Low Stress Thiol-ene Based Resin Nanohybrid Composite Physical Properties

Experimental low stress, nanohybrid composites were prepared using different methacrylate-thiol-ene resin systems designed at the University of Colorado, Boulder, USA. Thiol-ene polymerizations are step growth reactions, leading to a low volumetric shrinkage and shrinkage stress. These properties make Thiol-enes an alternative for dental applications.

Objectives: To determine the Physical Properties of experimental Methacrylate-Thiol-ene based composites compared to Bis-GMA based resin (Filtek Supreme Plus, 3M-ESPE) and dimer acid based resin (N'Durance^®, Septodont) nanohybrid composites.

Methods: Compressive and flexural strength, flexural modulus, water sorption and solubility were determined according to the International Standard ISO 4049 and ADA specification 27. Diametral Tensile Strength (DTS) was measured using a similar test method as compressive strength. Monomer conversion was calculated by near-IR. The polymerization shrinkage was measured using a linometer from ACTA. Shrinkage stress was measured with an ADAHF Tensometer. Wear resistance was measured using the ACTA machine. Specimens were polymerized using a quartz-tungsten-halogen lamp with an intensity of 500 mW/cm², during 40 or 20 seconds according to the test.

Results:

Conclusions: The thiol-ene based monomer system contributes to reducing the stress at the bonding interface with the tooth, while maintaining a high intrinsic strength. Further research is necessary in order to lower the volumetric shrinkage. This decrease should lead to an additional decrease in shrinkage stress.