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Effects of polymerization contraction in composite restorations
R L Sakaguchi1, M C Peters, S R Nelson
1Department of Oral Science, University of Minnesota School of Dentistry, Minneapolis.
Journal of Dentistry
|June 1, 1992
Summary
Researchers developed a new model to measure polymerization contraction stress in dental composites. Heliomolar showed significantly lower contraction strain compared to other materials, indicating reduced stress on tooth structure.
Area of Science:
- Dental Materials Science
- Polymer Chemistry
- Biomaterials Engineering
Background:
- Polymerization contraction in dental composites generates stress at the restoration-tooth interface.
- Accurate measurement of this stress is crucial for understanding restoration longevity and tooth integrity.
- Existing methods for measuring linear contraction have limitations.
Purpose of the Study:
- To develop and validate a novel model for measuring polymerization contraction stress in dental composites.
- To compare the polymerization contraction strain and stress of four different dental composite materials.
Main Methods:
- A new experimental model was designed, simulating a composite restoration surrounded by dentin using an acrylic ring.
- Strain gauges were employed to simultaneously measure the dimensional changes of the composite sample and the deformation of the acrylic ring.
- Polymerization contraction stress was calculated based on the measured strains and the material properties of the acrylic ring.
Main Results:
- Heliomolar exhibited significantly lower post-gel polymerization contraction (0.12%) after 60 seconds of light application compared to other tested composites.
- While Heliomolar consistently showed lower contraction strain, statistical significance was not maintained at the 14-minute equilibrium point.
- P-50 generated the highest contraction stress (1.7 MPa) on the acrylic ring immediately after light application, whereas Heliomolar produced the lowest (0.3 MPa), though differences were not statistically significant.
Conclusions:
- The developed acrylic ring model effectively simulates the stress experienced by dental composites during polymerization.
- Heliomolar demonstrates a favorable low polymerization contraction strain, potentially leading to reduced stress on the tooth structure.
- Further research is warranted to fully elucidate the clinical implications of varying contraction stresses among different composite materials.