Dental Anatomy, Embryology and Oral Histology
This domain tests tooth morphology, chronology of development, and microscopic structure of oral tissues. Questions ask you to identify teeth from features and to link development to clinical anomalies.
Core rules
- Permanent maxillary first molar has a rhomboid occlusal outline, three roots, and a cusp of Carabelli; mandibular first molar has five cusps and two roots.
- Primary molars are smaller and more bulbous, with markedly constricted cervical regions.
- Enamel is acellular and cannot regenerate; ameloblasts are lost after eruption.
- Dentin is laid down throughout life; peritubular dentin narrows tubules with age.
- Bell stage is characterized by enamel organ shaping and dental papilla differentiation.
Worked example
A extracted permanent tooth has a rhomboid occlusal table, three roots, and a prominent fifth cusp on the mesiolingual surface. The tooth is a permanent maxillary first molar. The rhomboid outline and three roots separate it from maxillary second molar, which is more triangular and has fused roots. The mesiolingual fifth cusp is the cusp of Carabelli, a stable identifying feature.
Traps
- Do not confuse the primary second molar with the permanent first molar; primary teeth are whiter and more constricted.
- Enamel rods run obliquely; do not describe enamel as living tissue.
- Root completion occurs after eruption, so a newly erupted tooth may have an open apex.
- Cementum is more cellular at the apical third.