Prosthodontics & Occlusion · patient case question
Which tooth surface and which mandibular movement are most likely responsible for the mobility of these crowns?
Patient case: Mobile anterior crowns
Patient: Male, 58 years old
Chief Complaint: “My two front crowns wiggle when I bite.”
Background: Porcelain-fused-to-metal crowns on teeth #8 and #9 placed six years ago. Grinds at night, no appliance. Otherwise healthy.
Findings: Grade I mobility of #8 and #9. Wear facets on the incisal edges. Heavy contact on the anterior teeth in excursions; posterior teeth show minimal wear.
Show answer and explanation
Correct answer: B. The lingual surfaces, during protrusive movement
- A. In maximum intercuspation the anterior contact should be light or absent, and any load there is closer to axial than the excursive load is.
- B. CORRECT. The maxillary anterior teeth contact the mandibular incisors on their LINGUAL surfaces, and it is the PROTRUSIVE excursion that loads that contact. Because the maxillary incisors are inclined facially, protrusive contact directs force labially rather than down the long axis — a non-axial load that produces mobility. This is exactly why anterior guidance must be evaluated whenever anterior crowns loosen.
- C. In lateral working movement the CANINES should be doing the disclusion. If the incisors are carrying working-side load, that is a separate problem, but protrusive is the movement that specifically loads the central incisors.
- D. The facial surfaces of maxillary anteriors have no antagonist and receive no occlusal load at all.
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