ODONTOGENESIS

Dr. Brian E. Esporlas

Stages in the life cycle of a tooth1. GrowthPhysiologic processa. Initiationb. Prolifirationc. Histodifferentiationd. Morphodifferentiatione. Apposition2. Calcification3. Eruption4. apposition

3 developmental process before function

Grow Calcify Erupt

Unlike kidney and heart.. Afte growth .. Function

Unlike bone… growth and calcify… function

Initiation stage

6th weeks intra uterine life: first sign of tooth development

Dental lamina: represent the first sign of tooth development. This is the GERMINAL BAND OF EPITHELIUM

Function of dental lamina

Initiate the development of the whole deciduous dentition

Initiate the development of the succedenuous teeth, by proliferation of bud from enamel organ

Initiates the development of the accesional teeth from the distal extention of the dental lamina

Vestibular lamina

After the dental lamina, the vestibular lamina will arise as another ectodermal thickening, but anterior to the dental lamina.

Then this will split to form the vestibular groove the future vestibule.

Bud stage

At certain point on DL representing the location of 10 manibular and 10 maxillary deciduous teeth cells multiply still more rapidly and form a knob like projections oward the mesoderm

Down ward growth creating dental sac, dental papila and dental organ

For the mandibular anterior 6th to 7 weeks

Max anterior 7th to 7 ½ week

Deciduous molars 8th week

Cap stage

The epithelial bud will continue to proliferate and expand latrally

Defferent part of the bud will show unequal growth leading to the formation of a cap stage dental organ( with invagination)

3 layers of cap stage

Outer dental epithelium Inner dental epithelium Stellate reticullum

(enamel pulp, Filled with mucoid fluid

rich in albumin)Star shape cell During late cap stage Stratum intermedium :

flat cell between inner dental epithelium and stalate reticulum.

Enamel knot: bud like enlargement , germinal center for the demand of cell growth of tooth

Enamel cord: vertical extension of the enamel knot that maintain the cap shape dental organ

Enamel naval: attachment of enamel cord to outer dental epithelium

Bell stage

.Dental lamina2.Dental sac or follicle3.Outer dental epithelium4.Stellate reticulum5.Inner dental epithelium6.Dental papilla7.Enamel cord8.Enamel navel9.Blood vessel10.Enamel niche11.Successional dental lamina

Dental papilla

The invaginated part of the dental organ is occupied by condensation of mesenchymal tissues.

Peripheral cells ( cuboidal – columnar) differentiates into odontoblast through the stimulation of the cell of the IEE

ODONTOBLAST – formtive cell of dentin

Central part will be the pulp

Membrana preformativa

Former basement membrane (separating the dental papilla from the IDE

FUTURE dentino enamel junction

Tooth germ and dental sac

During bell stage, the mesodermal tissue arround the enamel orgarn and the dental papilla differentiates into connective tissue capsule, dental sac.

As a resulth 3 tooth germs are developed.

a. Dental organ – will give rise to enamel tissue

b. Dental papilla – give rise to dentin and pulp

c. Dental sac – give rise to cementum, pdl and alveolar bone.

Dental organ

Give rise to enamel Play an active role in the formation of

dentin Play a role in formation of root via HERS

or hertwig’s epithelial root sheath. (from the junction of the IDE and ODE)

Produces enamel cuticle: last product of ameloblast

Remain as epithelial attachment of the neck of the toth after the tooth has erupted

histodifferentiation

Peripheral cells of the inner dental epithelium differentiates into ameloblast (formative cells of enamel)

With the influence of the ameloblast, the formative layer of dentin known as the ODONTOBLAST are formed from the cells of the periphery of the dental papill

Morphodifferentiation

The shape and form of the crown is determine by the membrana preformativa

Fate of dental lamina

The remnant should be calcified and be resorbed by osteoclast because it has no function

But, some group of epithelial cells may persist to stay (called gland of serres) and differentiates into ENAMEL MASS, SUPERNUMERARY TEETH, TUMORS OR CYST ( ameloblastoma)