A comparison of stromal cell-derived factor-1 expression during distraction osteogenesis and bone fracture in the mandible.

Distraction osteogenesis (DO) has been a widely applied technique in orthopedics and craniofacial surgery. However, the exact molecular mechanism by which the mechanical stimulus is translated into biological signals is still poorly understood. In this study, we examined and compared the expression of stromal cell-derived factor-1 (SDF-1) during mandibular distraction osteogenesis and fracture in rats, respectively. Forty-eight male Sprague-Dawley rats were divided into 2 groups and received unilateral distraction osteogenesis and rigid internal fixation, respectively, after the osteotomy on the right mandible. The harvested mandibles were examined radiographically, histologically, and immunohistochemically. We found that the expression of SDF-1 was mainly detected in the osteoblasts and blood vessels, and there were more intensive expression of SDF-1 in DO zones than in bone fracture zones. The quantitative analysis by enzyme-linked immunosorbent assay showed that SDF-1 reached a greater peak and maintained a longer period of up-regulation in DO than in fracture healing (P < 0.05). These results suggest that the distraction procedure markedly promotes the high expression of SDF-1 which facilitates the induction of bone formation during DO.

Effects of sympathetic innervation loss on mandibular distraction osteogenesis.

Sympathetic nerve system has been proved to have important regulative effects to bone mass. However, the role of sympathetic nerve system in distraction osteogenesis (DO) is unclear. Here we show that the sympathetic nerve system plays an important role in mandibular DO. Thirty male Sprague-Dawley rats were divided into 2 groups at random. Right-side mandibular DO was performed on the 15 rats in control group (group A). Bilateral transection of cervical sympathetic trunk and right-side mandibular DO were performed on the 15 rats in the experimental group (group B). After operation, quantitative general observations, micro-computed tomography bone morphology analysis, and hematoxylin-eosin staining osseous tissue on new osteotylus in distraction gap were performed at consolidation time of 1, 14, and 28 days. SPSS 12.0 software package was used for statistical analysis. At 1 and 14 days of consolidation time, there was more continuous bone formation in the experimental group than that of the control group as determined by gross observation. Bone formation parameters including bone mineral density, bone volume-total volume ratio, bone trabeculae number as determined by micro-CT, and histological study of the test group were significantly higher than those of the control group (P < 0.05). No significant difference was noted between the 2 groups on consolidation time of 28 days. Our study suggested that the sympathetic innervation loss could improve mandibular DO and new bone formation, and the sympathetic nerve system might negatively regulate the process of DO.

Research on a novel rigid internal fixation system.

PURPOSE: The purpose of the present study was to evaluate the efficiency of fixation with a novel (bulge core type system) rigid internal fixation system. MATERIALS AND METHODS: Mandibular linear fractures were created artificially in dogs and fixed using a bulge core type system or a miniplate system in vitro. A 3-point load cell was used to contrast the fixation strength of the 2 systems in vitro. Histologic sections were used to analyze the healing of mandibular linear fractures and to contrast the efficiency of fixation of the 2 systems in vivo. Tetracycline-fluorescein staining technology was used to evaluate the bone healing speed in the mandibular fracture lines during bone healing. RESULTS: In vitro, the 3-point load cell showed that the fixation strength of the bulge core type system was greater than that of the miniplate system (P < .05). In vivo, the histologic sections and tetracycline-fluorescein staining showed that greater and quicker bony healing occurred using the bulge core type system (P < .05) and that the efficiency of fixation of the 2 systems was similar. CONCLUSION: Our results have shown that the bulge core type system can provide sufficient strength for mandibular linear fracture healing.

Accurate reconstruction of discontinuous mandible using a reverse engineering/computer-aided design/rapid prototyping technique: a preliminary clinical study.

PURPOSE: To improve the reconstructive surgical outcome of a discontinuous mandibular defect, we used reverse engineering (RE), computer-aided design (CAD), and rapid prototyping (RP) technique to fabricate customized mandibular trays to precisely restore the mandibular defects. Autogenous bone grafting was also used to restore the bony continuity for occlusion rehabilitation. PATIENTS AND METHODS: Six patients who had undergone block resection of the mandible underwent reconstruction using a custom titanium tray combining autogenous iliac grafts. The custom titanium tray was made using a RE/CAD/RP technique. A virtual 3-dimensional model was obtained by spiral computed tomography scanning. The opposite side of the mandible was mirrored to cover the defect area to restore excellent facial symmetry. A bone grafting tray was designed from the mirrored image and manufactured using RP processing and casting. The mandibular defects were restored using the trays in combination of autologous iliac grafting. An implant denture was made for 1 of the 6 patients at 24 weeks postoperatively for occlusion rehabilitation. RESULTS: The trays fabricated using this technique fit well in all 6 patients. The reconstructive procedures were easy and time saving. Satisfactory facial symmetry was restored. No severe complications occurred in the 5 patients without occlusion rehabilitation during a mean 50-month follow-up period. The reconstruction in the patient with occlusion lasted for only 1 year and failed eventually because of bone resorption and infection. CONCLUSIONS: Mandibular reconstruction was facilitated using the RE/CAD/RP technique. Satisfactory esthetic results were achieved. However, the rigidity of the cast tray could cause severe stress shielding to the grafts, which could lead to disuse atrophy. Therefore, some modification is needed for functional reconstruction.

Modified approach to construct a vascularized coral bone in rabbit using an arteriovenous loop.

The most important factor for the survival of thick three-dimensional tissues is the degree of vascularization. In this study, a modified arteriovenous loop (AVL) model was developed to prefabricate an axial vascularized tissue-engineered coral bone. In group A (n = 28), an arteriovenous fistula between rabbit femoral artery and vein was anastomosed to form an AVL. The AVL was placed in a coral block (6 x 8 x 10 mm (3)) as a vascular carrier. The complex was wrapped with polytetrafluoroethylene membrane and implanted subcutaneously. In group B (n = 20), there was no vascular carrier, and the same dimensional coral was directly implanted beneath inguinal skin. After 2, 4, 6, and 8 weeks, the rabbits were perfused with heparinized saline (for scanning electron microscopy), India ink (for histological examination), and ethylene perchloride (for vascular casts) via the abdominal aorta. In group A, histology showed that newly formed vasculature extended over the surfaces and invaded the entire coral blocks. The vascular density was significantly superior to that in group B. Vascular casts showed that new blood vessels robustly sprouted from the AVL. Scanning electron microscopy demonstrated that there were minute sprouting cavities in the vascular endangium. In this model, an axial vascularized coral bone could be effectively constructed.

Expert Consensus for the Treatment Algorithm for Navigationassisted Reconstruction of Maxillofacial Deformities.

Deformities of the maxillofacial region following trauma and ablative surgery are devastating and not uncommon. Reconstruction of such defects is a surgically challenging procedure. Conventionally, reconstruction of dental arch defects lacks preoperative customised planning and relies heavily on the surgeon experience to ensure optimum surgical outcomes. The restoration of the dental arch shape and function has taken precedence after an extensive tumour resection surgery, especially in the current age of technological advancement. Thus, personalised and accurate reconstruction of dental arch defects has become a new goal. Computer-assisted surgery, especially navigation-assisted surgery, has gained popularity of late, in reconstructing deformities and restoring facial symmetry, appearance and function in the maxillofacial region. This technology provides a clearer three-dimensional visualisation of the area of interest and its relationship with the adjacent vital structures. Together with preoperative virtual surgical planning, it allows more specific and accurate osteotomies, thus reducing the ischemia and total operating times substantially. The risk of complications is also minimised whilst improving the final surgical outcomes. The use of the intraoperative navigation system and other computer-assisted surgical techniques during surgery can significantly improve the precision of the reconstruction of dental arch deformities, and achieve personalised and functional reconstructive goals while enhancing the quality of life of patients postoperatively. The Society of Oral and Maxillofacial Surgery, Chinese Stomatological Association provides the present professional perspective and treatment protocol for navigation-guided reconstruction of dental arch defects, to allow standardisation of the technique while promoting its application among oral and maxillofacial surgeons.

Tisssue responses in corticotomy- and osteotomy-assisted tooth movements in rats: histology and immunostaining.

INTRODUCTION: The purpose of this histologic study was to examine underlying cellular responses to corticotomy- and osteotomy-assisted tooth movements. METHODS: Thirty-six rats were divided into 5 groups: corticotomy-assisted tooth movement (CO + TM), sham corticotomy without tooth movement (CO alone), osteotomy-assisted tooth movement (OS + TM), sham osteotomy without tooth movement (OS alone), and unassisted tooth movement (TM alone). Standard orthodontic springs were activated to produce mesial tooth movement. The rats were killed at 3, 21, and 60 days after activation for osteoclast and blood vessel counts, and immunostaining with proliferating cell nuclear antigen (PCNA), transforming growth factor beta 1 (TGF beta 1), vascular endothelial growth factor (VEGF), and osteocalcin were performed. RESULTS: The CO + TM group had significantly more osteoclasts at 3 days (P <0.005) compared with the OS + TM group. The alveolar bone surrounding the dental roots was replaced with multicellular tissue at 21 days in the CO + TM group but was intact in the OS + TM group with the exception of a distal distraction site. At day 21, immunostaining with PCNA, TGF beta 1, VEGF, and osteocalcin occurred at the mesial border of bone in the CO + TM group, whereas a diffuse pattern was observed in the distal distraction sites at 21 and 60 days in the OS + TM group. CONCLUSIONS: Corticotomy-assisted tooth movement produced transient bone resorption around the dental roots under tension; this was replaced by fibrous tissue after 21 days and by bone after 60 days. Osteotomy-assisted tooth movement resembled distraction osteogenesis and did not pass through a stage of regional bone resorption.

A novel strategy for prefabrication of large and axially vascularized tissue engineered bone by using an arteriovenous loop.

The repair of bone defects remains a major clinical challenge because none available reconstruction methods and biomaterials have been proved completely satisfactory. As a promising approach for bone regeneration, tissue engineered bone has become a technically feasible method to repair small to moderate sized bone defects in clinical practice, but it is difficult to repair large one, particularly when the recipient site is scarred by infection or radiation injury. Construction of large and vascularized tissue engineered bone may overcome the problems since vascularization is an essential prerequisite for the constructs to survive and integrate with existing host tissue. On the other hand, prefabrication large artificial bone in vivo bioreactor and axial vascularization by means of arteriovenous loop model in soft tissue have been proved to be feasible. Therefore, we hypothesize that combination of cells, solid scaffold, growth factors, and arteriovenous loop may eventually generate a large and vascularized tissue engineered bone flap in vivo bioreactor. Like vascularized autologous bone grafts, the new constructs could be transferred to the defect site by using microsurgical techniques. The strategy would facilitate clinical translation in bone tissue engineering and offer new therapeutic strategies for reconstruction of extended bone defects if the hypothesis proved to be practical.

Long-term results of mandibular reconstruction of continuity defects with fibula free flap and implant-borne dental rehabilitation.

PURPOSE: This study evaluated the retrospective outcomes of implant-borne dental rehabilitation in patients with mandibular defects reconstructed with a fibula free flap. MATERIALS AND METHODS: Patients with segmental mandibular defects were enrolled in this cohort study. Defects in these patients were caused by oral neoplasm, trauma, and osteoradionecrosis. The patients were treated with a fibula free flap procedure and dental implant-borne prostheses between 1988 and 2010. Clinical and radiographic data were evaluated; Kaplan-Meier survival analysis and Poisson regression analysis were used to evaluate implant survival parameters. The statistical significance (α = .05) of the results was determined. RESULTS: Seventy-four patients were selected in this study. All patients were available for continuous follow-up. Nine patients (12.1%) developed fibular graft complications postoperatively: 3 in donor sites and 6 in recipient sites. One hundred ninety-two implants were inserted, and 18 implants failed (9.3%). Overall implant survival in patients was 90.1%, 83.1%, and 69.3% after 5, 10, and 20 years, respectively. In 152 implants, probing depth (PD) ranged from 2 to 3 mm. In 31 implants, PD was greater than 5 mm. In 9 implants, PD was greater than 7 mm. The highest implant failure rates were expected for men (odds ratio [OR] = 2.948; 95% confidence interval [CI], 1.10 to 7.85; P = .031), patients receiving primary fibula free flap reconstruction (OR = 3.696; 95% CI, 1.16 to 11.73; P = .027), and patients receiving radiotherapy (OR = 5.269; 95% CI, 1.40 to 19.7; P = .014). CONCLUSION: Fibula free flap procedures and implant-borne prostheses proved to be reliable approaches for rehabilitation of mandibular defects and oral function. The overall postoperative fibula free flap and peri-implant complication rates proved to be low. Regular follow-up visits and proper oral hygiene maintenance contributed to the long-term successful treatments.

Long-Term Results of Mandibular Reconstruction of Continuity Defects with Fibula Free Flap and Implant-Borne Dental Rehabilitation.

Purpose: This study evaluated the retrospective outcomes of implant-borne dental rehabilitation in patients with mandibular defects reconstructed with a fibula free flap. Materials and Methods: Patients with segmental mandibular defects were enrolled in this cohort study. Defects in these patients were caused by oral neoplasm, trauma, and osteoradionecrosis. The patients were treated with a fibula free flap procedure and dental implant-borne prostheses between 1988 and 2010. Clinical and radiographic data were evaluated; Kaplan-Meier survival analysis and Poisson regression analysis were used to evaluate implant survival parameters. The statistical significance (α = .05) of the results was determined. Results: Seventy-four patients were selected in this study. All patients were available for continuous follow-up. Nine patients (12.1%) developed fibular graft complications postoperatively: 3 in donor sites and 6 in recipient sites. One hundred ninety-two implants were inserted, and 18 implants failed (9.3%). Overall implant survival in patients was 90.1%, 83.1%, and 69.3% after 5, 10, and 20 years, respectively. In 152 implants, probing depth (PD) ranged from 2 to 3 mm. In 31 implants, PD was greater than 5 mm. In 9 implants, PD was greater than 7 mm. The highest implant failure rates were expected for men (odds ratio [OR] = 2.948; 95% confidence interval [CI], 1.10 to 7.85; P = .031), patients receiving primary fibula free flap reconstruction (OR = 3.696; 95% CI,1.16 to 11.73; P = .027), and patients receiving radiotherapy (OR = 5.269; 95% CI, 1.40 to 19.7; P = .014). Conclusion: Fibula free flap procedures and implant-borne prostheses proved to be reliable approaches for rehabilitation of mandibular defects and oral function. The overall postoperative fibula free flap and peri-implant complication rates proved to be low. Regular follow-up visits and proper oral hygiene maintenance contributed to the long-term successful treatments.

Local injection of substance P increases bony formation during mandibular distraction osteogenesis in rats.

Substance P is a neuropeptide that is distributed in those sensory nerve fibres that innervate the medullary tissues of bone. It is a potent accelerator of proliferation and differentiation of osteoblasts in vitro. However, its capacity for promoting repair of mandibular defects is not known. We have investigated the osteogenic effects of local injections of substance P during mandibular distraction osteogenesis in rats. Twenty Sprague-Dawley rats were randomly assigned to 2 groups (n = 10 in each): substance P 10(-7) mmol/l in normal saline 0.2ml was injected into the experimental group, and saline alone into the controls. The mandibular distraction rate was 0.2mm every 12hours for 10 days. Daily injections of substance P or saline were given during the distraction period. Regeneration of bone was assessed quantitatively on days 15 and 29 using microcomputed tomography (microCT), and histological analysis. The rate of bony union in the group treated with substance P was significantly higher than that in the saline alone group on day 29 (p=0.001) The microCT images and quantitation showed more callus and more mature cortical bone when substance P was given than with control. Histological examination showed that cartilaginous tissues had formed in the middle of the distraction gaps in both groups. Bony bridges were seen only in the substance P group at the final time point (day 29). Injection of substance P into the gap of a rat mandible during mandibular distraction improved formation of good-quality bone and accelerated bony union.

The adjuvant use of stromal vascular fraction and platelet-rich fibrin for autologous adipose tissue transplantation.

Autologous adipose transplantation is rapidly gaining popularity for the restoration of soft tissue defects and lipoatrophy as well as for aesthetic improvements (e.g., facial reconstruction and rejuvenation). However, the current technique is crude that suffers from serious demerits, particularly the long-term unpredictability of volume maintenance due to resorption of the grafted adipose tissue and limited adipogenesis. We hypothesized that the adjuvant use of patient-derived adipose stromal vascular fraction (SVF) and platelet-rich fibrin (PRF) may enhance the overall outcome of autologous fat grafting in plastic and reconstructive surgery. Autologous SVF, with a mean cell number of (4.8±3.79)×107 cells/mL and a mean cell viability of 71.8%, and autologous PRF, with sustained release of multiple angiogenic growth factors, were created before surgical use. The following adipose tissue implants were injected subcutaneously into a rabbit ear's auricula according to the following study design: 2 mL adipose granules and 0.2 mL normal saline solution (AG+NS group), 2 mL adipose granules and 0.2 mL SVF (AG+SVF group), 2 mL adipose granules and 0.2 mL PRF (AG+PRF group), or 2 mL adipose granules combined with 0.1 mL SVF and 0.1 mL PRF (AG+SVF+PRF group). Histological examinations showed that the implanted adipose granules were well engrafted in the AG+SVF+PRF group, with a higher microvessel density 4 weeks postimplantation compared with the other three groups (p<0.01). Twenty-four weeks postimplantation, the resorption rates of implanted tissue in each group were 49.39%±9.47%, 27.25%±4.37%, 36.41%±8.47%, and 17.37%±6.22%, respectively, and were significantly different (p<0.01). The results demonstrated that the efficacy of adipose tissue implantation can be enhanced by using autologous PRF and SVF as therapeutic adjuvants, offering a clinically translatable strategy for soft tissue augmentation and reconstruction.

Recruitment of exogenous mesenchymal stem cells in mandibular distraction osteogenesis by the stromal cell-derived factor-1/chemokine receptor-4 pathway in rats.

Distraction osteogenesis is widely used in orthopaedic and craniofacial surgery. However, its exact mechanism is still poorly understood. The purpose of this study was to find out whether there is systemic recruitment of mesenchymal stem cells (MSC) to the neocallus in the distraction gap by the stromal cell-derived factor-1 (SDF-1)/CXC chemokine receptor 4 (CXCR4) axis during osteogenesis. We examined the migration of MSC towards a gradient of SDF-1 in vitro. We also transplanted MSC labelled with green fluorescent protein (GFP) intravenously, with or without treatment with CXCR4-blocking antibody, into rats that had had unilateral mandibular distraction osteogenesis, and investigated the distribution of cells labelled with GFP in the soft callus after 24 h. We found that SDF-1 facilitated the migration potency of MSC both in vitro and in vivo, and this migration could be inhibited by AMD3100, an antagonist of CXCR4, and promoted by local infusion of exogenous SDF-1 into the distraction gap. This study provides a new insight into the molecular basis of how new bone is regenerated during distraction osteogenesis.

Local injection of nerve growth factor via a hydrogel enhances bone formation during mandibular distraction osteogenesis.

OBJECTIVE: The objective of this study was to evaluate the effects of the injectable NGF-carrying collagen/nano-hydroxyapatite/alginate hydrogel on the bone formation in a rabbit mandibular distraction osteogenesis model. STUDY DESIGN: Thirty-five New Zealand white rabbits underwent bilateral madibular distraction osteogenesis at a rate of 0.75 mm/12 h for 6 days. The rabbits were divided into 4 groups: group 1 received injections of collagen/nano-hydroxyapatite/alginate hydrogel containing hNGFß; groups 2, 3, and 4 received injections of hNGFß, Col/nHA/Alg hydrogel, and saline, respectively. The injections were performed on both sides of the mandible at the end of the lengthening phase. All the animals were killed at a consolidation time of 14 days. RESULTS: No difference in regenerate bone dimensions was observed among the 4 groups. Bone mineral density, the maximum load, and the bone volume/total volume of the new bone in the distraction gap in group 1 was significantly greater (P < .05) than in the other 3 groups. CONCLUSIONS: Application of the Col/nHA/Alg hydrogel as an NGF delivery during the consolidation phase of distraction osteogenesis increased regeneration and new bone formation.

A new hypothesis of mechanisms of traumatic ankylosis of temporomandibular joint.

Temporomandibular joint (TMJ) ankylosis is a disease that severely affects the human health. Although it is well known that trauma is the most common cause of TMJ ankylosis, the mechanisms by which the traumatic TMJ ankylosis develops are unclear. The existing hypothesis is not convincing in explaining the genesis of traumatic TMJ ankylosis. We make a hypothesis that the distraction osteogenesis (DO) of the lateral pterygoid muscle combining with the dislocated and damaged disc is an important factor in genesis of traumatic TMJ ankylosis. If this hypothesis is verified, it will be helpful for the prevention of traumatic TMJ ankylosis and change the principle of management of sagittal fracture of mandibular condyle (SFMC).

Morphological evaluation of temporomandibular joint after open and closed treatment of type B diacapsular condylar fractures in sheep.

The incidence of diacapsular fracture of the mandibular condyle (DFMC) has increased in recent years. However, the specific modality of treatment which would provide maximum benefit and good results for adult patients of DFMC has been controversial. To evaluate and compare morphological changes of temporomandibular joint (TMJ) after open and closed treatments for DFMC, a sheep model of a type B DFMC was created by osteotomy. Eight sheep models of type B DFMC were randomly divided into 2 groups to receive closed treatment (Group 1) and open reduction and internal fixation (ORIF, Group 2), respectively, and morphological changes of TMJ were scored according to the radiological and anatomical criteria of scoring and compared between the 2 groups. Compared with Group 1 animals treated by the closed method, Group 2 animals treated with ORIF received significantly lower scores for morphological changes 12 weeks after treatment. We conclude that ORIF is more efficient than the closed functional treatment in restoring morphology of TMJ to treat type B DFMC.

Dentists' role in treating facial injuries sustained in the 2008 earthquake in China: how dental professionals can contribute to emergency response.

BACKGROUND: A major earthquake struck Sichuan province, China, on May 12, 2008, and the authors were involved in the medical response to the disaster in Jiangyou City, an area hard-hit by the quake. In this article, they analyze data about the earthquake-related facial injuries and assess dentistry's role in treating them. METHODS: This descriptive study included review of medical records for 4,582 patients with earthquake-related trauma at eight hospitals in Jiangyou, a city severely affected by the earthquake, for the day of the disaster and the 14 days immediately afterward. RESULTS: Of the 4,582 patients, 408 (8.9 percent) sustained a total of 482 facial injuries. The dental team treated patients with facial injuries and others who needed care. CONCLUSIONS: Facial injuries constitute a significant portion of earthquake-related trauma, and dentists therefore are an important part of the medical team that deals with such trauma. Dentists are a reliable force in the medical response to earthquakes and other disasters. CLINICAL IMPLICATIONS: The dental team should play an important role in disaster response. Establishing oral and maxillofacial surgeon (OMS)/dentist reserves and active leagues that use OMSs' and general dentists' offices as bases can help improve disaster response.

Reconstruction of curved mandibular angle defects using a new internal transport distraction device: an experiment in goats.

A new internal distraction device, comprising a square-bodied bow, a transport plate, a traction mechanism, and two stabilisers, was developed to allow transportation of bone around an arc. Eight adult goats were studied. A curved mandibulectomy 3cm long was made on the mandibular angle. The distractor was implanted to restore the defect. The bone was distracted at a rate of 1mm per day after a 5-day latent period. Distraction lasted 25 to 32 days. Curvilinear distraction was successful in six of the eight goats. After consolidation periods of four or eight weeks, smooth curved bone masses were restored in the distracted areas. Radiographically, there was considerable bone density in the distraction area and opaque columns streamed in the direction of distraction. Histological examination showed membranous bony regeneration in the restored bone. These results suggest that restoration of curved bone defects using the new internal transport distraction device was feasible in goats.

Matrix metalloproteinase and its inhibitor in temporomandibular joint osteoarthrosis after indirect trauma in young goats.

Our aim was to examine the change in expression of matrix metalloproteinases (MMP-13), matrix metalloproteinases-3 (MMP-3), and tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) in the articular cartilage of goats with experimentally-induced osteoarthrosis of the temporomandibular joint (TMJ) at various times. Osteoarthrosis was induced in 20 goats in the bilateral TMJ and 5 goats acted as controls. There were 5 goats in each group, and a group was killed at 7 days, and 1, 3, and 6 months postoperatively. The samples were collected, and the joints evaluated histologically. Immunofluorescence was used to detect the presence of MMPs and TIMP-1 in the articular disc and condylar cartilage. The ultrastructure of the articular disc and condylar surface at 1 month was examined with scanning electron microscopy (SEM). Osteoarthrosis of the TMJ progressed gradually over time. MMP-13, MMP-3, and TIMP-1 were expressed strongly in the TMJ soon after injury; MMP-13 became gradually weakened, and MMP-3 strengthened later. None of these were expressed in the normal condyle. After a month the surface of the arthrotic condyle was uneven, and the underlying collagen fibrils were exposed in irregular fissures on the surface. The secretion of TIMP-1 was related closely to the changes of MMPs during osteoarthrosis of the TMJ. The unbalanced ratio between them caused degradation of the matrix of the cartilage and might be the cause of osteoarthrosis of the TMJ.

Transport distraction osteogenesis using nitinol spring: an exploration in canine mandible.

Some experiments in rabbits have presented the potential feasibility of using shape memory alloy spring for continuous distraction osteogenesis. To confirm the effectiveness of such method, we established canine models for the exploratory experiments of transport distraction osteogenesis using nitinol springs. Simple devices, including an internal 60-mm long sinusoid-shaped nitinol springs were used in the study. All dogs needed only one operation. In the operation, osteotomy was performed to create a 40-mm unilateral segmental mandibular body defect and a tooth-bearing transport bone disc. After reconstructive fixation of the remnant mandible, the spring was constricted and anchored across the distraction gap to activate transport distraction immediately. At the second experimental stage, an ePTFE sheet was further fixed to protect the defect and distraction gap before closing the incision. Control dogs underwent the same operation except for anchoring of the spring to examine the spontaneous bone regeneration. Automatic bone transportation, as a gradual slowdown process, was observed under the effect of the spring. The transport disc could get to the opposite side of the defect, or stopped halfway when ePTFE sheet intervened. Mandibular reconstruction was achieved in all these dogs and better in dogs with sheet protection. No integrated bone mass was found in the defect of control dogs. The study further proves that continuous distraction osteogenesis using nitinol springs is a practical technique, although the devices need more improvement for better control of the process of distraction and the quality of regenerated bone.