Three‐dimensional analysis of jaw kinematic alterations in patients with chronic TMD – disc displacement with reduction

Summary The study investigated whether chronic TMD patients with disc displacement with reduction (DDR), performing non‐assisted maximum jaw movements, presented any changes in their mandibular kinematics with respect to an age‐matched control group. Moreover, it was examined whether jaw kinematics and a valid clinic measure of oro‐facial functional status have significant associations. Maximum mouth opening, mandible protrusion and bilateral laterotrusions were performed by 20 patients (18 women, 2 men; age, 18–34 years) and 20 healthy controls (17 women, 3 men; age, 20–31 years). The three‐dimensional coordinates of their mandibular interincisor and condylar reference points were recorded by means of an optoelectronic motion analyser and were used to quantitatively assess their range of motion, velocity, symmetry and synchrony. Three functional indices (opening–closing, mandibular rototranslation, laterotrusion – right and left – and protrusion) were devised to summarise subject's overall performance, and their correlation with the outcome of a clinical protocol, the oro‐facial myofunctional evaluation with scores (OMES), was investigated. TMD patients were able to reach maximum excursions of jaw movements comparable to healthy subjects’ performances. However, their opening and closing mandibular movements were characterised by remarkable asynchrony of condylar translation. They had also reduced jaw closing velocity and asymmetric laterotrusions. The functional indices proved to well summarise the global condition of jaw kinematics, highlighting the presence of alterations in TMD‐DDR patients, and were linearly correlated with the oro‐facial functional status. The jaw kinematic alterations seem to reflect both oro‐facial motor behaviour adaptation and a DDR‐related articular impairment.