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J M Paddon

Publications and source records attributed to J M Paddon.

7 recordsLinked to original sources

Dimensional changes occurring in a glass-ionomer cement.

The dimensional changes occurring when glass ionomer cements are exposed both to desiccating and moist conditions were investigated. All work was done at 23 degrees C. The effect of time allowed for cements to mature before exposure to the test conditions was studied as was the effect of adding cellulose ethers. The contraction of glass ionomer cements under desiccating conditions was far greater than the expansion by water absorption. Increase of the time allowed for the cements to mature reduced the extent of this effect markedly. The addition of cellulose ethers to cement mixes was only moderately effective in reducing dimensional change.

Analysis of Variance↗

The hydration of dental cements.

A study was made of the hydration of dental cements, water being classified as "non-evaporable" and "evaporable". The ratio of these two types of water was found to vary greatly among different cement types, being lesser in zinc oxide and ionic polymer cements and greater in ion-leachable glass and phosphoric acid cements. The cement with the least "non-evaporable" water, i.e., showing least hydration (the zinc polycarboxylate cement), had the lowest strength and modulus and the greatest deformation at failure. A linear relationship was found to exist between strength and the degree of hydration of dental cements. All the cements were found to become more highly hydrated and stronger as they aged.

Absorption↗