Comparative evaluation of the morphological accuracy of dental crowns fabricated by different technologies.

STATEMENT OF PROBLEM: Information on the morphological accuracy of crowns produced by different technologies is limited. PURPOSE: The purpose of this in vitro study was to compare the morphology and contacts of crowns fabricated with intraoral systems, extraoral systems, and conventional method. MATERIAL AND METHODS: A typodont mandibular first molar (Nissin Dental Product) received a complete ceramic crown preparation and a reference crown. Microcomputed tomography (muCT) was used to obtain the virtual data (REF) of the reference crown. Three groups of replicated crowns were made: intraoral scanning system (TRIOS), extraoral scanning system (D700), and the conventional method (CONV) (n=8). The groups TRIOS and D700 were designed by the correlation method. All crowns were scanned with muCT to obtain 3D data. The data were superimposed on each other or the REF in an inspection software to evaluate precision and trueness. The contact penetration area of the occlusal surfaces of the crowns was calculated. An independent sample t test and 1-way ANOVA with the post hoc least significant difference (LSD) test were used to compare the data (alpha=.05). RESULTS: The crowns fabricated with the extraoral scanners showed significantly lower root mean square (RMS) values for trueness (F=1456.90, df=2, P<.001) and precision (F=188.88, df=2, P<.001) than the others. The penetration contact area ratio and the differences in the CONV group were both significantly higher than those of the other groups. CONCLUSIONS: The average discrepancies of the crown morphology fabricated from the extraoral scanning were significantly lower than those from others. The conventional method restored the occlusal contact with significantly less accuracy than the other groups.