Bond strength of three porcelains to two forms of titanium using two firing atmospheres.
BACKGROUND
Problems with casting and porcelain bonding are encountered when titanium is used in metal-porcelain restorations. The oxidation characteristics of titanium are the main problem. The bonding mechanisms in titanium-porcelain systems are complex and poorly understood.


OBJECTIVE
An in vitro investigation was performed to evaluate the bonding characteristics of 3 titanium-porcelain systems in various firing conditions.


METHODS
This study evaluated the bonding strength of 3 commercial titanium porcelains fired in a vacuum and in an argon atmosphere to cast and noncast commercially pure titanium, using a 3-point bending test according to DIN 13927 and SEM with energy-dispersive spectrometry analysis. The results were compared with an Ni-Cr alloy and a conventional porcelain that was chosen as a control.


RESULTS
The Ni-Cr-conventional porcelain system fired in an argon atmosphere had significantly higher bond strength than the other systems (P<.001). In addition, the bond strength of the titanium-spark erosion-Noritake Ti22 combination, fired in an argon atmosphere, was significantly higher than the other titanium-porcelain groups, which had results similar to those obtained with the vacuum-fired, Ni-Cr-conventional porcelain and argon-fired titanium-cast-Noritake Ti22 groups. On the other hand, the bond strength of the titanium-TiBond and titanium-Vita Titankeramik groups was below the lower limit value in the DIN 13927 standard for the 3-point bending test (25 MPa). Although the results of the Duncan multiple range test showed that firing in an argon atmosphere did not affect the bond strength of the titanium-Vita Titankeramik groups, the titanium-spark erosion-TiBond group, or the titanium-cast-Noritake Ti22 group, argon firing improved the bond strengths of the Ni-Cr-conventional porcelain group, the titanium-cast-TiBond group, and the titanium-spark erosion-Noritake Ti22 porcelain group. It was also found that there were no significant differences between the bond strengths of cast and non-cast titanium groups; an exception was the titanium TiBond groups in which the porcelain was fired in a vacuum.


CONCLUSIONS
The oxide layer produced on titanium was considered to have a potentially adverse effect on titanium-porcelain bonding. It was also concluded that matching the titanium-porcelain combination is the main determinant for optimal bonding. Firing in an argon atmosphere that limited the oxidation of titanium improved the titanium-porcelain bond in some of the groups.
Atsü
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S
Department of Prosthodontics, Oral Health Center of Ankara, Turkey.
Berksun
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D000704:Analysis of Variance; D002858:Chromium Alloys; D003722:Dental Alloys; D001840:Dental Bonding / Q000379:methods / Q000706:statistics & numerical data; D003735:Dental Casting Technique; D003776:Dental Porcelain; D008422:Materials Testing / Q000379:methods / Q000706:statistics & numerical data; D008855:Microscopy, Electron, Scanning; D011897:Random Allocation; D013499:Surface Properties; D013718:Tensile Strength; D014025:Titanium
D002858:Chromium Alloys; D003722:Dental Alloys; D003776:Dental Porcelain; D014025:Titanium