Effects of increased exposure times of simplified etch‐and‐rinse adhesives on the degradation of resin–dentin bonds and quality of the polymer network

Abstract

One of the reasons for resin-dentin degradation is poor polymerization of the adhesive layer. This study evaluated the effect of prolonged polymerization times on the immediate and 6-month resin-dentin bond strengths, silver nitrate uptake, and polymer quality of etch-and-rinse adhesives. Thirty extracted teeth were obtained, and a flat dentin surface was exposed on each tooth. Adhesives (Adper Single Bond 2 and One Step Plus) were applied to the dentin surface of these teeth and light-cured for 10, 20, or 40 s at 600 mW cm(-2) . Bonded sticks (0.6 mm(2) ) were tested in tension (0.5 mm min(-1) ) and analyzed, after immersion in 50% silver nitrate, using scanning electron microscopy. The polymer quality of adhesive films was evaluated using thermogravimetric analysis. Statistically higher bond strengths were observed for both adhesives when light-cured for 40 s. Degradation of dentin bonds occurred under all experimental conditions but it was less pronounced for adhesives light-cured for 40 s. Longer exposure times reduced silver nitrate uptake for Adper Single Bond 2. Solvent retention and the amount of residual monomer were statistically lower when both adhesives were light-cured for 40 s. Although longer exposure times than those recommended cannot prevent degradation of the dentin bonds, they can increase bond strength, probably because of the removal of an increased amount of solvent and the presence of a lower amount of residual monomer.

The Use of Montmorillonite Clays as Reinforcing Fillers for Dental Adhesives

“…The second (T peak approximately 360 o C), third (T peak approximately 380 o C) and fourth losses of mass (T peak approximately 400 o C) can be assigned to the decomposition of higher molecular-weight structures, comprising the chain areas formed more intensely by flexible components such as HEMA and TEGDMA for the second and third stages, along with areas of greater rigidity in the fourth stage, with higher prevalence of BIS-GMA and UDMA. 18 Regarding thermal resistance, the groups containing 0.2% filler load showed an increase in thermal resistance while the other concentrations showed no significant changes in this property. This behavior can be explained based on the dispersion of layered nanofillers, since the group with 0.2%, possibly, has an exfoliated morphology.…”

“…The presence of these polymer systems in a more rigid conformation lead to a less tendency of water sorption, since the reduced flexibility of the polymer networks generates a physical obstacle to the passive diffusion of the solvent through the material. 30 Thus, once the sorption is the primarily responsible for the mechanical strength loss of the adhesive systems because its represent the first stage of degradation of these interfaces by hydrolysis, 31,32 or because the water acts as a plasticizer of these materials, 18,33 the obtaining of these systems with greater rigidity reflects on a larger adhesive stability.…”

Aumento de longevidad de restauraciones de resinas compuestas y de su unión adhesiva. Revisión de tema

“…Experimental and clinical tests 107,108 have demonstrated that including an extra hydrophobic layer in addition to the self-etching adhesive procedure improves the clinical behavior observed 6, 12, and 24 months after application, mainly in terms of retention of CR restorations performed on Class V non-carious cervical lesions, consecuencia de la disminución de la degradación de unión adhesiva. 90,109,110 Empero, estudios a mayor plazo clínico son necesarios para completar esta información.…”

“…121 La explicación a este fenómeno podría relacionarse con el hecho de brindar al adhesivo mayor tiempo para la evaporación de sus solventes alcohólicos y agua, especialmente cuando se conoce que la incorporación de agua en los sistemas as a result of lower degradation of adhesive bond. 90,109,110 However, longer-term clinical studies are required to complement this information.…”

“…121 The explanation to this phenomenon may be related to the fact of giving the adhesive agent more time to evaporate its alcohol solvents and water, especially since it has been well known that adding water to adhesive systems adhesivos ayuda a la formación de los canales de agua a través de la zona híbrida, cuando está asociada a alcoholes, esto ocurre porque con la adición de agua a los co-monómeros y al etanol resulta el incremento de la retención de ambos, etanol y agua en el sistema, porque los dos solventes pueden unirse a los hidrógenos de los monómeros. 122 El aumento del tiempo de exposición a la evaporación del sistema adhesivo después de su aplicación, mayor que el recomendado por los fabricantes no previene su degradación, pero es capaz de aumentar la fuerza de la unión en forma inmediata y hasta por seis meses, quizá como resultado de la cantidad de cadenas de polímeros, 110 lamentablemente mayores tiempos de estudio no están disponibles en la literatura.…”