development of periodontium

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DEVELOPMENT
OF
PERIODONTIUM

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DEVELOPMENT OF GINGIVAL TISSUES
• Gingival tissues are composed of a
Superficial epithelium An underlying
of ectodermal origin connective tissue
of mesodermal
origin
• Both these tissues have components which derive
from both the oral mucosa & the developing tooth
germ.
- Listgarten 1972,Mc Kenzie 1988

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• The epithelium of gingival tissues is composed of:
- non keratinized junctional epithelium
- non keratinized sulcular epithelium
- keratinized oral epithelium

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• Gingival connective tissue is largely a fibrous connective
tissue that has elements originating from the oral mucosa
connective tissue & dentogingival fibers originate from
developing dental follicle.
• The gingival tissues associate with tooth via separate
mechanisms.
• The epithelial tissues interface with the tooth
via an epithelial attachment known
as Junctional Epithelium which in
health, is usually located at,
or coronal to the CEJ.

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• The gingival tissues attach to the root surface at
or below the CEJ via fiber insertion into the
cementum.

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• It follows a well defined series of events.
• Prior to eruption of the tooth, Enamel of formed crown is
covered with a few layers of flattened cuboidal cells called
Reduced Enamel Epithelium (REE).
• The basal lamina (EAL) lies in
direct contact with Enamel.
• REE completely encapsulates the
newly formed crown & terminates
at CEJ.
Development of Junctional Epithelium

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• As tooth erupts ,the REE covering the tip of the
crown fuses with the oral epithelium.
• The migrating epithelium produces an epithelial mass
between the oral epithelium & REE so that the tooth
can erupt without bleeding.
• Former ameloblasts do
not divide.

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• Shortly, afterwards it degenerates to result in first
exposure of the crown to the oral cavity.
• First evidence of Junctional Epithelium is seen upon
crown exposure.
• As the tooth continues to
erupt, the conversion of REE into
to Junctional Epithelium
continues.

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• Once, Enamel formation is complete, reduced
ameloblasts attach via hemidesmosomes to a basal
lamina that covers the crown surface referred to as
internal basal lamina of REE.
• This basal lamina extends apically
to CEJ where it loops back to form
an interface between REE &
connective tissue of the mucosa that
surrounds the entire crown.

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Development of Gingival Sulcus
• The gingival sulcus is a shallow, V-shaped space
or groove between the tooth and gingiva.
• It begins to form as the tooth erupts & a
separation occurs between the attached
epithelium & tooth surface.
• Simultaneously, epithelial cells derived from
stratum intermedium also begin to transform into
cells with the appearance of Junctional
Epithelium.

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• Cells from stratum intermedium continue their mitotic
activity.
• Newly formed daughter cells migrate coronally
toward the base of the gingival sulcus
exfoliate
allowing JE to maintain its
structure via constant
renewal process.

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• Gingival sulcus is formed when the tooth erupts into
the oral cavity.
• At that time , JE and REE form a broad band
attached to tooth surface from near the tip of the
crown to the CEJ.
• Gingival sulcus is a shallow V- shaped groove
between the tooth & gingiva that encircles the newly
erupted tip of the crown.
• In newly erupted tooth only Junctional epithelium
persists.

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• Sulcus consists of a shallow space that is
coronal to the attachment of the Junctional
epithelium and bounded by tooth
on one side and sulcular
epithelium on the other.
• The coronal extent of gingival
sulcus is the gingival margin.

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• Junctional epithelium has a free surface at the
bottom of the gingival sulcus.
• Like oral sulcular epithelium and oral
epithelium, Junctional
epithelium is continuously
renewed through cell division
at the basal layer.
• The cells migrate to base
of gingival sulcus where they
are shed.

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DEVELOPMENT OF CEMENTUM

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DEVELOPMENT OF CEMENTUM
• It is a hard, avascular connective tissue that
covers the anatomic roots of the human teeth.
• It was first described microscopically in 1835 by
two pupils of purkinje.
• It begins at the cervical portion of
the tooth at the CEJ and continues
to the apex.

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DEVELOPMENT OF CEMENTUM
• Formation can be divided into
Prefunctional stage
Functional stage

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Prefunctional stage :
• Cementum is formed during the root
development
• Human roots form over an extended period of
time ranging between 3.75 – 7.75 yrs for the
permanent tooth.
• Hence, Prefunctional development of Cementum
is a long lasting procedure.

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Functional stage :
• Commences when tooth reaches the
occlusal level & continues throughout life.

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• Adaptive & reparative processes are carried out
by the biological responsiveness of Cementum
influences the alterations in the distribution &
appearance of Cementum varieties on the root
surface with time.

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CEMENTOGENESIS
• After completion of crown
formation the cells of the
inner and outer enamel
epithelium form the bilayer of
cells known as Hertwig’s
Epithelial Root Sheath.

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• Continuous cell mitotic activity at the apical
termination of HERS
coronoapical growth of this bilayer

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• Its most apical portion, which forms a
diaphragm separates the dental papilla from the
dental follicle.
• The inner & outer cell layer of HERS is
surrounded by basement membrane.

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• The epithelial mesenchymal interactions
occurring between the internal basement
membrane & the cells of peripheral dental
papilla
differentiate into odontoblasts.
• Once the first matrix of radicular dentin is
formed by the maturing odontoblats & before it
mineralizes, HERS becomes discontinuous.

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• Epithelial remnants of HERS persist in the
developing & aging PDL, at an approximate
distance of 30 – 60 µm far from the root surface,
where they are referred to as Epithelial Rests of
Malassez.
- Malassez M L 1884

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• ERM forms a continuous network ensheathing the
root at a certain distance.
• Cell clusters are surrounded
by a basement
membrane which
separates them from
the surrounding
connective tissues.
• Function presently
unknown.

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DEVELOPMENT OF DENTINO CEMENTAL JUNCTION
• Differentiation of cementoblasts occurs on mantle dentin.
Maturing cementoblasts extend cytoplasmic process
positioning of the cemental collagen fibers
interdigitation of two fibril population (Cementum & dentin)
calcification starts in dentin, spreads across Cementum
formation of DCJ

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DEVELOPMENT OF DENTINO CEMENTAL JUNCTION

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DEVELOPMENT OF CEMENTO ENAMEL JUNCTION
• In 60% of teeth – Cementum overlaps the
cervical end of enamel for
a short distance.
• Occurs when enamel
epithelium degenerates at
its cervical termination
permitting connective tissue
to come in direct contact
with the enamel surface.

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DEVELOPMENT OF CEMENTO ENAMEL JUNCTION
• In 30% of teeth – Cementum
meets cervical end of enamel
in a relatively sharp line.

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DEVELOPMENT OF CEMENTO ENAMEL JUNCTION
• In 10% - Enamel & Cementum do not meet.
• Occurs when enamel
epithelium in the cervical
portion of the root is delayed
in its separation from dentin.
• In such cases no CEJ
• Zone of the root is devoid of
Cementum & is, for time
covered by REE.

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DEVELOPMENT OF INTERMEDIATE CEMENTUM
• Just before the degeneration of the epithelial root
sheath, root dentin is deposited adjacent to it as a
thin, amorphous, structureless, highly mineralized
secretion which appears on the surface of root
dentin.
• Devoid of collagen but
contains tryptophan.
• More evident in apical
region.
• Thickness : 10 – 20 µm

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DEVELOPMENT OF INTERMEDIATE CEMENTUM
• This Cementum is deposited on the root surface
& functions to attach secondary Cementum to its
surface.
• May contain epithelial cells.
• Root sheath cells have an
odontoblast stimulating
ability as well as possible
secretory functions in
producing the Intermediate
Cementum.

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CELLUAR AND ACELLULAR CEMENTUM
• The behavior of cementoblasts during matrix
formation determines the type of Cementum to be
formed.
• Cellular Cementum –
found on apical half (thicker)
• Acellular Cementum –
covers the cervical half of the
root dentin (thin)

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CELLULAR CEMENTUM ACELLULAR CEMENTUM

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DEVELOPMENT OF ALVEOLAR PROCESS
• Alveolar bone develops as the tooth develops.
• Initially, this bone forms a
thin egg shell of support,
termed as the ‘tooth crypt’,
around each tooth germ.

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• As the root grows and lengthen
alveolar bone keeps pace with the
elongating and erupting
tooth and maintains a
relation with each tooth
root.

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• Development of alveolar process begins in 8th
week in utero.
• At that time, within maxilla & mandible the
forming alveolar bone develops a horse shoe
shaped groove.
• The bony groove or canal is formed by the growth
of facial & lingual plates of body of maxilla or
mandible & contains the
developing tooth germs
together with alveolar blood
vessels and nerves.

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• At first developing tooth germs lie free in the
groove.
• Then, bony septa develops between teeth and
eventually each tooth is contained in a separate
crypt.
• During uterine life, dental
alveolus like the rest of the
skeleton is formed from an
embryonic type of bone
composed of tiny, bony
spicules.

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• Embryonic bone is of 2 types :
Woven Bone Coarse Bundle Bone
bundles of collagen collagen bundles
run in various direction are thicker.
in the matrix
Follow a parallel
coarse in matrix.

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• The matrix of embryonic bone consists of more
glycosaminoglycans & glycoproteins than that of
mature bone.
• The embryonic bone, is of temporary existence
and is replaced by mature or lamellar bone of the
compact or spongy bone.

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MATURE BONE :
• Composed of lamellae arranged in an orderly
manner.
• Fine fiber arrangement.
• Few cells

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• The bone between the roots of the adjacent
single rooted or multirooted teeth is termed as
the interdental bone.

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• In its mature form, alveolar bone is composed
of two parts :
Alveolar Bone Proper
Supporting Bone

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ALVEOLAR BONE PROPER :
• It is a thin lamella of compact bone that lines
the root socket & periodontal fibers are
embedded in it.
• Also called as Lamina Dura.

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• Alveolar bone proper is a specialized type of
dense bone composed of bundle bone &
haversian bone that appears radio opaque on x-
ray and hence is called as Lamina Dura.
• Bundle bone is named as
it is penetrated by
bundles of periodontal
fibers.
ALVEOLAR BONE PROPER :

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SUPPORTING BONE :
• Consists of both spongy &
compact bone
• Functions in supporting the
alveolar bone proper.

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• It is formed by osteogenic cells in the outermost
layer of the dental follicle
differentiate into osteoblasts
bone matrix laid down
osteocytes formed
Matrix calcifies
formation of mature bone
DEVELOPMENT OF ALVEOLAR BONE PROPER

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• In all bony tissues a system of cell to cell
communication exists between adjacent bone cells
e.g. osteogenic cells, osteoblasts & osteocytes.
• This takes place by 3 means :
1)Presence of junctional complex (gap) between the
different cells.
2)Presence of cytoskeleton at opposing points of
adjacent cells
3)Presence of small nerve fibers in the periosteum
These may work together to produce effective cell
communication & co-ordination of cellular activity.

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• Relationship between
a deciduous tooth & its
accompanying
succedaneous tooth
detailing the formation
of the alveolar bone
- Scoh,Symonds 1974
AT BIRTH AT 7MONTHS
AT 2½ YRS 7 YRS

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DEVELOPMENT OF PERIODONTAL LIGAMENT
• The periodontal ligament originates from the
dental follicle.
• It is a specialized, soft, connective tissue ligament
that provides the attachment for the teeth to the
adjacent alveolar bone.
• Its fibers are embedded in the
Cementum on the tooth’s
surface & in the alveolar bone
at the other end.

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DEVELOPMENT OF PERIODONTAL LIGAMENT
• Delicate fiber bundles of the forming PDL fibers
first appear as root formation begins.
• Follicular cells show increased mitotic activity.
• Inner most cells near the forming root
differentiate into cementoblasts & lay down
cementum.
• Outer most cells
osteoblasts

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• Centrally located cells in the ligament
differentiate into fibroblasts.
• These produce collagen
fibers that becomes
embedded into both
cementum and bone.
DEVELOPMENT OF PERIODONTAL LIGAMENT

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DEVELOPMENT OF PERIODONTAL LIGAMENT
• At first, developing fibers of PDL run obliquely in
a coronal direction from tooth to bone.
• The apical fibroblasts are the
stem cells that proliferate &
migrate cervically to form the
first group of collagen fibers.
ACF

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DEVELOPMENT OF PERIODONTAL LIGAMENT
• As tooth eruption proceeds, the obliquity of
the fibers gradually decreases.
ACF
OF

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DEVELOPMENT OF PERIODONTAL LIGAMENT
• The position of CEJ which was apical to the crest
becomes level & then coronal to the alveolar crest.
• This change between CEJ & alveolar crest may
relate to their functional role during tooth
eruption.
• It also brings the final
arrangement of the
principal fiber groups
of the mature PDL.

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DEVELOPMENT OF PRINCIPAL FIBERS
A) First small brush like fibrils arise from root
cementum & projects into the PDL space.
- surface of bone at this stage is covered by
osteoblasts.
- from the surface of bone only a small number of
radiating thin collagen fibrils can be seen.

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DEVELOPMENT OF PRINCIPAL FIBERS
B) Number & thickness of fibers entering the
bone increases & radiates towards the
loose connective tissue in the mid portion
of the PDL area which contains more or
less randomly oriented collagen fibrils.
- Fibers from cementum are still short while that
of bone becomes longer.
- The terminal portions of these fibers carry
finger like projections.

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DEVELOPMENT OF PRINCIPAL FIBERS
C) Fibers originating from cementum increase in
length & thickness & fuse in the PDL space with
the fibers arising from alveolar bone.
- When the tooth following eruption reaches
contact in occlusion & starts to function the
periodontal fibers become organized in bundles
& run continuously from bone to cementum.

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• Periodontal fibers run continuously from
cementum to alveolar bone proper.
• Periodontal fibers embedded in cementum have
a smaller diameter but are more numerous in
number than those embedded in alveolar bone
proper.

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• Periodontal ligament is in a continuous state of
remodelling, both during development &
throughout life span of the tooth.
• The ligament persistently maintains support of
an erupting or functioning tooth.

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• Remodelling is achieved by fibroblasts that
rapidly synthesize & secrete collagen.
• Rapid turnover of collagen takes place
throughout the whole thickness of ligament from
bone to cementum.
• Turnover is not restricted to the metabolically
active middle zone, which is sometimes referred
to as intermediate plexus.
• Different rate of collagen turn over in the
ligament in an apico-cervical direction.

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• Highest turn over is in apical region
• Lowest in cervical region of the ligament.

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REFERENCES
• Tencate’s Oral histology – Antonio Nanci
• Orban’s Oral histology and embryology –
S. N. Bhaskar
• Biology of periodontal tissues –
Bartold and Sampathnarayan
• Clinical periodontology and implant dentistry –
Lindhe
• Oral development and histology – Avery
• Clinical Periodonology – Carranza 10th edition
• Biological structure of normal & diseased
periodontium – Perio 2000, vol 13, 1997