The aim of this study was to clarify the relationship between the buccal mucosa ridging (BMR), which has been mentioned to be a clinical sign of clenching, and the viscoelastic behaviour of oral mucosa. Twenty-three people with BMR and 21 people without BMR participated as volunteers in this study. Measurements of viscoelastic behaviour were performed using a suction viscoelastic meter on central part of lower labial mucosa. A suction pressure of 300 hPa was applied for 2 s and then released for 2 s, and the time-dependent changes in the deformation of the mucosa over this 4 s were recorded as a deformation curve. Distensibility, remaining deformation and elastic recovery, which describe viscoelastic behaviour, were calculated by the deformation curve. These parameters were compared between groups with and without BMR. No significant difference was found in distensibility between the two groups (P=0·349). There were significant differences for the remaining deformation (P=0·012) and the elastic recovery (P=0·032), and the group with BMR showed higher remaining deformation and lower elastic recovery than the group without BMR. Based on these results, it clarified that the BMR is related to the mucosal viscoelastic behaviour, in particular remaining deformation and elastic recovery.