Optoelectronic Three-dimensional Condylar Movement Analysis During Mouth Opening and Protrusion

Objectives: The aim of this study was to quantitatively assess the condylar path during maximum mouth opening and protrusive standardized movements in healthy subjects. Methods: Free, habitual movements of mouth opening and protrusion of 18 subjects (9 women, 9 men) aged 21-32 years were recorded using an infrared optoelectronic three-dimensional motion analyzer (BTS Smart System). All subjects had complete healthy permanent dentition, canine and molar Angle Class I jaw relationships, no previous history of craniofacial surgery, trauma, or congenital anomalies, and no previous orthodontic treatment. The movements of nine spherical passive markers (3 head plane, 3 mandibular plane, 1 interincisor point, right and left condyles) were recorded during the movements. Three-dimentional antero-posterior pathways of the interincisal and of the two condylar reference points were assessed in opening and protrusion. Data were analyzed by ANOVA. Results: Mandibular length and width were larger in men than in women. The maximum mouth opening was not significantly different (p>0.05) between the sexes. Condylar path at maximum opening was significantly larger than at max protrusion (p=0.01). Condylar paths did not differ between sexes (p>0.05). Conclusion: Condylar path length at max protrusion was smaller than at max mouth opening in Angle Class I healthy subjects, without sex-related differences. These findings will enter in a reference database for oncoming surveys on pathological TMJ or pre/post surgical patients.