[The influence of different preset drill radius and tooth position on the compensation gap of zirconium dioxide restoration].

Purpose: To explore the influence of different preset drill radius on the drill compensation space of zirconia dioxide restoration and the characteristics of tooth position and anatomical parts of the drill compensation space.

Methods: The digital design data of 12 cases of incisor, premolar and molar were randomly selected, and the radius of the needle was preset to 0.3, 0.4, 0.5 and 0.6 mm. Software analysis was performed to obtain four evaluation index values for each group of drill compensation gaps ,including compensation area, the proportion of the drillcompensation area to the preparation area, compensation volume and the maximum value of the compensation. The compensation frequency of the occlusal/incisal edge, axial surface and edge area of 0.5 mm preset radius group were recorded. Data were analyzed by two-way ANOVA and Chi-square test using SPSS 22.0 software package.

Results: The preset drill radius and tooth position significantly affect the values of the four evaluation indicators(P＜0.05) of the drill compensation space, among which the four evaluation index values were significantly reduced by the preset radius of the drill (P＜0.05). The probability that the maximum drill compensation thickness value of incisor and molar teeth in the 0.5 mm group and all types of teeth in the 0.6 mm group exceeded 300 μm existed, the frequency of 20 μm gap compensation in the incisor/occlusal edge area, the axial surface area, and the edge area of the preparation decreased in turn(P＜0.05).

Conclusions: The preset radius of 0.3-0.4 mm can obtain a reasonable drill compensation gap on the tissue surface of the prosthesis. The occlusal/incisor area of the preparation needs to be carefully prepared to reduce the frequency of gap compensation.