Influence of tongue pressure and width on tongue indentation formation.

The purpose of this study was to clarify which physiological and anatomical factors were involved in the formation of tongue indentations, which are believed to be a clinical sign of clenching. Twenty-four dentulous subjects were investigated. They were divided into two groups, depending on the presence or absence of tongue indentations: (i) a tongue indentation group and (ii) a no tongue indentation group. Intraoral appliances containing a small pressure sensor were placed at the lingual surfaces of the upper and lower right first molars. Lingual pressure on the lingual surfaces of the upper and lower right first molars was then recorded under different conditions. The tasks selected as physiological factors to be recorded were: (i) silent reading at rest for 10 min, (ii) maximum voluntary clenching (MVC) for 5 s, (iii) 10% of MVC for 1 min and (iv) swallowing. The results for all tasks were compared between groups. Tongue width and dental arch width were also measured as anatomical factors. No significant differences were found between groups during silent reading at rest, clenching, swallowing, or in tongue pressure integration during silent reading at rest. However, a significant difference was found in terms of tongue width (P < 0.05). These results indicate that neither volume of lingual pressure exerted on the lingual surface of the teeth during rest, clenching, nor swallowing are related to the formation of tongue indentations. The results do suggest; however, that tongue width at rest plays an important role in the formation of tongue indentations.