Effect of the Absence of HEMA on the Bonding Properties of Universal Adhesive Systems Containing 10-MDP: An In Vitro Study
To evaluate the absence of 2-hydroxyethyl methacrylate (HEMA) on the adhesive properties with enamel and dentin of universal adhesive systems containing 10-methacryloyloxydecyl dihydrogen phosphate (MDP). One hundred and twelve caries-free third molars were used to test adhesion to dentin (n=64) and enamel (n=48). For each substrate, teeth were divided into eight experimental groups: four different adhesives each using two adhesive strategies. The adhesives used were: (1) Scotchbond Universal (SBU, 3M Oral Care, St Paul, MN, USA) as a HEMA-containing universal adhesive; (2) Gluma Bond Universal (GBU, Kulzer, Hanau, Germany); (3) Solare Universal Bond (SUB, GC, Tokyo, Japan); and (4) Zipbond Universal (ZIP, SDI, Victoria, Australia) as HEMA-free universal adhesives. The adhesive strategies used were etch-and-rinse (ER) and self-etch (SE). For dentin tests, the occlusal third of the crown of all teeth was removed and an adhesive protocol was applied. After completing the restoration, specimens were sectioned into bonded sticks (0.8 mm 2) and tested for microtensile bond strength (μTBS), in situ degree of conversion (DC), and nanoleakage (NL) by scanning electron microscopy. For enamel tests, teeth were sectioned into four parts (buccal, lingual, and proximal), and an adhesive protocol was applied. After completing the restoration, the specimens were tested for their microshear bond strength (μSBS). For in situ degree of conversion (DC) and nanoleakage (NL) evaluation of enamel, the specimens were sectioned in slices to be evaluated. The data for each substrate were subjected to two-way ANOVA and Tukey’s test (α=0.05) for each property evaluated. The SBU and ZIP adhesives showed the highest μSBS, and DC (dentin and enamel) and lower NL (dentin) values compared to GBU and SUB (p=0.001). However, SBU showed better results in terms of μTBS and μSBS (SE strategy), and DC (dentin and enamel) than ZIP. Strategy ER presented higher values of μTBS and μSBS when compared to strategy SE (p=0.001), except for SBU. The effect of the absence of HEMA in commercial universal adhesive systems on enamel and dentin adhesive properties appears to be material-dependent.SUMMARY
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Methods and Materials
Results
Conclusion
Representative backscattered scanning electron microscope (SEM) images of the resin-dentin adhesive interfaces of each experimental group. Observe that the amount of nanoleakage was lower and practically occurred within the hybrid layer for Scotchbond Universal (A-B) and Zipbond Universal (G-H). For Gluma Bond Universal (C-D) and Solare Universal Bond (E-F), the amount of NL was higher than that of the other materials, with most silver nitrate uptake occurring throughout the entire thickness of the HL (white hands indicator). Abbreviaitons: C, composite; AL, adheslive layer, HL, hybrid layer, D, dentin.
Representative backscattered SEM images of the resin-enamel adhesive interfaces of each experimental group. Despite, no nanoleakage was observed in the Scotchbond Universal adhesive (A-B), usually, the amount of NL was so low in the other groups (Gluma Universal Bond; C-D, Solare Universal Bond, E-F and Zipbond Universal; G-H) that it was not possible to observe some significant difference among them. Only a few spots of silver nitrate uptake were observed (white hands indicators in E-H). Abbreviations: C, composite; AL, adheslive layer, E, enamel
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