Final answer:
A "broken stress" or "non-rigid" connector for a fixed partial denture is indicated when abutment preparation would require excessive tooth structure removal.
Step-by-step explanation:
A "broken stress" or "non-rigid" connector is indicated for a fixed partial denture when the abutments cannot be prepared in parallel without excessive removal of tooth structure. This situation arises when the natural teeth that serve as abutments for the denture have divergent angles that can't be corrected without significant loss of tooth structure, which would compromise the health and strength of these teeth. By using a non-rigid connector, the prosthesis can accommodate the non-parallelism while still allowing for adequate retention and function. This is an important consideration in prosthodontics to ensure the longevity and effectiveness of dental restorations.