Histological assessment of intra-articular versus intra-peritoneal betamethasone L.A on tempromandibular joint arthritis in rat

Background: Pain and dysfunction of the tempromandibular joint (TMJ) are major clinical problems, especially, in arthritis. The aim of this study was to compare the effect of intra-articular (IA) versus intra-peritoneal (IP) injection of betamethasone long acting on TMJ arthritis in rat. Materials and Methods: In this experimental study, an inflammation in the left TMJ of 29 rats was induced by injection of complete Freund’s adjuvant. After 1 week, rats were divided into 5 groups: Group A: Rats of this group were not treated (n = 5); groups B, C: Rats were injected with a single dose of ½ mg/kg betamethasone L.A IA (n = 6); groups D, E: Rats received a single dose of ½ mg/kg betamethasone L.A IP (n = 6). Rats in groups B and D after 1 week, and in groups C, E and A, at 4 weeks after drug injection were sacrificed. Severity of inflammation was scored from 1 to 11 according to synovial hyperplasia, vascularity, fibrin deposits, and synovial adhesion. Results were analyzed by using Kruskal-Wallis and Mann-Whitney (P < 0/05 was considered significant). Results: Significant differences were existed between groups B, D (P = 0/004) and groups C, E (P = 0/002). The least severity of Inflammation and also evidence of resorbtion in condylar head was seen in group C. Conclusion: The best therapeutic response was seen with IA injection of betamethasone L.A in comparison with IP injection.