Development of an oxirane/acrylate interpenetrating polymer network (IPN) resin system

Dent Mater. 2018 Oct;34(10):1459-1465. doi: 10.1016/j.dental.2018.06.013. Epub 2018 Aug 1.

Abstract

Objective: Develop a hydrophobic, degradation-resistant dental restorative based on an Oxirane-Acrylate IPN System (OASys) with low shrinkage-stress to substantially extend clinical lifetime.

Methods: Unfilled OASys blends were prepared using dipenta-erythritol-hexaacrylate (DPHA) and p-cycloaliphatic-diepoxide (EP5000). Varying proportions of camphorquinone/iodonium photoinitiator, with a co-reactant oligomeric-diol, served as the experimental curing system. The effects of oxirane-acrylate ratio on the degree-of-cure (Durometer-D hardness), hydrophobicity (contact angle), mechanical properties (3-point bending), near-infrared FTIR degree-of-conversion (DoC), polymerization shrinkage, and shrinkage stress were determined. 70:30 BisGMA:TEGDMA resin served as control.

Results: Oxirane tended to decrease hardness and increase hydrophobicity. 0:100, 25:75, 50:50 EP5000:DPHA are harder after 24h than control. 75:25 and 100:0 EP5000:DPHA increased in hardness over 24h, but were softer than control. All groups increased in contact angle over 24h. After 24h, 50:50, 75:25 and 0:100 EP5000:DPHA were more hydrophobic (∼75-84°) than the control (∼65°). Acrylate DoC was ∼60% across all experimental groups. Initial oxirane conversion varied from ∼42% in 100:0 EP5000:DPHA to ∼82% 75:25 EP5000:DPHA. However, oxirane DoC increased for 100:0 EP5000:DPHA to ∼73° over 24h, demonstrating dark cure. Moduli and ultimate transverse strengths of OASys groups were higher than for 0:100 EP5000:DPHA, with 50:50 EP5000:DPHA having higher modulus than other experimental groups. However, the control had higher modulus and UTS than all experimental groups. Volumetric shrinkage averaged 7% for experimental groups, but stress decreased dramatically with increasing oxirane content.

Significance: Hydrophobic, low shrinkage-stress OASys resins are promising for development of composites that improve longevity and reduce the cost of dental care.

Keywords: Acrylate; Cationic photoinitiation; Degree of conversion; Hydrophobicity; Interpenetrating network; Oxirane; Restorative resin; Shrinkage stress; Volumetric shrinkage.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Acrylates / chemistry*
  • Bisphenol A-Glycidyl Methacrylate / chemistry
  • Composite Resins / chemistry*
  • Dental Materials / chemistry*
  • Elastic Modulus
  • Ethylene Oxide / chemistry*
  • Hardness
  • Hydrophobic and Hydrophilic Interactions
  • Materials Testing
  • Polyethylene Glycols / chemistry
  • Polymers
  • Polymethacrylic Acids / chemistry
  • Spectroscopy, Near-Infrared
  • Stress, Mechanical
  • Surface Properties

Substances

  • Acrylates
  • Composite Resins
  • Dental Materials
  • Polymers
  • Polymethacrylic Acids
  • triethylene glycol dimethacrylate
  • Polyethylene Glycols
  • Bisphenol A-Glycidyl Methacrylate
  • Ethylene Oxide