Micro-CT Evaluation of Enamel and Dentin Removal for Indirect Restorations

Objectives: This in vitro research aimed to evaluate the volumetric enamel and dentin tissue removal and the residual adhesion surface area after different dental preparations for indirect partial restorations (IPR).
Methods: A human molar was scanned using a Micro-CT and the STL file obtained was used to 3D-print 50 resin-tooth replicas. Standardized preparations for IPR were performed. The specimens were randomly assigned to 5 groups (n=10), according to the type of tooth preparations and the location of the maximum contour line with respect to the dental equator (DE): 1) Rounded shoulder above the DE (S/A); 2) Hollow chamfer above the DE (C/A); 3) Butt joint above the DE (B/A); 4) Rounded shoulder below the DE (S/B); 5) Chamfer below the DE (C/B).
The tooth replicas were then scanned and the STL files obtained were aligned and superimposed to the original STL model file. The volume of enamel and dentin removed during the preparations (One-way ANOVA) and the residual adhesion surfaces for enamel and dentin were calculated (Kruskal-Wallis test). The level of significance was set at p<0.05 for all the statistical analyses.
Results: No significant differences in terms of tissue reduction were found between S/A, C/A, and B/A (p>0.05). However, C/B was significantly more conservative in enamel reduction than the S/B (p<0.05). As for the residual adhesive surface area, C/B showed the highest enamel adhesive surface exposure among the different tooth preparations (p<0.05).
Conclusions: The chamfer preparation below the dental equator conserved significant amounts of tooth structure. No differences in terms of tooth structure removal were found among the preparations above the dental equator.