Ikuya Watanabe, DDS, PhD,(a) Jennifer Chang, BS,(b) and Yvonne Chiu, BS(b)
(a)Department of Biomaterials Science, Baylor College of Dentistry, Texas A&M University System Health Science Center, and (b)Baylor College of Dentistry, Texas A&M University System Health Science Center, Dallas, TX, USA
Purpose: This study examined the amount of distortion of prosthetic metal frameworks caused by laser welding when the welding pattern and the method of fixing the ends of the specimens in the jig were varied during the welding process.
Materials and Methods: Wax plate patterns (0.5×3.0x10 mm) were prepared to cast the Co-Cr plates. After the welded surfaces (3.0×0.5 mm) were polished with No. 600 SiC paper, the two plates were matched and welded with a Nd:YAG laser at constant welding parameters. The specimens were welded unilaterally or bilaterally with either three or five spots as follows: two ends fixed unilaterally (A) or bilaterally (AA), one end fixed unilaterally on one surface (B), two ends fixed on one surface with the opposite surface fixed at one end (AB), or one end fixed bilaterally on two surfaces (BB). The bilateral specimens were made by inverting the unilateral specimens and welding them on the other side opposite the first weld. Distortion was determined by measuring the gap from the jig base at one end of the plate after each welding application. The results (n=3) were analyzed using a two-way ANOVA and Tukey’s HSD (p<0.05).
Results: Compared to the two-end fixed specimens (A and AA), the specimens fixed at only one end on either surface (B, AB, and BB) had significantly more distortion. When both ends were fixed (A and AA), more distortion appeared to occur for three-spot welding compared with five-spot welding.
Conclusion: The method of fixing the ends of the specimens in the jig significantly affected the amount of distortion for both the three- and five-spot welding patterns. (Int Chin J Dent 2005; 5: 47-51.)
Key Words: cobalt-chromium, distortion, laser welding, metal framework.