The mandibular denture that floats: two implants or a remake?
72-year-old woman, edentulous 8 years, presents with 3-month-old maxillary and mandibular complete dentures. She reports that the mandibular denture "floats" during speech and that she cannot chew meat. Mandibular residual ridge height is 9 mm anteriorly and 6 mm in the premolar region; the floor of the mouth at rest sits 3 mm above the lingual flange, and only 1 mm of attached mucosa is present buccally. The maxillary denture has a good border seal but a shallow, 1 mm posterior palatal seal. A gothic arch centric relation record was used; mounted casts show a 1.5 mm slide from CR to maximum intercuspation. She can afford at most two implants and refuses bone grafting.
1. She asks whether two implants are worth the cost or whether a new mandibular denture would solve the problem. How do you decide, and what do you tell her?
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Frame the decision as a diagnosis question, not a preference question.
- The complaint is retention and function, not pain. Two-implant overdentures consistently outperform conventional mandibular dentures on retention, chewing ability and satisfaction, so the option is legitimate.
- But feasibility comes first. Her anterior height is 9 mm and premolar height 6 mm. Six millimetres in the premolar region is generally inadequate for a conventional implant, and 9 mm anteriorly is borderline once crestal width and the incisive canal/mental foramina are considered. Request a CBCT before promising anything; do not commit on panoramic or clinical estimates alone.
- Explain the realistic range: if bone between the foramina allows two implants of roughly 3.5–4.0 mm diameter, she can expect meaningful improvement in retention but the prosthesis will still be largely tissue-supported.
Separately, the existing dentures have correctable faults: the 1 mm posterior palatal seal is shallow and the 1.5 mm CR–MIP slide is untreated. Address both regardless of the implant decision, and tell her plainly that a remake alone may improve but probably will not eliminate the mandibular complaint.
2. Assuming two implants are placed in the canine regions, describe how you would change the mandibular prosthesis and why.
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Design principles for a two-implant mandibular overdenture
- Retention mechanism: a resilient/self-aligning attachment (e.g. Locator-type) suits a tissue-supported prosthesis because it permits some vertical resilience rather than converting the denture into a rigidly implant-borne one, which two implants cannot support.
- Support: keep broad tissue coverage of the residual ridge. Do not shorten the flange or hollow the base in the belief that the implants now carry the load.
- Space: the attachment and its housing need vertical room. If the 3-month-old denture lacks that space, a new prosthesis with a processed base is preferable to retrofitting, because grinding relief under the housing creates a plaque trap and weakens the base.
- Borders: maintain the lingual flange in the retromylohyoid area and re-verify the posterior palatal seal, since retention problems are rarely single-cause.
- Occlusion: re-record CR, eliminate the 1.5 mm slide, and keep a bilateral balanced scheme with a modest posterior tooth count.
3. What, if anything, would you change about the maxillary denture?
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- Posterior palatal seal: 1 mm is shallow; a properly placed seal of roughly 1–1.5 mm into the compressible tissue just anterior to the vibrating line improves adaptation and reduces dislodgement.
- Verify that the seal sits over tissue, not over the hard palate's immovable zone, and that it does not extend past the foveae.
- Recheck the occlusion at the corrected CR; a maxillary denture can be technically well made and still shift because of a premature contact on the working or balancing side.
- If the maxillary denture is otherwise sound and the patient's complaint is mandibular, do not remake it reflexively - adjust and remount. The error to avoid is treating the maxillary prosthesis as the source of a mandibular complaint simply because the patient mentions both.