Case Model 5
Replacement Instability — Escalation Cycle Failure
Case Summary
Mandibular first molar previously treated with: large composite, crown, root canal, crown replacement after fracture.
Now presenting with vertical root fracture.
Adjacent teeth have moderate restorations.
Patient reports heavy function.
No generalized periodontal disease.
1. Structure Assessment
Significant dentin removal from prior treatments
Loss of internal structural integrity
Root fracture present
Adjacent teeth structurally intact but moderately restored
Bone support adequate
Structural reserve of affected tooth: Exhausted
Structural reserve of adjacent teeth: Moderate
This tooth has undergone cumulative structural reduction across multiple irreversible interventions.
2. Force Assessment
Moderate to heavy occlusal load
No occlusal guard use
Adjacent posterior contacts intact
Load previously concentrated on treated molar
Force risk: Moderate to High
Force likely contributed to fatigue accumulation and fracture progression.
3. Time Projection
Restoration history spans 10+ years
Replacement intervals shortening
Progressive structural compromise observed
No systemic occlusal correction performed
Time risk: High
Fatigue accumulation compounded by prior irreversible interventions.
4. Long-Term Stability Projection
Under Continued Tooth Preservation Attempts
Root fracture non-restorable
Further structural manipulation impossible
Catastrophic structural loss confirmed
Under Extraction + Replacement Strategy
Option A: Implant Adjacent teeth preserved. New load interface introduced. Requires evaluation of force distribution.
Option B: Bridge Reduction of adjacent teeth required. Further structural reserve consumed.
Projected long-term stability must now be evaluated at system level, not individual tooth level.
5. Threshold Position
For the affected tooth: Threshold convergence exceeded. Structural reserve exhausted. No preservation pathway remains viable.
For the system: Decision now depends on convergence analysis of adjacent teeth and bone.
If projected force across projected time exceeds tolerance of abutments under bridge design, implant favored.
If bone support insufficient for predictable implant stability under projected force, bridge may be indicated.
Replacement instability confirms that prior escalation cycles did not incorporate system-level threshold evaluation.
Continuation of the same pathway without system correction would compound instability.
Decision: Extraction required. Replacement modality determined by structure, force, time, and long-term stability at system level.