...

1. “YOU NEVER KNOW WHERE YOU ARE GOING UNLESS
YOU KNOW WHERE YOU CAME FROM’’
17-05-2021 1

2. 17-05-2021 2
DEVELOPMENT OF TOOTH
&
PERIODONTIUM
Guided by:
Dr. Monica Mahajani
Dr. Chandrahas Goud
Dr. Anup Shelke
Dr. Subodh Gaikwad
Dr. Anup Gore
Dr. Kuldeep Patil
Presented by:
Dr. Chavan Sneha S.
(1ST Year PG)

3. DEVELOPMENT
17-05-2021 3
“Progression towards maturity”
- TOAD

4. PERIODONTIUM
Greek meaning, “PERI”-AROUND
“ODONT”-TOOTH
It is defined as,
The soft & specialized connective tissues
supporting & investing the tooth & consists of cementum,
periodontal ligament(PDL), bone lining the alveolus (socket), &
that part of gingiva facing the tooth.
-RICHARD TEN CATE’S 8th edi.
17-05-2021 4

5. CONTENTS
 INTRODUCTION
 DEVELOPMENT OF TOOTH
 DEVELOPMENT OF CEMENTUM
 DEVELOPMENT OF PERIODONTAL LIGAMENT
 DEVELOPMENT OF ALVEOLAR BONE
 DEVELOPMENT OF GINGIVA
 CONCLUSION
 REFERENCES
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6. INTRODUCTION
• The actual development of teeth starts at approximately 6 to 7
weeks after conception.
• It occurs by the interaction of the oral epithelial cells and the
underlying mesenchymal cells.
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7. Development:
• The epithelium of the primitive oral
cavity is called Oral Ectoderm. This
oral ectoderm contacts the
endoderm of the foregut to form the
buccopharyngeal membrane.
• At about 27th day, this membrane
ruptures and a primitive oral cavity
establishes connection with foregut.
• The most connective tissue cells
underlying the oral ectoderm are
ectomesenchyme in origin.
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8. • After 2 to 3 weeks of the rupture, the cells of oral ectoderm
proliferate and forms a continuous band of thickened epithelium
around the mouth in upper and lower jaws.
• This band is horse shoe shape. Each band is known as primary
epithelial band.
• At about 7th week, this band divides into an inner process
called dental Lamina and outer process called the vestibular
lamina.
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9. 17-05-2021 9

10. 17-05-2021 10
-RICHARD TEN CATE’S 9th edi.
Cranial neural crest cells

11. 17-05-2021 11

12. Epithelium mesenchymal interaction:
• The neural crest migrate into the Ist brachial arch,
which gets deposited and forms a band of
ectomesenchyme beneath the epithelium of the
primitive oral cavity (Stomodeum).
• Then the epithelium of the stomodeum releases
factors which initiates epithelial mesenchymal
interaction.
• These interactions are a series of programed,
sequential and reciprocal communication between
the epithelium and mesenchyme by signaling
molecule are in the form off growth factors, genetic
factors and extra cellular matrix.
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13. 17-05-2021 13

14. PRIMARY EPITHELIAL BAND (roughly
horseshoe shaped) (forms at 6th week of embryogenesis)
DENTAL LAMINA VESTIBULAR LAMINA
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-Present Labial or buccal to dental lamina
-Proliferation of vestibular lamina into
mesenchyme
-Rapidly enlarges and then degenerate to form
cleft vestibule
-Shows continuous and localized
proliferative activity
-Forms series of epithelial
outgrowth
-Determines future deciduous
tooth position
FATE: Total activity is about 5 years.

15. FATE OF DENTAL LAMINA:
• It is evident that the total activity of the dental lamina extends
over a period of at least 5 years.
• As the teeth continue to develop, they lose their connection with
the dental lamina. They later break up by mesenchymal
invasion, which is at first incomplete and does not perforate the
total thickness of the lamina.
• Remnants of the dental lamina persist as epithelial pearls or
islands within the jaw as well as in the gingiva. These are
referred to as cell rest of Serres.
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16. 17-05-2021 16
Epithelial pearls
Cell rest of Serres

17. 17-05-2021 17
A) The positions of the dental &
vestibular laminae in the four
quadrants are marked with
arrowheads & arrows,respectively
B) The two laminae at higher
magnification.

18. INITIATION OF TOOTH:
• Murine experiments indicate is that odontogenesis is initiated
first by factors resident in the first arch epithelium influencing
ectomesenchyme but with time this potential is assumed by the
ectomesenchyme.
• These experimental findings are mirrored by the expression
pattern of transcription and growth factors in these tissues.
• The earliest histologic indication of tooth development is at day
11 of gestation, which is marked by a thickening of the
epithelium where tooth formation will occur on the oral surface
of the first branchial arch.
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19. SIGNALS MEDIATING INITIAL STEPS
OF TOOTH DEVELOPMENT??
• To date, the earliest mesenchymal markers for tooth formation are
the LIM- homeobox (Lhx) domain genes (transcription factors),
Lhx-6 and Lhx-7 which are expressed in the neural crest–derived
ectomesenchyme of the oral portion of the first branchial arch.
• Experimental data demonstrate that the expression of Lhx-6 and
Lhx-7 results from a signaling molecule originating from the oral
epithelium of the first branchial arch.
• A prime candidate for the induction of Lhx genes is secreted
fibroblast growth factor-8; this growth factor is expressed at the
proper place and time in the first branchial arch and is able to
induce Lhx-6 and Lhx-7 expression in in vitro experiments.
• FGF-8 is known to establish oro aboral axis and position of tooth
germ.
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20. WHAT CONTROLS THE POSITION AND THE
NUMBER OF TOOTH GERMS ALONG THE
ORAL SURFACE?
• The Pax-9 gene is one of the earliest mesenchymal genes that
define the localization of the tooth germs.
• Shh gene have a role in stimulating epithelial cell proliferation
and its local expression at the sites of tooth development
• Lef-1 is first expressed in dental epithelial thickenings and
during bud formation shifts to being expressed in the
condensing mesenchyme
• Ectopic expression of Lef-1 in the oral epithelium also results in
ectopic tooth formation
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21. Molecular signaling during tooth development:
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-RICHARD TEN CATE’S 8th edi.

22. TOOTH TYPE DETERMINATION
• PATTERNING –
• determination of specific tooth types at their correct positions in
the jaws
• The determination of crown pattern is a remarkably consistent
process. Although in some animal teeth are all the same shape
(homodont), in most mammals they are different (heterodont),
falling into three families: incisiform, caniniform, and molariform.
• Two hypothetical models have been proposed to explain how
these different shapes are determined, and evidence exists to
support both
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23. FIELD MODEL:
• It proposes that the factors
responsible for tooth shape reside
within the ectomesenchyme in distinct
graded and overlapping fields for each
tooth family.
• The fact that each of the fields
expresses differing combinations of
patterning homeobox genes supports
this theory
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24. The homeobox code (field) model for dental
patterning
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25. CLONE MODEL:
• It proposes that each tooth class is derived from a clone of
ectomesenchymal cells programmed by epithelium to produce
teeth of a given pattern.
• In support of this contention, isolated presumptive first molar
tissues have been shown to continue development to form three
molar teeth in their normal positional sequence.
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26. 17-05-2021 26

27. INSTRUCTIVE SIGNALS FOR PATTERNING
• Signaling molecules often
regulate the expression
of transcription factors
that turn out to regulate
the expression of those
same signaling
molecules.
• At least 12 transcription
factors are expressed in
odontogenic
mesenchyme, and some
have redundant roles.
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28. REGIONALIZATION OF ORAL AND DENTAL
ECTODERM:
• Because regionally restricted expression of signaling protein
genes in oral ectoderm controls dental initiation and patterning,
it follows that the mechanisms that control the regional
restriction of ectodermal signals need to be understood.
• Misexpression of Wnt-7b in presumptive dental ectoderm
results in loss of Shh expression and failure of tooth bud
formation.
• This shows that the Wnt-7B gene represses Shh expression in
oral ectoderm and thus the boundaries between oral and dental
ectoderm are maintained by an interaction between Wnt and
Shh signaling.
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29. DEVELOPMENTAL STAGES
• Although tooth development is a continuous process, the
developmental history of a tooth is divided into several
morphologic “stages” for descriptive purposes.
• They are named after the shape of the enamel organ (epithelial
part of the tooth germ), and are called the:
Bud stage
Cap stage &
Bell stage
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30. BUD STAGE:
• Represented by the first epithelial inclusion
into the ectomesenchyme of jaw.
• The epithelium of the dental laminae is
separated from the underlying
ectomesenchyme by a basement
membrane.
• The supporting ectomesenchymal cells are
packed closely beneath & around the
epithelial bud.
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31. • Simultaneous with the differentiation of each dental
lamina, round or ovoid swellings arise from the
basement membrane. These are the primordia of the
enamel organs, the tooth buds.
• In the bud stage, the enamel organ consists of
peripherally located low columnar cells and centrally
located polygonal cells.
• Many cells of the tooth bud and the surrounding
mesenchyme undergo mitosis.
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32. CAP STAGE :
• increased mitotic activity and the
migration of neural crest cells into
the area the ectomesenchymal
• condense cells surrounding the
tooth bud.
• The area of ectomesenchymal
condensation immediately
subjacent to the enamel organ
• epithelial outgrowth, which
superficially resembles a cap sitting
on a ball of condensed
ectomesenchyme dental papilla
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Ref: Periodontology 2000, Vol. 24

33. 17-05-2021 33

34. • The enamel niche is an
apparent structure in histologic
sections, created because the
dental lamina is a sheet rather
than a single strand and often
contains a concavity filled with
connective tissue.
• Dental follicle is the condensed
ectomesenchyme limiting the
dental papilla and
encapsulating the enamel. It
forms cementum, periodontal
ligament, alveolar bone issue.
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35. Enamel knots • Each tooth germ has a single primary enamel
knot and secondary enamel knots at the tips of
the future cusps in molars at the cap stage.
• The enamel knot precursor cells can be
detected first at the tip of the tooth buds by
expression of the p21 gene, followed shortly
after by Shh.
• By the cap stage, when the enamel knot is
visible histologically, it expresses genes for
many signaling molecules, including Bmp-2,
Bmp-4, Bmp-7, Fgf-4, Fgf-9, Wnt-10b, Slit-1,
and Shh
• Fgf-4 and Slit-1 may be the best molecular
markers for enamel knot formation because
these are the only two genes that have been
observed in both primary and secondary knots.
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36. • a vertical extension of the enamel knot, called the enamel
cord
• When the enamel cord extends to meet the outer enamel
epithelium it is termed as enamel septum, for it would divide
the stellate reticulum into two parts.
• The outer enamel epithelium at the point of meeting shows a
small depression and this is termed enamel navel as it
resembles the umbilicus.
• These are temporary structures (transitory structures) that
disappear before enamel formation begins
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37. • Outer and inner enamel epithelium -The
peripheral cells of the cap stage are
cuboidal, cover the convexity of the “cap,”
and are called the outer enamel (dental)
epithelium. The cells in the concavity of
the “cap” become tall, columnar cells and
represent the inner enamel (dental)
epithelium.
• -The outer enamel epithelium is
separated from the dental sac, and the
inner enamel epithelium from the dental
papilla, by a delicate basement
membrane. Hemidesmosomes anchor
the cells to the basal lamina
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38. stellate reticulum
• The cells in the center of the enamel organ
synthesize and secrete glycosaminoglycans
into the extracellular compartment between
the epithelial cells
• Glycosaminoglycans are hydrophilic and so
pull water into the enamel organ.
• fluid increases the volume of the
extracellular compartment of the enamel
organ, and the central cells are forced
apart.
• Because they retain connections with each
other through their desmosome contacts,
they become star-shaped.
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39. BELL STAGE
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OUTER DENTAL
EPITHELIUM
Four different types of epithelial cells can be
distinguished on light microscopic
examination of the bell stage of the enamel
organ. The cells form the inner enamel
epithelium, the stratum intermedium, the
stellate reticulum, and the outer enamel
epithelium.
The junction between inner and outer
enamel epithelium is called cervical loop and
it is an area of intense mitotic activity.

40. Stratum intermedium
• A few layers of squamous cells form the
stratum intermedium, between the inner
enamel epithelium and the stellate
reticulum. These cells are closely attached
by desmosomes and gap junctions.
• The well-developed cytoplasmic
organelles, acid mucopolysaccharides, and
glycogen deposits indicate a high degree of
metabolic activity.
• This layer seems to be essential to enamel
formation. It is absent in the part of the
tooth germ that outlines the root portions of
the tooth which does not form enamel.
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41. • Dental papilla
• The dental papilla is enclosed in the invaginated portion of
the enamel organ.
• Before the inner enamel epithelium begins to produce
enamel, the peripheral cells of the mesenchymal dental
papilla differentiate into odontoblasts under the organizing
influence of the epithelium.
• First, they assume a cuboidal form; later they assume a
columnar form and acquire the specific potential to produce
dentin.
• The basement membrane that separates the enamel organ
and the dental papilla just prior to dentin formation is called
the membrana preformativa.
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42. ADVANCED BELL STAGE:
• Two important events occurs:
• 1) The dental lamina joining the tooth
germ to the oral epithelium fragments,
eventually separating the developing
tooth from the oral epithelium.
• 2) The inner enamel epithelium
completes its folding, making it possible
to recognize the shape of the future
crown pattern of tooth.
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43. • During this stage the boundary between inner enamel
epithelium and odontoblasts outlines the future dentino enamel
junction.
• Here, histologically enamel and dental formation can be
appreciated.
• As the hard tissue formation continue, the nutritional supply to
the ameloblasts from dental papilla is cut off and they derive
alternate source from dental sac.
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44. • The outer enamel epithelium becomes more irregular and
stellate reticulum collapses further to bring the blood vessels of
dental sac closer.
• Deposition of enamel proceeds coronally and cervically in all
regions from the dentino enamel junction.
• Once the enamel and dentine formation reach the cervical
region of tooth, root formation begins.
• The cervical region of enamel organ gives rise to epithelial root
sheath of Hertwig’s
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45. ROOT FORMATION:
• Once crown formation is completed, epithelial cells of the inner
and outer enamel epithelium proliferate from the cervical loop of
the enamel organ to form a double layer of cells known as
Hertwig’s epithelial root sheath
• As the inner epithelial cells of the root sheath progressively
enclose more and more of the expanding dental pulp, they
initiate the differentiation of odontoblasts from
ectomesenchymal cells at the periphery of the pulp, facing the
root sheath. These cells eventually form the dentin of the root.
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46. • Once a layer of radicular dentine is formed, in that region
HERS undergoes degeneration allowing the dental follicle cells.
• These dental follicle cells that come in contact with newly
formed dentine differentiate into cementoblasts and deposit
cementum on the outer surface of dentine.
• Radicular dentine formation continues apically and inward
while cementum formation continues apically and outward till
the entire length of root is formed.
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47. 17-05-2021 47

48. 17-05-2021 48
Epithelial root sheath and diaphragm.

49. Hertwig’s epithelial root sheath
• The rim of this root sheath, the epithelial diaphragm, encloses
the primary apical foramen.
• Once the desired length of root is formed, the lengthening of
HERS stops.
• The Hertwig’s Epithelial Root sheath do not undergo complete
degeneration instead remnants may persist which move away
from the root surface and remain in the pdl and are called ‘cell
rests of Malassez’.
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50. • Fig: Photomicrograph summarizing rooth
formation
• A)The root is beginning to form as an
extension of inner & outer enamel
epithelia in the cervical loop region,
which form bilateral structure called
Hertwig’s epithelial root sheath
• B)The differentiation of odontoblasts &
the formation of root dentin are shown.
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A B

51. AMELOGENESIS:
• It is formation of enamel by ameloblasts of
epithelial origin facing the odontoblast
layer.
• Differentiation of ameloblasts is initiated
by odontoblasts and the cells of stratum
intermedium via molecular signals, such
as BMP and FGF.
• The major proteins of the enamel matrix
are amelogenins, enamelins,
ameloblastins, and tuftelins.
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52. • At the same time or soon after the first
layer of dentine( mantle dentine) is
formed, the inner dental epithelial cells
differentiate into ameloblasts and secrete
enamel proteins.
• The ameloblasts will then start laying
down organic matrix of enamel against
the newly formed dentinal surface. The
enamel matrix will mineralize immediately
and form the first layer of enamel.
17-05-2021 52

53. DENTINOGENESIS
• Dentin is formed by odontoblasts that
differentiate from ectomesenchymal cells of
dental papilla with influence from the inner
dental epithelium.
• Differentiation of odontoblasts is mediated
by expression of signaling molecules and
growth factors in the inner dental epithelial
cells.( fibronectin;laminin;chondroitin sulfate;
TGF;BMP)
• Following differentiation of odontoblasts, first
layer of dentin is produced, MANTLE
DENTINE.
.
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54. • As the odontoblasts move inward pulpually, the odontoblast
process (Tomes fiber) will elongate and become active in
dentine matrix formation.
• it is initially called predentin .
• Mineralization is initiated in matrix vesicles where the first
apatite crystals are formed
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55. 17-05-2021 55

56. HISTOPHYSIOLOGY
• INITIATION:
Initiation induction needs ectomesenchymal-epithelial
interaction. It is Dental papilla mesenchyme can induce or
instruct the tooth epithelium and non tooth epithelium
Anodontia.
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57. • PROLIFERATION:
Enhanced proliferation activity ensues at the points of initiation
and results successively in the bud, cap, bell stages. These
changes causes regular changes in size and proportions of
growing tooth germ.
Oligodontia. Supernumerary teeth. Gemination or fusion.
17-05-2021 57

58. • HISTODIFFERENTIATION:
It succeeds the proliferation stage. The
formative cells of tooth development
undergo definitive morphological and
functional changes. This phase reaches
its highest development in bell stage
Regional odontodysplasia.
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59. • MORPHODIFFERENTIATION:
Basic size and relative size of future tooth is established by
differential growth. Advance bell stage shows
morphodifferentiation.
Microdontia, Macrodontia, Taurodontism, Concrescence,
Dilaceration, Dens invaginatus, Dens evaginatus.
17-05-2021 59

60. 17-05-2021 60
Taurodontism Concrescence Dilaceration

61. Evolution of periodontium
• The introduction of the socketed attachment of teeth is believed to have
arisen 200 million years ago when the earliest mammals were evolving
from their reptilian predecessors
• Three basic types of tooth attachment are observed in extant reptiles
(Osborn 1984; Gaengler 2000):
• 1. Acrodont type: characteristic of the Tuatara (Sphenodon punctatus) as
well as agamid lizards and chameleons, is characterized by ankylosis of
the tooth to the crest of the tooth- bearing element.
• 2. Pleurodont: the tooth being ankylosed to the pleura (lingually sloping
inner surface) of the tooth-bearing element.
• 3. Thecodont: where the teeth are set in sockets but do not ankylose to the
tooth-bearing elements. Instead, crocodile teeth show a fibrous attachment
to the wall of the alveolus by means of the periodontal ligament.
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62. 17-05-2021 62
Dens invaginatus Dens evaginatus

63. • APPOSITION:
Appositional growth is characterized by regular and rhythmic
deposition of extracellular matrix. Period of activity and rest
alternate at definite intervals
Amelogenesis imperfecta, Dentinogenesis imperfecta, Enamel
hypoplasia, Dentin dysplasia
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64. Amelogenesis imperfecta Dentinogenesis imperfecta
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65. Enamel hypoplasia Dentin dysplasia
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66. 17-05-2021 66
DEVELOPMENT OF TOOTH
&
PERIODONTIUM
Guided by:
Dr. Monica Mahajani
Dr. Chandrahas Goud
Dr. Anup Shelke
Dr. Subodh Gaikwad
Dr. Anup Gore
Dr. Kuldeep Patil
Presented by:
Dr. Chavan Sneha S.
(1ST Year PG)

67. 17-05-2021 67

68. Cementum is a Calcified, Avascular mesenchymal tissue
that forms the outer covering of the anatomic root.
Carranza 11th edition
17-05-2021 68
It was first demonstrated
microscopically in 1835 by two pupils
of purkinje.

69. • Two main sources of collagen fibers
• Sharpeys fibers ( Extrinsic) are the embedded portion of the
principal fibers of periodontal ligament and formed by
fibroblasts.
• Fibers that belong to the cementum matrix ( intrinsic) and
produced by cementoblast.
• Due to its lower crystallinity of mineral component : – has the
highest Flouride content – Readily decalcifies in the presence of
acidic conditions.
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70. • Non collagenous
• Non- collagenous proteins- play important role in
matrix deposition, initiation and control of
mineralization and matrix remodelling. Include:
Bone sialoprotein, osteopontin, tenascin,
fibronectin, osteocalcin.
• Proteoglycans- Chondroitin sulphate,hyaluronate,
heparan sulfate, biglycan and osteoadherin.
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71. • Growth factors- TGFß, bone morphogenetic
proteins (BMP’s),Platelet derived growth factors,
Osteoprotegerin (OPG).
• Cementum derived growth factor seen exclusively
in cementum.
 Is an insulin like molecule.
 Enhance proliferation of gingival fibroblasts and
periodontal ligament cells.
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72. Development of cementum
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73. 17-05-2021 73
Process of cementum development is called as “cementogenesis”.

74. cementogenesis:
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Deposition of dentin along the inner aspect of HERS
Breaking up of HERS along the newly formed dentin to come in
contact with cells of dental follicle
Differentiation of cementoblasts along the external surface of
the root
Protein secretion by cementoblasts mainly collagen &
proteoglycans which forms the organic matrix of the cementum
Phase of matrix maturation, which subsequently mineralizes
to form cementum

75. Varieties of cementum
• Two main types- (classified on the basis of
presence of cementocyte)
- Acellular ( primary)
- Cellular ( secondary)
• Both consist of interfibrillar matrix and
collagen fibrils.
• On the basis of the types of fibers
(extrinsic/intrinsic) presence or their
absence (afibrillar cementum).
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76. Development of acellular cementum
• Development of acellular cementum is associated with
secretion of enamel matrix protein (EMP) by HERS after
mineralization of first layer of dentin adjacent to the root.
• Enamel proteins including amelogenin & certain basement
membrane constituents are reported to be involved in epithelial-
mesenchymal reaction.
• HERS also secrete cementum related proteins like Bone
sialoprotein (BSP), osteopontin & fibrillar collagen
17-05-2021 76

77. • At the same time fibroblast precursors cells from
dental follicle come in contact with predentine matrix
and start depositing bundle of collagen fibrils to form a
thin layer of perpendicularly oriented “Sharpey’s fibers”
or “fringe fibers”.
• As the mineralization front advances, it contacts the
sharpey’s fibers and they undergo slow mineralization
to complete the process of acellular extrinsic fiber
cementum formation.
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78. 17-05-2021 78

79. Cementoid tissue & calcification of matrix
• The uncalcified matrix is called as cementoid.
• the growth of cellular cementum is a rhythmic process, and as
a new layer of cementoid is formed, the old calcifies.
• Gla proteins – osteocalcin & osteonectin acts as neucleators
for mineralization due to their strong affinity for calcium & BSP.
• Alkaline phosphatase promotes mineralization.
• Osteopontine regulates growth of apatite crystals.
• Major proteoglycan located in non-mineralized cementum is
keratan sulfates- lumican & fibromodulin.
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80. Development of cellular cementum
• A more rapidly formed & less mineralized variety of cementum
• divided into 2 stages:
Early stage in which extrinsic sharpey’s fibers produced by
fibroblasts are few
& traces of intrinsic fibers produced by cementoblasts are
randomly arranged.
Late stage of cementogenesis-
it closely resembles bone formation.
Cementoblasts and cementocytes are involved in the secretion of
intrinsic fibers.
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81. • The development of cementum has been subdivided into:
• Pre-functional stage
• Functional stage
• Pre-functional portion of the cementum is formed during root
development & is extremely long lasting process.
• The functional development of cementum, commences when the
tooth is about to reach the occlusal level & is associated with the
attachment of root to the surrounding bone & continues throughout
life. It is mainly during this stage that adaptive & reparative
processes are carried out by the biological responsiveness of
cementum.
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82. CEMENTUM ASSOCIATED CELLS
• Cementoblasts
• Cementocytes
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83. CEMENTOBLASTS
• Derived from dental follicle.
• Transformation of mesenchymal
cells of dental follicle.
• Cemento-progenitor cells
synthesize collagen and protein
polysaccharide.
• These cells have numerous
mitochondria, a well formed
Golgi- apparatus and large
amounts of granular
endoplasmic reticulum.
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Electron micrograph illustrating the insertion of
periodontal ligament (PDL) fiber bundles into cellular
intrinsic fiber cementum. Cementoid is seen at the
surface of the mineralized cementum. Cb,
Cementoblast.

84. CEMENTOCYTES
• Cementocytes in lacunae and the channels in which their
processes extend are called the canaliculi.
• The central cell mass may appear rounded or oval & diameter
ranges from 8-15 um.
• The cytoplasm is palely basophilic and the nucleus is centrally
located.
• Cementocytes communicate with each other through a system
of anastomosing canaliculi radiating from their body
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85. 17-05-2021 85
From Moss-Salentijn, L. 1972. Orofacial Histology and Embryology: A Visual Integration. Reproduced with permission from
F.A. Davis Company, Philadelphia, PA

86. • Histological observation of areas of root
resorption has shown that cementoblasts can
arise wherever viable dentin is exposed to the
soft tissue of the periodontal ligament. Induction
of cementoblasts from periodontal ligament cells
can apparently take place throughout life, as
evidenced by physiological areas of cemental
repair.
17-05-2021 86

87. • Cellular turnover among cementoblasts is
slow compared with that in the osteoblasts
that line the alveolus.
• Furthermore, it appears that cementoblasts
are capable of altering their rate of cementum
deposition
17-05-2021 87

88. CEMENTO ENAMEL JUNCTION
• Irregular fragmentation of HERS yields an equally irregular limit of
cervical enamel and an irregular onset of formation and deposition of
cementum.
• Consequently, the relationship between cementum and enamel at
the CEJ presents an irregular contour, as observed during scanning
electron microscope (SEM) analysis of the primary teeth
• The junction between the cementum and enamel at the cervical
region of the tooth is termed Cemento-Enamel junction
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Ref: Cementoenamel junction: An insightKharidi review ;Laxman Vandana, Ryana Kour Haneet;Journal of Indian Society
of Periodontology - Vol 18, Issue 5, Sep-Oct 2014

89. four TYPES OF RELATIONSHIP
EXISTS
• In about 60% cases cementum
overlaps the cervical end of enamel.
• In approx. 30% of all teeth
cementum meets the cervical end of
enamel.
• In 10% cases enamel and cementum
do not meet which can cause
accentuated sensitivity because of
exposed dentin.
• In about 1.6% of cases enamel
overlaps cementum.
17-05-2021 89
Cementoenamel junction: An insightKharidi review ;Laxman Vandana, Ryana Kour Haneet;Journal of Indian Society of
Periodontology - Vol 18, Issue 5, Sep-Oct 2014

90. 17-05-2021 90

91. CEMENTO-DENTINAL JUNCTION (CDJ)
• The terminal apical area of cementum where it joins the
internal root dentin is called cementodentinal junction or CDJ
• The nature of CDJ is of particular importance, because it
forms an interface between two very different mineralized
tissues. It is also of clinical importance because of the
processes involved in maintaining tooth function while
repairing a diseased root surface.
• Width of CDJ is 2 to 3um and remains relatively stable
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92. Intermediate cementum/ Hyaline layer:
• It is poorly defined zone near CDJ of certain teeth that
appears to contain cellular remnants of the Hertwigs
sheath embedded in a calcified group substance.
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93. DEVELOPMENTAL ANOMALIES
ASSOCIATED WITH
CEMENTOGENISIS
17-05-2021 93

94. CEMENTICLES :
• Are small, globular masses of
cementum found in approx 35% of
human roots.
• May not be always attached to the
cementum surface but may be located
free in Pdl.
• These may result from microtrauma,
when extra stress on sharpeys fibers
causes a tear in the cementum.
17-05-2021 94

95. • Are more commonly found in apical & middle third of root
and in root furcation areas
• May develop from calcified epithelial rests; around small
spicules of cementum or alveolar bone traumatically
displaced into the periodontal ligament; from calcified
Sharpey's fibers; and from calcified, thrombosed vessels
within the periodontal ligament
17-05-2021 95

96. ENAMEL PEARLS If some HERS cells remain attached to
forming root surface, they can produce focal deposits of enamel
like structures called ENAMEL PEARLS.
Clinical significance :
• They are plaque retentive structures.
• Promote periodontal disease.
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97. • If the overgrowth improves the functional qualities of the
cementum, it is termed as cementum hypertrophy.
• If the overgrowth occurs in nonfunctional teeth or if it is
not correlated with increased function, it is termed
cemental hyperplasia.
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98. Hypercementosis:
Appearance:
Occurs as a generalised thickening of
cementum, with nodular enlargement of
the apical third of the root.
It also appears in the form of spike like
excrescenses (cemental spikes) created
by either cementicles that adhere to the
root or the calcification of the periodontal
fibres at the site of insertion into the
cementum.
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99. • Hypercementosis of entire dentition may be seen in
patients with Paget's disease.
• Other systemic disturbances include acromegaly,
calcinosis, thyroid goiter, arthritis etc.
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100. Treatment:
• Hypercementosis itself does not need treatment.
• In multirooted tooth, sectioning of tooth may be required
before extraction.
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101. • Cemental aplasia or hypoplasia:
• Hypophosphatasia:
• Hypophosphatasia is due to an inborn error of metabolism.
• The basic disorder is a deficiency of enzyme alkaline
phosphatase in serum or tissues.
• This is characterised by loosening and premature
exfoliation of deciduous teeth, mainly anteriors.
• Exfoliated teeth microscopically show complete absence of
cementum or isolated areas of abnormally formed
cementum.
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102. Cemental Tear:
The detachment of a
fragment of cementum is
described as a cemental tear.
Cemental tears have been
reported in the periodontal
literature associated with
localized, rapid periodontal
breakdown.
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103. ANKYLOSIS:
• Fusion of cementum and alveolar bone and obliteration of the
periodontal ligament is called ankylosis. Results in resorption of
root and its replacement by bone tissue.
Ankylosis can also occur after:
• Chronic periapical infection
• Tooth reimplantation
• Occlusal trauma
• Around embedded teeth.
• More common in primary dentition
•
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104. 17-05-2021 104

105. • Treatment:
• No predictable treatment can be suggested.
• Treatment modalities range from a conservative
approach, such as restorative intervention to
surgical extraction of affected tooth.
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106. EXPOSURE OF CEMENTUM TO ORAL
ENVIRONMENT
• Exposed in cases of gingival recession leading to
pocket formation.
• Permeable to be penetrated by organic substances,
inorganic ions and bacteria.
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107. 17-05-2021 107

108. Possible Role of Cementum
in Periodontal Regeneration
A variety of chemotactic factors, adhesion molecules,
growth factors, and ECM constituents participate
together in the recruitment of cementoblast progenitors,
their expansion, and differentiation.
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109. 17-05-2021 109
Grzesik WJ, Narayanan AS. Cementum and periodontal wound healing and regeneration. Crit Rev Oral Biol Med. 2002;13(6):474-84
Cell activities required for new cementum and attachment formation and cementum components that possibly
regulate these processes.

110. PERIODONTAL LIGAMENT
• It is dense fibrous connective
tissue that is noticeably cellular
and contains numerous blood
vessels.
• Average width - 0.15mm to
0.38mm
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111. • The periodontal ligament (PDL) is composed of a
complex vascular & highly cellular connective tissue that
surrounds the tooth root & connects it to the inner wall of
the alveolar bone.
• Over the years it has been described by number of
terms:
• Desmodont
• Gomphosis
• Pericementum
• Dental periosteum
• Alveodental ligament
• Periodontal membrane
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112. 17-05-2021 112

113. Development of PDL begins with root formation, prior to tooth eruption
Continuous proliferation of IEE & OEE forms a cervical loop of tooth bud
Formation of HERS between the dental papilla & dental follicle
Sheath circumferentially encompassing dental papilla
Separate it externally from dental follicle cells
Root formation continue
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114. Cells in perifollicular area gain their polarity & cellular volume
Synthetic activity increases
These cells become elongated & contain increase amount of rough
endoplasmic reticulum, mitochondria & active Golgi complex
Actively synthesizing and depositing collagen fibrils & glycoproteins in the
developing PDL
Ligament mesenchymal cells begin to secrete
Assembles as collagen bundles
17-05-2021 114
Ref.:Orban’s Oral histology And Embryology, 13th edition

115. Development of principal fibers
• Immediately before tooth eruption & for sometimes there after,
active fibroblasts adjacent to the cementum of the coronal 1/3 of
the root, aligned in oblique direction to the long axis of the tooth.
• Soon, thereafter, first collagen fiber bundles of the ligament
become discernible. These are the precursors of the alveolar
crest fiber bundle group.
• Later, similar fibers are observed on the adjacent osseous
surface of the developing alveolar bone.
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116. • Both set of fibers, alveolar & cemental, continue to
elongate toward each other, ultimately to meet,
intertwine & fuse, & cross linking of individual collagen
molecules occur.
• By the time of first occlusal contact of the tooth with its
antagonist, the principle fibers around the coronal 1/3 of
the root, the horizontal group are almost completely
developed.
• Oblique fibers in middle third of the root are still being
formed.
• After complete root apex is formed, apical group of
fibers are developed.
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117. 17-05-2021 117

118. 17-05-2021 118

119. 17-05-2021 119

120. How Does PDL Fibers attach to Root surface???
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121. PDL homeostasis
• A remarkable capacity of PDL is that it maintains
its width more or less, despite the fact, it is
squeezed in between two hard tissues.
• Various molecules have been proposed, which
play a role in maintaining an unmineralized PDL.
• Bone sialoprotein
• osteopontin
• Matrix Gla proteins (Inhibitors of mineralization)
• Prostaglandins: Inhibit mineralized bone tissue
• Msx2 : Prevents osteogenic differentiation of
PDL fibroblasts by repressing cbfa1 activity
17-05-2021 121

122. • When the tooth finally comes in
function the alveolar crest fibers
is positioned nearer the apex.
• The horizontal fibers termed as
alveolar crest fibers have become
oblique once again but now the
difference is that the CEJ is
positioned in a coronal direction.
17-05-2021 122
A B C D
Fig: The development of principle fiber :
A: first forming alveolar creast fiber
B: Initially oblique
C: then horizontal
D: & then oblique again
-RICHARD TEN CATE’S 8th edi.

123. Cellular components:
• The periodontal ligament is known to have
heterogeneous population of fibroblasts.
• With the onset of root formation, the organelles in the
cell increases, collagen and ground substance
formation begin and fills the extracellular spaces.
• The developing periodontal ligament, as well as the
mature periodontal ligament, contains undifferentiated
stem cells.
• Experimental studies suggest that stem cells occupy
perivascular sites in the periodontal ligament and in
adjacent endosteal spaces
17-05-2021 123

124. ALVEOLAR BONE
DEFINITION:
• Bone is specialized C.T with calcified
intercellular substance
• Alveolar bone is specialized part of
maxillary and mandibular bone that
forms the primary support structure for
teeth
17-05-2021 124

125. DEVELOPMENT OF ALVEOLAR BONE
The process of bone formation is called as osteogenesis.
Alveolar bone is formed during fetal growth by intramembranous ossification.
OSTEOGENESISI
17-05-2021 125
Endochondral bone formation
-Long bones
-Flat bones end
Sutural bone growth
Intramembranous bone formation
-Flat bones of skull, clavicle &
mandible

126. Intramembranous bone formation
17-05-2021 126
Ref:Orban’s Oral Histology & Embryology 13th edition

127. 17-05-2021 127
Endochondral bone formation

128. Sutural bone growth
• Bone forms along suture margins
• Found in skull
• Fibrous joints between bones
• Allow only limited movement
• Helps skull and face to accommodate growing organs like eyes
and brain
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129. 17-05-2021 129
Fig: Sutural growth. A: Low-magnification light micrograph showing that the suture
connects two periosteal surfaces.
B: A higher magnification shows the developing inner osteogenic or cambium layer
and the central capsular layer.

130. • DEVELOPMENT OF ALVEOLAR BONE
• Alveolar process consists of bone which is formed both by
cells from the dental follicle (alveolar bone proper) & cells
which are independent of tooth development
• Maxilla & mandible develop-- 1st branchial arch or
mandibular arch.
• The maxilla forms within the maxillary process & mandible
forms within the fused mandibular processes of mandibular
arch.
• Both jaw bones start as small centres of
intramembraneous ossification around stomodeum
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131. Both maxilla and mandible develop intramembranously.
8th week in utero
Alveolar process develops from the dental follicle during eruption of tooth
Bell stage-- developing bone becomes closely related
The size of the alveolus is dependent upon the size of the growing tooth germ.
Resorption - inner wall of the alveolus Deposition -outer wall.
The developing teeth lie in a trough of bone -Tooth Crypt.
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132. Teeth separated from each other by the development of
interdental septa.
With the onset of root formation, interradicular bone develops
in multirooted teeth.
When a deciduous tooth is shed, its alveolar bone is resorbed.
Alveolar process gradually incorporated into maxillary or
mandibular body.
Permanent tooth moves into place, developing its own alveolar
bone from its own follicle.
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133. ALVEOLAR BONE
Alveolar bone proper Supporting alveolar bone
Lamellated bone Cortical plate
Bundle bone Spongy bone
17-05-2021 133
STRUCTURE OF ALVEOLAR BONE

134. • Alveolar bone proper:-
• it appears as thin radio opaque line
adjacent to socket, termed as lamina
dura.
• The alveolar bone proper forms the
alveolar wall that lines the tooth sockets,
and the supporting alveolar bone
consists of inner and outer cortical
plates.
• Its formation is initiated with the eruption
of the developing tooth.
17-05-2021 134

135. • At the late bell stage, bony septa and bony bridge
start to form, and separate the individual tooth germs
from another, keeping individual tooth germs in clearly
outlined bony compartment.
• At this stage, the dental follicle surrounds each tooth
germ, which is located between a tooth germ and its
bony compartment.
17-05-2021 135

136. • As the roots of teeth develop, the alveolar processes
increase in height. Also, cells in the dental follicle
start to differentiate into periodontal ligament
fibroblasts and cementoblasts responsible for the
formation of the periodontal ligament and cementum,
respectively.
17-05-2021 136

137. • At the same time, some cells in the dental follicle also
differentiate into osteoblasts and form the alveolar bone
proper.
• The formation of the alveolar bone proper is closely
related to the formation of the periodontal ligament and
cementum during root formation and tooth eruption
17-05-2021 137

138. • BONE REMODELING AND RESORPTION
• Bone is a dynamic tissue and is always undergoing changes to
adapt for functional forces, mesial drift, and eruption of teeth.
• There is constant formation and resorption of bone. Periods of
resorption alternate with periods of rest and repair.
• Lines seen in bone:
• Resting line: these lines correspond to the resting period in the
process of contineous bone formation.
• Reversal line: when a period of bone resorption is followed by bone
formation, a dark line is seen which seperates the new bone from old
bone, this resembles the shape of howships lacunae.
17-05-2021 138

139. 17-05-2021 139

140. Development of gingiva
• Gingiva, comprising of gingival epithelium and
connective tissue, is a portion of oral mucosa
that covers tooth bearing part of the alveolar
bone and cervical neck of tooth.
17-05-2021 140

141. Development of junctional epithelium:
• The ameloblasts shorten after the primary enamel
cuticle has been formed, and the epithelial enamel
organ is reduced to a few layers of flat cuboidal cells,
which are then called reduced enamel epithelium.
• During eruption, the tip of the crown approaches the
oral mucosa and the reduced enamel epithelium and
oral mucosa meet and fuse.
17-05-2021 141

142. • The reduced enamel epithelium remains
organically attached to part of enamel that has not
yet erupted.
• During transition from ameloblast to junctional
epithelium the changes in keratin expression occur
as a form of differentiation.
17-05-2021 142

143. • As the tooth erupts the reduced enamel
epithelium grows gradually shorter. A shallow
groove, gingival sulcus develops between gingiva
and surface of tooth. It deepens as a result of
separation of reduced dental epithelium from the
actively erupting tooth
17-05-2021 143

144. 17-05-2021 144
Ref:Jan Lindhe – Text Book Of Clinical Periodontology (4th edition)

145. Development of gingival sulcus:
• The gingival sulcus is the shallow, V shaped space
or groove between the tooth & the gingiva that
encircles the newly erupted tip of the crown.
• In the fully erupted tooth, only the junctional
epithelium persists.
• The sulcus consists of the shallow space that is
coronal to the attachment of the junctional
epithelium & bounded by the tooth on one side &
the sulcular epithelium on the other.
• The coronal extent of the gingival sulcus is the
gingival margin.
17-05-2021 145

146. Shift of the Dento-gingival junction
• Components:
1. Epithelial component is derived from
reduced dental (enamel) epithelium and oral
epithelium.
2. The connective tissue component is derived
from the lamina propria of the oral mucosa.
The attachment of the functional epithelium to
the tooth is reinforced with the gingival fibers,
which brace the gingival against the tooth
surface.
17-05-2021 146

147. Development of gingival connective tissue:
• Gingival connective tissue fibroblasts
originate from perifollicular mesenchyme, a
derivative of the stomodeal mesoderm
• During normal development of the
periodontium, gingival fibroblasts do not
come into contact with the tooth surface.
17-05-2021 147
Ref:Jan Lindhe – Text Book Of Clinical Periodontology (4th edition)

148. • New fibroblasts are derived from the proliferation of
undifferentiated perivascular cells.
• The collagen matrix of gingival connective tissue is well
organized into fiber bundles, which constitute the
gingival supra-alveolar fiber apparatus. It is made up of
the transseptal, circular, semicircular, transgingival, and
intergingival fibers, which connect and link the adjacent
teeth of one arch.
17-05-2021 148

149. Cuticular structures on the Tooth:
• Listgarten has classified cuticular structures into coatings of
developmental origin & acquired coatings.
• Acquired coatings include those of exogenous origin such as
saliva, bacteria, calculus & surface stains.
• Coating of developmental origin are those that are normally
formed as tooth development. They include the REE, the
coronal cementum & the dental cuticle.
17-05-2021 149

150. Developmental disturbances of gingiva
It includes
• Fibromatosis gingivae
• Retrocuspid papilla
17-05-2021 150

151. Fibromatosis gingivae
• Diffuse fibrous overgrowth of the
gingival tissue
• Mostly hereditary-AD
• Most common in maxilla
• Familial also occur with
Hypertrichosis, epilepsy, mental
retardation, sensori-neural deafness,
hyperthyroidism and growth hormone
deficiency
17-05-2021 151

152. • Histopathology
• Dense hypocellular and hypovascular
collagenous tissue
• Epithelial thickening with elongated rete
ridges
• Mild inflammatory infiltrate
• Sometimes dystrophic calcifications seen
• EM reveals mixture of fibroblasts and
myofibroblast likecells
17-05-2021 152

153. Treatment
• Gingivectomy and oral hygiene measures
• Follow up required because of itstendency to
recur
• Severe cases ±selective extraction
andgingivectomy
17-05-2021 153

154. Retrocuspid papilla
• Described by Hirshfeld in 1933
• Small elevated nodule located on the lingual mucosa of the
mandibular cuspids
•C/F
• Soft, well circumscribed mucosal nodule
• Most common in children between 8 ±16 yrs
• Show regression with maturity
• More common in females than males
17-05-2021 154

155. Retrocuspid papilla
17-05-2021 155

156. •Histopathology
• Mild hyperorthokeratosis or hyperparakeratosis,with or without acanthosis
• Connective tissues sometimes highly vascularised and show large stellate
fibroblasts
• Occasionally epithelial rests also seen
•Treatment
• Regress with age no treatment necessary
17-05-2021 156

157. Conclusion:
• Since the development of tooth &
periodontium forms the base of dentistry a
thorough understanding and sound
knowledge is necessary for a dentist to
provide an appropriate treatment.
17-05-2021 157

158. 17-05-2021 158
Summary of tooth formation

159. REFERENCES:
• Ten Cate's Oral Histology Development, Structure, and Function 9TH EDITION
• Clinical Periodontology- Carranza’s 13th edition
• Jan Lindhe – Text Book Of Clinical Periodontology (4th edition)
• Orban’s Oral Histology & Embryology 13th edition
• Periodontology 2000, Vol. 24, 2000, 9–27
• Cementoenamel junction: An insightKharidi review ;Laxman Vandana,
Ryana Kour Haneet;Journal of Indian Society of Periodontology - Vol 18,
Issue 5, Sep-Oct 2014
• Swaminathan Y, Thomas J; What makes cementum a unique structure?
International Journal of Scientific & Engineering Research, Volume 4,
Issue 12, December-2013 2268:ISSN 2229-5518
• Grzesik WJ, Narayanan AS. Cementum and periodontal wound healing
and regeneration. Crit Rev Oral Biol Med. 2002;13(6):474-84
17-05-2021 159

160. 17-05-2021 160