Abstract
BackgroundThe objective of this study was to investigate the influence of Er,Cr:YSGG laser irradiated at different powers on the micromorphology and the bonding property of non-carious sclerotic dentin to resin composites.MethodsTwo hundred bovine incisors characterized by non-carious sclerotic dentin were selected, and the seventy-two teeth of which for surface morphological analysis were divided into nine groups according to various treatments (A: the control group, B: only treated with the adhesive Adper Easy One, C: diamond bur polishing followed by Adper Easy One, D-I: Er,Cr:YSGG laser irradiating at 1W, 2W, 3W, 4W, 5W, 6W output power, respectively, followed by Adper Easy One). The surface roughness values were measured by the non-contact three-dimensional morphology scanner, then the surface micromorphologies of surfaces in all groups were assessed by scanning electron microscopy (SEM); meanwhile, Image Pro-Plus 6.0 software was used to measure the relative percentage of open tubules on SEM images. The rest, one hundred twenty-eight teeth for bond strength test, were divided into eight groups according to the different treatments (A: only treated with the adhesive Adper Easy One, B: diamond bur polishing followed by the above adhesive, C-H: Er,Cr:YSGG laser irradiating at 1 W, 2 W, 3 W, 4 W, 5 W, 6 W output power, respectively, followed by the above adhesive), and each group was subsequently divided into two subgroups according to whether aging is performed (immediately tested and after thermocycling). Micro-shear bond strength test was used to evaluate the bond strength.ResultsThe 4W laser group showed the highest roughness value (30.84±1.93μm), which was statistically higher than the control group and the diamond bur groups (p<0.05). The mean percentages ((27.8±1.8)%, (28.0±2.2)%, (30.0±1.9)%) of open tubules area in the 4W, 5W, 6W group were higher than other groups (p<0.05). The 4W laser group showed the highest micro-shear bond strength not only in immediately tested (17.60±2.55 PMa) but after thermocycling (14.35±2.08MPa).ConclusionThe Er,Cr:YSGG laser at 4W power can effectively improve the bonding property between non-carious sclerotic dentin and resin composites by increasing the roughness and mean percentage area of open tubules.
Highlights
Due to the complexity of dentin, bonding of dental materials to dentin substrates has attracted increasing attention among dental researchers
A variety of pathological dentin substrates are encountered in clinical practice, which mainly includes carious and non-carious sclerotic dentin
Two hundred freshly extracted bovine incisors with exposed non-carious sclerotic dentin on the lingual surface, clinically characterized by a vitreous appearance [24], physiologically discolored, caries-free, and undamaged [25] were collected from animals at least 3 years old [26] which had been slaughtered in Yunfeng Animal Husbandry, a local slaughterhouse located in the suburb of Xi’an, Shaanxi Province in China, for meat business
Summary
Due to the complexity of dentin, bonding of dental materials to dentin substrates has attracted increasing attention among dental researchers. In vitro studies [2] have demonstrated that for etch-and-rinse adhesives, bond strength values for sclerotic dentin are 25%– 40% lower than those achieved for sound dentin. This reduction is due to partial or complete obliteration of the dentinal tubules with mineral crystals and the presence of an acid-resistant hyper-mineralized layer that acts as an acid-resistant substrate to hinder penetration of the resin. The objective of this study was to investigate the influence of Er,Cr:YSGG laser irradiated at different powers on the micromorphology and the bonding property of non-carious sclerotic dentin to resin composites
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