Osteogenesis Distraction Part 2

1. Osteogene esis sis Part (2) Part (2) Prepared by: Prepared by: Dr. Mohammed Alruby. Mohammed Alruby. Distraction Distraction Osteogen Dr. Osteogenesis Distraction Osteogenesis Distraction Part 2 Part 2 Dr. Mohammed Alruby Dr. Mohammed Alruby

2. 2 Mandibular distraction osteogensis Introduction Pre-surgical orthodontic preparation Planning of mandibular distraction Extra-oral mandibular distraction osteogensis Mandibular lengthening using intra-oral distractor Bone transport Alveolar distraction Periodontal ligament distraction Rapid canine retraction using distraction of periodontal ligament Osteogenesis Distraction Part 2 Osteogenesis Distraction Part 2 Dr. Mohammed Alruby Dr. Mohammed Alruby

3. Mandibular distraction Osteogenesis Introduction Treatment planning for pt undergoing distraction osteogensis must consider all issues related to surgical correction, as well as the potential for future skeletal growth and the need for over correction, and possible future operation. Several specific distractions related decisions must be made during treatment planning include osteotomy design and location, selection of distraction device, determination of the distraction vector. **Distraction device selection: Craniofacial distraction devices have been developed for both internal and external appliances. = External distraction devices: Are placed using transcutaneous pins, offer excellent control for bone segment movement, available in longer length and they much easier to place, maintain and simpler to replace during distraction if necessary or to remove after completion of lengthening. But may lead to skin scaring and poor acceptance by pt. =Internal distraction devices: They may be tooth born, bone born or both. Internal devices neither produce facial scaring nor have the negative psychological impact of the external devices. But it is difficult to place, have a higher risk of injury to nerve and other anatomic structures, and a second surgical procedure to often necessary to remove the device following completion of consolidation. ** Distraction vector planning: The distraction vector defines the desired direction that the segment of bone must move during lengthening. With regarding to the vector of distraction there is some factors that affect it as, distraction device orientation and occlusal interference. 1—Distraction device orientation: If antro-posterior advancement of the mandibular corpus is desired, placement of the distraction device parallel to occlusal plane is recommended. Oblique distraction device orientation simultaneous vertical and horizontal movements of the bone segments. When oblique design is chosen, antroposterior positional changes occur along with hyperdivergance of the mandible, resulting in clockwise rotation and anterior opening of the bite that useful in case of deep bite. 2-Occlusal interference: One of the most important factor that affect the vector of distraction as in cases of posterior occlusal interference and the pt need corpus length this can lead to clock wise rotation of the mandible and anterior open bite. Pre-surgical orthodontic preparation: - After completion comprehensive treatment planning pre-distraction orthodontic /or orthopedic preparation is commenced, the teeth should move to near ideal position relative to basal bone. Dental mal-relation must be eliminated in order to prevent mechanical interference with the movement of the distal tooth bearing segment as, maxillary incisors that may retroclined in some cases need to be corrected to allow good mandibular advancement movement. The patient with sever retro-gnathia may have a transverse deficiency in maxilla, it is appropriate to expand the maxilla either prior to or during distraction to accommodate the width of advancing mandible. 3 Osteogenesis Distraction Part 2 Osteogenesis Distraction Part 2 Dr. Mohammed Alruby Dr. Mohammed Alruby

4. Another component of pre-distraction orthodontic treatment is the insertions of stabilized heavy arch to: 1- Allow vector control during distraction. 2- maintain the mediolateral relationship of the arch, the distal segment cannot displace laterally Planning of mandibular distraction: - Distraction osteogensis is an effective method of mandibular lengthening and correction of deformities of the craniofacial skeleton. Due to the anatomic complexity of the mandible, it is essential to accurately evaluate the deformity and form a definitive treatment plane preoperatively. Panoramic and cephalometric radiographs are used to evaluate the deformity and plane the three dimensional correction of the mandible with distraction. Three-dimensional computed tomography (C T) scans of skull and mandibular models are helpful to evaluate the exact type and severity of the deformity. Patient evaluation: 1- Medical history: Prior to clinical and radiographic examination, a complete medical history is analyzed to allow identification if other organ in the body is affected or not and whether a particular syndrome is present or not. 2-Clinical examination: The entire head organ is examined from different views. This should include analysis of general osseous contours for deformities and external facial features for facial asymmetry. Lateral nasal, chin, and forehead projection, as well as, the position of the mandibular angle and the size of zygomas, are examined, with comparison of both sides. The difference in mandibular and maxillary size between the right and left sides is evaluated by inserting tongue depressor between the teeth and comparing the occlusal plane cant with the line cross the eye brow or between the medial canthi. The extent of jaw opening is measured between the maxillary and mandibular incisors, the associated congenital anomalies are evaluated by examined the size and function of the muscles of mastication and testing the function of the facial nerve. The pt should observed from the frontal position to determine forehead, orbital, and zygoma and external ear relationship. The quality and thickness of soft tissue were also observed. The intraoral examination includes: occlusal plane cant, molar relationship, and the presence of cross bite, TMJ evaluation and mandibular functional movements are assessed, this include lateral excursion, maximum opening and protrusion. 3- Anterior-posterior cephalometric radiograph: On the Antroposterior cephalometric radiograph, a horizontal line (HL) is drawn between the linea innomenata (LI) and crista galli point (CP), horizontal asymmetry is analyzed by drawing a vertical line (VL) perpendicular to (HL) in the center of the face at CP. Inter-cuspal point (IC) is marked half the distance between the canine root apices. Drawing the intergonial line (IGL) or the occlusal plane (OP) analyzes vertical asymmetry. The angle between the IGL and HL indicated the vertical skeletal asymmetry. The ramus height is measured from condylon to gonion. The maxillary size is identified as the distance between the infera-orbital point (IO) at the center of inferior dental margin and (OP). 4 Osteogenesis Distraction Part 2 Osteogenesis Distraction Part 2 Dr. Mohammed Alruby Dr. Mohammed Alruby

5. 4- Lateral cephalometric radiograph: On the lateral cephalometric radiograph, the outline of the mandibular inferior border is marked for both sides, indicating the difference in size between the left and right halves of the mandible. The ramus height, body length and the gonial angle are measured. 5- Three-dimensional CT scans: Three-dimensional CT scans are taken at chin and the condylar heads. On the frontal views, the relationship between the mandible and the rest of the craniofacial skeleton is evaluated. On the lateral views, the posterior surface is marked and Gonion is identified at the edge of the mandible. The ramus height (CO-GO) and the body length (GO –PO) are measured for both sides of the mandible from Gonion to the most posterior point of the superior surface of the condylar head and the most anterior prominence of the mandible and compared with normal parameters. 6- Treatment planning: = Direction of distraction: The direction of distraction and the distraction device are determined based on the identified type of deformity and the positional changes, for example: if only unilateral ramus lengthening is required, the distractor is positioned parallel to the ramus of the mandible. If only unilateral corpus lengthening is required, the distractor is placed parallel to the corpus of the mandible but in cases with simultaneous ramus and corpus lengthening, the distractor may be placed according to this formula: Pin placement angle = 180 – gonial angle x ramus deficiency / total deficiency Where pin placement angle = the angle between the distraction vector and the mandibular plane. Amount of distraction can be calculated using a formula: = Dc + Dr-2 (Dc +Dr) x cos a Where: a = gonial angle Dc = corpus deficiency. Dr = ramus deficiency. The position of pin placement will determine the distraction vector. The distraction vector is different in each pt according to the grade of mandibular hyperplasia. N.B: there is a normal value for the, length of corpus and ramus of the mandible Classification of mandibular regenerate bone = Currently, calculation of the distraction, consolidation index, clinical evaluation, and plain film radiographs are the standard methods in limb lengthening for determining the appropriate time for distraction regenerate mineralization and remodeling prior to device removal. However, these methods have several limitations when used to craniofacial bones, clinical testing includes disconnection of the distraction device followed by manually stressing the bone to evaluate regenerate stiffness and bone segment mobility. This however, may be difficult or impossible to perform on most craniofacial bones. Plain film radiographic imaging in the craniofacial region is also more difficult than the long bones due to the frequent superimposition of adjacent bony structures or device fixation elements. Therefor the following is the radiographic classification of mandibular distraction regenerate based on 5 Osteogenesis Distraction Part 2 Osteogenesis Distraction Part 2 Dr. Mohammed Alruby Dr. Mohammed Alruby

6. qualitative description of the distraction bone formed during experimental bilateral lengthening of the mandible **Classification of mandibular hyperplasia: (Pruzansky grade) Grade 1: hypoplasia affects only the gonial angle. Grade 2A: the angle and ascending ramus is affected. Grade 2B: hypoplasia is more severe and affects the angle and ascending ramus, the later having a flat rudimentary condyle. Grade 3: complete absence of ramus and condyle (mandibular distraction is not indicated as a primary surgical procedure). = In patient with grade 1: The Corticotomy extends obliquely from the posterior edge of the hypoplastic gonial angle to the retro-molar area. The pins must be placed perpendicular to the Corticotomy to obtain an oblique distraction vector that produce larger bone elongation at the angle and less bone elongation in the retro molar area. = In patient with grade 2A: the distraction process elongates the angle and inferior portion of the ascending ramus, therefore the Corticotomy is placed obliquely to the junction of the angle and ramus. = In patient with grade 2B: The Corticotomy is placed horizontally at the base of the ascending ramus and the pins must follow a vertical distraction vector in order to obtain more elongation of the hypoplastic ascending ramus. Extraoral mandibular distraction osteogensis In most mandibular hypoplasia’s, all three dimensions (vertical, horizontal, and transverse) demonstrate varying degree of deficiency. ==Unidirectional device: With the use of unidirectional distraction device, mandibular lengthening was possible in one direction only. It is the first type used for mandibular osteo-distraction that successfully used for mandibular lengthening in pt with mandibular deficiency requiring distraction in primarily one direction, particularly when there was not enough host bone available to apply a BI- directional device. == Bi- directional distraction: The limitation of the unidirectional distraction device was obvious when considering the three dimensionally deficient mandible. Major limitation included difficulty predicting the direction of bone segment movement and inability to change this direction after initiating distraction. Distraction of the mandible in one direction cannot full file the functional and occlusal needs of the pt with malocclusion to allow two directions of movement which clinically required in pt bilateral micrognathia disorder and sever mandibular hypoplasia. ==Multidirectional distraction: Bi- directional appliances improved the control of bone segment and allowed angular manipulation at the gonial angle. However, when two osteotomies are performed on the mandible, the available bone stock is often limited and the risk of the tooth root damage increase. In addition, the intervening segment is prone to a vascular necrosis. In order to overcome the limitation of BI- directional device, the multidirectional device was developed the specific advantage of mandibular 6 Osteogenesis Distraction Part 2 Osteogenesis Distraction Part 2 Dr. Mohammed Alruby Dr. Mohammed Alruby

7. distraction using multidirectional device to accommodate any shape of the deficient mandible. Application of the device to the mandible with only two pin sites, using single osteotomy and contouring the regenerate during distraction while achieving the desired length and shape of the mandible. **Classification of craniofacial microsomia severity: Type I: (minimal hypoplasia): the temporo-mandibular joint and ramus are well formed but reduced in size compared with the contralateral side. Type II: TMJ, ramus, and glenoid fossa are hypoplastic and malposed, this class has been further divided into: II A: in which the deformed joint is positioned such that the mandible can be symmetrically opened, and II B: in which the deformed joint is malposed inferiorly, medially and anteriorly. Type III: TMJ, ramus and glenoid fossa are absent. Mandibular lengthening using intraoral distractors: Before the correction of mandibular ramus or corpus hypoplasia, the clinician must decide whether the existing deformity can best be connected with a functional appliance, conventional orthognathic surgery or distraction osteogenesis, the severity of the deformity and the pt. age are the primary criteria by which this decision should be based. Minor deformity cases can be treated successfully with functional appliance prior to puberty, and if necessary with orthognathic surgery, after puberty. These type of cases can be characterized by mandibular deficiency with an overjet of less than 6 mm or microsomia of Pruzansky grade 1. Distraction osteogensis is indicated when the overjet is greater than 7mm to 8mm, or Pruzansky grade 2A, 2B or certain cases of Pruzansky grade 3, although usually the total absence of bone stock in grade 3 does not allow the distraction technique because a primary bone graft must be performed first. Mandibular symphyseal widening by distraction: - Distraction osteogensis is a treatment alternative when transverse mandibular deficiency is too large for conventional orthodontic or surgical treatment. The goal for symphyseal distraction is to create new bone and soft tissue and allow good adaptation of the surrounding tissue to this area. The distraction osteogensis is indicated when it is necessary to significantly alter the mandibular arch form and the treatment requirements exceeds the possibilities of the conventional orthodontic or surgical treatment (> 4mm). This may include an increase of the mandibular width to compensate for arch length indecency, crowded anterior teeth or absolute bone deficiency. Pre distraction orthodontics: The aim of the pre distraction orthodontics is to remove any occlusal interference that might occur during and after distraction. This enhances stability and makes the post distraction orthodontic easier. The narrow mandible is often associated with a narrow maxilla; therefore, it is essential to treat this maxillary transverse deficiency prior to performing symphyseal distraction. 7 Osteogenesis Distraction Part 2 Osteogenesis Distraction Part 2 Dr. Mohammed Alruby Dr. Mohammed Alruby

8. Some intraoral distractors: - 1- Clinical application of ROD intraoral custom distraction device: - The ROD devices are intraoral, custom- made distraction devices pre- programmed along a desired vector of distraction, and there are five categories of ROD devices: ROD 1: Tooth born intraoral distraction device is indicated mainly in cases involving mandibular retroganthia with lower incisor compensation (proclination is greater than 110 degree to the mandibular plane or crowding than 8 mm). In these cases, interdental distraction provides the optimal mandibular advancement while simultaneously creating space for crowding resolution. There by eliminating the need for per– surgical extraction or orthodontics. ROD 2: Hybrid intraoral distraction device is indicated in cases with mandibular retrognathic without lower anterior crowding (proclination is less than 100 degree to the mandibular plane, crowding less than 6 mm). Used for distraction posterior to mandibular dentition. There is some modification that contain hinge which allows vertical molding of the callus and this enable the clinician to auto rotate the mandible during distraction to close the open bite after attaining the required amount of antro-posterior advancement of the mandible. (Correction of skeletal deficiency) ROD 3: (Tooth born) used to widen the mandibular symphysis for resolution of lower anterior crowding in cases with significant anterior mandibular arch constriction. ROD 4: (hyprid) used to widen and advance the maxilla for correction of transverse and anteroposterior deficiency. ROD:5 Used for alveolar ridge distraction to generate bone for dentoalveolar implant placement. Device fabrication: After any pre- distraction orthodontic treatment has been completed preformed st.st. crown is placed on the teeth preferably two teeth away from the osteotomy side. Typically, crown is fitted on the second molar and first premolar, rubber base impression material was taken then the fitted crown is transferred to the impression, crown is secured in position and the impression is poured by using heat resistant dental stone, the distraction device is adjusted and soldered on the crown of the model, and then try in before osteotomy in the oral cavity to determine its vector. 2-Multiaxis intra oral distraction of the mandible: It is an intraoral distractor that allows distraction in more than one axis, it is easily adaptable and allow minimally invasive placement. The requirements of the intraoral distractor that designed were: 1-Provide horizontal and vertical distraction. 2-Should allow gradual angular changes between the horizontal and vertical axis, which would enable precise occlusal management during distraction. 3-The entire bone born distractor should be located within the oral cavity, with the fixation plates and screws placed trans-mucsally. 4-The distractor should be modular so that it can be removed and reattached to the fixation plates 8 Osteogenesis Distraction Part 2 Osteogenesis Distraction Part 2 Dr. Mohammed Alruby Dr. Mohammed Alruby

9. during surgery, 3- A new spiral distractor for mandibular osteo-distraction: Although mandibular distraction has been performed in adults, most mandibular distraction procedures are performed on growing pt. therefore growth potential must be considered when performing osteo-distraction, several authors suggest that the mandible grow in an archial fashion. During growth, eruption of posterior teeth occurs, thereby maintaining the occlusion while advancing the chin anteriorly. Most of the distractors have a linear effect, which may adequately lengthen the bone, nonlinear distraction may be required in most cases when considering the small curvilinear anatomy of the craniofacial bone. This may particularly important for the maxilla and mandible when distraction may alter occlusal relationships, as in some cases open bite may developed after distraction. From the above this led to developed of distractor with a curvilinear distraction vector. Initially, all bony anatomic structures are traced, then the position of the mandibular osteotomy site is marked on the tracing. Generally, this is posterior to the most distal tooth and pass through the gonial angle region, if more vertical movement is desired then the osteotomy is performed slightly above the gonial angle whereas the osteotomy is performed anterior to the gonial angle if more antro- posterior movement is desired. Bone transport Bone transport is a distraction osteogensis technique that involves the slow movement of a free segment of bone (transport segment) across an osseous defect that developed as a result of severe congenital deformity, trauma. Following gradual advancement of the transport segment, new bone tissue forms behind the moving segment, thereby filling the defect with new bone. After completion of bone transport, compression force is applied between the transport and target bone segments to produce fusion at the docking site. Several bone transport techniques have been developed and according to Iliazarove, the techniques are divided into three groups based on the number of distraction / compression sites, mono-focal, bifocal, trifocal and defined based on the type of force that is applied between the bone segment compression or distraction. 1-Monofocal osteo-synthesis: Is used primarily in cases with small osseous defects of up to several millimeters, where healing between the segment of bone is abnormal resulting in non-union. In cases not requiring an increase in limb length, compression forces are applied and the pathologic tissue undergoes reparative remodeling, which result in reparative callus formation and fusion of the two ends and this termed mono-focal osteo-synthesis. 2-Bifocal osteo-synthesis: For large bone defects (one compression and one distraction site), the free bone segment (transport segment or transport disk) is created from one of the residual segments. This transport disk is then moved from the residual bone host segment through the defect toward the residual target bone segment. During movement of the transport disk, new bone (distraction regenerate) is formed 9 Osteogenesis Distraction Part 2 Osteogenesis Distraction Part 2 Dr. Mohammed Alruby Dr. Mohammed Alruby

10. between the residual bone host segment and the transport disk. Once the transport disk reaches the residual target bone segment, compression force are applied at the docking site. At this docking site, the compression forces stimulate gradual fusion of the contacting bone margins into solid regenerate bone. 3-Trifocal distraction – compression osteo-synthesis: In cases of large bone defect, two-transport disk can be centripetal toward each other so that they meet with center of the defect. Biologic foundation: Biologically, bone transport techniques are based on two separate process, distraction osteogensis and transformational osteogensis. Distraction osteogensis is a biologic process of new bone formation between the surface of bone segments that are gradually separated by incremental traction. Transformational osteogensis is a mechanically induced biologic process of pathologic bony tissue transformation into normal bone. In cases with either atrophic non-union or reduced bone surface area, Transformational osteogensis can be induced by compression force. This lead to local necrosis of the pathologic tissue followed by new vascularization of fibrous tissue and cartilaginous tissue with local resorption at the bony ends, resulting in progressive remodeling and fusion of two bony segments. Importantly, these two processes occur simultaneously during bifocal bone transport. Distraction osteogensis occur between the surface residual bone host segment and the tailing edge of the transport segment, while transformational osteogensis occur between the leading edges of the transport segment on the residual target bone segment. Canio-facial bone transport: Costantino and co-workers performed the first clinical application of this technique to the craniofacial skeleton in 1990 and 1995 respectively. Recently, various types of growth factors have been applied in hopes of accelerating distraction regenerate bone formation and bone segment fusion at the docking site as: Raschke and coworkers observed increase stiffness of the regenerate after administration of growth hormone derivatives. Others demonstrate enhancement of callus maturation at docking site after injection of types I collagen mixed with marrow-derived mesenchymal stem cell. Mayer and Shimazaki demonstrate acceleration of formation and maturation of the regenerate bone by low intensity ultrasound. Alveolar distraction As the age of the population continues to increase, more patients suffer from alveolar ridge atrophy due to developmental anomalies, traumatic tooth loss and periodontal disease. Although several surgical approaches such as autogenous bone grafting, alloplastic augmentation and guided tissue regeneration were developed to manage these abnormalities, each of them has certain limitation in cases with severe alveolar bone defects and deformities. Distraction osteogensis offer the possibility of enhancing the shape, mass and mechanical strength of the alveolar bone in these cases by promoting new bone formation in a rapid and predictable 10 Osteogenesis Distraction Part 2 Osteogenesis Distraction Part 2 Dr. Mohammed Alruby Dr. Mohammed Alruby

11. manner prior to implant or fixed partial denture placement. Since the experimental validation by Block and co-workers and the initial clinical application by Chine and Tooth, the use of this technique for vertical alveolar reconstruction has increased tremendously. Different types of intraoral devices were designed to increase height of the alveolar bone. They include extra-osseous distractor placed on the lateral side of the bone, endo-osseous distractors inserted into the bone segments and distractor implant. Indication: Severe atrophy of the edentulous ridge requiring an increase in vertical bone height for placement of endosseous implant (at least 8mm of bone is necessary in order to place a small implant). osseous defect of the edentulous ridge, which require a height increase to improve the crown- root ratio, thereby reducing the risk of prosthesis overload Narrow alveolar ridge with normal height, but requiring increased width in a buccolingual direction for correct placement of an endosseus implant. Horizontal rather than vertical bone distraction is used in this situation to augment the alveolar ridge. Gradual vertical translation of an ankylosed tooth /or teeth when orthodontic tooth movement is not possible. Gradual vertical translation of an Osseo integrated implant with its surrounding alveolar bone. Alveolar ridge osteo-distraction may be indicated for the atrophic alveolar process resulting from periodontal disease, trauma or congenital deformity. This technique may also be applied to alveolar defects caused by marginal bone resection of a tumor or fenestration of cyst. Orthodontic indications include a local open bite caused by vertical malposition of tooth segment. Alveolar ridge distraction is contraindicated, however for severely atrophic mandible, and for patient with severe osteoporosis or extremely advanced age, since there is a greater risk of fracture As well as space limitation for device placement. As a result of bone transport, the alveolar ridge moved both coronally and labially. Distraction resulted in increased height and width of bone at the implant placement site, the bone adjacent to the natural teeth was widened during distraction as well, potentially improving their resistant to future bone loss. Some devices for alveolar distraction: TRACK 1.5(tissue regeneration by alveolar callus distraction -Koln) distraction device. This device is suitable for distracting large areas of alveolar process more than 3cm in width and contraindicated in cases of insufficient bone volume (vertical height less than 8mm) where the severely resorbed mandible has the potential to fracture in radiated patient, osteoporosis and general systemic disease. Modified TRACK 1.0 distraction device: Are suitable for distracting smaller alveolar segments, it is particularly indicated for partial defects of alveolar process or atrophy of smaller alveolar process areas. Modified TRACK 2.3 distraction device: Is suitable for distracting larger alveolar process segments in a considerably atrophic mandible as severely resorbed mandible or mandibles with inherent danger of fracture. ROD 5 distraction device: Demonstrated to increase the height and width of alveolar bone in case that has not sufficient 11 1- 2- 3- 4- 5- 1- 2- 3- 4- Osteogenesis Distraction Part 2 Osteogenesis Distraction Part 2 Dr. Mohammed Alruby Dr. Mohammed Alruby

12. alveolar bone for placement of implant. Distraction implants are suitable for increasing the height of anterior mandibular and maxillary alveolar ridge. The surgical technique combines a surgical osteotomy with the insertion of self- cutting conical screw implants. Alveolar ridge distraction should be started 1 week after surgery and performed slowly at a rate of 0.5mm / day divided in two or more measurements. At the end of distraction period, the distractor is transformed into a combined screw and cylinder implant. Osteo- integration of the implant occurs by 4 months. After this period, the implant can be loaded with a prosthesis, which improves the condition of the gingiva as well as dental aesthetics. The main advantage of using distraction implant is the single step surgical technique, which minimize trauma to periosteum and bone and allows transforming of the distractor into a dental implant without removal and insertion. Because of the small dimensions of the distraction implant, no inter-occlusal interference is observed and distraction can be performed in the upper and lower jaws simultaneously. = Many severe cases of cleft lip and palate require a secondary alveolar bone graft to provide reliable bony support, ensure a satisfactory height of the mucosal level on the clefted alveolar process, and avoid the prosthetic and aesthetic problem due to long abutment. In some cases, the bone volume after graft is not enough to insert implant so the use of distraction implant of the previously grafted bone segment solves this problem. Periodontal ligament distraction Although the art and science of orthodontic have progressed significantly over the past 100 years, relatively little has been done to enhance the rate at which tooth movement occur. Recently however, many methods have been proposed to enhance the rate of tooth movements. These methods include the injection of biologically active peptides, the use of magnets and even the application of electric current. Unfortunately, these techniques have produced inconsistent results, another technique have recently been introduced that demonstrates intriguing possibilities. A modification of the distraction osteogensis technique, whereby the interdental bone is undermined after tooth extraction has been shown to produce rapid tooth movement with minimal complication Rapid canine retraction using distraction of periodontal ligament: - In1876 Farrar reported use of special screw utilized to retract the canine into the space left after extraction of the first premolar, the screw was activated every morning and evening (0.42mm /day) for an average 46 days with no associated pain. During this time Farrar reported that there was no movement in posterior segment that suggesting no anchorage loss occurred. But he reported some complications associated with this technique including alveolar bone fracture, pulpal necrosis leading to abscess formation with subsequent tooth discoloration. In 1887 Angle developed a retraction screw to move the canine distally after extraction of 1st premolar and still use until Angle introduction of the edge wise appliance. A force applied to a tooth to be moved, resulting in periodontal ligament (PDL) compression on one side of the tooth and tension on the other side. During this process, the periodontal collagen fibers and blood vessels are stretched on the tension side and fibroblast appears oriented in the direction of 12 Osteogenesis Distraction Part 2 Osteogenesis Distraction Part 2 Dr. Mohammed Alruby Dr. Mohammed Alruby

13. stretching. Thereby forming long bony trabeculae horizontally and parallel to the path of tooth movement. This process has been described as Orthodontically induced PDL osteogensis. The limitations in rate of tooth movement are most likely related to characteristics of alveolar bone and tissue of PDL Factor affecting the rate of orthodontic tooth movement: Strength of periodontal ligament, that is higher in first week than second week. Patient age, it will know that tooth movement occur faster in adolescents than in adults, this related to decrease physiologic cellular activity in adults’ periodontal tissue. Resistance of alveolar bone limits the rate of tooth movements, for example in alveolar bone with loose trabeculae provide less resistance so tooth movement occur faster than through normal bone. Therefore, reduction of bony resistance on the compression side of the tooth will diminish physical alveolar bone contact, thereby minimizing undermining resorption and accelerating the rate of orthodontic tooth movement. One of the recent techniques for accelerating tooth movement is interdental distraction osteogensis followed by orthodontic tooth movement with the rate of 1.2 mm /week in mandible and 3.5 mm / week in maxilla. Biologically the rapid canine retraction is based on the principle of bifocal bone transport used on long bone and PDL on the tension side during tooth movement, the mechanical forces induces osteoid deposition and alveolar bone mineralization arranging the newly formed bony trabeculae parallel to the path of tooth movement. Technique: Firstly, the rapid canine retraction is indicated in cases that need short treatment and maximum anchorage control. Pre-surgical orthodontics: The anchor unite are the 1st molar and 2nd premolar bilaterally, in maximum anchorage cases make leveling only at the anterior segment from 1st premolar to 1st premolar, with no active appliance placed on the anchor unite. This allows start of cellular activity on the anterior segment PDL and not on the anchor unite that facilitate movement during distraction. But in cases of moderate anchorage (where anchor control is not critical), nickel-titanium wires are placed on all teeth simultaneously to stimulate the PDL on the anchorage unite at the same time that allows the anchorage unite to move mesially and canine to distracted distally. Surgery: = Immediately after 1st premolar extraction, the interseptal bone distal to the canine is undermined and reduced in thickness. Because the 1st premolar socket depth is always less than that of the canine, the bone located distal to canine root apex would resist tooth movement during distraction. Therefore, the 1st premolar extraction socket must be extended to the same depth as the canine socket using round carbide bur. The bur is held parallel to the long axis of the canine, the interseptal bone is reduced to a thickness 1 to 1.5 mm. A preapical film is taken to ensure that the socket has been adequately deepened and the interseptal bone sufficiently reduced. = The final step is to undermine the margins of the interseptal bone distal to the canine so that it can be broken during distraction. This occurs by make two vertical grooves from inferior to the superior 13 1- 2- 3- Osteogenesis Distraction Part 2 Osteogenesis Distraction Part 2 Dr. Mohammed Alruby Dr. Mohammed Alruby

14. aspect of the socket on both the mesiobuccal and mesiolingual line angle of the extraction socket. The two grooves are connected at its base. = Activation of the canine retraction / distraction device is begun the day of insertion and continues until the canines have been distracted into the desired position. It is activated (0.35mm / turn) twice / day. Once on the morning and once at the night, this because the maximum cell proliferation in the PDL occurs late in the evening and early in the morning. = Patients are monitored once a week during distraction produce to ensure that the desired movement is occurring. Results: clinical finding: Minimal root resorption has been seen in the distracted canines. The buccal gingiva recedes about 1mm in some cases, however, it appear to regain its original height within a few months. The width of keratinized gingiva, pocket depth, gingival height and attachment level remains the same 5 months after distraction. No detrimental effect to the periodontal apparatus of the canine. No distracted tooth has had crown discoloration or any signs of pulpal necrosis. 2- Radiographic stages for rapid canine distraction: Stage (1): first week of distraction, stretched PDL is observed with no radiographic evidence of bone formation. Stage (2): from the second week to the end of distraction. Actively growing bony trabeculae in the distracted PDL are evident radiographically. Stage (3): from the end of distraction to 4 week of consolidation. This period is characterized by recovery of the PDL, during this time the distracted PDL decrease in size, gradually reaching pre-distraction dimensions. The radiographic appearance of the bone is similar to that of the cortical bone or to a thickened lamina dura. Stage (4): from the fourth to twelfth week of consolidation, remolding of the newly formed regenerate bone occurs. Stage (5): after 12 week of consolidation maturation of the regenerate bone is completed and the lamina dura reaches its normal thickness. Radiographically, the inter-septal bone between the lateral incisors and the canine is indistinguishable from the undistracted sites. Biologic response of PDL to rapid distraction: Several histologic studies revealed that, immediately after applications of the traction force, initial tension accumulate in PDL, activating fibroblast located on the stretched collagen fibers. The tension then transmitted through the collagen bundles network into the sharpey’s fibers located at both the alveolar bone and cementum, thereby activating the osteoblast and Cementoblast. At the host alveolar bone and along the surface of the fibrous tissue, the activated osteoblast produces osteoid, which then mineralized. The activated Cementoblast produce more cementum on the surface of the host cementum layer thereby reinforcing its anchorage to the sharpey’s fibers. 14 1- - - - - - Osteogenesis Distraction Part 2 Osteogenesis Distraction Part 2 Dr. Mohammed Alruby Dr. Mohammed Alruby

15. Tooth tipping: Although the canine root is parallel to the long axis of the second premolar, the tooth tends to tip distally during retraction. In adult patients, the amount of canine tipping during rapid distraction was approximately 7 degree. This angulation is associated with the position of the distraction device and the overall length of the tooth. Ideally the distraction device should be located as close to the canine center of resistance as possible in order to reduce tipping of canine. Influence of patient age: Although principles of canine distraction are the same for adolescent and adults, some clinical differences were observed. For example, the amount of maxillary canine movement during the first week of distraction was less in adult patient than adolescent. But no differences were seen during second and third weeks. Root resorption: If the canine is not retracted into the extraction socket within the first 3 weeks, the rate of tooth movement slows, root resorption increases, and the anchorage units start to move forward. A correlation between root resorption and the duration of treatment has been reported, interestingly the duration of time over which the force is applied to appear to be more critical than the magnitude of this force. With my best wishes ---- thanks 15 Osteogenesis Distraction Part 2 Osteogenesis Distraction Part 2 Dr. Mohammed Alruby Dr. Mohammed Alruby