Effect of Light Source Intensity on Shear Bond Strength

Objectives: The aim of this study was to evaluate the effect of light source intensity on shear bond strength of two different bonding systems. Methods: Flat occlusal dentin surfaces were created on 240 extracted human molar teeth 2 mm above the dentino-enamel junction. The teeth were first randomly divided into two groups and then divided into eight subgroups (n=15). The bonding agents (Clearfil SE Bond (CSE)-Kuraray and Single Bond (SB)-3M ESPE) were applied on the flat dentinal surfaces according to the manufacturer's instructions and composite resins(Clearfil APX–Kuraray and 3M Filtek Z250) were applied to the surfaces in standart cylindirical shaped plastic matrixes (2 mm in diameter and 2mm in height) respectively. Light curing was applied using different light intensities, between 100 and 900 mW/cm2 by different light sources. Shear bond testing was applied by using a stubby-shaped apparatus (Ultradent, USA) at a crosshead speed of 1,5 mm/min to each specimen. The bond strengths were calculated and converted into MPa. Results: In all groups, CSE showed higher bond strength values than SB except for the group, light source of 200 mW/cm2 intensity was used. In CSE groups there was no significant difference between shear bond strength values 100 mW/cm2 (71,35± 24,08) and 200 mW/cm2 (70,53±27,37) light intensity. The bond strength values were significantly lower than that of other light source intensities. When the groups of SB compared, while the lowest shear bond strength values (46,35±18,56) were obtained with the light source of 100 mW/cm2 intensity, the highest values (99,32±23,36) belonged to the light source of 300 mW/cm2 intensity. Conclusion: Light intensity over 200 mW/cm2 was not dramatically affected the bond strength of self-etch system CSE.