Microtensile Bond Strength Evaluation of Composite Resin to Discolored Dentin After Amalgam Removal

Abstract

BackgroundTo obtain prolonged clinical success with composite restorations, better bonding of resin to the tooth substrate is crucial. AimThe study was aimed to evaluate the microtensile bond strength (µTBS) of bulk-fill composite resin restorations when bonded to a cavity previously restored with amalgam, comparing with that of freshly prepared dentin. Materials and methodMesio-occlusal cavity preparations were done on 80 extracted human mandibular molars with a buccolingual width of 4 mm and a 1.5 mm axial depth by placing the gingival seat 0.5 mm coronal to the cementoenamel junction (CEJ) and were restored with fine-grain amalgam alloy. After thermocycling, the amalgam restorations were removed. Disto-occlusal cavities with similar dimensions of mesial cavities were prepared, and both the proximal surfaces were filled with bulk-fill composite using either etch-and-rinse or self-etch adhesives. Following thermomechanical cyclic loading, all the teeth were sectioned for µTBS testing. Bond strength data expressed in megapascals (MPa) were subjected to statistical analyses using analysis of variance (ANOVA) and Tukey's multiple post-hoc tests.

Effect of Polywave and Monowave Light Curing Units on the Microtensile Bond Strength and Failure Types of Different Bulk-Fill Resin Composites: An in vitro Study

“…Both photoinitiators were stimulated by different wavelengths, which improved their mechanical properties. 5 , 14 , 37 , 39 The higher absorption of visible light by these photoinitiators could have contributed to their greater depth of cure. This did not occur with Filtek One Bulk Fill because it contained only CQ.…”

“…The test was performed on a universal testing machine (CMT-5L Liangong, Shandong, China) with digital software (Smart Test) at a crosshead speed of 0.5 mm/min. 6 , 13 , 14 , 27 , 30 The µTBS values obtained after the test were analysed in megapascals (MPa) [ Figure 3 ].

Figure 3 Microtensile bond strength testing.

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“…6,13 This makes it a more versatile alternative because multiple samples can be obtained from a single tooth, allowing for more assertive studies and better substrate control. 6,13,14 In addition, the clinical results of the microtensile bond strength evaluation were more reliable than those of the microshear bond strength testing. 15,16 The rationale for evaluating microtensile bond strength is that the stronger the bond between the tooth and the biomaterial, the greater the resistance of the restoration to stresses imposed by resin polymerization and oral function.…”

“…15,16 The rationale for evaluating microtensile bond strength is that the stronger the bond between the tooth and the biomaterial, the greater the resistance of the restoration to stresses imposed by resin polymerization and oral function. 6,13,14 Therefore, inadequate polymerization may result in reduced biocompatibility owing to the release of unreacted monomers, decreased mechanical properties, and decreased color stability. 5,17,18 Parallel to the advances in resin composites, there have also been improvements in the light-curing units.…”