.
Clearly, then, the poorer prognosis can be ‘blamed’ on the infection, but not necessarily on the
overfilling.
The goal of initial endodontic therapy is to cure apical periodontitis (80). When radiolucency is still
present at follow-up, it is an expression of apical periodontitis the same disease the initial therapy
aimed
to cure.
However, it should be taken into account that, because all endodontically treated teeth remain
constantly challenged by intraoral microorganisms, development of apical periodontitis in the future
remains a possibility for all teeth, even those that are completely healed at one point after therapy.
Therefore, periodic follow-up of endodontically treated teeth is advocated as a viable routine.
Persistance de la maladie = le plus souvent due à une infection résiduelle du système canalaire. Mais l’extrusion
de matériel étranger et la présence de kystes peuvent mimer une vraie parodontite apicale. Mais cela est peu
fréquent. Une parodontite apicale persistante est tout d’abord causée par une infection (première cause !), Les
sites microbiens peuvent être différents :
1.
2.
Le plus souvent les MO sont présents dans le système canalaire malgré le traitement ou viennent
envahir les canaux après traitement (restauration coronaire non étanche).
Des Mo spécifiques peuvent s’établir dans les tissus péri-apicaux (actinomyces israelii, Arachnia
propionica)
3.
MO d’autres espèces à l’extérieur du système canalaire, dans les tissus péri-apicaux, sur la surface
radiculaire, dans des lacunes du cément, dans des biofilms microbiens ressemblant à de la plaque ou
sur des débris de dentine extériorisés lors du traitement.
Retenir que la cause principale est l’infection radiculaire !
Friedman = la parodontite apicale is « universally considered a disease requiring therapy », qu’il y ai
ou pas des symptômes. De la même manière une parodontite apicale persistante après traitement
ne peut pas être considérée comme un succès seulement parce que la dent est asymptomatique :
« it is the same disease, still requiring management ». La guérison est supposée être totale. Donc
tout reste de radiotransparence doit être considéré comme une parodontite apicale persistante ou
récurrente. Cependant la guérison de lésions péri-apicales de grandes étendues peuvent laisser des
cicatrices fibreuses (persistance d’une radiotransparence).
Succès clinique = disparition des symptômes et plus grande liberté quant au cliché radiographique
Une définition plus stricte impose un succès clinique et radiographie (radiotransparence acceptée
seulement si présente autour de l’éjection de matériel).
Le problème de la définition la moins contraignante est qu’une parodontite apicale est fréquemment
asymptomatique (2, 26 ; 47, 46)
Toronto study, phase 1 :
The quality of a clinical study is primarily concerned with validity and relevance (3). The quality
parameters can be grouped into four categories as follows:
(a) Cohort: this should be defined at the inception of the study and clearly described. The pattern of
referral and case-selection criteria should be described (4). At the end point of the study, the entire
inception cohort should be accounted for (4). The sample size may be required to exceed a certain
threshold.
(b) Exposure (intervention, treatment): treatment providers and procedures should be clearly
described. Procedures considered to be irrelevant or unacceptable may be excluded.
(c) Outcome assessment: outcome dimensions (5) should be clearly defined. Measures used to assess
these dimensions should be objective and applied consistently by properly calibrated examiners
with established reliability. The examiners should be blinded or masked and different from the
providers of treatment. Direct visual comparisons of radiographs, e.g. preoperative and at follow-up,
should be avoided. The follow-up period should be long enough to capture the completion of the
healing process in the majority of the study sample.
(d) Data analysis and reporting: potentially confounding prognostic factors should be controlled, or at
least observed, and recorded.
Being frequently related to traumatic occlusion, food impaction, or periodontal disease, tenderness
to percussion was allowed if unaccompanied by any other clinical sign or symptom
The fact that state-of-the-art treatment did not dramatically improve the outcome once more
highlighted the complexity of treating apical periodontitis. Apparently, prevention or treatment of
this disease cannot be improved merely by changing treatment techniques.
Because apical periodontitis results from interactions between microorganisms, their environment
and the host immune system (19), only use of effective modifiers of any of these three factors
mightsignificantly improve the outcome of treatment.
Toronto study, phase 2 :
The results regarding initial treatment for Phase I (17) revealed that the outcome (81% overall healed
rate) was
significantly better in teeth treated without the presence of AP. With AP present, the outcome was
significantly better for singlerooted than for multirooted teeth. Several factors were associated with
a large (_10%), albeit statistically nonsignificant healing rate differential. Two factors were of
particular interest: (a) number of treatment sessions in teeth with AP; and (b) treatment technique:
flared canal preparation and vertical compaction of warm guttapercha
(FPVC) as described by Schilder (18, 19), or modified step-back preparation and lateral compaction of
gutta-percha (SBLC) (20 –22). The lack of significance for some of those factors is reflective of
insufficient power because of the limited sample size of the Phase I study (17).
Based on the Phase I study results (17), it was hypothesized that the healed rate would be
significantly higher for: (a) single-rooted than multirooted teeth; (b) treatment using FPVC than SBLC
technique; and (c) treatment of teeth presenting with preoperative AP in two or more sessions than
in one session.
reflect absence (PAI ≤ 2) or presence (PAI ≥3) of AP.
Outcome assessment was based on clinical and radiographic measures, and the periapical tissues
classified as “healed” (absence of AP, signs, and symptoms other than tenderness to percussion), or
as having “disease” (presence of AP, signs, or
symptoms). Teeth presenting without clinical signs or symptoms were considered “functional”
regardless of the PAI score
The bivariate analysis (Table 2) identified only two statistically significant associations with a higher
healed rate for treatment without preoperative AP than with AP, and treatment using FPVC than
SBLC. Five additional factors were associated with “large” (_10%) healed rate differentials that were
not statistically significant.
Of 70 teeth treated with preoperative AP, 57 (81%) had healed. Stratified analysis (Table 4) identified
only one statistically
significant association with a higher healed rate for treatment using FPVC than SBLC. Eight additional
factors were associated with large healed rate differentials that were not statistically significant.
Thus, the absence of symptoms is insufficient as a measure of healing. Patients should be
encouraged to attend followup examinations after endodontic treatment to assess the outcome, even if they are asymptomatic.
Nevertheless, absence of
symptoms does allow the tooth to remain “functional.” This dimension of outcome should not be
overlooked when communicating to patients the benefits associated with endodontic treatment visà-vis tooth extraction and replacement.
The healed rate (combined sample, 85%) differed significantly for preoperative AP (absent,
93%; present, 79%), treatment technique (flared preparation and vertical compaction, 90%; stepback
preparation and lateral compaction, 80%), gender (females, 90%; males, 79%), number of roots (1–
92%; >2–81%), and root-filling length (adequate, 87%; inadequate, 77%). Logistic regression revealed
increased risk of disease for preoperative AP (odds ratio _ 3.3) and technique (odds ratio _ 2.3). This
study confirmed AP and highlighted treatment technique as the main predictors of outcome in initial
treatment.
It is noteworthy that 45% (combined sample) of the teeth having disease at follow-up demonstrated
reduced lesions
relative to the preoperative size. Although size reduction does not suggest that the lesion has healed,
it may be a sign of slowprogressing healing. In a recent study (28), as many as 6% of teeth that had
persistent AP 10 yr after treatment have been observed to completely heal 10 to 17 yr later. This
finding should be communicated to patients to emphasize the need for extended follow-up as long as
complete healing has not been observed.
Clearly then, the significant effect of the treatment technique on outcome was specific to teeth with
preoperative
AP. The FPVC technique, as taught in the Graduate Endodontics Clinic at the University of Toronto,
strictly adhered
to the original description by Schilder of the cleaning and shaping protocol (19) and vertical
compaction of warm guttapercha
(18) using Kerr Pulp Canal Sealer (Kerr, Romulus, MI). The main alternative technique taught (SBLC)
comprised stepback
cleaning and shaping (20), often modified to include extensive apical reaming (21), and lateral
compaction of guttapercha (22) with Roth’s 801 sealer
Thus, the technique described by Schilder (18, 19), as a complete concept, yielded a better outcome
than SBLC. However,
because this study was not designed specifically to compare the two treatment techniques, e.g. it
was not a randomized,
controlled trial, the result can only be considered as suggestive.
The outcome differed for single-rooted and multirooted teeth, as previously observed in the Phase I
study (17) only for teeth with preoperative AP. Whether reflecting the complexity of eliminating root
canal infection in the multirooted teeth or just the use of the tooth as the unit of evaluation (5), this
finding suggested a practical application: clinicians can better appraise patients of the prognosis by
citing the expected healing rate for the specific tooth type, rather than an average healing rate for
single-rooted and multirooted teeth. It should be noted, however, that this finding was contrary to
that of Strindberg (6) and Engström et al. (7). Gender has not been found to significantly affect the
outcome in the selected studies (11, 17). The potential confounding effect of other factors on this
finding was assessed and excluded (tests not shown), and no explanation could be offered for this
observation.
Indeed, the largest healing rate differential related to root-filling length (15%) was observed among
teeth with
AP. It has been suggested that this adverse effect could be a result of over-instrumentation and
subsequent transportation of contaminated debris periapically (5, 11, 34), rather than the periapical
extrusion of the root-filling material per se.
Toronto Study phase 3
Logistic regression performed on the combined phases I-III sample identified significant (p _ 0.05)
outcome predictors: preoperative AP (OR _ 3.5; CI 1.7-7.2; healed: absent, 93%; present, 80%),
number of roots (OR _ 2.2; CI 1.0-4.7; healed: 1 - 92%; _2 - 83%), and intraoperative complications
(OR _ 2.2; CI 1.1-4.5; healed: absent, 88%; present, 76%). Treatment technique (OR _2.8; CI 1.3-6.1;
healed: Schilder, 89%; alternative, 73%)
was suggested as an outcome predictor in teeth with AP, requiring confirmation from randomized
controlled
trials.
Toronto Study phase 4
When pooled with Phases 1–3, 439 of 510 teeth (86%) were healed. Logistic regression
identified 2 significant (P_ .05) preoperative outcome predictors: radiolucency (odds ratio
[OR], 2.86; confidence interval [CI], 1.56 –5.24; healed: absent, 93%; present, 82%) and
number of roots (OR, 2.53; CI, 1.25–5.13; healed: single, 93%; multiple, 84%). In teeth with
radiolucency, intraoperative complications (OR, 2.27; CI, 1.05– 4.89; healed: absent, 84%;
present, 69%) and root-filling technique (OR, 1.89; CI, 1.01– 3.53; healed: lateral, 77%;
vertical, 87%) were additional outcome predictors. A better outcome was suggested for teeth
without radiolucency, with single roots, and without mid-treatment complications. The
predictive value of root-filling technique in teeth with radiolucency requires validation from
randomized controlled trials.
Preoperative apical periodontitis was identified as an outcome predictor in all 3 phases (19, 22, 25),
as in the majority of previous studies (6, 7, 13, 18, 21, 23, 24). More than 1 root in the treated tooth
was identified in the latter 2 phases (22, 25), and occurrence of a mid-treatment complication was
identified in the most recent phase (25).
The multivariate analysis (Table 4) identified 2 preoperative significant predictors of disease
persistence, presence of radiolucency (odds ratio [OR], 2.86), and 2 or more roots (OR, 2.53).
Stratified multivariate analysis of the subsample of teeth with preoperative radiolucency (Table 5)
identified 2 significant predictors of disease, midtreatment complications (OR, 2.27) and root-filling
by using LC (OR,1.88).
Therefore, patients who are considering initial treatment and alternative extraction and replacement
should be informed of the 86% chance for the treated tooth to heal completely, an additional 5%
chance for incomplete healing, and 95% chance for functional retention 4 – 6 years after initial
treatment.
Indeed, in a study spanning 27 years of follow-up (32), approximately 6% of teeth appeared healed
only during the second or third decade after treatment.
The finding of a better healed rate in single-rooted teeth than in multi-rooted teeth (one, 93%; two
or more, 84%) was not surprising, considering that the evaluated unit was the tooth, not the
individual root. In multi-rooted teeth, the risk for persistence of disease is proportional to the
number of roots. Therefore, the results might have been inherent to the method of analysis, but they
might also reflect the greater challenge encountered when the anatomically complex, multi-rooted
teeth are treated.
In any event, clinicians should consider the 11% difference in outcome when projecting the prognosis
for single-rooted and multirooted teeth.
By their nature, these complications can either promote infection or interfere with its elimination;
therefore,
iatrogenic complications should be avoided to maximize the outcome of treatment in teeth with
apical periodontitis.
Vytaute Peciuliene, Jurate Rimkuviene, Rasma Maneliene, Deimante
Ivanauskaite : Apical periodontitis in root filled teeth associated withthe
quality of root fillings. Stomatologija, Baltic Dental and Maxillofacial
Journal, 8:122-6, 2006
Periapical Index (PAI) established by Orstavik et al. based on the histological work of Brynolf allows
standardization of the different categories, and thus comparisons between studies [9, 12]. Its
reliability was established by further investigations [2, 3, 4]. However, in order to differentiate the
normal status from the pathologic, the authors proposed a cut-off at a score of 2, since PAI>2 was
considered to be indicative of periapical pathology. Score of 2 corresponds to an image with a
localized widening of the ligament and can be associated signs of bone modifications which may be
interpreted as an ongoing healing process, an established state of irritation, or an evolution toward a
pathological state.
Since peak incidence of healing or emerging chronic apical periodontitis is at 1 year, the risks of a
questionable image developing a more advanced lesion are increased [1]. Periapical lesions are in
general radiographically underestimated, since the cortical bone must have a 30-50% mineral bone
loss to be detectable [13]. Moreover, as the PAI system was established for maxillary anterior
incisors, where the cortical bone is thin, the risk of underestimation of lesions with a PAI>2 is
increased.
A comparison of the quality of root canal treatment in two Danish
subpopulations examined 1974–75 and 1997–98
The periapical status of root-filled teeth depends on both the quality of the root canal treatment and
of the coronal restoration
(Ray & Trope 1995, Kirkevang et al . 2000b).
Periapical bone was judged sound if the PAI score was 1 or 2 and diseased if the PAI score was 3, 4 or
5 (Table 1)
The quality of the lateral seal in the two groups is shown in Table 6. Only about one-quarter of the
teeth in group 1 had adequately sealed root canals, whereas in group 2 almost half of the teeth were
judged adequately sealed. The difference was highly significant (P < 0.001). In Table 7, the length of
the root filling in the two groups is shown. Less than half of the root fillings in group 1 had adequate
length, whereas in group 2 more than half of the root fillings were judged adequate (P <0.001). The
rate of pulpotomies in group 1 was 5.3%, and in group 2 it was 1.1% (P< 0.001). The periapical status
of the two groups is shown in Table 8.
More root fillings appeared to be adequate during 1997–98 than during 1974–75, and fewer
pulpotomies were found in 1997–98. The quality of the root fillings during 1997–98 was found to be
at the same level as in a study of randomly selected individuals living in Aarhus County (Kirkevang et
al. 2000b). This supports the assumption that the technical quality of endodontic treatment is less
patient dependent.
Another explanation could be a change in the treatment strategy of apically infected teeth toward
more conservative treatments, where dentists hesitate to extract teeth with periapical lesions, but
extend the period of conservative treatment and try to treat/retreat them. This would result in a
higher rate of ‘diseased’ or ‘dubious’ teeth in a population. Other studies have found a slight
improvement in periapical status over time (Eckerbom et al. 1989, Petersson 1993). The fact that the
periapical status of root-filled teeth in the present study had not improved with the better quality
treatment indicates that the quality of the root fillings is not the only parameter that influences the
periapical status. The quality of the root filling, as depicted by radiography, may be of importance for
the outcome of the treatment, but it does not provide any information on microbial contamination
that will probably play an important role in the outcome
Although the two populations under comparison were not identical with respect to disease
frequency, the technical quality of root canal treatment had improved from 1974 to 1997
Endodontic infection: Some biologic and treatment factors associated with
outcome
Optimal prognosis for endodontic treatment is dependent on the successful elimination of
microorganisms from the infected root canals.1-5 To optimize successful outcome, the focus of
endodontic treatment is directed at disinfection through chemomechanical debridement and
biomechanical preparation, followed by a quality obturation of the root canal system. Finally, it is
necessary to preserve the remaining tooth structure by timely placement of an appropriate
permanent restoration.
Complete disinfection of the infected pulp space is difficult, and there is still no predictable, effective
procedure
to achieve this to maximize the successful treatment outcome. During disinfection, it is essential that
optimal
instrumentation be delivered, especially in the most apicalarea of the root canal.
Studies on endodontic prognosis11 and root canal anatomy12-14 suggest that the optimal apical
terminus is not the same for vital and non vital teeth.
After single-tooth rubber dam isolation, the tooth and rubber dam were disinfected with 30% H2O2
and 5% tincture of iodine.
2% iodine potassium iodide was used for additional disinfection as a final rinse at each treatment
session in cases of necrotic pulp with a periapical lesion. Before obturation, the canals were irrigated
with 70% alcohol and completely dried.
the risk of failure increases as the working length decreases (away from the radiographic apex). The
interaction between the preoperative periapical diagnosis and the working length level was
evaluated (Table VI). This model demonstrates a significant relationship between working length
level and periapical diagnosis
The effect of preoperative periapical diagnosis, working length, and density. Diseased periapex,
decreasing working length (away from the radiographic apex), and fair/poor density all
simultaneously increase the risk of failure For necrotic cases, it appears that success is enhanced
when the root canal is instrumented and obturated closer to the radiographic apex, thereby
effectively removing any remaining infected necrotic tissue. In contrast, for vital cases, the outcome
is most favorable when the distance from the apex is maintained short of—but within 2 mm of—the
radiographic apex.20 The question arises of whether instrumentation of necrotic cases with
periapical disease carried out closer to the radiographic apex would have a success rate be similar to,
for example, normal pulp/normal periapex or pulpitis/normal periapex. In other words, could we
improve prognosis and equalize it for all diagnostic categories if we correctly determine the optimal
level of instrumentation? A review of Table II reveals that the success rates for different diagnostic
categories, taking into consideration the pulpal and periapical diagnosis, are significantly different.
This table also clearly shows that the optimal level of instrumentation is different for different
diagnostic categories. However, necrotic teeth with periapical destruction that are instrumented
close to the apex still have a significantly lower success rate than the vital cases with normal
periapex. This indicates that there are other forces at work in this complex system, independent of
mechanical factors such as apical instrumentation terminus. These factors are most likely associated
with the presence or absence of dentin infection and periapical complications.21
It is evident from the data presented in Table II that endodontic outcome is dependent on the
preoperative periapical diagnosis, independent of the level of instrumentation or obturation. The
favorable outcome, however, is enhanced by the differential level of instrumentation for different
periapical conditions. From this we conclude that the endodontic outcome is primarily influenced by
preoperative periapical diagnosis For roots/teeth with diseased periapex, the failure rate was
approximately 20% higher if the density was fair/poor. In the series of the logistic regression models,
we first analyzed the simultaneous effect of 2 factors: preoperative periapical diagnosis and working
length level (Table V). This model shows that the risk of failure increases as the working length
decreases (away from the radiographic apex). Compared with normal periapex, the risk of failure for
teeth/roots with diseased periapex is higher for each level of working length (odds ratio _ 4.8; P
_.0001). For every millimeter loss in working length (away from the radiographic apex), the odds of
failure increase by approximately 14%. This model implies that, for normal periapex, the working
length level does not matter and that any observed changes in failure risk are random. Furthermore,
this model shows that the average rate of failure, across all levels of working length, is not affected
by the working length in teeth/roots with normal periapex. A decrease in working length only
increases the risk of failure in those with diseased periapex. Given the same periapical diagnosis and
working length level, teeth/roots with a poor/fair density of obturation have more than double the
risk of failure (odds ratio _ 2.18; P _.03). Regardless of density, a decrease in working length is
associated with increased failure only in teeth/ roots with diseased periapex.
It is now an established fact that teeth/roots with apical periodontitis have, on average, a rate of
success that is 10% to 20% less than that in teeth/ roots without apical periodontitis.2,10 The
prevalence of apical periodontitis increases with age, and by 50 years of age, 1 out of 2 individuals
will have experienced this disease.23 The morbidity associated with apical periodontitis is higher in
patients with certain systemic diseases than in the general population.24
Endodontic outcome is a multifactorial phenomenon.
Internet
Apexification is a method of inducing a calcified barrier at the apex of a nonvital tooth with
incomplete root formation. Apexogenesis refers to a vital pulp therapy procedure performed to
encourage physiological development and formation of the root end
La povidone iodée est un complexe chimique soluble dans l'eau, composé d'iode et de
polyvinylpyrrolidone (PVP).
La povidone iodée est employée dans la pharmacopée comme antiseptique topique. Le médicament
est commercialisé sous le nom Bétadine® en France, Belgique et Suisse.
Le diiode I2 dissous dans l'éthanol (« teinture d'iode ») ou dans une solution aqueuse d'iodure de
potassium KI (solution de lugol) est également utilisé en pharmacie et en milieu hospitalier comme
antiseptique puissant. Il laisse des traces jaunes sombres caractéristiques sur la peau. Il existe
également des composés organiques où l'iode est lié, tels que la povidone iodée (Bétadine ou IsoBétadine).
La teinture d'iode est, en médecine, un antiseptique puissant composé d'iode dissous dans l’alcool, plus
précisément dans l'éthanol, généralement à raison de 10 %. Il existe aussi des mélanges à 2 %, 3 % et 7 %. C'est
un élément essentiel d'un kit de survie utilisé pour désinfecter et assainir.
Cutting efficiency of 3 different instrument designs used in
Reciprocation, Jeffrey Wan, BS,a Brian J. Rasimick, BS,b Barry L.
Musikant, DMD,c and Allan S. Deutsch, DMD,c,d South Hackensack, NJ,
and New York, NY
With advancements in technology, endodontic instruments today come in a variety of designs, each differing in
cost, performance, and safety. One important attribute is the cutting efficiency of an instrument.
Cutting efficiency can be measured with several different techniques.1-4 One accepted method is to measure by
weight the amount of dentin cut by the instrument under a reproducible procedure.5-7
An instrument’s flute design may be a determining factor of its cutting efficiency.8 Two major classes of
endodontic instruments are reamers and files. Files are generally machined or twisted tightly to exhibit flutes that
run more horizontal to the cutting surface, whereas reamers exhibit flutes directed more vertically. At the same
cutting length, files have a greater number of flutes than reamers, which may have an effect on cutting
efficiency. Other parameters have been observed by previous studies to affect cutting efficiency, including
including surface treatment, cross-sectional area, sterilization, rake angle, tip design, and metallurgical
properties.7-14 However, although extensive studies have been conducted on the cutting efficiency of rotary
endodontic instruments, there is a need for studies investigating the cutting efficiency of reciprocating systems
and flatsided instruments.
All 3 instrument types
were tested in reciprocal motion using an Endo-Express
4:1 reciprocating handpiece (Essential Dental Systems)
operating at 2500 rpm.
SafeSiders was found to cut significantly more than K-Files and K-Reamers (P _ .026), whereas K-Files and KReamers were not found to be significantly different (P _ .63).
Studies observed a significant difference in cutting efficiency between machined and twisted instruments.
15,16 SafeSiders demonstrated a greater cutting efficiencythan either K-Files or K-Reamers. This may be
attributable to the smaller cross-section of the SafeSider as a result of the integration of a flat side. According to
Camps and Pertot,17 a smaller cross section creates more space between the instrument and the canal walls. This
extra space allows for more debris collection, which facilitates easier removal. Larger cross sections may not
provide enough space for debris to be displaced. As such, the debris impedes the instrument from cutting more
dentin. The flat-sided feature may also increase cutting efficiency by introducing another cutting edge. However,
this conclusion can neither be confirmed nor denied by this study.
All instruments were operated under reciprocal cutting, whereby the cutting flutes oscillate back and forth about
an axis that is parallel to the direction of cutting.Under this system, cutting efficiency improves as the angle
between the cutting edge and the long axis of the instrument decreases.18 This would seem to favor reamers over
files, as reamers exhibit flutes that are more vertical than those found in files. The results of this study do not
support this supposition. Studies have reported smear layer thicknesses between 0.9 and 3.0 _m.23,24 The amount
of dentin contained in the smear layer is less than 1.5% of the amount of dentin removed during instrumentation.
The results of this study conclude that SafeSiders stainless steel 40/0.02 instruments exhibit a greater cutting
efficiency on dentin than K-Files and K-Reamers of the same size and taper. K-Files and K-Reamers display a
similar cutting efficiency. Cross-sectional area may be a determining factor on cutting efficiency. Pitch length
does not seem to have an effect on cutting efficiency.
Assessment of apically extruded debris produced by the singlefile ProTaper
F2 technique under reciprocating movement Gustavo De-Deus, DDS, MS,
PhD,a Maria Claudia Brandão, DDS, MS,b Bianca Barino, DDS, MS,b Karina
Di Giorgi, DDS, MS,b Rivail Antonio Sergio Fidel, DDS, MS, PhD,c and
Aderval Severino Luna, PhD,d Rio de Janeiro, Brazil
No significant difference was found in the amount of the debris extruded between the conventional sequence
of the ProTaper Universal NiTi files and the single-file ProTaper F2 technique (P _ .05). In contrast, the hand
instrumentation group extruded significantly more debris than both NiTi groups (P _ .05).
Conclusions. The present results yielded favorable input for the F2 single-file technique in terms of apically
extruded
debris, inasmuch as it is the most simple and cost-effective instrumentation approach. (Oral Surg Oral Med Oral
Pathol Oral Radiol Endod 2010;110:390-394)
The use of the singlefile NiTi technique to prepare the whole root canal is very advantageous, because the
learning curve can be considerably reduced with the reduction of the endodontic armamentarium. Moreover, the
single-file NiTi technique tends to be more cost-effective than the conventional multifile NiTi rotary systems.
The amount of material extruded from the apical foramen is one of the main concerns related to an
instrumentation technique. Dentin debris, pulp tissue remnants, microorganisms, and intracanal irrigants may be
extruded from the apical foramen during canal instrumentation. Extrusion ofthese elements may cause undesired
consequences,such as induction of inflammation and postoperativepain and delay of periapical healing. 6,7
Although allinstrumentation techniques apically extrude someamount of debris, 8 there are notable differences
among the techniques. It is worthwhile to note that,while apical extrusion of dentinal debris and irrigantshas
been observed with the use of all presently known root canal preparation techniques and instruments, less
dentinal debris extrusion was associated with the use of motor-driven rotary instruments.9,10 Because rotary
instruments can differ greatly in their design, type of blades, use, number of files, and kinematics, different
amounts of apically extruded debris can be found between the systems. 11
Conventional crowndown hand-file instrumentation was used as a reference. The null hypothesis tested was that
there are no differences in the amount of debris extruded apically between the 2 ProTaper techniques.
The apical third was prepared with Flexofile (Dentsply/Maillefer) sizes 50, 45, 40, 35, 30, and 25 at
working length (WL) using the balanced force movement.14
Based on the statistical results, no significant difference was found in the amount of the debris extruded between
the conventional sequence of the ProTaper Universal NiTi files and the single-file ProTaper F2 technique (P _
.05). The hand instrumentation group extruded significantly more debris than both of the other NiTi groups (P _
.05). The present study showed no significant difference in the amount of debris extruded between the
conventional sequence of the ProTaper Universal NiTi files and the single-file ProTaper F2 technique.
Therefore, the null hypothesis was plainly accepted. The improved apical control of debris extrusion promoted
by both NiTi techniques is in line with earlier reports.9,10,16 Among several hand-instrumentation kinematics, the
balanced force technique is regarded to promote less apical extrusion of debris.17 Therefore, the balanced
force technique was chosen to be used as the reference for comparison in the present study
In the present experimental design, 2 different variables were present in the NiTi groups: the number of files
used and the movement kinematics. Therefore, it is not possible to isolate the influence of each variable on the
present result. The experimental design used in this study is appropriate, because the purpose was not to
determine the relationship between the number of files or the movement kinematics with the amount of debris
extruded apically.
However, it can be speculated that the canal preparation of singleroot teeth tends to extrude less debris, because
the cleaning and shaping procedures are easier and more predictable.
From a clinical point of view, the present results are favorable for the single-file F2 technique, inasmuch as it is
the most simple and cost-effective instrumentation approach. However, apical control of extruded debris is just 1
aspect that an instrumentation technique needs to have tested. Other factors of the root canal preparation with the
single-file F2 technique still require solid laboratory- based tests before the indication of large and longitudinal
clinical studies; researching the involvement of the risk zone in the mesial root of mandibular molars, apical
transportation, debridement ability, and fracture susceptibility all represent further priorities of research for the
F2 single-file technique.
The reciprocating movement is a clockwise (CW) and counterclockwise (CCW) movement. The ATR Vision
(ATR; Pistoia, Italy) motor allows programming for reciprocating movement at four-tenths of a circle CW and
two-tenths of a circle CCW. The F2 file was driven at 400 rpm with a 16:1 reduction ratio contraangle handpiece
Lifespan of One Nickel-Titanium Rotary File with Reciprocating
Motion in Curved Root Canals Sung-Yeop You, DDS, Kwang-Shik Bae, DDS,
PhD, Seung-Ho Baek, DDS, PhD,Kee-Yeon Kum, DDS, PhD, Won-Jun Shon,
DDS, PhD, and WooCheol Lee, DDS, PhD
But : entre autre = to compare the timerequired for its preparation of a curved root canal using both reciprocating
and continuous motion.
Méthode = Each canal was prepared with reciprocating motion until the ProTaper F2 single file (Dentsply
Maillefer, Ballaigues, Switzerland) reached the working length. One file was used until it was fractured.
The access cavities were made with #330 burs, and the working lengths were determined as follows.
A #10 K-file was inserted into the root canal until the tip of the file was flush with the apical foramen.
From that point, 1 mm was subtracted, and that length was defined as the working length of the root
canal. After the working length was determined, a glide path was produced using a #15 K-file.
Reciprocating motion (clockwise 140_ and counterclockwise 45_) using the Tecnika digital motor (ATR,
Pistoia, Italy) until a ProTaper F2 single file (Dentsply Maillefer, Ballaigues, Switzerland) reached the
working length. One F2 file was used until it was fractured or deformed, after which it was replaced
with a new file. All the root canals were prepared by one single operator. The fractured files were
examined under the scanning electron microscope (SEM) (Hitachi S-4700; Hitachi, Tokyo, Japan) at
magnifications of _30; _200; _1,000; _2,000; and
_5,000 for disclosing the fracture mechanism. Another 60 canals from 30 of the extracted maxillary
and mandibular molars were divided randomly into two groups: the continuous rotation motion (CM)
group and the reciprocating motion (RM) group. The canals in the CM group (n = 30) were prepared
using continuous rotation following the sequence of ProTaper S1->SX->S1->S2->F1- >F2, whereas
the canals in the RM group (n = 30) were prepared with reciprocating motion with the sole use of the
ProTaper F2.
The average lifespan of one F2 file was 10.60 _ 4.35 canals with the longest lifespan of 21 canals. The total time
for canal preparation was 46.42 _ 18.12 seconds and 21.15 _ 6.70 seconds in the CM and RM groups,
respectively. There was a statistically significant difference between the groups (p < 0.01).
Within the limitation of this study, one F2 file can be safely used to the working length of curved canals at least six
times under reciprocating motion. Reciprocating preparation with only one F2 file was much faster than root canal
instrumentation with continuous rotation. (J Endod 2010;36:1991–1994) The total root canal preparation time
was measured until the F2 file finally reached the working length, excluding the time it took to
change files and irrigate the canals. The average lifespan of one F2 file was 10.60_4.35 canals. The
longest lifespan of a single F2 file was 21 canals, and the shortest one was 6 canals (Table 1). The
total time for canal preparation in CM group was 46.42 _ 18.12 seconds, and the total time for canal
preparation in RM group was 21.15 _ 6.70 seconds. There was a statistically significant difference
between the two groups (p < 0.01).
O
ne of the goals of endodontic treatment is thorough cleaning and shaping of the root canal system
by removing all the infected pulp tissue, bacteria, and their byproducts (1, 2).
The NiTi rotary file has induced a significant progress in endodontic treatment because of its flexibility
and high cutting efficiency (3–5). With the instrument placed in the center of the root canal, it has
become possible to produce a more rounded and tapered funnel-shaped canal while reducing the
incidence of procedural accidents such as transportation and ledge formation (6, 7). Furthermore, NiTi
files prepare canals easily and rapidly with minimal straightening (8).
Despite these advantages, the biggest problems of NiTi files are their high cost and unexpected
instrument fracture (4, 9). The high cost of NiTi files has forced many clinicians to reuse them, which,
in turn, leads to a higher incidence of instrument fracture. A recent retrospective study (10) showed
that most file fractures occurred in curved root canals, especially in the mandibular molars.
In this regard, the employment of reciprocating motion instead of the conventional continuous rotation
method has been suggested to be advantageous in the preparation of curved canals with the use of
one single NiTi file (14). However, it was a single case report of one operator, and there were no wellcontrolled comparisons
with any existing methods.
Reciprocating motion (clockwise 140_ and counterclockwise 45_) using the Tecnika digital motor (ATR,
Pistoia, Italy) until a ProTaper F2 single file (Dentsply Maillefer, Ballaigues, Switzerland)
When using a series of NiTi files, certain files bear more stress than others. For this reason, it is not
possible to measure the lifespan of a certain file that reaches the full working length with completion of
the root canal preparation. So far, apart from the recommendations to discard the NiTi file when it
undergoes deformation or when the operator becomes instinctively insecure about the state of the file,
there have been no reports on the fracture incidence of certain types of NiTi files.
The data showed that the longest lifespan of single ProTaper F2 files with reciprocating motion was 21
canals with a mean lifespan of 10.60 canals. In this regard, Shen et al (16) reported on the mean
lifespan of ProTaper files from two clinics. To our surprise, the result from one clinic showed that an
average of 16.88 canals were prepared with one set of ProTaper files. However, it should be taken
into consideration that the teeth included in their study were not limited to only molars. The data from
other clinic in their same study revealed that only 2.83 molar cases were safely instrumented with
sequential use of 6 ProTaper files. These results showed dramatic differences between uses in curved
canals and in straight canals as well as the short lifespan of files in curved canals
In this study, the minimum extent of ProTaper F2 usage before fracture was after six canal
preparations, and this result seems to be consistent with Peters et al (17) who suggested that
ProTaper files should be thrown away after being used in four to five constricted canals. According to
another recent study (18), the lifespan of the ProTaper files was found to be 10 canals when they were used in sequence under continuous rotation,
whereas these ProTaper files could be used in up to 13 canals without fracture when reciprocating
motion was employed.
Among the files used in their experiment, F2 files were shown to be reused in up to 10 canals without
fracture under reciprocating motion, and this result was similar to our study in which the mean lifespan
of the ProTaper F2 was 10.60 canals.
When comparing the number of files needed in canal preparation, Varela-Patino et al (18) showed that
a total of 23 ProTaper file series were needed to prepare 60 canals with reciprocating motion, and a
total of 30 ProTaper file series were needed to prepare 60 canals under continuous rotation motion. In
this study, only 11 F2 files were used to prepare 120 canals, and this was a big reduction in the
number of files necessary to instrument to the working length. Furthermore, this is in contrast to one’s
expectations that when using only one master apical size rotary file for the preparation of the entire
root canal system, the stress exerted on this NiTI file should easily fracture it (19). These results can
be explained by two reasons. First, the torsional stress was reduced by using reciprocating motion.
Reciprocating motion prevents the taper lock phenomenon by unsymmetrical repeating of the
clockwise and counterclockwise rotations (14, 18). As a result, it reduces torsional fracture, allowing us
to understand how reciprocating motion shows better results compared with continuous rotation. The
other reason is that the file used in this study was a ProTaper file. ProTaper files are known to resist
torsional fracture by uniformly distributing the stress exerted on it (20). However, further research is
needed to evaluate not only the stress distribution in other types of files under reciprocating motion but
also the cleaning and shaping ability of a single file with reciprocating motion.
Considering the efficiency of reciprocating motion, the total time taken for canal preparation in the RM
group was half of that in the CM group. We noted a drastic reduction in the time needed for the
preparation of curved canals to the working length with only one master apical size file under the
reciprocating motion. This suggests that the reciprocating motion is superior not only in its mean
lifespan but also in its cutting efficiency, which is ultimately expected to reduce the operator’s fatigue.
Considering the efficiency of reciprocating motion, the total time taken for canal preparation in the RM
group was half of that in the CM group. We noted a drastic reduction in the time needed for the
preparation of curved canals to the working length with only one master apical size file under the
reciprocating motion. This suggests that the reciprocating motion is superior not only in its mean
lifespan but also in its cutting efficiency, which is ultimately expected to reduce the operator’s fatigue.
According to a report by Sattapan et al (21), fracture of NiTi files occurs in one of two ways: flexural
and torsional failure. Flexural fracture occurs because of repeated compression and tension in curved
canal. Torsional fracture occurs when binding occurs at a part of the file other than the tip. In the
clinical situation, both torsional stress and cyclic fatigue are exerted on files within the root canal, and
these two forces influence each other. In fact, NiTi files exposed to torsional stress are prone to
fracture at a lower cyclic fatigue (22), and torsional resistance decreases in used files (23). Therefore,
these two aspects of file fracture can be simultaneously observed when the cross-sectional area of the
fractured file was examined under the SEM (24).
The problem in choosing NiTi files that have a high torsional resistance in most cases is that the cyclic
fatigue
value and the torsional resistance value are inversely proportional (4,25). In this regard, Ullmann and
Peters (25) reported that larger instruments that have been subjected to some cyclic fatigue should be
used with great care or discarded. The other method for preventing file fracture is to reduce torsional
stress in the process of canal preparation. For this purpose, preflaring and the crown-down
preparation have been suggested (9). These methods have been known to not only decrease the
occurring torsional stress but also shifts the area on which the stress is exerted on (from the tip to the
body of the file), further reducing any torsional stress.
As it was reported by other studies (14, 18) and reconfirmed in this study, reciprocating motion
reduces torsional stress by preventing binding of the file, thereby raising expectations that files could
be used longer without fracture.
In conclusion, within the limitation of this study, one F2 file can be safely used to the working length of
curved canals at least 6 times under reciprocating motion without any help of other ProTaper files such
as SX, S1, S2, and F1. Reciprocating preparation with only one F2 file was much faster than root
canal instrumentation with continuous rotation.
CLINICAL ARTICLE Canal preparation using only one Ni-Ti rotary
instrument: preliminary observations G. Yared 102-83 Dawson Road,
Guelph, ON N1H 1 B1, Canada
Méthode = In this novel technique, the canal is negotiated to the working length with a size 08 hand file. Then, the
canal preparation is completed with an F2 ProTaper instrument used in a reciprocating movement. In larger canals, the
use of additional hand files may be required to complete the apical enlargement.
The advantages of the technique include a reduced number of instruments, lower cost, a reduced instrument fatigue and
the elimination of possible prion cross-contamination associated with the single use of endodontic instruments.
Effective cleaning and shaping of the root canal system is essential for achieving the biological and mechanical
objectives of root canal treatment. The objectives are to remove all the pulp tissue, bacteria and their by-products whilst
providing adequate canal shape to fill the canal (Schilder 1974).
However, nickel-titanium (Ni-Ti) instruments offer many advantages over conventional files. They are flexible (Walia et
al. 1988), have increased cutting efficiency (Kazemi et al. 1996) and have improved time efficiency (Ferraz et al. 2001).
Furthermore, Ni-Ti instruments maintain the original canal shape during preparation and have a reduced tendency to
transport the apical foramen (Kuhn et al. 1997, Reddy & Hicks 1998, Ferraz et al. 2001, Pettiette et al. 2001).
With all these apparent advantages, the use of Ni-Ti rotary systems has increased considerably since their introduction.
However, their cost and instrument fracture (Alapati et al. 2003, 2004, Berutti et al. 2004) are notable disadvantages.
The clinician is faced with two major concerns when considering the use of Ni-Ti rotary instruments: (i) possibility of
instrument fracture associated with increased instrument fatigue caused by the repeated use and (ii) the possibility of
cross-contamination associated with the inability to adequately clean and sterilize endodontic instruments (Spongiform
Encephalopathy Advisory Committee 2006). A recent study found prions in human pulp tissue (Schneider et al. 2007).
Tooth structure and organic debris were observed on the surface of Ni-Ti rotary instruments, and appeared to adhere in
the surface cracks despite meticulous ultrasonic cleaning and decontamination (Alapati et al. 2003, 2004, Sonntag &
Peters 2007). Therefore, the single use of endodontic instruments was recommended to reduce instrument fatigue and
possible cross-contamination. However, the single use of endodontic instruments and, mainly the more expensive Ni-Ti
rotary instruments, may become an economical burden on the endodontist and the general dentist especially as the
available techniques involve the use of at least three to four Ni-Ti rotary instruments. Consequently, the introduction of
canal preparation techniques which would reduce the number of instruments required to achieve the mechanical and
biological objectives would be beneficial.
This novel technique will reduce the number of Ni-Ti rotary instruments required for canal preparation, simplify the
armamentarium and would be more cost-effective compared with other Ni-Ti rotary techniques with regards to the single
use of Ni-Ti rotary instruments.
F2 ProTaper Ni-Ti rotary instrument (Tulsa Dentsply, Tulsa, OK, USA).
Instrumentation F2
An F2 ProTaper Ni-Ti rotary instrument is used for the canal preparation in a clockwise
(CW) and counterclockwise (CCW) movement. The F2 is used in conjunction with a 16 : 1
reduction ratio contra-angle connected to an ATR Vision (ATR, Pistoia, Italy) motor which
allows the reciprocating movement. The CW and the CCW rotations are set on the motor
at four-tenth and two-tenth of a circle. The rotational speed is set at 400 rpm.
The F2 instrument is used in the canal with a slow pecking motion and an extremely light apical pressure until resistance
is encountered (i.e. until more pressure is needed to make the F2 advance further in the canal). The instrument is then
pulled out of the canal, cleaned with a gauze to remove the debris filling the flutes, and reinserted and employed in the
same manner. This step is repeated until the F2 reaches the working length. No further enlargement would be required
for narrow and/or curved canals. For larger canals, hand files can be used after the F2 reaches the working length to
complete the apical enlargement. The canal preparation is accomplished with continuous canal irrigation using a 2.5%
solution of sodium hypochlorite and a final rinse with EDTA 17% followed by NaOCl.
Voir la suite de la préparation dans ‘larticle
Theoretically, the CW and CCW movement would reduce the incidence of torsional fracture by taper-lock. However, this
issue needs to be investigated.
One other important aspect of the F2 instrument is the variable taper. This feature would provide an increased flexibility
for this larger instrument which can be used in this technique to prepare severely curved canals (Figs 1–3). An
instrument with a fixed 0.08 mm mm)1 taper would be too rigid to be used in curved canals.
The degrees of CW and CCW rotations were determined from the torsional fatigue profile of the F2 ProTaper instrument
(unpublished results; Thompson 2006). These values were less than the degree of rotation at which the F2 instrument
would fracture if bound in dentine (Thompson 2006).
The CW rotation was greater than the CCW rotation. When the instrument is rotated CW, it will screw in the canal. When
rotated CCW, the instrument will unscrew out of the canal. As the CW rotation is greater than the CCW rotation, the end
result is a screwing in effect and an advancement of the instrument in the canal. Consequently, only very light apical
pressure should be applied on the instrument as its advancement would be almost automatic
At the present time, the ATR Vision motor (ATR, Pistoia, Italy) was the only one
available in North America to allow the setting of the specific values of the CW and CCW
rotations.
In the standard Ni-Ti techniques using continuous rotation, it is crucial to enlarge the canal to at least a size 15 file prior
to the use of rotary instruments (Peters et al. 2003, Berutti et al. 2004, Patino et al. 2005). If not, although the instrument
would still advance in the canal, it would bind in dentine; instrument fracture may then occur due to taper-lock. In the
present technique, the size 08 hand file ensures the presence of a patent glide path. The impression was that further
enlargement with hand files may not be necessary even for the preparation of severely curved canals and
Several authors (Stabholz et al. 1995, Ibarrola et al. 1999) recommended preflaring of the canal prior to its negotiation
with hand files to the working length to minimize the incidence of procedural errors. In the present technique, the canal
can be negotiated passively to resistance with a hand file size 8, and then the F2 is used to enlarge the canal
to the length reached by the hand file. This step would be repeated until the hand file and the F2 reach the working
length. Similar to the standard Ni-Ti rotary instrumentation techniques, one limitation for the application of the present
technique is the presence of a sharp (non-gradual) canal curvature. In such a case, the instrumentation with the F2
would be carried to a level coronal to the curvature; the preparation of the apical part would then be completed with hand
files.
A novel canal preparation technique with only one Ni-Ti rotary instrument used in a clockwise and counterclockwise
movement is described. This technique would offer two major advantages: (i) the single use of endodontic instruments
would become more costeffective and (ii) the elimination of possible prion cross-contamination and a reduced instrument
fatigue associated with the single use of endodontic hand and rotary reamers and files.
Root Canal Preparation of Maxillary Molars With the Self-adjusting
File: A Micro-computed Tomography Study Ove A. Peters, DMD, MS,
PhD,* and Frank Paque´, Dr med dent†
Introduction: The aim of this study was to describe the canal shaping properties of a novel nickel-titanium
instrument, the self-adjusting file (SAF), in maxillary molars.
Canals were shaped with the SAF, which was operated with continuous irrigation in a handpiece that provided an
in-and-out vibrating movement. Changes in canal volumes, surface areas, and crosssectional geometry were
compared with preoperative values. Canal transportation and the fraction of unprepared canal surface area were
also determined.
Results: Preoperatively, mean canal volumes were 2.88 _ 1.32, 1.50 _ 0.99, and 4.30 _ 1.89 mm3 for mesiobuccal
(MB), distobuccal (DB), and palatal (P) canals, respectively; these values were statistically similar to earlier
studies with the same protocol.
Volumes and surface areas increased significantly in MB, DB, and P canals; mean canal transportation scores in
the apical and middle root canal thirds ranged between 31 and 89 mm. Mean unprepared surfaces were 25.8% _
12.4%, 22.1% _12.0%, and 25.2% _ 11.3% in MB, DB, and P canals, respectively (P > .05) when assessed at
high resolution.
Conclusions: By using SAF instruments in vitro, canals in maxillary molars were homogenously and
circumferentially prepared with little canal transportation. (J Endod
2011;37:53–57)
Cleaning and shaping of root canals successfully require the presence of irrigation solutions that can
only be applied to the apical root canal third after enlargement with instruments (1–4). Nickeltitanium (NiTi) rotary instruments have become an important adjunct for root canal shaping, and
outcomes with these instruments are fairly predictable (5). However, rotary instruments perform
comparably poorly in long-oval canals such as distal canals in lower molars, specifically because they
do not mechanically prepare 60% or more canal surface under these conditions (6). Very recently a
new concept, the so-called self-adjusting file (SAF), has emerged that might allow uniform dentin
removal along the perimeter of oval canals. Root canal preparation with this file has been
quantitatively described only in anterior teeth (7) but not in molar root canals.
The effects of root canal shaping were assessed, besides other approaches, from double-exposure
radiographs (8), from cross sections by using the Bramante technique (9), and more recently by using
micro–computed tomography (MCT) data (10). The latter technique allows nondestructive
quantitative analyses of variables
such as volume, surface areas, cross-sectional shape, taper, and the fraction of affected
surface (11).
Earlier studies had indicated that differences in canal anatomy between palatal (P), mesiobuccal (MB),
and distobuccal (DB) canals would play a significant role for shaping outcomes (12). More ribbonshaped or flat canals such as the MB canal would have more unprepared canal area; moreover, on
average, smaller more curved MB canals would have greater canal transportation than P canals.
On the basis of the fact that the SAF is capable of addressing non-round canal cross sections, we
hypothesized that various canals in maxillary molars can be prepared to similar outcomes with respect
to canal transportation and amount of prepared surface.
Studies based on MCT done in our laboratory during the last decade provided data on preparation
effects for hand and rotary instruments in maxillary molars (10, 12–14). Therefore, the aim of this
study was to describe the canal shaping properties of the SAF in maxillary molars.
From teeth that had been extracted for reasons unrelated to the current study, 20 human maxillary
molars were collected and stored in 0.1% thymol solution at 4_C until further use. Teeth had
mature apices and were free of fractures and artificial alterations.
They were mounted on scanning electron microscopy stubs and then scanned in a desktop MCT unit
at an isotropic resolution of 20 mm(mCT 40; Scanco Medical, Bru¨ ttisellen, Switzerland) by using
previously established methods (10, 15). Care was taken to specifically select teeth that did not have a
distinct fourth canal orifice so as to include a buccolingually flat mesiobuccal canal, as judged from a
preoperative MCT scan in low resolution. Teeth were then accessed by using high-speed diamond
burs, and patency of the coronal canal was confirmed. Coronal flaring was accomplished with #2
Gates Glidden burs (Dentsply Maillefer, Ballaigues, Switzerland) placed to 2–3 mm below the
cemento-enamel junction. Subsequently, canal lengths and patency were determined with size 10 Kfiles (Dentsply Maillefer) and radiographs; working lengths (WLs) were set 1 mm shorter than the
radiographic apex. Each canal was then probed with #20 K-file. If it reached the WL, no further
preparation was done. If the canal was narrower than that, it was prepared until #20 K-file could freely
reach the WL to provide a glide path.
A special irrigation device (VATEA; ReDent Nova) was connected to the irrigation hub on the file and
provided flow of the irrigant (3% NaOCl) at a flow rate of 5 mL/min.
Mean initial canal volumes in the apical 4 mm were 0.69, 0.31, and 0.91 mm 3 in MB, DB, and P canals,
respectively (P < .01). Canal cross sections were rounder in DB and P canals compared with MB
canals (P < .01, Table 1). Both preoperative volumes and SMI scores were statistically similar
compared with samples of maxillary molars used in earlier studies (10, 12–14). Overall, canal
preparation of root canals in maxillary molars with the SAF resulted in adequate canal shapes with no
major shaping errors. In particular, no SAF fractured during the course of the study. On the basis of
superimposed red-green coded surface areas (Fig. 1A), overall shapes were satisfactory, with similar
amounts of dentin removed around the perimeter in most cross sections (Fig. 1A) and overall fully
prepared canal surface areas. Preparing with the SAF for 4 minutes resulted in mean dentin removal
ranging from 2.00–2.87 mm3; this represented significant volume changes compared with preoperative
data (P < .01). Differences in volume increase were small but significantly different when comparing
the 3 canal types investigated (Table 1). Increases in SMI were only significant for MB canals; 8 of
60 canals had SMI increases of 1 or more, all of which were MB canals. Slice-by-slice observation
indicated that rounding of MB canals occurred mostly in the coronal third. Mechanically untreated
canal areas, calculated by using superimposed MCT data sets (Fig. 1), were 25.8% _ 12.4%, 22.1% _
12.0%,and 25.2% _ 11.3% for MB, DB, and P canals, respectively (Table 2); untreated canal
areas were not statistically different when comparing the 3 canal types (P > .05). When restricted
to the apical 4 mm, uninstrumented canal areas ranged from 28.8% in DB canals to 47.4% in P
canals. When canal models were reformatted to 34-mm resolution, overall uninstrumented
areas were 38.5% (Table 2). Mean canal transportation ranged from 31–149 mm and was larger
in the coronal third compared with the apical and middle canal thirds (P < .01, Table 3). Canal
transportation was lowest in the palatal canal. Differences between all canal types with respect
to canal transportation at the middle and apical levels were significant; however, the individual
canal transportation values exceeded 100 mm only in 15 of 120 cases at those 2 levels. No
differences were registered when surface areas or canal transportation were recalculated on the basis
of 34 mm compared with 20 mm.
Dentin removal with the SAF is most effective during the first 2 minutes of use (18). However,
additional time might be needed to ensure a full canal wall preparation in some cases; for example, 4
and possibly 5 minutes of activation were required in anterior teeth (7). Preparation with the SAF did
not result in obvious preparation errors such as perforation and ledging, with canal transportation
values typically below 100 mm for the middle and apical canal sections. The slightly larger canal
transportation in the coronal section, particularly in MB canals, could have been possibly caused by
Gates Glidden drills in an attempt to facilitate straight-line access.
Overall, canal transportation is likely a cumulated effect of coronal flaring, glide path preparation, and
the action of the SAF. Similarly, adding instruments for further apical enlargement tends to increase
canal transportation, as shown in an MCT-based pilot study with sequential scanning (19). An earlier
study with the same experimental setup had shown overall canal transportation scores of 123.7, 89.8,
and 97.7 mm for the
coronal, middle, and apical thirds, respectively, after preparation with NiTi rotary instruments or K-files
(10). These scores and also those described for MB, DB, and P canals shaped with ProTaper (12) and
FlexMaster (13) indicate larger canal transportation for rotary instruments than for the SAF in maxillary
molar canals.
In fact, our earlier study on the effect of SAF preparation on maxillary incisors (7) indicated that 5
minutes of shaping with the 2.0-mm SAF resulted in 91.4% treated surface, but only 56.6% surface
had more than 100 mm dentin shaved off.
The present study, on the basis of 20-mmresolution, demonstrates overall unaffected canal area of
25.2%. However, a recalculation to 34- mm resolution results in overall 38.5% unaffected area
study on canals prepared to apical sizes #40 (MB, DB) and #45 (P) (10) indicated similar amounts of
overall unprepared surface as in the present study (38.1%). However, rotary preparation of flat MB
canals in maxillary molars in earlier studies (12, 13) resulted in 43.0% and 47.4% mean unaffected
areas, respectively, which is
higher than the scores in the present study.
Taken together, cross sections from various slices (Fig. 1) and low scores for unaffected canal
surface, in particular for flat canals, suggest that canal preparation with the SAF does indeed result in
homogenous preparation and circumferential removal of a layer of hard tissue.
In the present study, there were no significant differences in respect to affected canal surface among
the canal types. Nevertheless, when the same SAF size is used (eg, 1.5 mm) for multiple canals in the
same tooth, it might be prudent to increase preparation time for larger canal diameters. This will
compensate for lesser forces of the cutting SAF elements against canal walls (18) in larger canals
such as the palatal or the distal canal in molars. Alternatively, it might be advisable to instrument large
canals before any smaller canals, on the basis of the tactile feedback during confirmation of the glide
path. Rotary NiTi root canal files have been linked to 3%–5% incidence of intracanal breakage (23);
although a retained instrument fragment per se might not significantly alter healing outcomes of
periapical lesions, it is preferable to have no impediment to disinfection inside canals. In the present
study we did not observe any SAF breakage with retained fragments
Eradication of microorganisms, a critical step for endodontic outcomes (24), is the result of a
combination of mechanical preparation (25) and irrigation (26). Irrigation alone is not always effective
(27), and mechanical action of instruments on canal walls, including removal of infected dentin, might
be needed. The preparation of the most apical canal section remains a challenge.
In the present study, mechanical preparation with the SAF resulted in limited prepared surface. Hence,
sufficient deposition of disinfecting irrigation solutions remains important. Antibacterial efficacy of canal
surface preparation was not directly determined in the present study. Mechanical preparation per se
might affect bacterial biofilms (28) rather than only microorganisms in their planktonic state.
In fact, a recent scanning electron microscopic study suggested that preparation with the SAF leaves
very clean dentin walls, probably as a result of concurrent irrigation possible with this system (6).
the SAF and in particular its potential to debride canal walls better will lead to improved clinical
outcomes, but clinical studies are underway to address this question. Another important clinical
question is how best to obturate canals prepared with the SAF; initial data (29) suggest that lateral
compaction resulted in better obturation quality after SAF preparation compared with rotary
instrumentation. In conclusion, by using SAF instruments in vitro, canals in maxillary molars were
homogenously and circumferentially prepared with little canal transportation or other procedural errors.
Single-file F2 Protaper Technique in Oval-shaped Canals Gustavo DeDeus, DDS, MS, PhD,* Bianca Barino, DDS, MS,* Renata Quintella
Zamolyi, MD, MS,† Erick Souza, DDS, MS, PhD,‡ Albino Fonseca, Ju´nior,
MD, MS, Sandra Fidel, DDS, MS, PhD,§ and Rivail Antonio Sergio Fidel,
DDS, MS, PhD§
Introduction: The aim of this study was to determine whether the debridement quality of the singlefile F2 Pro-Taper instrumentation technique is comparable to a full conventional ProTaper sequence
in both round and oval-shaped root canals.
The single-file F2 ProTaper technique displayed similar PRPT to the full range of ProTaper
instruments in round canals. However, the debridement quality of the single-file F2 ProTaper
technique was suboptimal in oval canals.
Proper cleaning and shaping of the whole root canal space have been recognized as a real challenge,
particularly in curved, narrow, or oval-shaped canals (1–6). By using the reliable micro-tomography
method, Peters et al (6) reported that nickeltitanium (NiTi) instruments left about 35% of untouched
root dentin surfaces. This deficient mechanical preparation could offer an opportunity for remaining
microorganisms to recolonize the filled canal space, resulting in endodontic failure. In 2008, a new
preparation technique using only the F2 ProTaper instrument in a reciprocating movement was
published (7). The concept of using a single NiTi instrument to prepare the entire root canal is
interesting, because the learning curve is considerably reduced as a result of technique
simplification. Moreover, the use of a single NiTi instrument is more cost-effective than the
conventional multi-file NiTi rotary systems.
Although the first clinical impressions of the single-file F2 ProTaper technique appear promising (7),
other important parameters still need to be properly assessed by both laboratory and clinical studies.
Root canal debridement, for instance, is considered an important goal to be achieved after mechanical
instrumentation of the root canal and is frequently measured in terms of cleaning efficacy (2–5, 8).
In fact, the technique proposed by Yared (7) has never been assessed in terms of debridement
quality. In the present study, we sought to evaluate the amount of residual pulp tissue after the use of
either the full range of ProTaper instruments or the single-file F2 Pro-Taper technique in both round
and oval canals.
Two null hypotheses were tested: (1) there is no significant difference in debridement quality promoted
by conventional full sequence of the ProTaper Universal NiTi files and the single-file F2 ProTaper
technique in circular-shaped canals; (2) there is no significant difference in debridement quality
promoted by conventional full sequence of the ProTaper Universal NiTi files and the single-file F2
ProTaper technique in oval-shaped canals
With the purpose of collecting just vital mandibular incisor teeth,
After each extraction, teeth were immediately placed into a vial containing 10 mL of buffered 10%
formalin labelled with a random 4-digit alphanumeric code corresponding to 1 of the 4 experimental
groups.
For 6 months (August 2009–January 2010) following the abovementioned selection process, 98
mandibular incisor teeth were collected. Radiographs were taken in buccolingual and mesiodistal
directions to select only teeth with a single root canal as well as to categorize them as oval or circularshaped canals. The space corresponding to the root canal lumen was measured 5 mm from the apex;
when the mesiodistal diameter was 2.5 times larger than the buccolingual diameter, the canals were
classified as oval-shaped; for round-shaped
canals, the mesiodistal diameter had to be similar to the buccolingual diameter. All teeth presenting
isthmus, lateral, or 2 canals had been eliminated. Furthermore, only root canals with an initial apical
size equivalent to size 10 K-file were selected. As a result, just 54 incisor teeth fit the selection criteria.
From the selected sample, 24 teeth were classified as circular-shaped and 24 as oval-shaped root
canals. The 6 remaining teeth were used as histologic controls.
A common silicone impression material was used to simulate the bony socket site. Tooth
length was standardized to 18 mm, and the root canal patency was confirmed by inserting a
size 10 instrument. The working length was established at the apical foramen. The use of
different instrumentation techniques in both ovalshaped and circular-shaped root canals resulted in 4
experimental groups with 12 specimens each. Teeth for both experimental and control groups were
randomly assigned with the aid of a computer algorithm
(http://www.random.org).
For both groups, 1 mL of 5.25% NaOCl solution was used between each instrument. To standardize
the final irrigation volume used in the experimental groups, the volume of NaOCl was changed
according to the number of instruments used in each technique. Thus, a total volume of 18 mL of
NaOCl per treatment was used. The smear layer was removed with 3 mL of 17%
ethylenediaminetetraacetic acid for 3 minutes. Three milliliters of bi-distilled water was used for 3
minutes as a final flush. Twenty-four teeth (12 circular-shaped and 12 oval-shaped canals) were
prepared with the ProTaper Universal instruments (Dentsply Maillefer, Ballaigues, Switzerland) driven
at 300 rpm and 2 N/cm of torque (XSmart; Dentsply-Maillefer) under rotary motion (group 1). The
sequence was the following: (1) S1 file (1/3 of the working length [WL]); (2) SX file (1/2 of the WL); (3)
S2 file (2/3 of the WL); and (4) F1 and (5) F2 files (full WL). Therefore, all the canals in this group were
instrumented with 5 NiTi instruments. The other 24 teeth (12 circular-shaped and 12 oval-shaped
canals) were prepared by the single-file F2 ProTaper technique (7); rotational speed was set at 400
rpm, and the F2 instrument was driven with ATR Teknica electric micromotor (Pistoia, Tuscany, Italy)
under reciprocating movement (group 2).
The specimens were visualized in Axioplan 2 Imaging fully motorized light microscope (Carl Zeiss
Vision, Hallbergmoos, Germany). Image analysis and processing were completed by using the Axion
Vision image 4.5 Zeiss system (Zeiss) to trace the outline of the area of interest. In this way, the crosssectional areas of each root canal and remaining pulp tissue were measured (mm2). Furthermore, the
percentages of remaining pulp tissue area (PRPT) were calculated for each root canal section.
Univariate analysis of variance demonstrated that both root canal shape and instrumentation
technique significantly influenced the PRPT (P < .05). Much more tissue was removed in round canals
than in oval ones in both techniques (P < .05). The shape of the canal significantly influenced the
result of the technique, which can be seen by the significance in the interaction between canal shape
and technique (P < .05). Group 1 removed significantly more pulp tissue than group 2 in oval canals (P
< .05), whereas there was no difference between techniques in round canals (P > .05). The level of
cross section did not influence the PRPT (P = .325). The descriptive data are displayed in Table 1.
The present results show no differences in the debridement quality of circular-shaped canals prepared
by the conventional full sequence of ProTaper Universal NiTi files and the single-file F2 ProTaper
technique.
Therefore, the first null hypothesis was accepted. On the other hand, the oval-shaped canals prepared
by conventional ProTaper full sequence displayed significant improvement in debridement quality than
those prepared with the single-file F2 ProTaper technique. Thus, the second null hypothesis tested
was rejected.
Recently, Taha et al (1) reported that the wide variation among different teeth prepared by the same
technique appears to result from variations in root canal anatomy rather than from the instrument or
technique itself. The results of the present study support this statement because the shape of the root
canal significantly influenced the debridement quality. Thus, the complex anatomy of the root canal
space must be restated as the critical challenge in infection control, especially considering the welldemonstrated limitations of the current root canal preparation techniques.
The suboptimal results achieved by oval-shaped canals prepared by the single-file F2 ProTaper
technique might have a 2-fold basis: (1) the reduced number of files and (2) the reciprocating
movement kinetics. Because these 2 variables were present in this study, it is not possible to
determine the influence of each one on the final result. Probably both variables are combining to result
in the suboptimal performance by the single-file F2 ProTaper technique in oval canals.
Infact, an additional appropriate experimental design is required to isolate the influence of the
reciprocating movement on the debridement quality as well as the influence of the reduced number of
instruments.
The reduction in the number of instruments is a clear attempt to decrease the learning curve, also
resulting in a cost-effective approach. However, the poorest debridement quality in oval-shaped canals
can be considered as a side effect provoked by the simplistic approach of the single-file F2 ProTaper
technique.
The debridement quality of the root canal space has been reported to be more dependent on chemical
than mechanical preparation once an adequate taper is obtained (9). However, single-file F2 ProTaper
technique displayed significantly lower debridement ability in the present study, even with teeth
presenting a similar taper preparation. This re-stresses the fact that even though the root canal space
is radiographically properly enlarged, suitable debridement is not guaranteed.
The poor debridement quality in oval-shaped canals reported here is not a novelty. In effect, ovalshaped canals have been representing a real challenge to clean, shape, and fill (9–12). By using the
reliable micro–computed tomography method, Paque´ et al (12) observed more than half of
unprepared dentinal walls (ranging from 59.6%–79.9%), regardless of the instrumentation technique
used in oval-shaped root canals. The poor debridement quality found in the present study can be
correlated to findings reported by Paque´ et al. The cross section images of the present study restate
that rotary NiTi instruments tend to create round preparations in oval-shaped canals, leaving
unprepared lingual and buccal extensions with remaining pulp tissue and the untouched dentin inner
layer (1, 12) (Fig. 1B– F). This indicates that rotary NiTi systems are currently unable to produce
optimal preparation of oval-shaped canals as a result of the large difference between instrument
design and root canal geometry.
In this context, entirely groundbreaking approaches for root canal instrumentation are required to
optimize the debridement quality of oval-shaped canals. Therefore, innovative instruments such as the
recently introduced self-adjusting file system (13–15) deserve indepth investigations.
Remaining pulp tissue is the outcome measure used in the present experimental model to
compare the cleaning efficacy of different shaping methods.
The prospective in vivo selection of vital teeth by using a meticulous and well-controlled approach for
diagnosing pulp vitality enabled effective standard of control for selecting teeth with tissue contents
(16); which was confirmed by the positive histologic controls. This is an essential methodological step
to assure the credibility for a comparative study with histologic assessment (16, 17).
In summary, the present study demonstrated the influence of the root canal shape on the debridement
quality, regardless of the preparation technique used. Single-file F2 ProTaper technique displayed the
poorer debridement quality in oval-shaped canals. The present results lay emphasis on the
debridement limitations of the current chemical-mechanical preparation methods as well as on the
needed pursuit for more efficient instrumentation protocols.
Root Canal Anatomy Preservation of WaveOne Reciprocating Files
with or without Glide Pat Elio Berutti, MD, DDS,* Davide Salvatore Paolino,
MS, PhD,† Giorgio Chiandussi, MS, PhD, Mario Alovisi, DDS,* Giuseppe
Cantatore, MD, DDS,‡ Arnaldo Castellucci, MD, DDS, and Damiano Pasqualini,
DDS*
Introduction: This study evaluated the influence of glide path on canal curvature and axis modification after
instrumentation with WaveOne Primary reciprocating files.
Canal modifications seem to be significantly reduced when previous glide path is performed by using the new
WaveOne nickel-titanium single-file system.
N
ickel-titanium (NiTi) rotary instruments were introduced to improve root canal preparation (1). In
clinical practice these instruments are associated with an increased risk of fracture, mainly because of
bending normal stresses (failure by fatigue) and torsional shear stresses (failure by torque) (2–4).
Failure by torque might occur in case of torsional shear stresses exceeding the elastic limit of the
alloy, producing plastic deformation and eventually fracture (4). The clinician and the type of
instrumentation are fundamental to prevent torsional shear stresses. Various aspects might contribute
to increase these stresses, such as excessive pressure on the handpiece (5), a wide area of contact
between the canal walls and the cutting edge of the instrument (6, 7), or if the canal section is smaller
than the dimension of the nonactive or noncutting tip of the instrument (6, 7); the latter case might lead
to a taper lock, especially with regularly tapered instruments (8). The risk of taper lock might be
reduced by performing coronal enlargement (9, 10) and creating a glide path before using NiTi rotary
instrumentation (11, 12), both manual and mechanical (13). Thus, the root canal diameter should be
bigger than or at least the same size as the tip of the first rotary instrument used (11–13). Canal
curvature is considered one of the major risk factors for instrument failure caused by bending cyclic
fatigue (1); stresses due to bending cannot be significantly influenced by the clinician
No macroscopic deformations or fractures of any instrument occurred during the experiment.
The new WaveOne NiTi primary reciprocating file, if used after a previous glide path, produced less
modification in canal curvature compared with the Wave- One alone, as actually suggested by the
clinical procedure flowchart (17). WaveOne NiTi files appear to maintain the original canal anatomy,
and the presence of a glide path of the canal further improves their performance.
Coronal enlargement (9) and preliminary creation of a glide path are fundamental for safer use of NiTi
rotary instrumentation (11, 12). Furthermore, the preflaring of root canals would increase the accuracy
of root canal length measurements with electronic apex locators (20).
Reciprocating motion was proposed to increase canal centering ability as well as to reduce the risk of
root canal deformity (21–23)
the new M-Wire variant NiTi alloy instruments demonstrated better resistance on cyclic fatigue when
compared with the same instrument design produced from stock 508 nitinol, preserving similar
torsional properties (16).
Canal scouting and preflaring are the first phases of canal instrumentation during which the clinician
might more frequently find procedural difficulties (25). The use of a small-size hand K-file followed by a
more flexible and less tapered NiTi rotary PathFile might be a less invasive and safer method to
provide a glide path that better maintains the original canal anatomy, compared with manual preflaring
performed with stainless steel K-file (13). Moreover, preflaring tends to minimize procedural errors
such as transportation and ledge formation. Indeed, preflaring permits to maintain a pathway to the
fullWL, avoiding excessive instrument binding in the canal (11, 12).
In this study, it was observed that fewer pecking motions were needed to reach full WL with
WaveOne single files, when previously glide path was performed. It might be hypothesized that this
could reduce the risk of excessive undesired instrument brushing on the canal walls and subsequent
root canal transportation (26–28).
Furthermore, canal aberrations might lead to inadequate shaping and filling, affecting negatively the
disinfection and the long-termprognosis of the root canal therapy (1, 29). Outer apical transportation
and irregular foramen widening might lead to poor sealing efficiency with a high rate of extrusion of
debris and postoperative discomfort (30–32). In this study the absence of a previous glide path
affected the performance of WaveOne NiTi files, which evidenced greater alteration of the canal
curvature, compared with the performance of WaveOne files with previous glide path.
Effect of Canal Length and Curvature on Working Length Alteration
with WaveOne Reciprocating Files Elio Berutti, MD, DDS,* Giorgio
Chiandussi, MS, PhD,† Davide Salvatore Paolino, MS, PhD,† Nicola Scotti, DDS,*
Giuseppe Cantatore, MD,‡ Arnaldo Castellucci, MD, DDS,§ and Damiano
Pasqualini, DDS*
This study evaluated the working length (WL) modification after instrumentation with WaveOne Primary (Dentsply
Maillefer, Ballaigues, Switzerland) reciprocating files and the incidence of overinstrumentation in relation to the
initial WL.
A significant decrease in the canal length after instrumentation (95% confidence interval ranging from _0.34 mm
to _0.26 mm) was detected.
Conclusions: Checking the WL before preparation of the apical third of the root canal is recommended when
using the new WaveOne NiTi single-file system.
It has been shown that root canal instrumentation leads to changes in working length (WL) by
straightening of the canal during the course of the treatment (17, 18). Although NiTi rotary
instrumentation may lead to a smaller WL change during shaping procedures (19) compared with
stainless-steel instrumentation, the appropriate determination of WL throughout the entire treatment is
still a key factor for successful endodontic therapy. Davies et al (18) suggested that verifying the WL
after early coronal flaring and late coronal flaring before definitive instrumentation of the apical
segment of the root is the most appropriate action
The present study evidenced that a significant decrease in the WL may occur after instrumentation
with the new reciprocating single file WaveOne Primary, mainly because of the straightening of the
root canal curves. These results are in agreement with the findings of other investigations on WL
reduction after root canal shaping with stainless-steel hand files (21), stainless-steel hand files plus
Gates Glidden burs (18), and NiTi rotary instruments (18, 22). However, it has been shown that NiTi
rotary instrumentation may lead to a considerable, yet smaller, amount of curve straightening and to a
WL decrease (18, 22). This is probably caused by the superior ability of NiTi instrumentation to remain
centered into the root canal compared with stainless steel instrumentation (1, 18, 23). Modifications of
the WL during instrumentation are influenced by several important factors. The original canal anatomy
(ie, the canal curvature [17]) and the coronal flaring of root canals (24) were found to be the primary
determining factors. In this study, the canal length and the canal curvature were correlated to the WL
decrease. As expected, the interaction of both factors as well as the canal curvature by itself
significantly influenced WL reduction; a severe curvature is more likely to lead to a higher decrease in
the WL. On the contrary, straight canals, such as the ones used in the control group, did not undergo
significant WL modifications after instrumentation. In case of severe curvature, flaring the coronal
portion of the root canal should be the procedure of choice in order to facilitate the placement of files
into the apical segment (24) and prevent excessive flexural stress to the Ni-Ti instruments (25, 26). It
has been shown that, in case of severe curvature, the coronal flaring always leads to a WL decrease
independently from the root canal preparation technique (27). However, WL reduction is higher after
immediate coronal flaring compared with late coronal flaring before apical preparation (18). NiTi rotary
files showed a mean WL decrease of_0.22 mmafter canal preparation, but a less pronounced WL
reduction (_0.14 mm) was evident after late canal flaring. Therefore, it is highly recommended to
check the WL at least twice during root canal shaping; an initial check is suggested during canal
scouting. Canal scouting is usually performed with #10 K-file when the patency of the root canal is
explored. Afterwards, a glide path is created, either manual or mechanical (11–13), to prevent NiTi
rotary file tip blockage. A second check of the WL is suggested after canal flaring, before preparation
of the apical portion of the root canal, because the WL is expected to undergo significant changes.
This recommendation is particularly important when using the new WaveOne single-file reciprocating
system, which is designed to reach complete shaping with only 1 instrument used to the full WL. In this
study, the decrease of the canal length after instrumentation ranged from _0.34 mm to _0.26 mm
(95% confidence interval). Furthermore, 24 of 32 WaveOne Primary files projected beyond the
experimental apical foramen. The large incidence (75%) of overinstrumentation was simply caused by
the fact that instrumentation was accomplished only according to the initial WL. Overinstrumentation
with NiTi rotary files of augmented taper beyond the apical foramen may lead to apical transportation
(28) and overfilling (29) with defective apical seal control, especially in severely curved canals. This
type of intraoperative complication is a significant predictor of outcome of the initial endodontic
treatment, especially in teeth with preoperative radiolucency (30). Furthermore, overinstrumentation
may also cause complications such as a greater incidence of postoperative pain (31). The findings of
this study confirm the importance of checking the WL when canal preparation has reached the limit
between medium and apical third of the root canal before instrumentation of the apical third.
Radiographic estimates have been shown to be inaccurate in determining the correct WL in many
clinical situations, probably because of anatomic variability, and to be associated with the tendency to
underestimation (32). Electronic apex locators showed to be precise and reliable in more than 90% of
cases (33) and are superior in reducing overestimation of the root canal length (34). Their accuracy is
improved by the flaring of the canal before WL determination (35). In conclusion, within the limits of
this study, checking the WL before preparation of the apical third of the root canal is a highly
recommended strategy when the new WaveOne NiTi single-file system is used.
Cyclic fatigue of Reciproc and WaveOne reciprocating
instruments G. Plotino, N. M. Grande, L. Testarelli & G. Gambarini Department of
Endodontics, ‘Sapienza’ University of Rome, Rome, Italy
To evaluate the cyclic fatigue resistance of Reciproc_ and WaveOne_ instruments in simulated root canals.
Reciproc_ instruments were associated with a significantly higher cyclic fatigue resistance than WaveOne _ instruments.
Reciproc_ and WaveOne_ instruments have been designed specifically for use in reciprocation. Both instruments have a lefthanded angulation of the blades, which means they cut in the counterclockwise (CCW) direction. The values of clockwise
(CW) and CCW rotations are different. A large rotating angle in the cutting direction (CCW) determines the instrument
advances in the canal and engages dentine to cut it, whereas a smaller angle in the opposite direction (CW) allows the file to
be immediately disengaged and safely progress along the canal path, whilst reducing the effect of a screwing effect and file
breakage. These angles are specific for the different instruments and they were determined using the torsional properties of
the instruments.
The instruments have the same nominal size, tip size 25 with 0.08 taper. Taper is constant in the apical 3 mm of the
instruments but reduces in the middle and coronal portion of the working part of the instrument.
2006). The influence of the cross-sectional design of a NiTi instrument on its cyclic fatigue resistance is controversial and has
been the subject of a number of recent investigations (Turpin et al. 2001, Biz & Figueiredo
2004, Diemer & Calas 2004, Chow et al. 2005). However, how and why the design of the instrument could influence their
behaviour under cyclic fatigue stress remains unclear. In fact, some studies found that the fatigue life of various instruments
did not seem to be affected by the instrument design, suggesting that the cross-sectional area or shape of the instrument is not
the main determinant of fatigue life (Melo et al. 2002, Cheung & Darvell 2007). Yet, other studies on cyclic fatigue
suggested that a different cross-sectional design appeared to be an important determinant of cyclic fatigue resistance of
different files (Haikel et al. 1999, Grande et al. 2006, Tripi et al. 2006, Ray et al. 2007). However, in a previous study,
Grande et al. (2006) demonstrated that the metal mass at the point of maximum stress influenced the lifespan of NiTi rotary
instruments during a cyclic fatigue test. The authors compared the cyclic fatigue resistance of Mtwo_ instruments, with a
lower cross-sectional metal mass, and ProTaper_ instruments, with a larger crosssectional metal mass, and reported that the
bigger the metal mass, the lower the fatigue resistance. These results are consistent with those of the present study, which
showed that Reciproc_ instruments, with a design similar to Mtwo_, are more resistant than WaveOne_ which has a cross
sectional design similar to ProTaper_. It must be exp
however, single use means that the same instrument can be used in 3–4 root canals, which could be complex and tortuous.
Therefore, single use reduces but not eliminates the risk of accumulation of metal fatigue and failure. Hence, it may be
concluded that testing cyclic fatigue of reciprocating instruments is as valuable as testing cyclic fatigue of rotary
.instruments.
Reciproc_ instruments resisted cyclic fatigue significantly more than WaveOne_ instruments; these differences could be
related to the different cross-sectional design and/or the different reciprocating movement of
the two instruments.
Canal Shaping with WaveOne Primary Reciprocating Files and
ProTaper System: A Comparative Study Elio Berutti, MD, DDS,* Giorgio
Chiandussi, MS, PhD,† Davide Salvatore Paolino, MS, PhD, Nicola Scotti,
DDS,* Giuseppe Cantatore, MD,‡ Arnaldo Castellucci, MD, DDS, and
Damiano Pasqualini, DDS*
This study compared the canal curvature and axis modification after instrumentation with Wave- One Primary
reciprocating files (Dentsply Maillefer, Ballaigues, Switzerland) and nickel-titanium (NiTi) rotary ProTaper
(Dentsply Maillefer).
Canal modifications are reduced when the new WaveOne NiTi single-file system is used. (J Endod
2012;-:1–5
Furthermore, shaping tends to preserve the integrity and location of the canal and apical anatomy in
preparation for an adequate filling (2, 5, 6). The avoidance of both iatrogenic damage to the root canal
structure and further irritation of the periradicular tissue is demanding for all the newest
instrumentation techniques (2, 7). Maintaining the original canal shape using a less invasive approach
is associated with better endodontic outcomes (1). Previous studies have shown that canal
transportation leads to inappropriate dentine removal, with a high risk of straightening the original
canal curvature and forming ledges in the dentine wall (8, 9). Nickel titanium (NiTi) rotary instruments
have shown efficiency in achieving optimal root canal shaping (1, 10), with less straightening and
better centered preparations of curved root canals (2). The superelasticity of NiTi rotary files may allow
less lateral forces to be exerted against the canal walls, especially in severely curved canals, reducing
the risk of canal aberrations and better maintaining the original canal shape
(1, 11)
However, in clinical practice, these instruments may be subjected to fracture, mainly because of
flexural (fatigue fracture) and torsional (shear failure) stresses (12–14). Torsional stresses may be
increased with a wide area of contact between the canal walls and the cutting edge of the instrument
(3, 15). To reduce such stresses, the ProTaper rotary design combines multiple progressive tapers,
adequately maintaining the original canal curvature (1, 16, 17). Canal curvature is suspected to be the
predominant risk factor for instrument failure because of flexural stresses and cyclic fatigue (1–3).
The WaveOne Primary file has the same tip size and taper features as the ProTaper F2 but a variable
section and reverse cutting blades.
E
NDODONTIC
CANAL PREPARATION WAVEONE SINGLE-FILE
TECHNIQUE by Clifford J. Ruddle,DDS
The mechanical objectives for endodontic canal preparation were brilliantly outlined almost 40 years ago. 1 When
properly performed, these mechanical objectives promote the biological objectives for shaping canals, 3D
cleaning, and filling root canal systems (Figure 1).2
However, recent advances for endodontic canal preparation have focused on the concept “less is more.”3 This
On the other hand, reciprocation, defined as any repetitive back-and-forth motion, has been clinically utilized to
drive stainless steel files since 1958
Fortunately, these risks have been virtually eliminated due to continuous improvement in file designs, NiTi alloy,
and emphasis on sequential glide path management (GPM).4
Compared to reciprocation, continuous rotation utilizing well-designed active NiTi files requires less inward
pressure and improves hauling capacity augering debris out of a canal.5
Serendipitously, in about 1998, Dr. Ben Johnson and Professor Pierre Machtou co-discovered the unmistakable
advantages of reciprocating NiTi files utilizing unequal bidirectional movements. Subsequently, in the late 1990s,
Machtou and his endodontic residents extensively analyzed this novel unequal reciprocating movement using the
entire series of not-yet-tomarket ProTaper files. Starting with the end in mind, Dr. Ghassan Yared, a former
student of Professor Machtou, performed exhaustive work to identify the precise unequalCW/CCW angles that
would enable a single reciprocating 25/08 ProTaper file to optimally shape virtually any canal. 7 Although this
specific reciprocation technique stimulated considerable interest, this file was never designed to be used in this
manner. Yet, Yared’s work rekindled interest to take this single-file concept closer to its full potential.
WAVEONE
In 2008, a team of 8 international clinicians including Drs. Ben Johnson, Sergio Kuttler, Pierre Machtou, Wilhelm
Pertot, Julian Webber, John West, Ghassan Yared, and myself, in collaboration with Dentsply International,
began the serious work of developing both a new reciprocating file and motor for shaping canals. In 2011,
following 4 years of R&D, both WaveOne (Dentsply Tulsa Dental Specialties and Dentsply Maillefer) and Reciproc
(VDW) were internationally launched as single-file shaping techniques. This paper will focus on WaveOne, as this
single-file reciprocating shaping technique utilizing unequal
CW/CCW angles is over 4 times safer and almost 3 timesis the system I helped develop and with which I am
most familiar faster than using multiple rotary files to achieve the same final shape. 8,9
DESIGN
Strategically, only 1 file is generally utilized to fully shape virtually any given canal. However, there are 3
WaveOne files available to effectively address a wide range of endodontic anatomy commonly encountered in
everyday practice (Figure 2). The 3 WaveOne instruments are termed Small (yellow 21/06), Primary (red 25/08),
and Large (black 40/08). The Small 21/06 file has a fixed taper of 6% over its active portion. The Primary 25/08
and the large 40/08 WaveOne files have fixed tapers of 8% from D1-D3, whereas from D4-D16, they have a
unique progressively decreasing percentage tapered design. This design serves to improve flexibility and
conserve remaining dentin in the coronal two-thirds of the finished preparation.
Another unique design feature of the WaveOne files is they have a reverse helix and 2 distinct cross-sections
along the length of their active portions (Figure 3). From D1-D8, the WaveOne files have a modified convex
triangular cross-section, whereas from D9-D16, these files have a convex triangular
cross-section. The design of the 2 WaveOne cross-sections is further enhanced by a changing pitch and helical
angle along their active portions. The WaveOne files have noncutting modified guiding tips, which enable these
files to safely progress through virtually any secured canal. Together, these design features enhance safety and
efficiency when shaping canals that have a confirmed, smooth, and reproducible glide path.
between martensite and austenite and produce a more clinically optimal metal than traditional NiTi itself. Studies
have shown that M-wire technology significantly improves the resistance to cyclic fatigue by almost 400%
compared to commercially available 25/04 NiTi files.10 The good news is that reducing cyclic fatigue serves to
clinically decrease the potential for broken instruments
There are 3 critical distinctions with this novel, unequal bidirectional movement. One, compared to continuous
rotation, there is a significant improvement in safety, as the CCW engaging angle has been designed to be
smaller than the elastic metallurgical limit of the file. Two, opposed to all other reciprocating systems that utilize
equal bidirectional angles, the WaveOne system utilizes an engaging angle that is 5 times the disengaging angle.
Fortuitously, after three engaging/disengaging cutting cycles, the WaveOne file will have rotated 360º, or turned
one CCW circle. This unique reciprocating movement enables the file to more readily advance toward the desired
working length.7 Three, compared to an equal bidirectional movement, an unequal bidirectional movement
strategically enhances auguring debris out of the canal.11 Auguring debris in a coronal direction promotes the
biological objectives for preparing canals, 3D disinfection, and filling root canal systems.
From our collective experiences, our group can report that the primary 25/08 file will produce an optimal final
shape in almost 90% of all canals, regardless of their length, diameter, and curvature. However, in longer,
narrower, and more curved canals, even when the 10 file is loose at length, the Primary 25/08 WaveOne file will
more predictably advance to the terminus of the canal when the glide path is expanded.
The Large 40/08 WaveOne file is used to complete the shape in larger diameter canals that are typically
straighter. Examples include certain maxillary incisors, single-canal bicuspids, and larger diameter canals within
maxillary and mandibular molar teeth. Recall, the usual WaveOne protocol is to initiate shaping procedures using
the primary 25/08 file. However, after carrying the Primary 25/08 file to the working length, gauging procedures
may confirm that the foramen is bigger than 0.25 mm. In these instances, the clinician will require the 40/08
WaveOne file to fully shape and finish these larger canal systems. With experience, the clinician will learn to
recognize these larger and more straightforward canals and is encouraged to initiate canal preparation
procedures utilizing only the 40/08 WaveOne file.
In summary, there are 3 WaveOne files. Following access and GPM procedures, the Primary 25/08 WaveOne file
will generally progress to the desired working length in three or more passes. As previously mentioned,
infrequently but on occasion, the clinician may require a second WaveOne file to complete a predictably
successful final shape. SHAPING TECHNIQUE The WaveOne single-file shaping technique is beautifully safe
and simplistic when attention in focused on the access preparation and GPM. As is required for any shaping
technique, straightline access to each orifice is emphasized. Attention is directed to flaring, flattening, and
finishing the internal axial walls.13 Importantly, the orifice(s) should be preenlarged and all internal triangles of
dentin eliminated. Perhaps the greatest challenge performing endodontic treatment is to find, follow, and
predictably secure any given canal
At the end of the day, a small-sized hand file is used to either confirm existing space is available or, alternatively,
to create sufficient space so mechanical files can safely follow a secured canal.13
To clarify, a canal is secured when it has a confirmed, smooth, and reproducible glide path.
With an estimated working length and in the presence of a viscous chelator, insert a 10 file into the orifice and
determine if the file will easily move toward the terminus of the canal. In shorter, wider, and straighter canals, a 10
file can usually be readily carried to the desired working length. A loose 10 file confirms sufficient existing space is
available to immediately initiate mechanical shaping procedures utilizing the Primary 25/08 WaveOne file.
However, in longer, narrower, and more curved canals, oftentimes the 10 file cannot be initially and safely worked
to length. In these instances, there is generally no need to select and use size 06 and/or 08 hand files in an effort
to immediately reach the terminus of the canal. Simply work the size 10 hand file, within any region of the canal,
until it is completely loose (Figure 5). The advantages of a sequential glide path have been previously
elucidated.4,1 When GPM procedures have been completed, the access cavity is voluminously flushed with a 6%
solution of NaOCl. Shaping can commence, starting with the Primary 25/08 WaveOne file (Figure 6a). Gentle
apically directed pressure will typically allow this instrument to run 2, 3, or 4 mm inward. After every few
millimeters of advancement, or if the Primary 25/08 WaveOne file will not easily progress, remove this file and
clean and inspect its flutes. Upon removing any mechanical shaping file from any canal, it is wise to irrigate,
recapitulate with a 10 file, then re-irrigate. Strategically, recapitulating with the 10 file moves debris into solution,
con- A brushing motion may be utilized to eliminate interferences, remove internal triangles of dentin, or to
enhance shaping results in canals which exhibit an irregular cross-section. In one or more passes, continue with
the Primary 25/08 file through the body of the canal. Removing canyons of restrictive dentin from the coronal twothirds of a canal creates a more direct path to its apical one-third, improving accuracy when determining a precise
working length. Especially in longer, narrower, and more curved canals, the apical one-third of virtually any canal
can be more predictably secured when pre-enlargement procedures have been performed first. A pre-enlarged
canal improves the ability to more readily direct and slide a precurved small-sized hand file to the full working
length. In the endodontic vernacular, “get behind the handle, gently slide the file, and find the foramen”.
Regardless of the glide path sequence, once the apical one-third has been fully negotiated, establish working
length, confirm patency, and verify there is a smooth reproducible glide path. The glide path is secured when a 10
file is loose at length and can “slip and slide” and “slide and glide” over the apical one-third of the canal.13
When the canal is secured, the Primary 25/08 WaveOne file can generally be carried to the full working length in
one or more passes (Figure 7). When this Primary file will not readily advance in a secured canal, then the Small
21/06 WaveOne file may be utilized. This file will typically reach the desired working length in one or more
passes. The Small 21/06 file may be the only shaping file taken to the full working length, especially in more
apically or abruptly curved canals. However, with the anatomy in mind, to encourage 3D disinfection and filling
root canal systems, more shape may be indicated. In these instances, the 25/08 file will generally advance
through any region of a canal where the shape has been previously expanded utilizing the small 21/06 bridge file.
Once the Primary 25/08 WaveOne file readily moves to the working length, it is removed. The finished shape is
confirmed when the apical flutes of this file are loaded with dentin. Alternatively, the size of the foramen can be
gauged with a size 25/02 hand file (Figure 8). When the size 25 hand file is snug at length, the shape is done. If
the size 25/02 hand file is loose at length, it simply means the foramen is larger than 0.25 mm. In this instance,
gauge the foramen with a size 30/02 hand file. If the size 30 hand file is snug at length, the shape is done. If the
size 30 hand file is loose at length, proceed to the Large 40/08 WaveOne file to more optimally prepare and finish
these larger canals. Upon reaching the working length, remove the 40/08 WaveOne file and inspect its apical
cutting flutes. If the flutes are loaded with dentine mud, there is visual confirmation that this file has cut its shape
in the apical one-third. Alternatively, the terminal size of the preparation can be gauged using a size 40/02 hand
file. When the size 40/02 hand file is snug at length, the shape is done and the foramen is confirmed to be 0.40
mm. When the 40/02 hand file is loose at length, it simply means the foramen is larger than 0.40 mm. In these
instances, other methods may be utilized to finish these larger, typically less curved, and more straightforward
canals. There are differing opinions regarding the optimal size and taper to prepare the apical one-third of any
given canal. Importantly, clinicians should not be trying to mechanically prepare “round” foramens; rather,
clinicians should be trying to “clean” foramens. Cleaning is readily accomplished in a preparation that has a
sufficiently tapered resistance form. Well-shaped canals promote the exchange of irrigants into all aspects of the
root canal system.15 Evidence is available that clearly shows a 40/06 preparation is no cleaner than a 20/10
preparation.16 Articles have been accepted for publication that demonstrate the WaveOne shapes preserve and
maximize remaining dentin, accurately follow and shape the original pathway of the canal, and maintain the
position of the foramen (Figure 9).17 The WaveOne shapes of 25/08 and 40/08, in combination with active
irrigation, have been shown to produce consistently clean root canal systems that any dentist can effectively fill in
three dimensions (Figure 10).15
Zehnder : Root Canal Irrigants. JOE — Volume 32, Number 5, May 2006
pages 389-398
A favorable outcome of root canal treatment is defined as the reduction of a radiographic lesion and absence of
clinical symptoms of the affected tooth after a minimal observation period of 1 yr (1).
Evaluation of the Effect of Endodontic Irrigation Solutions on the
Microhardness and the Roughness of Root Canal Dentin Hale Ari, DDS,
PhD, Ali Erdemir, DDS, PhD, and Sema Belli, DDS, PhD
Pecora et al. (23), Chng et al. (24), and Lewinstein et al. (7)
reported that high concentration of hydrogen peroxide caused the
great decrease in dentin microhardness. The significant alteration
in dentin hardness after irrigation treatment indicates direct effects
of these chemical solutions on the components of dentin structure
(25, 26). Hydrogen peroxide affects the inorganic parts of dentin
through acidic demineralization and attacks the organic-rich intertubular
dentin by collagen denaturation action (7). Organic-dissolving
properties of sodium hypochlorite on the collagen component
of dentin (25, 26) explains how the alternated irrigation with
these two solutions effect the hardness of dentin. Although 3%
H2O2 had no effect on surface roughness of root canal dentin, a
significant decrease on surface microhardness was shown in this
study. This result probably may be related to the material’s low
concentration.
Zhender, 2005
Teeth were stored in 0.1% thymol solution at 5°C.
Canals were instrumented using Gates Glidden drills followed by ProFile
instruments (Dentsply Maillefer, Ballaigues, Switzerland) crown-down,
so that finally a #45.04 instrument reached working length, which was
set 1 mm short of the anatomical apex. During instrumentation, canals
were irrigated with a 1% NaOCl solution. Subsequently, canals were
rinsed with copious amounts of deionized water. To assess the impact of
NaOCl on the complexing capacity of the sequestrant solutions under
investigation, these were either mixed with H2O or 1% NaOCl at a 1:1
ratio. The instrumented teeth were randomly divided into 10 groups
(n _ 6, each). In an experimental series, one tooth per group was
irrigated for 1 min with 5 ml of the complexing agent/H2O or complexing
agent/NaOCl mixture using an ISO-size 35 irrigating needle 1 mm
short of working length (Hawe Neos, Bioggio, Switzerland). Distilled
H2O and 0.5% NaOCl served as controls After experimental irrigation, teeth were copiously rinsed with
deionized water and longitudinally fractured. After critical point drying,
one fractured half of each root was mounted on a stub and goldsputtered
(SCD 030, Balzers Union, Balzers, Liechtenstein). Prepared
root canal surfaces were observed in a scanning electron
microscope (AMRAY 1810, Bedford, MA), and five photomicrographs
were taken at 500_ magnification from typical areas of the
coronal, the middle, and the apical thirds of the prepared root
canal. On each of these photomicrographs, the presence or absence
of smear layer was semiquantitatively estimated by two blinded observers
as follows: 0, 90 to 100% of dentinal tubules visible; 1, 50 to
90%; 2, 10 to 50%; 3, 1 to 10%; and 4, 0% of dentinal tubules visible.
Median scores per tooth were used for further calculations and
comparisons between different irrigation regimes. These were performed
using Kruskal-Wallis ANOVA followed by Mann-Whitney U test. To assess the
inter-dependence between calcium concentrations in eluates and smear
layer scores in respective teeth, Spearman’s rank correlation coefficient was
calculated. For statistical analyses, p _ 0.05 was considered to indicate a
significant difference.
Sectioning the Roots
The anatomical crowns were removed with a separating disk. A
shallow longitudinal groove was cut with a diamond separating
disk on the buccal and lingual surfaces of the root. The roots were
then split with a surgical chisel and mallet, resulting in a mesial and
distal half for each canal. All intact halves were used for evaluation.
Measurement of Surface Debris
The root sections were mounted with the exposed canal system
facing up on a calibrated grid. Photomicrograph ektachrome transparencies were taken of the specimens using a stereomicroscope at
×20 magnification. The transparencies were then coded and randomized
by an investigator not associated with tooth instrumentation
or the photomicrography. The photomicrographs were projected
onto a screen to 24 times the original size to produce a 2 ×
3 foot image. A transparent mylar grid was placed over the projected
images. Each square in the grid represented a 200 ~m × 200
/,m subdivision of the root.
An evaluator, who was unaware of which specimen or group
was being scored, counted the total number of squares covering the
apical 6 mm of canal space and the number of squares that
contained debris (Fig. 1). Particles or chips of any structure on the
surface of the root canal were judged as debris.
A debris percentage was calculated for each specimen by dividing
the number of debris containing squares by the total number
of squares. A mean debris score was then calculated for each
group. Differences among the treatment groups were determined
using a one-way analysis of variance and Bonferonni post-hoc tests
(p < 0.05).