ABSTRACT
PURPOSE: This study compared the fatigue life of human maxillary premolars restored with direct composites and indirect ceramic inlays in mesio-occlusodistal (MOD) cavities. MATERIALS AND METHODS: Ten human maxillary premolars were divided into two groups of five and restored with (1) direct composite restorations, or (2) pressed ceramic restorations. Standardized MOD cavities were prepared for both groups. Teeth in the direct composite group were restored with Z250 composite and Single Bond adhesive, and those in the ceramic group were restored with IPS Empress ceramic inlays. The ceramic inlays were luted with Single Bond and RelyX ARC cement. Under the applied test load of 11.17 kg, strain measurements were recorded from an electric resistance stain gauge bonded to the buccal surface. These strains were recorded for the (1) intact tooth, (2) cavity preparation, and (3) restored tooth. These strain measurements were used to calculate the relative tooth compliance values for each tooth. The fatigue loading was applied until reinforcement loss was registered by the strain gauge. RESULTS: A one-way ANOVA showed no significant compliance difference between the intact and restored tooth conditions, and no significant difference in fatigue cycles to failure between the two groups. CONCLUSION: There were both adhesive and cohesive failures in both restoration groups, indicating that the adhesive joint is not the only weak link in these restorations.
Subject(s)
Ceramics/chemistry , Composite Resins/chemistry , Dental Bonding , Dental Cavity Preparation/classification , Dental Restoration, Permanent , Inlays , Tooth/physiopathology , Aluminum Silicates/chemistry , Analysis of Variance , Bisphenol A-Glycidyl Methacrylate/chemistry , Compliance , Dental Porcelain/chemistry , Dentin-Bonding Agents/chemistry , Humans , Materials Testing , Polyethylene Glycols/chemistry , Polymethacrylic Acids/chemistry , Resin Cements/chemistry , Stress, Mechanical , Surface PropertiesABSTRACT
PURPOSE: This study determined the effect of bonding a composite core on the number of load cycles to cement failure for teeth restored with complete crowns. MATERIALS AND METHODS: Ten extracted human maxillary central incisors were divided into two groups of five each. The tooth roots were at least 11 mm long, allowing an 8-mm post. Under copious irrigation, each tooth was cut to a flat plane 1 mm coronal to the buccal cementoenamel junction, perpendicular to the long axis of the tooth. The canal space was prepared to a final diameter of 1.25 mm, 8 mm deep. Each tooth was rebuilt with a 050 Parapost and Corestore. Final preparation height was 7 mm, including a 1-mm ferrule. For group 1, the core was bonded to the dentin using autocured Scotchbond Multipurpose Plus. For group 2, the core was not bonded. Following crown cementation, all teeth were subjected to a fatigue load of 4 kg at a rate of 280 cycles per minute. RESULTS: One tooth with a bonded core failed at 19,880 cycles, and the other four in this group did not fail after 100,000 cycles. All of the teeth without a bonded core failed at a cycle count of less than 100. The Mann-Whitney nonparametric test showed a significant difference between the two groups (P < .01). CONCLUSION: Bonding of a composite core to dentin prior to crown cementation provided a significantly stronger crown retention under fatigue loading.