Ultra-Morphological and Nanomechanical Characterization of Reinforced Enamel and Dentin by Self-Etch Adhesives: The Super Tooth

Abstract

Using various electron microscopy techniques, we have demonstrated that resistance of enamel and dentin to acid attack could be increased in an acid-base resistant zone which was formed following the application of some acidic monomers, especially phosphoric-acid ester methacrylates incorporated into a few self-etching dental adhesives. We proposed that the diffusion of such acidic monomers beyond the classic hybrid layer (interfacial zone) and their ion-exchange interactions with the available hydroxyapatite could result in formation of stable organic-inorganic complexes, and that the structures should be termed “super tooth”, as they would in concept withstand major causes of dental caries and tissue degradation. We also reported that the fluoride-release from these biomaterials could contribute to reinforcement of the underlying tissue. On mechanical testing methodology, we demonstrated that time-dependent nanomechanical response of dental structures in nanoindentation could provide useful information that may not be derived under large-scale fracture experiments such as the common bonding tests. In the present paper, we present some of our recent findings on the ultra-morphological and nanomechanical characteristics of super enamel and super dentin created by self-etching adhesives, compared with sound tissue and the tissue bonded by conventional adhesives following phosphoric-acid treatment or etch-and-rinse adhesives.