ABE Endodontics key terms

A fleshy mass of hyperplastic granulation tissue that grows out of a wide open cavity in a young, well-vascularized tooth, usually a primary molar. It is chronic hyperplastic pulpitis, often painless and bleeds easily on touch.

A localized mass of chronic inflammatory tissue at the root apex, made up of lymphocytes, plasma cells, macrophages and proliferating capillaries. It arises from prolonged pulp necrosis and is usually symptomless; radiographically it may appear as a widened periodontal ligament space.

A true epithelium-lined cavity at the apex of a necrotic tooth, arising when inflammatory stimuli cause epithelial rests of Malassez to proliferate. It is the most common odontogenic cyst and may be radiographically indistinguishable from a granuloma.

A localized increase in bone density around the apex of a tooth with low-grade chronic pulp inflammation, seen radiographically as a radiopaque area with an intact periodontal ligament space. It represents a defensive osteoblastic response rather than infection of bone.

A pulp sensibility test in which a refrigerant spray or ice is applied to the facial surface; a healthy pulp responds with a brief, sharp sensation that disappears when the stimulus is removed. A lingering response suggests irreversible pulpitis.

A sensibility test that passes a graded current through the tooth to depolarize intact A-delta nerve fibres. It indicates the presence of viable sensory nerves, not blood flow, so it can be positive in a partially necrotic pulp.

Pain on biting or release of biting, often sharp and poorly localized, in a tooth with an incomplete fracture extending into dentine. Diagnosis uses transillumination, bite tests and careful probing; the fracture may later propagate to the pulp.

Three-dimensional volumetric imaging that shows root canal anatomy, fractures and periapical bone lesions in fine detail. Its higher radiation dose than periapical films means it should be reserved for cases where conventional imaging is inadequate.

A structured community of bacteria attached to the canal wall and embedded in a self-produced matrix of polysaccharides. It resists host defences and disinfectants, and mechanical disruption is required for its removal.

A hardy gram-positive coccus commonly found in teeth with failed root canal treatment. It tolerates high pH, survives starvation and can invade dentinal tubules, making it a frequent cause of persistent apical periodontitis.

A component of the outer membrane of gram-negative bacteria that is a potent trigger of inflammation. In the root canal it diffuses into periapical tissues and drives bone resorption through macrophage and osteoclast activation.

Micro-organisms, typically Actinomyces species, organized in colonies or biofilms on the external root surface beyond the apex. Because they lie outside the canal, they may persist after adequate instrumentation and usually require surgery.

The distance from a coronal reference point to the apical limit of instrumentation, usually the apical constriction, determined by apex locator and confirmed radiographically. Accurate length prevents short fills and instrumentation beyond the foramen.

The narrowest part of the canal near the cementodentinal junction, typically 0.5 to 1 mm short of the radiographic apex. It marks the ideal apical limit of cleaning, shaping and obturation in most cases.

A smooth, reproducible passage from the canal orifice to the apical third created with small hand or rotary files before larger instruments are used. It reduces torsional stress, ledging and instrument separation.

A 1 to 2 micrometre film of dentine debris and remnants of pulp and bacteria that coats the canal wall after instrumentation and blocks dentinal tubules. It harbours bacteria and limits disinfectant penetration, so chelating agents are used to remove it.

The primary endodontic irrigant; it dissolves necrotic tissue, kills a broad range of micro-organisms and, at higher concentrations, lubricates the canal. It does not remove the smear layer and can cause severe tissue damage if extruded beyond the apex.

Delivery of irrigant through a small ultrasonically oscillating file placed in a flooded canal without intentional contact with the walls. Acoustic streaming and cavitation improve tissue dissolution and disinfection in uninstrumented areas.

A natural polymer of isoprene mixed with zinc oxide and barium sulphate, supplied in cones that match canal taper. It is the standard core filling material; it seals only when adapted to the walls with a sealer.

A calcium silicate-based sealer that sets in the presence of moisture, forms a hydroxyapatite-like precipitate and bonds chemically to dentine. It is biocompatible, has low solubility and does not shrink on setting.

An obturation technique in which thermoplasticized gutta-percha is packed apically with heated pluggers and then backfilled in increments. It adapts well to irregular canals but risks sealer extrusion and vertical root fracture.

A circumferential band of 1.5 to 2 mm of sound tooth structure coronal to the preparation margin that grips the restoration. It opposes lateral forces and greatly improves the fracture resistance of endodontically treated teeth.

Passage of bacteria and fluid from the mouth along a defective restoration into the root canal system. Leakage can cause failure even after perfect instrumentation, so a durable coronal seal is essential.

Re-entry into a previously treated tooth to remove filling material, address persistent infection and re-obturate. It is the first option for post-treatment apical periodontitis when the tooth is restorable and the cause is intraradicular.

A file or other instrument that fractures and remains lodged in the canal. Management options are bypassing, removal with ultrasonics or retrieval systems, or leaving it in place when the canal can still be cleaned.

Extrusion of sodium hypochlorite beyond the apex, causing sudden severe pain, immediate swelling and tissue necrosis. Management is supportive: irrigation with saline, analgesia, cold compresses and monitoring for airway compromise.

An artificial communication created between the root canal and the periodontium or oral cavity during access or instrumentation. Immediate repair with a biocompatible material improves the prognosis; site, size and timing of repair all matter.

Surgical resection of the apical portion of a root, usually about 3 mm, to remove the apex and any uninstrumented apical ramifications. It is performed with a minimal bevel under magnification and copious irrigation.

Placement of a biocompatible material such as mineral trioxide aggregate into a prepared retropreparation to seal the apical canal after resection. It prevents leakage from the cut canal into periapical tissues.

Use of barrier membranes with or without bone grafts to keep epithelium and connective tissue out of a surgical defect, allowing periodontal ligament and bone to regenerate. It is considered for large through-and-through periapical lesions.

Deliberate extraction of a tooth, treatment of the apical or canal problem outside the socket, then replacement in its alveolus. It is reserved for cases where surgery or retreatment is impractical, with limited extraoral time to protect the periodontal ligament.

Complete displacement of a tooth out of its socket, causing severance of the pulp blood supply and periodontal ligament damage. Prompt replantation, correct storage medium, splinting and timely root canal treatment determine the outcome.

Loss of root and periodontal ligament that is replaced by bone, with the root becoming ankylosed to bone. It follows severe periodontal ligament injury, progresses irreversibly and is common after avulsion or intrusion in mature teeth.

A biologically based treatment for immature necrotic teeth in which the canal is disinfected and a blood clot is induced, allowing new tissue and continued root development. It relies on stem cells from the apical papilla and a bacteria-tight coronal seal.

A mixture of ciprofloxacin, metronidazole and minocycline used as an intracanal medicament in regenerative procedures. It is effective against canal flora but can stain teeth, so alternatives are often preferred in aesthetic cases.

An injection targeting the inferior alveolar nerve before it enters the mandibular canal, anaesthetizing the mandibular teeth on one side. Failure is common because of accessory innervation and anatomical variation, so supplemental injections are often needed.

An amide local anaesthetic with a thiophene ring, used at 4% with epinephrine. It diffuses through bone well and is popular for mandibular infiltration, though it carries a small risk of persistent paraesthesia.

Addition of sodium bicarbonate to an anaesthetic solution to raise its pH closer to tissue pH, increasing the proportion of uncharged base. Onset may be faster and injection less painful, especially in inflamed tissue.

Administration of an analgesic such as an NSAID before treatment begins to prevent central and peripheral sensitization. In endodontics it reduces post-operative pain and the need for rescue medication.