Variability of shear and microtensile bond strength tests to enamel and dentin

Abstract

Purpose: This study aimed to provide guidelines about the coefficient of variation (CV) of shear (SBS) and microtensile (μTBS) bond strength to enamel and dentin. Methods: A search of the English language peer-reviewed literature was conducted using the PubMed database from 2000 to 2009. Only bond strength studies (SBS and μTBS) that have tested both enamel and dentin substrates were selected. The following information was gathered from the 103 papers selected: groups mean and standard deviation (SD), repetition number, and type of statistical analysis. The CV of each study was calculated by using its mean and SD values, the normality of shear and microtensile CV was analyzed using Shapiro-Wilk test, and a CV classification was established for each variable. Results: According to the CV classification proposed, values below 10.3% and 11.3% could be considered low for shear bond strength to enamel and dentin, respectively; and values below 15.4% to enamel and 16.4% to dentin could be considered low for the microtensile test. Values higher than 46.8% and 62.1% (shear bond strength to enamel and dentin) and 45.9% and 45.5% (microtensile bond strength to enamel and dentin) showed a very high variability. Conclusion: Such classification can be useful for future experiments on adhesive materials to estimate statistical power and data precision.