Dental Anatomy: Notation, Morphology and Crown Form
What is examined
Dental Anatomy questions test whether you can name, number and mentally build any tooth in either arch, because every crown, pontic and denture tooth you make depends on that map.
Notation
- FDI two-digit system: the first digit is the quadrant taken from the patient's own upper right - 1 upper right, 2 upper left, 3 lower left, 4 lower right; the second digit is 1–8 from the midline. So 16 is the upper right first molar.
- Primary teeth use quadrants 5–8, so 55 is the upper right primary second molar.
- Palmer (A–E, 1–8) still appears in orthodontic correspondence; Universal 1–32 appears in US-sourced material.
Morphology rules
- Incisors: single root, mamelons on newly erupted centrals, cingulum lingually. The maxillary central is the widest anterior crown (about 8.5 mm); the mandibular central is the narrowest.
- Canines: one long root, cusp tip placed distal to the long axis of the root.
- Premolars: the maxillary first has two roots and two cusps; the mandibular first's lingual cusp is small and non-functional.
- Molars: maxillary first has four cusps plus the cusp of Carabelli; mandibular first has five cusps; maxillary molars have three roots, mandibular molars two.
- Proximal contact areas migrate cervically with age; embrasures let food escape the contact rather than trap it.
Worked example
A prescription reads "26 - full gold crown". First digit 2 = upper left quadrant, second digit 6 = first molar. Expect three roots (mesiobuccal, distobuccal, palatal), four cusps, a rhomboid occlusal outline and a crown wider buccolingually than mesiodistally. That tells you how to orient the die and where the margin will sit.
Traps
- Reading 26 as a lower right tooth (that is 46) ruins the case before you start.
- Confusing the patient's left with your left when surveying a cast.
- Treating a primary second molar like a scaled-down permanent first molar - its roots flare to clear the premolar.