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Two-year composite/dentin bond stability.

PURPOSE
To examine the composite-to-dentin shear bond strengths over 2 yrs of three chemically different single bottle dentin adhesives: water-based Syntac Single Component (SSC); acetone-based Prime & Bond 2.1 (PB), and; ethanol-based and filled OptiBond Solo (OS).


MATERIALS AND METHODS
Extracted human molars stored in 0.2% sodium azide were randomly assigned to each of three dentin bond groups for testing at 5 time periods (n=15). The crowns of the teeth were sectioned to expose occlusal dentin and the roots embedded in acrylic. The dentin was etched with 37% H3PO4 for 20 s, rinsed and dentin adhesives applied per manufacturers' instructions. A column of Z-100 composite was bonded to the treated dentin surface and light cured. Teeth were stored in distilled water at 37 degrees C and thermocycled for 1,000 cycles between 5 degrees C and 55 degrees C and tested in shear at 24 hrs (baseline), 6, 12, 18 and 24 months. Mean +/- SD shear bond strengths (SBS) were determined.


RESULTS
ANOVA at a significance level of P< 0.05 revealed OS had significantly higher SBS at 6 and 12 months compared to baseline. PB had significantly higher SBS at 12 months compared to baseline. SSC had significantly higher SBV at 18 months compared to baseline. However, at 24 months the SBV for OS and SSC were significantly lower than at baseline. During all time periods, OS and PB had significantly higher SBS than SSC.


CLINICAL SIGNIFICANCE
The long-term stability of resin-based composite to dentin bond strengths from single bond adhesives is questionable because after 2 yrs, bond strengths for two of the three tested dentin adhesives, OptiBond Solo and Syntac Single Component, were significantly lower than initial strengths.