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PubMed2002

Condylar displacement related to mandibular symphyseal distraction.

This study was undertaken to determine the true nature of condylar displacements associated with mandibular symphyseal distraction osteogenesis. Earlier investigators have assumed that each mandibular half rotated about a point near the center of each condyle as viewed on a submental radiograph. In a 12-patient sample, 10 with tooth-borne symphyseal distraction and 2 with bone-borne symphyseal distraction, it was found that each condyle was laterally displaced in direct relationship to the amount of symphyseal distraction. The rigidity of the distraction appliances and their attachments and the inability of the soft tissues and muscular attachments to cause the mandible to undergo compound bending require this to be the case. Temporomandibular joints appear to be able to accommodate the lateral displacements because symptoms were not introduced, or, if present before therapy, distraction did not exacerbate them.

Adaptation, Physiological↗
PubMed2003

Alterations of morphology and microdensity in the condyle after mandibular osteodistraction in the rat.

PURPOSE: In this study, we examined the effects of mandibular distraction osteogenesis on the morphology and the microdensity of the rat condyle. MATERIALS AND METHODS: One hundred twenty-nine rats were allocated to 4 experimental groups (n = 32 or 33). Each received unilateral mandibular ramus osteotomy and distraction device placement. After a 3-day latency, these were distracted once a day for 5 days. The slow distraction group was distracted a total of 1 mm (0.2 mm/d); the moderate group, 2 mm (0.4 mm/d); the rapid group, 3 mm (0.6 mm/d); and the sham group, no distraction (0.0 mm/d). Eight to 9 rats in each group were sacrificed at each of 4 time points after device placement (6, 10, 24, and 38 days). Baseline data were obtained 3 days after osteotomy and device placement without distraction from an additional 10 rats. Radiographs of the hemimandibles were scanned and measured to evaluate changes in condylar size (height, width, and area), angulation, and bone microdensity converted to equivalent bone thickness using a stepwedge. The wet weights of masseter muscle were measured at the time of harvest. RESULTS: 1) Muscle weight gains over time were significantly lower in the treated than the untreated sides throughout the consolidation period (P <.001). 2) Condylar size and angulation on the untreated side increased postoperatively, whereas there was a significant reduction of these parameters (P <.01 to.001) on the treated side at 24 and/or 38 days. 3) Condylar microdensity significantly increased on the untreated side at 24 and 38 days (P <.05 to.01) but not on the treated side. 4) Faster or larger distraction caused more severe size reduction and more upright condylar angulation, prevented an increase in bone microdensity on the treated side, especially during the consolidation periods (P <.05 to.01), and retarded increase in muscle weight, whereas a slower distraction rate showed few negative, and even some positive effects. 5) Correlations in size, angulation, and microdensity between right and left condyles became less significant over time. 6) There were positive correlations between muscle weight and condylar size, angulation, and microdensity. CONCLUSION: An increased rate of mandibular distraction has significant negative effects on condylar morphology and microdensity.

Analysis of Variance↗
PubMed2006

Craniofacial bone tissue engineering.

Repair and reconstruction of the craniofacial skeleton represents a significant biomedical burden, with thousands of procedures per-formed annually secondary to injuries and congenital malformations. Given the multitude of current approaches, the need for more effective strategies to repair these bone deficits is apparent. This article explores two major modalities for craniofacial bone tissue engineering: distraction osteogenesis and cellular based therapies. Current understanding of the guiding principles for each of these modalities is elaborated on along with the knowledge gained from clinical and investigative studies. By laying this foundation, future directions for craniofacial distraction and cell-based bone engineering have emerged with great promise for the advancement of clinical practice.

Biomechanical Phenomena↗
PubMed2005

[The effect of dog bilateral distraction osteogensis in temporomandibular joint].

OBJECTIVE: To investigate the effect of bilateral mandibular distraction osteogenesis in the condyles. METHODS: 16 adult hybrid dogs were randomly divided into normal control group and experiment group. Experimental dogs underwent bilateral mandibular osteodistraction at a rate of 1 min/day. 4 dogs were killed respectively in distraction period, 2 and 8 weeks after completion of 10 days distraction. The bilateral condyles specimens were harvested and examined with histological and immunohistochemical methods. RESULTS: Compared with normal control group, various degrees of irregularities and erosion were found in fibrocartilage of condyle in experiment group, including damage in fibrous layer, hyperplasia layer and proliferative layer and osteogenic activity in cartilage layer. A significant increase of TGF-beta1 expression was also found in experiment groups. TGF-beta1 positive staining was noted in hypertrophic cell, matrix and chondroblast, osteoblast and matrix in osteogenic activity areas. These changes were the most obvious in 2 weeks after completion of distraction. CONCLUSION: Gradual bilateral mandibular distraction at a rate of 1 mm/day brought degenerative changes of condyle, but the changes are reversible.

Animals↗
PubMed2004

Enhancement of bone formation by bone morphogenetic protein-2 during alveolar distraction: an experimental study in sheep.

BACKGROUND: The purpose of this study was to perform alveolar ridge augmentation by distraction osteogenesis (DO) and to enhance bone regeneration through the use of recombinant human bone morphogenetic protein-2 (rhBMP-2), followed by implant placement. METHODS: Alveolar segmental osteotomy was performed in the mandible of 10 sheep followed by placement of 1.5 mm alveolar distraction devices. The study group was injected on the fifth day of distraction with a single dose of 10 microg rhBMP-2. Only distraction was performed in the control group. RESULTS: A mean alveolar augmentation of 12 mm was achieved. After 12 weeks of consolidation, the distraction devices were removed and biopsies were taken for histological and immunohistochemical characterization and morphometry of the newly formed bone. Titanium threaded cylindrical implants were then placed in the newly augmented bone. Radiological evaluation showed lifting of the transport segment and integration of the implants within both the transport segment and the regenerated bone. The histological study demonstrated that the association of DO and BMP resulted in increased trabecular bone size and volume (32.2%+/-0.95% versus 18.6%+/-0.71%; P <1 x 10(-17) after 24 days of lengthening and 63.8%+/-1.89% versus 42.5%+/-1.33%; P<1 x 10(-15) after 12 weeks of consolidation) and increased numbers of proliferating cell nuclear antigen stained cells (0.7+/-0.04 versus 0.47+/-0.04; P<1 x 10(-10)) compared with the DO only group. CONCLUSIONS: Alveolar distraction augments atrophic alveolar ridge and creates new bone that permits implant placement. rhBMP-2 enhances bone quality and may shorten the consolidation period of distraction allowing for earlier implant placement.

Alveolar Bone Loss↗
PubMed2005

Microstructural and strength evaluation of regenerate tissue during the consolidation period after vertical mandibular ramus distraction.

Mandibular ramus height restoration by distraction osteogenesis (DO) is a key procedure in mandibular hypoplasia reconstruction. The objective of this study was to evaluate short-term skeletal changes in the regenerated bone after vertical mandibular ramus DO using a buried distraction device. Eight subadult beagle dogs underwent bilateral vertical mandibular ramus DO. After a 7-day latency period, distraction was performed at a rate of 0.5 mm twice a day for 12 days. Four dogs were killed at 1 month and four dogs at 2 months after the end of distraction. One intact beagle was included as an unoperated control. After sacrifice, micro computed tomography (muCT) and mechanical testing of distracted sites were used to measure bone volume (BV), total volume (TV), and mechanical peak load strength, respectively. The muCT images showed wide variation in the response, with some animals demonstrating considerable bone formation and reconstitution of the canal for the inferior alveolar nerve. Quantitatively, BV was no more than 67% and BV/TV was less than 25% of the intact control, and strength was approximately 33% of the intact control value. The 1 and 2 month values were similar. These results suggest that internal distractors can successfully reconstitute bone but that the regenerated tissue did not regain structural and mechanical characteristics of native bone within the 2 month study period.

Animals↗
PubMed1998

Controlled multiplanar distraction of the mandible: device development and clinical application.

Distraction osteogenesis has been shown to be an effective method of lengthening and augmenting endochondral bone. It has also been applied effectively in the reconstruction of the membranous bones of the craniofacial skeleton. With the accumulation of clinical experience in mandibular distraction, the differences between endochondral and membranous bone distraction have become apparent, especially in the limitations of uniplanar distraction for the three-dimensional reconstruction of the deficient mandible. Distraction of the mandible in a single plane cannot satisfy fully the functional and structural requirements of the patient with malocclusion as well as deficiency of the skeletal and soft tissue. This study reports the development and clinical use of a multiplanar mandibular distraction device with the ability to achieve linear distraction (Z-plane or sagittal), angular distraction (Y-plane or vertical), and transverse distraction (X-plane or coronal). The device contains two independent gear arrangements attached to two arms that extend from the central unit. Therefore, the trajectory of the regenerated bone may be changed during the distraction process. The device also allows manipulation of the various planes of movement independent of each other. Furthermore, the rotational points for the multiplanar distraction devices are located at a single point; therefore only a single osteotomy and two pin sites are required. The multiplanar distraction device allows the surgeon to customize and contour the dimensions of the distraction process by controlling the trajectory of the translation of the regenerated bone.

Child, Preschool↗
PubMed2000

Effect of distraction rate on biomechanical, mineralization, and histologic properties of an ovine mandible model.

Craniofacial microsomia is a common congenital malformation. Ilizarov's method of distraction osteogenesis applied to the mandible has yielded promising results both experimentally and clinically. Because the technique is used predominantly in a pediatric population, length of treatment and compliance may be problematic. To date, the limits of distraction rate in the craniofacial skeleton have not been defined. This study was designed to investigate the effects of distraction rate, in a large animal model, on the mineralization, biomechanical, and histologic properties of lengthened mandibles. Clinically faster distraction rates would decrease the overall treatment time. Twenty-four animals were divided into four groups, with varying rates of distraction (1, 2, 3, and 4 mm/day). A uniaxial distractor at the angle of the mandible was used. The mandibles were lengthened to 24 mm and fixed for a period of 5 weeks, when the animals were killed. The specimens were analyzed with respect to mineralization using dual energy x-ray absorptiometry, biomechanical strength, through a modified three-point bending test, and histologic properties with hematoxylin and eosin stains. Biomechanical, mineralization, and histologic analyses of the samples indicated that group 1 (1 mm/day) samples were significantly superior (p<0.05) to those of group 4 (4 mm/day). Although bone formation was achieved in all groups, group 1 (1 mm/day) demonstrated the strongest biomechanical and histologic properties. Bone mineral density obtained using dual energy x-ray absorptiometry may be clinically useful as a reliable, noninvasive, and relatively cheap predictor for removal time of the fixator.

Animals↗
PubMed2000

Force level and strain patterns during bilateral mandibular osteodistraction.

PURPOSE: Recent reports have demonstrated that device orientation is important during mandibular distraction osteogenesis. The purpose of this study was to evaluate the force level and strain patterns on the mandible during bilateral osteodistraction with devices oriented either parallel to the body of the mandible or parallel to the sagittal axis of distraction. MATERIALS AND METHODS: Five unembalmed human cadaver mandibles were placed in a specially designed apparatus for stabilization of the proximal segments during distraction. A force transducer was attached to the lateral aspect of the inferior ramus, and strain gauges were attached to the mandibular bone segments proximal and distal to the distraction device. Lateral force and bone strains were then measured at 5 and 10 mm of distraction. Osteodistraction proceeded first with the devices placed parallel to the mandibular body, then parallel to the axis of distraction. RESULTS: Significantly greater lateral forces were seen when the devices were oriented parallel to the mandibular body. With this device orientation, increased tensile strains were seen at the labial symphysis and medial ramus, and increased compressive strains were found at the lingual symphysis and lateral ramus. However, when the devices were oriented parallel to the axis of distraction, the forces and strains were not detected. CONCLUSIONS: The results suggest that device orientation has important biomechanical effects on lateral forces and strain patterns during mandibular osteodistraction.

Adult↗
PubMed2002

Immediate versus delayed midface distraction in a primate model using a new intraoral internal device.

The theoretic advantage of distraction osteogenesis of the craniofacial skeleton, especially in cases of severe midface retrusion and in the presence of maxillary scarring, is prevention of relapse following significant advancements. The purpose of this study is to demonstrate the utility of a new low-profile, intraoral, internal device for midface distraction at the conventional or high Le Fort I level. In addition, the present study compares the efficacy of immediate versus delayed distraction on subsequent maxillary relapse. Four adult rhesus Macaca mulatta monkeys were divided into two groups. Group 1 underwent immediate midface distraction; group 2 underwent delayed distraction. All four monkeys underwent a modified Le Fort I osteotomy through an upper buccal sulcus incision and bilateral application of the intraoral midface distraction devices. No other osteotomies or incisions were necessary. Immediate distraction, performed in group 1, entailed intraoperative activation of the devices and distraction of 10 mm followed by a 5-day lag period before postoperative activation and distraction of an additional 10 mm at the rate of 1 mm/day. Delayed distraction, performed in group 2, entailed a 5-day postoperative lag period before device activation and distraction of 20 mm at the rate of 1 mm/day. Both groups thus underwent 20 mm of midface distraction. All devices were removed 6 weeks after completion of distraction. All monkeys tolerated the devices and daily distraction uneventfully. On the basis of serial cephalograms and dental models obtained throughout the experimental period, there was no evidence of relapse in either the immediate or delayed groups 6 months after distraction. In addition, on the basis of histologic, ultrastructural, and dry skull analysis, no significant differences were observed in the quality of regenerate bone obtained when comparing the immediate and delayed distraction groups. Significant midface advancement is thus feasible using this new internal, intraoral distraction device, which presents several advantages over other internal devices that require coronal incisions and additional osteotomies to achieve midface advancement. In addition, immediate distraction may abbreviate the distraction period without adverse sequelae.

Animals↗
PubMed2005

Bone formation is impaired in a model of type 1 diabetes.

The effects of type 1 diabetes on de novo bone formation during tibial distraction osteogenesis (DO) and on intact trabecular and cortical bone were studied using nonobese diabetic (NOD) mice and comparably aged nondiabetic NOD mice. Diabetic mice received treatment with insulin, vehicle, or no treatment during a 14-day DO procedure. Distracted tibiae were analyzed radiographically, histologically, and by microcomputed tomography (microCT). Contralateral tibiae were analyzed using microCT. Serum levels of insulin, osteocalcin, and cross-linked C-telopeptide of type I collagen were measured. Total new bone in the DO gap was reduced histologically (P < or = 0.001) and radiographically (P < or = 0.05) in diabetic mice compared with nondiabetic mice but preserved by insulin treatment. Serum osteocalcin concentrations were also reduced in diabetic mice (P < or = 0.001) and normalized with insulin treatment. Evaluation of the contralateral tibiae by microCT and mechanical testing demonstrated reductions in trabecular bone volume and thickness, cortical thickness, cortical strength, and an increase in endosteal perimeter in diabetic animals, which were prevented by insulin treatment. These studies demonstrate that bone formation during DO is impaired in a model of type 1 diabetes and preserved by systemic insulin administration.

Animals↗
PubMed2004

A comparison of two types of free bone grafts as transport discs in segmental distraction for reconstruction of calvarial bone defects: an experimental study.

INTRODUCTION: Several investigations over the past few years have shown that the importance of preserving the blood supply of the transport disc during segmental distraction has been overestimated. It was clearly demonstrated that distraction osteogenesis by local bone transportation could be achieved even with free bone grafts. So far, there have been no systematic investigations into how different types of free bone grafts vary in their function and suitability as transport discs in segmental craniofacial distraction. The aim of this study was to develop criteria to aid the clinician in selecting the most suitable free bone graft for distraction purposes. MATERIALS AND METHODS: Under general anesthesia, calvarial defects measuring 6 x 5 cm were created in 12 adult black head sheep in order to reconstruct them by segmental distraction using two different types of bone grafts as transport discs. Group 1 (n=6) received autotopical membranous bone of the calvarium as the transport segment, while group 2 (n=6) received heterotopical enchondral material from the iliac crest. Distraction was started postoperatively after 5 days at 0.6 mm/day and continued for 7 weeks. After a further 6 weeks of consolidation, the animals were killed and specimens examined macroscopically, radiographically and histologically. RESULTS: The significantly better quality of bone regenerates of group 1 was clearly influenced by the significantly better stability of the transport disc's connection to the distraction device, the calvaria grafts showing better volume stability and better mechanical resistance during transport than the iliac bone. The influence of both types of bone grafts on the macro- and microstructure of the newly formed bone was clearly evident. The mineralization density of group 2 regenerates was significantly lower than that of group 1 specimens. CONCLUSION: High mechanical stability of the bone graft is a very important point to consider when selecting a free graft for use as transport disc in local bone transport, especially if transport is necessary over long distances.

Animals↗
PubMed2003

Molding of the regenerate in mandibular distraction: clinical experience.

Initial clinical experience with distraction osteogenesis has demonstrated the risk of developing postdistraction malocclusion that requires secondary orthodontic correction. In addition, optimal mandibular form is not always achieved. Both animal studies and preliminary clinical investigations have suggested that the regenerate can be successfully "molded" during active mandibular distraction. The authors have applied this concept clinically to obtain a more desirable occlusal relationship in a group of mandibular distraction patients. Eleven patients are described in whom angulation of the distraction device or intermaxillary/interdental elastics were employed to mold the regenerate. Two representative case studies are provided to illustrate the principles. When using elastic traction to close an anterior open bite, care must be taken that extrusion of individual teeth is minimized by distributing the force over the entire dental arch, especially the basilar portions of the jaws. The authors demonstrate that molding of the regenerate can be successfully accomplished not only during device activation but also early in the consolidation period. The outer limit of the time window in which molding is effective remains to be defined.

Adolescent↗
PubMed2002

Midface distraction following Le Fort III and monobloc osteotomies: problems and solutions.

Distraction osteogenesis has been used increasingly for midfacial advancement in patients with syndromic craniosynostosis and in severe developmental hypoplasia of the midface. In these patients, the degree of advancement required is often so great that restriction of the adjacent soft tissues may preclude stable advancement in one stage. Whereas distraction is an ideal solution by which to gradually lengthen both the bones and the soft tissues, potential problems remain in translating the distraction forces to the midface. In these patients, severe developmental hypoplasia may be associated with weak union between the zygoma and the maxilla, increasing the chance of zygomaticomaxillary dysjunction when using internal devices that translate distraction force to the maxilla through the zygoma. Eight cases are reported in which either internal or external distraction systems were used for midface advancement following Le Fort III (n = 7) or monobloc (n = 1) osteotomies. Cases of patients in whom hypoplasia at the zygomaticomaxillary junction altered or impaired plans for midface distraction were reported from three host institutions. Seven patients had midface hypoplasia associated with syndromic craniosynostosis, and one patient had severe developmental midface hypoplasia. The distraction protocol was modified to successfully complete midface advancement in light of weakness at the zygomaticomaxillary junction in seven patients. Modifications included change from an internal to an external distraction system in two patients, rigid fixation and bone graft stabilization of the midface in one patient, and plate stabilization of a fractured or unstable zygomaticomaxillary junction followed by resumption of internal distraction in four patients. Previous infection and bone loss involving both malar complexes precluded one patient from being a candidate for an internal distraction system. Using a problem-based approach, successful advancement of the midface ranging from 9 to 26 mm at the occlusal level as measured by preoperative and postoperative cephalograms was undergone by all patients. Advantages and disadvantages of the respective distraction systems are reviewed to better understand unique patient characteristics leading to the successful use of these devices for correction of severe midface hypoplasia.

Child↗
PubMed2006

Complications in maxillary distraction using the RED II device: a retrospective analysis of 21 patients.

Rigid external distraction osteogenesis (DO) in the treatment of midface hypoplasia has been shown to be effective and safe, but there have been several case reports on complications. Here is presented an overview of the complications in a series of 21 patients with various craniofacial anomalies. All patients were treated using the rigid external distraction II (RED II) device after Le Fort I or III osteotomy. Distraction started 1 week postoperatively and continued until Class I occlusion was achieved; it was then continued to include a 15% overcorrection. All data were collected and categorized retrospectively from the patients' files. After a mean period of distraction of 34 days, 42 complications were reported in six different categories. Pin loosening (42.9%) and frame migrations (28.6%) were the most common complications. Of the frame migrations 25% were traumatic. Intracranial penetration of one fixation pin occurred during removal of the RED II device in one patient. From these results it can be deduced that application of the RED II device is associated with a substantial number of specific complications that mainly concern the pins of the halo-frame. The stability of the device is discussed as the distraction distance achieved was less than expected.

Adolescent↗
PubMed1997

2/3 osteotomy for lengthening the mandible in dogs by gradual distraction.

Successful lengthening of the mandible by gradual distraction has been reported previously. There are various methods for osteotomy before distraction osteogenesis. In this paper, a new type of osteotomy, performed on growing dogs as a model, is reported. Ten mongrel dogs, aged 6 months, were studied. A unilateral 2/3 osteotomy was performed, and an external lengthening device was fixed to the mandible perpendicular to the osteotomy. Seven days after the operation, the mandible was lengthened by 1 mm per day. The dogs were sacrificed for histological study at the end of the distraction on days 14, 28, 56 and 120 following completion of the distraction.

Animals↗
PubMed1999

[Changes in the nasal airway by transverse distraction of the maxilla].

OBJECTIVE: To investigate nasal airway changes through transverse maxillary distraction osteogenesis by means of an objective, reliable, noninvasive investigation technique with special attention to nasal valve changes and widening of the posterior maxilla. PATIENTS AND INTERVENTION: Eight patients with a severe maxillary transversal deficit underwent surgically assisted rapid palatal expansion in local or general anesthesia. Before and after the distraction process, a transnasal series of acoustic measurements of nasal airway profile was performed under topical decongestion. Nasal volume was calculated by integration of the area profile. The cross-sectional area of the nasal valve was also determined. RESULTS: A significant enlargement of nasal volume was recorded in all patients (P < 0.01: Wilcoxon signed rank test). The average increase measured 5 cm3 (23%). The increase in volume was recorded in all parts of the nasal cavity, indicating complete maxillary expansion even in the posterior segment. The nasal valve area raised from 0.56 to 0.70 cm2 (P < 0.01). Six out of eight patients reported striking improvement of nasal patency after maxillary distraction. CONCLUSION: Besides correction of the maxillary arch deformity, rapid palatal expansion contributes to improved nasal patency by resolving nasal valve constriction. Significant widening of the posterior nasal cavity was achieved, indicating a translational pattern of maxillary movement, although the pterygomaxillary junction was not touched in the osteotomy.

Adult↗
PubMed2005

Evaluation of minipigs as an animal model for alveolar distraction.

OBJECTIVE: Alveolar distraction osteogenesis is a relatively novel tissue regeneration technique that remains, in some respects, at an experimental stage. The selection of an experimental animal biomodel is not clearly defined, with reports in the reviewed literature on dogs, sheep, and monkeys. The present objective was to compare 2 experimental biomodels (dog and minipig) using an alveolar distraction protocol with a novel prototype distractor. STUDY DESIGN: Three beagle dogs and 3 Göttingen minipigs were evaluated, placing the distractor at the right hemimandible alveolar ridge after previous extraction of premolars. The radiological examination was carried out immediately after the distraction and at 2 weeks of consolidation. RESULTS: Satisfactory clinical and radiological results were obtained in 2 of 3 beagle dogs after the previous unilateral extraction of mandibular and maxillary premolars. During the consolidation, a height gain of approximately 5 mm was observed, with the appearance of radiodense bone trabeculae in the distraction chamber. The distraction failed in all of the minipigs. CONCLUSION: The minipig was not an appropriate biomodel for the study of alveolar distraction because the investigators were not able to maintain the seal of the distraction chamber or the stability of the distractor.

Alveolar Process↗