SCIENTIFIC ARTICLE
Australian Dental Journal 2009; 54: 326–333
doi: 10.1111/j.1834-7819.2009.01158.x
Internal bleaching of teeth: an analysis of 255 teeth
P Abbott,* SYS Heah*
*School of Dentistry, The University of Western Australia.
ABSTRACT
Background: Studies about bleaching have not analysed factors that affect the outcome. This aim of this study was to
analyse the outcome of, and the factors associated with bleaching.
Methods: Internal bleaching was done on 255 teeth in 203 patients. Colour was assessed pre-operatively, postoperatively
and at recalls. The cause and type of discolouration, number of applications, bleaching outcome, and colour stability were
assessed.
Results: The most common teeth were upper central (69 per cent) and lateral (20.4 per cent) incisors. Trauma was the most
common cause (58.8 per cent), followed by previous dental treatment (23.9 per cent), pulp necrosis (13.7 per cent) and pulp
canal calcification (3.6 per cent). Dark yellow and black teeth required more applications of bleach than light yellow and
grey teeth. Colour modification was ‘‘good’’ (87.1 per cent) or ‘‘acceptable’’ (12.9 per cent). Teeth restored with glass
ionomer cement ⁄ composite resin had good colour stability, but this was less predictable with other restorations. No teeth
had external invasive resorption.
Conclusions: Bleaching endodontically treated teeth was very predictable, especially for grey or light yellow discolourations. Glass ionomer cement ⁄ composite restorations were effective at preventing further discolouration. Patient age and
tooth type did not affect treatment outcome and no cases of external invasive resorption were observed.
Keywords: Internal bleaching, outcome, discolouration.
Abbreviations and acronyms: EIR = external invasive resorption; GIC = glass ionomer cement; PCO = pulp canal calcification; PN = pulp
necrosis.
(Accepted for publication 19 April 2009.)
INTRODUCTION
Internal bleaching is a conservative means of managing
discoloured root-filled teeth. The primary indication for
internal bleaching is intrinsic (internal) discolouration.
Such discolourations have a number of different causes
which can be either local or systemic, and they are
distinct from those resulting in extrinsic (external)
staining.1
Blood products and their subsequent derivatives can
disseminate into the dentinal tubules after trauma to the
pulp or when the pulp is removed. As haemolysis
continues, various iron compounds are produced which
can be converted into black ferric sulphide. This is the
most common cause of intrinsic discolouration according to Grossman,2 but degrading proteins, as is the
eventual situation with pulp necrosis, can also cause
discolouration.3,4 In 1967, Nutting and Poe5 reported
that pronounced discolouration was more likely to
accompany pulp haemorrhage than pulp degeneration
326
without haemorrhage. Dental restorative materials,
including root filling materials, can also cause intrinsic
discolouration.1 If remnants of root filling materials
and some root canal medicaments are left in the pulp
chamber, the substance can infiltrate into the surrounding dentinal tubules and cause staining. Unfortunately,
the discolouration caused by metal ions such as staining
due to amalgam generally cannot be removed by
internal bleaching.4
Systemic causes of intrinsic discolouration include
tetracycline-containing medicines and high levels of
fluoride consumption.1 Pulp canal calcification is
another form of intrinsic tooth discolouration.1 It is
normal for odontoblasts to continuously form dentine
throughout the life of the tooth, but bacterial challenge
or other stimuli such as trauma to a tooth can
accelerate this protective mechanism. Hence, it is not
uncommon to observe pulp canal calcification in elderly
patients or in traumatized teeth. Accompanying pulp
canal calcification is a decrease in the translucency of
ª 2009 Australian Dental Association
Outcome of internal bleaching
the tooth combined with a yellowing or dark discolouration of the tooth.1
The advantages of internal bleaching have been well
reported in the literature. Conservation of tooth structure and achievement of good aesthetics is possible while
the procedure is inexpensive and simple to perform.1
However, the process requires a root-filled tooth, into
which a bleaching paste can be placed in the pulp
chamber. Hence, discoloured teeth with normal pulps, as
is usually the case with tetracycline staining and often
with pulp canal calcification, must undergo elective
endodontic treatment and root canal filling prior to
internal bleaching. Other restorative dental treatment
options such as porcelain veneers or crowns may be
considered in such cases in order to avoid the possible
risks and disadvantages of elective endodontic treatment.
Bleaching has been a topic of some concern in the
past for several reasons. Colour stability after bleaching
has been reported in the literature by many authors
with varying results.6–9 There have also been concerns
about the low pH levels that are caused by hydrogen
peroxide (H2O2) when used alone4 and bond strength
of the final restoration has been shown to be negatively
affected by residual bleaching solution.10 Therefore, it
is recommended that a period of 7–10 days be allowed
before the final restoration is placed to overcome this
latter problem.1
External invasive resorption (EIR) has been reported
to have an association with internal bleaching, both
with and without the application of heat.11 In 1979,
Harrington and Natkin reported seven cases of external
invasive resorption after internal bleaching using a
combined technique.12 Another case series of 11 teeth
with EIR after internal bleaching was reported by Cvek
and Lindvall in 1985.13 Currently, it is thought that the
cause is the passage of H2O2 through the dentinal
tubules and cementum to irritate the periodontal
tissue.14 The true incidence of external invasive resorption following internal bleaching has yet to be determined although Heithersay et al.15 reported that only
1.9 per cent of approximately 200 cases developed EIR
over a 19-year follow-up period after bleaching.
Chlorinated lime was first used for internal bleaching
in the early 1900s.4 Since then many other solutions
such as oxalic acid, chlorine compounds, sodium
peroxide and sodium hypochlorite, have been used to
improve the efficacy and outcome of internal bleaching.4 A thermocatalytic technique was introduced in
1924 by Prinz,4,16 who used 20–25% H2O2 applied to
the pulp chamber and activated by heat lamps or hot
instruments. This was proposed by many as the best
method of internal bleaching due to the high reactivity
of H2O2 in response to heat. Another popular technique, known as the ‘‘walking bleach technique’’ was
described in 1938 by Marsh and published by Salvas.17
Hydrogen peroxide by itself has an acidic pH value
ª 2009 Australian Dental Association
between 2 and 3 but when combined with sodium
perborate in the ratio of 2:1 g ⁄ ml, the pH becomes
alkaline.18,19 The increase in pH buffers the H2O2 and
this significantly improves the whitening efficiency.20
Currently, 35% H2O2 and sodium perborate are
commonly used in the walking bleach technique.1
There is little doubt that a short-term improvement in
tooth colour can be predictably achieved in most cases.
However, the long-term prognosis of intracoronal
bleaching has been reported by several authors with
variable results. Three possible causes of colour regression have been postulated, namely: (1) chemical
reduction of oxidation products; (2) marginal breakdown of the final restoration; and (3) the inherent
permeability of the enamel and dentine to extrinsic
substances.9 The variation in results may be due to
inadequate numbers of cases, differing bleaching techniques and final restorations, as well as varying
definitions of colour regression. Howell9 studied the
longevity of intracoronal bleaching in 43 teeth and
found that short-term outcome was good, but colour
regression occurred in 53 per cent of the teeth after one
year. Chandra and Chawala21 reported that only 17 out
of 239 teeth showed colour deterioration after one year
and that there was evidence of restorative margin
deterioration in all of these cases.21 Brown22 reviewed
80 teeth in 1965 by comparing pre- and post-treatment
photographs. He reported that of those teeth that
responded to bleaching, 46.3 per cent showed some
colour regression over 1–5 years. Howell concluded
that those teeth that are more difficult to bleach have a
greater tendency to discolour again after treatment.9
Currently, there is little information in the literature
that relates the outcome of internal bleaching to the
pre-bleaching colour and the cause of the discolouration. Hence, the main aim of this study was to assess
the initial outcome of internal bleaching relative to the
original colour, the cause and degree of discolouration.
The teeth were also reviewed after bleaching to monitor
the long-term stability of the colour and whether EIR
developed.
MATERIALS AND METHODS
This study was a retrospective review of 255 consecutive teeth that were bleached by a single operator in
203 patients and followed up for up to five years. The
bleach technique as described by Abbott1 was used
following root canal filling of the teeth. Prior to
bleaching, the tooth colour was assessed and recorded
along with the cause of the discolouration. As part of
completing the root canal filling, the gutta percha was
removed to a level 2.5 mm below the cemento-enamel
junction and then a 2.5 mm thick base of Cavit (ESPE
3M; Norristown, PA, USA) was placed as a base over
the gutta percha to ensure that none of the bleaching
327
P Abbott and SYS Heah
solution would enter dentinal tubules in the root
portion of the tooth. Cotton wool and Cavit, used as
a temporary restoration, were placed in the endodontic
access cavity and left for one week to allow the Cavit
base to set completely before bleaching. At the first
bleaching appointment, the temporary restoration
(Cavit) and cotton wool were removed. The Cavit base
was checked to ensure it followed the cemento-enamel
junction contours. Liquid orthophosphoric acid
(37.5%) was used to etch the entire access cavity for
30 seconds and then this acid was thoroughly washed
out of the access cavity. A thick paste consisting of fresh
35% hydrogen peroxide and sodium perborate powder
was prepared immediately prior to use and then it was
packed into the cavity. Some of the bleaching paste was
removed from the proximal and palatal aspects to
provide retention for temporary restoration of the
access cavity which was again done with Cavit. The
patients were then reviewed after 5–7 days to assess the
colour modification. If further colour modification was
required, then a fresh mix of the bleaching paste was
placed and the access cavity was again filled with Cavit.
Where more than one application of the bleach mixture
was needed, the teeth were reviewed at 5–7 day
intervals until the bleaching was judged to be complete.
When completed, the bleaching paste was rinsed from
the access cavity and a further temporary restoration
(Cavit) was placed. In the early stages of the study, a
cotton pellet was placed in the cavity before the Cavit
was placed but in the later stages the cavity was
completely filled with Cavit and no cotton pellet was
used. This variation was done because a small number
of the early cases had some colour regression during the
review period and all of these teeth were found to have
had the cotton pellet left in the cavities when they were
restored by the referring dentists.
Once the bleaching had been completed, the patient
was referred back to his ⁄ her general dentist for
restoration of the access cavity after a minimum of
two weeks. A letter was sent to the referring dentist
requesting that they restore the access cavity using the
glass ionomer cement (GIC) ⁄ composite resin sandwich
(laminate) technique.23 Instructions regarding the procedure for placing this type of restoration were also
enclosed. The particular brands of GIC, composite resin
and resin bonding agent used were recorded by the
referring dentist and returned to the author for analysis.
Pre-treatment and post-treatment photographs were
taken of each patient on Kodachrome 35 mm colour
transparencies. The patients were reviewed, initially
after six months and then at regular intervals for up to
five years wherever possible. During these review
appointments, the patients and in some cases where
relevant their parents, were questioned about their
perception of the colour of the tooth and whether it had
changed since the bleaching had been done. The tooth
328
was assessed clinically and photographs were taken for
comparison with previous photographs. In all cases,
there was consensus agreement about the colour of the
tooth between the operator and the patient ⁄ parent.
Factors assessed in this study included: patient age,
gender, tooth type, causes of the discolouration,
original tooth colour, initial outcome of bleaching,
number of applications of bleaching paste required,
colour stability over six months to five years, factors
related to subsequent colour changes, and the incidence
of external invasive resorption.
Colour modification achieved by internal bleaching
was assessed by the author and the patient (and in
young patients, also by the parents) using the classifications of ‘‘good’’, ‘‘acceptable’’ or ‘‘no change’’.
‘‘Good’’ colour modification was recorded when the
colour of the bleached tooth matched the colour of the
adjacent teeth and the patient (and ⁄ or parent) was
entirely pleased with the outcome. ‘‘Acceptable’’ colour
modification was recorded when the colour of the
bleached tooth was similar to the colour of the adjacent
teeth although not an exact match but the patient
(and ⁄ or parent) were pleased with the result. In
addition, the operator assessed that further colour
modification was unlikely to improve the outcome any
further. ‘‘No change’’ in colour was recorded if there
had been no modification of the tooth colour following
bleaching – this was assessed clinically and by comparing the pre- and post-bleaching photographs.
Any colour changes noted at review appointments
were classed as either ‘‘acceptable’’ or ‘‘unacceptable’’.
An ‘‘acceptable’’ change was one that was minor, did not
concern the patient (and ⁄ or parent) and did not require
further bleaching or other management. In contrast, an
‘‘unacceptable’’ colour change was one that required
further bleaching, veneering or crowning of the tooth.
Tooth discolouration was classified according to its
cause and colour. The causes were grouped as trauma,
pulp necrosis (PN), pulp canal calcification (PCO) or
dental materials used during previous endodontic
treatment. The discolourations were classified as grey,
black, light yellow and dark yellow.
All comparisons were tested for statistical significance at the 5% level using Pearson’s chi square, oneway ANOVA and the Scheffe post hoc test.
RESULTS
There were 203 patients with a total of 255 teeth
included in this study. Of the 203 patients, 46 per cent
were male and 54 per cent were female (Table 1).
Just one tooth was bleached in 162 patients, whereas
there were two teeth bleached in 30 patients and three
teeth in 11 patients (Table 1). The most common age
range of the patients was 11–20 years (Table 2)
although age was not significantly related to the cause
ª 2009 Australian Dental Association
Outcome of internal bleaching
Table 1. Number of patients and number of teeth
treated
1 tooth
2 teeth
3 teeth
Total no. of teeth
72
90
162
12
18
30
7
4
11
117 (46%)
138 (54%)
203 patients ⁄
255 teeth
Males
Females
Total no.
of patients
Table 2. Age distribution of the patients
Age range (years)
Number of patients
Per cent of patients
<10
11–20
21–30
31–40
41–50
51–60
6
108
27
35
23
4
3.0%
53.2%
13.3%
17.2%
11.3%
2.0%
Total
203
100%
Table 3. Tooth types bleached
Tooth
Maxillary
Mandibular
Central incisor
Lateral incisor
Canine
1st premolar
176
52
5
1
(69%)
(20.4%)
(2%)
(0.4%)
17 (6.6%)
4 (1.6%)
0
0
Total
234 (91.3%)
21 (8.2%)
of discolouration, the colour or the number of applications of bleach required. Of the teeth that required
bleaching, 91 per cent were maxillary teeth, predominantly central (69 per cent) and lateral (20.4 per cent)
incisors (Table 3). Only 8.2 per cent of the teeth were
mandibular teeth, and there was only one posterior
tooth included in this study.
Chi-square analysis indicated that there were significant differences (p = 0000) for the cause of the
discolouration and the initial colour of the teeth.
Table 4 shows that trauma to the teeth was significantly
more likely to cause grey or light yellow discolouration,
whereas previous dental materials used during endodontic treatment, PN and PCC generally caused dark
yellow discolouration.
The initial colour had a significant effect on the
outcome of bleaching (p = 0.000). Teeth that were
initially grey were the most predictable ones to bleach
with ‘‘good’’ colour modification being achieved in
all grey teeth (Table 5). Light yellow and black discolourations showed slightly less favourable results (94.9 per
cent and 86.1 per cent, respectively, were ‘‘good’’) while
a ‘‘good’’ result was only achieved for 67.5 per cent of
the dark yellow teeth. It was notable that all teeth in
this study had either ‘‘good’’ or ‘‘acceptable’’ colour
modification following bleaching and there were no
teeth that had no improvement in their colour.
The number of applications of bleaching paste
required for the various pre-operative discolourations
(Table 6) increased in order from light yellow,
grey, black to dark yellow. Approximately half the
teeth required only one application, 30 per cent
required two applications while about one-quarter
needed 3–5 applications to achieve a good or acceptable
result. Typically (i.e., approximately three-quarters
of each discolouration), the light yellow and grey
Table 4. Initial colour of the discoloured teeth and the cause of the discolouration
Pre-operative
discolouration
Cause of the discolouration
Trauma
Pulp canal
calcification
Pulp necrosis
No.
%
No.
%
No.
%
No.
%
No.
%
22
39
68
21
8.6
15.3
26.7
8.2
29
10
11
11
11.4
3.9
4.3
4.3
7
2
0
0
2.7
0.8
0
0
19
8
4
4
7.4
3.1
1.6
1.6
77
59
83
36
30.2
23.1
32.6
14.1
150
58.8
61
23.9
9
3.6
35
13.7
255
Dark yellow
Light yellow
Grey
Black
Total
Previous dental
treatment
Total
100
Table 5. The outcome of the bleaching procedure according to the pre-operative discolouration
Outcome of
bleaching
Pre-operative discolouration
Dark yellow
Light yellow
Total
Grey
Black
No.
%
No.
%
No.
%
No.
%
No.
%
Good
Acceptable
No change
52
25
0
67.5
32.5
0
56
3
0
94.9
5.1
0
83
0
0
100
0
0
31
5
0
86.1
13.9
0
222
33
0
87.1
12.9
0
Total
77
83
100
36
100
ª 2009 Australian Dental Association
59
100
100
255
100
329
P Abbott and SYS Heah
Table 6. The number of applications of the bleaching mixture required to modify the various pre-operative
discolourations
No. of applications
required
Pre-operative discolouration
Dark yellow
Light yellow
Total
Grey
Black
No.
%
No.
%
No.
%
No.
%
No.
%
1
2
3
4
5
10
4
27
29
14
3
0
5.2
25.0
37.7
1.2
3.9
0
44
11
3
1
0
0
74.6
18.6
5.1
1.7
0
0
61
18
2
2
0
0
73.5
21.7
2.4
2.4
0
0
9
18
5
4
0
1
25.0
50.0
13.9
8.3
0
2.8
118
74
39
20
3
1
46.3
29.0
15.3
7.8
1.2
0.4
Total
77
58.8
59
23.9
83
3.6
36
13.7
255
100
Table 7. The number of applications of the bleaching mixture related to the cause of the discolouration
No. of applications
required
1
2
3
4
5
10
Total
Cause of the discolouration
Trauma
Previous dental
treatment
No.
%
No.
%
94
41
12
3
0
0
62.7
27.3
8.0
2.0
0
0
15
20
10
13
2
1
150
58.8
61
Total
Pulp canal
calcification
Pulp necrosis
No.
%
No.
%
No.
%
24.6
32.8
16.4
21.3
3.3
1.6
1
2
4
2
0
0
11.1
22.2
44.5
22.2
0
0
8
11
13
2
1
0
11.1
22.2
44.5
22.2
0
0
118
74
39
20
3
1
46.3
29.0
15.3
7.8
1.2
0.4
23.9
9
3.5
35
13.7
255
100
Table 8. Number of patients due for, and who attended, recall appointments plus the number of teeth due to be,
and actually, reviewed. Note: the number of teeth at each recall appointment was less than the original starting
number shown in the Table
Recall interval
6
1
2
3
4
5
months
year
years
years
years
years
Due for review
Number attended ⁄ review
No. of patients
No. of teeth
166
24
82
37
24
11
206
8
92
46
27
17
discolourations required only one application of the
bleach paste. There were significant differences between
the following pairs: black and grey; black and light
yellow; dark yellow and light yellow; dark yellow and
grey; dark yellow and black.
Teeth that were discoloured by trauma required
significantly less applications (usually only one) than
those discoloured by other causes (Table 7). There were
no significant differences between the other causes and
the number of applications.
Patients were reviewed at intervals ranging from six
months up to five years, depending on their clinical
need and availability (Table 8). Of those due for a sixmonth recall, 78.3 per cent attended while 100 per cent
330
No. of patients
(% of those due to attend)
130
24
53
30
17
9
(78.3%)
(100%)
(64.6%)
(81.1%)
(70.8%)
(81.8%)
No. of teeth
(% of those due for review)
141
58
50
36
20
14
(68.4%)
(100%)
(54.3%)
(78.3%)
(74.1%)
(82.4%)
of those due for a one-year recall attended. Recall
attendance of those patients scheduled from two to four
years varied from 64.6 per cent to 81.1 per cent. A fiveyear recall was attended by 81.8 per cent of those who
were due for the appointment.
At the review appointments, the total percentage of
teeth that had discoloured again, to both ‘‘acceptable’’
and ‘‘unacceptable’’ levels, was 3.9 per cent (Table 9).
Four teeth (originally two dark yellow, one light yellow
and one grey) had an ‘‘acceptable’’ colour change,
while six teeth (originally two dark yellow, two light
yellow, one black and one grey) had ‘‘unacceptable’’
colour regression. Of those that were ‘‘acceptable’’, one
tooth discoloured after two years, another after three
ª 2009 Australian Dental Association
Outcome of internal bleaching
Table 9. Colour stability at recall appointments according to the pre-operative colour and the outcome of the
bleaching procedure
Pre-operative
colour
Initial
result
Original no.
of teeth
No. (%) with acceptable
colour change [recall time interval
when colour change noted]
No. (%) that had unacceptable
discolouration again [recall time
interval when discolouration noted]
Dark yellow
Dark yellow
Light yellow
Light yellow
Black
Black
Grey
Grey
Good
Acceptable
Good
Acceptable
Good
Acceptable
Good
Acceptable
52
25
56
3
31
5
83
0
2 (3.8%) [2 yrs, 3 yrs]
0
1 (1.8%) [4 yrs]
0
0
0
1 (1.2%) [4 yrs]
0
2 (3.8%) [6 mths, 3 yrs]
2 (8%) [6 mths, 1 yr]
0
0
1 (3%) [3 yrs]
0
1 (1.2%) [5 yrs]
0
years and two teeth after four years. Of those that were
‘‘unacceptable’’ and needed to be re-bleached, two had
discoloured after six months and the access cavity had
not been restored in both of these cases. One tooth
discoloured after one year, another two teeth after three
years and one tooth after five years.
Six teeth required re-bleaching due to restoration
breakdown and re-staining of the tooth structure. Five
of the teeth had been extracted for various reasons such
as periodontal issues, root fractures (horizontal, vertical
and crown ⁄ root) and inability to replace an unsatisfactory restoration. Four teeth required full coverage
crown restorations due to crown fractures, and three
teeth had veneers placed, one due to over-bleaching and
the other two were to replace old veneers that had been
placed prior to the bleaching.
No cases were found to have external invasive
resorption at the review appointments.
DISCUSSION
The results of this study reinforce that internal bleaching is a predictable, simple, quick and cheap procedure.
It is conservative of tooth structure, and maintains the
natural contour, occlusion, form and function of the
tooth. Potential problems associated with dental prostheses are avoided, such as periodontal problems,
changes in occlusion, root fractures, opposing tooth
wear, and aesthetic concerns. The procedure is safe if
adequate precautions are taken, such as those described
by Abbott.1 A thorough understanding of the chemistry
of the materials and the procedure is essential to ensure
patient and staff safety since the materials are caustic.
The 11–20 year old age group has been reported to
have a higher incidence of dental trauma than other age
groups24 and dental trauma is a common cause of
discolouration requiring internal bleaching. This study
supported these reports since just over half of the
patients belonged to this age group and over half of the
teeth in this study were discoloured as a result of trauma.
A typical endodontic practice has a demographic
distribution of females to males of 2:1.25,26 Contrary to
ª 2009 Australian Dental Association
this, the per cent gender distribution in this study was
almost equal (i.e., 46 per cent males:54 per cent
females). This may be due to a higher incidence of
dental trauma in boys when compared to girls24 which
is reflected in the distribution of teeth that required
bleaching, and the cause of the discolourations.
The distribution of specific teeth types encountered in
this study is consistent with the distribution of teeth
requiring internal bleaching reported in other studies.22,27,28 It also correlates to the typical distribution of
teeth reported in dental trauma studies.24
The majority of teeth had either grey or dark yellow
discolouration. The most common cause of discolouration was trauma to the teeth (58.8 per cent). Approximately half of these teeth had grey discolouration and
approximately one-third were light yellow. Previous
endodontic and restorative dental treatment led to
discolouration of about one-quarter of all teeth in the
study and the most common discolouration in this
group was dark yellow. Pulp necrosis was most likely to
cause dark yellow discolouration as was pulp canal
calcification but this latter condition was not a common
cause of discolouration overall.
The outcomes obtained with the internal bleaching procedure used in this study support previous
reports3,5,6,21,28 that have found internal bleaching to
be a predictable procedure. In this study, all teeth had
either ‘‘good’’ or ‘‘acceptable’’ colour change and,
notably, there were no cases that were considered to
have had no change at all. All of the grey cases and
almost all of the light yellow and black cases had
‘‘good’’ outcomes. The dark yellow teeth were harder
to bleach as about one-third of this group had only
‘‘acceptable’’ changes rather than ‘‘good’’ changes.
However, overall, the results of the bleaching were
very encouraging and predictable.
Overall, almost half of the teeth (but up to threequarters of the grey and light yellow cases) required
only one application of the bleaching mixture in order
to achieve ‘‘good’’ or ‘‘acceptable’’ colour modification. Another quarter required two applications and
15 per cent required three applications. Hence, the
331
P Abbott and SYS Heah
bleaching procedure was relatively quick in most cases
with little chair-side time involved – approximately
10–15 minutes per application.
The majority of teeth that had discoloured as a result
of trauma had colour modification after just one
application of the bleaching mixture. This was not
surprising since most of the traumatized teeth had
either grey or light yellow discolouration and these two
colours were the quickest to change. Teeth with
discolouration as a result of pulp canal calcification
were the slowest to be modified with up to almost half
of them requiring three applications of the mixture.
Not all patients were recalled at the same interval.
The recall interval depended on the initial reason for
endodontic treatment and the patient’s availability.
Attendance at recall examinations is a limiting factor
for all clinical review or follow-up studies. An overall
recall attendance of 50 per cent is considered to be
excellent with most endodontic studies only achieving
about 30–40 per cent attendance. In this study, the
majority of patients were recalled within the first year.
Although only a few patients attended their recall
appointments at five years (only 11 patients were due
for a five-year follow-up, of which nine attended), only
one tooth was found to have discoloured at the fiveyear recall appointment. In contrast, Feiglin6 reported
that of 20 teeth followed for six years after internal
bleaching, 45 per cent remained the same colour, or
were similar in colour to the adjacent tooth. A larger
cohort of patients followed up to five years may be
required to validly examine the long-term stability of
internal bleaching procedures.
All teeth reviewed in this study that had further
discolouration after internal bleaching were deemed to
have had an unsatisfactory restoration of the access
cavity. Cotton wool was found in the pulp chambers of
all cases that required further bleaching. The GIC ⁄ composite resin laminate technique when used to restore the
access cavity was found to produce less cases with further
discolouration compared to other restorative techniques
used. These findings reinforce the earlier stated concept
that further discolouration is likely to be a result of the
restoration breakdown and uptake of food stains into the
tooth rather than being due to chemical reduction of
oxidation products produced by the bleaching itself.
Although no cases of EIR were found in this study,
not all teeth were reviewed at five years, and more longterm studies are required to assess the true incidence of
EIR.29 However, at least in the short term, EIR was not
found to be associated with the internal bleaching
technique used in this study.
CONCLUSIONS
Internal bleaching is a predictable procedure. Colour
modification was usually ‘‘good’’ while the rest were
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‘‘acceptable’’. Teeth stained due to trauma, and with
grey or light yellow discolourations were easier and
quicker to bleach than darker teeth which required
more applications of the bleaching paste. Dark yellow
discolouration was the most difficult to modify and
stains from previous dental materials were also difficult
to remove. Some teeth discoloured again over 2–5 years
and this appeared to be related to breakdown of the
access cavity restoration. There were no cases of
external invasive resorption noted in the five-year
follow-up period.
REFERENCES
1. Abbott PV. Aesthetic considerations in endodontics: internal
bleaching. Pract Periodontics Aesthet Dent 1997;9:833–840.
2. Grossman L, Oliet S, Del Rio C. Endodontic Practice. 11th edn.
Philadelphia: Lea & Febiger, 1988.
3. Howell RA. Bleaching discoloured root-filled teeth. Br Dent J
1980;148:159–162.
4. Attin T, Paque F, Ajam F, Lennon AM. Review of the current
status of tooth whitening with the walking bleach technique.
Int Endod J 2003;36:313–329.
5. Nutting EB, Poe GS. Chemical bleaching of discolored endodontically treated teeth. Dent Clin North Am 1967;Nov:655–
662.
6. Feiglin B. A 6-year recall study of clinically chemically bleached
teeth. Oral Surg Oral Med Oral Pathol 1987;63:610–613.
7. Glockner K, Hulla H, Ebeleseder K, Stadtler P. Five-year followup of internal bleaching. Braz Dent J 1999;10:105–110.
8. Amato M, Scaravilli MS, Farella M, Riccitiello F. Bleaching teeth
treated endodontically: long-term evaluation of a case series.
J Endod 2006;32:376–378.
9. Howell RA. The prognosis of bleached root-filled teeth. Int
Endod J 1981;14:22–26.
10. Attin T, Hannig C, Wiegand A, Attin R. Effect of bleaching on
restorative materials and restorations–a systematic review. Dent
Mater 2004;20:852–861.
11. Rotstein I, Zalkind M, Mor C, Tarabeah A, Friedman S. In vitro
efficacy of sodium perborate preparations used for intracoronal
bleaching of discolored non-vital teeth. Endod Dent Traumatol
1991;7:177–180.
12. Harrington GW, Natkin E. External resorption associated with
bleaching of pulpless teeth. J Endod 1979;5:344–348.
13. Cvek M, Lindvall AM. External root resorption following
bleaching of pulpless teeth with oxygen peroxide. Endod Dent
Traumatol 1985;1:56–60.
14. Heller D, Skriber J, Lin LM. Effect of intracoronal bleaching on external cervical root resorption. J Endod 1992;18:145–
148.
15. Heithersay G, Dahlstrom S, Marin P. Incidence of external root
resorption in bleached root-filled teeth. Aust Dent J 1993;39:82–
87.
16. Ho S, Goerig AC. An in vitro comparison of different bleaching
agents in the discolored tooth. J Endod 1989;15:106–111.
17. Salvas C. Perborate as a bleaching agent. J Am Dent Assoc
1938;25:324–327.
18. Rotstein I. In vitro determination and quantification of 30%
hydrogen peroxide penetration through dentin and cementum
during bleaching. Oral Surg Oral Med Oral Pathol 1991;72:602–
606.
19. Kehoe JC. pH reversal following in vitro bleaching of pulpless
teeth. J Endod 1987;13:6–9.
ª 2009 Australian Dental Association
Outcome of internal bleaching
20. Frysh H, Bowles WH, Baker F, Rivera-Hidalgo F, Guillen G.
Effect of pH on hydrogen peroxide bleaching agents. J Esthet
Dent 1995;7:130–133.
27. Holmstrup G, Palm AM, Lambjerg-Hansen H. Bleaching of
discoloured root-filled teeth. Endod Dent Traumatol 1988;4:197–
201.
21. Chandra S, Chawla TN. Clinical evaluation of various chemicals and techniques of bleaching of discolored root filled teeth.
J Indian Dent Assoc 1972;44:165–171.
28. Amato M, Scaravilli M, Farella M, Riccitiello F. Bleaching teeth
treated endodontically: long-term evaluation of a case series.
J Endod 2006;32:376–378.
22. Brown G. Factors influencing successful bleaching of the discolored root-filled tooth. Oral Surg Oral Med Oral Pathol
1965;20:238–244.
29. Szajkis S, Tagger M, Tamse A. Bleaching of root canal treated
teeth and cervical external resorption: review of the literature.
Refuat Hashinayin 1986;4:10–12.
23. McLean JW. Glass-ionomer cements. Br Dent J 1988;164:293–
300.
24. Bastone E, Freer T, McNamara J. Epidemiology of dental trauma:
a review of the literature. Aust Dent J 2000;45:2–9.
25. Abbott PV. Analysis of a referral-based endodontic practice:
Part 1. Demographic data and reasons for referral. J Endod
1994;20:93–96.
26. Waldman HB, Feigen ME. Endodontists in a period of improving
dental economics and changing realities of practice. J Endod
1990;16:179–181.
ª 2009 Australian Dental Association
Address for correspondence:
Winthrop Professor Paul Abbott
School of Dentistry
The University of Western Australia
17 Monash Avenue
Nedlands WA 6909
Email: paul.v.abbott@uwa.edu.au
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