Pulp and Periapical Biology and Pathology
The Pulp and Periapical Biology and Pathology domain tests how normal pulp physiology becomes inflammation, necrosis, and periapical disease, and how those processes explain clinical tests. Expect questions on fibre types, pulp-space compliance, host response, and the radiographic limits of diagnosis.
Core rules
- Healthy pulp has odontoblasts, a cell-free zone, a cell-rich zone, and a pulp core; low compliance means even modest oedema raises tissue pressure and can collapse venules.
- A-delta fibres are myelinated and mediate sharp, stimulus-evoked pain; C fibres are unmyelinated and produce dull, lingering pain.
- Periapical radiolucency reflects bone loss, not the first day of inflammation; granuloma and cyst are distinguished histologically, not reliably by radiograph.
- Condensing osteitis is a sclerotic response to low-grade infection, common in young patients.
- Bacterial products drive most apical periodontitis; antibiotics do not remove the intraradicular source.
Worked example
A 35-year-old reports a 20-second lingering cold response in a molar with deep caries. Percussion is normal and the periapical radiograph shows intact lamina dura. The lingering response indicates symptomatic irreversible pulpitis; normal percussion and radiograph argue against symptomatic apical periodontitis. The plan is pulp extirpation or root canal treatment, not antibiotics.
Traps that cost marks
Equating a radiolucency with pulpitis; assuming a necrotic tooth must hurt; calling all apical radiolucencies cysts; and treating pulpitis with antibiotics instead of removing the pulp source.