Bond strength of HEMA-containing versus HEMA-free self-etch adhesive systems to dentin

Abstract

This study analyzed the bond strength (BS) of HEMA versus HEMA-free self-etch adhesive systems to dentin. The occlusal surface of 20 third molars was removed and the dentin was abraded with 600-grit silicon carbide paper. The teeth were randomly assigned to 4 groups (n=5) and restored with GO, Adper SE Plus, OptiBond All-In-One, and Clearfil 3S Bond adhesive systems and Filtek Z350 composite. After light curing (600 mW/cm²), the teeth were stored in distilled water at 37ºC for 24 h and were sectioned in the mesiodistal and buccolingual directions to obtain sticks (0.8 mm²). The sticks were subjected to tensile force using a universal testing machine (0.5 mm/min), and the modes of failure were analyzed by scanning electron microscopy and classified as adhesive, cohesive, or mixed. The BS data (in MPa) were treated using one-way ANOVA and Tukey's tests at 5% significance. GO presented the lowest mean bond strength value (10.57 ± 3.72) and differed significantly from the other materials (p=0.001), which, in turn, presented statistically similar results (p>0.05) among themselves: Adper SE Plus (29.08 ± 8.93), OptiBond All-In-One (28.36 ± 6.49), and Clearfil 3S Bond (28.62 ± 6.97). Mixed fractures were the most prevalent. It was concluded that the influence of HEMA on BS to dentin was material dependent.

Bond strength to dentin of total-etch and self-etch adhesive systems

“…Self-etch systems employ water as their main solvent. In addition to the basic roles of solvents in adhesive systems, in these products, water has the additional function of ionizing acid monomers, thus allowing them to condition the structure of the tooth 10,28 . Some self-etch systems combine water and another solvent to achieve better results.…”

“…The key characteristic of these systems is that they skip the acid etching stage prior to application 10 , greatly decreasing the level of technical sensitivity required 11 , particularly because they obviate the need for optimal dentin moisture, which is required for total-etch systems [12][13][14][15] . Unlike conventional adhesive systems, self-etch systems have added monomers added to their composition that ensure etching of the dental structure, so that, as soon as an area of the tooth is etched (or decalcified), it is immediately occupied by the resin monomer 7,16 .…”

Microtensile Bond Strength of One vs Two Layer Applications of Three Disposable Seventh Generation Adhesives

“…Two of them may balance the solvent evaporation without dehydrating dentin, because acetone volatilizes rapidly and dehydrates the dentin and ethanol ensures the wetness of the substrate. The surfactant monomers may facilitate the penetration of hydrophobic components into dentin, reducing phase separation [7] and this property seems to contribute to a complete inter diffusion of the system all over the etched area.…”

“…The latest generation all-in-one adhesive have combined these steps into a single-step application for simpler and faster application [3][4][5][6]. All-in-one adhesive are mixtures of hydrophobic and hydrophilic monomers and solvents, combining etching, priming and bonding into a single product [3,[7][8][9]. They are mixed together immediately before use and then applied to tooth substrate and some of them were presented as a mixture of these adhesives.…”

“…The authors suggested the removal of the HEMA from these adhesives to minimize the water sorption. Studies showed a positive correlation between water sorption and the degree of hydrophilicity of these adhesives [7,12] but it was suggested that the 10% of HEMA would be beneficial for the performance of these adhesives [13].…”