Stress distribution and mechanical strength of NiCrTi welded implant frameworks

Objective: The aim of this study was to assess by photoelastic analysis and through a test of flexural resistance, welding techniques, Laser and TIG (Tungsten Inert Gas) in the manufacturing of NiCrTi implant frameworks.

Method: Three groups were formed with 5 samples each: framework cast in one piece, Laser welded and TIG welded.  The photoelastic model was made with flexible resin, from the transfer impression of a stainless steel matrix with 4 similar implants with regular diameter and hexagonal external connection. The tensions caused by the installation of the frameworks with 20 Ncm torque on the photoelastic model, were analyzed in a circular polariscope and recorded by camera. Later, the resistance test was performed on the mechanical universal testing machine (Model 4411, Instron corp., Canton, MA). The frameworks were positioned in the mechanical testing machine which was set to move 2mm per minute until the occurrence of fracture of the cantilever.

Result: The results were tabulated and submitted to ANOVA and Tukey's test at 5% significance. The results showed no statistical difference of maximum shear stress between any of the techniques used, however, the highest stresses were found along the implants of the right side. The one piece frameworks showed higher fracture resistance when compared to the TIG welded.

Conclusion: The stresses around the implants were similar among the diffferent framework manufacturing techniques and among all evaluated areas. And one-piece casting framework and Laser welded showed better resistance, than the TIG welding techniques.