For many of us composite is the first and only choice as a direct restorative material today. Although realistically we all know that no restoration lasts forever, we strive for the greatest longevity and durability we can achieve. Clinical and research data support that the two most common reasons we replace a composite restoration are recurrent decay and marginal leakage. So why should you care about the polymerization shrinkage of your composite? Simple, there is a direct linkage between the shrinkage stress of the composite and the longevity of the restoration. We have many great researchers looking at polymerization shrinkage and shrinkage stress of composite restorative materials and it’s impact on clinical performance. The results across these studies are consistent.
Higher contraction stress is associated with:
- Larger gap formation at the interface between composite and the tooth
- Increased marginal leakage
- Increased crack propagation
- Decreased bond strengths
All of these factors are working against our goals and accelerate failure of the restoration clinically. There are many factors that contribute to contraction stress, some we have no control over, like the preparation “C” factor, which is dictated by the condition of the tooth. We can manage the stress through utilization of placement techniques, resilient liners and light application. Maybe most importantly we have control over the composite we use, and at the top of the list for how we compare materials should be an understanding of its “Shrinkage Stress”. Using a material that has low shrinkage stress in combination with great technique is a sure recipe for improved clinical results.