The Journal of Adhesive Dentistry, Volume 26/2024

Purpose: To investigate the microtensile bond strength (µTBS) to dentin in class-I cavities using different layering techniques, adhesive application modes, and aging. Materials and Methods: 150 caries-free human molars were randomly assigned to 8 experimental and 2 control groups (n=15 teeth/ group). For each tooth, a standardized class-I cavity was prepared (4x4x4 mm) and pretreated with a universal adhesive (self-etch or etch-and-rinse mode). Incrementally layered restorations served as the control. In the experimental groups, either lining with bulk-fill flowable composite and a layering technique, bulk filling, or the snowplow technique with one or two layers of viscous composite were applied. Four microsticks were obtained from each cavity. Half were tested initially and the other half after aging (thermocycling, 15,000 cycles, 5-55°C, n=30 sticks/group). Tobit regression was used for analyzing group differences, including analysis of interactions, Pearson’s chi-squared test or Fishers’s exact test for fracture analyses (significance level 0.05). Results: Regression analysis showed significant differences in µTBS between groups initially and after aging. In both etching modes, lining with a bulk-fill flowable composite and layering technique achieved the highest µTBS both initially and after aging. In contrast to the etching mode (self-etch < etch-and-rinse), aging did not influence µTBS significantly. The predominant failure types were adhesive and mixed, with a significantly lower number of pre-test failures in the etch-and-rinse groups. Conclusion: The etch-and-rinse mode achieves higher µTBS in class-I cavities compared to the self-etch mode. The lining technique with bulk-fill flowable composite as well as the snowplow technique yielded the highest µTBS after aging, whereas bulk filling and its combination with the snowplow technique resulted in lower µTBS. Keywords: class-I cavity, snowplow technique, bulk filling, µTBS, configuration factor

Purpose: To evaluate the effect of different lithium-disilicate (LiSi) glass-ceramic surface decontamination procedures on the shear bond strength (SBS) to resin cement. Materials and Methods: Seventy CAD/CAM LiSi ceramic specimens (IPS e.max CAD, Ivoclar) were cut and sintered. Fifty specimens were treated with 5% hydrofluoric acid (HF) for 20 s, while 20 were left untreated. All 70 specimens were then contaminated with human saliva and try-in silicone paste. The following surface cleaning methods were investigated (n = 10): C: water rinsing (control); PA: 37% H3PO4 etching for 20 s; E: 70% ethanol applied for 20 s; CP: cleaning paste (Ivoclean, Ivoclar) brushed for 20 s; HFSEP: self-etching ceramic primer (Monobond Etch&Prime, Ivoclar) rubbed for 20 s; HF: 5% HF applied for 20 s or no HF etching prior to contamination; SEP: self-etching ceramic primer rubbed for 20 s and no HF etching prior to contamination. Composite cylinders were created and luted with an adhesive resin cement to the decontaminated surfaces. After storage for 24 h at 37°C, the SBS test was conducted. Two fractured specimens per group were observed under SEM to perform fractographic analysis. The data were statistically analyzed with p set at <0.05. Results: The type of surface cleaning approach influenced bond strength (p < 0.001). HFSEP, SEP, and HF attained higher SBS (p < 0.001) compared to other groups. None of the approaches were able to completely remove contaminants from the ceramic surfaces. SEM images showed residual traces of contaminants on CP-treated surfaces. Conclusions: The self-etching ceramic primer enhanced bond strength to contaminated LiSi ceramic surfaces, irrespective of previous treatment with hydrofluoric acid. Keywords: lithium-disilicate glass-ceramic, surface cleaning, decontamination, hydrofluoric acid, ceramic primer, shear bond strength

Purpose: The study evaluated the clinical performance of partial indirect resin composite (PIRC) restorations with “proximal box elevation” (PBE) placed in molars. Materials and Methods: Sixty-three patients received 80 posterior PIRC (SR Nexco, Ivoclar Vivadent) restorations. Large posterior defects with cuspal loss and deep cervical margins were included in the study. PBE was performed prior to preparation and impression making. Two independent observers evaluated the restorations using the FDI criteria (scores 1-5) for esthetic, functional, and biological properties. Patients were recalled at 6 months and 1, 2, and 3 years. Overall success rates were calculated (Kaplan-Meier analysis) and compared (log-rank tests) according to baseline variables. The impact of the baseline variables on the failure of the restorations was analyzed (multiple proportional Cox regression). Results: Seventy-nine (98.7%), 69 (88.4%), 66 (92.9%), 44 (86.2%) and 45 (91.8%) PIRCs completed their follow up at baseline, 6 months, and 1, 2 and 3 years, respectively. In total, 10 failures were observed: 5 with partial loss, 4 with material chipping, and one with secondary caries, yielding an overall success rate of 87.5% and a survival rate of 93.8%, with a mean observation time of 26.5 ± 13.6 months. Conclusions: PIRCs with PBE demonstrated a high survival rate and satisfactory esthetic properties. Failure was less likely for PIRC restorations with partial cuspal coverage (onlay) compared to full cuspal coverage (overlay). Keywords: adhesive dentistry, clinical trial, dental materials, indirect resin composite, survival, proximal box elevation

Purpose: To compare the adhesion of a self-curing (Tokuyama Universal Bond, TUB) and a light-curing (Scotchbond Universal, SBU) universal adhesive to CAD/CAM materials, enamel, and dentin. This study also assessed differences in enamel adhesion between self-etch vs selective etching modes, as well as immediate and long-term adhesion to dentin for both adhesives. Materials and Methods: Shear bond strength (SBS) testing was used to assess adhesion to enamel, dentin, Lava Ultimate (LU), Vita Enamic (VE), IPS e.max CAD (LD), IPS e.max ZirCAD (3Y-Zir), and Lava Esthetic (5Y-Zir) (n = 10). Moreover, bonding to enamel in self-etch and selective etching modes (n = 10) as well as immediate and aged resin-dentin bond strength (24 h after bonding, after 100,000 thermal cycles [TC] and long-term storage) was evaluated using the microtensile bond-strength test (n = 30). Failure mode was also determined for the bonding to dentin. Statistical analyses consisted of one-way and two-way ANOVA with appropriate post-hoc Tukey-Kramer or two-sample t-tests, as well as the chi-squared or Fisher’s exact test (α = 0.05). Results: TUB and SBU universal adhesives presented similar bonding to LU, VE, 3Y-Zir, and 5Y-Zir. However, SBS for TUB was superior to SBU when bonding to lithium-disilicate glass-ceramic (IPS e.max CAD). SBU showed better adhesion to dentin and enamel when used in the self-etch mode, while TUB promoted strong bond strength to enamel in the selective etching mode. TUB after TC was the only aging condition that yielded a significant reduction in resin-dentin bond strength. Conclusion: In-vitro adhesion performance of the self-curing and light-curing universal adhesives varies depending on the dental substrate or CAD/CAM restorative material used for bonding. Keywords: universal adhesives, bond strength, resin cement, enamel, dentin, self-curing adhesive, CAD/CAM

Purpose: This study aimed to investigate the bonding effectiveness of two HEMA/BPA-free universal adhesives (UAs) to flat dentin, to characterize their adhesive-dentin interfacial ultrastructure, and to measure their water sorption (Wsp), water solubility (Wsl), and hydrophobicity. Materials and Methods: The immediate and aged (50,000 thermocycles) microtensile bond strength (μTBS) to flat dentin of the HEMA/BPA-free UAs Healbond Max (HbMax; Elsodent) and Healbond MP (HbMP; Elsodent) as well as the reference adhesives OptiBond FL (Opti-FL; Kerr), Clearfil SE Bond 2 (C-SE2; Kuraray Noritake), and Scotchbond Universal (SBU; 3M Oral Care) was measured. The adhesive-dentin interfaces of HbMax and HbMP were characterized by TEM. Wsp and Wsl of all adhesive resins and of the primer/adhesive resin mixtures of HbMax, Opti-FL, and C-SE2 were measured. Hydrophobicity was determined by measuring the contact angle of water dropped on adhesive-treated dentin. Results: In terms of µTBS, HbMax and HbMP performed statistically similarly to Opti-FL and C-SE2, but outperformed SBU. Aging only significantly reduced the μTBS of SBU when applied in E&R bonding mode. TEM revealed typical E&R and SE hybrid-layer ultrastructures at dentin, while electron-lucent globules of unknown origin, differing in size and shape, were observed within the adhesive resin of HbMP and even more frequently in that of HbMax. Higher Wsp was measured for the primer/adhesive resin mixtures than for the adhesive resins. Opti-FL was more hydrophobic than all other adhesives tested. Conclusion: The HEMA/BPA-free UAs bonded durably to flat dentin with bond strengths comparable to those of the gold-standard E&R/SE adhesives and superior to that of the HEMA/BPA-containing 1-step UA. Keywords: dental bonding, bond durability, water sorption, interface, HEMA, BPA

Purpose: This study investigated and compared the bond strengths, microleakage, microgaps, and marginal adaptation of self-adhesive resin composites (SAC) to dentin with or without universal adhesives. Materials and Methods: Dentin surfaces of 75 molars were prepared for shear and microtensile bond strength testing (SBS and µTBS). Silicon molds were used to build up direct restorations using the following materials to form 5 groups: 1. Surefil One; 2. Prime&Bond active Universal Adhesive + Surefil One; 3. Vertise Flow; 4. OptiBond Universal + Vertise Flow; 5. Scotchbond Universal + Filtek Z500 (control group). Bonded specimens were thermocycled 10,000x before being tested either for SBS or µTBS using a universal testing machine at a crosshead speed of 0.5 mm/min. Direct mesial and distal class-II cavities were created on 100 sound premolars, with the gingival margin of distal cavities placed below CEJ and restored according to the five groups. After thermocycling, microleakage scores were assessed following immersion of restored premolars in 2% methylene blue dye for 24 h, while marginal gaps and adaptation percentages were investigated on epoxy resin replicas under SEM at magnifications of 2000X and 200X, respectively. Results were statistically analyzed with parametric and non-parametric tests as applicable, with a level of significance set at α = 0.05. Results: Bond strengths, microleakage scores, microgaps, and percent marginal adaptation of Surefil One and Vertise Flow were significantly (p < 0.001) inferior to the control group. Dentin preconditioning with universal adhesives significantly increased the study parameter outcomes of Surefil One and Vertise Flow, yet they were still significantly below the performance of the control group. Conclusion: Conventional resin composite outperformed the SAC whether applied solely or in conjunction with their corresponding universal adhesives. Keywords: self-adhesive resin composites, universal adhesives, shear bond strength, microtensile bond strength, microleakage, marginal adaptation

Purpose: Multiple materials are found in the root canal after fiber-post cementation. The layer of a bioceramic-based (BC) sealer may affect the bond strength (σBS) of the fiber post in the root canal. The purpose of this study was to employ multilayer compos-ite-disk models in diametral compression to investigate whether the bond strength between a fiber post and root dentin can be in-creased by the application of a primer on the BC sealer. Materials and Methods: The multilayers of materials in the root canal required 3D finite-element (FE) stress analyses (FEA) to pro-vide precise σBS values. First, BC sealer was characterized using x-ray powder diffraction (XRD) to determine when the sealer com-pletely set and the types of crystals formed to select which primer to apply to the sealer. We selected a 10-methacryloyloxydecyl dihydrogen phosphate (10-MDP)-based primer to treat the BC sealer before post cementation. Ultra-highspeed (UHS) imaging was utilized to analyze the crack initiation interface. The obtained failure force was used in FE analysis to calculate σBS. Results: UHS imaging validated the fracture interface at the post-dentin junction as FEA simulations predicted. σBS values of the fiber posts placed with various material combinations in the root canal were 21.1 ± 3.4 (only cement/ post), 22.2 ± 3.4 (BC sealer/cement/post) and 28.6 ± 4.3 MPa (10-MDP primer treated BC sealer/cement/post). The 10-MDP-treated BC sealer exhibited the highest σBS (p < 0.05). Conclusion: The multilayer composite disk model proved reliable with diametral compression testing. The presence of BC sealer in the root canal does not reduce σBS of the fiber post. Conditioning the BC sealer layer with 10-MDP primer before fiber-post cemen-tation increases σBS. Keywords: bioceramic-based sealer, bond strength testing, fiber post, finite element analysis, multilayer composite-disk model, ultra- highspeed imaging

Purpose: This investigation aimed to assess the impact of additive manufacturing-generated surface textures on zirconia bond strength. Materials and Methods: Zirconia samples (n = 144) fabricated using digital light-processing (DLP) technology were categorized into 6 groups according to the type of surface conditioning (group NN: no designs, no air abrasion; group NY: no designs, with air abrasion; group GN: groove designs, no air abrasion; group GY: groove designs with air abrasion; group HN: hexagon grid, no air abrasion; group HY: hexagon grid, with air abrasion). Composite resin cylinders were cemented to the treated zirconia surfaces with dual-curing, self-adhesive resin cement (Clearfil SA Luting). The shear bond strength (SBS) was tested after water storage for 3 days or 3 days with an additional 10,000 thermocycles. Results: The zirconia samples fabricated using DLP technology have high accuracy. The SBS of the NY, GY, and HY groups did not significantly differ after 3 days, and neither did the SBS of the NN, GN, and HN groups. The NN, NY, and HY groups exhibited reduced SBS compared to their initial values following artificial aging, while the SBS of the remaining three groups were not diminished. The GY group obtained the highest SBS value after aging. Conclusion: Printing grooves with air abrasion can improve the bond strength. Keywords: additive manufacturing, bonding, resin cements, zirconia

Purpose: This paper describes previously unknown details about the discovery of resin adhesion to acid-etched human enamel. Materials and Methods: A literature review was performed through manual assessments. Primary sources revealing the discovery of resin curing on etched enamel were analyzed considering the research objectives and methodological procedure during that era, including the type of teeth used, preparatory measures, acid-etching process, type of resin and its application, and follow-up observations. Additionally, the political and economic contexts were examined. Results: In 1949, acid etching was found to promote adhesion with acrylic resin, a finding described again in 1955. The 1949 studies utilized nitric acid for enamel etching and the acrylate resin Paladon from the Kulzer company (Germany). Conversely, the 1955 investigations employed phosphoric acid and an unnamed acrylate, likely a self-curing resin supported by Kulzer in the late 1930s. Disparities in the 1949 and 1955 findings can be ascribed to varying objectives and test conditions amidst a turbulent political backdrop, significantly impacting the Kulzer company. Conclusion: The discovery of resin adhesion to acid-etched enamel, approaching its 75th anniversary in 2024, is a landmark in 20th-century adhesive dentistry. Paladon represents a pioneering compound, exemplifying the influence of political, ideological, and economic factors on scientific advancements during that period. Keywords: adhesion of acrylics to acid-etched enamel, history of adhesive dentistry, history of dental acrylics

Purpose: To investigate the influence of contamination and different cleaning methods on resin bonding to cobalt-chro-mium (CoCr) alloy disks. Materials and Methods: A total of 160 CoCr disks were divided into 3 groups. The first group (N = 64) was air abraded with alumina particles; the second group (N=64) was air abraded and contaminated with silicone disclosing agent and saliva; the third group (N = 32) was neither air abraded nor contaminated. The first two groups were divided into 4 subgroups (N = 16) according to the cleaning method: ultrasonic bath in 99% isopropanol, use of a cleaning suspension of zirconium oxide particles, use of a cleaning suspension based on 10-MDP salt, and treatment with atmospheric plasma. The third group was divided into 2 subgroups (N = 16): treatment with atmospheric plasma and no treatment. All CoCr specimens were bonded to plexiglas tubes filled with a bonding resin that contained phosphate monomer. Tensile bond strength (TBS) was examined by tensile testing after 3 and 150 days of water storage plus 37,500 thermal cycles (N = 8). Results: After contamination, TBS was significantly reduced after 150 days of water storage. Groups without air abrasion showed initially low TBS and debonded spontaneously after 150 days of water storage. Conclusion: None of the cleaning methods was able to remove saliva and silicone disclosing agent on CoCr-alloy sur-faces. Surface activation by plasma treatment has no long-term effect on the bond strength. Keywords: alloy, contamination, cleaning, bonding, plasma treatment

Purpose: To investigate the antibacterial effects of Terminalia catappa Linn (TCL) leaf extracts at different concentrations and the effects of these extracts used as primers on the long-term adhesive properties of two universal adhesives. Materials and Methods: After extract preparation, the antimicrobial and antibacterial activities of TCL against Streptococcus mutans (UA 159) were assessed in microdilution assays to provide the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC). Additionally, to provide quantitative data on the ability of TCL extract to reduce cell viability, colony forming units (CFU) were counted. To examine adhesive properties, 288 human molars were randomly assigned to 32 experimental conditions (n = 9) according to the following variables: (1) treatment agent: negative control (untreated surface), and primers at concentrations of 1xMIC, 5xMIC, and 10xMIC; (2) adhesives: Scotchbond Universal (SBU) and Futurabond Universal (FBU); (3) adhesive strategy: etch-and-rinse (ER) or self-etch (SE); and (4) storage time: 24 h or after 2 years. Primers were applied for 60 s, upon which the teeth were incrementally restored and sectioned into adhesive-dentin bonded sticks. These were tested for microtensile bond strength (μTBS) and nanoleakage (NL) after 24-h and 2-year water storage, as well as in-situ degree of conversion (DC) at 24 h. The chemical profile of the hybrid layer was determined via micro-Raman spectroscopy. Biofilm assay data were analyzed using the Kruskal-Wallis test; the pH of culture media and the chemical profile were analyzed by one-way ANOVA. The adhesive properties (µTBS, NL, DC) were evaluated using a four-way ANOVA and Tukey’s test. Significance was set at 5%. Results: Similar values of MIC and MBC were observed (2 mg/ml), showing bactericidal potential. CFU analysis demonstrated that concentrations of 5xMIC and 10xMIC significantly inhibited biofilm formation (p < 0.001). The application of the TCL primer at all concentrations significantly increased the immediate μTBS and DC, and decreased the immediate NL values when compared to the control group (p < 0.05), regardless of the adhesive and adhesive strategies. Despite an increase in the NL values for all groups after 2 years (p > 0.05), in groups where the TCL primer was applied, the μTBS remained constant after 2 years for both adhesives, while a decrease in the μTBS was observed in the control groups (p < 0.05). Usually, 10xMIC showed better results than 1xMIC and 5xMIC (p < 0.05). The application of TCL promoted cross-linking; cross-linking rates increased proportionally to the concentration of TCL (p < 0.05). Conclusion: Primers containing TCL promoted bactericidal and bacteriostatic action, as well as cross-linking with dentin, while maintaining the adhesive properties of the adhesive-dentin interface after 2 years of water storage. Keywords: microbial degradation, dentin adhesives, scanning electron microscopy, flavonoids

Purpose: The aim of this retrospective study was to assess the short- to mid-term restorative and periodontal outcome of deep margin elevation (DME) performed using resin composite. Materials and Methods: Twenty-eight teeth treated with DME and indirect adhesive restorations were followed-up for a mean of 25.4 months (minimum: 12 months). Clinical and radiographic examination assessed the adaptation of the DME material and indirect restorations, presence of recurrent caries or discoloration, periodontal health at DME and non-DME sites, and periapical health. Results: The overall success rate was 96.6%. One tooth showed signs and symptoms of apical pathology after 34 months following DME. No caries, discoloration, or periodontal pockets were detected in any of the treated teeth. DME had no detrimental effect on the gingival/periodontal health or plaque accumulation. There was no correlation between the distance from the DME material to the marginal bone level and pocket depth, gingival inflammation, and plaque accumulation (p > 0.05). Conclusion: Deep margin elevation might be considered a safe procedure for teeth with deep subgingival proximal caries in the short- and mid-term. Keywords: subgingival margins, deep margin elevation, cervical margin relocation, restorative dentistry