The Journal of Adhesive Dentistry, 01/2021

Purpose: To systematically review in vitro studies that evaluated adhesive-dentin bond strength with or without the addition of desensitizers. Materials and Methods: A search was conducted in four databases (PubMed, Embase, Web of Science, and Cochrane Library) without publication date or language limits in accordance with the Preferred Reporting Items for Systematic Reviews (PRISMA). Two reviewers selected the studies, extracted data, and assessed the risk of bias independently. The inclusion criterion was the evaluation of the effect of immediate or aged bond strength after applying desensitizer in the bonding step. The risk of bias was assessed following the method used by Sarkis-Onofre et al.41 Meta-analysis was conducted using Review Manager 5.3. Results: A total of 1636 articles were found using the search strategy above; 59 articles were selected for full-text analysis, and 32 were systematically reviewed, with 18 considered in the meta-analysis. Results showed a significant difference among various kinds of desensitizers. The subgroup comparison showed high heterogeneity among the different kinds of desensitizers. The use of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and arginine-CaCO3 showed no negative effect on the immediate bond strength, whereas other desensitizers showed some influence. Conclusion: Different desensitizers have various effects on microtensile bond strength. Desensitizers may be selected based on the bond strength and especially used to relieve tooth sensitivity after tooth preparation. Keywords: dentin, bonding, hypersensitivity, desensitizer, adhesive.

The importance of the interdental anatomy of a class-2 direct composite restoration is one of the most underestimated topics in direct posterior composite restorations. The proximal emergence profile of the restoration and the contact area should be designed to maximize arch continuity and to minimize food impaction. Other restorative criteria that must be fulfilled are marginal adaptation compatible with the dental and periodontal integrity, and geometry of the marginal ridge compatible with the mechanical integrity of the restoration under load. Shortcomings will result in masticatory discomfort, caries, periodontal problems and undesired movement of teeth. In vitro and in vivo studies showed that the use a contoured sectional metal matrix band with a separation clamp results in the tightest contact point. However, this matrix system also has shortcomings and does not give the expected result in all class-2 cavities. The variation in depth, width of the box, distance between the cervical cavity margin and the adjacent tooth requires customization of the interproximal space. In order to realize this, sectional matrix bands with several profiles of curvature, variation of wedges and separation clamps, and the use of teflon tape are required. In addition, dentists should follow a protocol allowing them to build a proximal composite surface that fulfills the required restorative criteria. Pre-wedging, space evaluation, interproximal clearance, correct selection, positioning and stabilization of the matrix band are important steps in this protocol. Keywords: class-2, composite resin restoration, matrix system, proximal contact point, proximal emergence profile

Purpose: To assess possible correlations between clinical outcomes and SEM marginal analysis in a prospective long-term clinical study using two adhesives in incisors and canines. Materials and Methods: Thirty-five patients received class III and IV restorations with two different adhesives, either the one-step self-etch adhesive iBond Gluma inside (1-SE) or the two-step etch-and-rinse adhesive Gluma Comfort Bond (2-ER) combined with the fine particle hybrid composite Venus. The restorations were clinically evaluated (modified USPHS criteria) over 90 months. Based on resin replicas, a quantitative marginal SEM analysis was performed using the criteria “gap”, “perfect margin”, “overhang”, and “underfilled”. The results of the quantitative marginal analysis were statistically compared and related to clinical evaluations. The SEM data were analyzed statistically using the Kolmogorov-Smirnov test, Wilcoxon test, and mixed models test.Results: Of the 35 subjects at baseline, 16 (1-SE) and 17 (2-ER) were clinically re-examined after 90 months. 13 patients were included in the SEM analysis due to uninterrupted documentation over 90 months or until restoration loss. SEM analysis showed larger discriminative power between groups than did the clinical examination, but the trend was the same. Marginal analysis (“gap”, “perfect margin”) showed significant differences between the materials after 12 months, which clinically began to show a trend from 12 months, and were statistically verified after 48 and 90 months. “Overhang” and “underfilled” did not reveal significant differences between the systems or over time.Conclusion: SEM marginal analysis using the replication technique is a powerful tool to reveal differences between adhesives. Compared to clinical evaluation, group differences can be detected earlier, with both outcome parameters confirming each other over long observation periods. Keywords: adhesion, composite, long term, clinical study, in vivo, SEM, USPHS criteria

Purpose: To study the effect of the varnish type, application time and surface polishing on the shear bond strength (SBS) of a universal adhesive in healthy and demineralized bovine enamel. Materials and Methods: 432 bovine primary central incisors were assigned to 18 groups according to enamel mineralization [healthy and demineralized], topical varnish [Clinpro White Varnish (CWV; 3M Oral Care) and Profluorid (PFV, Voco)], remineralization time [24 h or 21 days] and polishing or not of the enamel surface. Adhesion was tested using Futurabond M (Voco)+ and GrandioSO (Voco). Sheer bond strength (SBS) was measured and the fracture mode studied. The statistical analysis was performed using two-way ANOVA, Tukey’s test, and Pearson’s chi-squared test. Results: In healthy bovine enamel, CWV reduced SBS at 24 h and 21 days; polishing significantly improved SBS. PFV increased SBS in healthy enamel at 21 days and demineralized enamel at 24 h and 21 days; polishing had no effect on SBS. The application time and polishing of the enamel surface affected the behavior of varnishes with respect to SBS. There was a correlation between the type of fracture and the degree of mineralization as well as the timepoint of varnish application. Conclusions: Remineralization of demineralized enamel with fluoride varnishes permits the recovery of the bond strength obtained in healthy enamel. Of the two varnishes studied, PFV had the highest SBS and more uniform behavior, regardless of the application timepoint, degree of mineralization, and surface treatment of the enamel. Keywords: demineralization, enamel, remineralization, fluoride varnish, tricalcium phosphate, shear bond strength

Purpose: To evaluate in vitro the effect of saliva contamination on bond strength of a universal adhesive applied with actively (with rubbing motion) and passively (without rubbing motion). Materials and Methods: A total of 144 bovine dentin samples were used, and the universal adhesive, Clearfil Universal Bond Quick, was either applied in accordance with the manufacturer’s instructions (passive application) or applied with rubbing motion for 10 s (active application). These 2 groups were divided into 6 subgroups according to saliva contamination (n = 12): 1. control: etch-and-rinse (no saliva); 2. control: self-etch (no saliva); 3. etching/saliva/bonding; 4. etching/bonding/saliva; 5. saliva/bonding; 6. bonding/saliva. A resin composite, Filtek Ultimate, was filled into a polyethylene mold (0.9 mm diameter, 1.2 mm height) on the surfaces. Samples were subjected to microshear bond strength testing, and five specimens from each group were examined using SEM. Resin-dentin interfaces were also observed using transmission electron microscopy (TEM). All failure modes were determined using light microscopy. Statistical analyses were performed with two-way ANOVA, the Kruskall-Wallis test, and the Mann-Whitney U-test (p < 0.05). Results: Active-application groups showed statistically significantly higher bond strengths than did passive groups, regardless of adhesive strategy and saliva contamination (p < 0.05). Application of Clearfil Universal Bond Quick in self-etch mode with rubbing motion improved the µSBS among control groups (p < 0.05). The active application did not make a significant difference among the active groups (p > 0.05), except in group 2. Groups 2 and 5 showed significantly higher µSBS than group 3 among the passive groups (p < 0.05). Conclusion: Rubbing the universal adhesives without any prior etching may increase the dentin bond strength. Following etching, passive application of the universal adhesive (without any additional rubbing motion) could affect the bonding to dentin in the presence of saliva. Keywords: universal adhesive, saliva contamination, rubbing motion, etch-and-rinse, self-etch

Purpose: To investigate the fatigue performance and stress distribution of endodontically treated maxillary premolars with occlusal (O), mesio-occlusal (MO), or mesio-occluso-distal (MOD) cavities filled directly with bulk-fill composite.Materials and Methods: Besides the intact teeth (control group), sixty sound maxillary first premolars, standardized by size and morphology, were subjected to root canal treatment and randomly allocated to three groups throughout cavity preparations (O/MO/MOD). All cavities were restored with a bulk-fill composite (Tetric N-Ceram Bulk fill) and universal adhesive (Tetric N-Bond Universal) using etch-and-rinse mode. Half of the specimens of each group underwent 20,000 thermocycles (5°C–55°C). All specimens were subjected to a 50-N load perpendicular to their buccal bevels on the palatal cusps for 1,200,000 cycles. The survival curve and fracture mode were analyzed by log-rank and Fisher’s exact tests, respectively. Finite element analysis (FEA) was conducted to simulate the working condition of premolars with O/MO/MOD cavities. The von Mises stress and the first principal stress were calculated for three FEA models.Results: Premolars with O cavity restorations exhibited better stress distributions than did those with MO and MOD cavity restorations. Compared to the intact premolars, no significant difference was detected in the fatigue performance of O/MO/MOD restorations, regardless of whether they underwent thermocycling. Only one specimen presented unrestorable fracture, while the rest of the fractured premolars were restorable. Conclusion: The cavity design of endodontic premolars restored with a bulk-fill composite has no influence on the stress distribution or fatigue survival, with a biomechanical performance similar to that of an intact tooth. Keywords: maxillary premolar, endodontical treatment, bulk-fill composite, fatigue performance, finite element analysis.