Effect of scanning pathways on trueness and precision in full-arch optical impression

Abstract Background: In this study, we investigate the effect of differences in scanning pathway during optical impression on the trueness and precision of full-arch impressions. Methods: Reference data were obtained using a lab scanner. All the optical impressions were measured across the dental arch using TRIOS® 3 in four different pathways. The reference data and optical impression data were superimposed using a best-fit method. The criteria for superimposition included the center of one starting side dental arch (partial-arch best-fit method : PB) and the center of full-arch (full-arch best fit method : FB). Data were compared between the left and right molars (starting and ending sides). The mean values (scan deviations) of trueness (n = 5) and precision (n = 10) were calculated after the difference in deviation between each group was absolutized. Visual observations using the superimposed color map images showed the variation in trueness. Results: There was no significant difference in scanning time or the amount of scan data between the four scanning pathways studied. Trueness did not differ significantly among the four pathways with respect to starting and ending sides, regardless of superimposition criteria. Precision with PB was significantly different between scanning pathways A and B, between pathways B and C for the starting sides and between scanning pathways A and B, between pathways A and D for the ending sides. In contrast, there was no significant difference between starting sides and ending sides pathways for FB. For PB, color map images showed a large error range in the direction toward the molar radius for occlusal surface and cervical regions on the ending sides. Conclusion: Differences in scanning pathways did not affect trueness, regardless of superimposition criteria. Scan pathway B on the starting side and scan pathway D on the ending side were the most accurate, and the difference in scanning pathways was observed to affect the precision of PB.