Periodontics

1. DEVELOPMENT OF
PERIODONTIUM
BY
DR. JIGNESH TATE
1st YEAR PG STUDENT
DEPARTMENT OF PERIODONTOLOGY
YOGITA DENTAL COLLEGE AND HOSPITAL, KHED

2. CONTENT
 Introduction
 Dental lamina
 Stages of tooth development
 Hertwig’s epithelial root sheath and root formation
 Development of cementum
 Development of periodontal ligament
 Principle Fibers of periodontal ligament
 Development of principle Fibers
 Alveolar bone
 Gingiva
 References

3. INTRODUCTION
 Periodontium consists of investing and supporting tissues of the
tooth which include gingiva, periodontal ligament, cementum and
alveolar bone.
 It can be divided into two parts: the gingiva whose main function is
protection of underlying tissues and attachment apparatus composed
of the periodontal ligament, cementum and alveolar bone.
 The word comes from the Greek terms peri- meaning “around” and
odontos meaning “tooth”.
 Derived from the dental follicle of the tooth germ.

4. DENTAL LAMINA
 2 or 3 weeks after the rupture of buccopharyngeal membrane, when
the embryo is about 6 weeks old, certain areas of basal cells of the
oral ectoderm proliferate more rapidly than do the cells of the
adjacent areas. This leads to the formation of primary epithelial
band.
 At about 7th week the primary epithelial band divides into the
inner(lingual) process called dental lamina and outer (buccal)
process called vestibular lamina.

5. STAGES OF TOOTH DEVELOPMENT

6. BUD STAGE
 Simultaneously with the differentiation of each dental lamina,
round or ovoid swellings arise from the basement membrane at 10
different points, corresponding to the future positions of the
deciduous teeth.
 These are the primordia of the enamel organ, the tooth buds.

7.  Peripherally located low
columnar cells and centrally
located polygonal cells.
 Many cells of the tooth bud
and surrounding
ectomesenchyme undergo
mitosis.
 As a result of increased
mitotic activity, the
ectomesenchyme
surrounding the tooth bud
condense.

8.  Ectomesenchymal
condensation
immediately
subjacent to the
enamel organ is
the dental papilla.
 The condensed
ectomesenchyme
that surrounds the
tooth bud and the
dental papilla is
the dental sac.

9. CAP STAGE
 As the tooth bud
continues to
proliferate, it does
not expand uniformly
into a larger sphere.
Instead unequal
growth in different
parts of the tooth bud
leads to the cap stage.

10. 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 epithelium.
- The cells in the concavity
of the cap become tall
columnar and represent
the inner enamel
epithelium.

11. Stellate reticulum
- Polygonal cells.
- Separation of polygonal cells
due to osmotic pressure
exerted by dental papilla.
- As a result, the polygonal
cells become star shaped but
maintain contact with each
other by their cytoplasmic
processes.
- As these star shaped cells
form a cellular network, they
are called the stellate
reticulum.

12. BELL STAGE
 As the invagination of
the epithelium
deepens and its
margins continue to
grow, the enamel
organ assumes a bell
shape.
 Four different types of
epithelial cells are
distinguished on light
microscopic
examination of bell
stage of the enamel
organ.

13. The cells form:
• the inner enamel epithelium,
• the stratum intermedium,
• the stellate reticulum and
• the outer enamel epithelium.

14. Inner enamel epithlium
- The inner enamel epithelium - tall columnar cells - amelogenesis -
ameloblasts.
- The cells of the inner enamel epithelium exert an organizing
influence on the underlying mesenchymal cells in the dental
papilla, which later differentiate into odontoblasts.

15.  Stratum intermedium
- A few layers of squamous cells form the stratum intermedium
between the inner enamel epithelium and the stellate reticulum.
- 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.

16. Stellate reticulum
- Expands due to increase in the amount of intercellular fluid.
- Cells are star shaped with long processes that anastomose with those of
adjacent cells.
- Before enamel formation begins, the stellate reticulum collapses, reducing
the distance between the centrally located ameloblasts and the nutrient
capillaries near the outer enamel epithelium.
- Its cells are then hardly distinguishable from the stratum intermedium.

17.  Outer enamel epithelium
- The cells of the outer enamel epithelium flatten to a
low cuboidal form.
- At the end of the bell stage, preparatory to and during
the formation of the enamel, the formerly smooth
surface of the outer enamel epithelium is laid in folds.
- Between the folds the adjacent mesenchyme of the
dental sac forms papillae that contain capillary loops
and thus provide a rich nutritional supply for the
intense metabolic activity of the enamel organ.

18. Dental lamina
- The dental lamina is seen to extend lingually and is termed successional
dental lamina as it gives rise to enamel organs of permanent successors
of deciduous teeth.

20. HERTWIG’S EPITHELIAL ROOT SHEATH
AND ROOT FORMATION
 The development of roots begins after enamel and dentin
formation has reached the future cementoenamel junction.
 The enamel organ plays an important part in root development by
forming hertwig’s epithelial root sheath, which moulds the shape
of the roots and initiates radicular dentin formation.
 Hertwig’s root sheath consists of the outer and inner enamel
epithelium.

22.  When these cells have induced the differentiation of radicular dental
papilla cells into odontoblasts and the first layer of dentin has been
laid down, the epithelial root sheath looses its structural continuity
and its close relation to the surface of the root.
 Its remnants persists as epithelial network near the external surface
of the root.
 These remnants are found in the periodontal ligament of the erupted
teeth and are called rests of malassez.

23. FIG: HERTWIG’S EPITHELIAL ROOT SHEATH

24. Epithelial Daiphragm

25. Root Cementum
Specialized mineralized tissue covering the root surfaces
and occasionally small portion of the crowns of teeth.
Collagen fibrils embedded in an organic matrix.
Serves by attaching the principle periodontal ligament
fibers to the tooth root.

26. Cementogenesis
Soon after Hertwig’s Epithelial Root Sheath breaks up,
undifferentiated mesenchymal cells from the adjacent
connective tissue differentiate into cementoblasts.
Cementoblasts synthesize collagen and protein
polysaccharides, which make up the organic matrix of the
cementum.

27. The cementoblasts that are derived from the dental follicle
are involved in the formation of Cellular intrinsic fiber
cementum.
The cementoblasts that are derived from Hertwig’s
Epithelial Root Sheath, are involved in the formation of
Acellular extrinsic fiber cementum.

28. Cementoid Tissue
Growth of cementum is a rhythmic process. As the new
layer of cementum is formed, the old one calcifies.
A thin layer of cementoid can be seen on the cemental
surface. This cementoid tissue is lined by cementoblasts.
Connective tissue fibers of the periodontal ligament pass
between the cementoblasts into the cementum.

30. Schroeder’s Classification of cementum.
(Based on nature and origin of organic fibrous matrix)
1. Acellular Afibrillar cementum
 Neither contains cells nor intrinsic or extrinsic collagen fibers.
 Found near cervical region of crown.
2. Acellular extrinsic fiber cementum
 Composed of densely packed bundles of sharpey’s fibers that are derived from
periodontal ligament.
 Found in cervical and middle third of root.
 Does not contain any type of cells.
 The only type found in single rooted teeth.

31. 3. Mixed stratified cementum
 Contains alternating layer of cellular and acellular cementum.
 Found in apical portion of root.
4. Cellular intrinsic cementum
 Also known as secondary cementum.
 Found on middle and apical third of root.
 Entirely derived from cementoblasts, hence devoid of Sharpey’s fibers.

32. DEVELOPMENT OF PERIODONTAL
LIGAMENT
 Shortly after the beginning of root formation and the formation of
outer dentinal layer of root, the periodontal ligament is formed.
 The external and internal dental epithelia proliferate from the
cervical loop of dental organ to form double layered hertwig’s
epithelial root sheath.

33.  Due to growth changes, the sheath stretches and it fragments to form
discrete clusters of epithelial cells called epithelial cells of Malassez.
 The enamel organ and Hertwig’s Epithelial Root Sheath are
surrounded by a dental sac.
 A thin layer of these cells which lies adjacent to the enamel organ is
known as dental follicle.

34.  The dental follicle area comprises of two sub-population of cells.
 These cells initially are smaller in size and have less synthetic
activity.
THE DENTAL FOLLICLE AREA
- CLOSE TO EPITHELIAL ROOT SHEATH
- PERI FOLLICULAR MESENCHYMAL CELLS
- CLOSE TO THE BONE
- DENTAL FOLLICLE PROPER CELLS

35. HERS undergoes disintegration
to form cell rests of Malassez
Root dentin is exposed
Cells of perifollicular mesenchyme get attracted to root dentin and
get differentiated to form cementoblasts, which lay down the
cementum.
As cementum is laid down the cells of perifollicular mesenchyme
gain polarity, increase in size and they increase their synthetic
activity and form collagen fibers

36. These fibers get embedded into the
cementum on one side and too the
newly formed bone on the other side
The periodontal space has numerous
unorganized collagen fibers
Small fiber bundles are seen extending
from the cementum side as well as the
bone side
As the cells develop and mature they
secrete collagen due to which these small
fiber bundles get interwind and form a link
between the bone and cementum, securing
the tooth in alveolar socket

37. PRINCIPLE FIBERS OF PERIODONTAL
LIGAMENT
 ALVEOLAR CREST FIBER GROUP
 HORRIZONTAL FIBER GROUP
 OBLIQUE FIBER GROUP
 APICAL FIBER GROUP

38. DEVELOPMENT OF PRINCIPLE FIBERS
 As the crown approaches the
oral mucosa during tooth
eruption the newly formed
collagen fibers lack orientation,
but soon acquire orientation
oblique to the tooth.
 The first collagen bundles
appear in the region
immediately apical to the
cemento enamel junction and
give rise to gingivo dental fiber
group.

39.  As tooth eruption progresses, additional oblique fibers appear and
become attached to the newly formed cementum and bone.
 The trans septal and alveolar crest fibers develop when the tooth
emerges into the oral cavity
 Alveolar bone deposition occurs simultaneously with periodontal
ligament organization

40.  As the tooth eruption proceeds, the obliquity of the fibers gradually
decreases and the position of cemento enamel junction, which is
originally apical to the crest of the crypt, comes to the level of the
crest and then coronal to the alveolar crest.
INITIAL AND FINAL POSITION OF
CEMENTO ENAMEL JUNCTION

41. Alveolar bone
 The maxilla and mandible of the adult human can be divided into
two portions:
The alveolar process; and
The basal body ( Basal Bone).

42. • The alveolar processes
consist of the thin alveolar
bone proper that forms the
alveolar wall of the tooth
socket, the inner and outer
cortical plates and spongy
bone between the alveolar
bone proper and cortical
plates.
• Since the alveolar
processes develop and
undergo remodeling with
the tooth formation and
eruption, they are tooth
dependent bony structures.

43. Development of alveolus
Tooth germs develop within bony structures.
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.

44. Even prior to root formation, the tooth germ within bony
compartment show continued bodily movement in various
directions to adjust to the growing jaws.
This movement causes minor remodeling of bony
compartment through bone resorption and deposition of
new bone.
The major changes in the alveolar processes begin to
occur with the development of the roots of teeth and tooth
eruption.

45. As the roots of the 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 periodontal ligament and
cementum respectively.
At the same time, some cells in the dental follicle also
differentiate into osteoblasts and form the alveolar bone
proper.

46.  The Alveolar process is constituted by the:
A.Bundle bone (Alveolar bone proper)
B.Spongy/ cancellous bone
C.Cortical plates

47. A. Bundle Bone
It is that portion of inner alveolar wall which gives
attachment to the periodontal ligament fibers and into
which Sharpey’s fibers are inserted.
Characterized by thin bone lamellae which are arranged
parallel to the root surface.
It derives its name from the abundance of collagen fiber
bundles (Sharpey’s fibers) into it.

49. Lamina Dura
The bundle bone is surrounded by dense lamellated bone,
and this dense bone along with bundle bone constitute the
lamina dura

50. B. Supporting Alveolar Bone
Spongy or Cancellous Bone
 Lies between cortical plates and alveolar bone proper.ie. Spongy
bone present between two compact layers of bone.
 Presence of cancellous bone trabeculae.
 Cancellous bone may not be present always at all areas of jaws, and
its amount also varies considerably at different areas of the alveolar
processes

51. 1. Alveolar bone proper
(Bundle bone)
2. Trabecular bone
(Supporting alveolar
bone)
3. Compact bone
(Cortical Plates)

52. C. Cortical Plates
 This is the external, compact covering of the alveolar process.
 Composed of dense, compact, haversian bone.
 Thicker in mandible than in maxilla, thickest in mandibular buccal
region.
 Histologically, cortical plates contain longitudinal lamellae and
haversian systems.

53. Gingiva
 The portion of oral mucosa that covers the alveolar processes of the
jaw and the cervical neck of the tooth.
 Comprises of gingival epithelium and connective tissue.
 The epithelial component of gingiva shows regional morphological
variations that are a reflection of tissue adaptation to the tooth and
alveolar bone.
 These include the oral gingival epithelium, oral sulcular epithelium
and junctional epithelium ,
 The gingiva evolves as the crown enters the oral cavity by breaking
through the oral epithelium.

54. Development of gingival epithelium
 The enamel epithelium rapidly proliferates, forming the thick
reduced enamel epithelium
 As the crown erupts further, the reduced enamel epithelium
overlying the enamel fuses with the oral epithelium, undergoes
transformation, and establishes the dento-gingival junction.
 The junctional epithelium maintains a direct attachment to the tooth
surface.

56. Primary Attachment Epithelium
Attachment of the junctional epithelium on the tooth
surface is called as the attachment epithelium.
During eruption, the tip of the tooth approaches the oral
mucosa resulting in the fusion of reduced enamel
epithelium and the oral epithelium.
The epithelium covering the tip of the crown degenerates
in the center, and the crown emerges through this
perforation into the oral cavity.

57. The reduced enamel
epithelium remains
attached to the part of the
tooth that has not yet
erupted.
Once the tip of the crown
has emerged, the reduced
enamel epithelium is
called primary attachment
epithelium.

58. With the eruption of the tooth,
the reduced enamel epithelium
moves apically, reducing in
length.
Eventually a shallow groove
develops, in between the
gingiva and the surface of the
tooth called the gingival
sulcus.

59. Apical Shift of Gingival Sulcus
(Passive Eruption)

60. References
 Moon Il Cho & Philias R. Garant. Development and general structure of the periodontium.
Periodontology 2000. 2000; 24: 9-27.
 Lindhe J. Anatomy of Periodontal Tisues. Sixth Edition. Wiley Blackwell Publication. 3-
48.
 Orban’s Oral Histology and Embryology. Development and Growth of Teeth. Twelfth
Edition. Elsevier Publication. 22-30.
 Orban’s Oral Histology and Embryology. Periodontal Ligament. Twelfth Edition. Elsevier
Publication. 156-7.
 Avery JK, Chiego DJ. Periodontium: Periodontal Ligament. Essentials of Oral Histology
and Embryology. Third Edition. Elsevier Publication. 146-50.
 Satish Chandra. Development of Teeth. Textbook of Dental and Oral Histology with
Embryology. Second Edition. Jaypee Publication. 32-42.
 Satish Chandra. Periodontal Ligament. Textbook of Dental and Oral Histology with
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