Screw hole design for single abutments
The anatomy will here be presented transparency. For the design of a screw retained bridge it can be helpful to design the screw channel extended above the actual framework. The reason for this, first of all, is an advantage during the application of ceramic which can't flow into the screw channel holes. The second reason is, that during the fixation of the bridge, the tool is better guided and canting of the the tool effects no chipping of the ceramic, which is a certain risk in that process.
We could specify an offset between the anatomy and "Height"  of the screw channel. You can use slider for that, or put the values in the input field. Values greater than zero makes the screw channel higher than the anatomy, values below zero shrink the screw channel lower than the anatomy.
The screw channel can also be processed using reference points. The circular discs below the reference points are coloured black, which means that the height of the reference points are fixed in relation to the anatomy and the thickness of the screw channel can only be controlled using the “Minimum thickness”  slider.
To add reference points hold “Ctrl” and click on the required area at the top edge of the screw channel. Change to the free mode by clicking it on the discs below the reference points. This then changes the colour from black to green. The reference point can now be moved in all directions also including the height, while taking into consideration the minimum thickness.
In some cases, it may be desirable to design the thickness of the screw channel individually and selectively at one or more reference points. To do this, click on one of the arrows or reference points, hold the mouse key and drag it away from the centre until the screw channel achieves its desired shape. The minimum thickness is determined by the “Minimum thickness slider”. If the screw channel thickness should only be increased in a certain area (mesially, distally, orally or buccally), then click on one of the arrows or reference points and keep “SHIFT” pressed. Then drag the section of the screw channel to the required thickness.
|Further useful functions are available. For this reason another reference point  appears in the middle of the screw channel, which enables controlled adjustment of the height. It moves all reference points that have been switched to the free mode.
The height of the screw channel can be fixed to the anatomy by clicking the “Anatomy” field. If a reduced restoration has been created, the height can also be fixed to the restoration by click the “Framework” field.