Linear dimensional changes during setting of two polycarboxylate cements

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Abstract
The linear dimensional changes of two polycarboxylate cements have been studied. The measurements were performed on specimens placed on a mercury bath, and were started 3 min after commencing the mix. The specimens were allowed to set at 37 degrees C under various environmental humidity. Specimens from one of the polycarboxylate cements (Durelon), were made using both the universal liquid and the thin liquid meant for cementation. The powder/liquid ratios (P/L) were either 2-5 or 1-5.. Specimens from the second cement (Poly-C), were made using the liquid meant for cementation only with a P/L of 1-5. The dimensional changes of Durelon were dependent on the powder/liquid ratio and the environmental humidity during setting. Under dry conditions this cement showed a maximum contraction of 4-60% after 14 days when a high P/L was used and 6-10% when a low P/L was used. After 1 day under wet conditions no significant differences between cements with high and low P/L were registered, and the mean contraction was 1-10%. The dimensional changes of Poly-C were dependent on the environmental humidity, and after 14 days under dry conditions a maximum contraction of 5-50% was registered and after 1 day under wet conditions a contraction of 0-60%. The contraction of the polycarboxylate cements tested in this study started earlier and were in general more pronounced than that observed for a zinc phosphate cement (Oilo, 1975).

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