Effect of finishing process on the surface quality of Co-Cr-Mo dental alloys

Preparatory procedures for the material have a sign ifica t influence on the surface stereometry of the material. This study investigated the effect of the electropolishi ng process on the surface quality of metallic prost hetic constructions based on Co-Cr-Mo alloys. It has been found that the process of electropolishing prevents to excessive developm ent of the surface of a material and consequently improves surface qualit y.


Introduction
Biomedical engineering is an interdisciplinary field of knowledge whose main goal is the constant development of medical techniques.An important problem frequently considered as negligible is the quality control of each component in the manufacturing process of prosthetic work and influence of its properties on fitting to the patient's mouth (BIAŁAS A. 2008; PANEK H., BARZYK M., NAWROT P., NAPADŁEK P., ŚPIKOWSKA-SZOSTAK J. 2009, HĘDZELEK W., URBANEK M., WASIAK W. 1998/1999, JOSEPH D. BRONZINO 2000).Regardless of the type of product (elements of prosthetic restorations) the primary factors in achieving a high quality are: technical aspects, material selection and quality of service (DRAGO C., PETERSON T. 2014, KOCHANEK-LEŚNIEWSKA A., CIECHOWICZ B., WOJDA M., MICHALIK R. 2012., POLAK A.2015).During the production of the final product a number of inconsistencies may occurring the production process; from bad design due to the use of improper methods during the manufacturing process, to the use of different methods of finishing treatment (mechanical or chemical treatment) (KEDICI S. P., AKSUT A. A., KILIÇARSLAN M. A., BAYRAMOGLU G., GOKDEMIR K. 1998, KHAMIS E., SEDDIK M., 1995, LIN M. H-Y., BOWERS B., WOLAN J.T., CAI Z., BUMGARDNER.2008, MAKOWSKA J. D. WALCZYŃSKA A. 1990).
The aim of this study is to demonstrate the relationship between the use of the electropolishing process and the quality of the surface layer of prosthetic construction.

Experimental
For research the dental alloybeen used.This type of alloy has chemical composition Co 59,0 Cr 25,5 Mo 5,5 W 5,0 and a low content of elements such as Ga (3.2%) Nb, 1%) is an alloy without Ni and designed to perform metal structural work (i.e.partial dentures).
As the most famous process often used in the final treatment metallic construction for s and cleaning surface, replacing the traditional mechanical processing is electropolishing K.P. 2005), the tested sample has been electrolytic polishing process.
Parameter determining the speed of the electropolishing process (chemical processing) include current density, in this study, the current density was i = 0.25A/cm 2 .The working solution was a glycol aqueous solution of sulfuric acid and hydrochloric acid for a constant temperature of 30 and the process was continued for measurement results were compared to a sample (Table 1).
The paper presents the most representative results of surface topography casting on Cr-Co-Mo.In the paper the roughness analysis is performed -surface roughness measured with pin profilometer (Taylor Hobson), measuring section 4 mm for each sample.To better illustrate the results of surface roughness the 3D images with optical microscope Olympus (with EPI overlay) were carried out.

Results
In Figure 1 the determined surface profiles for sample 1(non-treated) and 2 (after electropolishing 0.25 A/cm 2 ,t = 10 min) are presented.With respect to the profilometry roughness measur ness parameters recorded during ana Table 2.For comparison a set of the parameters i.The confirmation of the results are 3D images of studied surfaces.Pictures were taken with an optical microscope with EPI overlay at 50X magnification.As a result of electropolishing, surface of the sample 2 is significantly smoother (Fig. 3).

Summary and conclusions
After the electropolishing process, the roughness parameters are significantly lower than those of the starting sample.Microscopic examination confirmed that this process contributes to the smoothing surface of the prosthetic construction and improve product quality.

Fig. 1 .
Fig. 1.Analysis of the local areas (profile) of dental alloy Collado CC: a) sample 1 without electropolishing; b) sample 2 after ele tropolishing process Source: own study Fig. 2. Change of Ra, Rz and Rt parameters values for dental alloyCollado CC: a) sample 1 without electropolishing; b) sample 2 after electropolishing process Source: own study f a c e b e f o r e e l e k t r o p o l is h in g p r o c e s s P a r a m e t e r s R t R z P a r a m e t e r s s u r f a c e a f t e r e l e k t r o p o l i s h i n g p r o c e s s2.Change of Ra, Rz and Rt parameters values for dental alloyCollado CC: a) sample 1 without electropolishing; b) sample 2 after electropolishing process

Table 1 .
Determination of Collado CC based Cr alloy samples

Table 2 .
Selected surface roughness parameters Collado CC based Cr Parameters

Table 2 .
Selected surface roughness parameters determined for Collado CC based Cr-Co-Mo alloy samples