Endodontics
What the exam tests
Endodontic questions cluster around three decisions: is the pulp diseased and how, can the tooth be saved, and how do you clean, shape, and seal it predictably. Know the diagnostic vocabulary: reversible pulpitis (provoked, brief, no spontaneous pain), symptomatic and asymptomatic irreversible pulpitis, and pulp necrosis, then correlate with the apical diagnoses - symptomatic apical periodontitis, asymptomatic apical periodontitis, acute and chronic apical abscess, and condensing osteitis. A normal-appearing periapex on a radiograph does not rule out necrosis.
Concepts to own
- Pulp testing: the cold test is the workhorse; the electric pulp test is unreliable in young or recently traumatized teeth; percussion tests the periodontium, not the pulp.
- Working length: the apical constriction sits roughly 0.5–1.0 mm short of the radiographic apex, and electronic apex locators are accurate when the canal is not flooded with pus or hemorrhage.
- Shaping objectives: taper, continuity, and preservation of canal anatomy rather than aggressive enlargement.
- Irrigation: sodium hypochlorite dissolves tissue and kills biofilm, EDTA removes the smear layer, and chlorhexidine is an alternative when hypochlorite is contraindicated. Never mix hypochlorite and chlorhexidine - a brown precipitate forms.
- Obturation and restoration: the coronal seal matters as much as the apical seal; a tooth that cannot be durably restored should not be treated.
Traps
Questions favor the phoenix abscess (acute exacerbation of a chronic lesion), the hypochlorite accident (sudden pain, swelling, chlorine taste), and the second mesiobuccal canal of maxillary molars, which is present in the majority of teeth.
Rule of thumb
Diagnose before you drill. Irreversible inflammation calls for pulpectomy or full cleaning; a necrotic tooth with an acute swelling calls for drainage plus cleaning, and antibiotics alone will fail.