Marginal accuracy and fracture strength of Targis/Vectris Crowns prepared with different preparation designs

Song, Ho Yong; Cho, Lee Ra

Abstract

STATEMENT OF PROBLEM: Targis/Vectris restorations provide excellent esthetics. Marginal accuracy is significantly influenced by the preparation design. There were no studies to examine the effect of preparation design on the marginal discrepancy and fracture strength of Targis/Vectris crowns. PURPOSE: This study evaluated the marginal accuracy before and after cementation, and the fracture strength of FRC/Ceromer(Targis/Vectris) crowns according to different preparation design. MATERIAL AND METHOD: Three metal dies with different convergence angles(6degrees, 10degrees, 15degrees) were prepared. Total 30 (10 for each angle) Targis/Vectris crowns were made. The restorations were evaluated for adaptation of the margin before and after cementation, then were compressively loaded to failure. Fracture surfaces of the crowns were examined using a SEM. Results. The mean marginal gap was 49micrometer for 6degrees, 55micrometer for 10degreesand 70micrometer for 15degreesand in clinically acceptable level. The mean marginal gap increased significantly after cementation. The increasing amount during cementation was the largest in the 6degrees group. The crowns on 6o convergence angle had a significantly higher fracture strength than the crowns on 15degrees angle. Mean fracture strength of total crowns regardless of convergence angle was 1390 N, which was higher than all-ceramic crowns. SEM observation showed two-mode fracture pattern.
CONCLUSION
From the results of this study, all of the FRC/Ceromer crowns had clinically acceptable marginal accuracy and could withstand the bite force. Moreover, less convergent angle than all-ceramic crown might be recommended for preparation procedure.