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Background: This study evaluated the effect of: (1) chemomechanical caries removal (CMCR); (2) dentine surface treatments and (3) dentine substrates on adhesion of resin-modified glass ionomer cement (RMGIC) adhesives., Methods: One hundred and twenty permanent molars exhibiting moderate cavitation on the occlusal surface into dentine were used. Seventy-five carious molars were used for bond strength testing; the remaining 45 for micromorphological evaluation of the bonded interface. Caries was excavated with NaOCl-based CMCR (Carisolv), enzyme-based CMCR (Papacarie), or conventional rotary caries removal methods. Dentine surface treatment was performed using 37% phosphoric acid, 25-30% PAA or 20% PAA + 3% AlCl3 ., Results: Three-way ANOVA revealed that all three factors 'caries removal methods', 'dentine surface treatments' and 'dentine substrates' did not significantly affect bond strength (p > 0.05). Scanning electron microscopy micrographs showed that the acid-base resistant layer was thicker in caries-affected dentine compared to sound dentine., Conclusions: NaOCl- and enzyme-based CMCR methods have no adverse effect on adhesion of RMGIC adhesives to sound and caries-affected dentine. Dentine surface treatment with 37% phosphoric acid for 5 s has no negative effect on bonding of RMGIC adhesives to dentine compared with using polyacrylic acid for 10 s. RMGIC adhesives bonded well to both sound and caries-affected dentine., (© 2015 Australian Dental Association.)

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]

This article reviews the current concepts for operatively managing carious lesions extending into dentine with minimal removal of tooth structure and restoring with dentine adhesives and direct composite resin. It looks sequentially at the operative steps involved including remineralisation with bioactive cements, bonding to caries-affected dentine including smear-layer modification using HOCl, creation of an acid-base resistance zone,steps to optimise the performance of all-in-one adhesives, and incremental placement of direct composite resin to improve bond strengths to cavity floor dentine. It explores how understanding the phenomenon of colour-shifting at the composite resin-enamel/dentine restoration borders can help in creating near "invisible" restoration margins through a "chameleon" effect. With the increased risks of transmission of Covid-19 when aerosol generating procedures are carried out in Dentistry, following a minimally invasive approach to managing dental caries should be given serious consideration. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the tensile bond durability and ability of four MMA-based adhesive resins to prevent demineralization along the hybrid layer when exposed to a demineralizing solution. Materials and Methods: A PMMA rod was bonded to human dentin using one of four MMA-based adhesive systems: Super-Bond C&B (SB), SBP-40TX (SBP, experimental), M-Bond (MB), and M-Bond II (MB II). Bonded specimens were sectioned into 0.9 mm x 0.9 mm beams and subjected to microtensile bond strength (µTBS) testing after water storage at 37°C for 24 h or 10,000 thermal cycles. Data were analyzed with two-way ANOVA and Bonferroni's t-test. Fracture mode analysis of the bonding interface was performed using a scanning electron microscope (SEM) and statistically analysed using the chi-square test. To disclose the demineralization inhibition potential through formation of an acid-base resistant zone (ABRZ), the bonded interface was exposed to a demineralizing solution (pH 4.5) for 90 min, and then 5% NaOCl for 20 min. After argon-ion etching, the interfacial ultrastructure was observed using an SEM. Results: µTBS values without thermocycling were not significantly different (p > 0.05) among 4 adhesive resins. After thermocycling, a significant decrease in µTBS was found in MB and MB II (p < 0.001), whereas SB and SBP showed no significant change (p > 0.05). Failure modes were signiicantly different (p < 0.05). An ABRZ was seen in SBP, MB, and MB II, while this protective zone was absent in SB. Conclusion: Dentin bonding performance after thermocycling was material dependent in MMA-based adhesive resins. The ABRZ formation was only observed in the self-etching systems. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the morphological changes in the acid-base resistant zone (ABRZ) at the resin/dentin interface after long-term storage in water. Materials and Methods: Two-step self-etching adhesive systems, Clearfil SE Bond (SE) and Clearfil Protect Bond (PB) (Kuraray Medical) were used. Human dentin disk sandwiches with resin composite were prepared, sectioned, and embedded in epoxy resin. The specimens were stored in water for 1 day, 1, 3 or 6 months, and then subjected to demineralizing solution and 5% NaOCl. The specimens were finally sectioned again, polished, argon-ion etched, and observed with SEM. Results: The outer lesion (OL) thickness at 1 day ranged from 10 to 15 µm but increased to approximately 30 urn after 6 months, suggesting gradual loss of dentin stored in water. A lower electron density was noted in the adhesives at the locations that were exposed to water. The ABRZs were observed clearly in all groups; the thickness of the ABRZ at the mid-point of the OL gradually decreased with time for SE. For PB, the thickness was stable up to 1 month, but decreased after 3 months. The bottom of the ABRZ in SE formed a right angle with dentin; in contrast, in PB, it sloped down toward dentin with a broadening bottom. Conclusions: Water storage resulted in changes both in the dentin substrate and the adhesive layer. An ABRZ was observed beneath the hybrid layer after long-term storage in water in both SE and PB. The ABRZ was thicker and relatively more stable in PB, probably due to fluoride release. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to evaluate the effect of Er:YAG laser ablation on the microstructure of the dentin/adhesive interface after acid-base challenge in vitro. Materials and Methods: Thirty-two extracted third molars were used. One pair of disk-shaped specimens was obtained from the midcoronal dentin of each tooth. One surface in each pair was subjected to Er:YAG laser irradiation, while the other was ground using 600-grit SiC abrasive paper. The specimens were assigned to 4 groups with 8 pairs in each group. A self-etching primer (Clearfil SE-Bond), a bonding adhesive (Clearfil SE-Bond), and a photocuring composite (Clearfil APX) were applied according to manufacturer's instructions to create dentin-resin "sandwiches" of each pair, except in group IV, where no primer was applied. The specimens were stored in demineralizing solution for 20 min in groups I and IV, 60 min in group II, and 120 min in group III. After immersion in 5% NaOCl, all the specimens were polished and argon-ion etched. Finally, the interfaces between the dentin and bonding agent were observed under a scanning electron microscope. Results: All specimens in groups I to III showed an acid-base resistant zone, except those of group IV, which debonded completely. A statistically significant difference was found in the thickness of the acid-base resistant zone between group I vs groups II and III for both abraded and Er:YAG-irradiated surfaces. There was no statistically significant difference in the thickness of the acid-base resistant zone between groups II and III for both conventionally prepared and Er:YAG-irradiated surfaces. Conclusion: The existence of an acid-base resistant zone following the application of the SE Bond system on both abraded and Er:YAG-lased human dentin, regardless of the acid-base challenge duration, was confirmed. [ABSTRACT FROM AUTHOR]

Abstract: Objective: Characterize the ultramorphology and secondary caries inhibition potential of different dentin adhesive systems in order to find a satisfactory explanation resist to recurrent caries. Methods: Human premolar dentin was treated with one of the two self-etching adhesive systems, Clearfil SE Bond, Clearfil Protect Bond or an acid-etching adhesive system, Single Bond. The bonded interface was exposed to an artificial demineralizing solution (pH 4.5) for 90min and then 5% sodium hypochlorite for 20min. Transmission electron microscopic observation was performed at the adhesive–dentin interface. The width of the reinforced zone was measured and data were analyzed with univariate analysis of variance under general linear model. In order to identify type of crystallites in the reinforced zone selected area electron diffraction was performed. Results: An acid–base resistant zone (ABRZ) was found adjacent to the hybrid layer in the outer lesion front with only Clearfil SE Bond and Clearfil Protect Bond, while Single Bond was devoid of this protective zone. Crystallite arrangement and the ultramorphology were almost similar in the corresponding regions of Clearfil SE Bond and Clearfil Protect Bond. However, thickness of the ABRZ at the mid portion was 1159(±41.91)nm in Clearfil protect Bond, which was significantly thicker than that of Clearfil SE Bond (F =514.84, p <0.001). Selected area electron diffraction confirmed the crystallites in the zone as apatite. Conclusions: The self-etching adhesive systems created a new reinforced acid resistant dentin under the hybrid layer. Difference in the thickness of the zone expressed a different potential for demineralization inhibition. [Copyright &y& Elsevier]