On Superplastic Forming of Pure Titanium for Constructing Dental Implants

Abstract

A newly designed dental implant (artificial tooth root) has been developed for the cases where ordinary osseointegrated implants cannot be applied because of the insufficient born quality or quantity. Superplastic forming enables to produce such dental implants from a pure titanium piece. A pre-machined pure titanium piece was sandwiched in between a pair of concavo-covex ceramic die that was formed directly from an image model of maxilla (upper jaw born), then superplastically formed into a dental implant. Therefore the implant has the tailor-made shape for individual patients. Superplastic forming was performed at 1()93K, 0.1mm/min of deformation rate. and 10 -3 - 10 -4 Pa of atmosphere. The forming procedure was finished after the load value reached and was kept at 100kgf for 3() minutes in order to ensure the detailed shape. Implantation to a patient had caused no trouble for more than 4 months after the operation. Besides the born quality or quantity, several other problems exist in the conventional osseointegrated implants (Branemark implant, for instance). In some cases, the bonding strength between the implant and the jaw born is not sufficient enough because the bonding is caused only by mechanical interlocking. In order to overcome this problem a new techniquc for getting a bioactive surface has been developed by the authors. That is hydroxyapatite-granule implantation on the titanium surface by using superplastic deformation, On applying this technique to the conventional dental implants, hydroxyapatite granules must be fixed on the cylindrical or screw-shaped surface of the implants. If the screw shape implants can be superplastically formed directly from a titanium pin, that enables the hydroxyapatite-granule implantation on the surface by operating granule implantation and shape forming simultaneously. In order to realize such implants, superplastically forming of a pure titanium pin into a screw shape was examined. As a result, it was found that the same mold forming method used for producing dental implants was also applicable for screw shape forming. A half-split mold along the screw axis was directly produced from the original screw.