Dental Anatomy, Oral Histology and Oral Physiology
Dental Anatomy and Tooth Morphology
Nomenclature and chronology
Master both numbering systems: Universal (1–32, starting at the maxillary right third molar) and FDI two-digit (quadrants 1–4 permanent, 5–8 primary). Primary dentition begins with the mandibular central incisor at 6–10 months; the first permanent tooth to erupt is the mandibular first molar at about 6 years, followed by central incisors, laterals, first premolars, then canines and second premolars, then second molars. Root completion lags eruption by roughly 2–3 years, which is why endodontic and orthodontic decisions in children must account for open apices.
Morphology you must be able to draw from memory
Maxillary first permanent molar: five cusps including the cusp of Carabelli, three roots, and an MB2 canal in the majority of teeth. Mandibular first molar: five cusps with three buccal, two roots, usually three canals (mesiobuccal, mesiolingual, distal). Maxillary first premolar: two roots, two canals. Mandibular first premolar: one root, one canal, with a lingual cusp much smaller than the buccal.
Primary versus permanent teeth
Primary crowns are bulbous with a marked cervical constriction, thinner enamel (about 0.5–1 mm) and dentine, proportionally larger pulps with high horns, flatter interproximal contacts, and roots that flare widely to accommodate the permanent successor. These features explain rapid caries progression and the risk of pulpal involvement in children.
Rule of thumb
When asked which tooth is most variable, think mandibular second premolar (2 or 3 cusps, 1–3 canals) and maxillary second molar (variable cusp number, fused roots). Trap: the cusp of Carabelli is on the maxillary first permanent molar and the maxillary second primary molar - not on the mandibular molars.
Oral Histology and Oral Physiology
Enamel and dentine
Enamel is about 96% mineral by weight, formed by ameloblasts that are lost at eruption, so enamel neither regenerates nor remodels. Know rods, the Hunter-Schreger bands (alternating rod directions) and gnarled enamel over cusps. Dentine is about 70% mineral, permeated by tubules containing odontoblast processes and fluid - the basis of hydrodynamic hypersensitivity. Distinguish primary dentine (formed before completion of the root), secondary dentine (slow, physiological, after completion) and tertiary/reactionary dentine (rapid, in response to injury).
Pulp, cementum and periodontal ligament
Pulp contains odontoblasts, a cell-free zone of Weil, a cell-rich zone and a central core. Cementum is acellular extrinsic fibre cementum cervically and cellular intrinsic fibre cementum apically; it is more resistant to resorption than bone. The principal periodontal fibres are alveolar crest, horizontal, oblique (the most numerous and the group that resists axial loading), apical and interradicular. The junctional epithelium attaches to the tooth by hemidesmosomes against an internal basal lamina - the weak point that permits pocket formation.
Physiology and histology traps
Oral mucosa is masticatory (keratinized: gingiva, hard palate), lining (non-keratinized) or specialized (dorsum of tongue, taste buds). Salivary acini are serous, mucous or mixed, with myoepithelial cells for expulsion. Gustation: sweet at the tongue tip, bitter posteriorly - but all taste qualities are detectable across the tongue; the old 'taste map' is a myth and a common distractor.
Rule of thumb
If a question asks which structure prevents epithelial downgrowth along the root, the answer is the junctional epithelium plus the gingival fibre apparatus; once these are lost, attachment loss becomes measurable.