Effects of finish line and cavity depth on intraoral scanner accuracy in different endocrown designs

It has been reported that variations in pulpal cavity depth can influence the scanning accuracy of digital impressions obtained using intraoral scanners. However, current studies investigating the impact of different cavity geometries in endocrown preparations on digital impression accuracy with contemporary intraoral scanners remain limited. The aim of this in vitro study was to evaluate the effects of different endocrown designs and finish line configurations on the scanning accuracy of intraoral scanners. For this purpose, six prepared tooth models were fabricated with two different cavity depths (2 mm and 4 mm) and three different occlusal geometries (a shoulder finish line located 2 mm occlusal to the cervical line, a shoulder finish line located 4 mm occlusal to the cervical line, and a butt margin). In each group, digital data obtained with a laboratory scanner (Medit T310) were used as reference models. The models were scanned with four different intraoral scanners (Trios 3, Medit i600, Helios 600, and Trios 5) (n=10). The digital impressions obtained from the intraoral scanners were superimposed onto the reference data using a best-fit algorithm to assess scanning accuracy. For statistical analysis, SPSS software (Version 22, SPSS Inc, Chicago, IL, USA) was used. Levene's test was performed to assess the assumption of homogeneity of variances among the compared groups. Repeated measures analysis of variance (ANOVA) was used for normally distributed data, while the Friedman test was used for non-normally distributed related numerical data. Following the identification of statistically significant differences in ANOVA and Friedman tests, pairwise comparisons between scanners were conducted using Bonferroni-corrected post- hoc tests. The level of statistical significance was set at p<0.05 for all analyses. Models with shoulder finish lines demonstrated significantly higher deviation values across all intraoral scanners (p<0.05). No statistically significant difference was found between models with 2 mm and 4 mm pulpal cavity depths (p=0.741). For all samples, digital impressions within clinically acceptable accuracy limits were obtained. This study was approved by Baskent University Institutional Review Board (Project no: D-DA24/03) and supported by Baskent University Research Fund. Keywords: Endocrown, intraoral scanner, finish line, cavity depth, accuracy.