Corrosion Behavior of a Nickel-base Dental Casting Alloy in Artificial Saliva Studied by Weight Loss and Polarization Techniques
Objectives:Corrosion of Ni-Cr base dental alloys in saliva influences their application in prostheses.
Material and methods: Corrosion behaviour of the NiCr alloy was studied using two techniques including weight lossdescribed by corrosion rate (CR) per mil per year (mpy)and potentiodynamic polarizationdescribed by corrosion potential (CP) in mV and current density (CD) in mA/cm2in artificial saliva with different pH.Surface morphology was studied using scanning electron microscopy (SEM). Statistical difference was assessed using one-way ANOVA and post-HOC Tukey-HSD tests with a difference significance of 95%.
Results:In weight loss method,CRwas 71.95±3.40, 17.26±1.03, 8.92±0.35 and 6.93±0.54mpy in pH values of 2.5, 5, 7 and 9, respectively. CR obtained in pH of 2.5 was significantly different with that in other groups, but those obtained in pH of 5, 7 and 9 were not significantly different. In polarization method, CPwere significantly different. CD measured in pH of 2.5 and 5 was significantly different with the rest of pH values. Corrosion rates in pH of 7 and 9 were not significantly different.
Conclusion:The results obtained by both techniques are consistent. Corrosion resistance decreases as pH increases. In more acidic saliva, corrosion rate is greater likely due to the higher dissolution rate of Ni through weak passivation. However, the less acidic saliva leads to formation of more stable passive film on Ni and therefore the dissolution of Ni decreases leading to lower corrosion rates.
Sarantopoulos DM, Beck KA, Holsen R, Berzins DW. Corrosion of CoCr and NiCr dental alloys alloyed with palladium. J Prosthet Dent 2011; 105(1): 35-43.
Supreetha SN, Ravindra K, Murali H. Effect of heat treatment on the corrosion behavior of nickel chromium (wiron 99) alloys. IJDA 2010; 2(1): 90-95.
Matkovic T, Matkovic P, Malina J. Effects of Ni and Mo on the microstructure and some other properties of Co-Cr dental alloys. Journal of Alloys and Compounds 2004; 366(1-2): 293-297.
Wylie CM, Shelton RM, Fleming GJ, Davenport AJ. Corrosion of nickel-based dental casting alloys. Dent Mater 2007; 23(6): 714-23.
Lin HY, Bowers B, Wolan JT, Cai Z, Bumgardner JD. Metallurgical, surface, and corrosion analysis of Ni-Cr dental casting alloys before and after porcelain firing. Dental Materials 2008; 24(3): 378-385.
Geis-Gerstorfer J. In vitro corrosion measurements of dental alloys. J Dent 1994; 22(4): 247-51.
Ameer MA, Khamis E, Al-Motlaq M. Electochemicalbehaviour of recasting Ni-Cr and Co-Cr non-precious dental alloys. Corrosion Science 2004; 46(11): 2825-2836.
Khamis E, Seddik M. Corrosion evaluation of recasting non-precious dental alloys. Int Dent J 1995; 45(3):209-17.
Abey S, Mathew M, Lee D, Knoernschild KK, Wimmer MA, Sukotjo C. Electrochemical Behavior of Dental Implants (CpTi): Influence of pH of Artificial Saliva. J Oral Implantol2014; 40(1): 3-10.
deDeMicheli SM, Riesgo O. Electochemical study of corrosion in Ni-Cr dental alloys. Biomaterials 1982; 3(4):209-12.
Qiu J, Yu WQ, Zhang FQ, Smales RJ, Zhang YL, Lu CH. Corrosion behaviour and surface analysis of a Co-Cr and two Ni-Cr dental alloys before and after simulated porcelain firing.Eur J Oral Sci 2011; 119(1): 93-101.
Wataha JC, Lockwood PE, Khajotia SS, Turner R. Effect of pH on element release from dental casting alloys. J Prosthet Dent 1998; 80(6): 691-8.
Fontana MG. Corrosion Engineering, 2nd Edition. USA: McGraw-Hill;1986.
Molina C, Nogués L, Martinez-Gomis J, Peraire M, Salsench J, Sevilla P, Gil FJ.Dental casting alloys behaviour during power toothbrushing with toothpastes of various abrasivities. Part II: corrosion and ion release. J Mater Sci Mater Med. 2008;19(9):3015-9.
Barão VA, Mathew MT, Assunção WG, Yuan JC, Wimmer MA, Sukotjo C. Stability of cp-Ti and Ti-6Al-4V alloy for dental implants as a function of saliva pH - an electrochemical study. Clin Oral Implants Res 2012; 23(9): 1055-62.
Mareci D, Nemtoi G, Aelenei N, BocanuC.The electrochemical behaviour of various non-precious Ni and Co based alloys in artificial saliva.Eur Cell Mater 2005; 8(10):1-7.