Thermal expansion coefficient of titanium casting

A reliable measurement of the thermal expansion coefficient (α) value is required to achieve a positive thermal mismatch between metal and porcelain for porcelain-fused to metal crowns. Heating rate and specimen conditions may significantly influence the α value and the effects of these factors were studied. Commercially pure cast titanium rods, ‘as cast’ and sandblasted, were heated at various conditions. According to this study, the discrepancy of α values between heating and cooling conditions was insignificant when the heating (cooling) rate was reduced to 1 °C min⁻¹. It was revealed that α values obtained from 1 °C min⁻¹ cooling rates should be utilized. Dental porcelain with an α value lower than 8·5 × 10⁻⁶ °C will be suitable for titanium-ceramic applications.