1. Development of teeth

2. Introduction 6th week of intra uterine life
Stomatodeum (primitive oral cavity) consists of epithelium and connective tissue
Complex process involving epithelium & mesenchymal interactions.
Connective tissue contains cells derived from neural crest hence called as ectomesenchyme.
Horseshoe shaped band like proliferation of epithelium forms the DENTAL LAMINA
Dental lamina further forms the enamel organ of the developing teeth

4. Dental lamina further proliferates at 10 points corresponding to 10 decidous teeth.
Lingual extension – permanent successors
Buccal extension – vestibular lamina
Distal extension – permanent molars
Dental lamina Enamel organ
Ectomesenchymal condensation – Dental papillae
Dental follicle / sac
Enamel organ forms ENAMEL
Dental papillae forms DENTIN & PULP
Dental follice forms CEMENTUM, PERIODONTAL LIGAMENT
& ALVEOLAR BONE

5. Oral epithelium Dental lamina Enamel organ Future dental papilla

6. Stages of tooth development
Tooth formation is a continuous process based on the shape of the enamel organ it is divided into stages
Bud Stage
Cap Stage
Early bell stage
Advanced bell stage
Based on the physiologic phase the development of tooth can be also divided in to physiologic stages
Initiation
Proliferation
Histodifferentiation
Morphodifferentiation
Apposition

7. BUD stage The enamel organ resembles a bud
It consists of peripheral low columnar cells & central polyhedral cells
Ectomesenchymal condensation can be seen
Difference between dental papillae and dental follicle is not evident

8. CAP Stage
Unequal proliferation transforms the bud into a cap like structure
Enamel organ shows 3 distinct layers
Outer enamel epithelium – convex part– cuboidal cells
Inner enamel epithelium – concave part – columnar cells
Stellate reticulum - polygonal (star shaped network)
polygonal cells produce albumin increase in intercellular fluid cushion like effect protects enamel forming cells.

9. CAP Stage
Enamel knot, cord, septum, navel – transient structures seen in the center of enamel organ.
Enamel knot – knob like accumulation
Enamel cord – vertical extension of knot
Enamel septum – knot extending from inner enamel epithelium to outer enamel epithelium dividing the enamel organ
Enamel navel – depression on the outer surface of enamel organ
Earlier thought to be only reservoir for dividing cells but now known to act as signaling center & plays a role in determining the shape of the tooth.
The ectomesenchyme becomes more cellular and occupies the concavity of the enamel organ – Dental Papilla
Part of the ectomesenchyme which is more fibrous and surrounds both the enamel organ & papilla – Dental follicle

11. Early Bell Stage

12. Early Bell Stage Enamel organ assumes bell shape
4 distinct layers – 3 of cap stage and stratum intermedium.
Inner enamel epithelium converts to ameloblasts
“Reciprocal induction” begins
Cervical loop is appreciated
Dental lamina disintegrates – cell rests of serres (epithelial pearls)
Dental papilla & dental follicle become more organized.
“Membrana Preformative” – Future dentinoenamel junction

13. Advanced Bell Stage

14. Advanced Bell Stage
Ameloblasts and odontoblasts can be clearly demarcated.
Enamel and Dentin formation begins (reciprocal induction)
Stellate reticulum collapses to facilitate nutrition.
After hard tissue formation dental papilla is known as dental pulp.
Hertwigs epithelial root sheath proliferates from cervical loop leading to root formation.
Fibres of dental sac become more organized to resemble periodontal ligament.

15. Reciprocal Induction

16. Root Formation
Hertwigs epithelial root sheath (HERS) consists of inner & outer enamel epithelium.

17. Hard tissue formation reaches the future CEJ [cervical loop] HERS proliferates downwards inner cells induce dental papillae cells to differentiate into odontoblasts formation of radicular dentin rupture of HERS [cell rest of mallasez] Dental follicle comes in contact with dentin differentiation of cementoblasts & cementum formation.

18. Formation of multirooted teeth
Cell rests of mallasez
Enamel pearls & Epithelial pearls

19. Physiologic stages of tooth development
Initiation: induction by epithelial – mesenchymal interaction
Proliferation: increases in size and grows from bud to cap & bell stages
Histodifferentiation: basic cells transform into various layers and assume their functions, i.e. become specialized.
Morphodifferentiation: basic size and form of the tooth are determined.
Apposition: deposition of hard tissues.

20. Applied aspects Enamel hypoplasia Mottled teeth Turners hypoplasia
Anodontia
Supernumerary teeth
Taurodontism
Dens invaginatus
Odontogenic cysts & tumors
Dens evaginatus
Enameloma

21. OVERVIEW