Effect of Layering Methods, Composite Type, and Flowable Liner on the Polymerization Shrinkage Stress of Light Cured Dental Composites.

摘要

Composite restoration has become an essential part of everyday dental practice with the improvement in dental adhesive system, the increase in patients esthetic demand and more emphasis on preservation of tooth structure. However, Polymerization shrinkage and its associated stress still remains a main drawback of composite restoration in dentistry [1, 2]. Polymerization shrinkage causes stress at the interface between a tooth and a restoration as the modulus of composite increases during curing. This stress manifests as bond failure, cuspal flexure, enamel microcrack, pulpal irritation and secondary caries due to bacterial infiltration, and post operative sensitivity, which in turn can lead to restoration failure and require re-restoration [3, 4]. Clinical strategies suggested to minimize shrinkage stress of composites include incremental filling technique, soft-cure or pulse-delay cure method, and the use of low-modulus intermediate liner such as flowable composites to absorb shrinkage stress [2, 4, 5]. However, conflicting results have been reported regarding the efficacy of the methods. Measurement of cuspal deflection is a useful way for evaluating polymerization shrinkage stress, but the use of extracted teeth for cuspal deflection measurement can produce significant discrepancies among specimens due to the lack of standardizing the anatomical and histochemical characteristics of each individual tooth [6].