THE EFFECT OF COMPOSITION OF LIQUID AND POWDER ON THE PHYSICAL PROPERTIES OF SILICATE CEMENTS

¹ Department of Chemistry, Tufts College, and Tufts College Dental School, Boston, Mass.

A survey has been made of the possibilities of improving the properties of dental silicates by modification of the kind or amount of modifier in liquid and by varying the kind and amount of flux and the proportions of usual oxides in the powder. The suitability of various compositions was judged from determination of consistency, setting time, hardness, and water solubility. In some instances the acid solubility, the refractive index of the powder, and the opacity of the set cement were measured. Liquids were evaluated by mixing these with a commercially available powder, and powders were compared in most instances after forming cements with a commercial liquid.

When aluminum or zinc was used alone as a modifier, the physical properties of the cement were approximately the same as that prepared from a special control liquid and that prepared from a commercial liquid. Magnesium, indium, calcium, barium, titanium, and beryllium proved to be unsuitable as single modifiers in the liquid. Barium, calcium, and indium oxides could be used as comodifiers with zinc oxide without deleterious effect on the physical properties, but there was no indication of general improvement.

Only a very narrow range of composition containing CaO, SiO₂, and Al₂O₃ could be fused to clear glasses which would set within the proper length of time with silicate liquids. Several different compounds could be used as fluxes for increasing the range of compositions that would set. No composition was found which was appreciably superior in properties to representative commercial products and all powders tested were deficient in translucency.