Rat mandibular distraction osteogenesis: II. Molecular analysis of transforming growth factor beta-1 and osteocalcin gene expression

Distraction osteogenesis is a powerful technique capable of generating viable osseous tissue by the gradual separation of osteotomized bone edges. Although the histologic and ultrastructural changes associated with this process have been extensively delineated, the molecular events governing these changes remain essentially unknown. We have devised a rat model of mandibular distraction osteogenesis that facilitates molecular analysis of this process. Such information has significant clinical implications because it may enable targeted therapeutic manipulations designed to accelerate osseous regeneration. In this study, we have evaluated the expression of transforming growth factor beta-1, a major regulator of osteogenesis during endochondral bone formation and development, and osteocalcin, an abundant noncollagenous extracellular matrix protein implicated in the regulation of mineralization and bone turnover. The right hemimandible of 36 adult male rats was osteotomized, and a customized distraction device was applied. Animals were allowed to recover and, after a 3-day latency period, were distracted at a rate of 0.25 mm twice daily for 6 days followed by a 2- or 4-week consolidation period. Distraction regenerate was harvested after the latency period, days 2, 4, or 6 of distraction, and after 2 or 4 weeks of consolidation and processed for Northern analysis (n = 4 at each time point) and immunohistochemical localization of TGF-beta1 (n = 2 at each time point). Six sham-operated animals (i.e., skin incision without osteotomy) were also killed (immediately postoperatively), and the mandibles were harvested and prepared in a similar fashion. Equal loading and transfer of RNA for Northern analysis was ensured by stripping and probing membranes with a probe against GAPDH (a housekeeping gene). Our results demonstrate that the spatial and temporal patterns of TGF-beta1 mRNA expression and protein production coincide with osteoblast migration, differentiation, and extracellular matrix synthesis. In addition, we demonstrate that TGF-beta1 production may be an important regulator of vasculogenesis during mandibular distraction osteogenesis. Finally, we have shown that osteocalcin gene expression coincides temporally with mineralization during rat mandibular distraction osteogenesis.     

Content and predictors of the ethnic identity of Russian-speaking immigrant adolescents in Finland

Even though osteodistraction has been well established in the extremities, the parameters used in craniofacial distraction have been essentially borrowed from orthopaedic experience. Latency is widely practised but its relevance has not been fully investigated. The purpose of this study was to establish the role of latency in mandibular distraction osteogenesis. Twenty-two growing Wethers sheep were allocated to four experimental groups. Six animals were allocated to each of Groups A, B and C and underwent bilateral mandibular corticotomies and attachment of an external lengthening device. Latent periods of 0, 4 and 7 days respectively were observed prior to beginning distraction. The distraction protocol consisted of a rate of 0.5 mm twice daily for 20 days, followed by a consolidation phase of 20 days after which the sheep were killed. Histology, bone densitometry and 3-point mechanical testing were performed on the harvested mandibles. Group D formed the control group (n = 4). Histologically, the distracted bone exhibited bone formation primarily via intramembranous ossification with scattered islands of cartilage. The regenerated bone had mechanical properties significantly weaker than the undistracted control group (P < 0.05), but between the experimental groups no statistically significant differences were demonstrable either in mechanical strength or DEXA density. These data indicate that a change in latency does not alter the properties of the regenerated bone in mandibular distraction osteogenesis and indeed no latent interval may be necessary at all in craniofacial distraction. This has implications for the duration of device fixation in distraction procedures.     

Changes in the aortic endothelium and plasma von Willebrand factor levels during the onset and progression of insulin-dependent diabetes in BB rats

The superior volume maintenance of membranous over endochondral bone has been shown in several studies and provides the basis for its preferred clinical use as an onlay grafting material in the craniofacial skeleton. The scientific rationale for this seeming embryologic advantage, however, has never been proven. Our hypothesis is that the pattern of onlay bone graft resorption is primarily determined by a graft's micro-architecture (relative cortical and cancellous composition) rather than its embryologic origin (membranous versus endochondral). Twenty-five adult New Zealand, White rabbits were used for this study. Eight animals were killed at 3 weeks, eight animals at 8 weeks, and nine animals at 16 weeks. Three graft types were placed onto each rabbit cranium: cortical bone graft of membranous origin and cortical and cancellous bone graft of endochondral origin. Fluorochrome markers were injected into all living rabbits at 1, 6, and 14 weeks. Microcomputed tomography scanning was performed on all of the bone grafts to determine postsacrifice volumes and to obtain detailed information regarding the bone graft's trabecular architecture. In addition, specimens were examined histologically. Volume analysis showed a statistically greater resorption rate in the cancellous endochondral bone graft than in either the endochondral or membranous cortical bone grafts (p < 0.05) for all time points. In addition there was no significant difference in the resorption rates between the endochondral and membranous cortical bone grafts. A post-test power analysis (alpha = 5 percent) of the volume data comparing the two types of cortical bone grafts showed that a difference in resorption of 8.9 percent would be detected with a 90-percent probability. Previous studies, which have shown a seeming superiority of membranous over endochondral bone grafts, used composite grafts composed of both cortical and cancellous portions. By separating these components, we have shown that cortical bone grafts maintain their volumes significantly better than cancellous bone grafts. In addition, we found no statistical difference in the resorption rates between the two cortical onlay bone grafts of different embryologic origins, a finding that has never been previously published. From our results, we believe cortical bone to be a superior onlay grafting material, independent of its embryologic origin. We believe these results challenge the currently accepted theories of bone graft dynamics and may lead to a change in the way clinicians approach bone graft selections for craniofacial surgery.     

Rat mandibular distraction osteogenesis: Part I. Histologic and radiographic analysis

The application of distraction osteogenesis to craniofacial surgery has altered the approach and treatment of congenital and acquired craniofacial defects. Although the histologic and ultrastructural changes associated with distraction osteogenesis have been described extensively, relatively little is known about the molecular regulation of this process. The elucidation of the molecular mechanisms of distraction osteogenesis has important clinical implications because it may facilitate the use of recombinant proteins or gene therapy to accelerate bone regeneration. Molecular analysis of distraction osteogenesis has been hindered by the use of large animal models in which only limited genetic information is available. In this study, a rat model of mandibular distraction osteogenesis is described. This report includes a pilot study (n = 50) to develop an appropriate distraction device and to determine the optimal placement of the osteotomy. The study subsequently included 80 animals, 35 of which were distracted at a rate of 0.25 mm per day for 6 days (1.5 mm total) and 35 that were distracted at a rate of 0.25 mm twice per day (3.0 mm total). These animals were killed at various time points (after latency and during the distraction and consolidation periods) and displayed histologic and radiographic findings of membranous bone distraction osteogenesis that were consistent with those in large ,animal and clinical models. In addition, five animals each were acutely lengthened 1.5 mm and 3.0 mm and demonstrated a fibrous nonunion. Furthermore, the utility of this model is demonstrated in the analysis of the molecular mechanisms of distraction osteogenesis by applying the polymerase chain reaction to total cellular RNA isolated from normal and distracted rat mandibles. In conclusion, it is believed that the rat model of distraction osteogenesis has significant advantages over traditional models, including decreased costs and facilitation of molecular analysis.     

Distraction osteogenesis for lengthening of the hard palate: Part II. Histological study of the hard and soft palate after distraction

To correct velopharyngeal incompetence, a new treatment concept was proposed in Distraction Osteogenesis for Lengthening of the Hard Palate: Part I (using lengthening of the hard and soft palate by distraction osteogenesis). Cephalometry and computed tomography showed successful elongation of the posterior hard palate with gradual calcification. Here the sequential use of fluorochrome markers (oxytetracycline, xylenol orange, DCAF [2,4-bis-N-N'-dicarboxymethyl aminomethyl fluorescein], and alizarin complexone) during the distraction and retention period is reported together with the histologic investigations using light and laser scan microscopy without prior demineralization. The experimental gap showed de novo osteogenesis in all dogs. The new bone was always in continuity with the original anterior and posterior palatal bone margins. It either bridged the experimental gap fully or left a small central zone of fibrous tissue, in which eventual ossification occurred. Several distinct zones could be distinguished: A small central zone was found with parallel strains of collagen fibers, oriented longitudinally in the direction of the distraction. Next to this zone a layer of undifferentiated mesenchymal precursor cells was seen in direct contact to newly formed bone. The next zone was coarse woven bone, showing a transition to mature lamellar bone through remodeling. No evidence of endochondral bone formation was found, i.e., all dogs showed exclusively intramembranous bone formation. The soft tissues showed no signs of alteration: in particular, there was no necrosis or scar formation. The soft tissues were not thinned but appeared to have followed the longitudinal displacement. In conclusion, gradual distraction osteogenesis of the hard palate could be a possible method for lengthening the palate to treat velopharyngeal incompetence.     

An adult case of extra-hepatic portal obstruction with bleeding from esophageal varices

PURPOSE: This study examined the use of a locking reconstruction bone plate/screw system for use in mandibular surgery. PATIENTS AND METHODS: All patients treated with a locking reconstruction bone plate/screw system for fractures of the mandible or continuity defects in an 18-month period were prospectively studied. Ease of use of the locking plate/screw system, characteristics of the fractures/defects, and complications were tabulated. RESULTS: One hundred two locking bone plates were placed in 84 patients. Most patients (n=75) were treated for fractures of the mandible; there were eight continuity defects and one case of mandibular narrowing. There were no cases of malocclusion or difficulties encountered in using the plate/screw system. Loss of fixation was encountered in only one patient. CONCLUSIONS: The use of a locking plate/screw system was found to be simple, and it offers advantages over conventional bone plates by not requiring the plate to be compressed to the bone to provide stability.     

Mandibular lengthening by gradual distraction: analysis using accurate skull replicas

Bone lengthening in the upper and lower extremities by gradual distraction has become an accepted procedure. We have used an extraoral device to lengthen the mandible in four patients with unilateral mandibular hypoplasia. Using an accurate skull replica, the proposed corticotomy line, intended direction of lengthening, and appropriate position for the screws were determined. Following distraction, a significant increase in the dimensions of the affected mandible was obtained in each case. In this series, accurate skull replicas proved very useful for defining the anatomy, for surgical simulation and for pre- and postoperative evaluation.     

Basement membrane of blood vessels during distraction osteogenesis

A canine model of distraction osteogenesis has recently been developed that permitted the evaluation of bone formation and its vascularization during bifocal callotasis. In this model, the authors examined the composition of the blood vessels during distraction osteogenesis of the mandible for laminin and for Type IV collagen, both constituents of the vascular basement membrane. At the fibrous distraction site, at the juncture of the free cortical surface and the regenerated bone, and at the abutting cortical surfaces at the distal margin of the defect, laminin and Type IV collagen were present in all vessels.     

Reconstruction of mandibular continuity defects in dogs using poly (L-lactide) mesh and autogenic particulate cancellous bone and marrow: preliminary report

PURPOSE: This study evaluated the reconstruction of continuity defects in the canine mandible using a poly [L-lactide] (PLLA) mesh tray and particulate cancellous bone and marrow (PCBM). MATERIALS AND METHODS: Eight adult dogs were divided into two groups of four dogs each. In group A, each dog had a tray fixed with stainless steel wires on each side of the mandibular stumps with the concave surface of the tray attached to the inferior border of the mandible (U-fixation). In group B, the concave surface was attached to the superior border (inverted U-fixation). Each tray was filled with PCBM from the ilium. After the operation, the dogs were radiographed, and specimens were examined histologically at 3-, 6-, and 12-month intervals. RESULTS: All of group A showed good clinical healing and the continuity of the mandibular bone was regained within 3 months postoperatively. However, fibrous tissue had invaded through the area above the tray, resulting in a poorly shaped alveolar ridges. In group B, the dogs showed good bony regeneration with well-shaped alveolar ridges. However, two animals in this group had partial exposure of the PLLA mesh tray into the oral cavity. CONCLUSION: It is suggested that a combination of the PLLA mesh and PCBM grafts might be a useful technique for functional reconstruction of the jaw bone, specifically using method A (U-fixation) as a technique to reconstruct continuity defects of the mandible, and method B (inverted, U-fixation) as a promising method for alveolar reconstruction to make wearing dentures possible.     

Juvenile xanthogranuloma of the iris with bilateral spontaneous hyphema

Lengthening of the mandible by gradual distraction and ear reconstruction using tissue expanders were performed on nine young patients (6-11 years old) with unilateral hemifacial microsomia. The technique holds promise for reconstruction of ear and mandible at the same time. This is essentially a pilot clinical project. A late follow-up of these patients is necessary.     

3-dimensional computed tomography with model preparation before mandibular reconstruction

Extended mandibular defects resulting from cancer resection are amenable to reconstruction with a free vascularized bone graft transplantation. Between 1992 and 1995, 12 patients were enrolled in a protocol including a preoperative 3D-CT used to develop a custom-made acrylic model of the mandible. Besides contributing to the assessment of tumor extension, 3D-CT helps determine the adequate limits of mandibular resection. 3D-CT has the advantage of providing the surgeon with a more familiar image of the mandible and the mandibular model, allowing better and quicker conformation of the bone flap. The graft can be shaped at the donor site before cutting its vascular pedicle, resulting in a shorter period of ischemia. This series demonstrated that preoperative mandibular modeling with 3D-CT helps improve functional and cosmetic results in mandibular reconstruction.     

A historical review of mental health services in Hong Kong (1841 to 1995)

OBJECTIVE: To review the experience of 1 microvascular surgeon during an 11-year period in performing 210 vascularized bone-containing free flaps for oromandibular reconstruction. DESIGN: Retrospective medical records review of patients who underwent primary and secondary oromandibular reconstruction with the use of vascularized bone free flaps. SETTING: Academic medical center. PATIENTS: A total of 201 patients underwent 210 composite free-flap reconstructions of the mandible for various disorders and with a range of bony and soft tissue defects. INTERVENTION: All patients underwent the microvascular transfer of vascularized bone flaps from the ilium, fibula, or scapula. In selected cases, 2 simultaneous free flaps were transferred to achieve an optimal bone and soft tissue reconstruction. Endosteal dental implants were used in 81 patients, with a total of 360 fixtures placed during these 11 years. MAIN OUTCOME MEASURES: The success of microvascular free tissue transfer, dental implant extrusion, and short- and long-term complications at the recipient and donor sites. RESULTS: Of the 210 mandibular reconstructions that were performed, 202 were successful in reestablishing mandibular continuity. Reexploration for vascular-related complications was done in 16 patients, 8 of whom were successfully treated, yielding an overall success rate of 96%. The overall success rate for endosteal dental implants was 92%. The implant success rate was 86% when the bone in which the fixtures were placed was irradiated postoperatively. The success rate was 64% in the 14 fixtures that were placed into previously irradiated bone. CONCLUSIONS: The success of the use of vascularized bone free flaps in restoring continuity to the mandible is clearly demonstrated in this series. There was an acceptable incidence of donor- and recipient-site complications that resulted in minimal long-term morbidity. The careful selection of a donor site(s) for oromandibular reconstruction allows for an optimal restoration of bony and soft tissue defects. Dental implants can be safely used in oromandibular reconstruction with a high level of success. Placing these implants during the initial surgery shortens the duration for achieving dental rehabilitation and enhances the success of the implants when postoperative radiotherapy is administered.     

Cloning, characterization, and chromosomal localization of human superillin (SVIL)

The specific aim of this study was to determine the response of alveolar bone after it was augmented vertically using distraction osteogenesis and subsequently loaded with implant restorations. Four dogs each had four implants placed horizontally into an edentulous mandibular quadrant and, after integration, a distraction osteogenesis device was fabricated in the laboratory. An osteotomy was made to allow the crest of the alveolar ridge to be distracted vertically. After 10 mm of vertical distraction, the device was stabilized with light cured resin. Following bone fill confirmation of the distraction gap at 10 weeks, two implants were placed into the ridges, one in distracted bone and one in nondistracted bone. After 4 months for implant integration, freestanding prostheses were fabricated. Crestal bone levels were evaluated throughout the period of function. Animals were sacrificed after 1 year of loading, for histologic evaluation of the bone. The vertical ridge augmentation averaged 8.85 +/- 1.05 mm after 10 weeks of healing following distraction, without change over 1 year of implant loading. Histologic examination showed that bone had formed between the distracted segments, creating an augmented ridge. The average thickness of the labial cortex in the distraction gap was significantly thinner than the lingual cortex in distracted bone and the lingual and labial nondistracted cortical bone. The presence of the dental implant did not significantly affect cortical bone thickness. Serial sections showed that implants remained integrated and functional without soft tissue inflammation. Dental implants placed into alveolar ridges augmented with the technique of distraction osteogenesis maintained bone and were functional for the length of this study.     

Vector of device placement and trajectory of mandibular distraction

The role of preoperative planning, the geometric changes, and the long-term effects of mandibular distraction have not been previously reported. This study included 10 patients who underwent unilateral (5 patients) or bilateral (5 patients) mandibular distraction. Preoperative, postdistraction, and yearly radiographs (panoramic, posteroanterior, and lateral cephalograms) were reviewed. Postdistraction follow-up ranged from 12 to 70 months. Postdistraction, the mandibles showed evidence of anticipated growth without relapse. This growth rate was variable and dependent on the genetic program of the native bone. Previously reported improvement in temporomandibular joint morphology was maintained in the long term. The resulting shape of the neomandible was most influenced by the vector of placement of the distraction device. When placed vertically, ramal elongation was observed. When placed horizontally, anterior projection of the mandibular body occurred. When placed obliquely, ramal and body elongation occurred with preservation of the gonial angle. After 2 to 5 years of follow-up, continued growth of the neomandible was observed.     

Mandibular reconstruction using a microvascular method in the transplantation of a fibular flap

The best results in mandibular reconstruction are achieved by transplantation of vascularised bone. This transplant has an own blood supply therefore its surviving is not influenced by the non-sterile environment of the oral cavity and the insufficient blood supply of the operated area (caused by scar or radiation). A new promising method for reconstruction of a wide segmented defect of the mandible is vascularised fibular flap transplantation. Eight consecutive patients treated with fibular flap transplantation in 1993 and 1994 were reviewed. Osteo- and osteo-cutan flaps were used for reconstruction of the composite tissue defects. The authors report on the surgical technique and their first experiences. The authors consider the application of the fibular flap the most successful procedure of all types of reconstruction of segmented mandibular defect.     

A comparison of vascularized and nonvascularized bone grafts for reconstruction of mandibular continuity defects

PURPOSE: This study compared vascularized and nonvascularized bone grafts for the reconstruction of segmental defects of the mandible. PATIENTS AND METHODS: The results in 39 patients having vascularized bone grafts (38 fibulas and one iliac crest) and 29 patients having nonvascularized bone grafts (26 iliac crest [22 corticocancellous block grafts, four cancellous bone grafts in a tray] and three rib grafts) for segmental mandibular reconstruction were evaluated in terms of overall success rate, total number of surgeries performed, total blood loss, total number of hospital days, and total number of hours in the operating room. RESULTS: Of 39 vascularized bone grafts, two failed (95% success rate), whereas of 29 nonvascularized bone grafts, seven failed (76% success rate). Failure for the nonvascularized bone grafts was closely correlated to the length of the defect. Nonvascularized bone graft patients underwent an average of one more surgical procedure for total reconstruction than vascularized bone graft patients, including osseointegrated implants. However, vascularized bone graft patients spent a mean of over 14 additional days in the hospital for all of their reconstructive procedures and an additional 3 hours in the operating room as compared with nonvascularized bone graft patients. Blood loss was similar in both groups (1,100 mL). Only 20% to 24% of patients in each treatment group have completed reconstruction to include osseointegrated implants. CONCLUSIONS: The success rate for vascularized bone grafting is high and is the treatment of choice when primary reconstruction is required, when the patient has been previously irradiated, or when simultaneous replacement of soft tissue is required. Vascularized bone grafts are also the treatment of choice for mandibular replacements over 9 cm in length. Nonvascularized bone grafts create a better contour and bone volume for facial esthetics and subsequent implant insertion, and may be the treatment of choice for secondary reconstruction of defects less than 9 cm in length.     

UDP-GlcNAc:Galbeta1-->3GalNAc (GlcNAc to GalNAc) beta1-->6N-acetylglucosaminyltransferase holds a key role on the control of CD15s expression in human pre-B lymphoid cell lines

Distraction osteogenesis has become an important technique to treat craniofacial skeletal dysplasia. In this study, the technique of maxillary distraction with a rigid external distraction device is presented. Cephalometric results in the first 14 consecutive patients are analyzed. The study sample consisted of 14 patients with various cleft types and maxillary hypoplasia treated with the rigid external distraction technique. Analysis of the predistraction and postdistraction cephalometric radiographs revealed significant skeletal maxillary advancement. All patients had correction of the maxillary hypoplasia with positive skeletal convexity and dental overjet after maxillary distraction. The morbidity for the procedure was minimal. Surgical and orthodontic procedures are thoroughly described.     

Use of activator appliances in pediatric patients treated with costochondral grafts for temporomandibular joint ankylosis: analysis of 13 cases

PURPOSE: The long-term outcomes and clinical results of costochondral transplants used for the treatment of condylar ankylosis of the mandible in children with and without application of postoperative activator appliances are evaluated and compared. MATERIALS AND METHODS: A nonrandomized, retrospective clinical study of 13 cases of condylar ankylosis (16 joints) of the mandible surgically treated during a 9-year period from 1988 to 1997 was performed. All 13 patients were treated by condylectomy and immediate costochondral rib grafts. Nine of these patients underwent long-term postoperative therapy using removable activator appliances. Four patients did not undergo activator therapy postoperatively. Casts, radiographs, photographs, computed tomography (CT) scans, magnetic resonance imaging (MRI) and 99Tc bone scans were used postsurgically to evaluate graft take, condylar growth and function, occlusion, and facial and condylar symmetry. RESULTS:The postoperative and long-term clinical results in both groups showed costochondral growth center transplants to be effective in restoring mandibular growth of the affected side. However, symmetry, arch coordination, correction of occlusal canting, mandibular deviation, facial growth, and prevention of reankylosis were obtained and better controlled only in those cases that underwent long-term orthodontic activator therapy postoperatively and were followed closely. CONCLUSIONS: Children with long-standing condylar ankylosis of the mandible and its resultant facial asymmetry and occlusal canting (secondary to a nonfunctional joint and maxillary compensation) treated with condylectomy and immediate costochondral rib graft reconstruction of the affected joint were treated more favorably when activators were used postsurgically. The patients that failed to comply with or continue activator therapy postsurgically developed complications relating to mandibular deviation, occlusal dysharmony, asymmetry and, in one case, reankylosis of the temporomandibular joint (TMJ).     

Frontofacial osteotomies, advancement, and remodeling by distraction: an extended application of the technique

The purpose of this clinical report is to present the distraction technique for advancement of the frontofacial skeleton as a unit. Our 14-year-old patient was diagnosed with Carpenter's syndrome and kleblattsch?del deformity at birth. At other centers the patient underwent corrective surgeries, including repeated fronto-orbital advancement in an attempt to correct the residual deformity. This has resulted in bony malunion and recurrent deformity, and it has left the patient with no available donor sites for harvesting of bone graft. The patient had class III malocclusion, severe midfacial and frontal deficiency, and relative turricephaly. We performed frontofacial osteotomies and placement of the distraction devices. Distraction of 20 mm was accomplished, correcting the exophthalmos and midface retrusion and producing class I dental occlusion. We conclude that distraction is an optional surgical method that can be applied in selected cases for advancement of the entire frontofacial skeleton.     

Mutation analysis and expression of the mottled gene in the macular mouse model of Menkes disease

OBJECTIVES: The purpose of this study was to evaluate the ability of two different panoramic imaging systems to produce cross-sectional images with accurate vertical dimensions of the posterior mandible. STUDY DESIGN: Three partially edentulous human cadaver mandibles were used for this study. On each mandible, three potential implant sites were arbitrarily identified in an area between the mental foramen and the ascending ramus. Each site was imaged using two different panoramic machines. Using each image, the mandible's outline, cortical thickness, and position of the mandibular canal were traced on clear acetate film. The mandibles were then sectioned at each site to serve as a gold standard. The cadaver sections and tracings (corrected for magnification) were measured, recording the overall mandibular height, distance from the crest of the ridge to the superior aspect of the mandibular canal, and the thickness of the cortical bone at the most inferior aspect of the mandible. RESULTS: There were no significant differences between either of the system's image measures and the gold standard when considering the distance between the crest and the mandibular canal. Differences were noted between the systems measures and the gold standard in the assessment of the cortical bone thickness and the overall mandibular height. CONCLUSIONS: Both imaging systems can be useful for vertical measurements of a potential implant site in the posterior mandible.