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Fixed Bridge Biomechanics — ORE Part 1 MCQ

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HardProsthodonticsFixed Bridge BiomechanicsORE Part 1

A patient requires a conventional three-unit fixed-fixed bridge to replace the lower right first molar. The lower right second premolar and second molar are vital and minimally restored. Which biomechanical complication is most important to consider when designing the bridge?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: A — Loss of retention at the less retentive abutment from differential tooth movement

Explanation lettering: E = shown as B · B = shown as E

A is correct. The premolar and molar have different root form, periodontal support and physiological mobility. A rigid fixed-fixed bridge limits their independent movement during function, producing tensile and peeling forces at the retainers. The less retentive retainer, commonly the premolar, is consequently more vulnerable to loss of retention or de-cementation. Prosthodontic literature supports the principle that permitting differential movement reduces adverse stress and debonding risk. B is not clinically important because prosthesis weight is negligible. C and D are incorrect because replacement of one posterior tooth is a routine three-unit bridge span when abutments are suitable. E is possible in weakened or overloaded teeth, but is not the principal concern with vital, minimally restored abutments.

Reference: Kanojia E, et al. Shielding the Pier Abutment Using a Nonrigid Connector. Cureus. 2024. https://pubmed.ncbi.nlm.nih.gov/38406087/