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This study evaluated the effects of blood contamination and decontamination methods during different steps of bonding procedures on the microtensile bond strength of two-step self-etch adhesives to dentin. Sixty extracted human molars were ground flat to expose occlusal dentin. The 60 molars were randomly assigned to three groups, each treated with a different two-step self-etch adhesive: Clearfil SE Bond, AdheSE and Tyrian SPE. In turn, these groups were subdivided into five subgroups (n = 20), each treated using different experimental conditions as follows: control group-no contamination; contamination group 1-CG1: primer application/ contamination/primer re-application; contamination group 2-CG2: primer application/contamination/wash/dry/primer re-application; contamination group 3-CG3: primer application/adhesive application/light curing/contamination/ adhesive re-application/light curing; contamina- tion group 4-CG4: primer application/adhesive application/light curing/contamination/wash/ dry/adhesive re-application/light curing. Composite buildup was performed using Z250. After 24 hours of storage in distilled water at 37 degrees C, the bonded specimens were trimmed to an hourglass shape and serially sectioned into slabs with 0.6 mm2 cross-sectional areas. Microtensile bond strengths (MTBS) were assessed for each specimen using a universal testing machine. The data were analyzed by two-way ANOVA followed by a post hoc LSD test. SEM evaluations of the fracture modes were also performed. The contaminated specimens showed lower bond strengths than specimens in the control group (p < 0.05), with the exception of CG1 in the Clearfil SE group and CG2 and CG3 in the Tyrian SPE group. Among the three self-etch adhesives, the Tyrian SPE group exhibited a significantly lower average MTBS compared to the Clearfil SE Bond and AdheSE (p < 0.05) groups. Based on the results of the current study, it was found that blood contamination reduced the MTBS of all three self-etch adhesives to dentin, and water-rinsing was unable to overcome the effects of blood contamination.
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PMID:Effects of blood contamination on microtensile bond strength to dentin of three self-etch adhesives. 2053 34

Optimization of mechanical properties is required in applications of tissue-engineered scaffolds. In this study, a polyelectrolyte complexation approach is proposed to improve the mechanical properties of the nanofibrous scaffolds. Through an electrospun chitosan/gelatin (CG) model system, it is demonstrated that the storage modulus of CG nanofiber-based complex membranes is over 10(3)-fold higher than that of neat chitosan or gelatin membranes. Further, an annealing process was found to promote the conjugation of the oppositely charged polymers and thus the tensile modulus of CG membranes is 1.9-fold elevated. When the molar ratio of aminoglucoside units in chitosan to carboxyl units in gelatin is 1:1, the complex nanofiber-based membranes (CG2) display the highest mechanical strength. In addition, the complex membranes reveal an excellent swelling capacity. By comparing the CG membranes electrospun with cast, it is deduced that the complexation is one of the main contributing factors to the improvement in mechanical properties. FTIR and DSC analyses confirm that more molecular interactions took place in the complexation. SEM observation clearly displays the electrospinnability of the complex. Therefore, polyelectrolyte complexation is an effective strategy for enhancing mechanical properties of nanofibrous scaffolds. These mechanically enhanced chitosan/gelatin nanofibrous membranes have wider applications than wound dressing.
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PMID:Mechanical enhancement of nanofibrous scaffolds through polyelectrolyte complexation. 2323 52