Acute Bilateral Dislocation of the Temporomandibular Joint With Left Old Zygomaticomaxillary Complex Fracture Treated With Coronoidectomy Authors.

The majority of various types of temporomandibular joint dislocation can be easily reduced to normal position through nontraumatic procedures. We present a rare case of temporomandibular joint dislocation with a left old zygomaticomaxoid complex fracture in a 48-year-old hemiplegic male. Due to the lock-in state of dislocated coronoid process and deformed zygomaticomaxoid complex, this type of dislocation combined with an old fracture is rare and difficult to reduce with conservative therapy. Therefore, coronoidectomy was performed to release the lock and reduce the condylar.

Squamous Cell Carcinoma Arising From Odontogenic Cyst Epithelium or Oral Mucosa Epithelium After Marsupialization of Odontogenic Radicular Cyst in Posterior Mandible?

Squamous cell carcinomas (SCCs) are common malignant tumors in the oral and maxillofacial region. However, SCCs secondary to marsupialization of odontogenic radicular cysts are extremely rare. The authors report an unusual case of a 43-year-old male presented with dull pain in the right molar region of the mandible without numbness of lower lips, who had a long history of smoking, alcohol consumption, and betel nut chewing. Computerized tomography revealed a round well-defined unilocular radiolucent at the apex of lower right premolars, 2 nonvital teeth. The clinical diagnosis was the radicular cyst of the right mandible. The patient was initially treated with root canal therapy of the teeth followed by marsupialization with a mandibular vestibular groove incision. While the patient did not follow the instruction of irrigation of the cyst and had no regular follow-up. The reexamination of computerized tomography indicated a round well-defined unilocular radiolucent at the apex of lower right premolars and filled with a soft tissue without clear boundary with buccal muscles at 31 months follow-up. There were no masses or ulcer around the mandibular vestibular groove incision and the patient had no sign of numbness of lower lips. The clinical diagnosis was the radicular cyst of right mandible with infection. A curettage was performed. However, the pathologic diagnosis was well-differentiated SCC. An extended radical surgical resection including segmental resection of the right mandible was performed. The histopathology was well-differentiated SCC without the cyst epithelium and invasion of bone, which can be distinguished from primary intraosseous SCC. The case indicates that marsupialization performed in patients with a history of smoking, alcohol consumption, and betel nut chewing, has a risk of suffering from oral SCC.

Sensory Nerves Affect Bone Regeneration in Rabbit Mandibular Distraction Osteogenesis.

Objectives: To investigate the effects of inferior alveolar nerve on new bone formation in rabbit mandibular distraction osteogenesis. Methods: 20 New Zealand White rabbits underwent bilateral distraction osteogenesis with a rate of 1 mm/day. The inferior alveolar nerve of one side was resected under the surgical microscope, with the inferior alveolar vascular intact. The contralateral side received sham operation. The rabbits were sacrificed at consolidation time of 28 days. The regenerate callus underwent radiograph examination, dual-energy X-ray absorptiometry, haematoxylin and eosin staining and histomorphometric analysis. A paired t-test was performed using SPSS 16.0 software package. Results: The BMD of the new bone in the distraction gap on the denervation side of mandibular was significantly lower (P<0.05) than on the control side. The histological investigation showed that the bone trabeculae were dis-arrayed containing dispersed cartilage cells on the denervation side, whereas the bone trabeculae were orderly with rich blood vessels and no cartilage cell on the control side. Both new bone volume and the thickness of new trabeculae were significantly lower on the denervation side than on the control side (P < 0.05). Conclusion: The loss of the sensory nerves could result in a decrease of the new bone quality during the mandibular distraction osteogenesis.

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.

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.

Sympathetic denervation-induced MSC mobilization in distraction osteogenesis associates with inhibition of MSC migration and osteogenesis by norepinephrine/adrb3.

The sympathetic nervous system regulates bone formation and resorption under physiological conditions. However, it is still unclear how the sympathetic nerves affect stem cell migration and differentiation in bone regeneration. Distraction osteogenesis is an ideal model of bone regeneration due to its special nature as a self-engineering tissue. In this study, a rat model of mandibular distraction osteogenesis with transection of cervical sympathetic trunk was used to demonstrate that sympathetic denervation can deplete norepinephrine (NE) in distraction-induced bone callus, down-regulate ß3-adrenergic receptor (adrb3) in bone marrow mesenchymal stem cells (MSCs), and promote MSC migration from perivascular regions to bone-forming units. An in vitro Transwell assay was here used to demonstrate that NE can inhibit stroma-derived factor-1 (SDF-1)-induced MSC migration and expression of the migration-related gene matrix metalloproteinase-2 (MMP-2) and downregulate that of the anti-migration gene tissue inhibitor of metalloproteinase-3 (TIMP-3). Knockdown of adrb3 using siRNA abolishes inhibition of MSC migration. An in vitro osteogenic assay was used to show that NE can inhibit the formation of MSC bone nodules and expression of the osteogenic marker genes alkaline phosphatase (ALP), osteocalcin (OCN), and runt-related transcription factor-2 (RUNX2), but knockdown of adrb3 by siRNA can abolish such inhibition of the osteogenic differentiation of MSCs. It is here concluded that sympathetic denervation-induced MSC mobilization in rat mandibular distraction osteogenesis is associated with inhibition of MSC migration and osteogenic differentiation by NE/adrb3 in vitro. These findings may facilitate understanding of the relationship of MSC mobilization and sympathetic nervous system across a wide spectrum of tissue regeneration processes.

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.

Nerve growth factor injected systemically improves the recovery of the inferior alveolar nerve in a rabbit model of mandibular distraction osteogenesis.

Our aim was to find out if nerve growth factor (NGF) injected systemically could improve the recovery of the inferior alveolar nerve in a rabbit model of mandibular distraction osteogenesis. We used 48 New Zealand white rabbits that were treated with bilateral distraction osteogenesis at a rate of 0.5mm/12h for 10 days. Immediately postoperatively, NGF or sodium chloride 0.6 µg/day was injected intramuscularly for 20 days. At the end of distraction and after consolidation times of 1, 2, and 4 weeks, the inferior alveolar nerves were evaluated histologically and histomorphometrically. Histologically, at 2 and 4 weeks there was less myelin debris, and more regenerating axons were present, in the NGF than the control groups. The density of myelinated axons was significantly greater in groups with NGF than controls at 2 and 4 weeks (p<0.05). NGF given systemically can accelerate the recovery of the inferior alveolar nerve in rabbits after mandibular distraction osteogenesis, and is a promising treatment option for neurological complications of mandibular distraction osteogenesis.