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Photocurable epoxy-polyol matrices for use in dental composites I
D A Tilbrook1, R L Clarke, N E Howle
1IRC in Biomedical Materials, Department of Biomaterials in Relation to Dentistry, Queen Mary and Westfield College, London, UK.
Biomaterials
|July 25, 2000
Summary
New cycloaliphatic epoxy resins offer lower shrinkage and improved strength for dental composites compared to traditional dimethacrylates. Careful formulation is key to managing water absorption and preventing cracking in these advanced dental materials.
Area of Science:
- Materials Science
- Polymer Chemistry
- Biomaterials Engineering
Background:
- Dimethacrylate polymers are standard in dental composites but suffer from high shrinkage.
- Cycloaliphatic epoxy resins with polyol extenders present a promising alternative for low-shrinkage dental materials.
- Visible-light curing systems are preferred for dental applications due to ease of use.
Purpose of the Study:
- To characterize epoxy-polyol matrices for dental composite applications.
- To investigate the influence of polyol type and epoxy-to-polyol ratio (R) on material properties.
- To evaluate epoxy-polyols as replacements for dimethacrylate resins.
Main Methods:
- Formulation of epoxy-polyol matrices with varying polyol types and R values.
- Curing using cationic onium/camphorquinone initiators under visible light.
- Material characterization including shrinkage, oxygen inhibition, strength, hardness, glass transition temperature (DMA), and water uptake.
- Analysis of hydration effects and potential for cracking.
Main Results:
- Epoxy-polyols demonstrate significantly lower polymer shrinkage and no oxygen inhibition layer compared to dimethacrylates.
- Higher strength, equivalent hardness, and acceptable glass transition temperatures were observed.
- Water mass increase was nearly double that of dimethacrylates, with cracking noted in some samples during hydration.
- Careful selection of formulation parameters, specifically R between 4 and 8, mitigates cracking.
Conclusions:
- Epoxy-polyol matrices offer substantial advantages over dimethacrylates for dental composites, including reduced shrinkage and enhanced mechanical properties.
- Optimizing the epoxy-to-polyol ratio (R) is critical for balancing material properties and preventing hydration-induced damage.
- Further research is needed to reduce water uptake in epoxy-polyol matrices for improved long-term stability in dental applications.