Distraction osteogenesis: the effects of orthodontic tooth movement on distracted mandibular bone

The application of distraction osteogenesis in craniomaxillofacial surgery has created new treatment methods for patients with craniofacial skeletal dysplasias. Most of the applications in the craniofacial skeleton have been for the correction of severe congenital or acquired conditions. As more understanding is gained with these new approaches, refinements in techniques will enhance treatment planning and outcome. This will expand the application of distraction osteogenesis to more common, less severe types of skeletal dysplasias. One of the important areas in mandibular distraction osteogenesis is the management of the dental gap created when distraction is applied within the tooth-bearing segment of the mandibular body. In this study, the authors investigated the effects of orthodontic tooth movement into new bone created through the process of distraction osteogenesis. Orthodontic tooth movement through newly formed mandibular bone in the canine model was performed and, through histologic studies, was found to create compact bone along the path of the moving tooth. This compact bone replaced the more unstructured woven bone that was originally created by the process of mandibular distraction osteogenesis. These findings indicate that orthodontic tooth movement can be performed in distracted bone and can have significant influence on the stability and long-term structural preservation of the bone created by distraction osteogenesis within the tooth-bearing segment of the mandible.     

Treatment planning and biomechanics of distraction osteogenesis from an orthodontic perspective

As in traditional combined surgical and orthodontic procedures, the orthodontisthas a role in the planning and orthodontic support of patients undergoing distraction osteogenesis. This role includes predistraction assessment of the craniofacial skeleton and occlusal function in addition to planning both the predistraction and postdistraction orthodontic care. Based on careful clinical evaluation, dental study models, photographic analysis, cephalometric evaluation, and evaluation of three-dimensional computed tomographic scans, the orthodontist, in collaboration with the surgeon, plans distraction device placement and the predicted vectors of distraction. Both surgeon and orthodontist closely monitor the patient during the active distraction phase, using intermaxillary elastic traction, sometimes combined with guide planes, bite plates, and stabilization arches, to mold the newly formed bone (regenerate) while optimizing the developing occlusion. Postdistraction change caused by relapse is minimal. Growth after mandibular distraction is variable and appears to be dependent on the genetic program of the native bone and the surrounding soft tissue matrix. A significant advantage of distraction osteogenesis is the gradual lengthening of the soft tissues and surrounding functional spaces. Distraction osteogenesis can be applied at an earlier age than traditional orthognathic surgery because the technique is relatively simple and bone grafts are not required for augmentation of the hypoplastic craniofacial skeleton. In this new technique, the surgeon and the orthodontist have become collaborators in a process that gradually alters the magnitude and direction of craniofacial growth.     

Distraction osteogenesis in an anterior mandibular bone defect utilizing lingual periosteal release: a case report

This clinical report presents a modified distraction technique to achieve height in the vector of distraction. The success of distraction osteogenesis depends on both biologic and biomechanical factors. The focus in this case is on correcting the direction of distraction; incorrect distraction direction is a frequent complication associated with distraction osteogenesis in the mandible. A 21-year-old man presented with a 10-mm vertical bone defect in the anterior mandible caused by facial trauma. The treatment chosen was distraction osteogenesis. After osteotomizing a bone segment and slitting the lingual periosteum, the bone segment was advanced anteriorly 4 mm and an extra-alveolar distraction device was applied. This approach allows the distraction device to be placed vertically, thus preventing lingual shift. The newly created alveolar ridge fully met prosthodontic requirements for a predictable outcome.     

Proximal segment displacement in mandibular distraction osteogenesis

Distraction osteogenesis has been advocated for treatment of the mandibular deformity in patients with hemifacial microsomia (HFM). During the active phase, the force of distraction pushes the distal segment of the mandible down, creating a distraction gap. Because of the abnormal temporomandibular joint anatomy in HFM patients, the proximal segment may not seat in the glenoid fossa and thus may be displaced with distraction. The purpose of this study was to determine the vector(s) of proximal segment movement during mandibular distraction using a semiburied device. Two investigators traced the immediate pre-and postdistraction panoramic radiographs of 12 HFM patients (mean age at operation = 8.4 years, mean distraction = 28 mm) who had mandibular distraction with a semiburied device. Radiographic analysis, based on a vertical maxillary reference line, measured change in condylar position with angular and linear measurements. Inter-rater reliability for the tracing and analysis was shown with a correlation coefficient between 0.89 and 0.99 for all measures. Based on the angular and linear measurements, 10 of the 12 patients had superior movement of the proximal segment with distraction. Sagittal movement of the proximal segment could not be judged adequately. This study was based on measurements made on panoramic radiographs. Direct measurements could not be made; thus, it was not possible to estimate proximal segment movement in millimeters or as a percentage of total movement. Further studies to document proximal segment movement using computed tomography scans may provide more quantitative data.     

Intraoral distraction osteogenesis of the mandible in hemifacial microsomia.

PURPOSE: Lengthening of the mandible by distraction osteogenesis is the preferred method for treatment of hemifacial microsomia in children. Use of an intraoral distraction technique and horizontal oblique ramus osteotomy in such patients is presented. PATIENTS AND METHODS: Mandibular ramus lengthening was performed in 11 patients aged 6 to 12 years with hemifacial microsomia. During the age of mixed dentition in hemifacial microsomia patients with a hypoplastic mandible, the unerupted molars buds are located high in the retromolar region and are in danger of being damaged by the osteotomy. Therefore, an intraoral approach exposing the mandibular ramus and angle was performed, and a horizontal oblique ramus osteotomy was made, preserving the inferior alveolar nerve. An intraoral device was placed along the ramus, and distraction was started on the third postoperative day at the rate of 1 mm/d and continued for 2 to 3 weeks or as long as necessary. The device was maintained for retention an additional 6 weeks and was then removed. RESULTS: Clinically, the face became more symmetric. The postdistraction posteroanterior cephalometric radiographs demonstrated elongation of the affected ramus and improvement in facial symmetry. CONCLUSIONS: The advantages of this method are that it allows device placement along the ramus, permitting the ramus elongation necessary in treatment of hemifacial microsomia, that it prevents damage to the tooth buds which, during the age of mixed dentition, are in a higher position in the retromolar area, and that it prevents injury of the inferior alveolar nerve.     

A customized distraction device for alveolar ridge augmentation and alignment of ankylosed teeth

The purpose of this study was to develop an extraosseous, tooth-supported miniature intraoral device that could produce prosthetically driven bone distraction of small atrophic alveolar ridge segments. Extraosseous distraction requires that the distraction device be anchored to a dental implant previously placed into the ridge according to its anatomic axis. A distractor can also correct the position of implants placed in young patients before skeletal growth is completed. Similarly, it allows the alignment of ankylosed teeth not treatable by orthodontics. The device is made of (1) an engine consisting of an orthodontic micrometric screw; (2) a joint between the implant and the engine, ie, the ball attachment/o-ring system; and (3) an anchorage system to the oral cavity provided by an orthodontic appliance and a mini-implant for possible additional support. Surgery involves an osteotomy of the atrophic alveolar ridge segment, incorporating the implant, from the basal bone; afterward the device can be applied and distraction of the segment can be carried out. Distraction was successfully performed in 3 clinical cases: 2 bone-implant segments and 1 bone-ankylosed tooth segment. All cases were clinically uneventful. This mini-device for osteogenic distraction of small atrophic ridge segments can provide for accurate and precise ridge augmentation, as is required for ideal prosthetic rehabilitation.     

Computer-aided surgery in distraction osteogenesis of the maxilla and mandible.

When using unidirectional intraoral distraction devices, it is desirable to be able to determine the final position of the bone fragment after the distraction procedure. However, additional constraining forces from adjacent tissues render the prediction of the distraction direction difficult. We have utilised computer-aided surgery in three patients for intraoperative control of the distraction direction. In one cleft palate patient, suffering from maxillary hypoplasia and anterior open bite, a modified Le Fort I osteotomy and maxillary distraction was performed. Despite a ventrocaudal position of the distraction device, intraoperative computer visualisation showed an unfavourable caudal vector of distraction without any anterior movement. The final result confirmed the direction indicated by the computer. Maxillary advancement remained insufficient. In two patients suffering from mandibular hypoplasia, intraoperative assessment revealed a favourable direction of distraction. The distraction procedure led to a satisfactory result in both cases. Computer-aided surgery is helpful in assessing the vector of distraction intraoperatively, making the result of the distraction procedure more predictable and allowing instant correction by adequate reapplication of the device.     

Orthodontic spring guidance of bilateral mandibular distraction in rabbits.

Although distraction osteogenesis can lengthen congenitally small mandibles, the distraction procedure can be difficult to control. To study the efficacy and safety of orthodontic spring guidance on bilateral mandibular distraction, an 8-mm anterior open bite was experimentally produced and corrected during bilateral mandibular distraction in rabbits. Orthodontic springs were attached to the anterior maxilla and mandible to redirect an ongoing distraction procedure. Sixteen rabbits underwent mandibular distraction: 6 rabbits received heavy springs (8 oz), 6 rabbits received light force springs (2 oz), and 4 rabbits served as control animals with anterior open bites without spring guidance. Nickel-titanium springs were applied during the last week of osseous distraction and the first week of consolidation. Distractors were left in place throughout a 2-month consolidation period. None of the animals developed fibrous union as a result of spring guidance. The 8-mm open bite did not close in the control group or in the light spring group after 2 weeks of spring wear or during the consolidation period. Heavy springs completely closed the experimental open bites within 2 weeks (P <.01, analysis of variance). Bite corrections did not change during the consolidation period. This study indicated that the addition of an orthodontic spring to a mandibular distraction procedure did not impair bone healing. With the distraction device in place, heavy spring forces redirected an ongoing mandibular distraction procedure and corrected an open bite, distraction side effect. Direct measurements, radiographic measurements, and tissue histologic factors described changes in segment position and shape of the distraction site.     

Vertical alveolar bone distraction at molar region using lag screw principle.

PURPOSE: Recently, alveolar bone distraction has been widely used and several devices have been developed for this purpose. However, there are some disadvantages in each device, especially for distraction of posterior alveolar ridge. The purpose of this study was to develop a new device for vertical alveolar bone distraction at the molar region and to show the results of its clinical application. MATERIALS AND METHODS: The mechanism of device is based on lag screw principle and the device consists of the following 4 components; distraction screw, hole implant fixture, supporting plate, and temporary short implant and/or neighboring natural teeth. The distraction screw suspended at the supporting plate is inserted into the internal thread of the hole implant fixture placed at alveolar transport segment. If the distraction screw turns at the supporting plate, the hole implant fixture with transport segment moves to the supporting plate without vertical movement of the screw at the supporting plate like a lag screw. After an animal experiment using 4 beagle dogs, the device was clinically applied in 4 patients before implant insertion. RESULTS: The distraction of the alveolar bone could be successfully performed in all patients without any complications. The direction of distraction with this device could be adjustable, and the alveolar bone could be distracted not only vertically but also horizontally. Moreover, the surgical technique is simple with no need for a second surgery, and there is no occlusal disturbance from the device. CONCLUSIONS: The new device for alveolar bone distraction using lag screw principle can be used effectively in the molar region.     

Use of a plate-guided distraction device for transport distraction osteogenesis of the mandible.

BACKGROUND: Transport distraction osteogenesis has been used to reconstruct continuity defects by regenerating bone and soft tissues. A challenge has been to maintain the correct vector during the distraction process. A new type of distraction device was recently developed that uses a standard reconstruction plate to "guide" the transported segment of the bone. This plate-guided distractor device (PGD) intimately follows the shape of the plate, thus allowing for 3-dimensional vector control during the distraction process. PATIENTS AND METHODS: Four patients underwent transport distraction osteogenesis for reconstruction of segmental mandibular defects ranging in size from 4 to 7 cm. The age of the patients ranged from 27 to 62 years. Two patients had been treated with radiotherapy as part of treatment for oral malignancy. A standard locking reconstruction plate was placed to bridge the continuity gap. An osteotomy was performed to create a bone transport segment. The PGD was secured to both the reconstruction plate and the transport bone. After a latency period of 7 days, the device was activated at a rate of 1 mm/d. The distraction process continued until the transport segment reached the opposing bone or sufficient bone and soft tissue were reconstructed for oral rehabilitation. RESULTS: All patients achieved hard and soft tissue formation. Two patients had premature consolidation of the distraction regenerate but had sufficient tissue for rehabilitation. CONCLUSION: A PGD can be used to regenerate missing hard and soft tissues. An advantage of this technique is that it uses a reconstruction plate that is routinely placed to bridge mandibular continuity defects. This device allows for ultimate vector control by intimately following a carefully adapted plate.     

Reconstruction of the alveolar ridge by osteodistraction for implant placement

Alveolar Distraction is a method for reconstructing a deficient or atrophic alveolar bone. Alveolar ridge reconstruction may be indicated for the atrophic alveolar process resulting from maxillofacial trauma, periodontal disease, or post aggressive large cyst or tumor resection. The aim of this paper is to demonstrate the method of reconstruction of the alveolar ridge by Distraction Osteogenesis. A total of 32 patients were treated. An alveolar segmental osteotomy was carried out and the distraction device was mounted. In patients with an extensive alveolar defect two distraction devices were placed in order to better control the vector of elongation in both bone edges. The distraction was started on the fourth post-operative day at a rate of 0.5 mm/day as necessary and according to the length of the distraction device, followed by a consolidation period of 90 days. Subsequently, the devices were removed, and dental implants were placed for osteointegration. The amount of elevation was 8-15mm. All the patients had panoramic x ray before the distraction, during the lengthening, at the end of distraction and after removal of the device. Early mineralization in the distracted area was seen radiographically during the consolidation period that increased after device removal. As a result of alveolar distraction, a segment of mature bone was transported vertically in order to lengthen the crest for better implant anchorage, either for esthetic purposes or for functional prosthetic requirements. A total of 68 implants were introduced. In follow-up at 24 months, failure of only one implant was noted, due to inadequate transported bone stability. In conclusion, distraction osteogenesis is an alternative treatment in moderate to severe alveolar deficiencies for an ideal three-dimensional reconstruction with no need for bone harvesting. This method offers the possibility to place dental implants in a correct position to obtain proper prosthetic results.     

Excellence in finishing: modifications for the perio-restorative patient

Orthodontic finishing is a continual challenge for the orthodontist. In some situations, it seems that the teeth simply “fall together” into their correct relationship with little effort on the part of the clinician. However, in other patients, it takes considerable effort and skill to achieve an excellent occlusal result after appliance removal. Futhermore, the increase in adult patients has brought a new challenge to the orthodontist. How should the teeth be positioned if the patient will require minor or major restoration of the teeth after orthodontic treatment? How should the clinician finish the occlusion if the patient has had significant periodontal bone loss before orthodontic therapy? How can the esthetics of a debilitated adult dentition be improved to resemble the nonworn, nonrestored, nonperiodontally involved adolescent dentition? These questions will be addressed in this article that identifies the occlusal, periodontal, and esthetic parameters for orthodontic finishing in the adolescent dentition, and provides useful guidelines for finishing in the adult perio-restorative patient.     

Vector control in lower jaw distraction osteogenesis using an extra-oral multidirectional device.

PURPOSE: This cephalometric study describes structural changes in facial features and occlusion during distraction of the mandible. PATIENTS: Seven patients aged 7-16 years with severely retrognathic lower jaws were treated by bilateral extra-oral distraction. The direction of the distraction was changed during the distraction period (mean 30 days) using the adjustable hinge in the distractor. Cephalometric follow-up documents were analysed for changes in facial and occlusal structures. The distraction therapy proceeded in two phases. First, horizontal distraction was undertaken to achieve a good incisor relationship. After this, the direction was changed to a more vertical plane with the use of a hinge axis, and the tips of the lower incisors were used as the axis of rotation. RESULTS: The most remarkable changes were in the more anterior position of the lower jaw, the increase in ramus height and good dental overjet. The mandibular occlusal plane became more horizontal, creating a posterior open bite. By guiding the vector of distraction, no anterior open bite or lateral crossbite appeared. CONCLUSION: This study points out the advantages of using extra-oral multidimensional distractors. Severe lower jaw deficiency requires not only a long working length of the device but also precise control of the vector during the active phase of distraction.     

Distraction osteogenesis for augmenting the deficient alveolar ridge in preparation for dental implant placement: a case report

Distraction osteogenesis is a process in which new bone is created in a defect of the alveolar ridge by stretching existing bone. The process was originally developed by a Russian orthopedist, Gavriel Ilizarov, for the correction of long-bone deformities. It was later adapted to the maxillofacial skeleton and alveolar ridge. Distraction osteogenesis involves surgically creating a mobile bone segment to which a distraction device is attached. By controlled movement, the bone segment, along with the soft tissues overlying it, are transported into a new position. After a suitable healing period, the distraction device is removed and dental implants can be placed. A case report is presented describing the use of alveolar distraction to augment a vertically deficient alveolar ridge.     

Management of alveolar clefts using dento-osseous transport distraction osteogenesis

This article evaluates the usage of distraction osteogenesis (DO) in the treatment of cleft alveoli. The procedure was carried out on eight alveolar clefts of five patients between the ages of 17 and 25 years. Three patients had bilateral alveolar clefts (BAC) and two patients had unilateral alveolar clefts (UAC). DO was carried out bilateral to the palatal segments for the BAC patients and unilateral to the lesser segment for the UAC patients. A custom-made tooth-borne distractor was used. The average amount of distraction was eight mm (range, 5-11.5 mm). The average amount of distal movement of the anchorage teeth was 0.8 mm (range, 0-2 mm). The average amount of inclination changes of the transport segments and anchorage teeth was 7.6 degrees (range, 2-17.5 degrees) and 3.3 degrees (range, 0-9 degrees), respectively. Two important problems were observed attributable to the method. First, the transport segment was docked in a more superior position at the end of distraction process. This undesirable movement also changed the inclination of the teeth in the transport segment and increased tooth tipping. Removing the device in the second week of the consolidation period and retracting the segment to its ideal position orthodontically solved these problems. Second, the bony defect on the nasal side of the alveolar cleft could not be completely closed. This method for repairing small or large alveolar clefts is a simple, cost-effective, and useful treatment option. However, repairing the alveolar cleft without grafts seems to be impossible when using a tooth-borne device.     

A new way to anchor the external device in mandibular distraction: three case reports with a Pierre Robin sequence

Pierre Robin sequence is a pathology derived from alteration in the first and second branchial arch. Patients have breathing problems due to micrognathia and glossoptosis, causing severe upper airway obstruction. One surgical treatment is distraction osteogenesis. Three patients with Pierre Robin sequence (case 1, 3 months old; cases 2 and 3, 1 month old) with severe upper airway obstruction requiring mechanical ventilator assistance, underwent mandibular distraction osteogenesis prematurely with a new anchoring system, thus avoiding tracheostomy and its consequences. An intraoral approach was used to avoid scarring. A new anchoring device with transfixing Kirschner wire in the proximal (mandibular ramus) and distal segment (chin zone) was used. This diminishes the risk of distractor device displacement, guaranteeing optimal stability. A more anterior installation reduces the risk of damaging tooth buds in the mandibular body and the inferior alveolar nerve. The more anterior the fixation, the more horizontal the distraction vector becomes. The position and stability of the device are crucial. In these three patients the placement of two transfixing Kirschner wires using an intraoral approach showed good results and stability during the period of distraction and consolidation, with optimal results on the upper airway, avoiding tracheostomy.     

Reliability of distraction vector transfer in unilateral vertical distraction of the mandibular ramus

Mandibular distraction osteogenesis fails in correcting the skeletal deformities if the vector of distraction is incorrect. Lack of vector control is caused mainly by two factors: first, deficient vector planning and transfer, and, second, resistance of the masticatory muscles and the remaining soft tissue envelope toward elongation. To enhance predictable placement of intraoral distraction devices during surgery and thereby the treatment outcome, a method combining planning, simulation, and transfer was developed. The presurgical planning was based on frontal and lateral head films, and the planned position and orientation of the distraction device was applied on the stereolithographic model. This model was cut according to the planned osteotomy, and the distraction was simulated. The transfer procedure copied the planned and simulated position of the distraction device during surgery by use of an individual guiding splint. The guiding splint was fabricated on plaster models, and transferred to the stereolithographic model to reproduce the planned and simulated distraction treatment during surgery. The reliability of the vector-transfer method was evaluated cephalometrically in a homogenous group of 13 patients and their respective stereolithographic models in comparison with the planned, simulated, and transferred distraction vectors.     

自制牙支持式牵张器治疗上颌骨畸形

目的:探讨运用自制牙支持式牵张器治疗上颌骨畸形.方法:利用自制牙支持式牵张器进行上颌骨牵张,治疗唇腭裂术后继发上颌发育不足、重度上颌后缩畸形、上颌骨获得性畸形等,共28 例.结果:除2 例因牵张器松动致牵张失败需重新手术外,余者术创正常愈合,牵张过程顺利,达到预期牵张目的.结论:牙支持式牵张器可有效的治疗上颌骨发育不足及软组织量不足的患者.     

Controlled multiplanar distraction of the mandible, Part II: Laboratory studies of sagittal (anteroposterior) and vertical (superoinferior) movements

The application of distraction osteogenesis in craniofacial surgery has significantly altered the treatment of congenital mandibular deficiencies. However, evaluation of results in both animal studies and clinical cases has revealed deficiencies, particularly in two areas. First, distraction using a uniplanar device in an anteroposterior direction can result in a persistent anterior open bite. Second, the lateralization of the distracted hemimandible was often limited, with insufficient incremental gain in the bigonial distance. To overcome these shortcomings, a multiplanar distraction device was developed and tested in the canine model. This report details canine studies addressing the first problem: combined anteroposterior or sagittal (z-axis) and superoinferior or vertical (y-axis) movements. Six dogs underwent bilateral mandibular distraction with an external (extraoral), multiplanar device and completed sagittal plus vertical distraction. Evaluation included clinical examination (facial form, jaw position, and occlusion), photography, cephalograms (posteroanterior, basilar, and lateral), three-dimensional computed tomography reconstructions, and examination of dry skulls. The dogs averaged 18.5 mm (range, 15-20 mm) of sagittal distraction and 41.0 degrees (range, 21-50 degrees) of vertical distraction. Marked anterior open bites were produced after vertical distraction secondary to premature contact of the maxillary and mandibular molars. Distraction in the vertical direction also had the additive effect of increasing the sagittal gains by approximately 5% to 10%. In conclusion, a multiplanar distraction device (with the potential for distraction in three planes) was effective in increasing mandibular anteroposterior thrust (sagittal distraction) and also in creating an anterior open bite (vertical or superoinferior distraction). Vertical distraction probably requires bilateral osteotomies to obtain optimal results. The preliminary gains in sagittal length are modified (reduced or increased) after distraction in a second plane (vertical and horizontal). Specifically, vertical distraction in the inferior direction (creating an open bite) also leads to isolated increases in the anteroposterior plane. Conversely, vertical distraction in the superior direction (closing an open bite), as seen in a human malocclusion, may lead to isolated decreases in the anteroposterior plane, but this question remains to be investigated in the laboratory.     

Treatment of an ankylosed central incisor by single tooth dento-osseous osteotomy and a simple distraction device.

When teeth are replanted after being avulsed, the repair process sometimes results in ankylosis. In a growing child, the ankylosed tooth fails to move along with the remaining alveolar process during vertical growth, resulting in a tooth that gradually appears more and more impacted and requires several reconstructive procedures to correct. Ankylosed teeth can, however, serve as anchorage for orthodontic correction of a malocclusion and as a point of force application for a dentoalveolar segment during alveolar distraction osteogenesis. This case report describes the treatment of a 13-year-old girl whose maxillary left central incisor had been avulsed and replanted 5 years earlier. The tooth had become ankylosed, and it was used to provide "free anchorage" during distalization of the maxillary dentition. The underdeveloped alveolar process adjacent to the ankylosed tooth was reconstructed by dento-osseous segment distraction osteogenesis, by using the ankylosed tooth as the point of force application.