Single Molar Replacement in a Patient With Treated Periodontitis and a Narrow Ridge

Facts that constrain the decision:

• Ridge 5.2 mm crestal / 4.1 mm at 3 mm depth. A standard 4.1 mm-diameter implant needs roughly 1.5–2 mm of buccal and lingual bone, so a 4.1 mm implant is at or beyond the limit of what the ridge allows without augmentation. A narrow-diameter implant (e.g., 3.3–3.5 mm) is feasible in 4–5 mm of bone but has reduced fatigue resistance and is generally restricted to single-unit, non-parafunctional, low-load sites.
• 12.5 mm to the canal allows a 10 mm implant with ~2 mm safety margin; a shorter implant (8 mm) is also defensible.
• Interocclusal space 8 mm plus a supra-erupted opposing molar means the crown will need ~2 mm occlusal reduction and the vertical space is adequate for a screw-retained or cemented crown but the occlusal scheme must be managed.
• Stable periodontitis with low BOP supports implant placement, but the patient is at elevated risk for peri-implant disease and must be enrolled in maintenance before surgery.

Options to present:

1. Short/narrow implant, no graft - least morbidity and cost; acceptable if load is controlled and the implant is not in a high-load cantilever.
2. Guided bone regeneration or ridge split at placement - increases width, allows a standard-diameter implant, adds cost and a second-stage healing period.
3. Fixed partial denture 45–47 - requires preparing two sound teeth; long-term survival of a 3-unit FPD in a periodontally susceptible patient is inferior to a single implant, and it violates the principle of not destroying intact teeth.
4. Removable partial denture - does not meet her stated priority.

Recommendation: Present all four, but recommend option 1 (narrow or short implant with simultaneous minor contour augmentation if the buccal plate is thin) conditional on a documented maintenance program and occlusal control of the supra-erupted antagonist. Reserve GBR for a case where primary stability or buccal plate thickness cannot be achieved. Emphasize that the decision is driven by the 4.1 mm dimension at depth, not by the crestal 5.2 mm.

Counseling structure (shared decision-making):

• Acknowledge the legitimate advantages of the FPD: fewer surgeries, shorter total treatment time, lower initial cost.
• Then present the trade-offs with numbers rather than adjectives.

Key points:

• Tooth destruction is irreversible. Preparing 45 and 47 removes 1.5–2 mm of enamel circumferentially on two virgin teeth. If either later needs endodontics or fractures, the failure cascade is expensive.
• Survival data: Systematic reviews of single implants vs. 3-unit FPDs in partially edentulous patients consistently show higher long-term survival for the implant crown (roughly 95%+ at 10 years vs. ~85–90% for FPDs), with the FPD's main failure mode being biologic (caries, endodontic) at the abutments.
• Periodontal risk: In a patient with a history of periodontitis, FPD abutments complicate hygiene and increase risk of recurrent disease at the very teeth that are currently healthy.
• Cost over time: The initial FPD may be cheaper, but replacement of an FPD at 10–15 years and possible endodontic/surgical retreatment of abutments often exceeds the lifetime cost of an implant.
• Her priority: She wants a fixed, non-removable solution - both options satisfy that, so the differentiator is long-term risk to her natural teeth.

Close: Offer a written estimate for both, a 2-week decision window, and confirm she understands that declining the implant does not end her eligibility - she can return. Document the discussion and her choice.

Pre-surgical checklist (periodontal and medical):

• Confirm periodontal stability is documented and recent: full-mouth plaque <20%, BOP <15–20%, no pockets >4 mm, and a signed maintenance schedule. She meets this today, but re-verify at the day of surgery if more than 3 months have elapsed.
• Medical: HbA1c 6.4% is acceptable (well-controlled); confirm no new bisphosphonate, anticoagulant, or immunosuppressant since last visit.
• Occlusal: reduce or restore the supra-erupted maxillary molar before or at the time of crown delivery so the implant crown is not in hyperocclusion.
• Radiographic: confirm canal position and plan implant length with ≥2 mm safety margin; plan a surgical guide.

Surgical plan: Narrow-diameter or standard-diameter implant depending on final site preparation, with simultaneous contour augmentation if buccal plate <1.5 mm. Two-stage or one-stage depending on primary stability and soft-tissue thickness.

Maintenance plan (this is the part the exam tests):

• Post-op: chlorhexidine rinse, no brushing over the site for 1 week, soft diet.
• Prosthetic phase: verify cleansability, screw-retained preferred for retrievability, avoid submucosal cement.
• Long-term: periodontal maintenance every 3 months for the first year (she is a treated periodontitis patient - this is a risk-based interval, not the standard 6 months), then 3–6 months based on stability. At each visit: probing depths around the implant, BOP, plaque score, radiographic crestal bone level at 1 year and then every 1–2 years, and occlusal check.
• Define peri-implant mucositis vs. peri-implantitis thresholds in her record so the next clinician can act early. Give her written red flags (bleeding, swelling, mobility).