Dottorato di Ricerca in Malattie Odontostomatologiche
Coordinatore: Prof. Giorgio Pompa
PHD project in
"CT EVALUATION OF CORTICAL BONE THICKNESS AND DENSITY
FOR ORTHODONTIC
MINI IMPLANT PLACEMENT .
Tutor:Prof.ssa Ersilia Barbato.
Dotorando: Dott.ssa Aisha Sofan.
A.A 2011/2012
Table of Contents
Introduction…………………………………………………………………………………………………………..………2
Properties………………………………………………………………………………………………………………..…5
Mini Screw Design……………………………………………………………………………………………………….5
Biocompatibility…………………………………………………………………………………………….…………..7
Osseointegration…………………………………………………………………………………….…………….. 7
Orthodontic Mini Screw Loading…………………………………………………………………………………8
Indications…………………………………………………………………………………………………………..………8
Contra-indications………………………………………………………………………………………………..……9
Clinical Applicatios……………………………………………………………………………………………………..9
1.Molar intrusion........................................................................................................10
2- Retained or tipped molars uprighting…………………………………………………….…………….12
1.a-1Transverse molar uprighting (torque). Labial cross bite (scissors)……………..….……12
1.b-Transversal molar uprighting (torque). Lingual cross bite………………………….………..13
2.Mesiodistal molar uprighting with coronary movement……………………………..……….…14
3- Correction of anterior open bite…………………………………………………………………….……..14
4- Correction of anterior deep bite……………………………………………………………………….…..16
5- Uprighting of occlusal plane tipped in frontal plane (canting ..................................17
6- Correction of extraction case…………………………………………………………………….…………18
7- Distalization…………………………………………………………………………………………………….…..19
a. Entire maxilla or mandible distalization………………………….…….20
b. Distalization in maxilla combining microimplants with transpalatal
bar in maxilla……………………………………………………………………………….…………….20
c. Distalization with pendulum and anchorage reinforcement
using microimplants in maxilla…………………………………,,,,,,………………………..21
d. Distalization using micro-implants, sliding tube and distalizing spring ……..22
e.Distalization using "z" spring in maxilla and mandible
f. Direct distalization with microimplants……………………………………………….…22
8. Forced eruption of retained teeth……………………………………………………………..……….…23
9- Bowing effect leveling………………………………………………………………………………………………23
10- Asymmetric expansion……………………………………………………………………………………23.
11 - En masse" dental movement…………………………………............................................24
a. "En masse" retrusion incisal - canine group……………………….…………………..……24
b. " En masse " anchorage loss …………………………………………………………………..……25
c. "En masse " molar distalization………………………………………………………………..…..26
d."En masse " lateral movement of four incisors………………………………………………26
Complications……………………………………………………………………………………………..……………27
injury to adjacent structures……………………………………………………………………27
Failure…………………………………………………………………………………………………….28
Fracture………………………………………………………………………………………….…….……28
Surgical technique ……………………………………………………………..…………………………………….28
Removal of the Mini-implants……………………………………………………………..…………….30.
Aim Of the Study………………………………………………………………………………………………..…30
Materials And Methods…………………………………………………………………………………………….30
Statistical Analysis………………………………………………………………………………..…………..………35
Results……………………………………………………………………………………………………………………..35
Discussion………………………………………………………………………………………………………..…….…40
Conclusion…………………………………………………………………………………………………………………41
Bibliography…………………………………………………………………………………………………………….42
List of Tables
Table 1. cortical bone thickness of adolescents and adults………………42.
Table II. cortical bone density of a adolescents and adults………………………………….42
Table lll. The average of the thickness and the density of cortical bone…………44
Table IV .the average of thickness and density based on sextant position………45
Table V. t test between maxilla and mandible………………45
Table VI.t test between adolescent and adult…………………………………..46
Table VII. t test between male and female………………………………………46
List of Figures
Fig (1)Microimplants mechanics. Direct anchorage…………………………………11
Fig (2) Microimplants mechanics. Indirect anchorage……………………………………….12
Fig (3) Temporary orthodontic mini screw implant design features…………………………..13
Fig (4) Diagram of molar intrusion……………………………………18
Fig (5) A,B mesiodistal molar tipping correction with coronary movement………………21
Fig(6) Mesiodistal molar tipping correction with radicular movement…..22
Fig (7) microscrew implant anchorage sliding mechanics for treatment of open bite…..23
Fig(8) A,B Correction of anterior deep bite with extraction and microimplants…….25
Fig (9) extraction mechanics
suggested by Park: Upper microimplan is used as
absolute
anchorage maxilla………………………………………………………………….27
Fig (10) Molar distalization with transpalatal bar and microimplants(lateral view)…….27
Fig (11) A, B, Distalization with transpalatal bar with absolute anchorage with microimplants and
closing coil springs………………………………28
Fig (12)Distalization with microimplant in palatal midline or two palatine microimplants and a
transpalatal bar, withchain pull……………………………………………………………..28
Fig (13) Pendulum appliance modified for anchorage with microimplants………………………29
Fig (14) microimplant borne expander………………………………………………….31.
Fig (15) Resistance centers (RC) of teeth……………………………………………………31
Fig (16) "En masse" retrusion of anterior teeth……………………………………….32
Fig (17) "En masse" posterior anchorage loss………………………….…….33
Fig (18) "En masse" lateral movement of all four incisor…………………………………34
Fig (19).Four view
windows performed
by SimPlant
software (Materialise, Leuven,
Belgium…………………………………………....38
Fig (20) . The measurements of cortical bone thickness in both side palatal and uccal…..39
Fig(21)2-dimensional interdental slice, showing cortical bone with measurements of buccal and
lingual cortical bone thickness………………………………..39
Fig(22)To measure the density of cortical bone we put implant with diameter and length
is1 mm…………………………….40
Fig (23). Measurement of the density of the cortical bone………………………..40.
Fig(24)Box polt diagramm show the density of cortical bone in different levels……………….43
Abstract
The purpose of this study are to evaluate the thickness and density of the cortical bone
at every interradicular areas of both jaws, and to assess the differences in cortical bone
thickness between adolescents and adults in 4 levels from alveolar crest. Materials and
methods. Pretreatment Computed Tomography scans,taken in the orthodontic
department of “La Sapienza” University of Rome, Italy. 48 patients were selected and
were divided in to 2 groups comprising adolescents (12-18 years of age) and adults (1950 years of age). The SimPlant software (Materialise, Leuven, Belgium) was used to
perform the measurements. Results. In this study it was found that there were
differences between males and females. The thickness and the density of the buccal
and palatal or lingual cortical bone in males were greater than in females. The thickness
and density of cortical bone in adult were greater than in adolescents. Conclusion. For
cortical bone thickness, there are different changes in the cortical bone between adults
and adolescents, but it was not found gradual changes in the 4 distances from the
alveolar crest. For cortical bone density there are different changes. There is a gradual
increase of density in the apical direction from the alveolar crest except in palatal
female at 8mm.
Introduction
orthodontic treatment is to achieve desired tooth movement with a minimum number
of undesirable side effects . 1 Strategies for anchorage control have been a major factor
in achieving successful orthodontic treatment since the specialty began. Edward Angle, 2
writing in 1900s, was one of the earliest to advocate the use of equal and opposite
appliance forces to control anchorage. Traditionally, anchorage is reinforced by
increasing the number of teeth bilaterally or using the musculature, extra-oral devices,
and the alveolar processes. Prevention of undesirable tooth movement in both arches is
now possible. The use of small titanium bone screws ,some authors called "Temporary
Anchorage Devices TADs" ; (also known as micro screws or mini screws. TAD has
increased the envelope of orthodontic treatment, providing an alternative to
orthognathic surgery (particularly in the vertical dimension) and allowing asymmetric
tooth movement in three planes of space. 3 (TAD) is a device that is temporarily fixed to
bone for the purpose of enhancing orthodontic anchorage either by supporting the teeth
of the reactive unit or by obviating the need for the reactive unit altogether. They can be
located transosteally, subperiosteally, or endosteally; and they can be fixed to bone
either mechanically (cortically stabilized) or biochemically (osseointegrated).4 TADs
provide the biomechanical advantage that provide more effective and efficient
treatment with fewer auxiliaries and other appliances. Predicting resistance to tooth
movement can minimize adverse responses, lead to more successful treatment of
complicated problems, and provide efficient care in less time. Teeth can be moved
directly (en masse without anchorage loss) to their final positions. Improved techniques
and information over the last two decades have enabled clinicians to obtain more ideal
tooth positioning. Much of this has come from cases reports published. 5 Miniscrews can
be used in conjunction with all types of orthodontic systems (edgewise, self-ligation,
expansion devices, etc). While biomechanical techniques have been simplified over the
last century, they however remain complicated.6 Miniscrew implants are widely used as
orthodontic anchorage for of these advantages: they are easy to place and remove, they
can be placed at various sites, even between roots, and the orthodontic force can be
loaded immediately compared with traditional dental implants. TADs performed
maximum anchorage, decrease the need for patient compliance.7-10
According to
experimental and clinical studies.TADs can provide sufficient and stable anchorage for
orthodontic treatment. However, some clinicians have observed mini-implant loosening
during orthodontic treatment.11-16 The success rates of Orthodontic Mini implants have
been reported to range from 37% to 97%.17-30 Studies have found that the stability of
TAD was affected by age, sex, craniofacial skeletal pattern, site and side of implantation,
latent period, loading protocol, dimension of TAD and angulation of to bone, insertion
torque, degree of TAD-bone contact, quality and quantity of the cortical bone, degree of
inflammation of the peri-TAD-tissue, thickness and mobility of the soft tissue, and root
proximity.12,17.21,25.27,30,31 Many studies have evaluated cortical bone thickness and bone
density for placement of mini-implants because bone thickness and density are reported
to be critical for stability.31-33 The stability of mini-implants is generally defined with two
main components:34primary stability is established from the mechanical retention
between the minimplant surface and bone; it is dependent on the thickness and
integrity of the cortical bone, the miniimplant design, and loading protocol.35-36
Secondary stability is achieved through continuous bone remodeling around the miniimplant, leading to osseointegration.37.38 The firmness of cortical bone is one of the
principal factors controlling the stability of mini-implants.39,40,41 Several quantitative
studies of corticalbone thickness (CBT) have been performed in attempts to improve the
success rate of orthodontic mini-implants.41,42 The clinician must plan a good position
from the biomechanical point of view, consider the gingival position (attached gingiva.
movable mucosa), and minimize the risk of damage to adjacent structures. X-ray or
computerized tomography (CT) images are used to examine the relationship between
roots and to measure the total bucco-palatal lingual thickness, the cortical plate
thickness, and the interradicular spaces. These measurements are then used to select
the appropriate shape, length, diameter, and neck height of commercially available
miniscrews. It is recommended that a miniscrew is inserted at the attached gingival level
in order to avoid gingival inflammation. Inflammation can lead to screw failures and
pain because of compression of gingival tissues. Many authors have studied anatomical
sites on dry skulls43,44 and on X-ray images,45-48 because there is substantial risk of
damaging the roots,49 or other important anatomical structures during TAD positioning.
Other authors45-54 have pointed to the physical characteristics of TADs, including the
diameter, length, shape, and pitch.55,56 It was recently shown57 that increasing the
penetration depth of TADs resulted in greater retention. Conversely, increasing the
abutment-tip distance from the cortical plate resulted in reduced retention. Placement
of the TAD to the cortical plate provided the best retention. Insertion at an oblique angle
from the line of force reduced the retention of TADs. Generally, for adequate retention,
clinicians should embed 71.2% of the length of the screw section of the TAD into the
alveolar bone; the required percentage is typically higher in the maxilla than in the
mandible.58 A recent study showed that the most significant factors for predicting TAD
failure were inflammation of the soft tissue surrounding a TAD and early loading within 3
weeks after insertion. The other factors tested included gender, type of malocclusion,
facial divergence, method of force application (power chain or Ni–Ti coil spring), arch
(upper or lower), type of soft tissue (attached gingival or removable mucosa), and most
cephalometric measurements that reflected dento-cranio-facial characteristics.59
Anchorage with microimplants according to the classification that made by Dr. Hyo Sang
Park60 can be divided into :
- Direct anchorage:
when the force is exerted directly from microimplant over the active segment (a tooth
or a group of teeth to be moved).
It consists of a continuous arch, two
microimplantsand elastic chain from the arch to microimplants.and crimpable hooks
which allow better vertical control and torque control of incisal group.
Fig (1)Microimplants mechanics. Direct anchorage
- Indirect anchorage : when the force is exerted over the active segment from the
reactive segment (a tooth or a group of teeth used as anchorage) and the anchorage of a
reactive segment is increased with rigid fixation to micro-implants.61, The method of
choice is always direct anchorage, but sometimes due to certain circumstances, an
indirect anchorage can be used.61,62 These circumstances can be:
- To improve biomechanical conditions.
- To optimize the force factors6
- Presence of anatomical structures which suppose certain risk for microimplant
insertion at indicated site inadequate for direct anchorage (presence of blood nerves
or vessels, proximity of maxillary sinus, too close dental roots, etc.).
- Bad quality of the bone at the indicated site for microimplant insertion adequate for
direct anchorage.
- Loss or mobility of micro implant in the site adequate for direct anchorage.
Fig (2) Microimplants mechanics. Indirect anchorage.
PROPERTIES of mini implants63
The main differences between the currently available miniscrew implants relate to their
composition, size, and design and include:
(1) The design of the mini -screw.
(2) The length of the implant
(3). The diameter of threaded portion.
(4) The alloy or metal used for their fabrication.
Design of Mini Screw
A typical mini screw implant has three basic components: a core, a helix (the thread),
and a head.64Each component is crucial to the function of the mini screw.
Fig (3)Temporary orthodontic mini screw implant design features.
The head of the screw provides a means for applying twisting torque to the core and
thread, and also acts as a point of orthodontic force application. Most mini screw
implants are of a male type head design. This provides an articulation point to the
screwdriver and offers control during implantation. The core forms the support of the
screw and is wrapped in a helical thread. The cross-sectional area of the core is
extremely important to the strength of the mini screw, because the core diameter
ultimately determines the torsional strength.65 A largest the core diameter, the lower the
incidence of screw fracture during the implantation procedure(see Fig 3).
The shank extends from head to the beginning of the threads. The pitch is the distance
between the threads on the screw. The lead of the screw is the distance the screw will
advance with each 360 degree turn. In a single threaded screw, the pitch will equal the
lead. Of the characteristics of a mini screw implant, the length has a minor effect on
distribution of stress, and the thread design and the diameter have the most significant
effect. According to finite-element analysis, implants that extend 4.0 mm in bone, and
implants that extend 6.0 mm in bone show a negligible difference in stress distribution.66
However, clinically, mini screw implants extending 4.0 mm into bone showed
unsatisfactory success rates. The 4.0 mm mini screw showed a high rate of failure, due to
the insufficient length to clinically engage cortical bone. Therefore, at least 5.0 mm of
screw length is needed to account for the tissue thickness and to effectively engage
bone. A mini screw length of 5.0 mm or more has not shown any increase in load
distribution, unless it is used for bicortical anchorage.66 Mini screw diameter has a
significant effect on stress distribution in bone. The larger the diameter of the mini screw
allows for a more favorable stress distribution. According to 3D finite element model
analysis, a 1.4 mm diameter implant that is placed in cortical bone (1.2 mm thick) can
tolerate 150g of orthodontic force, while a 1.8 mm diameter implant can tolerate 350g
of orthodontic force.67To increase the success rate of a mini screw implantation, features
have been added. These features include: a threadless coronal section of the screw; a
tapered core from apical to coronal; a lateral cutting groove; and a sandblasted or acid
etched surface. The threadless cylindrical neck helps to control tissue overgrowth, and
aids in the soft tissue adaptation. The tapered core increases stability,
by condensing bone as the mini screw is inserted into cortical bone. Mechanical
retention of the mini screw to bone can increase by sandblasting or acid etching the
surface of the mini screw. A lateral cutting grove helps to prevent the concentration of
stress, which could lead to mini screw fracture.68 In 2008, Kim showed that microgrooves
on the screws surface could have some effects on the arrangement of gingival
connective tissue fibers, and could positively affect soft tissue and bone tissue
adaptation around the mini screw implant.69 The majority of orthodontic mini screw
implants are either self-tapping, or self-drilling. Self-tapping screws have a fluted leading
edge and require a pre-drilling procedure. Self-drilling screws have a corkscrew like tip
and pre-drilling is not required.70Most common mini screws have diameters ranging from
1.2 to 2 mm. A tapered mini screw that has an initial diameter of 1.5 mm will have a
decreased diameter at the tip to 1.2–1.1 mm. The difference between the initial
diameter and the tip is approximately 0.3–0.4 mm.15 The length of the mini screw can
vary from 4 mm to 12m.
Biocompatibility
Implants for orthodontic anchorage are made of alloplastic materials. Each material has
its own advantages and disadvantages with regard to physical properties, such as
biocompatibility,
mechanical
strength,
machinability,
and
elasticity.71-73
The
biocompatibility of materials is most important not only for formation of the interface
but also for maintenance of the interface.70-73 Leakage of ions or corrosion products from
implants leads to bone resorption and fibrous encapsulation.74,75
Osseointegration
Osseointegration generally is defined as the direct anchorage of an implant by the
formation of bony tissue around the implant without the growth of fibrous tissue at the
bone-implant interface.76-78 . Osseointegration is a series of healing processes that form
new bone tissue with the implant surface. Partial osseointegration represents a distinct
advantage in orthodontic applications, allowing effective anchorage to be combined with easy
insertion and removal.Because
complete osseointegration of screws used in orthodontic
applications is a disadvantage that complicates the removal process,most of these
devices are manufactured with a smooth surface, thereby minimizing the development
of bone ingrowth and promoting. Soft tissue attachment at ordinary conditions and in
the absence of special surface treatment regimens.79-81
Orthodontic Mini Screw Loading .
After implantation, the implant can be immediately loaded or loaded after a healing
period. Both loading methods have shown equal success rates with an orthodontic force
of 250g. In 2008 , Garfunkle studied the success rates of immediate loaded (within one
week), delayed loaded (between 3 -5 weeks), and unloaded (never loaded) mini screw
implants. Using a mixed-model analysis, Garfunkle found that there was no statistically
significant difference between the success rates of immediately loaded mini screws
(80.0%) and delayed loaded mini screws (80.95%), but the success rate for loaded mini
screws (80.49%) was significantly higher than that of unloaded mini screws (60.98%).
The higher success rate of the loaded mini screw implants could be due to the minimized
micro motions around the loaded mini screws, thereby decreasing the likelihood of periimplant bone resorption or fibrous encapsulation. Neither the timing of force
application, nor the force itself precipitated failure of the mini screw. Clinical orthodontic
forces can be applied immediately to mini screws with high clinical success rates. 82
Indications for skeletal anchorage82
Skeletal anchorage has, to a large degree, replaced conventional anchorage in situations
where anchorage is considered either critical, insufficient, or likely to result in
undesirable side effects such as vertical displacements generated by inter-maxillary force
systems. Another frequently found indication for its use is in cases of non-compliance.
While many so called “compliance free” anchorage systems have been introduced for
orthodontic treatment, none of these have proven to deliver the absolute anchorage
generated by skeletal anchorage systems. Finally but perhaps most importantly, skeletal
anchorage has widened the spectrum of orthodontics allowing the orthodontist to
perform treatments that could not, or, only with great difficulty, otherwise be done with
conventional mechanics.83.84 In general then, it can be stated that skeletal anchorage is
indicated where the forces acting on the reactive units are undesirable and cannot be
neutralized by occlusal forces.
Contra-indications83-85
1. Systemic diseases such as diabetes, osteoporosis, osteomyelitis, blood dyscrasias,
metabolism disorders, etc.
2. Patient undergoing the radiotherapy in arches.
3. Psychological disorders.
4. Presence of active oral infections.
5. Uncontrolled periodontal disease.
6. Presence of pathological formations in the zone, such as tumors or cysts.
7. Insufficient space for insertion of microimplant.
8. Thin cortical bone and insufficient retention.
9. Deficient quality of the bone.
10. Soft tissue lesions, such as lichen planus, leucoplakia,etc.
11 .Patient who does not accept microimplant treatment
Relative contra-indications
1. Tobacco, alcohol and drugs abuse.
2. Mouth breather.
3. Absence of ability to maintain the correct oral hygiene.
Clinical applications of mini-implants
Published clinical cases reports86,87 show that temporary anchorage devices have been
successfully used in a variety of malocclusions. Mini implants have been successfully
applied in: correction of open bites by posterior intrusion,86 class II correction, class III
correction, or in any treatment that requires maximum anchorage control. Mini screws
can be used in two ways, either directly or indirectly.
MOLAR INTRUSION
Molar intrusion with conventional mechanics using removable appliances, fixed
orthodontic arches for intrusion, magnets or springs, bite planes, trans palatal bar for
intrusion (separated from the palatal vault) or face-bow with high pull is less effective,
requires more patient cooperation and presents side-effects in comparison to facilitate
the intrusion mechanics using skeletal anchorage.
Fig (4) Diagram of molar intrusion
. Park87 presented two cases of upper molars intrusion .In the first case reported; using
labial and palatal micro-implants with a force of 100g during 6 months, a 3,5mm
intrusion was achieved in a 26-year old patient. The second case presented a 23-year old
patient where a palatal micro-implant and a trans-palatal bar were used to control the
torque, achieving the 2,5mm intrusion in 7 months
Sherwood et al 88 recommend molar intrusion with anchorage using mini-plates and labial
elastic pull. For torque increase control, they recommended the use of a 016"X022"
orthodontic arch , and in the maxilla recommended to add a .020" Round Australian
arch in overlay through the extra oral band tube, and activated it for constriction (in this
way a molar torque increase was under control during the intrusion). In mandible, they
recommend to carry out torque control with lingual arch. Molar intrusion was achieved
in approximately 6,5 months.
Yao et al89 emphasized to facilitate the molar intrusion with microimplants in comparison
to conventional mechanics, and added that both teeth intruded with this mechanics
(pulpal vitality) and adjacent tissues (alveolar bone and periodontal) present
no
alteration . They recommended medium intrusion forces (150-200g). a study was
carried out
with three –dimensional reconstruction of molar intrusion in 22 patients
with fixed appliances and microimplants. The result was an effective molar intrusion
carried out with this method. The average intrusion of the first molar was 3-4mm,with
the maximum of 5mm. The average second molar intrusion was 2mm and the average
second bicuspid intrusion was1-2mm.
Chang et al90 used labial and palatal microimplants for molar intrusion with a better
torque control. The first case was a 30-year old female patient who presented a 5mm
molar extrusion in palatal cusps and 1,5mm extrusion in labial cusps. The correction
was achieved in 5 months using 3,50z elastics.
Lin et al 91 reported cases of upper molars intrusion with labial and palatal microimplant.
The first case was a26-year old patient with a 5mm extrusion of the upper second molar
which was intruded in 5 months using forces of 150-200g. The second case was a 2S-year
old patient who presented a 5mm extrusion of upper first molar, and 2mm extrusion of
the upper second molar. The correction was achieved in 3 months .
Bae92 reported a case of effective intrusion of the lower first and second molars. A wire
was bonded from the occlusal surface of the first molar to the occlusal surface of the
second molar. Two micro-implants were inserted. The treatment was completed in 6
months.
2-Retained or Tipped Molars uprighting
Park has established, there were numerous techniques for uprighting of second molars,
especially in those cases where the first molar is absent. The side -effects in these
techniques always were problems . For example, prosthetic implants used as anchorage
have been very useful but the problem appears in its osseointegration and in minimum
quantity of space necessary for their insertion . This means that the patient must wait
three months before loading the implant with forces, and besides, its removal is
complicated ,too. Therefore, the insertion of micro-implants presents a great advance in
technique, and it is applicable in most of the treatments.
Park et al 93 said that when there is a discrepancy of mandible in posterior, second
molars erupt lingually, producing a cross bite. To correct this malocclusion, crossed "Z"
elastics are usually used ,but those provoke certain amount of extrusion of molars. Using
micro-implants this problem is avoided.
Yun et al94 affirmed that most of the methods for molar uprighting produce undesired
side -effects, such as extrusion of the molars used as anchorage. They suggested, molar
uprighting technique using direct anchorage. Micro-implant was inserted on mesial side
of the first molar to reinforce its anchorage. A TMA spring was used between the first
and second molar to upright it. Molar uprighting with micro-implants mechanicis more
simple and does not have any side effects on the rest of the teeth. It can be divided into
the following cases:
1. Transversal molar uprighting (torque):
a. Labial cross bite (scissors).
b. Lingual crossbite.
2. Mesiodistal molar uprighting with coronary movement, and with radicular
movement.
1.a- Transversal molar uprighting (torque).Labial crossbite (scissors)
Upper palatal and lower labial micro-implant can be used. The pull is carried out with
buttons and elastic chain .
The advantage of this system comparing to the "Z" elastics are:
- There is no molar extrusion but intrusion,
-No need for patient cooperation.
1.b-Transversal molar uprighting (torque). Lingual cross bite
The technique is very simple. A distal micro-implant was used and the pull
was carried out from the button on mesial surface and passed over the occlusal surface,
or a button on occlusal surface, or a button on labial surface and other on lingual surface
to control rotations.
A
B
Fig (5) A, mesiodistal molar tip ping correction with coronary movement ,B occlusal view
2.Mesio-distal molar uprighting .
Labial micro-implant is inserted mesially, and a band with a spring longer than the
central position of the molar resistance. It should be completed with a pull using a
lingual elastic chain to avoid molar rotation .
Fig(6) Mesiodistal molar tipping correction with radicular movement.
3-Anterior open bite correction
Skeletal anterior open bite is a complicated malocclusion characterized mainly by
overgrowth of the maxillary and mandibular posterior dentoalveolar heights, resulting
in a longer vertical facial dimension and a steeper mandibular plane.95.96 It is difficult to
decrease the heights of posterior dentoalveolar regions in the treatment of anterior
open bite. Many methods have been introduced to intrude the posterior teeth,such as
passive bite blocks,97 active bite blocks with magnets98,99 or springs100 high pull
headgear,101 fixed appliances, and vertical elastics.102-105 However, these traditional
techniques often can not intrude the molars, especially in adult patients. Thus, surgical
impaction of the maxilla is often the only way to obtain counter-clockwise rotation of
the mandible and a reduction of anterior facial height in adult patients with severe
skeletal open bite.106 Specially-designed miniscrews107-112 and miniplates113-117 have been
developed recently to obtain a stable anchorage source. Several studies114-116 have
reported the successful treatment of anterior open bite by intruding the mandible or
maxillary molars with mini-plate anchorage.
Fig(7)microscrew implant anchorage sliding mechanics for treatment of open bite.
Micro-implant can provide a stable skeletal anchorage to achieve molar intrusion.
Skeletal open bite can be effectively corrected by this orthodontic treatment option
without orthognathic surgery. Micro-implant placed between the second premolars
and the first molars in the maxillary arch, can provide anchorage for anterior retraction
and posterior intrusion of the teeth. Mandibular micro-implant, placed between the
first and second molars, can provide an anchorage for uprighting the molars and
counteract the mesial tipping at the same time of space closure. The mesial movement
of the mandibular posterior teeth makes the fulcrum move forward and allows a better
chance to close the mandibular plane angle or, at least, prevent opening the mandibular
plane angle. In addition, the use of micro-implant can eliminate the need for
intermaxillary elastics, which have been known to induce extrusion of the molars,and
clinicians might have more chance to close the mandibular plane. This can increase the
SNB angle and improve the profile.
4- Correction of anterior deep bite
Deep bite has potentially detrimental effects on mandibular and temporo mandibular
joint function and periodontal health as well as esthetics. Incisor intrusion can be
achieved with various treatment modalities. The most commonly used is the utility arch
technique In mini-implant anchorage system, forces can be applied to produce tooth
movement in any direction without detrimental reciprocal forces. 118 Some studies was
done to analyze the skeletal dental changes occurring during deep overbite correction
with mini-implant anchorage system and the used reinforced arches by a trans-palatal
arch. The mini-implant technique for true incisor intrusion can be considered superior to
the use of conventional arches. Many authors
119-121
have described the intrusion of
incisors with micro-implants in anterior deep bite treatments.
Ohnishi et al 122 described the treatment of a 19-year old patient with anterior crowding,
anterior deep bite and gummy smile. By means of incisors intrusion the correction of
overbite was achieved from 7,2mm to 1,7mm. They used micro-implant under the
anterior nasal spine and they intruded by pulling from the fixed orthodontic arch.
Kim et al 123 described the treatment of a 10.5 year old boy who presented Class II,
division 2 malocclusion with anterior deep bite, gummy smile and crowding in incisal
zone. They used MBT brackets in incisors and a 019 " x.025 " wire spring in sheath. A
6mm long micro-implant with a 1.6 mm diameter was inserted under the anterior nasal
spine. Two central incisors pro-inclination and intrusion was achieved using a closing
coil-spring. The upper horizontal part of the spring in sheath served to separate the
spring from the gingival in order to avoid lesions. When central incisors reached the level
of lateral incisors, a .014" sectional arch was added ,and the intrusion of all four incisors
was carried out. When deep bite correction was finished ,the arch was replaced by a
.018"
arch ,and elastic chain was added to close spacing between incisors. The
treatment was continued with Twin Block and fixed orthodontics. It is also possible to
correct anterior deep bite in cases with extractions by pulling from incisal group towards
distal and upwards.
Fig(8) A,B Correction of anterior deep bite with extraction and microimplants.
5- UPRIGHTING OF OCCLUSAL PLANE TIPPED IN FRONTAL PLANE (CANTING)
Yeon124 suggested tipped occlusal plane correction by means of intrusion of extruded
teeth and using micro-implants as anchorage. Correct diagnosis must be carried out,
which permited the extrusion of teeth on the side where they are in an upper position,
or intrusion of teeth which are in a lower position .Basically, this depends on vertical
dimension and esthetics (incisal and gingival exposure when patient is smiling and with
lips in rest). To extrude the teeth that are in an upper position, build up can be used on
the antagonist side in order to achieve disocclusion of the side in which the extrusion
should take place, and indicate maxillary elastics in antagonist molars or antagonist
micro-implants, which will depend on how much vertical control is necessary. To
intrude the teeth of one side, labial micro-implants are used. Micro-implants also are
very effective in treatments of transversally tipped occlusal plane where molar intrusion
should be carried out.
6- CORRECTION OF EXTRACTION CASES
The Cases treated with extractions with conventional mechanics have some problems
during the mechanics development:
a. Posterior anchorage control.
b. Anterior anchorage control
c. Torque loss in anterior teeth .
d. Tipping loss in canines.
e. Increased tipping in posterior teeth .
f. Increased overbite.
g. Vertical bowing effect control.
h. Transverse bowing effect control .
i. Increased friction .
All these problems can be easily controlled with the new mechanics, developed on the
basis of skeletal anchorage.124-134
Park124presented a case of skeletal Class ll
treated with sliding mechanics and
microimplants used as anchorage, in which the most important characteristics of this
mechanics were stressed .He called these technique "Micro Implant Anchorage" (MIA) .
Park125 reported a case of Class I malocclusion with
bi-protrusion treated with
extractions and micro-implants. The maxillary micro-implants were used for anchorage
and to get the direction of force closer to dental resistance centers (RC), as well as to
achieve the retrusion "en masse" of anterior teeth .Mandible micro-implants were used
to achieve mandibular anti-rotation with chin advance, which improved the convex
profile of a patient. This mechanics has already been described by Tweed-Merrifield147.
Park et al125presented a detailed study of sliding mechanics for extraction cases using
microimplants. Park 148 also presented three cases treated with micro-implants:
a case with micro-implants in maxilla, a case with micro-implants in mandible and
another one with micro-implants in both arches, emphasized the importance of vertical
control in molars during mandibular anti-rotation and improvement of profile esthetics.
Echarri 131,135 has studied the mechanics of extraction cases treatments(both lingual and
labial ones) with sliding mechanics, loop mechanics or with micro-implants.
Fig (9) extraction mechanics suggested by Park: Upper microimplan is used as absolute anchorage maxilla.
7. DISTALIZATION.136
According to clinical experience,136 the applications of micro-implant in distalization
moviments are:
Fig (10) Molar distalization with transpalatal bar and microimplants(lateral view)
Entire maxilla or mandible distalization.
It is used for Class II malocclusion treatment (" en masse" distalization of entire maxilla)
or for Class III malocclusion treatment ( "en masse" distalization of entire mandible).For
this purpose, 10 to 12mm long micro-implants are used, inserted in a vertical position;
- In mandible, in retro-molar zone, in labial cortical bone.
- In maxilla, in retromolar zone, in palatal cortical bone .These micro-implants can give
the force up to 300g.
Distalization combined with microimplants and transpalatal bar in maxilla.
Some designs153 that combine trans-palatal bars with microimplants can be used
,indicated for molars with correct tipping and rotation , but they need to be distalized
Using this technique, it is possible to get the point of force application as close to
resistance center as possible, and with this, " en masse" movement of molars .
Fig (11) A, B Distalization with transpalatal bar with absolute anchorage with microimplants and closing coil springs
Fig (12)Distalization with microimplant in palatal midline or two palatine microimplants and a transpalatal bar, with
chain pull.
Distalization with pendulum reinforced with microimplants inserted in
maxilla.136
Bayza et al
153
described the BAPA (Bone-Anchored Pendulum Appliance) that uses an
5mm long microimplant with 2mm diameter inserted 7–8 mm posteriorly from incisal
foramen, 3-4mm laterally from midline and with 50°-76°inclination in respect to palatal
plane. Pendulum appliance is fixed to micro-implant with curing resin.
.
Fig (13) Pendulum appliance modified for anchorage with microimplants.
Distalization using micro-implants, sliding tube and distalizing spring
Alfredo Bass described sliding distalization appliance micro-implants. It consists of a
microi-mplant inserted in zygomatic crest of alveolar bone, as parallel to first molar roots
as possible. It shouldn't be inserted between dental roots to avoid interferences during
distalizing movement. The bracket of second bicuspid was not bonded, a tube with a
hook (Ortho Organizers, Carlsbad, CA,USA) is incorporated into arch , but it is not fixed
so it can slide along the arch . A distalizing spring is put between sliding tube and molar
tube. Using metallic ligature, sliding tube is ligated to micro-implant, and coil spring is
compressed .Each activation is done in the same way.
Distalization using "z" spring in maxilla and mandible (mini-pendulum)
Kim 137 designed "z" spring which is used in a miniplate fixed with two microimplants. It
consists of a mini-plate and two micro-implants with a nut in the head. In this way two
micro-implants were inserted and an impression is taken to adapt mini-plate, weld the
tubes and adapt springs In continuation , mini-plate was placed and fixed with nuts. The
spring is activated for distalization.
Direct distalization with microimplants
Microimplants can be used in both arches for direct distalization, but they are usually
more used in mandible. Usually they are used in patients with an absence of molars,
inserted horizontally in alveolar bone. Depending on the bone height, it can be inserted
one 8mm long micro-implant, or two short micro-implants (5-6mm), joined with acrylic
resin or provisional crown.136
8. Forced eruption of retained teeth introduction
Gurosoy et al138 affirmed that one of the most frequent accidents during the included
canines treatment is debonding of attachment bonded to included tooth .That is why
they recommend to use a small micro-implant inserted in the included tooth, and to use
a ligature wire in micro-implant.
9. Bowing effect leveling.
All arches, when ligated to brackets, can provoke side-effects Microimplants are very
effective in bowing effect treatment and they should be inserted in the opposite
arch, using inter-maxillary elastics.
10. Asymmetric expansion.
Gamba et al
139
made a concluded study of periodontal effects produced by rapid
maxillary expansion. reduces .The thickness of labial cortical bone, especially at the
molar level. RME expansion appliance provokes dehiscence in labial cortical bone of
anchorage teeth, especially if the cortical bone is thin at the beginning. RME expanders
provoke more reduction in labial alveolar crest height especially at the level of first
bicuspids. Another problem difficult to solve is asymmetric expansion.
Fig (14) microimplantborneexpander
11 –"En masse" dental movement
Dental res istance center is approximatelly in the center of cervico-apical sense of dental
root which presents bone support.If the force (F) is applied to a body, and its application
point is in the resistance center (RC), "en masse" movement of that body will be
produced.
Fig (15) Resistance centers (RC) of teeth
"En masse" retrusion of incisal-canine group
The most recommended technique for "en masse" dental movement the retrusion of
all 6 anterior teeth using absolute anchorage. In this way, anterior group torque loss is
avoided, as well as canine retrociination ,increased overbite, and posterior teeth torque
loss. A crimpable hook is used adjusted or welded to arch mesially from the canine. This
hook must be sufficiently long to be at the level of RC (resistance center). Using a
microimplant between the second bicuspid and first molar and on the same height, an
indicated movement will be achieved.
Fig (16) "En masse" retrusion of anterior teeth
"EN MASSE" ANCHORAGE LOSS
To avoid mesio-inciination of posterior teeth and retro-inciination of anterior teeth
during the molar mesialization. Long hook is welded to the first molar band and
microimplant is inserted distally from the canine, at the . RC In this way, molars are
mesialized without side-effects.
Fig (17) "En masse" posterior anchorage loss.
" EN MASSE" MOLAR DISTALIZATION
Distalizing the molars with palatine microimplants and transpalatal bar, the force is
applied in resistance center RC, which helps to achieve "en masse" movement.
"EN MASSE" LATERAL MOVEMENT OF FOUR INCISORS
Based on . Nanda's mechanics,140 a lateral " en masse" movement of all four incisors can
be achieved to center the midline, without side effects .A sectional rectangualr arch will
be used, ligated to all four incisors and with a hook or loop in midline long enough to
reach RC. The microimplant was inserted mesially from the canine, and in RC, on the
side towards which we want to move the incisors. By-pass arch is inserted ligated to
canine, bicuspid and molar brackets, but it also passes over the lingual surface of incisors
to avoid their retro-inclination. In this way, "en masse" movement is achieved.
Fig (18) "En masse" lateral movement of all four incisor
COMPLICATIONS.
Inflammation, infection, and tissue irritation.
Inflammation and infection of the tissues around the implant site might occur, although
infection is generally not a problem.141-143 Meticulous oral hygiene is critical, and the use
of 0.2% chlorhexidine mouth rinses or dental floss dipped in 2% chlorhexidine can be
used to avoid and control any inflammation or infection that might occur.141,143 In the
event where the patient has purulence, pallor, or inflammation, management with an
appropriate antibiotic is indicated.144 One important factor to help avoid tissue
inflammation is the determination of the best site for miniscrew implant insertion. It is
advised that the mini implants should be inserted in keratinized gingiva when possible,
and the frenum and muscle tissue should be avoid.145,146 Hypertrophy of the mucosa
covering the implant might occur as a complication of placing it in non keratinized
gingiva. In such cases, the placement of a healing cap abutment is recommended at the
time of insertion,144 or the clinician could allow the mucosa to cover the miniscrew
implant, with only a wire or an attachment on it passing through the mucosa.141
injury to adjacent structures.
Another complication concerning miniscrew implant insertion is injuring adjacent roots,
periodontal ligaments, nerves, and blood vessels.142,143,145 If such a phenomenon occurs,
the patient usually shows pain on percussion and mastication ,in cases of periodontal
injur symptoms, and sensitivity to hot and cold in cases of root injury. In such
circumstances, the mini screw implant should be removed.142,143 The prognosis of the
injured tooth depends on whether or not there has been injury to the pulp.142 The
incidence of root damage from using mini-implants for orthodontic anchorage is even
lower when considering the careful planning that takes place before insertion of the
mini- implant, unlike those placed in an emergency situation.
Failure.
Failure of the mini-implants might occur if there is lack of stability at insertion time due
to in adequate thickness of the cortical bone.142 The mini- implant may be lost or become
loose as a result of various factors, such as inflammation of the peri-implant tissues and
improper placement
Fracture.
Fracture of the mini-implant may occur during removal of the mini-implant, if the neck
of the screw is too narrow.141,145 To avoid this complication, it is advised that miniimplants should be used with a diameter of 2 mm or larger.
Surgical technique.146
Before to the actual placement of any mini-implant, some important points must to be
considered to insure a successful treatment result:
-The desired tooth movements be defined in all three planes of space.
- The skeletal of anchorage to be used directly or indirectly , will determine the type
of screw head to select. Indirect anchorage was needed , (meaning that the point of
force application is not identical to the screw head) a mini-implant with a bracket like
head is indicated
-The diameter of the screw to use depends on the placement site.
-Soft tissue consideration. Not only the cortical bone but also the thickness of the
mucosa has to be considered in the selection of the proper screw and length of both
thread and trans mucosal collar must be determined because it is desirable to avoid the
presence of any threads in the soft tissues, the thread length of the screw has to be
chosen giving due consideration to the mucosal thickness at the placement site. . The
thickness of the mucosal can be assessed using either endodontic file with rubber stop
as a marker, or a periodontal probe with millimeter markings. Once the placement site
has been determined:
1. The patient is asked to rinse for (2 min) with a.2% clorhexidine mouth wash.
2. Local anesthesia of the mucosa at the insertion site is administered either by an
injection of 0.5 ml local anesthetic or by an alternative anesthesia of the mucosa.
3. Following the administration of anesthesia, the doctor has to prepare for the screw
insertion procedure according to established sterile field standards established for
intraoral surgery.
4. A sterile surface has to be available and prepared to receive all of the surgical
materials determined necessary for placement of the screws.
5. The doctor and assistants prepared according to established protocols for oral or
periodontal surgery (surgical scrub, surgical head cover, mouth mask, and sterile gloves).
6. The screw is picked up with the screwdriver, the grip on the screw tightened, and the
insertion performed.
When starting the insertion, the screw is kept perpendicular, or close to perpendicular,
to the bone surface. Once the screw is felt to have engaged the bone, the direction can
be altered to a more apical direction. Keeping this direction stable . The screw driver is
slowly and continuously turned until the clinician feels an increase in resistance. This is a
sign that the trans mucosal collar has reached the periosteal surface. At this point, the
turning of the screw is completed; continued turning would lead to a loosening of the
screw. Following insertion, the peri-implant tissues are gently rinsed with sterile saline
solution before the screws are loaded. It is recommended that the initial load not exceed
a maximum force of 50 cN and that the force be applied perpendicular, or as near to
perpendicular, to the long axis of the screw as possible. An intrusive or extrusive pull-out
force can also be accepted immediately following insertion; on the other hand, a
moment in either the clock or counter clockwise direction will lead to a shearing force
resulting in a loosening of the screw with a loss of primary stability. It is important to
instruct the patient in proper care and oral hygiene related to Mini-screws before
dismissing the patient
Removal of the Mini-implants
The removal of the Mini-implants is easily accomplished with the same screw driver as
used for insertion. The procedure can usually be done under application of a local
anesthetic gel. The removal site should be gently swabbed with a 0.2% Chlorhexidine.
The wound present at time of screw removal is minimal and usually closes within a few
days. In most cases, healing will continue safely.
Aim of study
To determine the safe zones for mini-implant placement in the maxilla and in the
mandible based on the measurement in the each inter-radicular areas by evaluation
of the thickness and density of the cortical bone with the effect of age and gender on
the studied anatomical measurements.
MATERIALS AND METHODS
Data were obtained from CT scans taken in the orthodontic department of "Sapienza"
University of Rome, Italy. For orthodontic patients , who made the CT scans for other
type of orthodontic treatment. 45 patients were selected and were divided into 2
groups comprising adolescents ( 12 -18 years of age) and adults (19-50 years age). The
scans were selected according to the age, sex requirements, and the following of
exclusion criteria:(1) missing or unerupted permanent teeth in the quadrant measured,
(2) periapical or periradicular pathologies or radiolucencies of either periodontal or
endodontic origin, (3) a significant medical or dental history (eg, use of bisphosphonates
or bone-altering medications, or diseases), (4) severe facial or dental asymmetries, and
(5) vertical or horizontal periodontal bone loss.The data were obtained with a spiral
multisliced Asteion Multi_ CT system (Toshiba Medical Systems.This scanner, with a
HeliCool Radiogenic tube and a real-time spiral of 12 frames ⁄s, produced 0.5-mm scans
in a scanning time from 0.5 to 2.3 s with a slice thickness from 0.5 x4 x 8 x4 mm and a
field of view from 180 to 500 mm. It had detectors of 896 Solid statusx32 mm, with a
distortion of 0.4 mm (HU < 10%). In this study, data processing and all measurements
were performed by SimPlant software (Materialise, Leuven, Belgium) , a program that
allows reconstruction of 3D models and images of anatomical structures along planes
and curves from data acquired with CT. With this program we imported CT images; then
we did the segmentation to create a 3D model from the 2D CT images, and the
panoramic curve was obtained. We found four view windows Figure(16) that show: 1)
2D cross sectional slices; 2)2D axial slices; 3) 2D panoramic slices; 4) 3D Model.
Fig (19) Four view windows performed by SimPlant software (Materialise, Leuven, Belgium.
Before measuring, each site was oriented in all view windows. For the measurements
made in interradicular areas of the maxilla and mandible, the sagittal panoramic slice
was used to locate in interradicular area of interest site . The slice was then oriented so
that the vertical reference line bisected the interradicular space and was parallel to the
long axes of the roots. The axial slice was then used to bisecting the interradicular
distance and oriented perpendicular to the bone surface in four levels at 2,4, 6 and 8
mm from the alveolar crest Figure (17).
Fig (20) .The measurements of cortical bone thickness in both side palatal and buccal.
Fig (21)Two-dimensional interdental slice, showing cortical bone with measurements of buccal and lingual
cortical bone thickness.
The bone density of the cortical plate was measured at 2,4,6 and 8 mm intervals apical
to the alveolar crest at each interradicular sites in both maxilla and mandible. Simplant
software was used to map and display bone density in the region of interest. A cube of
1mm was used to calculate the density of cortical bone at each level figure(18) . Bone
density was measured using Hounsfield units (HU) Figure (19), which are directly
associated with tissue attenuation coefficients.
Fig(22)To measure the density of cortical bone we put implant with diameter and length is1mm.
Fig (23)Measurement of the density of the cortical bone.
Statistical Analysis
Data was evaluated using a statistical analysis software (SPSS® software (Statistical
Package for Social Science, IBM Corporation, NY-USA). Quantitative data of each group
was described with mean values. The quantitative data was illustrated using tables and
histograms. Considering the values of thickness and density , the T-test was used to
determine the influence of different gender , age and arch on thickness and density .
The significance was set at P≤.05. Correlations between thickness , density and level of
measurements were tested with the Pearson correlation coefficient. The significance
was set at P≤.01.
Results.
In the table I shows the average of the cortical bone thickness ( buccal and palatal or
lingual) at different
measurement levels from the alveolar crest. fIn adults
maximum average of the measured
the
buccal cortical bone thickness at maxilla was
1.72mm, while minimum average of the measured buccal cortical bone thickness was
1.25mm.In adults the maximum average of the measured palatal cortical bone at the
maxilla was 1.73mm, while the minimum average of the measured palatal bone was
1.31 mm. In adults the maximum average of the measured
lingual
cortical bone
thickness at mandible was 1.99mm, while minimum average of the measured lingual
cortical bone thickness was 1.41mm. In adolescents
measured
buccal
cortical bone thickness at maxilla was 1.45mm, while minimum
average of the measured
cortical bone thickness was 1.22mm. In adolescents
maximum average of the measured buccal
1.73mm, while
the maximum average of the
minimum average of
the
cortical bone thickness at mandible was
the measured
cortical bone thickness was
1.38mm. In adolescents the maximum average of the measured palatal cortical bone
at the maxilla was1.38mm, while the minimum average of the measured palatal cortical
bone was1.19mm. In adults and adolescents maxilla, both males and females, the
average cortical buccal bone thickness (ACBBT) and the average cortical palatal bone
thickness
(ACBPT)had
no
significant
differences
at
all
the
distances
(2mm,4mm,6mm,8mm) from the alveolar crest. (see table I).
Table 1. cortical bone thickness of adolescents and adults.
Age
1218
Sex
Males
Females
Males
1950
Female
Arch
Maxilla
Mandible
Maxilla
Mandible
Maxilla
Mandible
Maxilla
Mandible
2mmB
1,38
1,51
1,23
1,67
1,48
1,43
1,28
1,47
4mmB
1,35
1,61
1,22
1,69
1,52
1,65
1,25
1,41
6mmB
1,38
1,66
1,23
1,75
1,65
1,67
1,27
1,49
8mmB
1,37
1,78
1,24
1,70
1,72
1,72
1,27
1,47
2mmP/
L
1,41
1,49
1,19
1,62
1,50
1,56
1,30
1,42
4mmP/
L
1,45
1,63
1,23
1,71
1,65
1,79
1,35
1,57
6mmP/
L
1,44
1,73
1,30
1,83
1,73
1,79
1,31
1,65
8mmP/L
1,45
1,72
1,27
1,78
1,72
1,99
1,32
1,62
In the table II shows the average of the cortical bone density (buccal and palatal or
lingual) at different
measurement
levels from alveolar crest. In both adults and
adolescents groups, the cortical bone (buccal and palatal or lingual ) showed significant
gradient changes increased from 2mm distance to 8mm. However the average values
show a decrease in palatal or lingual cortical bone density at 8mm measure. The range
of average bone density varied from 910,03 to 1327,90 HU for the maxilla and from
1212,87 to 1461,61 HU for the mandible. (see table II).
Table II. cortical bone density of a adolescents and adults.
Age
Sex
Males
12-18
Females
Males
19-50
Females
Arch
D
2mm
D
4mmB
D
6mmB
D
8mmB
D
2mmP/L
D
4mmP/L
D
6mmP/L
D
8mmP/L
Maxilla
941,22
1049,78
1086,81
1117,48
927,69
1102,80
1119,56
1102,71
Mandible
1246,32
1311,23
1373,10
1422,55
1341,77
1421,74
1454,08
1461,61
Maxilla
910,03
963,48
1001,17
1107,52
921,78
1031,69
1091,45
1065,04
Mandible
1212,87
1283,32
1355,97
1403,21
1320,99
1390,19
1412,43
1411,82
Maxilla
1058,52
1242,38
1262,06
1327,90
1169,33
1242,47
1217,18
1178,72
Mandible
1132,26
1247,93
1239,10
1281,87
1175,19
1255,03
1282,28
777,43
Maxilla
969,02
1025,84
1048,13
1096,75
941,13
1013,29
1034,49
1043,66
Mandible
1053,93
1086,23
1140,61
1189,98
1168,46
1242,33
1237,93
1310,21
Fig(24)Box polt diagramm shows the density of cortical bone in different levels
In table lll there were the average values of measured cortical bone thickness and
density. The table shows that , the average values of measured of buccal and palatal or
lingual cortical bone thickness was higher in adult than in adolescent , except ,in the
mandible female the buccal and palatal or lingual cortical bone thickness was higher in
adolescent than in adult. The buccal cortical bone and the palatal cortical bone were
thicker in the mandible than in the maxilla. The buccal
and the palatal cortical bone
were more density in the mandible than in the maxilla. The maximum average the
measured
of cortical bone thickness was 1,77mm in the mandible, however the
minimum average value of the cortical bone was 1,23mm in adolescent in the maxilla.
The maximum average value of buccal cortical bone density at maxilla was 1419,23
HU, while minimum average value of cortical bone density was 991,27HU. (see table I).
Table lll. The average of the thickness and the density of cortical bone
Age
12-18
19-50
Sex
Males
ARCH
ACBBT
Maxilla
Mandible
1,37
1,64
ACBP/LT
1,44
1,64
ACCBD_
1049,54
1336,22
ACCP/LD
1064,25
1419,23
Females
Maxilla
Mandible
1,23
1,70
1,24
1,74
991,27
1313,84
1021,88
1383,86
Males
Maxilla
Mandible
1,59
1,62
1,65
1,77
1226,09
1225,98
1201,07
1252,47
Females
Maxilla
Mandible
1,26
1,46
1,32
1,56
1042,86
1121,69
1004,60
1221,63
The buccal and palatal cortical bone of both jaws in the Posterior sextants
(maxilla left [MaxL], maxilla right [MaxR], mandible left [MandL], and mandible right
[MandR] in adult and adolescent had greater cortical bone thickness than the anterior
sextants (maxilla middle [MaxM] and mandible middle [MandM], except in maxilla
males in both adult and adolescents, that shows thicker anterior sextants(see table IV).
The t test was used to compare the maxilla and mandible cortical bone thickness and
density. It showed that the buccal and lingual cortical bone at the mandible was thicker
than buccal and palatal cortical bone at the maxilla. Also the buccal and lingual cortical
bone at the mandible was greater density than the buccal and palatal cortical bone at
the maxilla. The data was statically significative. (see table V)
Table IV .the average of thickness and density based on sextant position.
Age
12-18
Sex
Males
Arch
Maxilla
Mandible
females
Maxilla
Mandible
19-50
Males
Maxilla
mandible
females
Maxilla
Mandible
Sextant
Right
anterior
Left
Right
anterior
Left
Right
anterior
Left
Right
anterior
Left
Right
anterior
Left
Right
anterior
Left
Right
anterior
Left
Right
anterior
Left
ATCCB
1.33
1.43
1.36
1.80
1.42
1.72
1.28
1.20
1.20
2..08
1.38
1.59
1.51
1.53
1.76
1.76
1.50
1,58
1.25
1.23
1.33
1.62
1.20
1.61
ATCCP/L
1.40
1.47
1.43
1.72
1.58
1.64
1.26
1.25
1.21
1.86
1.57
1.79
1.62
1.67
1.65
1.80
1.72
1.79
1.30
1.31
1.35
1.61
1.45
1.66
ADCCB
1045.10
1090.02
1010.47
1374.02
1225.74
1421.52
1031.63
990.14
949.20
1420.64
1182.88
1344.92
1242.23
1236.89
1194.43
1225.70
1250.98
1195.10
1107.15
989.27
1039.10
1224,72
1017.79
1137.39
ADCCP/L
1061.65
1074.47
1055.17
1415.71
1411.83
1431.00
1015.18
1032.14
1018.05
1332.32
1417,34
1407,08
1271,97
1186.40
1139,64
1265.83
1279.88
1201.52
989.63
1088.03
920.11
1273.98
1215.20
1176.64
Table V- t test between maxilla and mandible.
maxilla VS mandible
Sig.
Difference between
means
Difference standard error
medie_sitiVmmV SPESSORE
,000
-,28576
,03118
medie_sitiVmmp SPESSORE
,013
-,30988
,02925
,000
-215,66869
21,91451
,027
-281,84571
21,12007
medie_siti V DENSITA
VESTIBOLARE
medie_sitiV DENSITA PALATALE
Then the t test was used to compare the two groups of age, the adolescents (Ages 1218) and the adults (Ages 19-50), it showed that the thickness and density of buccal and
palatal or lingual cortical bone in adult were greater than in adolescents except the
density of palatal or lingual cortical bone in adolescents was greater than in adults. The
data was statically significative just in the palatal cortical bone thickness.(see table VI).
Table VI.t
test between adolescent and adult
Adolescents 12-18 y VS adults 19-50y
medie_sitiVmmV
medie_sitiVmmp
medie_sitiVDmmv
medie_sitiVDmmp
Sig.
Difference between means
Difference standard error
,336
-,03308
,03436
,001
-,10845
,03267
,894
-3,25989
24,40519
,483
17,50705
24,94965
The t test was used to compare the gender groups males and females. it showed that the
thickness and density of the buccal and palatal or lingual cortical bone in males were
greater than in females. The data was statically significant. (see table VII).
Table VII. t test between male and female
Sig.
Difference between
means
Difference standard error
medie_sitiVmmV
,000
,21267
,03210
medie_sitiVmmp
,000
,22437
,03049
medie_sitiVDmmv
,000
153,74597
22,74124
medie_sitiVDmmp
,000
156,02788
23,24064
Male vs female
DISCUSSION
Turkyilmaz et al 147 demonstrated that it is possible to estimate primary implant stability
from pre-surgical computerized tomography(CT). Therefore, it would be desirable to
image every patient with CT, but not every clinician has access to a CT or CBCT scanner
and might lack some potentially important information. This investigation was intended
to supply a guideline when CT imaging is not possible. In general, the mandible provides
more cortical bone than the maxilla. In the present study was found that the mandible
buccal and lingual cortical bone thickness and density was greater than the maxilla .
Friberg et al148 found similar results in their morphometric study; they reported more
compact cortical bone in the mandible than in the maxilla. Baumgaertel et al149 found
the buccal mandible cortical bone thickness was greater than in the maxilla. In this study
was found that there was significant sex difference at inter-radicular sites of cortical
bone thickness and density in either the maxilla or the mandible. The thickness and the
density of the buccal and palatal or lingual cortical bone in males were greater than in
females. The sex differences in cortical bone thickness might be expected because
males have larger bite forces and masticatory muscles than females. Although females
tend to eat higher fiber foods such as fruits and vegetables, and males eat more meats
and foods with higher fat content.150. On the other side , Schwartzet al 151 found any sex
differences in cortical bone thickness for the mandible. Ono et al, 151 also found there
was no significant sex difference at inter-radicular sites 4 mm apical to the alveolar crest.
However, the same Authors found that cortical bone was thicker in males than females
at vertical levels 1 to 2mmand 5 to 9mmapical to the alveolar crest in the maxilla.
Farnsworth et al150 showed no significant differences in cortical bone thickness between
the sexes in either the maxilla or the mandible. In the current study it was not found
gradual changes in the cortical bone thickness in different locations by the distances
from the alveolar crest in apical direction at 2, 4, 6, 8mm.There were no significant
differences in locations measured. Deguchi et al.152 found the same result. Kee- Joon
Lee et al
155
also found an effect of the vertical level and a significantly larger inter-
radicular space in the apical region compared with the coronal region , especially in the
posterior area . They also found , in contrast, that the space between the central and
lateral incisors did not show a significant increase at the apical level (8 mm) compared
with that at 2 mm. Ono et al,152found that the cortical bone thickness tended to be
thicker at greater heights and thinner at shallow locations.
In the present study it was also found that the cortical bone thickness in the mandibular
buccal and lingual regions were thickest posteriorly and became progressively thinner
anteriorly ( see table IV). Schwartz-Dabney and Coll.151showed a cortical bone thickness
decrease from posterior to anterior. The same result was obtained by Farnsworth et
al.150 This pattern might also be explained by the higher functional demands placed on
the posterior teeth. Van Eijden154 reported increases in the longitudinal elastic modulus
(increase in stress per unit of strain) between the molar region and the symphysis. Stress
and strain differences could give rise to the differences in cortical thickness in this
region. Baumgaertel et al149 found that buccal cortical bone is thinnest in the anterior
sextants of both jaws and increases progressively toward the posterior, except distally to
the maxillary second molars, where the buccal cortex average was thin.
Conclusion
Anchorage is one of the key factors that affect the implant success rate in orthodontic
treatment. The traditional anchorage methods are uncomfortable, and usually they can
not provide adequate anchorage because of the anatomical factors of the jaw. the
stability of the implant should have been paid more attention among orthodontics. The
cortical bone is one of the principal factors controlling the stability of mini-implants. The
cortical bone thickness and density should be evaluate together to give complete
information about the quality and quantity of cortical bone. In this study it was found
for cortical bone thickness, there are different changes in the cortical bone between
adults and adolescents, but it was not found gradual changes in the 4 distances from
the alveolar crest . For cortical bone density there are different changes . There is a
gradual increase of density in the apical direction from the alveolar crest except in
palatal female at 8mm. There are significant differences in cortical bone thickness and
density between male and female. Also t There are significant differences in cortical
bone thickness and density between maxilla and mandible.
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