Effects of composite thickness on shear bond strength to dentin

Abstract

Sixty non-carious extracted human molars were used in this study. The enamel
on the occlusal surface ofthe crown of the tooth was removed by a diamond bur then
the surfaces of the teeth were ground flat. The teeth were randomly divided into six
groups each of ten and stored in distilled water at 370 C. Two types of composite were
used in this study, Definite and Tetric. The bonding agents Etch and Prime were
prepared according to manufacturers directions and applied to the dentin surface on
the first three groups and light cured for 20 seconds. The composite Definite was
packed into either 2, 3, and 4mm thick using split metal mould in the first, second
and third groups respectively and bulk-cured from top of the composite for 40
seconds, the same procedure was repeated in the remaining three groups but the
composite used was Tetric which its corssponding bonding agent was Excite. The
bond strength was measured with universal compression machine.The results showed `
that there was no significant difference between the two types of composite Tetric and
Definite used in this study. The shear bond strength was affected by the composite
thickness, the 2 mm increment showed higher bond strength than the 3mm and 4mm
increment in both composites