Tooth Development

enamel organ: growth of dental lamina, 10 in maxilla and 10 in mandible arranged in the form of horse shoe shape
Dental papilla : ectomesenchymal condensation below the enamel organ
Dental sac or dental follicle: ectomesenchyme surrounding enamel organ and dental papilla

Soon after tooth development the dental lamina starts degenerate
In third molar region:5 years
As the tooth develops the connection breaks and islands of epithelial cell remain within the jaws and gingiva – “cell rests of serres”

enamel organ resembles a small bud
peripherally located low columnar cells and centrally located polygonal cells
The surrounding mesenchymal cells proliferate results in condensation of cells in 2 areas

– Dental papilla

– Dental sac

unequal growth in different parts of the tooth bud
Shallow invagination on the deep surface of bud
Peripheral cells :cuboidal, cover the convexity of the cap-outer enamel epithelium
cells in the concavity of the cap:columnar cells-inner enamel epithelium
Polygonal cells begin to separate due to water being drawn into the enamel organ from the surrounding dental papilla: star shaped: stellate reticulum
The cell in the center of the enamel organ are densely packed and form the enamel knot: acts as a signaling centers
a verticle extension of the enamel knot:enamel cord: reservoir of the dividing cell

Due to continued uneven growth of the enamel organ it acquires a bell shape
Shape of the crown is decided
Inner enamel epithelium:tall columnar cells called ameloblasts
- These cells attached to one another by junctional complexes laterally and to cells in stratum intermedium by desmosomes
- a strong influence on the underlying mesenchymeal cells of dental papilla which later differentiates into odontoblasts
Stratumintermedium: A few layers of squamous cells, between the inner enamel epithelium and the stellate reticulum
- closely attached by desmosomes & gap junctions
- essential to enamel formation
Stellate reticulum: expands further due to continued accumulation of intra cellular fluid
- As the enamel formation starts, the stellate reticulum collapses to a narrow zone thereby reducing the distance between the outer and inner enamel epithelium
Outerenamel epithelium: Low cuboidal cells- These cuboidal cells later assumes a columnar form and produce dentin
- Thrown into folds which are rich in capillary network, this provides a source of nutrition for the enamel organ
- Before the inner enamel epithelium begins to produce enamel. Peripheral cells of the dental papilla differentiate into odontoblasts
Dental lamina: extend lingually- successional dental lamina as it give rise to enamel organs of permanent teeth
Dental sac: Circular arrangement of fibers and resembles a capsule around the enamel organ- form the periodontal ligament fibers that span between the root and the bone

mineralization and root formation
The junction between the inner enamel epithelium and odontoblasts outlines the future dentino-enamel junction
Formation of dentin occurs first along the future dentinoenamel junction in the region of future cusps and proceed pulpally and apically
After the first layer of dentin is formed, the ameloblasts lay down enamel over the dentin in the future incisal and cuspal areas
The cervical portion of enamel organ gives rise to hertwig epithelial root sheath (HERS): outlines the future root & thus responsible for the size shape and length & number of roots
Root formation: begin after enamel & dentin formation has reached the future cementoenamel junction
HERS remnants: rests of mallasez

1. The successors of deciduous teeth develops form_______?

A. Successional lamina
B. Dental lamina
C. Stellate reticulum
D. Neutral ectodermal cells

Answer:A