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Does single versus stepped curing of composite resins affect their shear bond strength?
R Caldwell1, G Kulkarni, K Titley
1Edmonton, Alberta, Canada.
Journal (Canadian Dental Association)
|December 12, 2001
Summary
Stepped photo-polymerization did not improve resin composite shear bond strength compared to single-cure methods. Thicker increments (over 2mm) may reduce bond strength, especially with single-bottle adhesives.
Area of Science:
- Dental Materials Science
- Polymer Chemistry
- Biomaterials Engineering
Background:
- Polymerization shrinkage in resin composites impacts physical properties and restoration integrity.
- Stepped photo-polymerization is proposed to reduce shrinkage compared to single-cure methods.
- Resin composite increment thickness may influence final shear bond strength.
Purpose of the Study:
- To compare shear bond strength of resin composites cured by stepped versus single-cure photo-polymerization.
- To evaluate the effect of varying resin composite increment thicknesses (1.5, 3, and 4.5 mm) on shear bond strength.
- To assess the influence of two different adhesive systems (Scotchbond Multipurpose and Singlebond) on bond strength outcomes.
Main Methods:
- Human third molar dentin was used as the substrate.
- Resin composite increments of 1.5, 3, and 4.5 mm were cured using either stepped or single-cure photo-polymerization.
- Bonding was achieved with either the Scotchbond Multipurpose or Singlebond adhesive system.
- Shear bond strength was tested after 7 days of water storage, and failure modes were analyzed.
Main Results:
- No significant difference in shear bond strength was observed for the Scotchbond Multipurpose adhesive, regardless of curing method or thickness.
- Significantly lower shear bond strength was found with the Singlebond adhesive when using 4.5 mm thick increments.
- A trend towards increased adhesive cohesive failures was noted with thicker resin composite increments.
Conclusions:
- Stepped photo-polymerization offers no significant advantage over single-cure photo-polymerization for shear bond strength in this study.
- Resin composite increments should ideally not exceed 2 mm in thickness for optimal bonding, particularly when using single-bottle adhesives.
- Clinical recommendations suggest limiting increment thickness to maintain restoration integrity and bond strength.
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