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…………………………………11Fig (2) Microimplants mechanics. Indirect anchorage……………………………………….12Fig (3) Temporary orthodontic mini screw implant design features…………………………..13 Fig (4) Diagram of molar intrusion……………………………………18Fig (5) A,B mesiodistal molar tipping correction with coronary movement………………21 Fig(6) Mesiodistal molar tipping correction with radicular movement…..22Fig (7) microscrew implant anchorage sliding mechanics for treatment of open bite…..23Fig(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)…….27Fig (11) A, B, Distalization with transpalatal bar with absolute anchorage with microimplants and closing coil springs………………………………28Fig (12)Distalization with microimplant in palatal midline or two palatine microimplants and a transpalatal bar, withchain pull……………………………………………………………..28Fig (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

AbstractThe 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 (19-

50 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 mini-implant,

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 peri-

implant 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 mini-

implants 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 the

maximum average of the measured 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 the maximum average of the

measured buccal cortical bone thickness at maxilla was 1.45mm, while minimum

average of the measured cortical bone thickness was 1.22mm. In adolescents the

maximum average of the measured buccal cortical bone thickness at mandible was

1.73mm, while minimum average of 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.

AgeSexArch2mmB4mmB6mmB8mmB2mmP/

L4mmP/

L6mmP/

L8mmP/L

12-18

MalesMaxilla1,381,351,381,371,411,451,441,45Mandible1,511,611,661,781,491,631,731,72

FemalesMaxilla1,231,221,231,241,191,231,301,27Mandible1,671,691,751,701,621,711,831,78

19-50

MalesMaxilla1,481,521,651,721,501,651,731,72Mandible1,431,651,671,721,561,791,791,99

FemaleMaxilla1,281,251,271,271,301,351,311,32Mandible1,471,411,491,471,421,571,651,62

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.

AgeSexArchD

2mmD

4mmBD

6mmBD

8mmBD

2mmP/LD

4mmP/LD

6mmP/LD

8mmP/L

12-18

MalesMaxilla941,221049,781086,811117,48927,691102,801119,561102,71Mandible1246,321311,231373,101422,551341,771421,741454,081461,61

FemalesMaxilla910,03963,481001,171107,52921,781031,691091,451065,04Mandible1212,871283,321355,971403,211320,991390,191412,431411,82

19-50

MalesMaxilla1058,521242,381262,061327,901169,331242,471217,181178,72

Mandible1132,261247,931239,101281,871175,191255,031282,28777,43

FemalesMaxilla969,021025,841048,131096,75941,131013,291034,491043,66

Mandible1053,931086,231140,611189,981168,461242,331237,931310,21

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

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

Age Sex ARCH ACBBTACBP/LTACCBD_ACCP/LD

12-18

MalesMaxilla1,371,441049,541064,25

Mandible1,641,641336,221419,23FemalesMaxilla1,231,24991,271021,88

Mandible1,701,741313,841383,86

19-50

MalesMaxilla1,591,651226,091201,07

Mandible1,621,771225,981252,47FemalesMaxilla 1,261,321042,861004,60

Mandible1,461,561121,691221,63

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 Sex Arch Sextant ATCCBATCCP/LADCCB ADCCP/L 12-18MalesMaxillaRight1.331.401045.101061.65

anterior1.431.471090.021074.47Left1.361.431010.471055.17

MandibleRight1.801.721374.021415.71anterior1.421.581225.741411.83

Left1.721.641421.521431.00femalesMaxillaRight1.281.261031.631015.18

anterior1.201.25990.141032.14Left1.201.21949.201018.05

MandibleRight2..081.861420.641332.32anterior1.381.571182.881417,34

Left1.591.791344.921407,0819-50MalesMaxillaRight1.511.621242.231271,97

anterior1.531.671236.891186.40Left1.761.651194.431139,64

mandibleRight1.761.801225.701265.83

anterior1.501.721250.981279.88Left1,581.791195.101201.52

femalesMaxillaRight1.251.301107.15989.63anterior1.231.31989.271088.03

Left1.331.351039.10920.11MandibleRight1.621.611224,721273.98

anterior1.201.451017.791215.20Left1.611.661137.391176.64

Table V- t test between maxilla and mandible.

Then the t test was used to compare the two groups of age, the adolescents (Ages 12-

18) 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 19-50ySig.Difference between meansDifference standard error

medie_sitiVmmV,336,-03308,03436

medie_sitiVmmp,001,-10845,03267

medie_sitiVDmmv,894-3,2598924,40519

medie_sitiVDmmp,48317,5070524,94965

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

Male vs femaleSig.Difference between

meansDifference standard error

maxilla VS mandible

Sig.Difference between

meansDifference standard error

medie_sitiVmmV SPESSORE,000,-28576,03118

medie_sitiVmmp SPESSORE,013,-30988,02925

medie_siti V DENSITA VESTIBOLARE,000-215,6686921,91451

medie_sitiV DENSITA PALATALE,027-281,8457121,12007

medie_sitiVmmV,000,21267,03210

medie_sitiVmmp,000,22437,03049

medie_sitiVDmmv,000153,7459722,74124

medie_sitiVDmmp,000156,0278823,24064

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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