[Expression and significance of nitric oxide synthase in mandibular distraction osteogenesis of canine].

OBJECTIVE: To investigate the expression and significance of nitric oxide synthase (NOS) during mandibular distraction osteogenesis and bone trauma healing, to futher study the mechanism of distraction osteogenesis. METHODS: Twenty-eight adult dogs were randomly divided into DO group (12 dogs), acutely lengthening group (12 dogs) and control group (4 dogs). Immunohistochemical examination were carried out to test the expression of NOS during the sixth day in distraction period, the second and eighth week of consolidation. RESULTS: In DO group infiltration of inflammatory cell was found in the distraction gap, more red blood cells (RBC) leak out around vascellum and matrix in the sixth day in distraction period. The expression of local iNOS (inducible NOS) and eNOS (endothelinal NOS) in DO gruoup and acutely lengthening group was higher than that in the control group (P < 0.05), the expression of local iNOS and eNOS in acutely lengthening group was lower than that in DO group (P < 0.05) in the early of distraction period and the consolidation. The expression of local iNOS and eNOS was no statistic difference between three groups (P > 0.05) in the eighth week of consolidation. CONCLUSION: NOS as a sensitive index of tissue trauma are highly expressed, and RBC was found leaking out in the early of distraction, indicating that micro-trauma to some extent may occurr during DO procedure, the micro-trauma may be one of the significant factors which increasing regeneration of bone during DO.

[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.