Effect of physical properties of direct bonding adhesives on bonding to etched enamel

Five types of light-cured direct bonding adhesives with different volumes of microfiller were prepared for study of the relationships between bond strength to enamel, resinous tag length, and flexural strength, and between viscosity and resinous tag length. The resinous tag length was measured with the combination of 2,4,6-trichlorophenoxy methacrylate as a tracer and electron-probe microanalyzer. Correlating resinous tag length versus viscosity or bond strength after 1-day immersion, and flexural strength with bond strength after 1-day and 30-day immersion resulted in high correlation coefficients. However, the bond strength after thermocycling did not correlate with resinous tag length or flexural strength.