The mechanical behavior ("shape memory") associated with martensitic solid-state transformation in nearly equiatomic Ni-Ti alloy (55-Nitinol) has been studied. Potential dental and medical applications for 55-Nitinol (55% Ni, 1.5% Co, balance Ti, by weight) and for 60-Nitinol (60% Ni, by weight) have been suggested.

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Thermal capacity, diflusivity, and conductivity were determined for nonmetallic restorative materials. Thermal characteristics were affected by composition, powder-liquid ratio, and water sorption. Diflusivity 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.Thermal properties of tooth structure and dental restorative materials have been investigated by several authors.'-" Most of the studies involve direct thermal conductivity measurements. Difficulties in obtaining steady-state conditions and in estimating and controlling heat losses have contributed toward large variations in reported values even for the same investigators.7,8 Additional difficulties in correlating results arise from an incomplete definition of compositions and powder-liquid ratios or a lack of identification of commercial brands used. The omissions are particularly obvious with liners and zinc oxide-eugenol cement preparations. To circumvent some of the technological difficulties, Braden' has introduced a simple method of determining diffusivity and has suggested that, under transient thermal conditions of the oral cavity, diffusivity, rather than conductivity, is the more important parameter.1030 conductivity determinations, to measure thermal properties of typical conventional nonmetallic restoratives, and to obtain information on some of the newer materials, such as a polymer-reinforced zinc oxide-eugenol cement and a direct filling resin composite. Materials and MethodsMaterials used in this study are listed in Table 1. Diffusivity and conductivity were determined for zinc phosphate, silicate, unmodified zinc oxide-eugenol cements; a resinreinforced zinc oxide-eugenol material; an unfilled direct filling acrylic resin; and a direct filling resin composite. Diffusivity was determined by the method described by Braden.' The specimen was a cube with the hot junction of a copper-constantan thermocouple* embedded in its center. Specimen molds were made of silicone rubber held in approximately 5 cm (-2 inch) sections of a 3.18 cm (1 1/4 inch) diameter copper pipe (Fig 1). The materials were mixed for 30 seconds and packed into the molds holding the thermocouples. The open ends of the molds were covered with glass plates. Except for zinc oxide-eugenol cement, the specimens remained in the molds 24 hours at 37 C and a relative humidity of 100%; they were then defiasked and placed in a desiccator at 37 C for seven hours for dry specimen determinations, or in 50 ml distilled water for seven days at 37 C for wet specimen measurements. To ensure complete set, unmodified zinc oxide-eugenol cement specimens were defiasked 48 hours after starting the mix.The surface moisture of the wet specimens was blotted off with tissue paper before test-* Type T insulated 30 gauge (Brown...

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.