Welding the separate bridge
There may be various reasons for separating a cast or milled bridge.
However, this is irrelevant in this context and not the subject of our consideration.
Depending on the situation, a bridge can have different fitting states on a model after separation.
Before any joint welding can begin, the separated parts must be in contact with each other.
A bridge is often separated in the area of a connector; depending on the work, this could also be done across a crown or through a pontic.
We will limit ourselves here to the connector area, as shown in the linked video at the end of this article.
Ideally, the welding area is prepared for a so-called X or DV seam (Fig. below).
In rarer cases, the parts will already be in full contact after cutting, and you may be inclined to weld the parts together directly, although we do not recommend this.
The penetration depth of the weld will most likely not be sufficient for a reliably stable connection, or you will have to work with such high welding parameters that distortion of the bridge can hardly be avoided.
In this case, even if this may seem awkward at first glance, we recommend grinding the joint in a circular V-shape to achieve a situation similar to the schematic diagram above.
If the separated parts have a larger gap between them, a contact point must first be applied from both sides using suitable welding wire as explained in the article Applying welding wire (CTE topic).
This technique should also be used to achieve an initial situation as shown in the illustration above.
If the parts are now touching, we recommend that you first apply a temporary fixation,
This will be removed again at the end of the weld.
Two welding points per segment with low welding parameters are completely sufficient for this fixation.
This counteracts possible distortion and keeps the parts in the correct position.
A first connection welding point can now be set centrally, in order to then successively build up the connector 
It is advisable to always place the first welding points diagonally opposite each other according to the wheel nut principle in order to strategically compensate for any stresses that may occur.
By fixing the bridge in place, it can be removed from the model at any time for welding or checked on the model for correct fit.
At the start of welding with the X-seam situation, the welding geometry 
The contact point at the deepest point of the connector is best reached with a freshly sharpened electrode, with a blunt electrode it is difficult or impossible.
Later, to complete the desired contour, you can switch to the welding geometry 
At the end of welding, the auxiliary structure can be easily removed and finished with the rest of the work.
Note: If the restoration is to be veneered with ceramic at a later stage, the area should always be ground over with a carbide bur if the electrode is accidentally welded on in order to prevent the inclusion of tungsten particles and subsequent chipping of the ceramic.
Video: Bridge welding
You can also watch the bridge welding process in this application video at .