Pulp Pathology
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Direct answer
Pain that lingers after a cold stimulus — or, the classic viva twist, pain provoked by hot drinks yet eased by cold water — marks the shift from reversible to irreversible pulpitis, the central distinction in pulp pathology. Reversible pulpitis is a brief, stimulus-bound inflammation that resolves when the irritant is removed; irreversible pulpitis is spontaneous, prolonged and needs root canal treatment or extraction. The same spectrum continues through chronic hyperplastic pulpitis (the pulp polyp of young patients with large carious exposures), pulp necrosis with its greenish-black discolouration, internal resorption with its pink coronal spot, and the pulp stones that crowd ageing and worn pulps.
What you must remember
- Reversible pulpitis: sharp pain to cold or sweet that disappears within seconds of removing the stimulus; the tooth is not tender to percussion and the pulp is salvageable.
- Irreversible pulpitis: spontaneous, prolonged pain, worse on lying down and at night, often relieved classically by cold in the early stage; the first-line treatment is root canal treatment or extraction.
- Chronic hyperplastic pulpitis (pulp polyp): a reddish, cauliflower-like mass filling the carious cavity of a young tooth with a wide apical foramen and good immunity; it bleeds on probing but is surprisingly painless.
- Pulp necrosis may be coagulative or liquefactive; the greenish discolouration comes from iron sulphide formed when haemoglobin breakdown products meet hydrogen sulphide from bacteria.
- Internal resorption presents as a pink coronal spot and radiographically as a focal, balloon-like enlargement of the pulp canal; odontoclasts are at work, and root canal treatment must be started before the wall perforates.
- Pulp stones are false (dystrophic calcification, the common kind) or true (rare, dentine-like with tubules); diffuse pulp calcification accompanies ageing, attrition and orthodontic loading.
- Acute pulpitis progresses from serous to suppurative; unanswered, it drains through the apical foramen into the periapical tissues.
Working through thermal pain step by step
A 30-year-old reports two weeks of pain in a lower molar. First, localize the offending tooth with the patient's own history — hot coffee triggers it, and the ache now lasts half an hour after the cup. Test each suspect tooth with a cold spray on a cotton pellet and compare with the contralateral tooth: an exaggerated, lingering response on the second molar points to irreversible pulpitis, whereas a brief twinge that vanishes with the stimulus would fit reversible disease. Percussion and palpation are next — tenderness to percussion means the inflammation has already reached the periodontal ligament, moving the diagnosis towards apical periodontitis. A periapical radiograph then shows the deep caries approximating the pulp and excludes a periapical radiolucency. The plan writes itself: irreversible pulpitis in a restorable tooth means root canal treatment, with analgesia in the interim; a tooth destroyed by caries is extracted. Run the same ladder for the child who presents not with pain but with a red mass protruding from a carious molar — probing reveals it is pulpal, and pulpectomy or extraction follows, not a curettage of "excess gum".
The hot-and-cold paradox
Examiners love asking why a patient with irreversible pulpitis walks in holding a bottle of cold water. The traditional explanation taught with Neville is that in a partly necrosing pulp, gases and tissue fluid expand with heat, raising intrapulpal pressure on already sensitized nerves, while cold contracts those gases and briefly drops the pressure. Whatever the final mechanistic word, the clinical teaching stands: heat that aggravates and cold that relieves is pulpitis until proved otherwise, and that patient's tooth is usually on its way to necrosis. The opposite trap is branding every sharp cold response a doomed pulp — dentine hypersensitivity and reversible pulpitis both give short, stimulus-bound pain and both deserve conservative care first.
Frequently asked questions
How is reversible pulpitis distinguished from irreversible pulpitis clinically?
Reversible pulpitis gives brief pain that stops with the stimulus and no spontaneous episodes; irreversible pulpitis gives prolonged, spontaneous pain, typically worse at night.
What is a pulp polyp?
Chronic hyperplastic pulpitis — extruded inflamed granulation tissue from a cariously exposed pulp, classically in a young molar; treatment is pulpectomy or extraction, not excision of the mass alone.
Why does a necrotic tooth turn grey-black?
Bacterial hydrogen sulphide reacts with haemoglobin breakdown products to form iron sulphide within dentinal tubules, staining the crown from within.
What does internal resorption look like?
A pink coronal spot clinically and a rounded, motheaten expansion of the pulp canal radiographically; urgent root canal treatment aims to arrest odontoclasts before perforation.
Are pulp stones clinically significant?
Rarely — they are incidental findings in ageing and attrition, though large canal-obliterating stones complicate endodontic access and negotiation.
Which type of pulpitis pain is relieved by cold?
Irreversible pulpitis in its early phase, a classical sign attributed to contraction of intrapulpal gases; its relief is temporary and the tooth still requires root canal treatment.