Enhancing Toughness and Reducing Volumetric Shrinkage for Bis-GMA/TEGDMA Resin Systems by Using Hyperbranched Thiol Oligomer HMDI-6SH.

Biao Yu,Sufyan Garoushi,Jingwei He,Lippo Lassila,Pekka K. Vallittu

doi:10.3390/ma14112817

Biao Yu, Sufyan Garoushi + Show 3 more

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https://doi.org/10.3390/ma14112817

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Abstract

In order to improve the toughness and reduce polymerization shrinkage of traditional bisphenol A-glycidyl methacrylate (Bis-GMA)/triethylene glycol dimethacrylate (TEGDMA) based dental resin system, a hyperbranched thiol oligomer (HMDI-6SH) was synthesized via thiol-isocyanate click reaction using pentaerythritol tetra(3-mercaptopropionate (PETA) and dicyclohexylmethane 4,4′-diisocyanate (HMDI) as raw materials. Then HMDI-6SH was mixed with 1,3,5-Triallyl-1,3,5-Triazine-2,4,6(1H,3H,5H)-Trione (TTT) to prepare thiol-ene monomer systems, which were added into Bis-GMA/TEGDMA resins with different mass ratio from 10 wt% to 40 wt% to serve as anti-shrinking and toughening agent. The physicochemical properties of these thiol-ene-methacrylate ternary resins including functional groups conversion, volumetric shrinkage, flexural properties, water sorption, and water solubility were evaluated. The results showed that the incorporation of HMDI/TTT monomer systems into Bis-GMA/TEGDMA based resin could improve C=C double bond conversion from 62.1% to 82.8% and reduced volumetric shrinkage from 8.53% to 4.92%. When the mass fraction of HMDI/TTT monomer systems in the resins was no more than 20 wt%, the flexural strength of the resin was higher or comparable to Bis-GMA/TEGDMA based resins (p > 0.05). The toughness (it was measured from the stress–strain curves of three-point bending test) of the resins was improved. Water sorption and water solubility tests showed that the hydrophobicity of resin was enhanced with increasing the content of thioester moiety in resin.

Highlights

Dental resin composites that based on photosensitive dimethacrylate monomers, such as bisphenol A-glycidyl methacrylate (Bis-GMA), triethylene glycol dimethacrylate (TEGDMA), and urethane dimethacrylate (UDMA), have been used as dental restorative materials for several decades due to their sufficient mechanical properties, acceptable aesthetics properties, and good bond ability to tooth tissue
Volumetric shrinkage and polymerization shrinkage stress of resin composites lead to restorations marginal microleakage and secondary caries, which reduce the clinical performance of these materials [1,2]
The results of flexural strength (FS), flexural modulus (FM), and toughness of dental resins were shown in Table 5, It was shown that FS of 10% HMDI-6SH/TTT resin and 20% HMDI-6SH/TTT resin was equivalent to that of control resin (p > 0.05) and higher than those of 30% HMDI/TTT resin and 40% HMDI/TTT resin (p < 0.05)

Summary

Introduction

Dental resin composites that based on photosensitive dimethacrylate monomers, such as bisphenol A-glycidyl methacrylate (Bis-GMA), triethylene glycol dimethacrylate (TEGDMA), and urethane dimethacrylate (UDMA), have been used as dental restorative materials for several decades due to their sufficient mechanical properties, acceptable aesthetics properties, and good bond ability to tooth tissue. The distance between monomers is reduced from Van der Waal force (~4 Å) to covalent bond distance (~1.5 Å), and the free volume is reduced too. Shrinkage stress occurs when the contraction is obstructed and the material is rigid enough to resist sufficient plastic flow to compensate for the original volume [3]. It was found that inorganic fillers, resin matrix, coupling agent, and polymerization process would affect the polymerization shrinkage stress [4]

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