Endodontics
Scope
Examines diagnosis and working-length determination, canal anatomy, shaping and irrigation, obturation, and the management of the previously treated tooth.
Diagnosis and working length
- Cold test and electric pulp test assess vitality; percussion and palpation assess periapical status; CBCT for complex anatomy.
- Working length: electronic apex locator confirmed radiographically, with the file 0.5–1 mm short of the radiographic apex.
Anatomy and shaping
- Maxillary first molar: MB1, MB2 (present in roughly half to two-thirds of teeth), DB and palatal. Mandibular first molar: MB, ML and distal.
- The second mesiobuccal canal is the most commonly missed canal; look for it under the MB1 orifice.
- Crown-down rotary shaping with a glide path; patency filing and recapitulation maintain the canal.
Irrigation
- Sodium hypochlorite 0.5–5.25% dissolves tissue and is antimicrobial; concentration and volume both matter.
- 17% EDTA removes the smear layer.
- Never mix NaOCl with chlorhexidine - a brown para-chloroaniline precipitate forms. Flush with saline between them.
Obturation
- Gutta-percha with sealer; warm vertical compaction adapts to irregular canals; sealer alone does not obturate.
Worked example
After NaOCl irrigation, a brown precipitate appears when chlorhexidine is introduced. Reasoning: the acid-base reaction between the two irrigants produces para-chloroaniline, a stain and potential carcinogen; the canal should be flushed with saline or EDTA and the two irrigants kept in separate phases.
Traps
- Trusting an apex locator in a bleeding, wet canal without radiographic confirmation.
- Overinstrumenting the apical foramen and losing patency or extruding debris.
- Obturating without verifying that all canals, especially MB2, have been located.