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Volume 11 , Issue 4
July/August 1998

Pages 333-339

Effects of Preparation and Luting System on All-Ceramic Computer-Generated Crowns


PMID: 9758997

Purpose: Computer-aided design/computer-integrated machining (CAD/CAM) allows defect-oriented custom-shaping of the inside surfaces of all-ceramic crowns. The urpose of this study was to examine the effect of inside crown form on fracture strength of cemented and bonded crowns. Materials and Methods: Four preparation types were used: (1) classic with a butt should of 1.2 mm, abutment height of 4 mm, and 6-degree convergence, (2) like type 1 with mesio-occlusodistal cavity, (3) like type 1 with height reduced by 50%, and (4) like type 1 with abutment reduced by 100% plus a pulp chamber cavity. Crowns were CAD desgined on preparations 1 to 4 using identical outside morphology. Machined crowns were placed on abutments (a) without any media as controls (n = 15), (b) ceme nted (n = 15), and (c) bonded (n = 15), and wre loaded until fracture. Results: Zinc phosphate-cemented crowns (1b, 2b, 3b, and 4b) showed significant (P < 0.001) increase of fracture load values compared to uncemented control crowns (1a, 2a, 3a, 4a). Fracture load values of bonded crowns (1c, 2c, 3c) were significantly (P < 0.001) higher than those for cemented crowns. Bonded crowns with thick occlusal dimensions (3c and 4c) showed the highest fracture load values. Conclusion: Bonded all-ceramic CAD/CIM crowns with defect-oriented inside morphology and increased occlusal dimensions showed high fracture load values.

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