[Narrowing and sliding genioplasty procedure combined with mandibular outer cortex ostectomy technique to correct square jaw in short face].

OBJECTIVE: To evaluate the the feasibility and effectiveness of narrowing and sliding genioplasty combined with mandibular outer cortex ostectomy technique to reshape a square jaw in short face. METHODS: From July 2005 to October 2009, a total of 57 patients received narrowing and sliding genioplasty combined with mandibular outer cortex ostectomy procedure to correct square jaw in short face. All the patients had standard frontal and lateral cephalometric radiographs, panoramic radiographs, and were photographed preoperatively and postoperatively to assess their face contour. The alteration of mandibular angle, mental contour and width of lower face was observed for 6 to 24 months postoperatively. Questionnaires were used to assess the patients' satisfactory. RESULTS: It showed that the postoperative lower face had narrowed and become softer, slender and oval, with a slick mental region. The final aesthetic outcomes were quite satisfactory in all cases from both the view of surgeons and patients. CONCLUSIONS: Narrowing and sliding genioplasty combined with mandibular outer cortex ostectomy procedure could efficiently adjust the shape and position of chin to obtain a good proportion of the lower face, and to change square and short face to slender oval one by single operation in accordance with the fashionable aesthetics in orientals.

[Correction of low angel-square jaw with mandibular "V-Line" ostectomy combined with mandibular outer cortex ostectomy].

OBJECTIVE: To evaluate the feasibility of mandibular "V-Line" osteotomy combined with mandibular outer cortex osteotomy for correction of low angle-square jaw. METHODS: From Jul. 2005 to Nov. 2007, 31 patients with low angle-square jaw were corrected with mandibular "V-Line" osteotomy combined with mandibular outer cortex osteotomy. The patients were followed up for 6-24 months. Pre- and Post-operative standard images and X-ray cephalometric examination were used to assess the therapeutic effect. RESULTS: The wounds were healed primarily in all the 31 cases with no severe complication. The lower labial numbness was happened in 13 cases, which was recovered within 4 months. All the patients achieved esthetic improvement at the frontal and lateral view. The mandibular angle and the mandibular plane angle reached 110 degrees - 120 degrees and 25 degrees - 30 degrees after operation. The distance between the angles was decreased. CONCLUSIONS: The low angle-square jaw can be corrected satisfactorily with mandibular "V-Line" osteotomy combined with mandibular outer cortex osteotomy.

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.

[Study of reconstruction of mandibular condyle by transport distraction osteogenesis in monkeys].

OBJECTIVE: To evaluate the applicability and effectiveness of reconstruction of mandibular condyle by transport distraction osteogenesis in an animal model of rhesus monkeys. METHODS: Six adult rhesus monkeys were used in this study. Bilateral condyles and articular discs were extirpated, and the technique of transport distraction osteogenesis was performed to reconstruct the condyle. X-ray and CT scanning films were taken at various intervals. Two monkeys selected at random were sacrificed respectively at 4, 12 and 24 weeks after completion of distraction, and the newly formed condyles resulted from bony transport disc were harvested and processed for histologic examination. The removed condyles at surgery were used as normal control and prepared in the same manner. RESULTS: Open bite was seen in all animals postoperatively, and disappeared at the end of distraction. The shape and appearance of the bony transport disc was similar to original condyles at sacrifice. The articular cavity was filled with fibrous connective tissue and considerable cartilage cells were observed in the surface of the condyle stump. Bone regeneration was perfect in the distraction gap. CONCLUSION: A neocondyle with functional shape can be created by transport distraction osteogenesis, which suggested that this technique might be an alternative method in reconstruction of the condyle.

[Experimental study on the microcosmic changes of compressed premaxillary suture with laser scanning confocal microscopy].

OBJECTIVE: The aim of this experiment is to know whether active orthopedic appliance is rationale to do presurgical treatment and seek some regularities. METHODS: Laser scanning confocal microscopy and triple fluorochrome labeling in bone were used to observe and study detailed changes occurred in compressed suture systematically. RESULTS: Widened suture and broken fibres between the adjoining bones was observed at the 3rd week postoperatively. At the 3rd week hyperplasia of organic tissue components was also seen. At the 6 and 9th week there were no apparent differences among all groups no matter whether in control group or experimental groups. CONCLUSION: Retarding injury of compressed suture and surrounding tissue hyperplasia exists. With growth and development wounded suture will gradually assimilate to control group structurally and functionally.

[Effect of orthopedic premaxillary retrution on craniofacial development in animal model].

OBJECTIVE: To observe the whole process of cranio-maxillofacial development of an animal model with bilateral premaxillary clefts, after being exerted with premaxillary retro-pressing forces. METHODS: Experimental rabbits with premaxillary clefts and without clefts were exerted with retro-pressing forces respectively. Roentgenographic cephalometric analysis and different investigations of premaxillary suture were performed during the whole craniofacial development. RESULTS: The longitudinal cephalometric analysis showed that a temporary retarding effect of mid-facial growth existed. The hindrance of maxillary growth potentiality did not occur in spite of being exerted retro-pressing force as to this experimental extent. CONCLUSIONS: (1) Infant rabbit combined with the designed retro-pressing appliance is an ideal experimental model for quantitative study of active orthopedic treatment of protruding premaxilla. (2) Using active preoperative orthopedics to reposit the protruding premaxilla of bilateral cleft palate is a reasonable and effective approach.

[Mode of new bone formation following distraction osteogenesis in mandibular lengthening].

OBJECTIVE: To investigate the mode and influential factor of new bone formation following distraction osteogenesis in mandibular lengthening. METHODS: Corticotomy was performed on bilateral mandibles in twelve adult male goats. A custom-made distractor was used to lengthen the mandible at a rate of 1 mm/day for 10 days (total 10 mm elongation). Four goats were sampled respectively at 2, 4 and 8 weeks after completion of distraction. The lengthening mandibles were examined by roentgenography and histology. RESULTS: Newly formed callus was observed in the distraction gap after mandibular lengthening. The new bone exhibited intramembranous ossification generally, but cartilage islands could be found in the specimen that distractor loosed. CONCLUSION: The above findings indicate that the mode of new bone formation in mandibular lengthening following distraction osteogenesis appears to be intramembranous ossification and that endochondral ossification takes place in case distractor has loosened.

[Recombinant human BMP-2 accelerates bone formation of mandibular distraction osteogenesis in rabbits].

OBJECTIVE: To study the effects of rhBMP-2 on bone formation of mandibular distraction osteogenesis in rabbits. METHODS: Bilateral mandibular osteotomies were performed in 12 mature rabbits. 5 mg rhBMP-2 with the collagen carrier was implanted in the osteotomy site of one side of the mandibles. Only the collagen sponge was placed in the contra-lateral side as control. The mandibles of 8 rabbits were lengthened by 6mm using a custom-made distractor. At 4 weeks after the end of distraction, all animals were killed and the distracted calluses were harvested and processed for histological, scanning electron microscopic, as well as Ca/P ratio analysis. RESULTS: The regenerated bone was found in the distraction gap after mandibular lengthening. The mandibular side treated with rhBMP-2 had greater amounts of new bone formation and earlier mineralization than contra-lateral side (non-rhBMP-2 treated). CONCLUSION: Recombinant human BMP-2 appears to be able to accelerate bone formation of mandibular distraction osteogenesis in rabbits.