Objective evaluation of tooth carving using homologous models

Tooth carvings are evaluated subjectively. However, subjective evaluations are associated with low intra- and inter-evaluator reliability in providing feedback for the fabrication of better tooth carvings. Therefore, this study aimed to analyze the relationship between subjective evaluation and the morphological characteristics of tooth carvings and their morphological characteristics using the feedback method in the low-scoring group.

Between April 2013 and September 2021, 120 maxillary left first molar carvings fabricated by undergraduate students were subjectively evaluated by an experienced instructor using a five-point scale. The tooth carvings were scanned to obtain three-dimensional shape data and divided into two groups, the high- and low-scoring groups, for principal component analysis. Homologous models with dimensions matching those of the average model were created, and principal component analysis was performed to evaluate the morphological characteristics of the tooth.

Principal component analysis indicated that an objective evaluation was possible using homologous model. On increasing the subjective evaluation, the occlusal inclination angle and the cervical region of the tooth became steeper, and the shape of the occlusal surface resembled a parallelogram. In addition, large morphological differences were observed in the position of the cervical region of the tooth, height of contour, and shape of the occlusal surface in the low-scoring group, whereas no such difference was observed in the high-scoring group.

Objective evaluation of tooth carving was possible using homologous model. The evaluation of tooth morphological characteristics could be effective in providing feedback to undergraduate students.