Adhesive layer properties as a determinant of dentin bond strength

Abstract

The goal of this study is to evaluate the hypothesis that the properties of the resin adhesive might affect the microtensile bond strength (MTBS) of multibottle dental adhesive system. In order to alter the properties, the experimental resin adhesives containing 2,2-bis (4-2-hydroxy-3-methacryloyloxypropoxyphenyl)propane (Bis-GMA) and triethylene glycol dimethacrylate (TEGDMA) at various ratios were prepared. Degree of conversion immediately after curing (DC-immed), degree of conversion at 48 h after curing (DC-48h) of a thin coat of the experimental adhesives, the flexural strength (FS) of the bulk specimens made of the experimental adhesives, pH, viscosity at shear rate of 1 S(-1), and the microtensile bond strength (MTBS) values of the adhesives to dentin were investigated. The maximum MTBS and FS values of the resin adhesives were observed when the ratio of Bis-GMA/TEGDMA was 60/40. However, pH and viscosity values increased with increasing Bis-GMA content in the adhesives. When Bis-GMA content was more than 60 wt %, the viscosity increased exponentially and restricted the DC and FS, and accordingly decreased the bond strength. The stronger the resin adhesives were, the higher the bond strength to dentin could be obtained.

Impact of Adhesive Application and Moisture on the Mechanical Properties of the Adhesive Interface Determined by the Nano-indentation Technique

“…There is a known solvent concentration at which maximum conversion is reached, more or less solvent than this amount can decrease monomer conversion, 27 which seems related to the viscosity of the adhesive film. 24 Although not measured in this study, it was visually evident that OSP is far more fluid than SBP. Thus, one can assume that the remaining water from the wet bonding technique could have been beneficial to the SBP by increasing the flowability of the adhesive, enlarging the mobility of the reactive components during polymerization and resulting in increased nanohardness values.…”

“…[21][22][23] The current investigation does not agree with the first hypothesis raised by Dal-Bianco and others 15 and Reis and others. 16,24 It only agrees with the second. If higher water/solvent evaporation had occurred, one would expect high nanohardness and Young's modulus values at the adhesive layer when the adhesive was vigorously applied in the dry environment.…”

“…Exactly the opposite response was expected, due to previous literature findings that demonstrated that the degree of polymerization is negatively correlated with the amount of solvent presented in the adhesive, [24][25][26] meaning that the higher the amount of water/solvent, the lower the degree of polymerization. The behavior of One Step Plus was indifferent, meaning that, regardless of the mode of application or degree of substrate moisture, the nanohardness and Young's modulus was not affected.…”

The effect of the strength and wetting characteristics of Bis-GMA/TEGDMA-based adhesives on the bond strength to dentin

“…When Bis-GMA was used in fractions of more than 60 wt% in a Bis-GMA/TEGDMA mixture, that is, less than 40 wt% TEGDMA, autodeceleration of the polymerization reaction decreased the DC owing to the increased viscosity in the adhesive mixtures. 4 However, in the Bis-M-GMA/TEGDMA mixture, a decrease of TEGMDA content to 20 wt% had no influence on the DC of the experimental adhesive due to low viscosity of Bis-M-GMA. Although the molecular weight of Bis-M-GMA is greater than that of Bis-GMA, Bis-M-GMA is relatively free from diffusion limitations due to the absence of hydrogen bonds.…”

“…2 Improvement in the mechanical properties of the adhesive layer is an important factor in increasing dentin bond strength. 3,4 There were various efforts to increase the mechanical properties of the adhesive layer; loading fillers, increasing the degree of conversion and improving the monomer system. It was suggested that adding fillers to the adhesives would increase the mechanical strength of the adhesive layers.…”