Simon Civjan

Thermal Properties of Nonmetallic Restorative Materials

Thermal capacity, diffusivity, and conductivity were determined for nonmetallic restorative materials. Thermal characteristics were affected by composition, powder-liquid ratio, and water sorption. Diffusivity and conductivity followed the same order of values. The least conductive material investigated was an unfilled acrylic resin. Highest diffusivities and conductivities were exhibited by a resin composite. Values obtained with the composite were about the same as those obtained for a thick mix of unmodified zinc oxide-eugenol cement.

Characterization of Zinc Oxide-Eugenol Cements Reinforced with Acrylic Resin

Zinc oxide-eugenol cements reinforced with poly(methyl methacrylate) have significantly higher strength than unmodified formulations. The degree of reinforcement appears to depend on the particle sizes and uniformity of distribution of the resin constituents.

Effects of Heat Treatment on Mechanical Properties of two Nickel-Chromium-Based Casting Alloys

Mechanical and heat treatment characteristics of two nickel-chromium-based dental casting alloys were investigated. Both alloys showed rapid response to heat treatment. In their softened state the alloys lost 25 to 50% of their as-cast hardness. Elongation was 20 to 45%. Rehardening nearly restored as-cast strength, whereas elongation values remained at 10 to 17%.

Electric Pulp Vitality Testers

Output of three commercially available electric pulp testers were compared. Clinical threshold settings of the instruments could not be correlated to peak voltage, root mean square voltage, or power outputs determined by use of a simulated load impedance. A mathematical expression to establish a relation between threshold settings and output information is suggested.

Characterization of Osseous Tissues by Thermogravimetric and Physical Techniques

Changes in osseous tissue after injury were studied in monkeys with the use of thermogravimetric analysis (TGA) and mechanical strength measurements. An exponential relationship was found to exist between strength and weight loss for repair tissues 3 to 8 weeks old. The quantitative techniques investigated seem promising for the improved characterization of mineralized tissue.

Properties of n-Butyl-α-Cyanoacrylate Mixtures:

Properties of filled n-butyl-α-cyanoacrylates were studied as a function of filler-monomer ratio, time, and curing conditions. Matrix characteristics were determined on amine initiated bulk polymer. Calcium carbonate and mixtures of zinc oxide and zinc phosphate formed reinforced materials with low solubility and disintegration.

Surface characteristics of alginate impressions

Abstract The effects of storage conditions on the surface characteristics of three irreversible hydrocolloids were studied. Downward inversion of impressions markedly slowed surface changes in air. Counter-replicated detail was relatively stable in dilute aqueous solutions of potassium sulfate, potassium chloride, and sucrose. Rapid surface deterioration occurred in aqueous solutions of zinc or calcium sulfates and in ~99 per cent ethyl alcohol.

Properties of surgical casting alloys

Abstract The properties of two surgical casting alloys (Vitallium and Ticonium) were determined and related to their compositional and microstructural characteristics. It was found that Vitallium was a Co-Cr based alloy. Major constituents of Ticonium were Ni, Cr, and Co. Both alloys had cored microstructures. Vitallium was superior in strength, whereas Ticonium had significantly lower hardness and greater ductility. The strength, hardness, and lower ductility of Vitallium could be attributed to a relatively high carbon content (0.04 per cent) and the presence of interdendritic precipitates.

Further Studies of Resin-Modified Temporary Restorative Materials

Composition and physical properties of a polycarbonate resin-reinforced zinc oxide-eugenol cement and of a formulation based on zinc oxide, eugenol and o-ethoxybenzoic acid (EBA) were determined. Both materials were similar in strength, but the polycarbonate-containing material was tougher and showed less solubility and disintegration. Cementing film thicknesses were obtained with the EBA cement.