Prosthodontics & Occlusion · patient case question
A mandibular RPD has a lingual plate major connector and a rest on the cingulum of tooth 27. What is the primary function of that rest?
Patient case: A denture that will not stay put
demo: 71-year-old male
chief: His upper denture drops when he speaks and food collects under it. He also has a sore lump at the front.
history: He has worn the same maxillary complete denture for fourteen years and has never had it relined. Only the mandibular anterior teeth from 22 to 27 remain.
meds: None relevant.
findings: The maxillary anterior ridge is displaceable and mobile on palpation while the posterior ridge is firm. A folded, fibrous ridge of tissue lies in the labial sulcus adjacent to the denture flange. The mandibular anterior teeth show generalised wear.
Show answer and explanation
Correct answer: C. Support, by directing occlusal forces along the long axis of the tooth
- A. Stability resists horizontal and rotational forces and comes from rigid components contacting axial surfaces, such as the proximal plates, minor connectors and reciprocal arms.
- B. Reciprocation neutralises the lateral force generated by the retentive arm and is supplied by a rigid arm or plate on the opposing surface.
- C. Correct. A rest is the component that provides support. It transmits occlusal load down the long axis to the abutment and prevents the prosthesis settling into the tissues. The cingulum rest is preferable to an incisal rest because it sits closer to the horizontal axis of rotation and is more esthetic.
- D. Retention resists vertical displacement and is supplied by the retentive clasp terminal engaging an undercut, not by a rest.
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