Development of tooth make easier

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

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
1. Initiation
2. Histo-differentiation
3. Morphodifferentiation
4. 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

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
Polyphyodont
Diphyodont
Monophyodont
• More than two sets
• Two sets of dentition
• Presence of only one set of
dentition for entire life
• All teeth have same shape without
distinctionHomodont
• Presence of different groups of teeth
Heterodont

7. Bunodont
• Primitive type of teeth seen in primates like cats, dogs,etc.
• Contains simple conical cusps
Haplodont
• Simplest cone form of teeth with single root
• Seen in reptiles like crocodile
• Only hinge movement of jaw seen
Triconodont
• Seen in early mammals
• 3 cusps arranged in line with largest cusp in the centre.
Tritubercular
Quadritubercular

8. Ankylosis
Pleurodont
Acrodont
With bone socket
Gomphosis
Thecodont
Tooth Attachment

9.  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

10.  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 27th 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.

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

13.  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

14. FATE OF DENTAL LAMINA
 Total 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.

15.  Subsequently hollows and form the oral vestibule between the
alveolar portion of the jaws and the lips and cheeks

16. Dental lamina
Primary
epithelial band
Vestibular
lamina
Oral vestibule
Dental lamina
Degenerates
Remnants of
cell rests of
serres
Lingual
extension
Germs of all
other
permanent
teeth
Distal
proliferation
Germs of
permanent
molars

18. 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

19. 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.

20. Cap Stage
Cap
stage
Outer and
inner
enamel
epithelium
Stellate
reticulum
Dental
papilla
Dental
sac

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

22. 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

23.  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

24. 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.

25. BELL STAGE
Bell
stage
Outer and
inner
enamel
epithelium
Stratum
intermedium
Stellate
reticulum
Dental
lamina
Dental
papilla
Dental
sac

27. 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

28.  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

29. 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

30.  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

31.  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

32.  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

33.  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

34. HERS
Epithelial
Diaphragm
Proliferation of cells
of epithelial
diaphragm
Differential growth
of epithelial
diaphragm in
multirooted teeth
Two or three roots
Proliferation lags
behind that of
pulpal connective
tissue
Apical foramen
Proliferation of cells
of connective tissue
of pulp
Differentiates into
odontoblasts
Core of the pulp

35. • The dental
laminae and
associated tooth
buds
• Requires
ectomesenchym
al-epithelial
interaction.
Initiation
• Starts at
initiation and
continues
successively in
the bud, cap, and
bell stage.
• Causes regular
changes in the
size and
proportions of
the growing
tooth germ.
Proliferation
• Differentiation
of cells occurs.
• Enamel and
dentin formation
occurs.
Histodifferentiation
• The basic form
and relative size
of the future
tooth is
established.
Morphodifferentiation
• Layer like
deposition of an
extracellular
matrix.
Appoposition

36. Nolla’s Stages of tooth
calcification

37. Clinical Consideration- Initiation
 ANODONTIA
 SUPERNUMERARY TEETH

38. Proliferation
 Fusion
 Gemination

39. Morphodifferentiation
 Talons cusp
 Dens in dente
 Microdontia
 Macrodontia

40. Histo-differentiation
 Dentinogenesis imperfecta
 Amelogenesis imperfecta

41. Apposition
 Enamel Hypoplasia
 Concrescence

42. 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

43. 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.

44. References
 Orban’s, Textbook of oral histology & embryology: 14th edition
 Ten Cate’s Oral Histology Development, Structure, and Function
Antonio Nanci : 7th 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: 4th edition