Silicophosphate cement

For a consistency spread of 25 mm diameter for 0-5 cm of cement paste under a load of 220 gf applied after 2 minutes at 23 °C. 

The silicophosphate cement originated with the dental silicate cement, for there is no doubt that early investigators experimented with mixtures of aluminosilicate glass and zinc oxide (Fletcher, 1878,1879 Eberly, 1928). It appears to have no particular advantages. As is often the case with hybrids, it can combine the worst features as well as the best of the parents, and often properties have intermediate values. Nevertheless, it continues to have a small but persistent usage arising from its one advantage over the 

The flow properties are not as good as those of zinc phosphate cement (Eames et al., 1978 Hembree, George Hembree, 1978) and film thickness is greater (Table 6.11). Moreover, it does not have the translucency of dental silicate cement (Wilson, 1975c). 

Silicophosphate cement acts as an agent for the sustained release of fluoride, although different cements behave very differently (Wilson, Crisp Lewis, 1982). Silicophosphate cement has a disability in the mouth similar to that of dental silicate cement. It is less resistant to oral fluids than glass polyalkenoate cement, but more resistant than all other dental cements, as is shown by both in vivo studies (Norman et al., 1969 Ritcher Ueno, 1975 Clark, Phillips Norman, 1977 Mitchem Gronas, 1978  

Osborne et al., 1978) and the laboratory impinging jet method (Beech Bandyopadhyay, 1983 Wilson et a/., 1986a). 

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BS 3365/1 1969 Specification for Dental Silicate Cement and Dental Silicophosphate Cement. Part 1 Dental Silicate Cement. 

Poetschke (1925) patented a dental silicate powder prepared by fusing zinc silicate with calcium fluoride. This is a kind of silicophosphate cement (Section 6.6). Thomsen (1931) attempted to formulate a water-setting dental cement. Heynemann (1931) included lithium salts in the flux and Brill (1935) included them in the liquid. 

Table 6.11. Specification properties of commercial luting silicophosphate cements ( Anderson Paffenbarger, 1962)...

Table 6.12. Specification properties of commercial filling silicophosphate cements Wilson, 1975c)...

Other silicophosphate cements that use cation-releasing silicates are based on wolla-stonite [33], and serpentinite [34,35]. Naturally occurring phosphate cements have also been known [36]. In these cements, silicates are sparsely soluble and release cations (Ca, and Mg ), which react with the phosphate anions to form hydrophosphates and eventually convert to phosphates. This process is similar to that involving zinc phosphate cements, in which hydrophosphates form first, then convert to phosphates during aging. 

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