Investigation of thiol-ene and thiol-ene–methacrylate based resins as dental restorative materials

Abstract

Objectives-The objective of this work was to evaluate thiol-norbornene and thiol-enemethacrylate systems as the resin phase of dental restorative materials and demonstrate their superior performance as compared to dimethacrylate materials.Methods-Polymerization kinetics and overall functional group conversions were determined by Fourier transform infrared spectroscopy (FTIR). Flexural strength and modulus were determined with a 3-point flexural test. Polymerization-induced shrinkage stress was measured with a tensometer.Results-Thiol-ene polymer systems were demonstrated to exhibit advantageous properties for dental restorative materials in regards to rapid curing kinetics, high conversion, and low shrinkage and stress. However, both the thiol-norbornene and thiol-allyl ether systems studied here exhibit significant reductions in flexural strength and modulus relative to BisGMA/TEGDMA. By utilizing the thiol-ene component as the reactive diluent in dimethacrylate systems, high flexural modulus and strength are achieved while dramatically reducing the polymerization shrinkage stress. The methacrylate-thiol-allyl ether and methacrylate-thiol-norbornene systems both exhibited equivalent flexural modulus (2.1 ± 0.1 GPa) and slightly reduced flexural strength (95 ± 1 and 101 ± 3 MPa, respectively) relative to BisGMA/TEGDMA (flexural modulus; 2.2 + 0.1 GPa and flexural strength; 112 ± 3 MPa). Both the methacrylate-thiol-allyl ether and methacrylate-thiol-norbornene systems exhibited dramatic reductions in shrinkage stress (1.1 ± 0.1 and 1.1 ± 0.2 MPa, respectively) relative to BisGMA/TEGDMA (2.6 ± 0.2 MPa).Significance-The improved polymerization kinetics and overall functional group conversion, coupled with reductions in shrinkage stress while maintaining equivalent flexural modulus, result in a superior overall dental restorative material as compared to traditional bulk dimethacrylate resins.

Optimizing the concentration of 2,4,6-trimethylbenzoyldiphenylphosphine oxide initiator in composite resins in relation to monomer conversion

“…Wet polishing was applied since it has been shown to have no effect on DC values 20) . Micro-Raman analysis was done within 10 min post-polymerization since studies on polymerization kinetics of various resin models and RBCs have shown a plateau in conversion within minutes of the start of polymerization [21][22][23] . The present results have shown a logarithmic relationship between the amount of Lucirin ® TPO and the resultant DC for both unfilled and filled resins.…”

Polymerization shrinkage stress of composite resins and resin cements – What do we need to know?

“…82 The mechanism for stress reduction relies on the fact that thiol-ene polymerizations progress via step-growth, a process in which gelation and vitrification are not reached until much later in conversion, so any strain can be accommodated before it generates stresses at the interface. 83,84 There are some disadvantages of using thiol-enes, such as a potential for decreased modulus in methacrylate polymerizations, and malodor of small molecule thiols. This can be circumvented by either decreasing the concentration of thiols in methacrylate polymerizations 85 or by tethering thiol functionalities into pre-polymerized particles.…”

Characterization of an experimental resin composite organic matrix based on a tri-functional methacrylate monomer

“…Since the development of the resin composites by Rafael BOWEN in the late 1950s, many efforts have been made to improve the behavior of this class of restorative materials [1][2][3] . In general, resin composites comprise three phases: a organic matrix formed by a mix of bi-functional methacrylate monomers, inorganic filler particles and a silane-coupling agent that chemically bonds the organic matrix to the filler particles.…”