Subjects and dentition

Males outnumbered females in the present study, but there have been no reports of differences in mean occlusal load between males and females in the 50–54 age group. While there have been reports that in healthy, dentulous subjects, the total occlusal force in the molar region on one side is approximately 400 N at maximum clenching strength, in the present study, the mean occlusal force on the natural tooth side at 100 % MVC was 274.4 ± 111.5 N. However, considering the subjects in the present study were of middle and old age, with mean age 49 years, the results probably have a certain validity.

Occlusal force is often measured across the whole jaw. The Dental Prescale used for occlusal force measurement has a thickness of approximately 100 μm, and concern has been raised that this thickness might affect the results of occlusal force distribution measurement. However, as good reproducibility of results from the molar region has been reported, in the present study, the molar region from the first premolar to the second molar on both sides was examined.

Study methods

Examination of occlusal contact

Materials such as wax, occlusal registration paper, and pressure-sensitive paper are used to examine occlusal contact. The present study utilized an examination method using silicone. The Blue Silicone used in the present study is a cartridge type, which allows a nearly constant mixing ratio to be maintained, it has low viscosity and thus flows well, and it shows little dimensional change over time. It therefore fully met the requirements for a material for registration of occlusal contact status.

A prior study reported low reproducibility when using Dental Prescale at low clenching strength. In addition, the use of Blue Silicone to take impressions at high clenching intensities of 80 and 100 % MVC places a burden on subjects, as Blue Silicone takes a long time to harden. For these reasons, when measurements from low to high clenching strength were made in the present study, Blue Silicone was used at clenching intensities of 20, 40, and 60 % MVC, and Dental Prescale was used at 40, 60, 80, and 100 % MVC.