Topographic study of human tongue in relation to oral tribology

Abstract

Human tongue plays a critical role in food oral processing and in particular to food manipulation and texture sensation. We speculate that different topographic characteristics among human individuals could be a fundamental cause for different food oral behavior and sensory perception. We hypothesize that tongue surface roughness will influence oral lubrication and therefore texture sensation. As the first initiative, this work investigated surface profile of human tongue. Altogether 71 young Chinese subjects participated in this investigation. Double moulding using silicone rubber and followed by gypsum was applied for the replication of the surface microstructure of human tongue. Optical scanning was applied to obtain 3D data of the replicated tongue surfaces. Mountains Map software was used to analyze topographic features. The method was verified by specimen of standard surfaces as well as pig's tongue. Results show that human tongue is generally symmetrical along the central line, but varies across the different area of the tongue. Tongue tip is the roughest part of the tongue. The roughness of the tongue decreases gradually from the front to the back. The calculated arithmetic roughness of the tongue tip varies from 50 μm to 160 μm for the investigated subjects, with an arithmetic average Sa at 89.53 ± 20.48 μm and a square root average Sq at 114.80 ± 25.47 μm. A preliminary analysis showed a possible correlation between tongue surface roughness and oral lubrication.