Visualization of Tooth Movements in Six-Degree-of-Freedom during Occlusal Force Loading

Objectives:

During clenching and chewing, teeth exhibit a degree of mobility due to occlusal contact, tongue movement, circulation and other surrounding phenomena. These tooth movements should be taken into consideration when making occlusal adjustments of dental restorations and fixed partial dentures. The purpose of this research was to develop method for evaluation of the slight tooth movements.

Methods:

Tooth movements of a 31-years old male volunteer's right side upper first premolar related to left side upper first premolar during different occlusal force loading condition i.e. at the buccal cusp, palatal cusp, central fossa, and a proximal tooth were measured by means of the high-resolution motion detector, whose resolution is 1.3µm for translation and 0.00017degrees for rotation. A three-dimensional (3-D) digitizer and computerized tomography were used to make a 3-D reconstruction of the whole his first premolar shape. Data from these devices were integrated for 3-D tooth movement visualization and animation. The helical (screw) axis concept and the coloring of the tooth surface with pseudo-colors according to the magnitude of tooth displacement from resting tooth position were adopted in order to evaluate tooth movements in six degrees of freedom visually.

Results:

The maxmum displacement at the central fossa of the occlusal surface was 148µm, 77µm, 95µm and 119µm during occlusal force loading at the buccal cusp, palatal cusp, central fossa, and proximal tooth (canine) respectively. By using the helical axis concept and the coloring of the tooth surface with pseudo-colors, slight tooth movements can be enhanced graphically and the characteristic tooth movement patterns under different occlusal force loading conditions can be realized.

Conclusion:

Our visualization and animation method provides an easier understanding of tooth movements in six degrees of freedom. It was suggested that the study of individual tooth movement is required to advance functionally adequate occlusal morphology.