Failure of cement

Another effect of biomechanical stress is cement failure, which usually affects the prosthetic attachment and can be addressed with a recementation technique. Decementation has become far less common as a result of advances in material science, especially with regard to luting agents. To prevent such occurrences, however, meticulous treatment planning and adherence to clinical criteria are necessary.
Technical issues

Compared to implant-supported removable prostheses, technical problems are more likely to develop with implant-supported FPDs.

Fracture of the framework

Whenever there is a rigid connection between the osseointegrated implant and the fixed subsequent framework, the strains are inevitably induced in every component of the framework. The additional functional load produces supplementary strains, which affect the bone-implant-prosthesis assembly. Hence, the challenge remains for a prosthodontist to deliver a tolerable prosthesis that does not jeopardize the endurance of the treatment. Therefore, passive fit of the framework has been advocated as a requirement for successful long-term osseointegration of the implant with the surrounding bone.

The problem of fracture of framework is reportedly exaggerated in partially edentulous jaws, because the implant-abutment interface and abutment retention screw are exposed to higher lateral bending loads, tipping, and elongation as compared to bilaterally splinted implants in a completely edentulous jaw. The length of the cast bar or framework span is directly proportional to the construction-related distortion,[60] which could get worsened by nonparallel placement of dental implants.

To correct the gross misfit of the abutment–superstructure relationship, cutting the framework or bar and then joining the sections by welding or soldering is recommended, but both techniques may further impair the original fit. Since the corrective methods usually lead to a misfit, in order to avoid the need for such corrections, it is recommended that effort must be made to improve the original/initial fit of the cast frameworks. Factors that influence the accuracy of the initial fit of the framework include the impression material, impression technique, and positional stability of the transfer posts. Refined approaches and detailed and accurate prosthodontic procedures are still a requisite to achieve a passive fit with an implant-supported superstructure.