Biomedical Sciences: Structure, Function, and Mechanisms
What the exam expects
Biomedical sciences underpin every clinical decision, so questions test structure–function links rather than isolated facts. Know tooth histology: enamel is the only ectodermal tissue of the tooth, is acellular, roughly 96% mineral, and cannot regenerate; dentin is tubular and formed by odontoblasts; cementum is avascular and anchors periodontal ligament fibers. Pulpal blood enters through the apical foramen, and because the pulp sits in a rigid chamber, inflammation produces pain.
The periodontium comprises gingiva, periodontal ligament, cementum, and alveolar bone. Principal fibers (alveolodental, transseptal) and gingival fiber groups resist occlusal force. Know trigeminal branches: maxillary molars receive the posterior superior alveolar nerve, premolars and anteriors the middle and anterior superior alveolar; mandibular teeth receive the inferior alveolar nerve, with the mental nerve supplying premolars and incisors and the lingual nerve carrying lingual gingiva and anterior tongue sensation.
Microbiology: supragingival plaque is Gram-positive, saccharolytic, and facultative; mature subgingival biofilm shifts to Gram-negative anaerobic proteolytic species - Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola (red complex), with Aggregatibacter actinomycetemcomitans in aggressive disease.
Pharmacology traps: epinephrine with nonselective beta blockers can precipitate hypertensive crisis; bisphosphonates and antiangiogenic drugs predispose to medication-related osteonecrosis; antibiotics are adjuncts only. Pathology: distinguish acute from chronic inflammation and dysplasia (premalignant epithelial change) from hyperplasia.
Rule of thumb: enamel is ectodermal; dentin, pulp, and cementum derive from ectomesenchyme. Worked example: anesthetizing a mandibular first molar requires the inferior alveolar nerve for the pulp plus the long buccal nerve for buccal soft tissue.