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The conventional three-step adhesive system is composed of an etchant, a primer, and a bonding resin. Japanese manufacturers focused on simplifying the etching and priming procedures, resulting in a one-step process referred to as "self-etching". Currently, a universal adhesive system and a universal-shade composite are trending. Morphological changes at the interface of the bonded specimens following an artificial acid-base challenge have been observed under SEM and TEM. A new layer is created beneath the hybrid layer, which is referred to as the "acid-base resistant zone (ABRZ)". With the increasing number of older adults and better teeth retention in the elderly population, the prevention and treatment of root caries are becoming increasingly important. 38% silver diamine fluoride (SDF, Saforide) contains high concentrations of silver and fluoride ions, which is very effective in preventing the progression of root dentin caries. However, the discoloration of the tooth structure is a drawback. It was reported that light exposure and demineralization of dentin accelerated its discoloration. From the evaluation of S. mutans biofilm accumulation on dentin surfaces, application of 38% SDF was the most effective to decrease the amount of biofilm attached to the dentin surface. In addition, 38% SDF has the potential to be used as a root caries indicator. From the clinical assessment, the SDF induced discoloration of the root caries lesions and provided an anti-inflammatory effect on the gingiva around the teeth affected by root caries. [ABSTRACT FROM AUTHOR]

Purpose: A new two-step self-etch adhesive (2-SEA) free of hydrophilic monomers was evaluated. Its microtensile bond strength (µTBS) to dentin under various aging conditions, interfacial gap formation, water sorption/solubility, and formation of an acid-base resistant zone (ABRZ) were evaluated and compared with a gold-standard 2-SEA. Materials and Methods: The new 2-SEA G2-Bond Universal (G2; GC) was compared to Clearfil SE Bond 2 (CSE2, Kuraray Noritake). Their µTBS to sound coronal dentin was tested after 1 week, 10,000 thermal cycles (TC), 20,000 TC, 6 months and 1 year. Failure mode was determined using scanning electron microscopy (SEM). Gap formation at the interface of 2-mm deep tapered cavities with an enamel border was observed using swept-source optical coherence tomography after 1 day, 1 week, 10,000 TC, and 20,000 TC. In addition, water sorption and solubility of the bonding agents was measured, and ABRZ formation was evaluated using SEM. Results: There was no significant difference in µTBS between G2 and CSE2 (p > 0.05), and the aging conditions had no significant effect on µTBS (p > 0.05). In all groups, cohesive failures prevailed (55%-95%). Interfacial gap formation was initially similar for both adhesives (p > 0.05), but G2 exhibited a significantly lower gap formation than CSE2 after TC (p < 0.05). The water sorption of G2 was significantly lower compared to CSE2 (p < 0.05), and their solubility was statistically similar (p > 0.05). ABRZ of similar thickness was observed with both adhesives. Conclusion: The new 2-SEA exhibited stable dentin bonding and increased hydrophobicity resulting from the absence of hydrophilic monomers. [ABSTRACT FROM AUTHOR]