Replacing a Missing Molar Next to a Compromised Tooth
A 54-year-old woman wants the gap from her lower right first molar (46) closed; it was extracted 6 years ago and food packs there. The upper opposing molar has over-erupted by about 2 mm. She is healthy, a non-smoker and takes no medication.
The adjacent teeth: 45 has a 4 mm distal pocket with about 20% bone loss and no mobility. 47 has an 8 mm distal pocket with bleeding on probing, a Grade II buccal furcation involvement, 2 mm recession and about 50% bone loss with an angular defect distally. Both 45 and 47 are vital; 47 has an occlusal composite. Plaque score is 45% and her BPE is 3/4/3.
Options discussed are a three-unit bridge from 45 to 47, an implant-supported crown at 46, or a removable partial denture. She is a teacher, "hates the idea of a plate", has about $4,500 available and has three weeks of leave in two months.
1. Assess the prognosis of 47 and explain how it changes the choice between a bridge and an implant-supported crown at 46.
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47 is the tooth that drives the decision. An 8 mm distal pocket with bleeding, a Grade II furcation, 50% bone loss and an angular defect means 47 has a questionable long-term prognosis and is a poor choice of bridge abutment.
A three-unit bridge from 45 to 47 would splint a compromised molar to a premolar that already has a 4 mm distal pocket, and the pontic and connectors would make cleaning the 47 furcation harder still. The predictable failure mode is that 47 loses more support, the bridge is sectioned, and 45 has been unnecessarily prepared - and its distal margin now sits at the site of a periodontal pocket. One failing tooth has then taken a sound tooth with it. A cantilever from 45 to replace a molar is not a reasonable load-bearing design in a premolar.
An implant at 46 is independent of 47. If 47 later fails, the implant crown is unaffected - that is the decisive structural advantage. The trade-offs are that the site has been edentulous for six years so some ridge resorption is likely, grafting may be needed, and the implant still requires a periodontally stable, motivated patient.
So: periodontal treatment and re-assessment first, then a single implant at 46 with 47 maintained as long as it can be; the bridge is the least favourable option, not the cheapest sensible one.
2. What periodontal treatment would you complete before any definitive prosthesis, and what criteria would you use at re-assessment?
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Non-surgical periodontal therapy first: full-mouth supragingival and subgingival instrumentation, with oral hygiene instruction targeted at her embrasures and the 47 furcation - interdental brushes sized to each space, not floss alone. Confirm the 8 mm measurement is true attachment loss and not false pocketing with the radiograph in front of you. Address the occlusal trauma question on 47 and the over-erupted upper molar at this stage only if it is contributing.
Re-assess at 6–8 weeks: bleeding on probing by site, pocket depths, plaque score (aim for under 20%), mobility, furcation status and whether the 47 distal defect remains deep and inflamed. If the distal defect on 47 is still 6 mm or more with bleeding, discuss the options openly - regenerative surgery (guided tissue regeneration with graft) into the angular defect has variable outcomes in mandibular furcation defects, or extraction of 47, which changes the whole plan to replacing both 46 and 47.
Nothing definitive is prepared while a tooth has active 8 mm pocketing. That is the point of the re-assessment: you cannot design a prosthesis whose abutment prognosis is unknown. Plan the management of the over-erupted 16 at the same time, because the occlusal plane must be correct before the implant crown is designed.
3. Given her $4,500 budget, what would you propose, and how would you present the trade-offs?
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Be honest about the arithmetic. A privately placed single implant with crown in New Zealand typically costs more than her budget, so she is choosing between staging the treatment, accepting a compromise, or waiting. Do not let the budget push her into a bridge on a compromised 47, which is the option most likely to cost her more in five years.
Proposal: stage it. Stage one now - periodontal treatment and re-assessment, oral hygiene, and management of the over-erupted 16. Replace the missing tooth provisionally with an acrylic partial denture if she wants the appearance for teaching, with the caveats: it collects plaque, it is not definitive, and it must be cleanable.
Stage two - save towards the implant, or investigate whether she qualifies for treatment through a dental school or hospital programme, and consider whether grafting will add cost. Revisit the bridge only if 47 responds well to treatment, she accepts the hygiene burden, and she understands that 47 remains the weak link.
Present the trade-offs in writing: total cost, number of visits, reversibility, hygiene demands and what happens if 47 fails. Warn that the over-erupted 16 will keep extruding while the space is open. Her unhurried, documented decision is the correct outcome - not a rushed bridge built around three weeks of leave.