Influence of interdental space and operator experience on the accuracy, scanning time, and number of photograms of veneer preparations digitized by using an intraoral scanner

Abstract

Statement of problem

Studies analyzing the accuracy of intraoral scanners (IOSs) for fabricating veneer restorations are scarce. Also, the space between tooth preparations significantly impacts the accuracy of IOSs. The influence of interdental space on the accuracy of veneer preparations digitized by using IOSs remains uncertain.

Purpose

The purpose of the present in vitro study was to assess the influence of interdental spaces and operator experience on the accuracy, scanning time, and number of photograms of an IOS for acquiring the virtual definitive casts for fabricating 2 adjacent veneer restorations.

Material and methods

A maxillary model with the 6 anterior teeth with a veneer preparation on both central incisors was virtually design. Three casts were printed each with a different interdental space between the preparations: 0.5, 1.0, and 1.5 mm. Each cast was scanned with an IOS (TRIOS 3) by an experienced and an inexperienced operator (n=10). The scanning time and number of photograms were registered. Linear measurements were obtained between the mesial surfaces of both veneer preparations in the virtual reference casts and experimental scans aiming to assess the interspace reproduction capabilities of each subgroup tested. Specimens with a bridge scanning error were registered. Two-way ANOVA and pairwise multiple comparisons were used to analyze trueness, scanning time, and number of photograms (α=.05). Levene and pairwise comparisons using Wilcoxon Rank sum tests were used to analyze precision (α=.05).

Results

All the specimens of the InExp-0.5 subgroup and 30% of scans in the InExp-0.5 subgroup had a bridge scanning error. Significant trueness, precision, scanning time, and number of photograms discrepancies were found among the groups (P<.001) and subgroups (P<.001), with a significant interaction between group×subgroup (P<.001). In the 0.5 group, there were trueness (P<.001) and precision discrepancies between the experienced and inexperienced operator. The experienced operator demonstrated better trueness and precision scanning the 0.5-mm cast when compared with the other reference casts (P<.001). The inexperienced operator revealed lower trueness when scanning the 0.5-mm cast when compared with the 1.0- (P<.001) and 1.5-mm (P<.001) casts. Scanning time discrepancies were revealed between the operators in the 1.0 (P<.001) and 1.5 groups (P<.001). For the inexperienced operator, the 1.0 and 1.5 groups (P<.001) were significantly different. Number of photogram discrepancies were revealed between the operators in the 1.0 group (P<.001) and 1.5 group (P<.001). Additionally, for the inexperienced operator, the 1.0 and 1.5 groups were significantly different (P<.001).

Conclusions

The interdental spaces and operator experience impacted the scanning accuracy, scanning time, and number of photograms of the IOS tested. The inexperienced operator was unable to scan the 0.5-mm interdental space and demonstrated similar scanning trueness and precision when scanning the 1.0- and 1.5-mm reference casts, but higher scanning time and number of photograms when compared with the experienced operator.