R. S. Tobias

Toxicity testing of inlay cements

This investigation was designed to study the pulpal responses to inlay cements using a technique modified from the conventional methods for testing restorative materials (BSI 1980) and to study the relationship between pulpal response and microbial microleakage. Standardised Class V cavities were prepared in ferret canine teeth after ketamine/xylazine anaesthesia. A stainless steel inlay pin was cemented into each cavity with Kalzinol, Aquacem, Poly F plus and zinc phosphate cements. Animals were killed with excess sodium pentobarbitone after seven, 14, 28 and 183 days and the canine teeth removed. Poly F plus and Kalzinol caused minimal pulpal changes. Aquacem produced a slight response whereas zinc phosphate caused the greatest response. These responses were less than when the same materials were placed in cavities alone and their onset was delayed. A significant positive correlation was found between pulpal inflammation and bacterial microleakage. There was no statistically significant correlation between pulpal inflammation and residual dentine thickness nor between bacterial microleakage and residual dentine thickness. Considerable pressure was exerted when cementing the inlay pins. so this technique provides a realistic method for testing the toxicity of inlay cements.

A study of the relationship among pulpal response, microbial microleakage, and particle heterogeneity in a glass-ionomer-base material

This investigation was designed to study the pulpal responses to glass-ionomer base materials that differ in particle size distribution. The study was carried out according to the BSI (1980) recommendations for testing restorative materials in vivo. The base materials caused more pulpal inflammation than the control material, Kalzinol, although by an indirect mechanism. A significant association was demonstrated in the statistical model between bacterial presence within the experimental cavity and pulpal inflammation. The type of restorative material has no direct association with the degree of inflammation, although the model suggests that it exerts an indirect influence via its antibacterial properties, and hence its influence on microbial microleakage. The base material, with a heterogeneous particle distribution, was associated with greater bacterial microleakage. Particle size distribution, therefore, has some effect upon bacterial microleakage, but, because of its complex effect upon several physical properties of materials, further studies are indicated.

An in vitro study of zinc in dentine beneath cavities filled with two dental cements

The concentrations of zinc ions in dentine in vitro beneath cavities filled with zinc oxide/eugenol and zinc phosphate cements were measured by atomic absorption spectrophotometry. No significant difference was recorded between the two materials over a period of 15 weeks. The clinical significance of this finding is discussed.

A method for testing the toxicity of temporary crown and bridge materials

A realistic method for testing the toxicity of a temporary crown and bridge material in vivo is described. The results are compared with a previous study. It is stressed that temporary crown and bridge materials should never be used as a temporary filling material.