The research which tries to use the laser to join the dental prosthesis has been done for about 40 years. It turned out to be able to use the laser welding to join the dental prosthesis effectively from results of a lot of researches. As a result, the laser welder for dental use is developed now and they has come to be used for clinical widely. However, the problem of the laser welding has begun to be worried as use spreads. The welding deformation and the welding defect accompany the laser welding. These problems were pointed out from early time and the improvement of these has come to be requested as a clinical application spreads. Efforts are being turned to the improvement of these problem in the laser welding now. The welding deformation is caused by the coagulation and heat shrinkage of the weld. The shape of fusion zone greatly influences the welding deformation. The deformation is small when diameter of fusion zone is small and melted shape is near the column form. The existence of the element which forms the eutectic with low melting point greatly influences about the crack generation. Sulfur, phosphorus and carbon increase the occurrence of the solidification crack. The welding method for preventing deformation and the alloy design for preventing crack generation being examined. Porosity often generation by remaining of the keyhole. Pulse shaping is effective to porosity. The research on pulse shaping might be advanced further by the appearance of the laser welder with pulse-shaping function. As a result, a better laser welding can be expected to become possible.
