The bond strength of porcelain fused to cast and wrought titanium surfaces was calculated from fracture loads in a 4‐point bending test. Two different porcelain were applied (O'Hara and Duceratin). The surface of Ti‐cast specimens was treated in two different ways to produce variations in the impurity level before porcelain veneering. Microhardness measurements as well as scanning electron microscopy with EDX analysis were conducted. The results showed no significant difference in bond strength between the two porcelains. Nor was any difference in bond capacity found between thoroughly blasted castings and wrought titanium. Significantly lower bond strengths were observed for lightly blasted specimens and for specimens treated with Gold bonding agent. Impurities in the surface region of the castings were found to be due to contact with the investment during solidification. This indicates that a thin surface layer (50–100 μm) of the casting should be removed before firing of the porcelain.

No abstract

Plasma spraying is a technique currently used in the production of HA-coated titanium implants. These coatings have been shown to be porous; they dissolve and have a weak bond to the substrate. The long-term interface strength has been questioned in particular. The aim of the present work was to produce HA coatings without the shortcomings of those produced by plasma spraying. Hot isostatic pressing (HIP) at 850 degrees C and 1000 bar with no holding time was applied for this purpose. Initially, the HA powder was mixed with water and air sprayed on the Ti substrate. The Ti specimens were then cold-pressed, enclosed by a protective Pt foil, and encapsulated in an evacuated glass ampulla. Subsequent to HIP, the glass and the Pt foil were removed. These coatings were denser than those produced by plasma spraying. The bonding was measured to be > 62 MPa, which is considered to be satisfactory. The structure of the coating was checked by X-ray diffraction and IR spectroscopy, and was found to correspond to that of HA. Some cracks were observed in the coating running predominantly vertical to the surface. Whether these are acceptable has to be verified by in vivo experiments.

No abstract

– Ti has a strong affinity to elements like O, N, and C. During melting a non‐reacting crucible and vacuum and/or Ar‐gas protection therefore have to be used. If the impurity content becomes too high, the material turns hard and brittle. In the present work vacuum/Ar‐pressure casting of crowns has been carried out at different air pressure levels. Recording of hardness on cross‐sections of the castings and the degree of mold filling show that an air pressure level < 1 torr in the melting chamber and < 10 torr in the mold chamber is sufficient to obtain sound castings of a small size like a crown.