[Study on the consistency between the trajectory of small opening and closing movements and the empirical hinge axis movement of the mandibular incisal point of healthy individuals].

Objective

To investigate the consistency between the small open-close movement trajectories of the mandibular incisor point in healthy subjects and the theoretical hinge axis circular movement trajectory, and to analyze the influence of the starting mandibular position on these trajectories.

Methods

Twenty healthy volunteers, including 11 men and 9 women, were recruited from the postgraduate student population of the Department of Prosthodontics, Peking University School and Hospital of Stomatology. The age of the participants was (28.0±5.6) years. Mandibular small open-close movement trajectories initiated from the centric relation position (CRP) and the intercuspal position (ICP) were recorded using the mandibular movement recording system, designated as CRP group and ICP group, respectively. Multi-source data from the subjects were used to construct static virtual patients, and the theoretical hinge axis circular movement trajectory of the mandibular incisor point was virtually constructed as the reference group. Trajectory deviation and trajectory flatness between CRP or ICP group and reference groups were calculated in the mathematical computing software, followed by statistical analysis to verify the influence of the CRP or ICP starting position on the small open-close movement trajectory of the mandibular incisor point.

Results

Trajectory deviation for small open-close movements initiated from CRP and ICP in the 20 subjects was (1.07±0.17) and (1.08±0.17) mm (t=0.30, P=0.767), respectively. Trajectory flatness for the CRP and ICP-initiated small open-close movement trajectories was (0.54±0.15) and (0.59±0.12) mm (t=1.20,P=0.245), respectively.

Conclusions

The small open-close movement trajectories of the mandibular incisor point initiated from both CRP and ICP exhibit good circular movement characteristics, with the starting position showing no significant influence on the trajectory.