Yang Yang1, Zhen Yang1, Jianfeng Zhou2, Li Chen3, Jianguo Tan4. 1. Graduate student, Department of Prosthodontics, Peking University School and Hospital of Stomatology & National Clinical Research Center for Oral Diseases & National Engineering Laboratory for Digital and Material Technology of Stomatology & Beijing Key Laboratory of Digital Stomatology, Beijing, PR China. 2. Associate Professor, Department of Prosthodontics, Peking University School and Hospital of Stomatology & National Clinical Research Center for Oral Diseases & National Engineering Laboratory for Digital and Material Technology of Stomatology & Beijing Key Laboratory of Digital Stomatology, Beijing, PR China. 3. Associate Professor, Department of Prosthodontics, Peking University School and Hospital of Stomatology & National Clinical Research Center for Oral Diseases & National Engineering Laboratory for Digital and Material Technology of Stomatology & Beijing Key Laboratory of Digital Stomatology, Beijing, PR China. Electronic address: dentistchenli@gmail.com. 4. Professor, Department of Prosthodontics, Peking University School and Hospital of Stomatology & National Clinical Research Center for Oral Diseases & National Engineering Laboratory for Digital and Material Technology of Stomatology & Beijing Key Laboratory of Digital Stomatology, Beijing, PR China.
Abstract
STATEMENT OF PROBLEM: Although different preparation designs have been proposed for onlays fabricated by computer-aided design and computer-aided manufacturing (CAD-CAM), their effect on marginal adaptation is unclear. PURPOSE: The purpose of this in vitro study was to investigate the effect of tooth preparation designs on the marginal and internal adaptation of ceramic-reinforced composite resin CAD-CAM onlays. MATERIAL AND METHODS: A traditional preparation with a heavy chamfer on the functional cusp and a contrabevel on the nonfunctional cusp and a shoulder preparation with equal reduction on all cusps were used for mesial-occlusal-distal (MOD) onlay preparations. Ceramic-reinforced composite resin onlays were designed and milled based on the scanned prepared teeth. A digital silicone replica technique was used to determine marginal discrepancies between preparations and onlay restorations. A total of 100 numeric distances (representations of the fit in each region) were measured in 3 distinct regions: the buccal margin, lingual margin, and internal area. Independent Student t tests were used to determine significant differences (α=.05). RESULTS: Traditional preparation designs resulted in significantly smaller overall discrepancies (50.9 ±0.5 μm and 139.1 ±5.4 μm, P<.001) and smaller marginal discrepancies in the buccal (49.7 ±1.4 μm and 135.8 ±2.2 μm, P<.001) and lingual areas (47.1 ±1.0 μm and 133.4 ±1.1 μm, P<.001). CONCLUSIONS: The marginal adaptation of ceramic-reinforced composite resin CAD-CAM onlays was affected by the preparation design. The traditional preparation design offered better marginal adaptation; therefore, it is recommended in clinical practice.
STATEMENT OF PROBLEM: Although different preparation designs have been proposed for onlays fabricated by computer-aided design and computer-aided manufacturing (CAD-CAM), their effect on marginal adaptation is unclear. PURPOSE: The purpose of this in vitro study was to investigate the effect of tooth preparation designs on the marginal and internal adaptation of ceramic-reinforced composite resin CAD-CAM onlays. MATERIAL AND METHODS: A traditional preparation with a heavy chamfer on the functional cusp and a contrabevel on the nonfunctional cusp and a shoulder preparation with equal reduction on all cusps were used for mesial-occlusal-distal (MOD) onlay preparations. Ceramic-reinforced composite resin onlays were designed and milled based on the scanned prepared teeth. A digital silicone replica technique was used to determine marginal discrepancies between preparations and onlay restorations. A total of 100 numeric distances (representations of the fit in each region) were measured in 3 distinct regions: the buccal margin, lingual margin, and internal area. Independent Student t tests were used to determine significant differences (α=.05). RESULTS: Traditional preparation designs resulted in significantly smaller overall discrepancies (50.9 ±0.5 μm and 139.1 ±5.4 μm, P<.001) and smaller marginal discrepancies in the buccal (49.7 ±1.4 μm and 135.8 ±2.2 μm, P<.001) and lingual areas (47.1 ±1.0 μm and 133.4 ±1.1 μm, P<.001). CONCLUSIONS: The marginal adaptation of ceramic-reinforced composite resin CAD-CAM onlays was affected by the preparation design. The traditional preparation design offered better marginal adaptation; therefore, it is recommended in clinical practice.