Comparative evaluation of effect of rescanning and cut out & stitching with uninterrupted single scan on the accuracy of digital impressions - An in vitro study

Aim: The purpose of this study is to evaluate the accuracy of digital impressions (DIs) subjected to rescanning, cutout, and stitching procedures compared to an uninterrupted single scan. Special focus on comparing the effects of these interventions on edentulous regions versus prepared abutment surfaces. Settings and Design: This was an in vitro study. Materials and Methods: A mandibular typodont with a prepared second molar and an edentulous first molar region was scanned using an intraoral scanner (3 Shape TRIOS 3). Fifty DIs were divided into five groups: uninterrupted single scan, rescanning, cutout and stitching of the concern area, cut-out and stitching of the edentulous area, and cutout and stitching of the prepared abutment. Accuracy was assessed by superimposing STL files of Dis and a reference laboratory scan using three-dimensional metrology software to calculate trueness and precision for local measures and reproducibility, whereas root mean square (RMS) was evaluated for overall geometric deviation. Statistical Analysis: Data were analysed using IBM SPSS Statistics v20.0. Normality was assessed using the Shapiro–Wilk test. One-way ANOVA with Tukey post hoc tests was used for trueness and precision, while the Kruskal–Wallis test with Bonferroni correction was used for RMSE. Independent-samples t-tests compared the cutout and stitching techniques between the edentulous and prepared-tooth groups. Statistical significance was set at α = 0.05. Results: The uninterrupted single scans demonstrated significantly higher trueness and precision compared with rescanning and cutout with stitching ( P < .05). No significant differences were observed between rescanning and cutout groups. Within the cutout groups, prepared abutment rescans yielded significantly greater accuracy than edentulous area rescans ( P < .001); whereas RMS error (RMSE) was lowest for rescanning, followed by cutout, whereas uninterrupted scans showing higher variability. Conclusion: Uninterrupted single scans provided the most accurate DIs overall. Rescanning and cutout with stitching procedures reduced trueness and precision but produced clinically acceptable results. Uninterrupted scans having better trueness/precision, but rescanning showing better RMS accuracy was more adversely affected in edentulous regions than in prepared abutments, highlighting the importance of uninterrupted scanning protocols in partially edentulous cases.