Bonding Protocols to Reverse the Bond Strength of a Universal Adhesive to Hemostatic Agent-contaminated Dentin.

OBJECTIVE: To evaluate the effect of different bonding protocols on the microtensile bond strength (µTBS) of a universal adhesive to dentin contaminated with a hemostatic agent. METHODS AND MATERIALS: Ninety-five extracted premolars were used in this study. For the µTBS test, 80 teeth were cut to expose mid-coronal dentin and randomly divided into two groups (uncontaminated dentin and hemostatic agent-contaminated dentin). Each group was further divided into five subgroups (n=8/group): 1) SE: no additional treatment, 2) ER: etching with 32% phosphoric acid, 3) CHX: rinsing with 0.2% chlorhexidine, 4) EDTA: rinsing with 17% EDTA, and 5) T40: application of universal adhesive for 40 seconds. A universal adhesive was applied followed by resin composite build-up. µTBS test was performed after 24 hours of water storage. Two-way analysis of variance (ANOVA) was calculated followed by the Duncan testing (α=0.05). The failure mode was analyzed using light microscopy. Additional teeth were prepared for energy-dispersive X-ray (EDX) analysis (n=1/group) and resin-dentin interface observation (n=2/group) using scanning electron microscopy. RESULTS: Adverse effects of hemostatic agent contamination on the bonding performance of a universal adhesive was found in the SE, CHX, and T40 groups (p<0.05). Fewer and shorter resin tags were observed in the SE, CHX, and T40 groups. A higher percentage of adhesive failure and mixed failure was found in contaminated dentin. All bonding protocols revealed lower amounts of Al and Cl after dentin contamination, except for the SE group. CONCLUSIONS: Hemostatic agent contamination adversely affected dentin bond strength. However, this bond strength could be reversed using the etch-and-rinse technique or rinsing with EDTA prior to adhesive application.

Does Shortened Application Time Affect Long-Term Bond Strength of Universal Adhesives to Dentin?

OBJECTIVE: This study evaluated the effect of shortened application time on long-term bond strength with universal adhesives. METHODS AND MATERIALS: Three universal adhesives were used: Clearfil Universal Bond (CU, Kuraray Noritake Dental Inc, Tokyo, Japan), Scotchbond Universal Adhesive (SB, 3M ESPE, St Paul, MN, USA) or G-Premio Bond (GP, GC Corp, Tokyo, Japan). Sixty molars were cut to expose midcoronal dentin and prepared with a regular diamond bur. Each adhesive was applied either according to the manufacturer's instruction or with shortened time. Specimens were stored in distilled water at 37°C for 24 hours and then cut into resin-dentin sticks. Microtensile bond strength (µTBS) was tested after either 24 hours or 1 year of water storage. Data were analyzed by the three-way ANOVA and Duncan tests ( α=0.05). Fracture modes were analyzed under a scanning electron microscope (SEM). One dentin stick per group was selected after fracture mode analysis and further observed using transmission electron microscopy (TEM). Six additional dentin discs were prepared and conditioned with each adhesive under the different application time to observe the adhesive-smear layer interaction by SEM. RESULTS: Shortened application time affected the µTBS ( p<0.001) while storage time did not affect bond strength ( p=0.187). A significant effect of shortened application time on µTBS was observed in the CU at 1 year and in the GP at both storage times. CONCLUSIONS: One-year storage time had no effect on the µTBS of universal adhesives to bur-cut dentin. The performance of universal adhesives can be compromised when applied using a shortened application time.