Study of corrosion of combinations of titanium/Ti-6Al-4V implants and dental alloys.
Metal ions released in 1% lactic acid solution from combinations of titanium fixtures with superstructures made of dental precious metal alloys (dental alloys) and titanium and differences based on the fixing method were investigated. In combinations of titanium with dental alloys, the level of Ti release was influenced by micro-structure of titanium: it was lower when the grain size was smaller. In titanium-titanium combinations, differences in the micro-structure of metal also markedly influenced the dissolution: the level of release increased when the micro-structure of titanium was different. The Ti and V release levels were higher in combination with titanium alloy and titanium than with titanium alloy and dental alloys. Regarding the superstructure-fixture fixing method, the level of Ti release was significantly lower in cement than in direct fixation. (+info)
Dental students' ability to evaluate themselves in fixed prosthodontics.
Self-evaluation is an essential skill for dental professionals for lifelong learning and improvement through the course of their careers. Students taking a preclinical fixed prosthodontics course were studied. The students were asked to assign themselves a grade upon completion of their timed preparation examination (teeth preparations and provisional restorations), and these were compared with grades given by the faculty. The poorer performing students tended to be less critical with their examination and to overrate their performance whereas the higher performing students were more critical of themselves and underrated their performance. (+info)
Collarless metal ceramic restorations to obscure the umbrella effect.
Surface characterization and bond strengths between Ti-20Cr-1X alloys and low-fusing porcelain.
This study evaluated the bond strengths between experimental Ti-20Cr-1X (X=Nb, Mo, Fe, Zr) alloys and porcelain (Duceratin). The results of this bond strength testing indicated that all the Ti-20Cr-1X alloys exceeded the lower limit value in the ISO 9693 standard for the 3-point bending test (25 MPa), and were all higher than that of commercially pure titanium (c.p. Ti). The coefficient of thermal expansion (CTE) values of all Ti-20Cr-1X alloys were higher than that of c.p. Ti, and this result of a closer match between CTEs shows the fact that the Ti-20Cr-1Mo alloy had a significantly higher bond strength than both the other Ti-20Cr-1X alloys and c.p. Ti. (+info)
A comparison of the marginal adaptation of cathode-arc vapor-deposited titanium and cast base metal copings.
Ion release from metal-ceramic alloys in three different media.
The aim of this in vitro study was to assess the effect of pH changes on ion release of metal-ceramic dental casting alloys. Samples from four commercially available alloys (Wirobond C, Wiron 99, Rematitan CP-Ti grade 1, and PontoStar) were prepared and polished. Ion release of alloys subjected to three different pH media (artificial saliva of pH 2.3, pH 6.5 and 0.9% saline solution of pH 7.3) for periods of 7, 15, 30, and 60 days were assessed by means of atomic absorption spectroscopy. Microscopic changes on surfaces of metallic samples before and after immersion were compared by scanning electron microscopy. ANOVA was used for statistical analysis of results. For all ions, pH and period interactions were statistically significant: highest amount of ion release occurred after 60 days of immersion regardless of pH value. For every alloy, ion release results were highest in artificial saliva of pH 2.3 and lowest in 0.9% saline solution. It was concluded that ion release from alloys was pH-dependent. (+info)