The effect of age and prosthodontic status on the clinical and electromyographic assessment of the interocclusal rest space

Statement of problem

Clinicians are aware that the vertical dimension of occlusion and the interocclusal rest space (IRS) are 2 major factors that require consideration in the management of patients needing oral reconstructive procedures. However, how the dimensions vary with age and prosthetic status is unclear.

Purpose

The purpose of this clinical study was to analyze the IRS in dentate, partially edentulous, and completely edentulous participants using both conventional and electromyographic (EMG)-based methods. The effect of age and prosthodontic status on the clinical and EMG assessment of the IRS was also explored.

Material and methods

The IRS was determined for a group of dentate (n=31) and partially edentate (n=31) participants, as well as a group of completely edentulous (n=31) participants who had worn dentures for at least 10 years before participating in the study. Clinical and EMG-based assessments (monitoring both elevator and depressor activity) were carried out using 5 different methods: rest, relaxing mask, phonetics, deglutition, and myobalance. Bivariate and multivariate analyses (forward stepwise linear regression models) were performed to compare the effect of age and prosthodontic status on the IRS (α=.05).

Results

The average IRS values obtained from clinical and EMG-based assessments were significantly greater among dentate participants (2.8 ±0.4 mm and 3.6 ±0.6 mm, respectively) than partially edentulous (1.9 ±0.5 mm and 2.6 ±0.5 mm) and completely edentulous participants (1.4 ±0.5 mm and 2.2 ±0.6 mm). The IRS values obtained using the 5 methods of clinical assessment were statistically smaller than those obtained by EMG. Correlation and regression analyses showed that age and extended edentulism significantly decreased the IRS. For the IRS determined clinically, a decrease was found of 0.01 to 0.02 mm/year, based on the age of the participant. However, this decrease became greater (0.05 to 0.6 mm) where the participant had changed from being dentate to partially edentulous and partially edentulous to completely edentulous.

Conclusions

The IRS becomes significantly smaller in relation to age and denture extension. The rest position in the clinical examination was located cranial to the position used to make the EMG-based measurement. Small but significant differences were found between the IRS values obtained in the clinical and EMG-based methods of assessment in all the prosthetic groups.