Primary Tooth Anatomy - Pediatric Dentistry

Overview

• Primary teeth have thinner enamel than permanent teeth (1mm vs 2mm on average).
• Enamel in primary teeth is more uniform in depth around the tooth.
• Dentin layer is also thinner, resulting in a relatively larger pulp.
• Thinner mineralized layers make primary teeth more prone to caries, tooth wear, and pulp exposure during restorations.
• Thinner enamel also means primary teeth appear more white compared to the yellowish tone of permanent teeth.

Enamel Rods

• Permanent teeth: enamel rods dip gingivally in the cervical third.
• Primary teeth: enamel rods point occlusally.

Cervical Bulge

• Prominent cervical ridge, especially notable in primary first molar (mesiofacial component).
• Roots of primary teeth are more divergent with a smaller or absent root trunk.
• Primary teeth tend to be wider mesiodistally and shorter incisogingivally compared to their permanent successors.

Individual Primary Teeth Characteristics

Maxillary Central Incisor

• Widest anterior tooth mesiodistally in both primary and permanent dentition.
• Only anterior tooth with a width greater than height.
• Prominent labial and lingual cervical ridges.

Maxillary Lateral Incisor

• No high-yield facts noted.

Maxillary Canine

• Widest anterior tooth in a faciolingual direction.
• Mesial cusp ridge is longer than the distal cusp ridge, causing the cusp tip to be offset to the distal.
• Longer and sharper cusp compared to the mandibular canine and its permanent successor.

Maxillary First Molar

• Crown resembles the maxillary first premolar with a small distal component visible from the occlusal view.
• Prominent cervical bulge, especially notable from occlusal view.
• CEJ dips more on the mesial half to accommodate the cervical bulge.
• Three-root form (similar to permanent maxillary molars): palatal, mesiofacial, distofacial roots.

Maxillary Second Molar

• Widest primary tooth in the faciolingual direction.
• Crown resembles the permanent maxillary first molar, including a cusp of Carabelli, oblique ridge, and distolingual groove.
• Only primary tooth with a cusp of Carabelli.
• Last primary tooth to erupt.

Mandibular Central Incisor

• Smallest tooth in a faciolingual direction.
• Most symmetric of all primary teeth.

Mandibular Lateral Incisor

• No high-yield facts noted.

Mandibular Canine

• No high-yield facts noted.

Mandibular First Molar

• Most unique tooth in the primary dentition.
• Resembles a combination of mandibular second premolar and mandibular first premolar.
• Most distinct mesiofacial cervical ridge and transverse ridge.
• Has an S-shaped cervical ridge due to CEJ dipping more on the mesial half.
• Distal triangular fossa.
• Mesio-lingual cusp is the highest and sharpest; mesio-buccal cusp is the largest.
• Four cusps and four pulp horns.
• Two-root form (similar to permanent mandibular molars).

Mandibular Second Molar

• Widest tooth mesiodistally in the primary dentition.
• Crown resembles the permanent mandibular first molar.
• Mesio-buccal, disto-buccal, and distal cusps are nearly equal in size (unlike in the permanent first molar).
• Five cusps in total.
• Two roots, with the mesial root containing two root canals.