New casting process for ti dental applications : the protection efficacy of a ceramic coating.

Informations projet

CATIPRO

N° de convention de subvention: G5ST-CT-2001-50140

Projet clôturé

Date de début 1 Janvier 2002

Date de fin 31 Mars 2004

Financé au titre de

• Programme for research technological development and demonstration on "Competitive and sustainable growth 1998-2002"

Coût total € 1 669 980,00

Contribution de l’UE € 834 985,00

Coordonné par

G.VOULDIS TITAN DENTAL LTD PTY
Greece

Livrables

2.Spray-dried zirconia fully stabilized powder led to very good quality coatings that seem to provide good protection to Ti leading to very smooth surface after casting

From the analysis of the results it is obvious that the mean values of the flexural strength of the zirconia-yttria protected titanium specimens, which were coated by Duceratin Plus and Noritake ultra low fusing dental porcelains appeared significantly higher (29.70 and 28.40 respectively) values than those which were cast by using magnesia investment material (22.40 and 23.10 respectively). Mean values of the third porcelain (Vita Titan Keramik) did not appear any statistically significant difference (33.73 and 34.30 respectively). A Scanning Electron Image accompanied with a Scanning Line for elements Ti, O, Zr, Y, P and Si revealed no entrance of Phosphorous and Silicon elements, within the mass of the casting from the phosphate-bonded investment material (Fig 6). On the opposite Magnesia investment material, although it does not contain silicon and phosphorous it produces inferior metallurgical phases, not the optimum of the metal-ceramic bonding. A second observation is that Vita TitanKeramik showed the best mean values (the higher flexural strength), probably due the stronger bonding agent of this porcelain.

The casting parameters were optimised and the defects origin identified during casting. Based on these results, suggestions for limiting the problems were made

Concerning the Ti castings preparation procedure for the application of the dental porcelain it was shown that the surface roughness is significantly depended on grain size and applied pressure during sandblasting but remains unaffected of incident angle. The surface roughness of cp Ti casting is increased by: a) increasing the mean size of alumina grains and b) increasing the applied pressure (and thus the velocity of particles) of sandblasting machine when 100 and 250µm powders are used A study was also undertaken to optimise the casting parameters and to identify the defects origin during casting. Based on these results, suggestions for limiting the problems were suggested. In more detail with an indication of the key experimental results, the conclusions are: The defects such as lack of filling and dimensional errors are caused mainly by a bad design of the feeding. In general, we have been able to observe that it is more critical in the Ciclarc II machine from Morita, whose process of filling and solidification is by differential pressure) than in the Easyti machine from Manfredi, in which the process of filling and solidification is by centrifugation, making easy the filling of the titanium melted).