The aim of this study was to assess the effect of different plasma arc welding parameters on the flexural strength of titanium alloy beams (Ti-6Al-4V). Forty Ti-6Al-4V and 10 NiCr alloy beam specimens (40 mm long and 3.18 mm diameter) were prepared and divided into 5 groups (n=10). The titanium alloy beams for the control group were not sectioned or subjected to welding. Groups PL10, PL12, and PL14 contained titanium beams sectioned and welded at current 3 A for 10, 12 or 14 ms, respectively. Group NCB consisted of NiCr alloy beams welded using conventional torch brazing. After, the beams were subjected to a three-point bending test and the values obtained were analyzed to assess the flexural strength (MPa). Statistical analysis was carried out by one-way ANOVA and Tukey's HSD test at 0.05 confidence level. Significant difference was verified among the evaluated groups (p<0.001), with higher flexural strength for the control group (p<0.05). No significant differences was observed among the plasma welded groups (p>0.05). The NCB group showed the lowest flexural strength, although it was statistically similar to the PL 14 group (p>0.05). The weld depth penetration was not significantly different among the plasma welded groups (p=0.05). Three representative specimens were randomly selected to be evaluated under scanning electron microcopy. The composition of the welded regions was analyzed by energy dispersive X-ray spectroscopy. This study provides an initial set of parameters supporting the use of plasma welding during fabrication of titanium alloy dental frameworks.

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Manufacturing of metal-free ceramic restorations become possible thanks to the emergence of reinforced ceramics and was consolidated with the development of adhesive materials and vitreous ceramic, allowing restorations adhesion to the dental structure. Lithium dissilicate-based ceramic offers features like, luting agent adhesion, resistance and optical effect, to be used without covering ceramics or thin restorations, maintaining their characteristics. The first ceramic systems were based on the development of infrastructure materials, replacing the metal, with increased reinforced crystalline phase which associated with the roofing porcelain can provide excellent aesthetics results without compromising the mechanical performance indispensable to restoration clinical longevity. Thus, we can perceive the importance of knowledge and planning of the steps to be followed in the process of ceramic restorations adhesion. The careful definition of protocols for the processes of moisture isolation, substrate preparation and restoration for the adhesion process are fundamental for clinical procedures to have reduced risk.

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