Use of Virtual Comparison Software for Preparation Depth Assessment in a Dental Technique Skills Course

The aims of this study were 1) to determine whether the Compare software Comparison% score provided appropriate feedback for preparation depth on a non-anatomical tooth and 2) to define an acceptable tolerance for use in calculating the Comparison% for virtual assessment of cavity depth on a non-anatomical mandibular first molar. Forty-six non-anatomical ivorine teeth with laser-marked outlines on their occlusal surfaces were used for this study. One tooth was prepared at a 1.5 mm depth, approved by participating faculty at a U.S. dental school, and served as the standard preparation. The remaining teeth were divided into three groups (n=15 per group) for cavity preparation depths of 1 mm, 1.5 mm, and 2 mm in the laser-engraved external outline. Teeth were prepared using an electric handpiece with a 330 bur and a hatchet. Virtual images of the standard and experimental tooth preparations were recorded using an intraoral scanner. Virtual comparison software was then used to superimpose a three-dimensional (3D) image of each experimental preparation on the 3D image of the standard preparation. The software calculated comparison surface percentage values (Comparison%) at a 100 and 200 micron tolerance for each specimen. Two-way mixed linear models (α=0.01) were adopted to compare outcomes for the two levels of tolerance for teeth with different depths of preparation. Using a tolerance level of 200 μm, Comparison% scores for the acceptable preparation depth of 1.5 mm were found to be significantly different (p<0.01) from those of the unacceptable 1 mm and 2 mm depth preparations. These findings suggest that virtual comparison software may be used to assess an acceptable depth for cavity preparation within a defined external outline.