Pressure-pain threshold of oral mucosa and its region-specific modulation by pre-loading.

Once subjected to denture wearing, oral mucosa has to withstand mechanical loads of various levels and durations. However, how this load affects oral mucosal sensitivity is unknown. This study investigated the pressure-pain threshold (PPT) of oral mucosa with or without pre-loading. An electric pressure algometer was developed specifically for measuring the PPT of oral mucosa. Measurements of 10 dentulous maxillae showed that the baseline PPT (BPPT) of the palatal site was 4.9- and 3.7-fold greater than that of the labial or buccal sites, respectively. The PPT of the labial site decreased significantly compared with its BPPT after 2 s-100% BPPT and 5 s-100% BPPT pre-loading. The PPT of the palatal site increased after 5 s-50% BPPT and 5 s-80% BPPT and 0.2 s-100% BPPT and 2 s-100% BPPT pre-loading. The PPT of the buccal site did not change after all levels and durations of pre-loadings tested. These results indicated the disproportionate modulation of oral mucosal PPT following various loads, suggesting that oral mucosa possesses region-specific psychophysical tolerance to mechanical stimuli.