Shrinkage stresses associated with incremental composite filling techniques

Area of Science:

• Dental Materials Science
• Biomaterials Engineering
• Polymer Science

Background:

• Polymerization shrinkage of composite resins is a significant clinical concern, potentially leading to stress generation.
• Incremental filling is widely adopted to mitigate these shrinkage stresses.
• Recent finite element analysis suggests incremental techniques may increase stress in simple preparations.

Purpose of the Study:

• To visualize and compare polymerization shrinkage-induced stresses in photoelastic models.
• To evaluate different incremental filling techniques against bulk placement in molar preparations.

Main Methods:

• Photoelastic models of primary molar preparations were created.
• Cavity walls were treated with unfilled resin.
• Hybrid composite resin was placed using gingivo-occlusal, oblique, facio-lingual, and bulk techniques.
• Stresses were observed using circular polariscopy.

Main Results:

• Few significant differences in shrinkage stresses were observed among the tested incremental techniques.
• The bulk placement technique resulted in the lowest observed shrinkage-induced stresses.
• Photoelastic analysis provided direct visualization of stress distribution.

Conclusions:

• The conventional understanding that incremental placement reduces polymerization shrinkage stress may not hold true for all techniques.
• Bulk placement demonstrated superior performance in minimizing shrinkage stress in this photoelastic model study.
• Further research is needed to fully elucidate the biomechanical effects of different composite placement strategies.