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At least 19 recordsLinked to original sources
PubMed1976

Adhesion of polycarboxylate cements to dental casting alloys.

The adhesive strengths of four commercial polycarboxylate cements to five dental casting alloys were compared with the strength of a conventional zinc phosphate cement. The following results were obtained. (1) The polycarboxylate cements showed adhesion that was four to 12 times greater than that of the zinc phosphate cement to all alloys tested. (2) The adhesive strength of the polycarboxylate cements was greater to the chemically active substitute alloys, such as the copper, nickel-chromium, and silver-tin-zinc alloys. The adhesion of the polycarboxylate cements to the chemically stable gold and silver-palladium alloys was not as great, but was four to six times that of the zinc phosphate cement. (3) The difference in adhesive strength between the brands of polycarboxylate cement was generally slight or statistically insignificant.

Acrylates↗
PubMedDate not supplied

Reinforced polycarboxylate cements.

Mechanical properties of polycarboxylate cements are greatly improved by incorporation of high modulus fibers such as potassium titanate into acrylic-itaconic acid and acrylic-itaconic-acronitic acid copolymers. Other desirable properties of the cements are not changed by the addition of fibers.

Aconitic Acid↗
PubMed1976

Linear dimensional changes during setting of two polycarboxylate cements.

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).

Acrylates↗
PubMedDate not supplied

Zinc polycarboxylate cements: a chemical study of erosion and its relationship to molecular structure.

Experimental results show that the rate of elution of Zn2+ and Mg2+ ions from polycarboxylate cements decrease with the cement's age. This phenomenon is explained by the setting reaction in which these cations are liberated from the oxide powder by an exchange with protons from the polyacid and in this state are vulnerable to water leaching. Subsequently, these cations become bound to the polyanion chain and become more resistant to water leaching. Magnesium ions are more easily hydrolyzed than zinc ions because they are less strongly bound to the polyanion chain. Zinc ions are apparently more strongly bound to a polyacid which is a copolymer of acrylic and itaconic acids, than to the homopolymer of acrylic acid. The pattern of elution of ions differs between the different cements, so that measurements after 24 hours cannot be used to predict long-term durability on a comparative basis. This coupled with the slow but continuous loss of ions makes a 24-hour test of doubtful validity. Polycarboxylate cements absorb water that is present in the matrix in loosely bound and tightly bound forms. The ionization of the polyacid to a polyanion during the course of the reaction apparently creates a demand for water, and the cement where the COOH:C ratio in the polyacid is highest absorbs the most water.

Absorption↗
PubMed1978

Punch shear strength of polycarboxylate cements.

Two general conclusions are drawn which apply to all the four commercial polycarboxylate cements: First, the effect of storage condition upon shear strength was much more pronounced after 24 hours than after 1 hour of storage time; second, the effect of storage condition was most extreme when the specimens were tested free of their matrices. Additionally some specific comparisons between the four products tested can be made based on differences of shear strength within the same experimental condition. The effect of confinement decreased in the following order: Boston greater than Bondal greater than PCA greater than Durelon. Sensitivity to storage conditions decreased in this order: Durelon greater than Bondal greater than PCA greater than Boston. Finally sensitivity to storage times decreased in the order Bondal greater than Durelon greater than Boston greater than PCA.

Acrylic Resins↗
PubMed1976

Sealing quality of polycarboxylate cements when compared to amalgam as retrofilling material.

Four hundred roots were uniformly prepared for retrofilling. One hundred of these were retrofilled with amalgam and served as controls for the study. The polycarboxylate cements--Durelon, PCA, and Poly C--were each used as retro-filling material for 100 roots. After immersion in 2 per cent aqueous methylene blue for 7 days, the roots were sectioned in 1 to 2 mm. increments to determine the depth of dye penetration. The depth of dye penetration was used as a measure of their sealing effectiveness. The groups were compared statistically by means of a t test. All cements were significantly different from amalgam. All cements performed inferiorly to amalgam, an already accepted retrofilling material.

Acrylates↗
PubMed1979

The role of diffusible ionic species in the bonding of polycarboxylate cements to dentine: an in vitro study.

Treatment of freshly-cut dentine with fluoride ions or high concentrations of metal ions produced changes ranging from mineralization of tubule contents to precipitation of adherent surface layers. Combinations of these treatments with application of fluoridated and non-fluoridated polycarboxylate cements and glass ionomer cements produced both increases and reductions in bond strength which are explained by ionic diffusion at the interface prior to setting.

Acrylic Resins↗
PubMed1975

Investigation of possible oncogenic action of zinc polycarboxylate cement by implantation in mice and hamsters.

Powdered, sterilized zinc polycarboxylate was implanted subcutaneously in 56 young hamsters and 54 mice, using equal numbers of each sex, with 24 sham operated hamsters and 26 mice as controls. The hamsters were sacrificed after 15 months and the mice after 12. Implant material was recovered from one of 42 surviving mice and from 16 of 43 surviving hamsters. Benign adenomas of the gut, thyroid, sebaceous glands and ovary were found in 3 experimental mice and in one control. Benign adrenal adenomas were found in 3 experimental hamsters and in one control. One control hamster developed a rhabdomyosarcoma in a limb. One experimental hamster developed a leiomysarcoma in close relation to an implant.

Acrylates↗