# Marginal adaptation analysis of CAD/CAM resin crown with non-invasive methods

## TL;DR

This study compares two methods for assessing the fit of dental crowns and finds that SS-OCT works well at a 90° angle.

## Contribution

The study introduces SS-OCT as a non-invasive clinical alternative for evaluating crown fit at a 90° light incidence angle.

## Key findings

- SS-OCT at 90° showed no significant differences compared to the silicone replica method.
- Marginal discrepancies increased as the light incidence angle decreased from 90° to 60°.
- SS-OCT is a viable non-invasive method for clinical evaluation of crown fit.

## Abstract

This study compared the silicone replica method with swept-source optical coherence tomography (SS-OCT) to analyze marginal adaptation and investigated the effect of the light incidence angle of SS-OCT on measurement precision.

A typodont-prepared mandibular right first molar was scanned using an intraoral scanner (Trios 3). Fourteen crowns were fabricated from CAD/CAM resin blocks (Katana Avencia P) using a 5-axis milling machine (DWX-50). Marginal adaptation at the buccal, lingual, mesial, and distal points was assessed using the silicone replica method and SS-OCT at light incidence angles of 60°, 75°, and 90°. Statistical comparisons were performed using two-way analysis of variance (ANOVA) and t-tests with Bonferroni correction, and t-tests at a significance level of 0.05.

At 60°, SS-OCT showed significantly larger marginal discrepancies than the silicone replica method at the buccal, lingual, and mesial points (p < 0.05). At 75°, only the lingual point showed a significantly larger value than the silicone replica method (p < 0.05). At 90°, no significant differences were observed between the SS-OCT and silicone replica methods (p > 0.05). Marginal discrepancy values increased as the angle changed from 90° to 75° to 60°, with significant differences between 60° and 75° and between 60° and 90° at the buccal and lingual points (p < 0.05).

SS-OCT is a viable alternative to the silicone replica method for assessing marginal adaptation at an incidence angle of 90 °.

SS-OCT, a non-invasive method, has the potential to be applied clinically for evaluating marginal fit in indirect restorations in vivo.