Repairing a broken clasp of a cast partial denture

• Where on the prosthesis is the clasp broken?
• What type of clasp is it, e.g. a molar support clasp with support or canine with a strong undercut and large travel?
• Is it a fatigue fracture, accident, casting defect, design fault, … ?

• What is the desired end result of the repair?

These questions should be clarified in advance with the practitioner or the patient, from a functional and, if necessary, an aesthetic point of view.

Not in all cases where a clasp fragment is still available, possibly even with a good fit, should it simply be welded back on. A maxillary canine clasp, e.g. for a tooth with a large undercut, which was placed as high as possible in the invisible area for esthetic reasons and is broken at the shoulder of the clasp, should not be welded back on without further ado, as the welded connection would not have the same elasticity as the rest of the structure. It may not be possible to simply reinsert this work or remove it later without difficulty for the patient. The risk of a new fracture is high.

Alternatively, the clasp could be shortened and thus placed slightly higher (i.e. towards the occlusal) if there is nothing to prevent this from an esthetic point of view. A curved clasp could be welded on temporarily. If it is a new restoration that is to be restored to its original state, it would be conceivable to grind back the fracture to the connector in order to model, cast and weld on a new one from there. The resilient area would then be the usual one.

With thicker structures, it is sometimes helpful to grind the welding area into a V-shape to fill this area with welding wire. Slight reinforcement of the welding area beyond the break generally makes sense in order to have enough material available for finishing and polishing and to avoid the formation of predetermined breaking points due to tapering or retractions.

These detailed considerations should be made for each type of repair in order to avoid failures that are not due to poor welding, but to incorrect planning and implementation. 

Due to the very different possibilities, it is unfortunately not possible to make any general recommendations for suitable welding parameters.