Surface structure and corrosion behaviour of dental alloys treated by Micro-Finishing

Recently a new method of surface finishing has been introduced in dental technology: It is a micro-dry blasting method, which works with two different blasting media. The first one is to reduce surface near layer, containing microstructural defects, the other one results in a surface strengthening by shot peening. The aim of the study was to verify the improving effect of this blasting technique on dental alloys and to investigate the corrosion behaviour of dental alloys after using micro-blasting. For this reason a high gold- and cobalt-base alloy and Titanium were tested as follows:Samples of the materials were treated by Micro-Finishing with an abrasive and spherical blasting medium separate and in combination. The finished surfaces were characterised by light-and scanning-electron-microscopy (SEM) and analysed profile graphically (RZ). The microhardness (MHV 0,02) was tested on transverse sections in distances of 10, 20, 100 µm and in the middle of the sample. Additionally electro-chemical tests were made in a 0,9% sodium chloride solution (pH=7,4). The resting potentials were recorded and the breakdown potentials evaluated. Using the micro-blasting technique enables an improvement of the surface structure by smoothing and strengthening the surface and increasing their microhardness. The corrosion behaviour shows a higher passivation. Keywords: surface finishing, shoot peening, dental alloy, precious dental alloys, non precious dental alloys, titanium, metallographic structure, corrosion behaviour, profile graphic analyses