Compliant phase reduces polymerization shrinkage in dental composite resin

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Abstract

Commercially available dental composite resins undergo polymerization shrinkage during curing, setting up internal stress that can result in debonding at the tooth-composite interface, tooth fracture and composite failure. Debonding can also lead to marginal leakage and recurrent decay. The presence of a compliant phase, in this case polybutadiene in aggregate form with fumed silica, is shown to reduce polymerization shrinkage in the bis-GMA/TEGDMA resin system. The addition of a small amount of the plasticizer triphenylethylene promoted additional reduction in cure shrinkage by reducing the glass transition temperature, Tg. A trend toward reduced cure shrinkage was noted as the polybutadiene : silica ratio decreased within each molecular weight of polybutadiene tested. The optimal formulation tested was determined to be 0.25 wt. % triphenylethylene in bis-GMA with aggregates formed from polybutadiene of molecular weight 2–3 million, in a polybutadiene : silica ratio of 0.005. Shrinkage reduction in this system was ∼ 42% without loss of Knoop hardness. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2306–2310, 2005

Ancillary