Avaliação in vitro da associação das técnicas de aplicação da clorexidina e saturação da dentina por etanol na estabilidade da união resina-dentina

Abstract

The search for adhesive restorations that have greater durability in the oral cavity is constant. Enamel adhesion is already well established and resistant over time. The great challenge is to improve the adhesion of the resin to the dentin, since this substrate is more complex, presenting a greater amount of water in its composition, which directly compromises the adhesion process. In the literature, two major problems related to the degradation of the resin-dentin adhesive interface over time are highlighted: hydrolytic degradation, caused by the deleterious effects of the water inherent to the tooth and the adhesive material used; and the enzymatic degradation caused by the proteolytic enzymes, especially the metalloproneinases (MMP's) present in the dentin structure and that are activated after the acid conditioning. Several proposals have been tested to combat these problems. In the present work, we will focus on two strategies used to improve bond strength to dentin over time: the application of 2% chlorhexidine (CHX) and the ethanol wet-bonding technique (EWBT). The main objective was to evaluate in vitro the effects of the association of these two techniques on the bond strength values to dentin after 24h, 6 months and 12 months of storage in water by means of microtensile bond strength test. Two forms of association were used: the first applying the techniques in separate steps, the CHX technique being applied previously to EWBT; and the second by means of an experimental solution handled in a pharmaceutical laboratory composed of 2% CHX diluted in absolute ethanol solution and applied once in the exposed dentin and conditioned with phosphoric acid. The thesis was divided into two chapters that evaluate these techniques in vitro. The first chapter evaluated after 6 months the association of the techniques in separate steps in two types of adhesive systems (3-step and 2-step etch-and-rinse). It was concluded that the association was able to preserve the adhesive interface after the period evaluated only when using the 2- step adhesive system, presenting RU values statistically superior to the control group of this adhesive. The second chapter evaluated after 12 months the association of singlestep techniques by mixing the two solutions (CHX and absolute ethanol) using a etchand-rinse 2-step adhesive system. The results showed that the mixture of solutions applied in a single step was not able to preserve the adhesive interface after the period evaluated, in addition to presenting the worst results when compared to the other techniques tested, with a reduction of RU values of 55.65 %, thus not being an option to improve the longevity of adhesive interfaces.