TRUENESS OF INTRAORAL SCANNER AT THE FINISH LINE OF FIXED PROSTHODONTIC ABUTMENTS: INFLUENCE OF FINISH LINE LOCATION, FINISH LINE REGION, AND GINGIVAL RETRACTION TECHNIQUE

Abstract

This clinical study evaluated the trueness of intraoral scanner at the finish lines of fixed prosthodontic abutments by examining the effects of finish line location, finish line region, and gingival retraction technique. Fifty abutment teeth from 9 patients were scanned intraorally using a TRIOS 5 intraoral scanner, with reference scans generated from conventional polyvinyl siloxane impressions, Type IV stone casts, and an E4 laboratory scanner. Trueness was assessed by comparing test and reference STL files using Geomagic Qualify 12 software. A total of 168 finish line regions were analyzed using a linear mixed model at α = 0.05. Finish line region showed a statistically significant main effect on RMS deviation (F(3, 111.34) = 7.998, p < .001), while finish line location (p = .061) and gingival retraction technique (p = .328) showed no significant main effects. A significant three-way interaction was observed (F(3, 119.79) = 7.891, p < .001). Pairwise comparisons revealed that the distal region exhibited significantly greater RMS deviations than the mesial and buccal regions. Overall mean RMS deviations were approximately 30 to 40 µm, which were within ranges previously reported as clinically acceptable marginal scan trueness.

Keywords: Intraoral Scanner, Trueness, Finish Line, Fixed Prosthodontics