Micromorphology of Resin/Dentin Interfaces Using 4th and 5th Generation Dual-curing Adhesive/Cement Systems: A Confocal Laser Scanning Microscope Analysis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Purpose: This study evaluated the differential composition of resin/dentin interfaces of indirect restorations created by the application of 4th and 5th generation dual-curing luting systems (bonding agents/resin cements), when each material was either light cured or allowed to self-cure. Materials and Methods: Occlusal flat dentin surfaces of 60 human third molars were assigned into 12 groups (n = 5) according to curing mode and dual-curing cementing system: 4th generation All Bond2 (AB2)/Duolink (Bisco) and 5th generation (B1) Bond1/Lute-it (Pentron). Fluorescein-labeled dextran (FDx) was mixed with the bonding agents, while rhodamine-labeled dextran (RhDx) was incorporated into resin cements and Pre-Bond resin from AB2. Resin cements were applied to 2-mm-thick, precured resin composite disks (Z250, 3M ESPE), which were fixed to dentin surfaces containing adhesive resin in either cured (light cured; LC) or uncured (self-cured; SC) states. The restored teeth were light activated (XL3000, 3M ESPE) according to the manufacturers' instructions (LRC) or allowed to self-cure (SRC), were stored for 24 h, and then vertically, serially sectioned into 1-mm-thick slabs, which were analyzed using confocal laser scanning microscopy. Fluorescent additives indicated where individual components of the bonding/cement systems were located. Additional specimens were prepared and analyzed using a conventional scanning electron microscope. Results: AB2/LC and B1/LC exhibited nonuniform primer/adhesive layer thickness. AB2/SC showed adhesive resin penetration within the primed dentin, and resin cement penetration at the entrance of the dentin tubules. B1/SC/LRC demonstrated resin cement penetration within the hybrid layer and into the dentin tubules. More resin cement penetration was observed in B1/SC/SRC groups than in its LRC equivalent. Conclusion: The morphological features and component interactions among materials at resin/dentin interfaces are related to the activation modes of the primer/adhesive layer and of the resin cement used.1111526Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Medical College of Georgia School of Dentistry, Augusta, GA, USAFundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)FAPESP [03/03645-0]CAPES [BEX 0184/05-5

Effect of pre-heated dual-cured resin cements on the bond strength of indirect restorations to dentin

This study evaluated the effects of resin luting agents (LA) polymerized using increased temperature on the in vitro microtensile bond strength (mu TBS) of indirect restorations to dentin. The occlusal dentin surfaces of 40 human third molars were exposed and flattened. The teeth were assigned to 8 groups (n = 5) according to the LA temperature (25 degrees C or 50 degrees C), curing mode (dual- or self-curing mode), and product (Excite DSC/Variolink II [VII] and XP Bond/Calibra [Cal]). The bonding agents were applied to the dentin surfaces according to manufacturers' instructions. For preheated groups, the LAs were heated to 50 degrees C, subsequently mixed on a heated stirrer surface, and applied to the previously heated pre-polymerized resin discs (2 mm thickness, TPH-Spectrum). The discs were bonded to the dentin surfaces, and the LAs were either exposed to a curing light according to manufacturers' instructions or allowed to self-cure. Specimens were stored in relative humidity at 37 degrees C for 7 days. Specimens were mesio-distally and bucco-lingually sectioned to obtain multiple bonded beams with a 1-mm(2) cross-sectional area for mu TBS testing. Data (MPa) were analyzed by 2-way ANOVA and Tukey's post hoc test (alpha = 5%) for each product. Specimen failure patterns were analyzed using a scanning electron microscope. VII groups showed higher mu TBS at 50 degrees C than at 25 degrees C regardless of curing mode (p = 0.05). Cal groups showed similar mu TBS at 25 degrees C and 50 degrees C in all activation modes. The use of some dual-polymerizing LAs at 50 degrees C may improve the mu TBS of indirect restorations to dentin.26217017

Effects of a Peripheral Enamel Margin on the Long-term Bond Strength and Nanoleakage of Composite/Dentin Interfaces Produced by Self-adhesive and Conventional Resin Cements

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Purpose: This study evaluated the effects of peripheral enamel margins on the long-term bond strength (mu TBS) and nanoleakage in resin/dentin interfaces produced by self-adhesive and conventional resin cements. Materials and Methods: Five self-adhesive [RelyX-Unicem (UN), RelyX-U100 (UC), GCem (GC), Maxcem (MC), Set (SET)] and 2 conventional resin cements [RelyX-ARC(RX), Panavia F(PF)] were used. An additional group included the use of a two-step self-etching adhesive (SE Bond) with Panavia F (PS). One hundred ninety-two molars were assigned to 8 groups according to luting material. Five-mm-thick composite disks were cemented and assigned to 3 subgroups according to water-exposure condition (n = 6): 24-h peripheral exposure (24h-PE-enamel margins), or 1 year of peripheral (1yr-PE) or direct exposure (1yr-DE-dentin margin). Restored teeth were sectioned into beams and tested in tension at 1 mm/min. Data were analyzed by two-way ANOVA and Tukey's test. Two additional specimens in each group were prepared for nanoleakage evaluation. Nanoleakage patterns were observed under SEM/TEM. Results: Except for RX, no significant reduction in mu TBS was observed between 24h-PE and 1yr-PE. 1yr-DE reduced mu TBS for RX, PF, GC, MC, and SET. No significant reduction in mu TBS was observed for PS, UC, and UN after 1 year. After 1yr-DE, RX and PS presented the highest mu TBS, and SET and MC the lowest. Nanoleakage was reduced when there was a peripheral enamel margin. SET and MC presented more silver deposition than other groups. Conclusion: The presence of a peripheral enamel margin reduced the degradation rate in resin/dentin interfaces for most materials. The mu TBS values produced by the multi-step luting agents RX and PS were significantly higher than those observed for self-adhesive cement143251263Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [2007/06083-4, 2007/06447-6

Effect of propolis gel on the in vitro reduction of dentin permeability

OBJECTIVE: The aim of this study was to evaluate the capacity of potassium oxalate, fluoride gel and two kinds of propolis gel to reduce the hydraulic conductance of dentin, in vitro. MATERIAL AND METHODS: The methodology used for the measurement of hydraulic conductance of dentin in the present study was based on a model proposed in literature. Thirty-six 1-mm-thick dentin discs, obtained from extracted human third molars were divided into 4 groups (n=9). The groups corresponded to the following experimental materials: GI-10% propolis gel, pH 4.1; GII-30% propolis gel; GIII-3% potassium oxalate gel, pH 4,1; and GIV-1.23% fluoride gel, pH 4.1, applied to the dentin under the following surface conditions: after 37% phosphoric acid and before 6% citric acid application. The occluding capacity of the dentin tubules was evaluated using scanning electron microscopy (SEM) at ×500, ×1,000 and ×2,000 magnifications. Data were analyzed statistically by two-way ANOVA and Tukey's test at 5% significance level. RESULTS: Groups I, II, III, IV did not differ significantly from the others in any conditions by reducing in hydraulic conductance. The active agents reduced dentin permeability; however they produced the smallest reduction in hydraulic conductance when compared to the presence of smear layer (P<0.05). The effectiveness in reducing dentin permeability did not differ significantly from 10% or 30% propolis gels. SEM micrographs revealed that dentin tubules were partially occluded after treatment with propolis. CONCLUSIONS: Under the conditions of this study, the application of 10% and 30% propolis gels did not seem to reduce the hydraulic conductance of dentin in vitro, but it showed capacity of partially obliterating the dentin tubules. Propolis is used in the treatment of different oral problems without causing significant great collateral effects, and can be a good option in the treatment of patients with dentin sensitivity

Influence of light-activated and auto- and dual-polymerizing adhesive systems on bond strength of indirect composite resin to dentin

Statement of problem. Clinicians must be aware of the bonding effectiveness of auto- and dual-polymerizing adhesive systems before choosing the material and technique of cementing inlay/onlays to dentin. An inadequate choice may compromise the success of indirect restorations. Purpose. This study compared the microtensile bond strength (MTBS) of indirect composite resin bonded to dentin by light-activated, autopolymerizing, and dual-polymerizing adhesive systems. Material and methods. Occlusal dentin surfaces of 36 human third molars were exposed and flattened. Teeth were assigned to 1 of the following 6 groups (n=6) of adhesive luting systems: 2 dual-polymerizing systems (Scotchbond Multipurpose Plus/Rely X [SBMP] and Prime & Bond NT Dual Cure/Enforce [PBDC]); 1 autopolymerizing system (ED Primer/Panavia F [EDP]); and 3 light-activated systems (control groups) (Adper Single Bond/Rely X [SB], Prime & Bond NT/Enforce [PB], and Clearfil SE Bond/Panavia F [CF]). The restorative materials were applied according to manufacturer's directions. A 2-mm-thick prepolymerized composite resin (Clearfil APX) disc was cemented with the resin cements on the bonded dentin. Teeth were stored in water at 37 degrees C for 24 hours. Afterwards, teeth were sectioned both mesial-distally and buccal-lingually to obtain multiple bonded beam specimens with 0.8 turn 2 of cross-sectional area. Each specimen was tested in tension at a crosshead speed of 0.5 mm/min until failure. Data (MPa) were analyzed by 1-way analysis of variance and the Tukey post hoc test (alpha=.05). Failure patterns of tested specimens were analyzed using scanning electron microscopy. Results. Mean MTBS values (MPa) for experimental groups were as follows: SBMP, 32.89 +/- 3.26(a); SB, 26.74 +/- 7.45(ab); PB, 26.11 +/- 4.48(ab); CF, 25.30 +/- 6.42(ab); EDP, 16.82 +/- 5.53(bc); PBDC, 11.20 +/- 5.89(c) (P<.001). Groups with similar lowercase letters were not significantly different. Failure pattern of fractured specimens varied according to the polymerization mode. Conclusion. The autopolymerizing system and one of the dual-polymerizing systems were as effective as the light-activated systems in bonding indirect composite restorations to dentin.96211512

High-concentrated carbamide peroxide bleaching agents effects on enamel surface

Concern has been expressed regarding the adverse effects of peroxide-containing tooth bleaching agents on enamel surface. This study examined enamel average surface roughness before (baseline) and after an in-office bleaching protocol and investigated the influence of high concentrations of carbamide peroxide gels on its surface staining and morphology. Flat enamel surfaces were submitted to 35 and 37% carbamide peroxide or to no bleaching treatment (n = 10) and evaluated with a profilometer. Eight specimens from each group were randomly selected and immersed in a 2% methylene blue solution. Afterwards, specimens were ground into powder and prepared for the spectrophotometric analysis. Two remained specimens of each group were examined using a scanning electron microscope. Data were subjected to analysis of variance and Tukey test (P > 0.05). Baseline roughness average was statistically similar for all groups, however, 35% carbamide peroxide produced the roughest enamel surfaces. Different concentrations of carbamide peroxide produced similar staining means and enamel surface morphological alterations.31215515

Effects of additional and extended acid etching on bonding to caries-affected dentine

This study evaluated the effects of additional and extended acid etching on microtensile bond strength (muTBS) of two adhesive systems to sound (SD) and caries-affected dentine (CAD). Flat surfaces of CAD surrounded by SD of 36 extracted carious third molars were assigned to four treatments (i): self-etching adhesive system (Clearfil SE Bond) applied to dentine surfaces following manufacturer's instructions (MI); (ii) after additional etching for 15 s (35% phosphoric acid, PA); (iii) total-etch one-bottle adhesive (Single Bond) applied to dentine surfaces following MI; or (iv), after etching for 45 s with PA. Composite 'blocks' were built on bonded surfaces and restored teeth were vertically sectioned to obtain bonded slices of 0.7 mm thick. Slices were trimmed to create hourglass-shaped specimens (cross-sectional area of 1 mm(2)), which were tested under tension in a universal testing machine. Additional CAD and SD samples were prepared for scanning electron microscopy observations. Additional and extended etching significantly increased muTBS to CAD; however, muTBS of both adhesives to CAD were significantly lower than to SD. Additional and extended etching can improve bonding to CAD; however, adhesives applied on SD showed the best results for bonding.112545846