Development of the teeth

Odontogenesis, or teeth development, is a process that includes the development of deciduous teeth, also called milk teeth or baby teeth; and permanent teeth.

Deciduous teeth begin to develop during week 6 - 7 of intrauterine life, whereas, development of permanent teeth begins during week 14 of intrauterine life and continues to even up to 5 years after birth!

Now, teeth are one of the most diverse organs in humans both morphologically and functionally.

The development of teeth begins around week 6, and from two tissue components: the primitive oral epithelium derived from ectoderm, and the underlying ectomesenchyme or dental mesenchyme.

The dental mesenchyme derives from craniofacial neural crest cells that migrate from the developing midbrain and the first two rhombomeres into the first branchial arch.

Now, the oral epithelium and the dental mesenchyme instructs each other in a sequential and reciprocal way to precisely determine the formation and location of highly specialized teeth, such as incisors, canines, premolars and molars.

The tooth development starts with a thickening of the primitive oral epithelium known as the primary epithelial bands- one on each jaw.

Each primary epithelial band soon splits into two; an inner, or lingual, dental lamina, and an outer, or buccal, vestibular lamina.

The vestibular lamina subsequently hollows and forms the vestibule of the mouth, which is the space between the alveolar portion of the jaws, lips, and cheeks.

Now, signal proteins such as FGFs, BMPs and ectodysplasin cause the cells within the dental lamina to start proliferating and to invaginate in the positions that correspond to the locations of the future teeth.

These localized enlarged projections within the dental lamina are known as the dental placodes.

Next, as the dental placodes continue to proliferate, the tooth undergoes morphogenesis which results in different teeth shapes.

This is guided by interactions between epithelial and mesenchymal tissues and progresses through distinct stages defined by morphological features of the dental epithelium: The bud, Cap and bell stages.