The impact of implant placement depth, posterior tooth presence and scanning strategies on accuracy and precision of partial edentulism

Aim: To evaluate the accuracy and precision of scan data obtained from partially edentulous maxillary models with different implant placement depths using different scanning strategies. Materials and Methods: Implants were placed at two different depths (1 mm, 3 mm) in two polyurethane maxillary models (M1, M2) simulating Kennedy Class II, modification I partial edentulism. A total of eighty datasets were obtained by applying four different scanning strategies (S1, S2 (occlusal-buccal-palatal); S3, S4 (zigzag)) using an intraoral scanner, and these datasets were aligned with reference scan data obtained using a laboratory scanner. Analyses of root mean square (RMS), linear, z-axis linear, angular, and inter-implant distance deviations were performed, and statistical evaluations were conducted using 2×4 factorial ANOVA, Bonferroni post-hoc tests, and correlation analyses. Results: Scanning strategies showed significant differences in all-model RMS and 16 RMS in Model 1, and in all-model RMS, 16 RMS, and 26 RMS in Model 2 (p<0.05). Linear deviations of implants 16 and 24 differed significantly between the models (p<0.05). A positive correlation was observed between RMS and linear deviation (p<0.05). While scanning strategies had no significant effect on angular deviations, a significant difference was observed between S1 and S4 in inter-implant distance deviations for implants 14-24 and 16-26 (p<0.05). Conclusion: Implant placement depth and scanning strategies are factors that affect the accuracy of digital impression. Greater RMS values were observed in association with deeper implant placements. The presence of posterior teeth improved scanning accuracy. Occlusal-buccal-palatal scanning strategies provided higher accuracy compared to zigzag scanning strategies. Selecting the appropriate strategy is important for optimizing impression accuracy in clinical applications. Keywords: Digital impression accuracy, Implant placement depth, Partial edentulism, Scanning strategy.