| The composite resin inlays that had been secondary cured have the improvement in physical-mechanical properties, wear resistance, marginal microleakage and degree of conversion. Few research was reported on tooth resistance with different cured resin composite inlays. The purpose of this study was to compare the fracture resistance and microtensile bond strength (MTBS) of tooth with different cured resin inlays.Part I: Fracture resistance of tooth withdifferent cured resin inlaysObjictive: The purpose of this study was to evaluate the fracture resistance of in intact and restored tooth with different cured resin inlay. Materials and Methods: Fifty noncarious human maxillary premolars were divided into five groups, and each group included 10 samples. All samples were submitted to mechanical tests to evaluate their fracture resistance. The first three groups received mesio-occluso-distal cavity preparations and were respectively restored with (1) direct resin composite(Renew), (2) direct resin composite inlays(Renew), (3) indirect resin composite inlays(Tescera). Samples of group 4 were prepared butwere tested without restoration (prepared-only group). Samples of group 5 were intact teeth and were tested as control group. All samples were mounted in artificial stone and subjected to a compressive axial loading in an Instron Universal Testing Machine at 2mm/min crosshead speed. Results: The mean fracture strength was: Groupl: 2.06 ± 0.76KN, Group2: 2.30 ± 0.49KN, Group3: 2.62 ± 0.68KN, Group4: 1.24 ± 0.44KN, Group5: 2.40 ± 0.71KN. Statistical analysis indicated no significant (p<0.05) differences between Group 5 (intact teeth) and restored teeth groups(group 1,2,3), with direct restorations as well as indirect restorations. The prepared-only teeth(Group 4) were the weakest. Conclusion: Restored teeth were stronger than the prepared-only teeth. There was no relation between different cured resin inlays and fracture resistance.Part II: Microtensile bond strength to dentinof different cured resin compositeObjective: The purpose of this study was to evaluate the microtensile bond strength(MTBS) of different cured resin composite. Materials and Methods: Superficial occlusal dentin of 15 freshly extracted caries- and restoration-free human mandibular third molars was exposed, finished with Isomet Low Speed Saw under copious water spray, and a crown of different cured resin composite bonded with the adhesivesaccording to the manufacture's instructions. The teeth were stored in water at room temperature for 24h, and sectioned both mesial-distally and buccal-lingually along their long axis into 1.0x1.0mm2 sticks that were tested in tensile mode.Results: Although no significant difference was found among the different cured indirect composite restorations of Renew(20.06±4.96 Mpa) and Tescera(20.87±4.62 Mpa), the direct composite restorations of Renew(33.38±6.24Mpa) resulted in statistically higher bond strength than that of the two indirect composites restorations. Conclusion: The microtensile bond strength of direct composite restorations was higher than that of indirect composite restorations. There was no relation between different cured indirect composite restorations and microtensile bond strength.Part III: Studies on bonding interface of different curedresin composites by Scanning Electron Microscopy Objective: The purpose of this study was to investigate the microstructure and bonding mechanism of bonding interface of different cured resin composites.Materials and Methods: Superficial occlusal dentin of freshly extracted caries- and restoration-free human mandibular third molars was exposed, finished with Isomet Low Speed Saw under copious water spray, and a... |
