Alternative methods for determining shrinkage in restorative resin composites

Area of Science:

• Dental Materials Science
• Polymer Chemistry
• Biomaterials Engineering

Background:

• Polymerization shrinkage is a critical factor in dental composite performance, potentially leading to marginal gaps and secondary caries.
• Accurate measurement of polymerization shrinkage is essential for material selection and clinical success.

Purpose of the Study:

• To evaluate and compare polymerization shrinkage of seven resin composites using coordinate measuring machine (CMM), optical coherence tomography (OCT), and Archimedes Principle.
• To test the hypotheses that there are no differences between materials and no differences between measurement methods.

Main Methods:

• Seven resin composites were tested. Polymerization shrinkage was measured using CMM (volume difference), OCT (linear shrinkage), and Archimedes Principle (buoyancy).
• Statistical analysis included ANOVA and the Games-Howell test to compare shrinkage values and material rankings across methods.

Main Results:

• Polymerization shrinkage values varied depending on the measurement method employed.
• Despite numerical differences, the ranking of resin composites for shrinkage was consistent across methods, with Filtek P90™ exhibiting the lowest values.
• Silorane-based resin composites demonstrated reduced polymerization shrinkage irrespective of the measurement technique.

Conclusions:

• While direct comparison of absolute shrinkage values across different methods is limited due to variations, materials can be ranked for polymerization shrinkage.
• The study confirms that silorane-based composites offer a significant advantage in reduced polymerization shrinkage.
• These findings aid in selecting dental composites with lower shrinkage, potentially improving clinical outcomes.