HISTEM W16/17 Tooth Development and Eruption

Which week of fetal development does primary dentition and permanent dentition begin? 

• Week 6 = Primary dentition development begins → 20 teeth 

• Week 10 = Permanent dentition development begins → 32 teeth

  • any missing or supernumerary teeth are determined at this time. 

T or F - the first teeth for both primary and permanent teeth begin to develop in the maxillary anterior region first and then mandibular anterior region. The development progresses posteriorly from the anterior region.

FALSE → develops first in the MANDIBULAR ANTERIOR REGION and then maxillary anterior region.

Why does teeth development progress posteriorly from the anterior region?

It allows time for both jaws to grow and accommodate more teeth as development continues.

Label the stages of tooth development.

1. A = tooth bud

2. B = Cap

3. C = Bell

4. D = dentinogensis

5. E = amelogenesis

6. F = crown formation

7. G = root formation and tooth eruption

8. H = functional tooth.

REVIEW: What are the 5 stages pf developmental processes?

1. Induction

2. Proliferation

3. Differentiation

4. Morphogenesis

5. Maturation 

Describe the Initiation stage (6-7th week) of Odontogensis.

Initiation Stage (6th–7th week) → physiological process:

• First stage of tooth development (odontogenesis).

• Stomodeum is lined by ectoderm

  • Outer ectoderm gives rise to Oral epithelium

• Oral epithelium grows downward/deeper into the underlying ectomesenchyme

• Ectomesenchyme is INDUCED to produce the dental lamina

Key event: Inductive interaction between oral epithelium and ectomesenchyme begins tooth formation.

Clinical relevance: Disturbances here may cause anodontia (missing teeth) or supernumerary teeth (extra teeth).

What happens if there is a lack of initiation during teeth development?

Causes absence of a single tooth or multiple teeth

• Hypodontia - more common; less than normal teeth

  • commonly occurs to Perm MxLI, M3, MdPM2

• Anodontia - missing all teeth

**Abnormal initiation = extra teeth; supernumerary teeth/hyperdontia

Describe the Proliferation stage (8th week) of odontogenesis. 

Proliferation Stage AKA Bud Stage (8th week):

• Second stage of odontogenesis.

• Dental lamina proliferates into tooth buds (oval masses) that penetrate into ectomesenchyme 

  • future tooth germ

*each dental arch should have 10 buds (primary teeth)

What is successional (secondary) lamina? When is it initiated?

Precursor tissue for the formation of tooth buds of permanent teeth

• Initiated between 10th week and 10th month after birth.

  • Perm molars → 20th week in utero for M1; 5th year of life for M3

• Successional lamina is lingual the dental lamina of primary teeth.

Closer look at secondary lamina and tooth buds of permanent teeth.

What can happen if there are developmental disturbances during the Profliferation stage of Odontogenesis (Bud stage)?