# Carbon Coatings Deposited on Prosthodontic Ni-Cr Alloy
###### Abstract  
The study discusses the results of investigations conducted on carbon coatings applied on a prosthodontic alloy Ni-Cr. Carbon coatings with the thickness of about 1000 nm were deposited by means of the RF PACVD method with a titanium interlayer applied by magnetron spray dispersion. The coatings underwent microscopic examinations, as well as structural tests with the use of Raman spectrometry, investigations of mechanical properties, adhesion and corrosion tests; also, the bacterial adhesion to the sample surface was determined. It can be inferred from the performed studies that the obtained carbon coatings exhibit mechanical properties which allow them to be used for prosthodontic elements. The coatings' adhesion to the metallic substrate made of Ni-Cr alloy equaled about 150 mN. The examined coatings clearly improve the corrosion resistance and reduce the number of bacteria adhering to the sample surfaces. Taking all this into account, it can be stated that carbon coatings can be potentially applied to protect metal prosthetic restorations.  
prosthodontic alloys; diamond-like carbon; corrosion; mechanical properties; bacterial adhesion Article  
Carbon Coatings Deposited on Prosthodontic Ni-Cr Alloy  
those areas of the mucous membrane. The microorganisms present in the oral cavity can cause corrosive destruction (MIC--microbially influenced/inducted corrosion) of metal prosthetic elements, implants, etc. [11; 12]. This phenomenon refers even to titanium and its alloys, which are commonly treated as very well resistant to corrosion [13]. Therefore, an important issue is not only improvement of corrosion resistance but also minimization of the possibility of a biofilm formation.  
Despite their many flaws, metals continue to be used, as, presently, there are no other materials which would possess comparable properties. The occurrence of an organism reaction very often refers to non-precious metal alloys (cobalt-chromium and nickel-chromium). These alloys do not demonstrate sufficient corrosion resistance in the oral cavity environment. However, due to economic reasons, they are commonly used in stomatology as a cheap alternative for the expensive precious metal alloys. A similar behavior is demonstrated by zinc, copper and silver as components of amalgams. Due to a significantly lower corrosion resistance of these metals, the latter cause a much stronger biological response of the body compared to the precious metal alloys. In order to improve their corrosion resistance, various types of surface modifications are applied, which make it possible to increase the biological tolerance of these alloys. The usual method involves coating with different layers, such as oxides, carbides or metal nitrides [14; 15; 16; 17; 18]. These coatings make it possible to improve the corrosion resistance and biocompatibility, and they reduce the bacterial adhesion [19; 20; 21]. They can significantly limit the release of metal ions into the surrounding environment [22]. Among the many available methods of coating synthesis, medical applications often involve covering the surfaces with layers deposited from the gaseous phase [15; 23; 24; 25; 26; 27]. One of the most interesting techniques is the application of carbon layers [26; 27]. Carbon is an element which characterizes in good corrosion resistance and biocompatibility. These properties largely depend on the form of the carbon--whether it has a diamond or graphite structure. Studies conducted by many authors show that such coatings have many advantageous properties, allowing their potential use in dental prosthetics [28; 29]. Therefore, covering metal elements with layers containing this element should provide them with good properties in the oral cavity environment.  
The aim of this study was to evaluate the quality of carbon layers deposited on prosthodontic Ni-Cr alloy in RF PACVD reactor equipped with a magnetron using titanium interlayer.