Indirect resin composite restorations bonded to dentin using self-adhesive resin cements applied with an electric current-assisted method.

PURPOSE: To evaluate the effects of an electric current-assisted application on the bond strength and interfacial morphology of self-adhesive resin cements bonded to dentin. METHODS: Indirect resin composite build-ups were luted to prepared dentin surfaces using two self-adhesive resin cements (RelyX Unicem and BisCem) and an ElectroBond device under 0, 20, or 40 µA electrical current. All specimens were submitted to microtensile bond strength test and to interfacial SEM analysis. RESULTS: The electric current-assisted application induced no change (P > 0.05) on the overall bond strength, although RelyX Unicem showed significantly higher bond strength (P < 0.05) than BisCem. Similarly, no differences were observed in terms of interfacial integrity when using the electrical current applicator.

Levels of Pro and Anti-inflammatory Citokynes and C-Reactive Protein in Patients with Chronic Periodontitis Submitted to Nonsurgical Periodontal Treatment

Aim: to compare the levels of IFN-γ, TGF-ß and C-reactive protein (CRP) in healthy patients (HP) and chronic periodontitis patients (CP) before and seven days after the last session of Non-Surgical Periodontal Treatment (NSPT). Materials and Methods: 40 subjects were divided into two groups: healthy (n= 20), and with chronic periodontitis (n = 20). Serum and gingival crevicular fluid (GCF) were collected from each patient and quantified for IFN-γ, TGF-ß and CRP using the enzyme-linked immunosorbent assay (ELISA). Results: IFN-γ was found to be higher in the GCF of the CP group before NSPT in relation to the HP group (p<0.05), and it had significant higher levels after seven days of NSPT (p<0.05). The levels of TGF-ß in the GCF of CP patients before NSPT were significantly higher when compared to HP (p<0.05), but they decreased after seven days of NSPT (p>0.05). Serum CRP levels did not show statistical difference between CP and HP before or after NSPT. Conclusion: Therefore, our results demonstrated for the first time that NSPT causes early exacerbation of the immune response at the local level represented by increased levels of IFN-γ and decreased levels of TGF-ß in the gingival crevicular fluid after seven days of treatment.

Collagen cross-linkers on dentin bonding: Stability of the adhesive interfaces, degree of conversion of the adhesive, cytotoxicity and in situ MMP inhibition.

OBJECTIVE: To investigate the effect of collagen cross-links on the stability of adhesive properties, the degree of conversion within the hybrid layer, cytotoxicity and the inhibition potential of the MMPs' activity. METHODS: The dentin surfaces of human molars were acid-etched and treated with primers containing: 6.5wt% proanthocyanidin, UVA-activated 0.1wt% riboflavin, 5wt% glutaraldehyde and distilled water for 60s. Following, dentin was bonded with Adper Single Bond Plus and Tetric N-Bond; and restored with resin composite. The samples were sectioned into resin-dentin "sticks" and tested for microtensile bond strength (µTBS) after immediate (IM) and 18-month (18M) periods. Bonded sticks at each period were used to evaluate nanoleakage and the degree of conversion (DC) under micro-Raman spectroscopy. The enzimatic activity (P1L10 cross-linkers, P1L22 MMPs' activities) in the hybrid layer was evaluated under confocal microscopy. The culture cell (NIH 3T3 fibroblast cell line) and MTT assay were performed to transdentinal cytotoxicity evaluation. Data from all tests were submitted to appropriate statistical analysis (α=0.05). RESULTS: All cross-linking primers reduced the degradation of µTBS compared with the control group after 18M (p>0.05). The DC was not affected (p>0.213). The NL increased after 18M for all experimental groups, except for proanthocyanidin with Single Bond Plus (p>0.05). All of the cross-link agents reduced the MMPs' activity, although this inhibition was more pronounced by PA. The cytotoxicity assay revealed reduced cell viability only for glutaraldehyde (p<0.001). SIGNIFICANCE: Cross-linking primers used in clinically relevant minimized the time degradation of the µTBS without jeopardizing the adhesive polymerization, as well as reduced the collagenolytic activity of MMPs. Glutaraldeyde reduced cell viability significantly and should be avoided for clinical use.

Improving adhesion between luting cement and zirconia-based ceramic with an alternative surface treatment.

This study evaluated the influence of an alternative surface treatment on the microshear bond strength (µsbs) of zirconia-based ceramic. Thirty-five zirconia disks were assigned to five groups according to the following treatments: Control (CO), glass and silane were not applied to the zirconia surface; G1, air blasted with 100µm glass beads + glaze + silane; G2, a gel containing 15% (by weight) glass beads applied to the ceramic surface + glaze + silane; G3, a gel containing 25% (by weight) glass beads applied to the ceramic surface + glaze + silane; and G4, a gel containing 50% (by weight) glass beads applied to the ceramic surface + glaze + silane. The specimens were built up using RelyX ARC®, according to the manufacturer's recommendations, and inserted in an elastomeric mold with an inner diameter of 0.8 mm. The µsbs test was performed using a testing machine at a crosshead speed of 0.5 mm/min. ANOVA and Tukey's test (p < 0.05) were applied to the bond strength values (in MPa). CO (15.6 ± 4.1) showed the lowest µsbs value. There were no statistical differences between the G1 (24.9 ± 7.4), G2 (24.9 ± 2.3), G3 (35.0 ± 10.3) and G4 (35.3 ± 6.0) experimental groups. Those groups submitted to surface treatments with higher concentrations of glass showed a lower frequency of adhesive failures. In conclusion, the glass application improved the interaction between the ceramic and the luting cement.

Improving adhesion between luting cement and zirconia-based ceramic with an alternative surface treatment

This study evaluated the influence of an alternative surface treatment on the microshear bond strength (μsbs) of zirconia-based ceramic. Thirty-five zirconia disks were assigned to five groups according to the following treatments: Control (CO), glass and silane were not applied to the zirconia surface; G1, air blasted with 100μm glass beads + glaze + silane; G2, a gel containing 15% (by weight) glass beads applied to the ceramic surface + glaze + silane; G3, a gel containing 25% (by weight) glass beads applied to the ceramic surface + glaze + silane; and G4, a gel containing 50% (by weight) glass beads applied to the ceramic surface + glaze + silane. The specimens were built up using RelyX ARC®, according to the manufacturer’s recommendations, and inserted in an elastomeric mold with an inner diameter of 0.8 mm. The μsbs test was performed using a testing machine at a crosshead speed of 0.5 mm/min. ANOVA and Tukey’s test (p < 0.05) were applied to the bond strength values (in MPa). CO (15.6 ± 4.1) showed the lowest μsbs value. There were no statistical differences between the G1 (24.9 ± 7.4), G2 (24.9 ± 2.3), G3 (35.0 ± 10.3) and G4 (35.3 ± 6.0) experimental groups. Those groups submitted to surface treatments with higher concentrations of glass showed a lower frequency of adhesive failures. In conclusion, the glass application improved the interaction between the ceramic and the luting cement.

Influence of ceramic primers on microshear bond strength between resin cements and zirconia-based ceramic

This study evaluated the effect of a coupling agent ceramic primer (CP) on the microshear bond strength (ìsbs) between luting cements and zirconia-based ceramic. Methods: Zirconia discs (Cercon) were made and finished with silicon carbide paper and submitted to air abrasion using 50 μm aluminum oxide particles (Al2O3) under 4 bar pressure. Zirconia disks were randomly assigned to four groups (n=10): (G1) ResiCem luting cement + Porcelain Primer, (G2) ResiCemluting cement only, (G3) Clearfil Esthetic Cement + Clearfil Ceramic Primer and (G4) Clearfil Esthetic Cement only. The luting cements were prepared according to manufacturers’ recommendations and inserted in an elastomeric mold positioned onto a zirconia disc. Each specimen was photoactivated by 20 s. The specimens were stored at 100% relative humidity and 37ºC for 24 h. The ìsbs test was performed using universal testing machine at a crosshead speed of 0.5 mm/min. An optical microscope was used to analyze the failure modes and illustrative images were captured with a scanning electron microscope. The ìsbs data were analyzed by two-way ANOVA (p<0.05). Results: No significant difference was found among the four groups G1 (17.4±6.8), G2 (17.1±5.5), G3 (15.6±5.5) and G4 (14.2±3.5), all of which showed 100% of adhesive failures. Conclusions: CP showed no increase in the ìsbs between zirconia-based ceramic and resin luting cements.