To evaluate the influence of the dental arch and cutting-off and rescanning procedures on the accuracy of complete-arch implant scans in partially edentulous arches.
A maxillary and a mandibular partially edentulous typodont with implant abutment analogs placed in the right and left first molar and right central incisor sites were digitized to create reference models by using an industrial optical scanner (7 Series Desktop Scanner; Dentalwings). Two experimental groups were scanned using an intraoral scanner (IOS) (TRIOS 4; 3Shape A/S): the Maxillary group (Mx) and the Mandibular group (Mb). Four subgroups were generated depending on the number of rescanned mesh holes: No holes (Mx-G0, Mb-G0), 1 hole (Mx-G1, Mb-G1), 2 holes (Mx-G2, Mb-G2) and 3 holes (Mx-G3, Mb-G3). A 3-dimensional metrology software (Geomagic Control X; 3D Systems) was used to measure the difference between the reference and the experimental scans computing the root mean square (RMS) error calculation. Two-way ANOVA and a post-hoc Tukey test were used to analyze the trueness data (α=0.05). Levene test was used to evaluate the prevision (α=0.05).
The Mx group obtained a trueness mean value of 54 ± 17 µm and a mean precision value of 54 ± 17 µm, while the Mb group presented a trueness mean value of 67 ± 23 µm and a mean precision value of 66 ± 22 µm. The Mx group demonstrated significantly better trueness than the Mb group (P<.001). The G0 and G1 subgroups had the highest trueness values among the subgroups tested. No significant difference was observed between G0 and G1, G1 and G2, and G2 and G3 subgroups in trueness and precision. However, the G0 had significantly better trueness and precision values compared to G2 and G3 subgroups. In addition, the G1 had significantly better trueness values than the G3 subgroup. However, the Levene test revealed no difference in the precision mean values among the subgroups tested.
Implant scanning trueness was affected by the dental arch and the number of rescanned mesh holes using the IOS tested. A higher number of rescanned mesh holes decreased the scanning trueness. The stitching algorithm of the IOS software tested after the mesh hole scan demonstrated a significant error, especially when multiples mesh holes are involved in the same arch.
Given that cutting-off and rescanning techniques can reduce trueness, clinicians should consider whether these techniques are necessary in complete digital workflows. This is particularly important when fabricating multiple single implant-supported restorations in the same arch.

To evaluate whether the cutting-off and rescanning procedures have an impact on the accuracy (trueness and precision) of the intraoral digital scan.
A right quadrant digital scan (reference scan) of a participant was obtained using an intraoral scanner (IOS) (TRIOS 4; 3Shape A/S, Copenhagen, Denmark). The reference scan was duplicated 135 times and divided into 3 groups based on the number of rescanned mesh areas: 1 (G1 group), 2 (G2 group), and 3 (G3 group) mesh holes. Each group was subdivided into 3 subgroups depending on the mesh hole diameter: 2 mm- (G1-2, G2-2, and G3-2), 4 mm- (G1-4, G2-4, and G3-4), and 6 mm- (G1-6, G2-6, and G3-6) (n = 15). A software program (Geomagic; 3D Systems, Rock Hill, SC, USA) was used to assess the discrepancy between the reference and the experimental scans using the root mean square (RMS). Kruskal-Wallis and post hoc multiple comparison Dunn\'s tests were used to analyze the data (α=0.05).
Trueness ranged from 5 to 20 µm and precision ranged from 2 to 10 µm. For trueness assessment, Kruskal-Wallis test revealed significant differences on the RMS error values among the groups tested (P<.05). The G3-6 group obtained the lowest trueness and lowest precision values, while the G1-2, G1-4, G2-2, G2-4, and G3-2 groups computed the highest trueness and precision values. When comparing groups with the same number of rescanned mesh holes but with different diameter, the higher the diameter of the rescanned mesh hole, the lower the trueness values computed; however, when comparing groups with the same diameter of the rescanned mesh hole but with differing number of rescanned mesh holes, no significant differences were found in the RMS values among the groups. For the precision evaluation, Levene\'s test showed a lack of equality of the variances, and therefore of the standard deviations. The F-test with Bonferroni correction identified significant differences between the SDs between group G3-6 and all the other groups. When comparing instead the interquartile range (IQRs) due to the non-normality of the data, groups G1 and G2 also showed lower IQR values or higher precision than groups G3.
Cutting-off and rescanning procedures decreased the accuracy of the IOS tested. The higher the number and diameter of the rescanned areas, the lower the accuracy.
Cutting-off and rescanning procedures should be minimized in order to increase the accuracy of the IOS evaluated. The intended clinical use of the intraoral digital scan is a critical factor that might determine the scanning workflow procedures.

To measure the impact of different scanning patches on the accuracy (trueness and precision) of an intraoral scanner (IOS).
A typodont was digitized using an industrial optical scanner (GOM Atos Q 3D 12 M) to obtain a reference mesh. The typodont was scanned using an IOS (TRIOS 3). Three groups were generated based on the rescan areas created: no mesh holes (G0 group), 3 mesh holes distributed on the digital scan (G1 group), and 3 mesh holes located on the left quadrant of the digital scan (G2 group). In the G0 group, a digital scan was completed following the manufacturer\'s scanning protocol. In the G1 group, a digital scan was obtained following the same protocol as G0 group. Three 12-mm diameter holes were created in the occlusal surfaces of the left second first molar, incisal edges of the central incisors, and right first molar of the digital scan using the IOS software. In the G2 group, a digital scan was obtained following the same protocol as G0 group. Three 12-mm diameter holes in the digital scan were created in the occlusal surface of the left first molar and left second and first premolars using the IOS software program. The discrepancy between the control and the experimental digital scans was measured using the root mean square calculation. The Kolmogorov-Smirnov test demonstrated that data were normally distributed. One-way ANOVA followed by post hoc multiple comparison Bonferroni test were used to analyze the data (α = .05).
Trueness values ranged from 15 to 26 μm and the precision ranged from 21 to 150 μm. Significant differences in trueness mean values were found among the groups tested (F(2, 42) = 6.622, P = .003); the Bonferroni test indicated significant mean differences between the G0 and G2 groups (mean difference=0.11, SE=0.003, and P = .002). For precision evaluation, significant precision differences were found between the groups tested (F(2, 39)=9.479, P < .001); the Bonferroni test revealed significant precision differences between G0 and G2 groups (mean difference=-0.12, SE=0.030, and P = .001).
Rescanning mesh holes and stitching procedures decreased the trueness and precision of the IOS tested; furthermore, the number and dimensions of mesh holes rescanned represented an important factor that influenced the scanning accuracy of IOS tested.
It is a fundamental procedure obtaining intraoral digital scans without leaving mesh holes, so the rescanning techniques are minimized and, therefore, the scanning accuracy of the intraoral scanner tested is maximized.