Oral Biology
Core concepts
Oral biology links embryology, histology and physiology of the oral tissues. Candidates should be able to describe tooth development (initiation, bud, cap, bell; the enamel knot as signalling centre; reciprocal epithelial–mesenchymal induction), the dental lamina and successional lamina, and the timing of mineralisation. Know amelogenesis (secretory, transition, maturation; amelogenins, enamelin, ameloblastin; Tomes' processes) versus dentirogenesis (predentin, mantle dentine, odontoblast process, peritubular dentine) and the fact that enamel is acellular and cannot regenerate while dentine and cementum can.
Know the periodontal ligament fibre groups (alveologingival, dentogingival, dentoalveolar, transseptal, interradicular) and the gingival fibre groups, plus the concept of the biologic width (junctional epithelium + connective tissue attachment). Understand saliva: composition, the roles of parotid (serous), submandibular (mixed) and sublingual (mucinous) glands, primary versus secondary saliva modification in the duct, and the protective functions (buffer, lactoperoxidase, IgA, statherin, proline-rich proteins). Understand oral mucosa keratinised versus non-keratinised, and tongue papillae with their associated taste modalities. Include eruption and root resorption of primary teeth, and the microbiology of dental plaque - early colonisers (Streptococcus sanguinis, Actinomyces) and late colonisers (Fusobacterium, Porphyromonas, Treponema) in the classic coaggregation model.
Traps
- Enamel is formed before dentine in the crown, but dentine is formed before enamel at the cervical region - the cervical enamel is thinner.
- Ameloblasts die after maturation; odontoblasts persist for life.
- Confusing the reduced enamel epithelium with the dental papilla.
Rule of thumb
If a question asks which tissue cannot repair, the answer is almost always enamel. If it asks which tissue is avascular, again enamel.