Chapter 10 - Zinc Phosphate Ceramics

Abstract

This chapter focuses on zinc phosphate ceramics. Zinc phosphate dental cements have been discovered over a century ago, and their development has continued since then. This chapter presents the earlier work in light of the solubility characteristics of zinc oxide and its products in an acid phosphate solution. Roastaing's patents are the first documents that provide formulations, in which zinc oxide is reacted with phosphoric acid to produce dental cements. The purpose behind much of the research is to find ways to retard the fierce reaction between these components so that practical cements can be developed. The role of aluminum in the zinc phosphate cements was considered very important. Aluminum oxide greatly moderated the reaction of zinc oxide and phosphoric acid, and this effect has been attributed to the formation of an aluminum phosphate gelatinous coating on zinc oxide particles. Another major development in zinc phosphate cement is zinc silicophosphate. Mixing aluminosilicate glass and zinc oxide, and then reacting the mixture with phosphoric acid produced this cement. Its properties lie between those of zinc phosphate and silicate cements. This chapter concludes that the ultimate compressive strength of zinc phosphate cements is higher than that of magnesium phosphate cements. Zinc phosphate samples are cast in a very small size as dental cements, while magnesium phosphate cements are used in bulk scale. Because large ceramics and cement casts tend to have more flaws, their strength is expected to be lower.