Prosthodontics & Occlusion · patient case question
What is the principal difficulty in providing a conventional fixed bridge here?
Patient case: Planning a fixed bridge to replace tooth #30
Patient: Male, 47 years old
Chief Complaint: Wishes to replace a missing lower right first molar.
Background: Tooth #30 was extracted four years ago and never replaced.
Current Findings: Tooth #31 has drifted mesially and is rotated. Tooth #29 is tipped distally. Both proposed abutments are vital, unrestored and periodontally sound. Tooth #3 has supra-erupted slightly into the space.
Show answer and explanation
Correct answer: B. Establishing a common path of insertion
- A. Mesial drift of #31 has REDUCED the space, but reduced space is a consequence of the drift; the governing prosthetic obstacle is the path of insertion.
- B. CORRECT. A fixed partial denture is a rigid, one-piece casting, so every retainer must draw along a SINGLE common path. When one abutment has drifted and rotated and the other has tipped, their long axes diverge and no single path exists without either over-preparing one abutment — risking pulp exposure — or accepting non-parallel preparations that will not seat.
- C. The stem states that both abutments are periodontally sound.
- D. Crown height is not identified as a problem here; both abutments are unrestored with normal clinical crowns.
Note: The realistic options: uprighting the abutments orthodontically first · a single implant, which sidesteps the parallelism problem entirely · or a non-rigid connector with a key-and-keyway allowing the retainers to seat along separate paths.
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