1. DEVELOPMENT OF TEETH, and ASSOCIATED STRUCTURES
By: Dr. Richa Khanna
Asst Prof.
Paediatric and Preventive Dentistry,
KGMU, Llko.

2. Specific Learning Objectives
You should be able to:
Enumerate different stages of tooth development
Describe characteristics features of each stage.
Describe vascular and nerve supply during tooth development
Describe stages of enamel formation.
Describe root formation during tooth development

3. …and is divided into the following stages
Development of dentition starts as early as the sixth week of prenatal life…
…and is divided into the following stages

4. PRENATAL STAGE
At 16 weeks small buds arise also on the lingual side. These are the early anlage of the permanent teeth.
Local buds arise at twenty different points on the labial side of dental lamina, representing the primordia of the deciduous teeth
Oral epithelium in both jaws thickens, forming
dental lamina
Duration: 6th weeks to 9 months in utero

5. The individual tooth formation consists of following stages:
1. Bud Stage
2. Cap Stage
3. Bell Stage

6. Bud Stage
The bud stage is characterized by the appearance of a tooth bud without a clear arrangement of cells.
It is characterized by rounded, localized growth of epithelium surrounded by proliferating mesenchymal cells.

7. Bud Stage
In the bud stage, the enamel organ consists of peripherally located low columnar cells and centrally located polygonal cells

8. Cap Stage
First signs of an arrangement of cells in the tooth bud occur in the cap stage.
The tooth bud grows around the ectomesenchymal aggregation, taking on the appearance of a cap, and becomes the enamel (or dental) organ.

9. Enamel organ
Dental follicle
Dental papilla
A small group of ectomesenchymal cells stops producing extracellular substances, resulting in an aggregation of these cells called
the dental papilla.
A condensation of ectomesenchymal cells called the dental follicle surrounds the enamel organ and limits the dental papilla
Eventually, the enamel organ will produce enamel, the dental papilla will produce dentin and pulp, and the dental follicle will produce all the supporting structures of a tooth

10. Histodifferentiation and morphodifferentiation takes place
Bell Stage
stellate
reticulum
outer enamel epithelium
Histodifferentiation and morphodifferentiation takes place
Dental organ is bell-shaped during this stage, and the majority of its cells are called stellate reticulum because of their star-shaped appearance
 Cuboidal cells on the periphery of the dental organ are known as outer enamel epithelium.

11.  The columnar cells of the enamel organ adjacent to the dental papilla are known as inner enamel epithelium.
The cells between the inner enamel epithelium and the stellate reticulum form a layer known as the stratum intermedium.
stratum intermedium.
outer enamel epithelium
inner enamel
epithelium

12. The rim of the dental organ where the outer and inner enamel epithelium join is called the cervical loop
The dental lamina disintegrates, leaving the developing teeth completely separated from the epithelium of the oral cavity.
Sometimes, these epithelial cells will persist and are called “epithelial pearls”or “cell rests of Serre”
Clinical significance: Cysts will develop in these (eruption cysts) and prevent eruption, or they may form odontomas(tumors) or may form supernumery teeth.

13. Enamel Knot:
Densely packed accumulation of cells projecting from the inner enamel epithelium into enamel organ. Exact role not known, but currently believed to be the organizational center for cusp development

14. Enamel niche :
It is an artifact produced during sectioning of the tissue.It occurs because the enamel organ is a sheet of proliferating cells rather than a single strand and contains a concavity filled with ectomesenchyme

15. Crown pattern determination
….Occurs in Bell stage

16. Vascular and Nerve Supply during Tooth Development
Vascular Supply:
Clusters of blood vessels in dental follicle and papilla.
Clustering of vessels in papilla coincide with position
of root formation
Enamel organ is avascular, however vessels seen in
close association in the follicle
Nerve Supply:
Initially noted in the dental follicle during bud to cap stage
However after start of dentinogenesis, seen in dental papilla
Nerve fibers do not enter enamel organ

17. Deposition of dental hard tissues is called “apposition”
Stages of Apposition
1.Elongation of inner dental epithelium
2.Differentiation of odontoblasts
Differentiation of odontoblasts from ectomesenchymal cells are induced by influence from the inner dental epithelium
3.Formation of dentin
First layer of dentin appears at the cusp tips and progresses cervically
As the organic matrix of dentin is deposited, the odontoblasts move
towards the center of the dental papilla, leaving behind cytoplasmic
extensions which will soon be surrounded by dentin. Therefore, a
tubular structure of dentin is formed.

18. The formation of enamel is called amelogenesis.
At the same time or soon after the first layer of dentin (mantle dentin) is formed, the inner dental epithelial cells differentiate into ameloblasts and secrete enamel proteins.
The boundary between the odontoblasts and inner dental epithelium defines the future dentino-enamel junction.
The formation of enamel is called amelogenesis.

19. Ameloblasts goes through following functional stages:
Morphogenetic.
Histodifferentiation
Secretory
Maturation
Protection:

20. Time Line of Human Tooth Development
Age Developmental Characteristics
42 to 48 days Dental lamina formation
55 to 56 days Bud stage; deciduous incisors;
canines and molars
14 weeks Bell stage for deciduous teeth;
bud stage for permanent teeth
18 weeks Dentin and functional ameloblasts
in deciduous teeth
32 weeks Dentin and functional ameloblasts
in permanent first molars

21. long, or is curved or straight
ROOT FORMATION
Development of root begins after the enamel and dentin formation has reached the future cementoenamel junction
Epithelial cells of the inner and outer dental epithelium proliferate from the cervical loop of the enamel organ to form the Hertwig’sepithelial root sheath.
The root sheath determines if a tooth has single or multiple roots, is short or
long, or is curved or straight

22. ROOT FORMATION

23. FORMATIONOF PDL AND CEMENTUM
As the root sheath fragments, the dental follicle cells will penetrate between the epithelial cells and lie close to the newly formed root dentin.
These cells will differentiate into cementoblasts, which will make cementum
Fibers of the periodontal ligament, which will also form from the cells of the dental follicle will get anchored in the organic matrix of the cementum which will later get mineralized

24. Specific Learning Objectives
You should be able to:
Enumerate different stages of tooth development
Describe characteristics features of each stage.
Describe vascular and nerve supply during tooth development
Describe stages of enamel formation.
Describe root formation during tooth development