Influence of the cut-out-rescan procedure and rubber dam color on the trueness of intraoral scanners: A laboratory evaluation.

Purpose: To evaluate the laboratory effect of the cut-out-rescan procedure and the rubber dam color on the trueness of two intraoral scanners (IOS).

Methods: An onlay preparation was performed on a typodont maxillary left 1st molar. The left hemi-arch of the maxilla was scanned using two IOS (Trios 3, 3Shape; n=20). These digital scans were defined as references and exported. The prepared tooth and 1 mm proximal surfaces were cut-out using the IOS' software tools. Following the rubber dam (blue-color) isolation, the cut-out area was rescanned and recorded. Reference and rescan data in .STL were uploaded to the software programs and superimposed. The deviations were obtained selectively for the teeth. Also, additional hemi-arc rescans with different rubber dam sheet colors (blue, purple, and black) were obtained and superimposed with reference scan without cut-out procedure. Trueness was evaluated using root mean square (RMS) error by Geomagic Control X and mean distance (Md) by Oracheck. Data were analyzed using ANOVA, Shapiro-Wilk, and Independent Samples (P< 0.05).

Results: The Md values by the Trios 3 were significantly higher than Omnicam for the 1st premolar and 1st molar (P< 0.05). Omnicam's RMS and Md values for the 2nd molar were significantly higher than 1st premolar and 1st molar (P< 0.001). Trios's RMS values were significantly higher for the 2nd molar than the 1st molar (P< 0.001). A lower deviation in Md values was obtained for black rubber dam color compared to the blue and purple in Omnicam and the purple in Trios (P< 0.005).

Clinical significance: The cut-out-rescan procedure may influence the scanning trueness depending on the IOS and location of the cut-out area. The use of the cut-out-rescan procedure will be optimized by considering the technology and software of the IOS. The black rubber dam was considered the optimal choice when using the rescan procedure.