Visual Vs. Spectrophotometric Analysis for Bevels in Class IV Restorations

Objectives: The purpose of this study was to determine which type of bevel in a class IV dental composite restoration is the most esthetic and most closely mimics the optical properties of natural tooth structure via clinical and spectrophotometric evaluations. The null hypothesis is that there is no difference between bevels, in regards to what is more esthetic.
Methods: The class IV samples were made via CAD/CAM milling for standardization. There was a negative control (no bevel), a positive control (original tooth), and six different types of bevels. The fractures were restored with the same type of composite via a template fabricated with a 3D printer. Once completed, the samples were randomized and evaluated visually by 91 people in five groups (faculty, graduate residents, undergraduate dental students, assistants/hygienists and auxillary staff). Evaluators placed the samples in the order they deemed least to most esthetic. After the visual evaluation, the lightness values were measured optically with a spectrophotometer at various points on each sample. One-way ANOVA with the post-hoc Tukey’s HSD was conducted to detect the difference in mean rating score among five groups of evaluators and Kendall’s W was used to evaluate an agreement among multiple raters.
Results: The groups were ranked from least to most esthetic as follows: no bevel, short and straight bevel, short and scalloped bevel, long and straight bevel, long and scalloped bevel, infinite and straight bevel and infinite and scalloped bevel by the 91 evaluators, and Kendall’s W was 0.80 (strong agreement). Moreover, no significant difference in rating scores was found among the five groups of evaluators regarding each type of bevels (p>0.05).
Conclusions: The null hypothesis was rejected. The findings of this study indicated that the infinite and scalloped bevel was the most preferred and no bevel was the least preferred via a strong agreement from the evaluators.