Temporomandibular joint mobility assessment: a comparison between four methods.

Temporomandibular joint (TMJ) mobility is assessed in different ways. Measurement of the interincisal distance in maximal mouth opening added to the vertical overlap of the dentition, i.e. linear mouth opening (LMO); measurement of angular displacement of the mandible relative to the cranium at maximal mouth opening, i.e. angle of mouth opening (AMO); assessment of the condylar position relative to the articular eminence performed on transpharyngeal radiographs in maximal mouth opening, i.e. condylar mobility (CM); measurement of angular displacement of the mandible at maximal mouth opening relative to the closed mouth position of the mandible, assessed on transpharyngeal radiographs in maximally opened and in closed mouth position, i.e., radiographic angle of mouth opening (RAMO). To compare these TMJ mobility assessment methods and to analyse the relationship between LMO, AMO and mandibular length (ML), 28 healthy volunteers (13 females, 15 males), mean age 29-6 years (range 21-41) with a symmetrical mouth opening pattern were assessed. LMO, AMO, ML, and RAMO were measured and CM was assessed on transpharyngeal radiographs. LMO and AMO were strongly and significantly related (r = 0.71). LMO was significantly influenced by AMO and ML. No significant differences between AMO and RAMO were found. CM was strongly and significantly related to AMO (r = 0.72) and weakly but significantly related to LMO (r = 0.42). Based on the results of this study recommendations are made regarding the appropriate application of TMJ mobility assessment methods.