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SUMMARYObjectives-To measure the denaturation temperature (Td) of demineralised dentine matrix as a function of infiltration with water vs polar solvents vs adhesive resins.Methods-Small disks of normal dentine were completely demineralised in 0.5 M EDTA. Dried demineralised specimens were placed in water, methanol, ethanol, acetone, η-butanol or HEMA. Additional specimens were infiltrated with Prime & Bond NT and polymerised. All specimens sealed in high pressure pans and scanned using differential scanning calorimetry (DSC).Results-Demineralised dentine saturated with water showed a Td of 65.6°C that increased with saturation by methanol, ethanol, acetone, η-butanol or HEMA to 148.5°C. These increases in Td were inversely related to the molar concentration of the solvents and to their Hoy's solubility parameter for hydrogen bonding (δh, p<0.01), as well as directly related to the cube root of their molecular weights (p<0.001). The presence of adhesive resins also increased the Td of demineralised matrices to even higher values depending if the resin bonded dentine was measured after 24 h of water storage (166.8°C) or dry (172.7°C) storage.Conclusions-Solvents and monomers with low δh values (i.e. 100% HEMA) increase the Td of demineralized dentin above that produced by solvents with higher δh values such as methanol and water.

The effect of a powder bed on the densification behavior of a compact made from a silicon carbide powder and containing yttria and alumina additives has been studied. It has been found that where the powder bed is made of just silicon carbide grit, relative densities of up to 0.92 of the theoretical density can be obtained. Additions of alumina to the powder pack increased the apparent relative density to 0.98. Further experiments have shown that the pack cannot act as a physical barrier to the diffusion of volatile components of the sintering aids. The alumina additions to the pack increase the relative density by allowing the diffusion of alumina species into the sample, rather than by affecting its shrinkage behavior. It is suggested that the predominant effect of the pack is to ensure that the partial pressure of silicon-containing species, such as SiO and Si, within the sample is sufficient to allow reaction between them and the volatile sub-oxides of yttrium and aluminum, forming a liquid phase.