Accuracy of bracket positions with a CAD/CAM indirect bonding system in posterior teeth with different cusp heights.

INTRODUCTION: Our objective was to evaluate the effect of cusp height of posterior teeth (first premolar, second premolar, first molar) on the accuracy of the computer-aided design and computer-aided manufacturing (CAD-CAM) indirect bonding system.

MATERIAL: Five kinds of maxillary arch models, without attrition, were divided into 2 groups: control group (with 0.5 mm of grinding) and experimental group (with the addition of 0.5 mm of wax to the cusp tip). Rapid prototype models were printed for both groups. Transfer jigs of the individual tooth brackets were designed using a digital model. 3-dimensional program to evaluate the differences between the intended digital bracket position and actual bracket position after indirect bonding. The differences were measured in the linear (mesiodistal, buccolingual, vertical) and angular (angulation, rotation, torque) dimensions. The Wilcoxon signed rank test was used for statistical analyses; significance was defined as P <0.05.

RESULTS: Both groups had similar frequencies of errors between the intended and actual bracket positions. The frequencies of vertical errors over 0.5 mm were 3.3% and 6.7% in the control and experimental groups, respectively. The frequencies of angulation, rotation, and torque errors over 1° were 53.3%, 43.3%, and 60%, respectively, for the control group; and 60%, 60%, and 73.3%, respectively, for the experimental group.

CONCLUSIONS: A difference in cusp height of maxillary posterior teeth did not produce a statistically significant difference in the linear and angular dimensions of bracket placement with the CAD/CAM indirect bonding system. However, given the tendency for a higher frequency in bracket placement errors in posterior teeth with larger cusp tips, cusp height should be considered when using a CAD/CAM indirect bonding system.