Temporomandibular joint dysfunction and systemic joint laxity.

The purpose of this thesis was to study an inherited disposition, systemic joint laxity, in patients with temporomandibular joint (TMJ) dysfunction. The importance of systemic joint laxity for TMJ dysfunction compared with other supposed etiological factors, such as bruxism and jaw trauma, was analysed in TMJ patients and in non-patient groups. Collagen distribution and mitral valve function were investigated in hypermobile TMJ patients and normal controls. General joint mobility was assessed in 360 participants. Comparing 74 female craniomandibular dysfunction (CMD) patients with 73 controls of the same sex and age, more hypermobile individuals were found in the patient group. Patients with TMJ dysfunction had significantly more hypermobile joints than other patients at a clinic for CMD patients. A multiple stepwise regression analysis established that hypermobility was a more important factor than bruxing for TMJ dysfunction. Trauma to the head and jaw was significantly correlated to TMJ dysfunction only in non-hypermobile patients. TMJ patients had significantly more musculoskeletal complaints than other CMD patients or controls. A non-patient investigation comprising about 200 adolescents showed the females to be significantly more hypermobile than the males. Another indication of a systemic disposition in hypermobile TMJ patients compared with controls was more insufficient mitral valve function in an echocardiographic investigation of 10 hypermobile TMJ patients and 10 normal controls. Skin biopsy revealed lower values of total collagen and a higher ratio of collagen type III to III + I in TMJ patients than in normal controls.