The production process of prosthetic restorations runs in two stages. In the first stage, the prosthetic foundation is produced of metal

alloys. In the second stage, a facing material is applied on the produced element. In both stages, the wettability is significantly important,

as well as the free surface energy relating to it. The quality of the obtained cast depends on the surface phenomena occurring between the

metal alloy and the material of which the casting mould is made. The performed examinations also point to a relation between the ceramics

joint and the base, depending on the wetting angle.

The aim of the presented paper was to examine influence of the composition of a Ti(C,N)-type coating on bases made of the Ni-Cr

prosthetic alloy on the wettability and the surface free energy.

The test material were disks made of the Ni-Cr alloy with the diameter of 8 mm. The disks were divided into five groups, which were

covered with Ti(C,N) coatings, with different amounts of C and N in the layer. In order to determine the surface free energy (����), the

wetting angle was measured. Two measure liquids were applied: distilled water and diiodomethane.

The obtained results of the measurements of the water-wetting angles suggest that together with the increase of the ratio of nitrogen to

carbon in the Ti(C,N) coating, the surface hydrophobicity increases as well. In all the samples, one can see a large difference between the

energy values of the polar and the apolar components. The high values of the polar components and the low values of the apolar ones make

it possible to conclude that these surfaces exhibit a greater affinity to the polar groups than to the apolar ones.

On the basis of the analysis of the surface free energy, one can state that covering the alloy with Ti(C,N)-type coatings should not decrease

the adhesion of the ceramics to the alloy, whereas TiC coatings should lead to the latter’s improvement. Due to their hydrophilicity, TiC

coatings should decrease the adhesion of bacteria to the surface and hinder the formation of a bacterial biofilm.

The aim of this paper was to study the corrosion behavior of Nickel – Base – Dental Alloys in Ringer biological fluid. The Nickel base alloys are widely used for medical purposes, especially for prosthetic works in the field of dentistry. The applied electrochemical methods used for corrosion investigations are Open Circuit Potential, Linear Polarization during time of immersion in order to calculate the polarization resistance and corrosion rate. Potentiodynamic Polarization diagrams was performed to appreciate the passive domain. Ni-Cr Ugirex alloy show a better corrosion resistance in Ringer solution which will be reflected in a longer life of the dental structures made with this alloy as compared to the Ni-Cr Ducinox alloy, which will result in dental structures with a shorter lifespan.
The electrochemical studies has shown that the alloy have a corrosion behavior similar to a passivating alloy, displaying an extensive passivity area due to formation of an oxide film.

The results of castability and structures researches of two nickel base alloys - Ceranium CN and Magnum AN applied on casting of the crowns and dental bridges are presented. Studies were carried out on the alloys cast under the centrifugal force to the moulds made by the lost wax method using production line of ROKO. Having regard to a specific technology of casting and possibility of ROKO production line, to the estimation of alloys castability a spiral test was adjusted with a 0,8 mm and a 2,5 mm diameter of test casting. Measuriements executed on a 20 test castings allowed to establish, that castability of Magnum AN alloy was 65 % greater than castability of Ceranium NC alloy. The results of thermodynamics calculations of the equilibrium and nonequilibrium crystallization (Scheil model) of the investigated alloys are presented too. The characteristic temperatures of phase transformation and forecast phase composition of alloys for both kind of crystallization were calculated. It is established after structural supervisions, that the investigated alloys crystallize in dendryte form and in centrifugal casting conditions have cooling rate sensivity and inclination to texture structure forming in outmost layer of casting. Phase composition of alloys corresponds to the results of thermodynamics calculations of the nonequilibrium crystallization conditions.