Circular comparison of finish lines obtained from digital scans and conventional impressions: A clinical study

Clinical studies that have investigated whether intraoral scanners (IOSs) are equivalent or even superior to conventional impressions in capturing subgingival finish lines are sparse.

The purpose of this clinical study was to compare circumferentially the course of subgingival chamfer preparations captured by both digital scans (DIGI) and conventional impressions (CONI) using CONI as reference.

Sixteen patients with a total of 50 teeth requiring crown preparations were included. For each die, a conventional polyether double-mix impression was made for the CONI workflow, and an intraoral scan was obtained for the DIGI setup. The CONI definitive casts were digitized, and the finish lines of the dies were defined for both workflows. The corresponding CONI and DIGI dies were registered. The deviations of the finish lines were analyzed circumferentially using an inspection software program with CONI as the reference. Positive (apical) and negative (coronal) deviations were calculated. Descriptive statistics were computed, normality was assessed using the Shapiro-Wilk test, and differences among tooth regions were analyzed using a linear mixed-effects model (α=.05).

On average, 9% of the DIGI finish lines were apical relative to the CONI margins, with a mean ±standard deviation of 68 ±54 µm. In contrast, 91% of the DIGI finish lines were located coronally, with a mean ±standard deviation of 245 ±108 µm. There were no statistically differences among tooth regions (P>.05).

The results of this study suggest that digital scans may not capture subgingival preparation margins with the same accuracy as conventional methods.