Effect of Abutment Tooth Geometry On The Accuracy of Fixed Prosthodontics Casts Obtained by Digital and Analog Workflows-In Vitro Study.

Abstract

Objective: Physical and digital casts are required for fixed dental prosthesis (FDP) fabrication. However, the effect of abutment tooth geometry on the accuracy of FDP casts obtained by digital and analog workflows remains unclear. This study evaluated the accuracy of obtaining dental casts for veneer and full crowns with digital and analog workflows.

Materials and methods: A typodont model of the maxilla with unprepared teeth and veneer and full crown preparations was digitalized with intraoral scanning (TRIOS 3; 3Shape), digital model (DM) group, and the digital files were exported to two additive manufacturing technologies, resulting in the groups digital light processing (DLP) (Hunter; FlashForge) and polyjet (PLJ) (Eden 500 V; Stratasys). In addition, plaster casts (PCs) were obtained with polyvinyl siloxane (Express XT; 3M ESPE) double impressions and type IV plaster (FujiRock; GC America) as a control group. The sample size per group (n = 6) was defined in the pilot study. The digitization of the typodont and experimental casts was performed with a laboratory scanner (inEos X5; Dentsply Sirona). The measurement deviation (trueness and precision) to the reference model was performed with reverse engineering software (Geomagic Control X 2018; 3D Systems). Two-way ANOVA was used to assess the effect of manufacturing techniques and abutment tooth geometry on model accuracy (primary outcome). In addition, one-way ANOVA was used to assess significant differences between manufacturing techniques for complete arches, including abutments and unprepared teeth (secondary outcome). Tukey post hoc tests were used to compare means among groups. All statistical analyses considered a significant level of p ≤ 0.05.

Results: Statistically significant interactions were observed between manufacturing technique and abutment tooth geometry, affecting both trueness (p < 0.001) and precision (p < 0.001). For trueness, DM exhibited the lowest RMS values (p < 0.001), PC and DLP showed no significant difference (p = 0.056), and PLJ had significantly higher values than other techniques (p < 0.001), while premolar and molar preparations displayed significantly lower discrepancies compared to other types (p < 0.002). For precision, DM had the lowest values (p < 0.001), with PC also showing low values (p < 0.001), and no significant differences were observed between DLP and PLJ (p = 0.986). Veneer, premolar, and molar crown preparations demonstrated significantly lower RMS compared to anterior crowns.

Conclusion: The design of the abutment tooth significantly influenced the trueness and precision of FDP casts obtained by digital and analog workflow. For trueness, DM exhibited the highest accuracy, outperforming PC, DLP, and PLJ and achieving better results with premolar and molar preparations compared to anterior crowns and veneers. For precision, DM was most accurate, followed by PC, DLP, and PLJ, with veneer, premolar, and molar crowns consistently outperforming anterior crowns.