Polymerisation shrinkage of luting agents for crown and bridge cementation.

ABSTRACT

The volumetric contraction of a variety of luting agents, including Panavia 21, All-Bond C&B Cement, Superbond., Variolink and zinc phosphate cement, was assessed and compared using a minimal transducer The contraction among the materials tested was determined from the post-gel linear displacement of a deflecting coverslip resting on 4 silicone rubber spacers between which a mixed material was centrally located. Finally, the rate and duration of shrinkage over a period of 60 minutes from the moment of rigid contraction for all materials were investigated, and the final shrinkage values among the materials tested were compared. The analysis of variance showed that there were highly significant differences (P< 0.001) between the materials and the mean of each group was significantly different from that of any of the other groups (Tukey's test). Superbond produced the highest values of the final polymerisation shrinkage, followed by All bond C&B, Variolink, Panavia 21 and zinc phosphate cement respectively. Also, there was a marked variation in the overall magnitude of shrinkage (from 1.34% to 4.62%) among the materials tested. The method used to measure the polymerisation shrinkage in the present study was shown to be a precise measure in that it produced consistent and reproducible results. It can also offer the ability to observe the development of polymerisation shrinkage against time, during the post-gelation phase, for a range of chemically-cured resin materials.