1. Development of the
Periodontium
Development Of The Periodontium

2.  Periodontium is defined as those tissues
supporting & investing the tooth. (Tencate 5th edi.)
 It consists of :-
1. Cementum (derived from the latin word
caementum, quarried stone i.e. chips of stone used
in making mortar)
Development Of The Periodontium

3. 2. Periodontal ligament (PDL)
3. Bone lining the alveolus (socket)
4. That part of the Gingiva facing the tooth
Development Of The Periodontium

4. Development Of The Periodontium

5. Development Of The Periodontium

6. GOMPHOSIS
(Socketed Tooth)
 Relatively recent structure in evolutionary terms
 Almost exclusively mammalian
Development Of The Periodontium

7. PERIODONTIUM
 Tissues of tooth support are odontogenic
 Derived from dental follicle
 Recent evidence indicating progenitor cells may be
derived from cells of dental papilla that migrate into
follicle at bell stage of development
Development Of The Periodontium

8. DENTAL FOLLICLE
 Well defined layer of cells surrounding the tooth
germ that is continuous with & derived from the
dental papilla at the cervical loop.
 Dental follicle forms cementum, Periodontal
ligament & bone
Development Of The Periodontium

9. Functions of Dental
Follicle
 To protect and stabilise the tooth during formation and
later eruption.
 To provide nutrition and nerve supply to the developing
tooth.
 To give rise to cells that form the cementum, the
periodontal ligament & the inner wall of the bony crypt
or alveolus.
Development Of The Periodontium

10. Development Of The Periodontium

11. Crypt

A crypt is a bony cavity enclosing a developing tooth
and is formed by the dental follicle.
 Each crypt has an opening in its roof through which
dental follicle fibres extend for communication within the
oral mucosa.
 The fibrous extension of the dental follicle, which
connects the permanent tooth germ to the oral mucosa is
called gubernacular cord .
Development Of The Periodontium

12. Dental Cementum
The dynamic tissue
covering the
root Development Of The Periodontium

13. Hyaline Layer of Hopewell
Smith / Intermediate
Cementum
It is a structure less highly mineralized layer
some 10 um thick on the surface of the root
dentin. Some investigators believe it may be a
form of enamel.
Development Of The Periodontium

14. Hyaline Layer (HL)
 Many fish have teeth covered with enameloid ( a
tissue that resembles enamel but is partly formed
by the dental papilla & internal dental epithelium)
 Enameloid & the hyaline layer are strikingly
similar.
 It has been suggested that the function of HL is
to cement cementum to dentin.
Development Of The Periodontium

15. CEMENTOGENESIS
 Cementum is deposited on the surface of root dentin
 Hertwig’s epithelial root sheath initates the
differentiation of root odontoblasts from the dental
papilla, which then form dentin of the root.
Development Of The Periodontium

16.  Before primary cementum can form, root
sheath must fragment to allow follicular
cells to reach the newly formed root
surface.
 These follicular cells differentiate into
cementoblasts.
Development Of The Periodontium

17.  Generally assumed that epithelium/ epithelial
product must be involved in initiating the
differentiation of cementoblasts from the
dental follicle.
 Eg:- When follicular tissue comes into
contact with enamel, cementum is deposited
on the enamel surface.
Development Of The Periodontium

18.  Finally the epithelial derived product
(enamel like proteins) incorporated into the
hyaline layer may play a role in the
differentiation of cementoblasts.
Development Of The Periodontium

19. Development Of The Periodontium

20.  Cementoblasts insert cytoplasmic processes
into unmineralised hyaline layer, begin to
deposit collagen fibrils at right angles to the
root surface.
 Cementoblasts then migrate away from the
hyaline layer but continue to deposit collagen
forming the fibrous matrix of acellular
cementum.
Development Of The Periodontium

21.  Cementoblasts also secrete noncollagenous
proteins such as bone sialoprotein and
osteocalcin.
Development Of The Periodontium

22. ACELLULAR CEMENTUM
 This first formed cementum is acellular because the
cells retreat into the ligament.
 It covers at least coronal two thirds of the root.
 This cementum thus consists of a mineralized layer
with a fibrous fringe extruding from it.
Development Of The Periodontium

23. Development Of The Periodontium

24.  Once the tooth is in occlusion, a more rapidly formed
& less mineralized form is deposited around the
apical third of root.
 The organic matrix consisting of noncollagenous
proteins & collagen fibrils become mineralized as a
result of cementoblasts budding off matrix vesicles.
Development Of The Periodontium

25. Cellular Cementum
 At the same time, the cementoblasts get trapped in the
matrix occupy lacunae & they become cementocytes.
Thus this is called cellular cementum.
 This cementum is confined to the apical third of the
root & the interradicular regions of premolars &
molars.
Development Of The Periodontium

26. Development Of The Periodontium

27. FATE OF HERTWIG’S ROOT
SHEATH
 As the sheath fragments & follicular cells migrate through
it, however most of the cells persist as strands or clusters
called as epithelial cell rests of malassez
 These cells rests are remnants of the root sheath & are
seemingly discrete clusters or islands of epithelial cells.
Development Of The Periodontium

28. Development Of The Periodontium

29. Cell Rests of
Malassez
 They exhibit dark staining nuclei & little cytoplasm
& are inactive.

At present there is no function for these cells,
however it has been suggested that they have a
protective function, preventing resorption of the root
surface to a role in maintaining the width of
periodontal ligament.
Development Of The Periodontium

30. Development Of The Periodontium

31.  Alveolar Bone and the
Alveolar Process
( The socket that is never
stable)
Development Of The Periodontium

32. Development Of The Periodontium

33. ALVEOLAR BONE
FORMATION
 As the root & its covering of primary cementum form, new
bone is deposited against the crypt wall.
 The deposition of this bone gradually reduces the space
between the crypt wall & tooth to the dimensions of
periodontal ligament.
 As mentioned new bone is formed by osteoblasts originating
from the dental follicle.
Development Of The Periodontium

34.  Development of the alveolar process begins
in the 8th week in utero.
 At that time, within the maxilla &
mandible the forming alveolar bone
develops a horse shoe shaped groove that
opens towards the oral cavity.
Development Of The Periodontium

35.  The bony groove or canal is formed by
growth of facial & lingual plates of the
body of maxilla & mandible & contains the
developing tooth germs together with the
alveolar vessels and nerves.
 Initially the developing tooth germs lie in
a groove.
Development Of The Periodontium

36.  Gradually bony septa develop between
teeth, so that each tooth is eventually
contained in a separate crypt.
 The alveolar process develops during the
eruption of the teeth.
Development Of The Periodontium

37.  During uterine life, the dental alveolus like
the rest of skeleton is formed by an
embryonic type of bone composed of bony
spicules.
 This embryonic bone - a variety of coarse
fibered or woven bone, is gradually
replaced by compact & spongy bone.
Development Of The Periodontium

38.  Both compact & spongy bones initially are
composed of layers (lamellae) arranged in
an orderly manner.
 The alveolar bone proper is formed by the
outermost cells of the dental follicle which
differentiate into osteoblasts.
Development Of The Periodontium

39. Development Of The Periodontium

40.  They lay down the bony matrix or osteoid
in which some osteoblasts become
embedded as osteocytes .
 The matrix then calcifies to form bone.
Development Of The Periodontium

41. Development Of The Periodontium

42. Development Of The Periodontium

43. Periodontal Ligament
Formation
 The Periodontal ligament forms shortly after root
formation begins.
 At the commencement of ligament formation the
ligament space consists of unorganized connective
tissue with short fibre bundles extending into it from
both cemental & bony surfaces.
Development Of The Periodontium

44.  Next ligament fibroblasts begin to form collagen
which remodels to the collagen bundles & establish
continuity across the ligament space.
 Thereby it secures the attachment of tooth
(cementum) to bone.
Development Of The Periodontium

45.  Before the tooth erupts the crest of alveolar bone is
above the CEJ & the developing fibre bundles of the
PDL are all directed obliquely.
 As the tooth moves coronally during eruption the
alveolar crest comes to coincide with the CEJ & the
oblique fibre bundles become horizontally aligned.
Development Of The Periodontium

46.  When the tooth finally comes into function, alveolar
crest is below the CEJ, thus the horizontal fibres
termed as alveolar crest fibres become
oblique once more.
 Only after the teeth come into function do the fibre
bundles of PDL thicken appreciably.
Development Of The Periodontium

47.  The ligament fibre bundles are established &
reoriented by the remodelling capacity of ligament
fibroblasts.

The PDL achieves the highest rate of collagen
remodelling & tissue turnover so far demonstrated.
Development Of The Periodontium

48. The Gingival Tissues
The architecture of
Periodontal
Protection
Development Of The Periodontium

49. Development Of The Periodontium

50. Dento gingival Junction
Formation
 That part of the Gingiva facing the tooth is a part of
periodontium & it is an adaptation of the oral mucosa.
 At the time of eruption the crown of the tooth is
covered by a double layer of epithelial cells.
Development Of The Periodontium

51.  Those cells in contact with the enamel are ameloblasts, which
develop hemidesmosomes secrete a basal lamina & become
firmly attached to the enamel surface.
 The outer layer consists of more flattened cells the remnants of
all the remaining layers of dental organ.

Together these 2 layers are called as reduced dental
epithelium.
Development Of The Periodontium

52.  Between the reduced enamel epithelium &the overlying oral
epithelium is connective tissue which breaks down when the
tooth is erupting.
 In response to degenerative changes in the connective tissues,
the cells of the outer layer of the reduced dental epithelium &
basal cells of the oral epithelium proliferate & migrate into the
CT, eventually fusing to form a mass of epithelial cells over
the erupting tooth (epithelial cuff ).
Development Of The Periodontium

53.  Thus the cells of the cuff are proliferative, migratory &
separated by widened intercellular spaces.
 Through these spaces, antigens enter from the oral cavity
leading to an acute inflammatory response within the
connective tissue.
 The clinical manifestation of this inflammatory response is
called Teething.
Development Of The Periodontium

54.  Once the cusp tip of erupting tooth emerges into the oral
cavity, oral epithelial cells begin to migrate partially over the
reduced enamel epithelium in an apical direction.
 At this time, the attachment of gingival epithelium to tooth is
maintained by ameloblasts & their hemidesmosomes & basal
lamina adjacent to the enamel surface. This is called
Primary Epithelial Attachment.
Development Of The Periodontium

55.  A process of transformation takes place whereby the reduced
enamel epithelium gradually becomes junctional
epithelium.
 The reduced ameloblasts which have lost their ability to divide
get transformed into squamous epithelial cells.
Development Of The Periodontium

56.  As the overgrowing epithelial cells from the cuff stratify, they
further separate the cells of the transformed dental epithelium
from the nutritive supply, with the latter cells degenerating &
creating a Gingival Sulcus .
 The final conversion of reduced dental epithelium to
junctional epithelium may not occur until 3 to 4 years after the
tooth has erupted.
Development Of The Periodontium

57.  Immediately after all the reduced dental epithelium has been
transformed, the development of dentogingival junction may
be regarded as complete.
 With the formation of the dentogingival junction, the dental
epithelium is finally lost.
Development Of The Periodontium

58. THANK YOU
Development Of The Periodontium