Correlative Transmission Electron Microscopy Examination of Nondemineralized and Demineralized Resin-Dentin Interfaces Formed by Two Dentin Adhesive Systems

Abstract

The resin-dentin interface formed by two dentin adhesives, Optibond (OPTI, Kerr) and Scotchbond Multi-Purpose (SBMP, 3M), was ultramorphologically examined by transmission electron microscopy (TEM). Ultrastructural information from nondemineralized and demineralized sections was correlated. It was hypothesized that the different chemical formulations of the two adhesives would result in a different morphological appearance of the hybrid layer. Ultrastructural TEM examination proved that each of the two dentin adhesive systems was able to establish a micromechanical bond between dentin and resin with the formation of a hybrid layer. However, the interfacial hybridization process that took place to produce this resin-dentin bond appeared to be specifically related to the chemical composition and application modes of both systems. OPTI consistently presented with a hybrid layer with a relatively uniform ultrastructure, electron density, and acid resistance. These three parameters were found to be more variable for the hybrid layer formed by SBMP. Characteristic of SBMP was the identification of an amorphous phase deposited at the outer surface of the hybrid layer. Although both adhesive systems investigated follow a total-etch concept, their specific chemical formulations result in different interfacial ultrastructures that are probably related to different underlying bonding mechanisms. The clinical significance of these morphological findings, however, is still unknown.

Microleakage and interfacial morphology of self‐etching adhesives in class V resin composite restorations

“…It should be taken into account that the clinical significance of the high microleakage scores obtained with the use of polyalkenoic acid-based adhesives (e.g., SBMP) is controversial; 25 their clinical retention rate at 3 years is unexpectedly high, which may be related to theirs stressrelaxation capacity. 25,30 On gingival margins, none of the restorative systems under study completely resisted microleakage, consistent with the findings of other studies. 4,31 CSEB showed lower dye penetration values compared with E&P, as reported by other authors.…”

Effect of Curing Mode on Microtensile Bond Strength to Dentin of Two Dual-cured Adhesive Systems in Combination with Resin Luting Cements for Indirect Restorations

“…The possible explanation for this finding may be related to the mixture among the primer and adhesive resin components within the hybrid layer when Pre-Bond is applied to the primed surface. Composed of a high concentration of hydrophobic monomers, such as Bis-GMA (Table 1), Pre-Bond adhesive resin may create a hybrid layer with a high concentration of hydrophobic monomers and, consequently, lower hydrophilicity, [14][15][16] thus improving its mechanical properties. [17][18] Moreover, dual-curing mechanisms within the hybrid layer may have contributed to the higher µTBS when Pre-Bond resin infiltrated the primed dentin surface.…”

SEM evaluation of resin-carious dentin interfaces formed by two dentin adhesive systems

“…This high variance indicated the unpredictability of the demineralization process in carious lesions. Van Meerbeek et al [11] demonstrated that, in some dentin bonding systems, there was a discrepancy between the depth of dentin demineralization and the depth of resin infiltration. In our investigation, this discrepancy was more obvious in the pink zone bonded with the etch-rinse system.…”

“…A bond between adhesive resin and dentin depends on the penetration of the primer and adhesive resin into the conditioned dentin surface to create micromechanical interlocking between the dentin collagen and resin, forming a hybrid layer [10]. The formation of the hybrid layer may be affected by chemical composition and application mode of adhesive systems [11], differences in the dentin location [12,13] and changes in the microstructural features of dentin associated with the caries process [14]. Several previous studies have shown that the hybrid layer created by etch-rinse systems is significantly thicker than that created by self-etch primers [14][15][16] since they are more acidic and therefore result in a deeper demineralized layer.…”