Evaluation of the accuracy of 2 digital intraoral scanners: A 3D analysis study.

STATEMENT OF PROBLEM: Evidence for the accuracy of a recently introduced intraoral scanner is lacking. PURPOSE: The purpose of this in vitro study was to evaluate and compare the trueness (validity) and precision (reliability) of 2 intraoral scanners by scanning a quadrant and a sextant. MATERIAL AND METHODS: A maxillary typodont with plastic teeth made from a shade A3 polymethyl methacrylate was scanned (n=10) with each intraoral scanner (Planmeca Emerald and 3Shape TRIOS 3) to obtain sextant and quadrant scans. Control scans were made with an industrial optical scanner. The scans were analyzed with a 3D reverse engineering software program and an independent samples t test and general linear model 2-way analysis of variance (α=.05). RESULTS: The 3Shape TRIOS 3 scanner showed no significant difference between the sextant and quadrant scans in trueness (P=.118) or in precision (P<.285). The Emerald scanner had statistically significant higher trueness for the sextant scan (P=.007). The 3Shape TRIOS 3 scanner had better performance in trueness and precision when compared with the Emerald scanner. CONCLUSIONS: The 3Shape TRIOS 3 scanner was found to be more accurate than the Emerald scanner in terms of trueness and precision, regardless of the scanning field. The Emerald scanner's trueness decreased as the scanning field increased from a sextant to a quadrant.

Efficacy of Several Retightening Protocols for Maintaining Clamping Force in the Implant-Abutment Joint: An In Vitro Pilot Study.

PURPOSE: Stability of an implant-supported restoration is an ultimate measure of the success of the procedure. It has been recommended by some to retighten the abutment screw for maintenance of the crown on the implant. The purpose of this study was to evaluate the usefulness of two retightening protocols to maintain the clamping force. MATERIALS AND METHODS: Three groups of slip-fit implants (MIS 4.3 by 10.5) were compared. The first group was only tightened once (group C). In the second group (group R10M), the screw was retightened after 10 minutes. The third group (group R2W) was retightened after 2 weeks of simulated functional loading. After completion of individual protocols, all specimens were loaded for 100,000 cycles. After the loading, all specimens had the remaining torque audited. RESULTS: The mean torque loss for group C was 6.10 (± 5.13) Ncm. Group R10M was 2.03 (± 3.018) Ncm, and group R2W was 0.30 (± 0.483) Ncm. A one-way analysis of variance (ANOVA) recorded significant differences among the groups (P = .003). Multiple pairwise comparisons between groups by Tukey test recorded significant differences between group C vs group R10M (P = .035) and group C vs group R2W (P = .002). There was no significant difference in torque loss between groups R10M and R2W (P = .509). CONCLUSION: Within the parameters of this in vitro investigation, it was concluded that both retightening after 10 minutes (P = .035) and after 2 weeks (P = .002) was equally effective.