Effect of Dentin Preparation Mode on the Bond Strength Between Human Dentin and Different Resin Cements

Abstract

The aim was to evaluate the influence of different dentin preparation mode in the smear layer characteristics (SL), hybrid layer (HL), and microtensile bond strength (µTBS) to dentin with two resin cements. The occlusal dentin of 120 third molars was exposed. The teeth were divided into 4 groups (n=30) according to the dentin preparation mode: 1- fine grain diamond bur; 2- coarse grain diamond bur; 3- multi laminate carbide steel bur; and, 4- ultrasonic CV Dentus diamond bur. Each treated dentin group was divided into 2 sub-groups (n=15) according to the resin cement: (1) RelyX U200 and (2) RelyX ARC. Resin composite blocks were cemented on dentin. After storage at 37o C for 24 h, beams with a cross section area of 1.0 mm2 were obtained, and tested in a universal testing machine at a crosshead speed of 0.5 mm/min. Two additional teeth for each sub-group were prepared to analyze the SL and HL on a scanning electron microscopy. According to Kruskal-Wallis test and Dunn tests, there was no significant difference in µTBS among the rotary instruments within each resin cement group. RelyX ARC obtained higher µTBS values compared to RelyX U200 (p<0.05). RelyX ARC formed evident HL, which was not observed for RelyX U200. The dentin mode preparation did not influence the µTBS of the resin cements. The SL was different for all instruments. The cementing agent is more determinant in the hybrid layer formation and bond strength to dentin than the instruments applied on dentin.

The finish line location of the cemented crown is an influencing factor for tensile bond strength, marginal adaption and nanoleakage?

“…The self-adhesive cements comprise acid monomers, such as carboxylic acid and hydroxyethyl methacrylate (HEMA), which create micromechanical retentions through partial etching of the smear layer surface [15]. In addition, there are other monomers, such as phosphate ester, that mediate chemical bonding with the hydroxyapatite, which remains in the dental tissue [6].…”

“…Therefore, the bonding process of these materials is more chemical than mechanical [16]. Due to the effect of partial etching and higher viscosity presented by the self-adhesive cement than conventional cements, it is more difficult to the monomers penetration in the tubules; because the material counts in addition to the chemical adhesion with the dental structure, with a mechanical retention with the TAGs, promoting a greater bond strength [15]. However, a report has indicated that the treatment of the enamel's surface with phosphoric acid at 37% prior to the application of self-adhesive cement increased the strength of adhesion [16].…”

“…The diffuse orientation of the enamel's prisms presents difficulty in terms of etching and penetration of the substrate for the selfadhesive cement monomers [17]. Surface etching with phosphoric acid at 37% improves the topography and changes the superficial tension of the surface; therefore, the cement is attracted by capillarity to the pores of the enamel which facilitates mechanical retention in addition to chemical bonding [15] [14]. Results of the tensile bond strength test in this study corroborate with those of previous studies, indicating that the enamel selective conditioning protocol increases the resistance of the adhesive interface for self-adhesive cement with enamel [15,16].…”

“…In contrast, the complex composition of dentin [inorganic component comprising intertubular dentin [50% of total composition]; organic matrix comprising collagen, phosphorus, and glycosaminoglycans (30%); water (20%) presents an ongoing challenge for the use of self-adhesive cements [6]. The acid monomers of the self-adhesive cement enable etching of the smear layer and produce micro retentions of 2-m size [14,15]. In addition, removal of the partial smear layer is an advantage, due to the presence of a greater amount of hydroxyapatite in the collagen network, which leads to an increased number of bonds between the monomers, and consequently, an increase in the bond strength of the interface [15].…”

Impact of Dentin Conditioning on Shear Bond Strength of Self-Adhesive Resin Cement

“…30,31-33 Therefore, self-adhesive resin cement was selected to be used in this in vitro study, as its bonding mechanism is based on demineralization and infiltration of dentin simultaneously at one time to form a hybrid layer through multifunctional monomers and acid groups included in their chemical composition. [34][35][36][37] The process of tooth preparation and dentin exposure, resulted in formation of dense smear layer. 28 This layer is known as "any remnants, calcified in nature, formed during preparation or instrumentation of hard tooth structures.…”