[Clinical study on the accuracy of occlusal contacts on digital model]

Objective: To explore the accuracy of occlusal contacts on digital model made by intraoral scanner. Methods: Twenty healthy subjects [6 males, 14 females, (24.4±1.4) years old] with intact dentition were randomly recruited from postgraduate students in Capital Medical University School of Stomatology who volunteered to participate in this study. For each participant, the 2nd and 3rd quadrant of natural dentition was scanned. A diagnostic test design was performed. The occlusal contacts of the maximal intercuspal position (MIP) were extracted with the transillumination of silicone interocclusal records, and the extraction threshold was set as ≤50 μm. Intraoral scanning system was used to scan in MIP and generate occlusal contacts on digital model. Five groups were designed as test groups according to included tooth position: group 1 (buccal scanning ranged from tooth 21 to 23), group 2 (buccal scanning ranged from tooth 23 to 26), group 3 (buccal scanning ranged from tooth 24 to 26), group 4 (buccal scanning ranged from tooth 25 to 26), group 5 (buccal scanning ranged from tooth 21 to 26). Five groups occlusal contacts on digital model were generated respectively. According to the relevant literature, the upper occlusal surface was divided into 28 partitions, and the accuracy of occlusal contacts on digital model was calculated with the transillumination of silicone interocclusal records as the reference standard. Subgroup analysis was performed according to anterior teeth area, premolars area and molars area. Results: The accuracy of occlusal contacts on digital models of the half dentition in five buccal scanning positions were: group 1 (86.8%), group 2 (92.0%), group 3 (90.7%), group 4 (91.1%), group 5 (90.4%), and the accuracy of occlusal contacts in group 1 was significantly lower than those in the other four groups (P<0.05). The accuracy of anterior teeth area were 85.6%-93.9%; the accuracy of premolar area were 92.5%-94.4%; the accuracy of molar area were 77.3%-93.6%, group 1 was significantly lower than those in the group 4 in molars area (P<0.05), the accuracy of anterior area was statistically less than premolars area and molars area in group 1 (P<0.05). There was no statistical difference in pairwise comparison between the three sections (P>0.05). Conclusions: The digital models scanned intraoral methods provide accurate, quantitative measures of occlusal contacts when transillumination contacts are the reference standard.