Development Of Teeth

Development of tooth make easier

1. PRESENTED BY- Dr. PARIKSHIT S.KADAM (JR-1) DEVELOPMENT OF TOOTH

2. CONTENTS Introduction Evolution of Dentition Types of dentition Terminologies Dental Lamina Vestibular Lamina Tooth Developmental stages • Bud stage • Cap stage • Bell stage • Advanced bell stage Hertwig’s epithelial root sheath and root formation

3. Histological Stages Initiation Histo -differentiation Morphodifferentiation Apposition Developmental defects Conclusion References

4. Tooth development or odontogenesis is the complex process by which tooth form from embryonic cells, grow, and erupt into the mouth. For human teeth to have a healthy oral environment, all parts of the tooth must develop during appropriate stages of fetal development. Primary (baby) teeth start to form between the sixth and eighth week of prenatal development, and permanent teeth begin to form in the twentieth week Introduction

5. Evolution OF Dentition Theory of Concrescence:- Fusion of two or more primitive conical teeth and each tubercle with its corresponding root form as single tooth. Theory of Trituberculy :- Derived from single reptilian tooth by secondary differentiation of tubercles and roots. Theory of multituberculy :- Results of reduction and condensation of primitive tuberculate teeth.

6. Types of Dentition

7. Tooth Attachment

8. Tooth :- Hard ,calcified structure found in the jaws and used for chewing food. - Two parts Crown and root. - Formed by enamel, dentin, pulp and cementum . Dental Lamina :- Lingual extension of primary epithelial band. Vestibular Lamina :- Buccal extension of primary epithelial band Successional Lamina :- Lingual extension of dental lamina. Stellate reticulum :- Star shaped cells presents between outer and inner enamel layer. Stratum intermedium :- Squamous cells presents between inner enamel epithelium and stellate intermedium . Terminologies

9. Dental Lamina The primitive oral cavity, or stomodeum , is lined by stratified squamous epithelium called the oral ectoderm. The oral ectoderm contacts the endoderm of the foregut to form the buccopharyngeal membrane. Membrane ruptures at about 27 th day of gestation and the primitive oral cavity establishes a connection with the foregut. 2- 3 weeks after the rupture of buccopharyngeal membrane, certain areas of basal cells of oral ectoderm proliferate rapidly, leading to the formation of primary epithelial band.

10. Maxillary Process Stomodeum Dental Lamina Mandibular Process Developing Tongue Primary Epithelial Band Ectomesenchyme

11. The band invades the underlying ectomesenchyme along each of the horseshoe shaped future dental arches . The dental lamina serves as the primordium for the ectodermal portion of the deciduous teeth

12. FATE OF DENTAL LAMINA T otal activity of dental lamina exceeds over a period of atleast 5 yrs. functions for a much briefer period since only a relatively short time elapses. Remnants of dental lamina persist as epithelial pearls or islands within the jaw as well as in the gingiva . These are referred as cell rest of serres .

13. Subsequently hollows and form the oral vestibule between the alveolar portion of the jaws and the lips and cheeks VESTIBULAR LAMINA

14. Tooth Developmental Stages

15. MORPHOLOGICAL PHYSIOLOGICAL 1. Dental lamina Initiation 2. Bud stage 3. Cap stage Proliferation 4. Early bell stage Histodifferentiation 5. Advanced bell stage Morphodifferentiation 6. Formation of enamel and dentin matrix Apposition

16. Bud Stage This is the initial stage of tooth formation where enamel organ resembles a small bud. In the bud stage, the enamel organ consists of peripherally located low columnar cells and centrally located polygonal cells.

17. Cap Stage

18. The outer enamel epithelium is separated from the dental sac, & the inner enamel epithelium from the dental papilla, by a delicate basement membrane

19. Enamel Niche : The enamel niche is seen where the tooth germ appears to have a double attachment to the dental lamina (the lateral and medial enamel strands). Appears as a funnel-shaped depression containing connective tissue. Transitory Structures A B

20. Localized mass of cells in the centre of the inner enamel epithelium. Forms a bulge into the dental papilla. It may represent an important signalling centre during tooth development ENAMEL KNOT Enamel knot

21. ENAMEL CORD The extension from the stratum intermedium into the stellate reticulum. When it completely divides the stellate reticulum into two parts, reaching the external enamel epithelium, it is termed the enamel septum . Where the enamel cord meets the external enamel epithelium, a small invagination termed the enamel navel may be seen.

22. BELL STAGE

23. ADVANCED BELL STAGE Characterized by the commencement of mineralization & root formation The boundary between the inner enamel epithelium & odontoblasts outline the future dentinoenamel junction Formation of dentin occurs first as a layer along the future dentinoenamel junction in the region of future cusps & proceeds pulpally & apically

24. The cervical portion of enamel organ gives rise to Hertwig Epithelial Root Sheath (HERS) This HERS outlines the future root & thus responsible for the size, shape , length & number of roots

25. Hertwig’s Epithelial Root Sheath and Root Formation The development of roots begin after enamel & dentin formation has reached the future cementoenamel junction The enamel organ plays an important role in root development by forming HERS, which models the shape of the root As the first layer of the dentin has been laid down, the epithelial root sheath loses its structural continuity and is close relation to the surface of the root

26. Its remnants persists as an epithelial network of strands or clumps near the external surface of the root These epithelial remnants are found in the periodontal ligament of erupted teeth and are called as rests of mallasez

27. The root sheath forms the epithelial diaphragm The outer & the inner enamel epithelium bend at the future cementoenamel junction into a horizontal plane, narrowing the wide cervical opening

28. It cannot be seen as a continuous layer on the surface of developing root In the last stages of the root development, the proliferation of the epithelium in the diaphragm lags behind that of the pulpal connective tissue

29. During the general growth of enamel organ, expansion of its cervical opening occurs in such a way that long tongue like extensions of the horizontal diaphragm develop Before division of the root trunk occurs, free ends of the horizontal epithelial flaps grow towards each other & fuse The single cervical opening is divided into 2 or 3 openings

30. Nolla’s Stages of tooth calcification

31. Clinical Consideration- Initiation ANODONTIA SUPERNUMERARY TEETH

32. Proliferation Fusion Gemination

33. Morphodifferentiation Talons cusp Dens in dente Microdontia Macrodontia

34. Histo -differentiation Dentinogenesis imperfecta Amelogenesis imperfecta

35. Apposition Enamel Hypoplasia Concrescence

36. Vascular and Nerve Supply during Tooth Development Vascular Supply: Clusters of blood vessels in dental follicle and papilla. 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

37. CONCLUSION Since development of tooth forms the base of dentistry, a thorough understanding and a sound knowledge is required by a dentist regarding the development stages of tooth & the anomalies related to it, so as to identify & treat them in a proper fashion.

38. References Orban’s , Textbook of oral histology & embryology: 14 th edition Ten Cate’s Oral Histology Development, Structure, and Function Antonio Nanci : 7 th edition. Avery JK: Embryology of the tooth. J Dent Res 30:490,1951 Oral anatomy, histology and embryology by B.K.B Berkovitz and G.R Holland: 4 th edition

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