Abstract
The purpose of this study was to explore the possibility of reusing for rapid burnout type gypsum-bonded investment materials which are frequently used in dentistry. The study added burned out investment materials into new investment at a rate of up to 80% and examined the physical and mechanical properties, x-ray diffraction analysis and fitness of castings made by recycled investment materials and investment material particle morphologies by SEM. The following results were obtained: 1. The strength of the trial reused investments satisfied the specification requirement for gypsum-bonded investment when the burned out investment materials were added at a rate of up to 20%. 2. X-ray diffraction analysis detected calcium sulfate anhydrate after the burning-out of investment materials, but not before their burning-out. 3. Based on the present fitness study, the recycled investment materials which contained burned out investment materials at a rate of up to 30% could be utilized in dental laboratory procedures.
