Research Summary: Reducing the variations in laser welding
Objective Interactions between lasers and materials are very complex phenomena. The success of laser welding procedures in dental metals depends on the operator's control of many parameters. The aims of this study were to evaluate factors relating to the operator's dexterity and the choice of the welding parameters (power, pulse duration and therefore energy), which are recognized determinants of weld quality.Design In vitro laboratory study.Materials and methods FeNiCr dental drawn wires were chosen for these experiments because their properties are well known. Different diameters of wires were laser welded, then tested in tension and compared to the control material as extruded, in order to evaluate the quality of the welding. Scanning electron microscopy of the fractured zone and micrograph observations perpendicular and parallel to the wire axis were also conducted in order to analyse the depth penetration and the quality of the microstructure. Additionally, the micro-hardness (Vickers type) was measured both in the welded and the heat-affected zones and then compared to the non-welded alloy.Results Adequate combination of energy and pulse duration with the power set in the range between 0.8 to 1 kW appears to improve penetration depth of the laser beam and success of the welding procedure. Operator skill is also an important variable.Conclusion The variation in laser weld quality in dental FeNiCr wires attributable to operator skill can be minimized by optimization of the physical welding parameters.
LASER WELDING OF DENTAL ALLOYS: A SYSTEMATIC OVERVIEW
1 LASER WELDING OF DENTAL ALLOYS: A SYSTEMATIC OVERVIEW Shanti Varghese1, Vinaya Bhat2, Suja Joseph3, 1) Department of Prosthodontics, Noorul Islam College of Dental Sciences, Kerala University, India. 2) Department of Prosthodontics, A.B Shetty Memorial Institute of Dental Sciences, Nitte University, Mangalore, India 3) Deprtment of Prosthodontics, Pushpagiri Dental College, Peruthurithi, Thiruvalla,Kerala, India
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.