Facial scanner accuracy with different superimposition methods - In vivo study.

PURPOSE: To compare trueness and precision between conventional and digital facial measurements and to evaluate the accuracy of different superimposition techniques for facial scans. MATERIALS AND METHODS: Twenty volunteers were recruited. Predetermined facial landmarks were marked with a black pen, and the interlandmark distances were measured manually with a conventional caliper and digitally with Geomagic software. Two consecutive facial scans were performed and superimposed using as best-fit reference the full face, the face without the eyes, and the bone-supported areas (eg, forehead and zygomatic areas) in order to assess root mean square (RMS) differences. Trueness and precision were evaluated and compared between the conventional and digital techniques. Mann-Whitney U and Kruskal-Wallis post hoc tests were used. The significance level was established at α = .05. RESULTS: Trueness between conventional and digital measurements was 1,151.75 ± 1,265.52 µm (3.04% ± 4.82%), and precision was 322.31 ± 300.54 µm (0.93% ± 1.10%). Global mean RMS values for each superimposition technique were 334.15 ± 172.07 for the full face, 339.57 ± 173.13 for the face without the eyes, and 385.65 ± 182.29 for the bone-supported areas, with the latter presenting statistically significant differences compared to the other two. CONCLUSION: Although statistically significant differences were detected in facial measurements, they were below the clinically detectable threshold. Superimposition with the full face and the face without the eyes area presented smaller discrepancies than with the bone-supported areas, with higher discrepancies in the lower third of the face.

Soft tissue replication in single unit implant impressions-A three dimensional clinical study.

OBJECTIVE: Comparison of soft tissue replication between conventional and digital impressions for definitive single unit implant rehabilitation in the esthetic zone. MATERIALS AND METHODS: Six patients were recruited according to inclusion criteria for this cross-over pilot study and submitted to a conventional silicone implant impression with customized coping and a digital impression with an intraoral scanner. Stereolithography files obtained from the same patient were superimposed with appropriate software and trueness evaluated between methods at predetermined locations (56 in hard and soft tissues and 18 in the emergence profile, per patient). Results were presented as mean root mean square (RMS) ± 95% confidence interval and effect size calculated with Hedges' g ± 95%. Mann-Whitney and Kruskal-Wallis were performed when appropriate and α was set at .05. RESULTS: Trueness between methods equated to 51.08[45.68;56.47] µm and 60.46[52.29;68.62] µm in hard and soft tissues, respectively. Soft tissue replication by intraoral scanner acquisition corresponded to a statistically significant RMS of 243.89[209.15;278.63] µm equating to a Hedges' g of 1.52[1.22;1.82] which corresponded to a large effect size. CONCLUSIONS: The proposed method could be considered for soft tissues assessment and the results suggest that intraoral impression techniques produce statistically significant changes in peri-implant soft tissue replication, although below the clinically detectable threshold. CLINICAL SIGNIFICANCE: The proposed technique allows for the 3D determination of peri-implant tissues changes in digital models with higher sensitivity than visual techniques, thus presenting itself as a promising alternative in clinical studies and that the use of an intraoral scanner obtained significant differences in the soft tissue emergence profile replication when compared with the gold standard.