Comparison of intraoral scanner accuracy before and after calibration: an in vitro study.

Background: Intraoral scanners are an essential part of modern digital dentistry, yet the influence of calibration on their accuracy remains underexplored. This in vitro study aimed to evaluate the effect of calibration on the scanning accuracy of the TRIOS 3 intraoral scanner after a noncalibrated period of 324 days.

Methods: Digital impressions of upper and lower full-arch phantom jaw models were obtained before and after calibration using the TRIOS 3 intraoral scanner (3Shape, Copenhagen, Denmark; software version 22.1.1). A total of 20 scans (five before and five after calibration for each jaw) were acquired by a single experienced operator. Reference scans were obtained with an extraoral scanner (E4, 3Shape, Denmark). Linear measurements (intermolar and interpremolar) and three-dimensional superimposition parameters (Absolute Average, Root Mean Square, and (90-10)/2) were used to assess trueness and precision. All measurements were performed using Medit Link software (version 3.3.6; Medit).

Results: Assessment of method error demonstrated excellent intrarater reliability for all trueness and precision parameters (ICC > 0.994, P < 0.001). Statistical analyses revealed minor differences in linear measurements and three-dimensional superimposition values before and after calibration, none of which reached statistical significance (P > 0.05). Regarding trueness, the upper jaw showed slightly increased Absolute Average (0.068 ± 0.004) and (90-10)/2 values (0.093 ± 0.006) after calibration compared to before calibration (0.065 ± 0.003 and 0.087 ± 0.006, respectively), while the lower jaw exhibited higher Root Mean Square values after calibration (0.088 ± 0.008) than before (0.076 ± 0.006). Precision results showed a slightly increased Absolute Average (0.029 ± 0.003), Root Mean Square (0.064 ± 0.006) and (90 - 10)/2 (0.036 ± 0.006) values in the upper jaw, and Root Mean Square (0.095 ± 0.010) values in the lower jaw after calibration. Trueness and precision of linear measurements also showed a general decrease after calibration in both jaws, though the differences were not statistically significant (P > 0.05).

Conclusions: The findings of this study show that the TRIOS 3 intraoral scanner maintained its accuracy without calibration for up to 324 days, suggesting that occasional deviations from manufacturer-recommended calibration intervals may not compromise scan quality. However, adherence to routine calibration is recommended until further evidence is available.