Polymerization contraction stress in resin–tooth bonds under hydrated and dehydrated conditions

Abstract 

Objective

This study hypothesizes that, with enamel or dentin as a bonding substrate, intrinsic water affects the development of polymerization contraction stress in the bonds of self-etching adhesives during bonding.

Materials and methods

The influence of the water content in dentin and enamel (wetness with water as control and acetone-dried specimens) on the stress development in self-etching adhesives was determined with a tensilometer. Thin layers of self-etching primer and/or adhesive resins were created between a glass plate and a flat enamel or dentin surface.

Results

After an initial maximum shortly after light curing for 30min, the contraction stress was decreased in the dentin (30–70%) and enamel (approximately 20%). In the acetone-dried specimens, the stress was continuously increased for 20–50%.

Significance

The intrinsic water content of tooth tissue influences the initial polymerization of polymers. This effect is favorable for stress relief in resin restoration but causes unwanted nanoleakage channel formation in resin–tooth bonds.

Keywords: Polymerization, Contraction stress, Self-etching adhesive, Dentin, Enamel, Water, pH