OBJECTIVETo measure passive tactile threshold of natural teeth in six orthogonal orientations, to analyze impact factors, and to guide the occlusal adjustment in a personalized manner.

METHODSThe passive tactile thresholds of 218 natural teeth from 20 healthy subjects were measured in six orthogonal orientations using a digital test system for tactile function of teeth. The subjects were composed of 10 males and 10 females, with a mean age of 25 years. The natural teeth were tested from central incisors to first molars in maxilla and mandible. The passive tactile thresholds of teeth were measured respectively in the four horizontal orientations of labial (buccal), lingual, mesial and distal, and the two axial orientations of apical and coronal. The multilevel modeling (MLM) was used to analyze impact factors.

RESULTSThe passive tactile thresholds of anterior teeth, premolars and molars were 16 (18), 38(57) and 105 (115) mN respectively. The difference between subjects was of statistical significance (P < 0.05). The three factors of tooth, gender and orthogonal orientation were disclosed to influence the passive tactile threshold of natural teeth (P < 0.01). The influence level of the factors was tooth > gender > orthogonal orientation.

CONCLUSIONSA force level of 10 mN could be detected by natural teeth. There was statistical difference in the passive tactile threshold between subjects. The passive tactile threshold was affected with tooth, gender and orthogonal orientation.