Stages in the life cycle of atooth1. GrowthPhysiologic processa. Initiationb. Prolifirationc. Histodifferentiationd. Morphodifferentiatione. Apposition2. Calcification3. Eruption4. apposition
3 developmental process beforefunction 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
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 tissueb. Dental papilla – give rise to dentin and pulpc. 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)