Thermal modeling of laser welding for titanium dental restorations

Statement of problem. Concerns of laser welding for titanium dental prostheses are the limited depth of laser beam penetration and extensive surface damage. Purpose. This study used numerical heat transfer simulation to explain this behavior and offers an alternate multiple-pulsed method. Material and methods. A one-dimensional finite difference analysis was used to simulate heat transfer in pure titanium and gold during laser welding with a custom-constructed software program. Results. The thermal gradient profiles revealed the problem to be inherent in titanium's low thermal conductivity; gold did not have this problem. Time-elapsed multiple pulses on titanium relieved this problem by giving the energy time to diffuse into the depth of the material. Conclusions. With single-pulse laser irradiation on titanium, an increase in power could not greatly increase melting depth. The excess energy only vaporized the material surface. (J Prosthet Dent 1998;79:335-42.)