The effect of finish line curvature on marginal fit of all-ceramic CAD/CAM crowns and metal-ceramic crowns

Objectives: To investigate the effect of abutment finish line curvature on the fit of allceramic CAD/CAM crowns and metal-ceramic crowns. Method and Materials: Three types of finish line curvature abutments (1-, 3-, and 5-mm curvature) were prepared on typodont maxillary central incisors. For each type of abutment, 5 all-ceramic crowns (Cercon system, DeguDent) and 5 metal-ceramic crowns were fabricated. The marginal gaps of copings and veneered crowns were measured on a profile projector. The data were calculated and analyzed with 2-way ANOVA and Tukey HSD test (α = .05). Results: The mean labial, lingual, mesial, and distal marginal gaps (SD) of all-ceramic crowns were similar: respectively, 54 (10), 51 (11), 47 (13), and 49 (9) µm for 1-mm curvature; 49 (12), 53 (11), 54 (10), and 55 (12) µm for 3-mm curvature; and 57 (12), 54 (11), 53 (10), and 52 (9) µm for 5-mm curvature. The mean labial, lingual, mesial, and distal marginal gaps (SD) of metal-ceramic crowns were 36 (7), 41 (9), 26 (8), and 28 (10) µm, respectively, for 1-mm curvature. The mean labial and lingual marginal gaps (SD) of metal-ceramic crowns for 3-mm curvature were 45 (8) and 48 (9) µm, respectively-significantly larger than mesial (P = .01 and .007) and distal (P = .03 and .02) gaps. The mean labial and lingual marginal gaps (SD) of metal-ceramic crowns for 5-mm curvature were 76 (10) and 74 (15) µm, respectively-significantly larger than mesial (P = .001 and .001) and distal (P = .001 and .001) gaps. Conclusions: The abutment finish line curvature had no significant effect on the marginal fit of all-ceramic crowns, but had a significant effect on the marginal fit of metal-ceramic crowns. Keywords: all-ceramic CAD/CAM crowns, finish line curvature, fit, metal-ceramic crowns