Etiological factors associated with temporomandibular joint disorder - study on animal model.

The etiology of temporomandibular disorder (TMD) is multidimensional: biomechanical, neuromuscular, bio-psychosocial and biological factors may contribute to the disorder. The main objectives of our study were investigation and analysis of the degree of involvement for several presumptive etiological factors of TMD: biomechanical stress (BS), estrogen hormones (EH) and emotional stress (ES). Six groups (n=10) of mature female Wistar rats were included in the study. Single presumptive etiological factor was applied in three groups (BS, EH and ES groups) and also association of presumptive etiological factors were applied in two groups (BSEH and BSES groups). No etiological factor was applied for the control group. Animals were sacrificed after a 60 days period and histological analysis of the temporomandibular joint (TMJ) tissues was performed. The changes in the mandibular cartilage, articular disc, temporal bone and synovial tissue were observed under optical magnification and quantified. All samples developed changes in the thickness of the condylar cartilage comparing to control group. The reduction was highly statistical significant for the EH, ES and BSES groups (p<0.001) and statistical significant for the BS and BSEH groups (p<0.05). The most important modifications with severe cartilage thickness reduction have been obtained in case of BSES group. In conclusion, biomechanical, emotional stress and estrogens can be considered as possible etiological factors in TMD.