Surface roughness and fatigue performance of commercially pure titanium and Ti-6Al-4V alloy after different polishing protocols

• Published in: The Journal of prosthetic dentistry 2005-04, Vol.93 (4), p.378-385
• Main Authors: Guilherme, Aderico Santana, Henriques, Guilherme Elias Pessanha, Zavanelli, Ricardo Alexandre, Mesquita, Marcelo Ferraz
• Format: Article
• Language: English
• Subjects: Dental Alloys - chemistry; Dental Polishing - methods; Dental Stress Analysis - instrumentation; Dentistry; Electrolysis; Humans; Hydrofluoric Acid - chemistry; Materials Testing; Microscopy, Electron, Scanning; Nitric Acid - chemistry; Saliva, Artificial - chemistry; Stress, Mechanical; Surface Properties; Titanium - chemistry
• ISSN: 0022-3913; 1097-6841
• DOI: 10.1016/j.prosdent.2005.01.010

Surface quality of cast metal is directly related to service performance under fatigue stress. Surface heterogeneities resulting from either finishing or polishing processes or by corrosive agents such as fluoridated solutions, can negatively affect fatigue life. Cast titanium frameworks are difficult to polish, and an accepted polishing protocol has not been established. This study evaluated and compared surface roughness of cast commercially pure titanium (CP Ti) and Ti-6Al-4V alloy submitted to conventional or electrolytic polishing, correlating the results with corrosion–fatigue strength testing performed in artificial fluoridated saliva. Specimens were also tested in air at room temperature to evaluate the effectiveness of the corrosion-fatigue test model. For each metal, 40 dumb-bell–shaped rods, 2.3 mm in diameter at the central segment, were cast. Conventional polishing was performed on 20 specimens of each metal following the manufacturer's instructions. A source of continuous electrical current was used for electrolytic polishing of the other 20 specimens of each metal, which were immersed in an electrolytic solution containing 5% fluoridric acid, 35% nitric acid, and 60% distilled water. Surface roughness, Ra (μm), was measured with a profilometer, and fatigue tests were carried out with a universal testing machine using a load 30% lower than the 0.2% offset yield strength. After failure, the fractured surfaces were examined using scanning electron microscopy. Surface roughness means were analyzed with a 2-way analysis of variance and the Tukey multiple comparisons test (α=.05). Electrolytic polishing (0.24 ± 0.05 μm) provided significantly ( P