Endodontic-Periodontal and Restorative/Prosthodontic Interrelationships
This domain tests whether you can separate pulp-derived from periodontal disease and plan the final restoration before starting.
Classifying endo-perio lesions
Simon's classification remains the working framework: primary endodontic, primary periodontal, primary endodontic with secondary periodontal involvement, primary periodontal with secondary endodontic involvement, and true combined lesions. Glickman adds acute and chronic patterns. The pulp sensibility test is the discriminator: a necrotic pulp with a deep isolated pocket points to an endodontic origin.
Probing patterns
An isolated narrow pocket running to the apex suggests an apical lesion draining through the sulcus, and it usually resolves with root canal treatment alone. Generalized pocketing with a vital pulp indicates periodontal disease. A furcation radiolucency with a narrow pocket suggests a perforation or a fracture.
Perforation and resorption
Repair perforations with MTA or a bioceramic; prognosis depends on the level of the perforation (crestal is worse than apical) and the time to repair. External cervical resorption is managed by removing the resorptive tissue and restoring the defect, with endodontic treatment only if the pulp is involved.
Restorative planning
- Post and core: ferrule of 1.5-2 mm, post length at least half the root, 4-5 mm of apical gutta-percha retained, narrow post preserving dentin.
- Endocrowns are an alternative in short, heavily broken-down molars.
- Crown lengthening versus orthodontic forced eruption: forced eruption brings bone and gingiva with the tooth.
- Posterior teeth with marginal ridge loss need cuspal coverage.
Worked example
A mandibular molar with a 9 mm mesial pocket, no response to cold, and a periapical lesion. Diagnosis: primary endodontic lesion with secondary periodontal involvement. Treat the canal first, re-probe at 4-8 weeks, then decide on periodontal surgery.
Traps
Scaling an endodontic lesion and delaying the root canal; ignoring the ferrule; planning the restoration after obturation rather than before.