Comparative study of the physical properties of a polyacid-modified composite resin and a resin-modified glass ionomer cement.

OBJECTIVES

The physical properties of the resin-modified composite resin Dyract (Detrey Dentsply) and the resin-modified glass ionomer cement Fuji II LC (GC) were compared, and the effect of water sorption on these properties was studied.

METHODS

Compressive, diametral compressive and flexural strengths were measured using specimens aged up to three months. The Vickers hardness and the water erosion were also determined. The specimens were stored at 37 degrees C under five different conditions, chosen to vary the water sorption of the samples. The results were analyzed using a multi-factor analysis of variance.

RESULTS

Dry specimens of Dyract and Fuji II LC showed similar properties. However, the two materials behaved differently when stored in presence of water. In contrast to Fuji II LC, Dyract showed very little expansion for the first 24 h (1.5 +/- 0.3 and 0.03 +/- 0.01%, respectively), leached small quantities of ions and retained its mechanical strength. Those differences are related to their chemical composition. Fuji II LC is hydrophilic, as it contains polyHEMA. In the presence of water, Fuji II LC behaves like a hydrogel, but the network resulting from the copolymerization of acidic and UDMA monomers is less hydrophilic, and the effect of water on Dyract is retarded.

SIGNIFICANCE

The significant properties of Dyract are determined by its composite character. This certainly represents some advantages, for instance, a higher mechanical strength, a better protection against initial dehydration and subsequent water effects. However, Dyract shows some disadvantages over Fuji II LC, like a lower amount of fluoride release or the interference of oxygen during polymerization.