Evaluation and comparison of the scanning accuracy of three intraoral scanners for single crown, three-unit, and cross-arch fixed partial denture by three-dimensional digital superimposition technique and measurement of vertical marginal fit of three-dimensional-printed resin retainers: An in vitro study.

Abstract

Aim: This study aims to evaluate and compare the scanning accuracy of three IOSs and measuring the vertical marginal fit of three-dimensional (3D) printed resin retainers for single crown, three-unit, and cross-arch fixed partial denture situations.

Settings and design: Comparative In Vitro Study.

Materials and methods: A maxillary Nissin typodont with prepared abutments at #13, #23, #25, #27, and #16 served as the master model. A calibrated Shining 3D laboratory scanner provided the reference standard tessellation language (control). Each IOS generated six scans ( n = 6/scanner; 18 test scans). Trueness and precision were derived by best-fit superimposition in Geomagic Design X. Fifty-four single-unit, three-unit, and cross-arch retainers were 3D-printed. Vertical marginal discrepancy was measured at mid-buccal and mid-lingual sites using a digital stereomicroscope (×20).

Statistical analysis used: One-way ANOVA with Tukey's post-hoc test was used for comparisons among scanners and prosthesis spans. Pearson's correlation was used to assess the relationship between trueness and marginal fit, and Chi-square test was used to assess clinical acceptability. A P value ≤0.05 was considered statistically significant.

Results: 3Shape TRIOS 3 showed the highest trueness (28.5 ± 5.2 µm) and precision (18.2 ± 3.1 µm), followed by Medit i700 and Shining 3D Aoralscan 3 ( P < 0.001). Marginal discrepancy was lowest with 3Shape TRIOS 3 (52.4 ± 6.5 µm) and increased with span. A positive correlation was found between trueness and marginal fit ( r = 0.82; P < 0.001). Clinical acceptability was 100%, 94.4%, and 77.8% for 3Shape TRIOS 3, Medit i700, and Shining 3D Aoralscan 3, respectively ( P = 0.041).

Conclusion: All three scanners delivered clinically acceptable results; 3Shape TRIOS 3 yielded the highest accuracy and best marginal adaptation. Accuracy and marginal fit deteriorated as prosthesis span increased.