When securing a dental prosthesis to the jaw of a patient, it is commonly known to attach a superstructure to osseointegrated dental implants. However, since the position and angle of the dental implants vary greatly from patient to patient, the use of angled distances is common These distances are placed upon the dental implant, and the superstructure is then most often cemented to the distances, since it is difficult to screw retain the superstructure to such distances. However, when using separate distances, these will inevitably extend—at least to some extent—in the axial direction of the dental implant. It is then often very difficult or even impossible to apply the superstructure on such distances, since the application of the superstructure calls for a substantially parallel arrangement of the distances. Also, the mounting process when using such distances is very complicated and cumbersome, since a vast number of different distances must be tested on the implants, to find the needed match. Also, interfaces between the distances and the superstructure are hygienically bad.
In order to model the desired position of the screw channel mouth in screw retained superstructures, it is known to position acrylic tubes on a model of the jaw of a subject. The model shows the position of the osseointegrated dental implants, and the acrylic tubes are placed at these positions and bent to the desired curvature before a mould is formed, based on the bent acrylic tubes. Subsequently, separate seat support cylinders are planarized together with the casted superstructure, whereafter the separate screw member seat support cylinders are welded onto the casted superstructure.
However, it may be hard to bend the acrylic tubes correctly. Bending the tubes to the desired curvature is tedious and the tubes may flex after bending, which may result in a mould with erroneous angles. Furthermore, it is only possible to obtain bent screw channels, following a curvature, whereby the angle between the central axis of the mouth of the attached screw seat and the central axis of the screw channel mouth is limited to angles less than 17 degrees.
Several screw channel directing devices for use in dental superstructures have been designed, but they may all suffer from certain different disadvantages. There is thus a need for an improved screw channel directing device, at least for demanding uses.