Oral Biology & Pathology Flashcards

What is the major inorganic component of dental enamel?

Answer: Hydroxyapatite [Ca10(PO4)6(OH)2] — approximately 96% by weight

Dental enamel is approximately 96% inorganic by weight, primarily hydroxyapatite (calcium hydroxyapatite). The remaining 4% is water and organic matrix. This makes enamel the hardest biological substance in the human body.

What is the aetiology of dental caries according to the Keyes Circle?

Answer: Interaction of three factors: susceptible host (tooth), cariogenic microorganisms (Streptococcus mutans, Lactobacilli), and fermentable substrate (sugars) — all three must be present

The Keyes model (later expanded to include time) describes caries as arising from the interaction of susceptible tooth surfaces, cariogenic bacteria, and dietary fermentable carbohydrates over time.

What is the histological appearance of the 'resting line' in cementum?

Answer: Dark lines (incremental lines) representing periods of reduced cementogenesis, similar to von Ebner lines in dentine

Resting lines in cementum represent periods of reduced or absent cementum deposition during tooth development. They appear as distinct basophilic lines histologically, marking cyclical growth phases.

Which cells are responsible for dentine formation?

Answer: Odontoblasts

Odontoblasts are the dentine-forming cells derived from neural crest cells. They line the pulp chamber and extend processes into dentinal tubules (Tomes' fibres), producing predentine which mineralises to become dentine.

What is 'scalloped' basement membrane in the gingival epithelium?

Answer: The undulating interface between the epithelium and underlying connective tissue, formed by rete ridges and connective tissue papillae

The gingival epithelium has a scalloped (rete ridge) interface with the lamina propria. Rete ridges interdigitate with connective tissue papillae, increasing surface area and enhancing mechanical attachment.

What is the role of salivary immunoglobulin A (IgA) in oral defence?

Answer: Provides mucosal immunity by binding antigens and preventing bacterial adherence to oral surfaces without invoking complement

Secretory IgA (sIgA) is the predominant antibody in saliva. It agglutinates bacteria and blocks their adhesion to mucosal surfaces, providing non-inflammatory first-line immune defence without complement activation.