The Journal of Adhesive Dentistry, 06/2021

Purpose: To compare the clinical performance and treatment times between glass hybrid (GH; EQUIA Forte Fil/EQUIA Forte Coat, GC) and adhesive/nanofilled resin composite restorations (RC; OptiBond FL, Kerr/Filtek Supreme XTE, 3M Oral Care) of sclerotic non-carious cervical lesions (sNCCL). Materials and Methods: This is an 18-month interim analysis of a 36-month cluster-randomized trial (ClinicalTrials.gov Identifier: NCT02631161). Eighty-eight patients (50–70 years) with 175 sNCCLs were randomized to receive GH or RC restorations. Restorations were placed without mechanical cavity preparation, and treatment time was recorded. After 18 months, restorations were evaluated using FDI criteria. Factors associated with restoration survival were evaluated using multi-level Cox-regression analysis. Generalized linear mixed modelling was used to analyze factors associated with treatment time. Results: After a mean of 18 months (min/max: 8/25), 78 patients (160 restorations) were assessed. Fifteen restorations (18%) failed in GH, and 11 (12%) in the RC, without a significant difference in survival (p = 0.904/Cox). Retention loss was the most common reason for failure in both groups. Restorations placed in older patients showed lower risk of failure [OR (95% CI): 0.90 (0.81–0.99) per year], while mandibular teeth showed higher risks [2.89 (1.00–8.31)]. Treatment time was significantly shorter for GH (mean ± SD: 8.6 ± 4.3 min) than RC (11.7 ± 5.7 min; p < 0.001). Conclusions: GH may be a suitable alternative to RC for restoring sNCCLs, without any significant difference in survival between the two materials at this interim analysis. In addition, placing GH restorations required less chairtime than did placing RC restorations. Keywords: composite resin, glass hybrid, glass ionomer, non-carious cervical lesion, randomized controlled trial, restoration, sclerotic dentin, treatment time

Purpose: The aim of this clinical trial was to compare a self-adhesive flowable resin composite, a highly filled flowable resin composite used in combination with a universal adhesive applied in self-etch mode, and a conventional flowable resin composite used in combination with a universal adhesive applied using two different application modes in occlusal cavities. Materials and Methods: Twenty-eight patients received 114 occlusal restorations. Cavities were divided into four groups: CS: a self-adhering flowable (Constic, DMG); GF: a highly filled flowable (G-ænial Universal Flo, GC) in combination with a universal adhesive applied in self-etch mode (G-Premio Bond, GC); TF-SE: a conventional flowable (Tetric N-Flow, Ivoclar Vivadent) in combination with a universal adhesive (Tetric N-Bond Universal, Ivoclar Vivadent) applied in self-etch mode; TF-ER: a conventional flowable (Tetric N-Flow, Ivoclar Vivadent) in combination with a universal adhesive (Tetric N-Bond Universal, Ivoclar Vivadent) applied in etch&rinse mode. Restorations were scored using modified USPHS criteria. Descriptive statistics were performed using chi-squared tests. Results: At 24-month evaluations, none of the restorations were lost. The CS group showed significantly higher bravo scores for marginal adaptation than did the other experimental groups (p = 0.024). Significant changes were seen for CS and GF regarding marginal adaptation compared to baseline. Conclusion: Although the self-adhering flowable resin composite exhibited inferior marginal adaptation compared to the highly filled flowable and conventional flowable resin composites, the restored teeth demonstrated a clinically acceptable performance after 24 months. Keywords: adhesive, dental materials, clinical research, resin composite

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. Keywords: adhesion, hydrophilicity, HEMA, microtensile bond strength, aging, gap formation, optical coherence tomography, acid-base resistant zone

Purpose: To investigate the effect of pretreatment protocols involving Papacarie Duo gel and Scotchbond Universal (SU) on the microshear bond strength (µSBS) of resin composite (RC) to hypomineralised enamel (HE). Materials and Methods: Specimens of normal enamel (NE) and HE were derived from extracted hypomineralised first permanent molars (FPMs). Based on the colour of demarcated opacities, HE specimens were classified as creamy/white (CW) or yellow/brown (YB). The specimens were randomly allocated into eight groups (n = 20). Each group involved pretreatment with Papacarie Duo gel or no pretreatment, and SU applied in etch-and-rinse (E&R) or self-etch (SE) mode. All specimens were bonded with RC and subjected to µSBS testing. Failure modes were analysed using an optical microscope and SEM. Results: Comparing NE with HE, the following factors were found to be significant (p < 0.001): type of enamel substrate, deproteinising pretreatment, and etching mode. Comparing CW HE with YB HE, a significant interaction between “deproteinising pretreatment” and “etching mode” was demonstrated (p = 0.028). When subjected to the concurrent use of Papacarie Duo gel and phosphoric acid etching, HE specimens showed a significant increase in µSBS (p < 0.001). Conclusion: Deproteinising pretreatment using Papacarie Duo gel followed by the application of SU in E&R mode led to increased µSBS of resin composite to HE. Keywords: bonding, deproteinisation, hypomineralised enamel, microshear bond strength, Papacarie, Scotchbond Universal

Purpose: To characterize experimental adhesives containing natural antimicrobial agents (proanthocyanidins, apigenin, tt-farnesol) in the primer and to evaluate their anti-caries effect. Materials and Methods: Natural agents were incorporated in the primer of an experimental adhesive: 4.5% proanthocyanidins (PA), 1 mM apigenin (API), 1 mM apigenin + 5 mM tt-farnesol (API + FAR), and primer without antimicrobial agent (control). Microtensile bond strength (μTBS) to dentin and nanoleakage were measured immediately (n = 7) and after 1 year of storage (n = 7). Water sorption (WS), solubility (SO), and degree of conversion (DC%) of the adhesives were measured. The hardness loss of enamel (n = 6) and dentin (n = 6) at the restorative margin was evaluated after biofilm formation. Results: DC%, nanoleakage, and immediate μTBS were similar for all groups. After 1 year, API + FAR showed higher nanoleakage and lower μTBS than the other groups, which were similar. WS and SO of API + FAR were lower than in the other groups. PA, API, and API + FAR presented less hardness loss than did the control group. At enamel, PA and API presented less hardness loss than the control and API + FAR groups at distances 50 µm and 100 µm; the hardness loss of enamel was similar for all groups 150 µm from the margin. Conclusion: The addition of proanthocyanidins and apigenin to the adhesives decreased the hardness loss of dentin and enamel submitted to biofilm formation, without jeopardizing the physical properties of the adhesives. The combination of apigenin + tt-farnesol decreased the hardness loss of dentin but not of enamel, and decreased the μTBS after 1 year of storage. Keywords: adhesion, adhesive systems, apigenin, proanthocyanidins

Purpose: To validate the rationale of using a conventional light-curing resin-based composite (RBC) to lute thick indirect restorations by measuring mini-interfacial fracture toughness (mini-iFT). Materials and Methods: Freshly exposed dentin of extracted third molars (n = 64) was immediately sealed with a thin layer of an experimental RBC with a 50 wt% or 75 wt% (IDS) filler load. Two- or 6-mm-thick CAD/CAM composite blocks were luted onto IDS using either pre-heated light-cure or dual-cure luting RBC, with the latter having served as control. Samples were cut into sticks, upon which a notch was prepared at the interface between IDS and luting RBC, prior to being submitted to a 4-point bending test to determine mini-iFT. The results were analyzed using a mixed linear model (LME). Failure mode at the fractured interface was determined using scanning electron microscopy (SEM). Results: LME revealed that mini-iFT was not significantly affected by the composite block thickness (p = 0.39), but by the luting RBC (p < 0.0001) and the IDS RBC filler load (p = 0.0011). Mini-iFT was higher with 50 wt% filler-loaded RBC IDS and when luted using the light-curing RBC. Conclusion: This work provides the proof of concept that 2- and 6-mm-thick indirect restorations can safely be adhesively luted with pre-heated conventional light-cure RBC under controlled light-irradiation conditions. This strategy even seems beneficial in terms of mini-iFT compared to using a dual-cure luting RBC. IDS with lower filler content also appeared more favorable. Keywords: adhesion, composite resin, computer-aided design/computer-aided manufacturing (CAD/CAM), dental cement, dual cure, interfacial fracture toughness, light cure, resin-based luting composite.

Purpose: To evaluate the effect of heated and room-temperature hydrofluoric (HF) acid on surface roughness parameters (Ra and Rq) and microtensile bond strength (μTBS) on feldspathic ceramic and lithium-disilicate glass-ceramics. Materials and Methods: Disk-shaped samples made from both ceramics were divided into groups according to surface treatment: feldspathic ceramic polished surface (FP), feldspathic ceramic + 60 s of 9% HF acid etching at room temperature (FC), feldspathic ceramic + 60 s of 9% HF acid etching heated to 70ºC (F70), lithium-disilicate polished surface only (LP), lithium disilicate + 20 s of 9% HF acid etching at room temperature (LC), and lithium disilicate + 20 s of 9% HF acid etching heated to 70ºC (L70). To evaluate Ra and Rq, non-overlapping readings were taken on the surface of each sample with a contact stylus profilometer. To measure microtensile bond strength (μTBS), samples of groups FC, F70, LC and L70 received their corresponding surface treatment, were silanized and then bonded using a dual-cure composite cement to resin composite disks. After 24 h, samples were sectioned to obtain specimens for μTBS. Representative samples from each group were examined using scanning electron microscopy (SEM) to analyze the morphology of the etched surface. The data were analyzed for statistical significance using Welch’s ANOVA with the Games-Howell multiple-comparison post-hoc test. Results: For both surface roughness parameters and HF acid etching at room temperature (FC and LC) showed a significant increase (p < 0.001) in surface roughness when compared to polished surfaces (FP and LP). Furthermore, the use of heated HF acid etching significantly increased (p < 0.001) the surface roughness of the ceramic when compared to their counterpart sample of HF acid etching at room temperature. Group L70 obtained the highest μTBS of all groups (29.11 ± 8.26 MPa) and was significantly higher (p < 0.001) than that of the other experimental groups. There were no statistical differences (p > 0.05) between groups FC (19.94 ± 4.14), F70 (18.24 ± 5.29), and LC (17.87 ± 6.96). Conclusion: The use of 9% HF acid etching heated to 70ºC resulted in significantly higher surface roughness and improved bond strength onto lithium-disilicate glass-ceramic compared to surface HF acid etching at room temperature. Keywords: lithium disilicate, feldspathic ceramic, microtensile bond strength, heated hydrofluoric acid, surface roughness

Purpose: To investigate the effects of four commercial silver diamine fluoride (SDF) agents on the chemical composition and microstructural properties of dentin, and its relation to the bond strength of two adhesives. Materials and Methods: Ninety human molars were randomly divided into sound dentin (negative control), demineralized dentin (positive control), and four experimental groups (n = 15) according to the SDF treatments (Cariestop [Biodinamica Quimica y Farmaceutica], RivaStar 1 [SDI], RivaStar 2 [SDI], and Saforide [Tokyo Seiyaku Kasei]). ATR-FTIR, x-ray diffraction, and SEM techniques were employed to characterize the compositional, crystalline, and microstructural properties of the samples. The microtensile bond strength test evaluated the bonding performance of two adhesives in demineralized dentin treated with SDF agents. Results: Regarding the chemical composition, all SDF-treated groups showed a significantly higher phosphate:organic matrix ratio than the demineralized dentin group (p < 0.05). The XRD analyses revealed that the crystallite size for hydroxyapatite crystals increased on the surface areas (deep, medium, and superficial dentin) for all experimental groups compared to demineralized dentin (p < 0.05). SEM images showed that the behavior of the agents used differs on each surface treated. Bond strength values were adversely affected with both adhesive systems in the four experimental groups (p < 0.05). Conclusions: The application of SDF agents resulted in the formation of different crystalline phases of silver salts and the increase of mineralization of the pretreated demineralized dentin. However, SDF application showed a negative effect on the bond strength of the adhesives. Keywords: adhesion, chemomechanical, dentin, mechanical tests, silver diamine fluoride

Purpose: To investigate the bond strength and durability of a novel dual-curing composite cement to zirconia under different curing conditions. Materials and Methods: Zirconia plates of different thickness (0.5, 1, and 2 mm) were bonded with either a novel dual-curing composite cement (Panavia V5, PV5, Kuraray Noritake) or a traditional one (RelyX Ultimate, RUL, 3M Oral Care; Multilink Automix, MLA, Ivoclar Vivadent), in light-, self-, or dual-curing mode. Bonded specimens were subjected to shear bond strength (SBS) tests after 24 h of water storage or after artificially aging by 20,000 thermal cycles plus 150 days of water storage. The degree of conversion (DC) of the composite cements under different curing conditions was measured by Fourier transform infrared (FTIR) spectroscopy. The irradiance and translucency of the zirconia plates of different thickness were also investigated. Results: The irradiance and translucency of zirconia decreased significantly with increasing thickness (p = 0.00). Both before and after aging, SBS of PV5 in self-curing mode was significantly higher than that of RUL (p = 0.07 before aging and 0.02 after aging) and MLA (p = 0.00 both before and after aging). However, for the three composite cements, light- and dual curing yielding the same SBSs for a constant Y-TZP thickness (p > 0.05). The FTIR analysis showed that, for all three dual-curing composite cements examined in this study, the mean DC values obtained in dual-curing mode were lower than those achieved in light-curing mode (p = 0.00 for PV5, RUL, and MLA). For RUL and MLA, lower mean DC values were obtained in self-curing than dual-curing mode (p = 0.00 for both RUL and MLA), while the DC values of PV5 showed no significant difference between self-curing and dual-curing mode (p = 0.33). Conclusion: When the photoactivation time is 60 s and the thickness of the zirconia restoration is less than 2 mm, it is safe to use the two traditional dual-curing composite cements RUL and MLA and PV5 for bonding zirconia. However, when the light exposure time is insufficient, PV5 provides improved bond strength and durability to zirconia. Keywords: dual-cure, curing mode, zirconia, thickness, shear bond strength, degree of conversion

Purpose: To evaluate the effect of different HF-etching protocols on the dissolution depth and micromorphology of the etched and adjacent surfaces of ultrathin glass-ceramic specimens. Materials and Methods: One hundred twenty specimens (6 x 6 x 0.3 mm) of leucite-reinforced glass-ceramic (LEU, IPS Empress, Ivoclar Vivadent) and lithium-disilicate-reinforced glass-ceramic (LD, IPS e.max, Ivoclar Vivadent) were prepared. Specimens were divided into 5 groups (n = 12) according to etching protocol: G1: control, untreated; G2: 5% hydrofluoric acid (HF) etching for 20 s (HF5%20s); G3: HF5%60s; G4: HF10%20s; and G5: HF10%60s. To analyze the dissolution depth, specimens were sectioned into two similarly sized halves using a chisel to create an internal surface (IS). Specimens were analyzed with scanning electron microscopy (SEM) on the following surfaces: HF application surface (AS), lateral surface (LS), internal surface (IS), and the surface opposite to the AS (OS). Dissolution patterns were identified. Data were submitted to one-way ANOVA and Bonferroni’s test (α = 0.05). Dissolution depth data were submitted to Kruskal-Wallis and Mann-Whitney U-tests (α = 0.05). The prevalence of different dissolution patterns was analyzed using SEM. Results: HF gel applied on the AS also affected the adjacent surfaces of all specimens. Different dissolution patterns were observed, which were dependent of HF-etching protocol and proportion of the glass phase in the ceramic. These patterns were categorized into four types for LEU (I-IV) and three for LD (I-III) according to the micropore size. The greater the micropore size, the more pronounced the etching pattern (p < 0.001). Higher HF times and concentrations showed prevalence of more severe etching patterns. HF10%60s produced greater dissolution depth in both materials when compared with other HF-etching groups (p < 0.05). Conclusion: Hydrofluoric acid etching not only affects the surface upon which it is applied, but internal, lateral and even opposite edges of glass ceramic. Different dissolution patterns and depths can be formed which are dependent of hydrofluoric acid concentration, application time, and proportion of the glass phase in the ceramic. Keywords: ceramics, hydrofluoric acid, acid etching, etching deepness, scanning electron microscopy, surface treatments

Purpose: To evaluate the effect of dimethyl sulfoxide (DMSO) on the microtensile bond strength (µTBS), nanoleakage (NL), and degree of conversion (DC) of universal adhesives on eroded dentin. Materials and Methods: One hundred thirty-four extracted (134) human third molars were selected for the study. After the dentin surface was exposed, 128 teeth were randomly assigned to 16 experimental groups as follows: dentin surfaces (sound dentin and eroded dentin), application of DMSO (without or with the application of DMSO), and adhesive strategies (etch-and-rinse [ER] and self-etch [SE]). The universal adhesive systems iBond Universal (IBU) and Scotchbond Universal (SBU) were applied and the teeth were restored using a resin composite. After 24 h in distilled water at 37ºC, the samples were sectioned and evaluated for μTBS. Selected sticks from each tooth were used for evaluating NL and DC. The remaining six teeth were used to measure the thickness of the collagen layer of the artificially eroded dentin using scanning electron microscopy. Data on μTBS, NL, and DC (%) were analyzed using three-way ANOVA and Tukey’s test (α = 0.05). Results: Significantly lower μTBS (p = 0.0001) and DC (p = 0.01) were observed for eroded dentin than for sound dentin. However, a significant increase in the μTBS (p = 0.0007) and DC (p = 0.001) was observed for both substrates when DMSO was applied. Moreover, the application of DMSO decreased the concentration of silver nitrate at the bottom of the hybrid layer for both sound and eroded dentin (p = 0.002). Eroded dentin showed enlarged tubules with the presence of a collapsed collagen fibril layer approximately 5.0 ± 2.0 mm of thickness. Conclusion: The bonding performance of both tested universal adhesives improved on both sound and eroded dentin with DMSO pretreatment. Keywords: dimethyl sulfoxide, adhesive, microtensile bond strength, tooth erosion