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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]

Purpose: To investigate the effect of different etching products used prior to the application of universal self-etching adhesive on dentin bonding. Materials and Methods: The etching products Multi Etchant (ME), Enamel Conditioner (EC), and K-etchant GEL (KE) were used as pre-treatments prior to the application of the one-bottle self-etching adhesive Adhese Universal (AU). Ground human dentin surfaces were randomly divided into four treatment groups: 1. control (CT; AU without conditioner); 2. ME; 3. EC; 4. KE. Microtensile bond strength (μTBS) tests with a thermocycling challenge (0-TC or 10,000-TC) were carried out and the morphological attributes of the adhesive-dentin interface were observed after an acid-base challenge using SEM to observe the acid-base resistant zone (ABRZ). Results: The KE group had a statistically significantly lower μTBS than did the ME and EC groups at 0-TC, and than the CT, ME, and EC groups at 10,000-TC (p < 0.05). An ABRZ was observed in all groups but had partially disappeared in KE. A funnel-shaped area of erosion was also observed at the junction of the dentin and bonding layer in the CT, ME, and EC groups, while the hybrid layer was thicker in the KE group with no evidence of erosion. Conclusion: The application of ME or EC did not reduce the microtensile bond strength and resulted in ABRZ formation, while the ABRZ was partially reduced in the KE group. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the roles of MDP and NaF in the bonding resin of a two-step self-etch adhesive (2-SEA) on enamel bonding performance. Materials and Methods: The experimental 2-SEAs were composed of an MDP-containing self-etching primer and four different bonding resins which were MDP- and NaF-free (00), MDP-containing and NaF-free (M0), MDP-free and NaF-containing (0F), and MDP- and NaF-containing (MF) adhesives. Microshear bond strength (μSBS) to enamel and ultimate tensile strength (UTS) of the adhesive resin were determined. The morphological characteristics of the adhesive- enamel interface after acid-base challenge were observed using SEM to evaluate the acid-base resistant zone (ABRZ). Results: No decrease in μSBS was observed even after thermocycling (TC) in 00, 0F and MF. However, the μSBS of M0 significantly decreased after TC. The UTS of M0 significantly decreased after 1- and 180-day storage in water. SEM observations indicated that ABRZ was present in all groups. However, formation of erosion beneath the ABRZ was observed in M0 and 00, whereas formation of a slope without erosion was observed at the bottom of the ABRZ in MF. Conclusion: In the experimental 2-SEAs, the addition of MDP alone to the adhesive resin did not contribute to an improvement in enamel bonding durability and interfacial morphology, whereas the addition of NaF in the adhesive resin demonstrated an enhancement of the bonding durability and improvement of acid resistance at the bonded interface. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the effect of selective phosphoric acid etching on enamel using “no-wait” self-etching adhesives. Materials and Methods: Clearfil Universal Bond Quick (UBQ, Kuraray Noritake) or G-Premio BOND (GPB, GC) was applied to ground human enamel surfaces. The adhesives were used in 3 modes: no-waiting self-etching mode (UBQ-0 or GPB-0), 10-s self-etching mode (UBQ-10 or GPB-10), and the selective-etch mode with phosphoric acid etching (UBQ-PA or GPB-PA). After an acid-base challenge, the morphological attributes of the interface were examined using scanning electron microscopy (SEM) to characterize the acid-base resistant zone (ABRZ). Microshear bond strength (μSBS) testing to enamel and ultimate tensile strength (UTS) of the adhesive resin were carried out. Results: ABRZ formation was confirmed in all groups. UBQ-PA and GPB-PA created thicker ABRZ with no funnelshaped erosion beneath the adhesive-enamel interface. μSBS of UBQ-PA was significantly higher than UBQ-0 and UBQ-10 (p < 0.05). However, there were no statistically signficant differences in μSBS among GPB-0, GPB-10, and GPB-PA. For the UTS, UBQ was significantly higher than GPB. Conclusion: Selective phosphoric acid etching created a stable adhesive-enamel interface. The no-waiting self-etching concept adhesive led to a thinner ABRZ. The results of μSBS suggest that phosphoric acid etching effects on enamel are material dependent. [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.

Purpose: To evaluate the acid-base resistant zone (ABRZ) at the adhesive/enamel interface of self-etching adhesives with or without prior phosphoric acid etching. Materials and Methods: Four adhesives were used in 8 groups: Clearfil SE Bond (SEB), Optibond XTR (XTR), Scotchbond Universal Adhesive (SBU), and Clearfil BOND SE ONE (ONE) without prior phosphoric-acid etching, and each adhesive with phosphoric acid etching for 10 s (P-SEB, P-XTR, P-SBU and P-ONE, respectively). After application of self-etching adhesives on ground enamel surfaces of human teeth, a flowable composite was placed. For observation of the acid-base resistant zone (ABRZ), the bonded interface was exposed to demineralizing solution (pH 4.5) for 4.5 h, followed by 5% NaOCl with ultrasonication for 20 min. After the acid-base challenge, morphological attributes of the interface were observed using SEM. Results: ABRZ formation was confirmed in all groups. The funnel-shaped erosion beneath the interface was present in SBU and ONE, where nearly 10 to 15 μm of enamel was dissolved. With phosphoric acid etching, the ABRZs were obviously thicker compared with no phosphoric acid etching. Conclusion: Enamel beneath the bonding interface was more susceptible to acid dissolution in SBU and ONE. In the case of the one-bottle self-etching adhesives and universal adhesives that intrinsically have higher pH values, enamel etching should be recommended to improve the interfacial quality. [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]

Self-etch adhesive (SEA) systems simplify bonding procedures. It is believed that good mechanical retention and chemical bonding are both important factors to obtain reliable bonding to enamel. The enamel acid-base resistant zone (ABRZ) has been confirmed at the adhesive/enamel interface by scanning electron microscopic observation. However, the formation of enamel ABRZ is influenced by the type and components of adhesive systems. Chemical interactions by a functional monomer with hydroxyapatite strongly support the explanation of the mechanism for enamel ABRZ formation. The ABRZ created by MDP-containing SEA systems has shown good potential to resist acid attack from simulated recurrent caries models. In addition, fluoride release may enhance acid resistance. It has been proposed that such a reinforced enamel be termed "Super Enamel". The concept of the formation of super enamel may contribute to protecting enamel, and conserve tooth structure leading to improved restoration longevity. [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: To evaluate the microtensile bond strength (µTBS) and acid-base resistant zone (ABRZ) of two dual-curing core systems to dentin using four curing modes. Materials and Methods: Sixty-four caries-free human molars were randomly divided into two groups according to two dual-curing resin core systems: (1) Clearfil DC Core Automix; (2) Estelite Core Quick. For each core system, four different curing modes were applied to the adhesive and core resin: (1) dual-cured and dual-cured (DD); (2) chemically cured and dual-cured (CD); (3) dual-cured and chemically cured (DC); (4) chemically cured and chemically cured (CC). The specimens were sectioned into sticks (n = 20 for each group) for the microtensile bond test. µTBS data were analyzed using two-way ANOVA and the Dunnett T3 test. Failure patterns were examined with scanning electron microscopy (SEM) to determine the proportion of each mode. Dentin sandwiches were produced and subjected to an acid-base challenge. After argon-ion etching, the ultrastructure of ABRZ was observed using SEM. Results: For Clearfil DC Core Automix, the µTBS values in MPa were as follows: DD: 29.1 ± 5.4, CD: 21.6 ± 5.6, DC: 17.9 ± 2.8, CC: 11.5 ± 3.2. For Estelite Core Quick, they were: DD: 48.9 ±5.7, CD: 20.5 ± 4.7, DC: 41.4 ± 8.3, CC: 19.1 ± 6.0. The bond strength was affected by both material and curing mode, and the interaction of the two factors was significant (p < 0.001). Within both systems, there were significant differences among groups, and the DD group showed the highest µTBS (p < 0.05). ABRZ morphology was not affected by curing mode, but it was highly adhesive-material dependent. Conclusion: The curing mode of dual-curing core systems affects bond strength to dentin, but has no significant effect on the formation of ABRZ. [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]

• The cement systems used influenced the morphology of acid–base resistance zone. • The self-etch adhesives combined with the cement systems affected the bond strength. • The tested cement systems differed in resistance to hydrothermal stress. Bond durability and resistance to acid-base challenge of dentin with dual-cure resin cement have been rarely investigated. The purpose of this study was to evaluate dentin bond strength and observe the adhesive-dentin interface after acid-base challenge using three different dual-cure resin cements. Thirty dentin surfaces from caries-free human premolars were ground and bonded with one of three dual-cure resin cements: PANAVIA V5 (V5), ESTECEM II (E II) and Rely X Ultimate (RXU) and thermocycled for 0, 5,000 and 10,000 cycles. A microtensile bond strength (μ TBS) test was undertaken and the interface of the bonded specimens after acid-base challenge was examined by SEM. The μTBS of V5 exhibited a stable bond strength despite thermal cycling while the bond of EII and RXU after 10,000 cycles dropped significantly among all thermal cycle periods (p <0.05). An acid-base resistant zone (ABRZ) was observed in all groups, however, the morphology of the bonded interface differed among the tested cements. Bonding durability to dentin and ABRZ morphologies differed among the cements evaluated. PANAVIA V5 cement system with tooth primer provided the most reliable bond strength and was best able to resist the acid–base challenge. [ABSTRACT FROM AUTHOR]

The resin-coating technique is one of the successful bonding techniques used for the indirect restorations. The dentin surfaces exposed after cavity preparation are coated with a thin film of a coating material or a dentin bonding system combined with a flowable composite resin. Resin coating can minimize pulp irritation and improve the bond strength between a resin cement and tooth structures. The technique can also be applied to endodontically treated teeth, resulting in prevention of coronal leakage of the restorations. Application of a resin coating to root surface provides the additional benefit of preventing root caries in elderly patients. Therefore, the coating materials have the potential to reinforce sound tooth ("Super Tooth" formation), leading to preservation of maximum tooth structures. [ABSTRACT FROM AUTHOR]

Dentin bonding systems have been dramatically simplified and improved during the recent decades. Monomer penetration into dentin and its polymerization in situ creates a hybrid layer, which is essential to obtain good bonding to dentin. Moreover, the presence of an acid–base resistant zone below the hybrid layer has been documented with self-etching adhesive systems in an artificial secondary caries attack. When ultrastructure of the acid–base resistant zone is assessed by SEM and TEM observations, formation of the acid–base resistant zone is considered to be due to the monomer penetration potential and fluoride release in the adhesive systems. Natural dentin has a limited potential to resist an acid attack of secondary caries; however, the acid–base resistant zone does not purely consist of dentin in morphology, it is rather a combination of dentin and the adjacent hybrid layer. Therefore, the reinforced dentin has been called “Super Dentin” bearing the ability to prevent primary and secondary caries. Prospectively, the great potential of adhesive technology in creation of the “Super Dentin” would lead to the development of new materials for mechanical, chemical and biological protection of the dental structures.

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. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effect of fluoride concentration in adhesives on morphology of acid-base resistant zone (ABRZ). Seven experimental adhesives with different concentrations of NaF (0 wt%; FO to 100 wt%: F100) were prepared based on the formulation of a commercially available adhesive (Clearfil Protect Bond, F100). The resin-dentin interface of the bonded specimen was subjected to deminerahzing solution and NaOCl, sectioned, polished and argon-ion etched for SEM observation. Fluoride release from each adhesive was measured using an ion-selective electrode. Fluoride ion release from the adhesive linearly increased with higher NaF concentration. The ABRZ area increased significantly with higher NaF concentration except for F0, F10, and F20 (p<0.05). F100 showed the largest ABRZ, where a slope of acid-resistant dentin was clearly observed at the bottom of the ABRZ. The concentration of NaF in the two-step self-etching adhesive resin influenced the amount of dentin structure remaining after acid-challenge. [ABSTRACT FROM AUTHOR]

This study investigated the influence of the composition of self-etching primer adhesive systems on the morphology of acid-base resistant zones (ABRZs). One-step self-etching primer systems (Clearfil Tri-S Bond, G-Bond, and One-Up Bond F Plus) and two-step self-etching primer systems (Clearfil SE Bond, Clearfil Protect Bond, UniFil Bond, and Mac Bond II) were used in this study. Each adhesive was applied on prepared dentin disk surfaces, and a resin composite was placed between two dentin disks. All resin-bonded specimens were subjected to acid-base challenge. Observation under a scanning electron microscope (SEM) revealed the creation of an ABRZ adjacent to the hybrid layer for all the self-etch primer adhesive systems, even when non-fluoride releasing adhesives were used. The presence of fluoride in two-step self-etching adhesive significantly increased the thickness of ABRZ created. Results suggested that an ABRZ was created with the use of self-etching primer adhesive systems, but its morphology differed between one-and two-step self-etching primer adhesive systems and was influenced by fluoride release activity. [ABSTRACT FROM AUTHOR]

This study aimed at evaluating the effect of functional monomers in all-in-one adhesive systems on formation of acid-base resistant zone (ABRZ) in enamel and dentin. Experimental adhesive systems containing one of three functional monomers; MDP, 3D-SR and 4-META were applied to enamel or dentin surface and light-cured. A universal resin composite was then placed. The specimens were subjected to a demineralizing solution (pH 4.5) and 5% NaC1O for acid-base challenge and then observed by SEM. The ABRZ was clearly observed in both enamel and dentin interfaces. However, enamel ABRZ was thinner than dentin ABRZ in all adhesives. Morphology of the ABRZ was different between enamel and dentin, and also among the adhesives. Funnel-shaped erosion was observed only in the enamel specimen with the 4-META adhesive. The formation of enamel/dentin ABRZ was confirmed in all adhesives, but the morphology was influenced by the functional monomers. [ABSTRACT FROM AUTHOR]

Summary: Dentin bonding systems have been dramatically simplified and improved during the recent decades. Monomer penetration into dentin and its polymerization in situ creates a hybrid layer, which is essential to obtain good bonding to dentin. Moreover, the presence of an acid–base resistant zone below the hybrid layer has been documented with self-etching adhesive systems in an artificial secondary caries attack. When ultrastructure of the acid–base resistant zone is assessed by SEM and TEM observations, formation of the acid–base resistant zone is considered to be due to the monomer penetration potential and fluoride release in the adhesive systems. Natural dentin has a limited potential to resist an acid attack of secondary caries; however, the acid–base resistant zone does not purely consist of dentin in morphology, it is rather a combination of dentin and the adjacent hybrid layer. Therefore, the reinforced dentin has been called “Super Dentin” bearing the ability to prevent primary and secondary caries. Prospectively, the great potential of adhesive technology in creation of the “Super Dentin” would lead to the development of new materials for mechanical, chemical and biological protection of the dental structures. [ABSTRACT FROM AUTHOR]

The aim of this study was to analyze the ultrastructure of the dentin-adhesive interface using two all-in-one adhesive systems (Clearfil Tri-S Bond, TB; Tokuyama Bond Force, BF) after different acid-base challenges. Three solutions were used as acidic solutions for the acid-base challenges: a demineralizing solution (DS), a phosphoric acid solution (PA), and a hydrochloric acid solution (HCl). After the acid-base challenges, the bonded interfaces were examined by scanning electron microscopy. Thickness of the acid- base resistant zone (ABRZ) created in PA and HCl was thinner than in DS for both adhesive systems. For BF adhesive, an eroded area was observed beneath the ABRZ after immersion in PA and HCl, but not in DS. Conversely for TB adhesive, the eroded area was observed only after immersion in PA. In conclusion, although the ABRZ was observed for both all-in-one adhesive systems, its morphological features were influenced by the ingredients of both the adhesive material and acidic solution. [ABSTRACT FROM AUTHOR]

Abstract: Objectives: To investigate the effects of two functional monomers on caries-inhibition potential and bond strength of two-step self-etching adhesive systems to enamel. Methods: Clearfil SE Bond and similar experimental formulations different in the functional monomer were used. Four combinations of primer and bonding agents were evaluated: (1) Clearfil SE Bond which contains MDP in both primer and bonding (M–M); (2) Clearfil SE Bond primer and Phenyl-P in bonding (M–P); (3) Phenyl-P in primer and Clearfil SE Bond bonding (P–M); (4) Phenyl-P in primer and bonding (P–P). Ground buccal enamel surfaces of human sound premolars were treated with one of the systems and the bonded interface was exposed to an artificial demineralising solution (pH 4.5) for 4.5h, and then 5% NaOCl with ultrasonication for 30min. After argon-ion etching, the interfacial ultrastructure was observed using SEM. Micro-shear bond strength to enamel was measured for all groups and results were analysed using one-way ANOVA and Turkey''s HSD, while failure modes were analysed by chi-square test. Results: An acid–base resistant zone (ABRZ) was found with all adhesive systems containing MDP either in primer or bond; however, ultramorphology and crystallite arrangement in the ABRZ were different among groups. P–P was the only group devoid of this protective zone. Micro-shear bond strength in M–M was significantly higher than those in M–P, P–M and P–P, while the latter three were not different from each other. Failure modes were significantly different (p <0.05). Conclusions: Functional monomers in two-step self-etching systems influence both the bonding performance and the formation of ABRZ on enamel. [Copyright &y& Elsevier]

An acid-base resistant zone has been found to exist after acid-base challenge adjacent to the hybrid layer using SEM. The aim of this study was to examine the acid-base resistant zone using three different bonding systems. Dentin disks were applied with three different bonding systems, and then a resin composite was light-cured to make dentin disk sandwiches. After acid-base challenge, the polished surfaces were observed using SEM. For both one- and two-step self-etching primer systems, an acid-base resistant zone was clearly observed adjacent to the hybrid layer - but with differing appearances. For the wet bonding system, the presence of an acid-base resistant zone was unclear. This was because the self-etching primer systems etched the dentin surface mildly, such that the remaining mineral phase of dentin and the bonding agent yielded clear acid-base resistant zones. In conclusion, the acid-base resistant zone was clearly observed when self-etching primer systems were used, but not so for the wet bonding system. [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]

The purpose of this study was to evaluate dentin bond strengths and to observe the adhesive-dentin interface after acid-base challenge using fluoride-free and fluoride-releasing self-etching adhesive systems; Clearfil SE Bond (SE), FL-Bond (FL) and FL-Bond II(FL II). Fifteen dentin surfaces from human molars were ground and bonded with one of three adhesive systems. The microtensile bond strength (pTBS) test was performed at a crosshead speed of 1 mm/mm. The interface of the bonded specimens after acid-base challenge were also examined by a SEM. The pTBS of SE were significantly higher than those of FL and FL II (p<0.05), however, there were no significant differences between FL and FL II (p>0.05). An acid-base resistant zone (ABRZ) was observed in all the groups, however, formation of the ABRZ was material dependent. Fluoride-release from the adhesive is a key factor to create thick ABRZ. [ABSTRACT FROM AUTHOR]

An acid–base resistant zone (ABRZ) has been shown to be created under a hybrid layer in a self-etching adhesive system at the adhesive/dentin interface. The purpose of this study was to assess the nanostructure of the ABRZ by applying all-in-one adhesive systems. Human premolar dentin was treated with one of two all-in-one adhesive systems; Clearfil Tri-S Bond and G-Bond according to the manufacturers' instructions. After placement of a resin composite, the bonded interface was vertically sectioned and subjected to an acid-base challenge. Following this, the nanostructure of the ABRZ was examined by SEM and TEM. The SEM observations of the adhesive-dentin interface after the acid-base challenge indicated that a hybrid layer less than 1 μm thick was created, and a ABRZ was formed beneath the hybrid layer for each adhesive system. The TEM observations indicated that the ABRZ contained mineral components in both adhesive systems, however, the thickness of the ABRZ was material dependent. The application of the all-in-one adhesive systems created an ABRZ at the underlying dentin, which reinforced normal dentin against dental caries. Therefore, this zone was named ‘Super Dentin’. Formation of ‘Super Dentin’ is a new approach in caries prevention. [ABSTRACT FROM AUTHOR]

The purposes of this study were twofold, namely to evaluate: (1) the effect of hybridization on microtensile bond strength (μTBS) to dentin, and (2) the ultrastructure of the dentin-adhesive interface with 4-META/MMA-TBB resin after acid-base challenge. Dentin surfaces, which received no treatment (NT), 65% phosphoric acid (PA), or 10% citric acid-3% ferric chloride (10-3), were bonded with a 4-META/MMA-TBB resin. To evaluate dentin bond strength, μTBS test was performed at a crosshead speed of 1 mm/mm. For ultrastructural evaluation of the adhesive interfaces, SEM was used to examine the interfaces of the bonded specimens after acid-base challenge. The μTBS of NT was not determined, while that of 10-3 was significantly higher than that of PA (p<0.05). With PA and 10-3, the hybrid layer was clearly observed, but no so for the acid-base resistant zone. Wall lesion was found in NT only. In conclusion, hybridization is vital to improving μTBS to dentin and enhancing resistance at the adhesive interface against acid-base challenge. [ABSTRACT FROM AUTHOR]

Objectives: Nowadays, the universal adhesives are often used for silane application prior to application of self-adhesive resin cements. The purpose of this study was to evaluate enamel surface roughness and to observe the enamel-adhesive interface after acid-base challenge using three different self-adhesive resin cements combined with universal adhesives., Materials and Methods: Three self-adhesive resin cements: PANAVIA SA Luting Cement Plus (SA), Calibra Universal (CA) and MaxCem Elite Chroma (MC) which in conjunction with the particular universal adhesives: Clearfil Universal Bond Quick (UQ), Prime&Bond Universal (PB) and Optibond Universal (OB) were tested. Thirty enamel surfaces from caries-free human premolars were ground and bonded with the tested self-adhesive resin cements combined with universal adhesives. The surface roughness test (Sa) with or without applying adhesives was performed with 3D-CLSM. The interface of the bonded specimens after acid-base challenge was also examined by SEM., Results: The Sa of OB was significantly higher than those of PB and UQ. There were statistically significant differences among all of the groups (p < 0.05). An acid-base resistant zone (ABRZ) was observed in all groups, however, formation of the ABRZ was material dependent., Conclusion: OB provided most etching performance to enamel of human premolars and MC group with OB presented durability against acid-base challenge., Clinical Significance: Nowadays, the combination of self-adhesive resin cement and universal adhesive may be a viable option for a reliable bonding performance and bonding durability in indirect restorative dentistry., (Copyright © 2020. Published by Elsevier Ltd.)

Self-etch adhesive (SEA) systems simplify bonding procedures. It is believed that good mechanical retention and chemical bonding are both important factors to obtain reliable bonding to enamel. The enamel acid-base resistant zone (ABRZ) has been confirmed at the adhesive/enamel interface by scanning electron microscopic observation. However, the formation of enamel ABRZ is influenced by the type and components of adhesive systems. Chemical interactions by a functional monomer with hydroxyapatite strongly support the explanation of the mechanism for enamel ABRZ formation. The ABRZ created by MDP-containing SEA systems has shown good potential to resist acid attack from simulated recurrent caries models. In addition, fluoride release may enhance acid resistance. It has been proposed that such a reinforced enamel be termed "Super Enamel". The concept of the formation of super enamel may contribute to protecting enamel, and conserve tooth structure leading to improved restoration longevity.

Purpose: To investigate the effect of different etching products used prior to the application of universal self-etching adhesive on dentin bonding., Materials and Methods: The etching products Multi Etchant (ME), Enamel Conditioner (EC), and K-etchant GEL (KE) were used as pre-treatments prior to the application of the one-bottle self-etching adhesive Adhese Universal (AU). Ground human dentin surfaces were randomly divided into four treatment groups: 1. control (CT; AU without con-ditioner); 2. ME; 3. EC; 4. KE. Microtensile bond strength (µTBS) tests with a thermocycling challenge (0-TC or 10,000-TC) were carried out and the morphological attributes of the adhesive-dentin interface were observed after an acid-base challenge using SEM to observe the acid-base resistant zone (ABRZ)., Results: The KE group had a statistically significantly lower µTBS than did the ME and EC groups at 0-TC, and than the CT, ME, and EC groups at 10,000-TC (p < 0.05). An ABRZ was observed in all groups but had partially disappeared in KE. A funnel-shaped area of erosion was also observed at the junction of the dentin and bonding layer in the CT, ME, and EC groups, while the hybrid layer was thicker in the KE group with no evidence of erosion., Conclusion: The application of ME or EC did not reduce the microtensile bond strength and resulted in ABRZ formation, while the ABRZ was partially reduced in the KE group.

The resin-coating technique is one of the successful bonding techniques used for the indirect restorations. The dentin surfaces exposed after cavity preparation are coated with a thin film of a coating material or a dentin bonding system combined with a flowable composite resin. Resin coating can minimize pulp irritation and improve the bond strength between a resin cement and tooth structures. The technique can also be applied to endodontically treated teeth, resulting in prevention of coronal leakage of the restorations. Application of a resin coating to root surface provides the additional benefit of preventing root caries in elderly patients. Therefore, the coating materials have the potential to reinforce sound tooth ("Super Tooth" formation), leading to preservation of maximum tooth structures.

Purpose: To evaluate the effect of selective phosphoric acid etching on enamel using "no-wait" self-etching adhesives., Materials and Methods: Clearfil Universal Bond Quick (UBQ, Kuraray Noritake) or G-Premio BOND (GPB, GC) was applied to ground human enamel surfaces. The adhesives were used in 3 modes: no-waiting self-etching mode (UBQ-0 or GPB-0), 10-s self-etching mode (UBQ-10 or GPB-10), and the selective-etch mode with phosphoric acid etching (UBQ-PA or GPB-PA). After an acid-base challenge, the morphological attributes of the interface were examined using scanning electron microscopy (SEM) to characterize the acid-base resistant zone (ABRZ). Microshear bond strength (µSBS) testing to enamel and ultimate tensile strength (UTS) of the adhesive resin were carried out., Results: ABRZ formation was confirmed in all groups. UBQ-PA and GPB-PA created thicker ABRZ with no funnel-shaped erosion beneath the adhesive-enamel interface. µSBS of UBQ-PA was significantly higher than UBQ-0 and UBQ-10 (p < 0.05). However, there were no statistically signficant differences in µSBS among GPB-0, GPB-10, and GPB-PA. For the UTS, UBQ was significantly higher than GPB., Conclusion: Selective phosphoric acid etching created a stable adhesive-enamel interface. The no-waiting self-etching concept adhesive led to a thinner ABRZ. The results of µSBS suggest that phosphoric acid etching effects on enamel are material dependent.

Purpose: To evaluate the roles of MDP and NaF in the bonding resin of a two-step self-etch adhesive (2-SEA) on enamel bonding performance., Materials and Methods: The experimental 2-SEAs were composed of an MDP-containing self-etching primer and four different bonding resins which were MDP- and NaF-free (00), MDP-containing and NaF-free (M0), MDP-free and NaF-containing (0F), and MDP- and NaF-containing (MF) adhesives. Microshear bond strength (µSBS) to enamel and ultimate tensile strength (UTS) of the adhesive resin were determined. The morphological characteristics of the adhesive-enamel interface after acid-base challenge were observed using SEM to evaluate the acid-base resistant zone (ABRZ)., Results: No decrease in μSBS was observed even after thermocycling (TC) in 00, 0F and MF. However, the μSBS of M0 significantly decreased after TC. The UTS of M0 significantly decreased after 1- and 180-day storage in water. SEM observations indicated that ABRZ was present in all groups. However, formation of erosion beneath the ABRZ was observed in M0 and 00, whereas formation of a slope without erosion was observed at the bottom of the ABRZ in MF., Conclusion: In the experimental 2-SEAs, the addition of MDP alone to the adhesive resin did not contribute to an improvement in enamel bonding durability and interfacial morphology, whereas the addition of NaF in the adhesive resin demonstrated an enhancement of the bonding durability and improvement of acid resistance at the bonded interface.

The aim of interfacial nanoleakage evaluation is to gain a better understanding of degradation of the adhesive-dentin interface. The acid-base resistant zone (ABRZ) is recognized at the bonded interface under the hybrid layer (HL) in self-etch adhesive systems after an acid-base challenge. The purpose of this study was to evaluate nanoleakage in HL and ABRZ using three self-etch adhesives; Clearfil SE Bond (SEB), Clearfil SE One (SEO), and G-Bond Plus (GBP). One of the three adhesives was applied on the ground dentin surface and light cured. The specimens were longitudinally divided into two halves. One half remained as the control group. The others were immersed in ammoniacal silver nitrate solution, followed by photo developing solution under fluorescent light. Following this, the specimens were subjected to acid-base challenges with an artificial demineralization solution (pH4.5) and sodium hypochlorite, and prepared in accordance with common procedures for transmission electron microscopy (TEM) examination. The TEM images revealed silver depositions in HL and ABRZ due to nanoleakage in all the adhesives; however, the extent of nanoleakage was material dependent. Funnel-shaped erosion beneath the ABRZ was observed only in the all-in-one adhesive systems; SEO and GBP, but not in the two-step self-etch adhesive system; SEB.