The Journal of Adhesive Dentistry, 05/2020

Purpose: To systematically review the literature to determine whether silane combined with adhesive application improves the repair bond strength of direct methacrylate-based resin composites in comparison to the use of an adhesive alone. Materials and Methods: The literature up to December 2019 was searched through PubMed/MEDLINE, Scopus, and Lilacs databases with no publication year or language limits. From 676 potentially eligible studies, 81 were selected for full-text analysis, and 19 were included in the systematic review. Two reviewers independently selected the studies, extracted data, and assessed the risk of bias. Meta-analyses were conducted using a random effects model to calculate pooled mean differences between adhesive- vs silane-plus-adhesive surface treatments (global meta-analysis) and considering subgroup analyses (immediate and aged repair bond strengths and type of silane – hydrolyzed or nonhydrolyzed). Statistical analyses were performed using RevMan5.3 at a significance level of 5%. Results: Global meta-analysis showed that the use of silane prior to adhesive application produced significantly higher repair bond strengths (p=0.003). A higher mean difference (effect size: 7.30, 95% CI: 2.91-17.51) between groups was found when nonhydrolyzed silanes were used. The heterogeneity was high. Studies scored between medium and high risk of bias. Conclusion: An additional silane application step could increase the repair bond strength of methacrylate-based resin composites. Keywords: methacrylate functional silane, bond strength, repair, resin-based composites

Purpose: This case report presents the management of molar incisor hypomineralization (MIH) from the mixed to the permanent dentition stage. Shortly after eruption of hypomineralized teeth, masticatory forces frequently cause rapid enamel breakdown. The MIH Treatment Need Index (MIH-TNI) provides guidelines for the treatment of MIH in relation to how severely the teeth are affected. Clinical considerations: An 11-year-old patient with permanent teeth affected by MIH was referred to us by his orthodontist for conservative dental treatment before planned orthodontic treatment. The restorative treatment varied according to the degree of severity of the affected teeth and included indirect composite resin restorations on teeth #17 (MIH-TNI 4c), #35 (MIH-TNI 4c) and #37 (MIH-TNI 4b), direct composite resin fillings on teeth #26 (MIH-TNI 2b), #27 (MIH-TNI 2a) and #16 (MIH-TNI 4c) and fissure sealants on teeth #16, 15, 14, 24, 25, 34, 36, 44, 45, 46 and 47. Orthodontic treatment was already started during the restorative phase with a bite-jumping appliance. With the conclusion of the second phase of mixed dentition at age 12, the orthodontist was able to start fixed orthodontic treatment of the maxillary and mandibular arches with all of the child's permanent teeth adequately restored. Orthodontic treatment was completed at age 14. At present, 6 years after initiation of dental treatment, all teeth are still free of decay. Conclusion: A carefully supervised recall program with early comprehensive care at frequent intervals and adequate, defect-driven restorations depending on how severely the teeth are affected are the basis for a favorable long-term prognosis in patients with MIH. Keywords: molar incisor hypomineralization, enamel hypomineralization, permanent dentition, indirect composite resin restoration

Purpose: This sub-analysis of our multicenter trial was to assess the long-term periodontal health (PH) of teeth, esthetically reshaped by means of direct composite buildups. Materials and Methods: 198 patients who received 667 direct composite buildups on 585 treated teeth (TT) between 01/2001 and 12/2013 were included. PH was assessed for each TT and for an untreated control tooth (CT) by recording the pocket probing depths (PPD), clinical attachment level (CAL), sulcus bleeding index (SBI), and Turesky's modification of the Quigley Hein plaque index (PI). Statistical analysis was performed using the two-sample Student's t-test and Mann-Whitney U-test. Regression models were performed to check for associations between PH and patients' age, gender, age of the buildups, enlargement range, jaw, and tooth type. The level of significance was set at α = 0.05. Results: PI scores were significantly (p < 0.001) higher in TT (1.60 ± 0.81) than in CT (1.41 ± 0.81). Differences between TT and CT regarding PPD (TT: 2.14 ± 0.56/CT: 2.18 ± 0.56), CAL (TT: 2.34 ± 1.05/CT: 2.33 ± 0.92), and SBI (TT: 0.41 ± 0.60/CT: 0.41 ± 0.65) were not statistically significant (p > 0.05). The enlargement range of the TT and the tooth type were not associated with PH. Male patients had significantly higher PPDs, CAL, and SBI values than did female patients. CAL and SBI values increased over time for both the TT and CT. CAL, SBI, and PI values were significantly higher in the mandible and the PPD values in the maxilla. Conclusion: Direct composite buildups made for reshaping, change of color or position of teeth did not impair PH in the long term. Keywords: direct composite buildups, recontouring, multicenter study, periodontal health, esthetical reshaping, gingivitis, periodontal destruction

Purpose: To evaluate the bleaching efficacy and shear bond strength (SBS) of composite restorations performed immediately after bleaching with a newly developed experimental bleaching agent, including 6% hydrogen peroxide (HP), titanium dioxide (TiO2), and/or chitosan (CS). Materials and Methods: We randomly divided 132 maxillary anterior teeth into 2 study groups, 60 teeth for color analysis and 72 teeth for the SBS test. For color analysis, teeth were divided into 5 subgroups. For SBS analysis, teeth were divided into 6 subgroups according to bleaching agent: group C (control): no bleaching; group 35HP: whiteness 35% HP; group 6HP: 6% HP; group HPC: 6% HP+CS; group HPT: 6% HP+TiO2; group HPTC: 6% HP+ TiO2+CS. The teeth were measured with a spectrophotometer before and 24 h after the bleaching, and calculated with the CIEDE2000 formula. SBS test was evaluated in composite restorations immediately after bleaching, using a universal testing machine. Statistical analysis was performed using ANOVA. Results: The highest ∆E00 values were observed in group 35HP (4.2 ± 1.2); the lowest value was observed in group 6HP (1.7 ± 0.6) (p < 0.05). The values for groups HPC and HPT were similar to each other and significantly lower than the value for 35HP (p < 0.05 and p > 0.05, respectively). Group HPTC was similar to 35 HP (p > 0.05). For SBS, all groups except those containing chitosan showed significantly decreased bond strength compared to the control (p < 0.05), while groups HPC and HPTC had values similar to the control (p > 0.05). Group C (28.02 ± 6.81) had the highest value, while group 35HP (17.02 ± 7.79) had the lowest SBS value. Conclusion: With the newly developed agent, the bond strength immediately after bleaching was found to be similar to the control group. Its bleaching efficacy was similar to that of routinely used bleaching agents. Keywords: hydrogen peroxide, titanium dioxide, chitosan, tooth bleaching

Purpose: Universal adhesives (UAs) are applied in 2-step etch-and-rinse (2-E&R) or 1-step self-etch (1-SE) mode. This study investigated whether three UAs could benefit from a highly filled extra bonding layer (EBL), turning them into 3-E&R and 2-SE UAs, respectively, thus also compensating for the commonly thin film thickness of UAs. Materials and Methods: Microtensile bond strength (μTBS) to bur-cut dentin of Clearfil Universal Bond Quick (C-UBq, Kuraray Noritake), G-Premio Bond (G-PrB, GC) and Prime&Bond Active (P&Ba, Dentsply Sirona), applied in E&R and SE mode without/with the adhesive resin (EBL) of OptiBond FL (Opti-FL_ar, Kerr), was compared to that of the 3-E&Ra OptiBond FL (Opti-FL; Kerr), which was also employed in 2-SE mode. As a cross reference, the SE primer of Clearfil SE Bond 2 (Kuraray Noritake) was combined with Opti-FL_ar (C-SE2/Opti-FL) and again applied in 2-SE and 3-E&R mode. μTBS was measured after 1 month of water storage (37°C) and additional 25,000 and 50,000 thermocycles (TC). All μTBS were statistically analyzed using three different linear mixed-effects models with specific contrasts (p < 0.05). Results: Overall, the four parameters (adhesive, bonding mode, aging, EBL) significantly influenced μTBS. G-PrB and P&Ba benefited from EBL when applied in both E&R and SE bonding modes. In E&R mode, P&Ba generally revealed the highest µTBS; C-UBq presented an intermediate and G-PrB the lowest µTBS. No significant differences were found between different bonding modes. C-SE2/Opti-FL outperformed Opti-FL in 3-E&R and 2-SE_1 month/25k. Conclusion: The overall benefit of EBL on the 1-month and TC-aged bonding efficacy differed for the different UAs tested. Keywords: bond strength, durability, hydrophobic, linear mixed model (LME), adhesive-dentin interface

Purpose: To compare shrinkage stress, cuspal strain and fracture load of weakened premolars restored with different conventional and bulk-fill composite resins and restorative techniques. Materials and Methods: Fifty premolars received a 4.0 x 3.5mm mesio-occlusal-distal (MOD) class II preparation. The lingual and buccal cups were internally weakened. Specimens were restored according to the following 5 groups: Filtek Z350 XT/10 increments; Filtek Z350 XT/8 increments (both 3M Oral Care); Filtek Bulk Fill Flowable Restorative + Filtek Z350 XT (both 3M Oral Care); SDR + Spectra Basic (Dentsply Sirona); and Tetric N-Ceram Bulk Fill (Ivoclar Vivadent). Cuspal strains were measured using strain gauges (n = 10). After restoration, specimens were submitted to thermal/mechanical cycles and fractured. Post-gel shrinkage of the composites was determined. Additionally, residual shrinkage strains and stresses were analyzed using three-dimensional finite element analysis (3D-FEA). The data were statistically analyzed using one-way ANOVA and Tukey's HSD (α = 0.05). Results: One-way ANOVA revealed statistically significant differences among composite resins (p < 0.001) for the post-gel shrinkage. Filtek Z350 XT had the highest post-gel shrinkage and no difference was found between Spectra Basic and Tetric N-Ceram Bulk Fill (p = 0.110). The Filtek Z350 XT/10 increments, Filtek Z350 XT/8 increments and Filtek Bulk Fill Flowable Restorative/Filtek Z350 XT had statistically significantly higher cuspal deformation values when compared to the SDR/Spectra Basic and Tetric N-Ceram Bulk Fill techniques. 3D-FEA confirmed higher stress levels in the incrementally filled conventional restorations. Fracture loads were not statistically significantly different. Conclusion: The bulk-fill restoration techniques resulted in less cuspal strain and stress than the incremental technique with conventional composite resin. Fracture resistance was not affected by the restorative techniques. Keywords: biomechanics, cuspal strain, finite element analysis, fracture resistance, shrinkage stress

Purpose: To evaluate the biocompatibility in rat subcutaneous tissue of conventional orthodontic cements, Riva (R) and Meron (M), modified by the addition of ethanolic extract of red propolis (EERP), at different concentrations and time intervals. Materials and Methods: One hundred eight male adult Wistar rats were used, distributed in nine groups of cements with added EERP at the concentrations used (C-control, MC, M10, M25, M50, RC, R10, R25, and R50). The rats were sacrificed after 3 time intervals (7, 15, and 30 days). Histological and immunohistochemical analyses were performed. The findings were statistically analyzed using the Kruskal-Wallis test followed by Dunn's test (p < 0.05). Results: The highest concentrations led to a higher level of inflammation at the initial times (p < 0.05), but without differences after 30 days. In terms of collagen, there was less collagenization at the initial times in comparison with the control group C. However, over time, the addition of propolis resulted in healing compatible with that of group C. The level of CD68 immunostaining was statistically significantly higher in the groups with the highest concentrations (R50 and M50) (p = 0.001). Conclusion: Orthodontic cements with the addition of EERP were found to be biocompatible in rat subcutaneous tissue. Riva cement with the addition of 50% EERP showed the highest tissue inflammation, but with satisfactory tissue repair. Keywords: glass-ionomer cements, propolis, biocompatibility

Purpose: To evaluate the effect of composite resin polymerization shrinkage stress on the stress distribution in the implant-supported crown-access hole, and on the bond strength between the ceramic and composite resin. Materials and Methods: A 3D model of a ceramic crown, in which the access hole was filled with composite resin (conventional or bulk-fill), was used to evaluate the stress distribution in the access hole using finite element analysis. The contacts were considered bonded and the polymerization shrinkage was simulated based on the coefficient of linear thermal expansion of each resin. The push-out test (1 mm/min, 100 kgf) was performed on perforated lithium disilicate samples filled with conventional or bulk-fill resins to validate the stress data of the bond strength. One-way ANOVA and Tukey's test were used to analyze the bond strength data, with α set at 5%. Results: Conventional resin showed the worst stress distribution and highest displacement values, von Mises stress, maximum principal strain, maximum principal stress, and maximum shear stress vs the bulk-fill resin. Statistically significantly greater bond strength was observed for bulk-fill (13.40 ± 5.59 MPa) than the conventional resin (8.70 ± 3.02 MPa). Conclusion: Comparing both materials tested in the present study, the use of bulk-fill composite resin to seal the screw-access hole is suggested to reduce the stress concentration and increase bond strength to the ceramic crown. Keywords: composite resins, finite element analysis, incremental technique, polymerization

Purpose: To evaluate the roughness, surface energy, and the bond strength of lithium disilicate yielded by two different types of nonthermal plasma (NTP), oxygen- or argon-based, compared to the conventional method. Materials and Methods: Ninety-three lithium disilicate (IPS e.max Press) samples were divided into 3 groups: HF (hydrofluoric acid group); ONTP (oxygen-based NTP group); ANTP (argon-based NTP group). Surface energy and roughness analyses were performed before and after surface treatment, and bond strength testing was performed before and after 5000 thermocycles. Scanning electron microscopy (SEM) was used to characterize the surface treatments. Data were submitted to ANOVA and Bonferroni's test with statistical significance set at 5%. Results: The ONTP group presented the highest surface energy values, followed by ANTP and HF. In addition, the ONTP group had higher surface roughness. SEM revealed exposed lithium disilicate crystals in the HF group, but a homogeneous film coverage in both NTP groups. Regarding bond strength, ANTP presented statistically significantly higher values than the other groups before thermocycling, and statistically significantly lower values than the other groups after thermocycling. The HF and ONTP groups presented statistically similar values after thermocycling. Conclusion: The bond strength of resin cement to lithium disilicate obtained after oxygen-based NTP was comparable with that obtained after conventional hydrofluoric acid treatment. Keywords: ceramic, lithium disilicate, surface treatment, shear bond strength, nonthermal plasma