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Polymerization contraction stress in thin resin composite layers as a function of layer thickness
D Alster1, A J Feilzer, A J de Gee
1Department of Dental Materials Science, Academic Centre for Dentistry Amsterdam, The Netherlands.
Summary
This study reveals that thinner resin composite layers generate higher curing stress, with a novel method developed to accurately measure this stress. The findings help estimate clinical stress levels in dental restorations.
Area of Science:
- Dental Materials Science
- Polymer Chemistry
- Biomaterials Engineering
Background:
- Curing stress in resin composites is a critical factor influencing the longevity and integrity of dental restorations.
- Accurate measurement of this stress, especially in thin layers, is challenging due to equipment compliance.
Purpose of the Study:
- To investigate the effect of layer thickness on curing stress in thin resin composite films.
- To develop and validate a method for determining the compliance of the test apparatus for accurate stress measurement.
Main Methods:
- Chemically initiated resin composite layers of varying thicknesses (50 microns to 2.7 mm) were tested in a tensilometer.
- Curing contraction stress was measured by counteracting displacement, and apparatus compliance was calculated using non-linear regression analysis based on Hooke's Law.
Main Results:
- Curing stress decreased significantly with increasing layer thickness, from 23.3 MPa (50 microns) to 5.5 MPa (2.7 mm).
- No samples fractured due to contraction stress before tensile loading.
- The compliance of the apparatus was determined to be 0.029 mm/MPa.
Conclusions:
- A reliable method was established for measuring axial polymerization contraction stress in thin resin composite films.
- This method enables better estimation of stress levels encountered in clinical dental applications.