The Journal of Adhesive Dentistry, 06/2017

Purpose: To critically appraise the evidence regarding the effect of enamel sandblasting on the bond strength of orthodontic brackets on either the labial or lingual tooth surface. Materials and Methods: An electronic database search of published and unpublished literature was performed. Search terms included sandblasting, enamel abrasion, tooth surface, bond strength, bond failure, and adhesive remnant; data were extracted in standardized piloted forms. Risk of bias was assessed using the Cochrane risk of bias tool, adapted for in vitro studies where necessary. Results: Of the 81 articles initially retrieved, 13 were eligible for inclusion in the systematic review. All of the latter were in vitro studies with unclear risk of bias primarily due to unclear reporting of blinding of outcome assessors. Eight studies assessed the combined effect of enamel sandblasting and etching, while only five evaluated the isolated effect of sandblasting on the buccal enamel surface. In view of the apparently heterogeneous study settings, intervention protocols, specimen preparation and storage sequences, only two studies were deemed eligible for quantitative synthesis. Random effects meta-analysis revealed no evidence to support sandblasting prior to etching over etching alone with regard to shear bond strength of orthodontic brackets bonded in vitro to lingual enamel surfaces of extracted premolars (standardized mean difference: 0.36; 95% CI: -0.21, 0.94; p = 0.22). Conclusions: The findings of the present study cannot support lingual enamel sandblasting prior to etching for augmentation of the bond strength of orthodontic brackets. Keywords: sandblasting, orthodontic bonding, shear bond strength, lingual orthodontics, brackets

Purpose: To evaluate the microtensile bond strength (µTBS) of three adhesives to dentin after 1 week and 6 months in an oral environment. Materials and Methods: Class I cavities were prepared in the third molars of 30 patients and randomized into 3 groups according to the following adhesives: Scotchbond Multi-Purpose (SM), Clearfil Protect Bond (CF), and Scotchbond Universal (UN). These molars were then subdivided into two groups according to the exposure time in the oral environment: one week (1W) and 6 months (6M). After the exposure time, the teeth were extracted, cut into beams, and submitted to the µTBS test. The data were analyzed using the Shapiro-Wilk test and two-way ANOVA followed by Tukey's post-hoc test with a significance level of 5%, and fracture modes were analyzed. Results: The bond strengths in MPa (mean ± SD) were SM-1W: 39.5 ± 7.9; SM-6M: 29.7 ± 1.8; CF-1W: 30.5 ± 1.4; CF-6M: 28.6 ± 4.1; UN-1W: 30.6 ± 3.2; and UN-6M: 26.7 ± 2.0. The SM-1W group exhibited significantly increased µTBS compared with the other groups. After 6 months in the oral environment, a significant reduction of µTBS was only observed for the SM group, whereas similar bond strengths were observed for the other groups. SM-1W exhibited a predominance of mixed fractures, whereas the other groups showed a predominance of adhesive fractures. Conclusions: The adhesives which were applied in the self-etching mode maintained bond strength after six months in the oral environment. A reduction of µTBS was only observed for the three-step etch-and-rinse adhesive. Keywords: dentin bonding agents, tensile strength, dentin, clinical study

Purpose: To investigate the influence of pretreating demineralized enamel with a caries infiltrant on the margin integrity of Class V composite restorations bonded with different adhesives. Materials and Methods: A total of 60 specimens from bovine incisors were demineralized (21 days, acid buffer, pH 4.95) to create artificial enamel lesions, and circular Class V cavities were prepared. Cavities of half of the specimens were treated with either an unfilled etch-and-rinse adhesive (Syntac Classic; Ivoclar Vivadent), a filled etch-and-rinse adhesive (Optibond FL; Kerr), or a self-etch adhesive (iBond Self Etch; Heraeus Kulzer) (n = 10 per group). Demineralized enamel of the other half of the specimens was pretreated with a caries infiltrant (Icon; DMG) prior to adhesive application. All cavities were restored with a nanofilled composite material and thermocycled (5000×, 5°C-55°C). Margin integrity was evaluated using scanning electron microscopy, and the percentage of continuous margin was statistically analyzed (p 0.05). Results: The significantly highest margin integrity was observed for Optibond FL, whether or not demineralized enamel was pretreated with the infiltrant. Pretreatment of demineralized enamel with the infiltrant resulted in a significant increase in margin integrity when the unfilled etch-and-rinse adhesive (Syntac Classic) or the self-etch adhesive (iBond Self Etch) was subsequently applied, but showed no significant improvement in combination with the filled etch-and-rinse adhesive (Optibond FL). Conclusion: Application of a caries infiltrant can improve margin integrity of composite fillings in demineralized enamel when used in combination with the examined self-etch and unfilled adhesives. Keywords: caries infiltrant, margin integrity, demineralized enamel, resin composite

Purpose: The purpose of this in vitro study was twofold: 1. To evaluate the surface conditioning effect of a self-etching ceramic primer on lithium disilicate and zirconia ceramics; (2) to study the bond durability provided by the self-etching ceramic primer after artificial aging compared with conventional ceramic conditioning methods. Materials and Methods: Lithium disilicate blocks (10 × 10 mm, 3.4 mm thick) and zirconia disks (8 mm diameter, 3.4 mm thick) were each divided into two groups. In group 1, the lithium disilicate disks (Li) were etched with hydrofluoric acid (HF), while zirconia (Zr) disks were treated with airborne-particle abrasion, both followed by application of a universal primer for restorative materials (MP; Monobond Plus, Ivoclar Vivadent). In group 2, Li disks were not etched with HF, while Zr disks were treated with airborne-particle abrasion, both followed by a self-etching primer (ME; Monobond Etch & Prime, Ivoclar Vivadent). Surface conditioning effects were evaluated using SEM. The specimens in both groups were bonded to a composite with a luting resin and divided into two subgroups. Subgroup 1 was stored in water (37°C) for 3 days, and subgroup 2 was stored in water for 30 days before undergoing 7500 thermal cycles (5°C to 55°C). Results: The self-etching ceramic primer had a significant effect only on the lithium disilicate surface topography. The mean initial bond strength of ME-Zr was relatively low (24.4 MPa) in comparison with all other material combinations (MP-Li: 34.3 MPa; ME-Li: 33.5 MPa; MP-Zr: 31.1 MPa). After 30 days of water storage and thermocycling, the bond strength decreased significantly in all groups. Conclusion: The self-etching primer provided bond strengths to lithium disilicate ceramic comparable with those of the well-established bonding method using hydrofluoric acid etching and a primer containing silane. To zirconia ceramic, however, it provided statistically significantly lower bond strength than did the established bonding method. Keywords: bonding, self-etching, tensile bond strength, ceramic

Purpose: To compare the enamel bonding performace of two commercial and three experimental two-step self-etch adhesives containing acidic functional monomers with different carbon-spacer length and hydrophilicity. The contact angle was also assessed to evaluate the wettability of each tested material. Materials and Methods: Forty extracted human molars were sectioned into four parts (buccal, lingual, mesial, and distal) and divided into 5 groups, according to the adhesives used: Clearfil SE Bond (CSE), AdheSE (ADSE), 10-MDP (15 mol% 10-methacryloyldecylphosphate), CAP-P (15 mol% caprolactone phosphate), and MTEP (15 mol% methacryloyltetraethylene phosphate). Enamel specimens were bonded with each adhesive and submitted to microshear bond strength (μSBS) testing after 24 h. The adhesives were applied onto additional enamel specimens without light curing to assess contact angle. Then the etching pattern was analyzed using SEM and confocal laser scanning microscopy (CLSM). The μSBS and contact angle data were analyzed by one-way ANOVA and Tukey's test (α = 0.05). Results: 10-MDP showed the highest μSBS of the tested groups (p 0.05), followed by CAP-P and CSE (p 0.05). MTEP and ADSE exhibited the lowest μSBS (p 0.05), but the difference between them was not significant. 10-MDP, CSE, and CAP-P exhibited lower contact angles (p 0.05) than did ADSE and MTEP. The SEM and CLSM analyses showed that 10-MDP and CSE had the most pronounced etching patterns and deepest adhesive penetration. ADSE and MTEP exhibited weak etching ability and adhesive penetration, while CAP-P produced moderate etching and intermediate penetration. Conclusions: The length and hydrophilicity of the functional monomer spacer chain tested in this study influenced the enamel bonding performance. Functional monomers with longer chains and more hydrophobic properties, such as 10-MDP and CAP-P, may interact better with enamel and achieve higher enamel bond strength. Keywords: enamel, self-etching, bonding, functional monomers, wettability

Purpose: To evaluate shear (SBS) and microtensile (µTBS) bond strengths of zirconia cores veneered using different fabrication techniques. Materials and Methods: Seventy-five IPS e.max ZirCAD plates were fabricated and divided into three groups according to the following veneering techniques: layering, pressing, and CAD-on. The specimens of the layering group were veneered with IPS e.max Ceram, and the specimens of the pressing group were veneered with IPS e.max ZirPress. Veneering ceramics in the CAD-on group were milled from IPS e.max CAD, fused with the core by using a glass-fusion ceramic, and then crystallized. Bond strength tests were performed using a universal testing machine at a crosshead speed of 0.5 mm/min for the SBS test and 1 mm/min for the µTBS test. Mean SBS and µTBS (MPa) were analyzed with one-way ANOVA and Tukey's HSD test (p 0.05). Results: Significant differences in SBS were observed between the groups (p 0.05). The mean SBS for the CAD-on group was significantly higher (31.89 ± 5.83 MPa) than those of the layering (14.27 ± 4.45 MPa) and pressing (12.23 ± 3.04 MPa) groups. However, the mean µTBS of the CAD-on (30.41 ± 8.64 MPa), layering (21.71 ± 3.40 MPa) and pressing (20.74 ± 6.36 MPa) groups were not statistically significant (p > 0.05). Conclusion: The CAD-on technique showed the highest shear bond strengths of the tested groups, and most of the specimens failed cohesively instead of failing at the adhesive interface. Keywords: zirconia, veneering techniques, CAD-on, all-ceramics, bond strength

Purpose: To evaluate the effect of sodium fluoride and chlorhexidine digluconate on the composite-dentin bond strength of a self-etch adhesive after thermocycling. Materials and Methods: Eighteen human third molars were prepared to expose a flat dentin surface and were divided into 3 groups (n = 6) according to the 3 cavity cleaning solutions: distilled water, 2% chlorhexidine digluconate (CHX), or 1.23% sodium fluoride (NaF). Solutions were rubbed onto dentin surfaces for 60 s, followed by bonding with Clearfil SE Bond, and a 5-mm-thick composite crown buildup. Bonded teeth were stored in distilled water for 24 h and then longitudinally sectioned to obtain bonded sticks. Half of the specimens were immediately tested in tension at 0.5 mm/min, while the remaining specimens were tested after 60,000 thermal cycles. Data were analyzed using two-way ANOVA and the Holm-Sidak method. Results: There was no significant difference between the groups after 24 h (p > 0.05). Thermocycling resulted in significant bond strength reduction for distilled water and CHX (p 0.05). When 24 h bond strengths were compared to the thermocycling group, NaF maintained its bond strength (p > 0.05), while significant reductions were observed for distilled water and CHX (p 0.05). Conclusions: Pretreatment with NaF maintained the bond strength of Clearfil SE Bond to dentin after 60,000 thermal cycles, but pretreatment with CHX did not. Keywords: dentin-bonding agents, sodium fluoride, self-etch adhesive, dentin bond strength

Purpose: To characterize the surface of glass fiber posts (GFP) after different surface treatments and evaluate which method incorporates higher amounts of silicon (Si) particles, as well as to evaluate the bond strength at the post/composite-cement interface with four different surface treatments of glass fiber posts luted with composite cement. Materials and Methods: Twelve glass fiber posts were obtained from the manufacturer. The posts were randomly distributed into four groups (n = 3): Co (control), no surface treatment; S, 70% alcohol and silane (60 s); HF + S, 10% hydrofluoric acid gel (60 s) and silane (60 s); NTP, nonthermal plasma of hexamethyldisiloxane (HMDSO) associated with argon (30 min). The surface of each GFP was characterized through scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Forty GFPs were randomly divided into 4 groups according the surface treatments (n = 10) and cemented with one composite cement (Rely X U200) into artificial canine teeth. The specimens were placed in a universal testing machine and subjected to tensile testing until failure occurred. Statistical analysis of the atomic percentage and bond strength was performed using ANOVA, followed by the post-hoc Tukey test (p = 0.05). Results: EDS graphics showed that the NTP group had a higher Si atomic percentage (at%) than the other groups (p 0.001). The HF + S group had a higher Si at% than did the Co and S groups. SEM images illustrated that the surfaces of the GFPs were variously modified after different treatments. The NTP group incorporated higher Si levels on the GFP surface and yielded the highest bond strengths (p 0.005) compared to the other tested groups. Conclusion: Treatment with HMDSO + Ar plasma (NTP) incorporated higher Si levels on the surface of the GFPs without inducing critical defects. NTP treatment promoted better bond strength results when compared to the other tested group when GFPs were cemented with composite cement. Keywords: plasma gas, silanes, dental prosthesis