This study evaluated the feasibility of a tooth preparation guide for prefabricated zirconia crowns (PZCs). Three-dimensional surface data for PZCs of the left maxillary primary first molar and left mandibular primary second molar were obtained using a model scanner. The tooth preparation data were digitally designed to harmonize with the adjacent teeth on the mixed dentition model and visualized using a color-coded map, which presents the required amount of tooth reduction. Twenty participants were recruited for preparing teeth with and without using the tooth preparation guide. The following three parameters were evaluated: tooth preparation time, harmony score, and amount of tooth reduction. The preparation time when using the guide was significantly reduced (p < 0.05), and a significant difference was observed in the harmony scores for the maxillary primary first molar preparation. Furthermore, the amount of tooth reduction was significantly different for both maxillary and mandibular primary molars (p < 0.05) in terms of the occlusal distal surface and buccal line angle in the maxillary primary first molars, and the smooth surfaces, proximal surfaces, and mesial line angles in the mandibular primary second molars. Thus, the results suggest that a tooth preparation guide could facilitate better tooth preparation for PZCs.

The present case report describes a rare case of dens evaginatus on the labial surface of mandibular incisor and interdisciplinary management including endodontic and periodontal treatment. A 10-year-old girl presented unusual whitish tubercle-like structure penetrated through the buccal gingiva of mandibular later incisor. In cone-beam computed tomographic view, pulpal tissue was extended from the principal root to the tubercle. Following full thickness flap reflection, the tubercle was carefully removed, resulting in dentin and pin-point pulp exposure. In order to prevent pulp necrosis and facilitate periodontal attachment to this area, Biodentine and enamel matrix derivative were applied. Gingival defect was compensated using a collagen matrix. Up to 2 years, harmonious gingiva state and no loss of tooth vitality were observed. In summary, dens evaginatus on mandibular later incisor could be successfully treated by means of interdisciplinary approach.