Polymerisation shrinkage around composite resin restorations--an in vitro study

The aim of this study was to determine the degree of penetration of a fluorescent adhesive at the margins of 3 brands of posterior composite resin restorative materials. Seventy-eight extracted human premolar teeth were used. Class II cavities were prepared on both approximal surfaces of each tooth in such a manner that the gingival wall was situated apical to the amelo-cemental junction. The enamel of the cavity walls was bevelled, etched and treated with the enamel bonding agent recommended by the manufacturer. The 3 brands of composite resin used were: Fulfil, Estilux Posterior and P 50. The teeth were divided at random into 3 groups of 26 premolars each. The mesial and distal cavities of each tooth in the group were filled with the same brand. The resin was inserted in two increments in both the mesial and distal cavities and polymerised. The margins of one restoration in each tooth was coated with fluorescent adhesive and cured. All the restored teeth were embedded in clear epoxy resin and then sectioned. The mounted sections were examined at 100X magnification with fluorescent light. The polymerisation contraction gap at different areas of the tooth/restoration interface and the degree of penetration of the fluorescent adhesive into the gap was determined. The fluorescent adhesive penetrated the contraction gaps in all 3 posterior restorative materials to varying degrees. The defects observed were similar in all 3 brands and the differences in degree of penetration were not statistically significant (p > 0.05).