Development of the dentition

The development of the dentition is a complex process that begins in the embryonic stage and continues through childhood into early adulthood. Here’s a quick recap of the key stages:

Embryonic Development

Initiation: The first sign of tooth development appears around the 6th week of embryonic life. The dental lamina forms, leading to the development of tooth buds.

The dental lamina is made up of 3 layers:

Endoderm: This is the inner most layer and forms the internal organs
Mesoderm: The middle layer forms muscle, connective tissue and importantly the pulp and dentine in teeth.
Ectoderm: This outer layer forms the enamel as well as hair, nails, sweat and saliva glands and skin.

Tooth bud formation follows the sequence below

Bud Stage: By the 8th week, tooth buds for the primary (deciduous) teeth start forming.
Cap Stage: The tooth bud develops a concavity, forming the enamel organ, dental papilla, and dental follicle.
Bell Stage: Differentiation of cells occurs, leading to the formation of enamel and dentine

The permanent tooth buds develop distal to the primary teeth, in sequences that follow the blood supply of the developing maxilla and mandible. The last tooth in each sequence is most likely to be missing in hypodontia:
– The third permanent molar is the last tooth in the permanent molar sequence
– **The second premolar is the last tooth in the buccal sequence (canine and premolars)
– The upper lateral incisor is the last tooth in the upper anterior sequence
– The lower central incisor is the last tooth in the lower anterior sequence (this is because the blood supply for the lower anterior segment emerges from the mental foramen and grows mesially to the midline

Postnatal Development

• Primary Dentition:
  • Eruption: The first primary teeth (usually the lower central incisors) emerge around 6 months of age
  • Completion: By the age of 3 years, all primary teeth have typically erupted

Transition to Permanent Dentition

• Mixed Dentition: Around 6 years of age, the first permanent molars and lower central incisors begin to erupt, marking the start of the mixed dentition phase
• Exfoliation: Primary teeth gradually exfoliate to make way for permanent teeth

It’s important to remember that the first permanent molars erupt behind the second primary molars, and some parents may not realise these are adult teeth.

Permanent Dentition

• Eruption: Permanent teeth continue to emerge, with the second molars appearing around 12 years of age
• Completion: The full permanent dentition, including third molars (wisdom teeth), is usually established by 19 years of age, although there is considerable variation

This process ensures that the teeth are properly aligned and functional for effective mastication, speech, and overall oral health. It is regulated by hundreds of genes (and many more we haven’t discovered yet!) and can be affected by genetic, environmental and systemic factors as we will describe in further weeks. To illustrate this, we will use the Tooth atlas developed at QMUL

How to use the tooth atlas

Start in the top left corner with the black arrow and then follow tooth development in a clockwise spiral until 15.5 years of age. On the right hand side of the atlas you have the tooth development times for the third permanent molars.

For example you can see that at 2.5 years of age, all the primary crowns and roots have formed. So if a child presents with an anomaly affecting the primary dentition, it must have happened before that age. You can also see that about a third of the crowns of the first permanent molars and incisors have developed, but also the tips of the permanent lateral incisors, canines, premolars and also second molars are starting to form. That explains why you sometimes see children presenting with Molar Incisor Hypomineralisation (MIH) also affecting the canines, premolars and second molars.

Remember that these are average tooth developmental ages and there will be gender and racial variations.

If you have any specific questions about any stage, feel free to ask!