Endodontics
Endodontic questions are usually case-based: state the pulpal and periapical diagnosis, then justify one technical decision.
Diagnosis and testing
- Cold test assesses A-delta fibres; EPT can give a false positive in a partially necrotic multirooted tooth and false negatives in calcified canals.
- Irreversible pulpitis gives lingering pain; a necrotic pulp gives no response with apical tenderness.
- Separate symptomatic from asymptomatic apical periodontitis by symptoms, not by radiograph size.
Shaping and irrigation
- Working length 0.5-1 mm short of the apical foramen, confirmed with an apex locator in a reasonably dry canal.
- Crown-down preparation with a glide path first; NiTi rotary files reduce transportation but need torque and speed limits; watch ledging and file separation in curvature.
- Sodium hypochlorite 1-3% dissolves tissue and disinfects; 17% EDTA for about one minute removes the smear layer; never mix hypochlorite with chlorhexidine because a precipitate forms.
Obturation and restoration
- Warm vertical condensation or single-cone with a bioceramic sealer; length control matters more than the technique chosen.
- Leave 4-5 mm of apical gutta-percha under a post; a 1.5-2 mm ferrule improves fracture resistance.
- A cracked tooth with reproducible pain on biting after root canal treatment often needs cuspal coverage or extraction.
Worked example
A mandibular first molar with irreversible pulpitis has a 25-degree mesial curvature and a 19 mm working length. A rotary file at controlled speed and light torque is advanced behind a patency file; 2.5% hypochlorite is used, then EDTA, then a warm vertical fill. A single-visit approach is acceptable because there is no apical periodontitis or exudate; an infected necrotic case would be better served by calcium hydroxide dressing.
Traps
Extruding hypochlorite and blaming the injection; reporting the radiographic apex as the working length; assuming a separated file always requires extraction; obturating without a plan for the coronal seal.