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

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. 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). 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. The best therapeutic response was seen with IA injection of betamethasone L.A in comparison with IP injection.