Marit Øilo1, Ketil Kvam2, Nils Roar Gjerdet3. 1. Associate Professor, Department of Clinical Dentistry, Faculty of Medicine and Dentistry, University of Bergen, Bergen, Norway. Electronic address: marit.oilo@iko.uib.no. 2. Senior Engineer, Nordic Institute of Dental Materials, Songsveien, Oslo, Norway. 3. Professor, Department of Clinical Dentistry, Faculty of Medicine and Dentistry, University of Bergen, Bergen, Norway.
Abstract
STATEMENT OF PROBLEM: The effect of anatomic contour design in all or parts of zirconia crowns is uncertain regarding clinical reliability and survival rates. PURPOSE: The purpose of this in vitro study was to compare the load at fracture of monolithic, anatomic contour zirconia crowns with bilayered crowns with and without a cervical zirconia collar. MATERIAL AND METHODS: Thirty zirconia crowns were fabricated for a shallow chamfer molar preparation, 10 with a normal core-veneer design, 10 with a core-veneer design with an additional cervical collar of zirconia, and 10 with a monolithic, anatomic contour design. Veneering ceramic was applied to the first 20 specimens to create an anatomic form. All crowns were cemented to epoxy abutments and loaded until complete fracture with a clinically relevant test method. The fracture modes and load at fracture were recorded. RESULTS: Statistically significant differences were found in the load at fracture and fracture modes among the test groups (P<.001). All fractures except one initiated in the crown margin, mostly in the proximal region. The mean load at fracture was 4091 N for the normal core-veneer design, 4712 N for the collar design, and 6517 N for the monolithic, anatomic contour design. CONCLUSIONS: Monolithic, anatomical contour design gave higher loads at fracture than traditional core-veneer design. Crowns with a cervical zirconia collar had higher load at fracture than the core-veneer design, but lower than the monolithic crowns.
STATEMENT OF PROBLEM: The effect of anatomic contour design in all or parts of zirconia crowns is uncertain regarding clinical reliability and survival rates. PURPOSE: The purpose of this in vitro study was to compare the load at fracture of monolithic, anatomic contour zirconia crowns with bilayered crowns with and without a cervical zirconia collar. MATERIAL AND METHODS: Thirty zirconia crowns were fabricated for a shallow chamfer molar preparation, 10 with a normal core-veneer design, 10 with a core-veneer design with an additional cervical collar of zirconia, and 10 with a monolithic, anatomic contour design. Veneering ceramic was applied to the first 20 specimens to create an anatomic form. All crowns were cemented to epoxy abutments and loaded until complete fracture with a clinically relevant test method. The fracture modes and load at fracture were recorded. RESULTS: Statistically significant differences were found in the load at fracture and fracture modes among the test groups (P<.001). All fractures except one initiated in the crown margin, mostly in the proximal region. The mean load at fracture was 4091 N for the normal core-veneer design, 4712 N for the collar design, and 6517 N for the monolithic, anatomic contour design. CONCLUSIONS: Monolithic, anatomical contour design gave higher loads at fracture than traditional core-veneer design. Crowns with a cervical zirconia collar had higher load at fracture than the core-veneer design, but lower than the monolithic crowns.
Authors: Sanath K Shetty; Tharammal Fayaz; Mohammed Zahid; Karkala S Suhaim; Mallikarjun Ragher; Mohammed S Hasan Journal: J Pharm Bioallied Sci Date: 2020-08-28
Authors: Fernando Zarone; Maria Irene Di Mauro; Pietro Ausiello; Gennaro Ruggiero; Roberto Sorrentino Journal: BMC Oral Health Date: 2019-07-04 Impact factor: 2.757