Material degradation in implant-retained cobalt-chrome and titanium framworks

The purpose of the study was to estimate in vitro material degradation in implants and cobalt-chrome or titanium frameworks, before and after exposure to artificial saliva. Four full-arch implant frameworks were fabricated according to the Cresco™ method (Astra Tech AB, Mölndal, Sweden), two in a cobalt-chrome alloy and two in commercially pure (CP) titanium. They were cut vertically, and the three central sections of each framework were used. Element leakage into an artificial saliva solution was observed with mass spectrometry. Before artificial saliva exposure, three Brånemark System(®) implants (Nobel Biocare AB, Gothenburg, Sweden) were screw-retained to cobalt-chrome sections, and three to titanium sections. The contact surfaces with the implants of the framework sections and the corresponding surfaces of six implants were examined with optical interferometry before and after exposure to artificial saliva to evaluate material degradation. Conventional descriptive statistics were used to present the mass spectrometry and interferometry data. One-way anova and Dunnett's T3 post hoc test were used to identify and study differences between the groups. To highlight changes within the groups, the Student's t-test was used. The significance level was set at 5%. There was significantly more leakage of cobalt elements than of titanium and chrome (P < 0·05). After saliva exposure and framework connection, the implants roughened (P < 0·05). The titanium frameworks were generally rougher than the cobalt-chrome frameworks, both before and after saliva exposure (P < 0·05). The findings in this study suggest active material degradation processes for both implants and framework materials