Do occlusal contact areas of maximum closing position during gum chewing and intercuspal position coincide?

Occlusal contact area (OCA) is most important during the occlusal phase when food particles are being pulverized. OCA is most easily measured statically at the maximum intercuspal position (ICP). However, the assumption of coincidence between dynamic maximum closing position (MCP) and statically determined ICP has not been previously tested. The purpose of this study is to introduce a method of quantifying OCA of all teeth during dynamic mastication to determine whether the OCA at the dynamic MCP during chewing is similar to the statically determined maximum possible OCA.

Thirteen healthy females participated in this study. Morphologic tooth shape data were measured from dental models using an automatic 3D digitizer. Mandibular movement during gum chewing was recorded using an optoelectronic analysis system with 6 degrees of freedom, and ten cycles were selected for analysis. The dynamic OCA was estimated with a measurement system combining 3D tracking of mandibular movements with 3D digitization of tooth shape.

The estimated mean 3D difference between the incisor position at ICP and MCP was 0.129 mm. At the dynamic MCP, the maximum OCA was 98.5% (68.42 mm(2)) of the maximum possible contact area in the static ICP (69.46 mm(2)). Both between-subject and within-subject variation were least at the dynamic MCP.

The maximum OCA during chewing is nearly identical to statically determined maximum possible OCA.