Periodontium / dental implant courses

Periodontium
(part 3)
INDIAN DENTAL
ACADEMY
Leader in continuing
Dental Education

• Periodontal ligament
-microscopic features
-functions
-age changes
- clinical consideration
• Alveolar bone
-Development
-structure
-functions
www.indiandentalacademy.com

• Collagen
• Elastic
• Reticular
• Secondary
• Indifferent fiber plexus
• Oxytalan
FIBERS
• Proteoglycans
• Glycoprotiens
• Blood vessels, nerves &
lymphatics
GROUND
SUBSTANCE

• Collagen is a protein composed of mainly glycine,proline,
hydroxyproline, and hydroxylysine.
• Collagen biosynthesis occurs inside fibroblast to form
tropocollagen.
• These aggregate into microfibrils that are packed
together to form fibrils
• Further forms bundles.

• Termed as “principal fibers”
• Mainly composed of collagen type I.
• Terminal portion of principal fibers are inserted into
cementum & bone – Sharpey’s fibers.

ALVEOLAR
CREST
HORIZONTAL
GROUP OBLIQUE
GROUP
TRANSSEPTAL
GROUP
APICAL
GROUP
INTERRADICULAR
GROUP

• Extends obliquely from cementum just beneath the junctional
epithelium to alveolar crest
Function :
a) Prevents extrusion
b) Resist lateral tooth movement

• Runs at right angle to long axis of tooth from cementum to
bone
• Immediately apical to alveolar crest grp.
• Limited to coronal 1/4th
• Function : resist horizontal and tipping forces.
Horizontal group

• Largest group
• Occupy almost 2/3rd of ligament.
• Extend from cementum in a coronal direction obliquely to
bone.
Function:
- Resist vertical masticatory forces and transform them into
tension on the alveolar bone.
Oblique group

• Radiate in irregular manner from cementum to the bone at
the apical region of the socket.
• Not seen on incompletely formed roots.
Function:
- Resist forces of luxation
- Prevent tooth tipping
- protect delicate blood & lymph vessels & nerves
traversing the PDL space.
Apical group

• Inserted into cementum from crest of interradicular septum in
multirooted teeth.
Function:
- resist tooth tipping
- torquing
- luxation
Interradicular group

• 3 types :
a) Elastin fibers
b) Elaunin fibers
c) Oxytalan fibers
• Elastin fibers: these are mature elastic fibers
• Conatins elastin protien which contains glycine, proline,
with little or no hydroxyproline & no hydroxylysine.
Immature elastic fibers

• Observed only in walls of afferent blood vessels.
• Elaunin fibers : may be found within the fibers of gingival
ligament.
• Oxytalan fibers : consist only microfibrillar component.
• They run parallel to the root surface in a vertical direction &
bend to attach to the cementum.

• Fine immature collagen fibers.
• Has argyrophilic staining properties.
• Are related to basement memberane of blood vessels &
epithelial cells.

• Located between & among principal fibers.
• Non-directional & randomly oriented.
• Traverse pdl space coronoapically

• Small collagen fibers associated with large principal collagen
fibers
• They run in all direction forming a plexus c/d as indifferent
fiber plexus

• It is a gel like matrix in which cellular & fibrous components
are embedded.
• Acc to Berkovitz ground substance account 65% of volume of
PDL.
• Noncollagenous protein – 10%
• Consists mainly – hyaluronase , glycosaminoglycans,
proteoglycans, & proteins.
• Substrate adhesion molecules – tenascin, osteonectin, laminin,
undulin, & fibronectin.

• Fibronectin & osteonectin – uniformly distributed.
• Tenascin – found in attachment zones.
• Laminin – basement membrane of epithelial cell rests of
Malassez
• Undulin – associated with tightly packed major collagen
fibrils.
• Proteoglycan including fibromodulin & perlecan are present.

BLOOD VESSELS :
Arterial supply- derived from inferior & superior alveolar
arteries.
It reaches PDL from 3 sources :
1. Branches in pdl from apical vessels that supply dental pulp.
2. Branches from intraalveolar vessels
3. Branches from gingival vessels

• Flow is from the ligament toward & into the adjacent alveolar
bone.
• Flow is alveolar lymph channels which are joined by dental &
interradicular lymph channels.

2 types of nerve fibers:
a) Sensory
b) Autonomic

Physical functions:
a) Soft tissue casing to protect
b) Transmission of occlusal forces to the bone
c) Attachment of teeth to bone
d) Maintainence of gingival tissue in their proper relationship.
e) Resistance to impact of occlusal forces(shock absorption)
i. Tensional theory
ii. Viscoelastic theory

Formative & remodelling function:
a) Cells of PDL participate in formation & resorption
b) Occur in physiologic tooth movement
c) Accommodation of periodontium to occlusal forces
d) Repair of injuries
3. Nutritional & sensory functions:
- Supply nutrients to cementum , bone &gingiva
4. Regulation of pdl width.

 Cell no. & activity decreases with age.
 Bone & cementum shows scalloping & PDL fibers attach to
the peak of scallops than over the entire surface.
 Any loss of gingival height promotes distructive changes in
pdl.
 Activity of pdl decreases .

Thickness varies in different individuals & different teeth
in same person.
Thickness of pdl is maintained by functional movements .
It is thin in functionless & embedded teeth.
Wide in teeth under excessive occlusal stress.
Supporting tissues of teeth long out of function – poorly
adapted to carry occlusal load by a restoration.
Applies – bridge abutments , teeth opposing bridges
dentures & teeth used as anchorage.www.indiandentalacademy.com

Acute trauma to pdl , accidental blow , or rapid
mechanical seperation –produce pathologic changes
Like fracture or resorption of cementum , tear of fiber
bundle , hemorrhage & necrosis
Leads to resoption of alveolar bone, widening of pdl &
loosening of teeth.
When trauma eliminated repair takes place

Orthodontic tooth movements
depends on resorption &
formation of both bone & pdl.
Develops pressure & tension
areas.

Periodontal ligament in the apical area of the tooth is
site of pathologic lesion
Periapical granuloma – contain epithelial cells that
undergo proliferation & form cyst
Commonest pathology – chronic inflammatory
periodontal disease.
Caused by toxin released from bacteria of dental
plaque.

• Bone is a specialized connective tissue that is mainly
characterized by its mineralized organic matrix.
• Living tissue which makes up body skeleton
• Toughness & elasticity
• Site for attachment of muscles & tendons
• Storage site.

BONE (Developmentally)
Endochondral bone Intramembranous bone

BONE (Histologically)
Compact (Cortical) Cancellous (spongy)

• Alveolar bone is that part of maxilla and mandible that
forms and supports the tooth socket.
• It is formed when tooth erupts to provide osseous
attachment to forming periodontal ligament.
• It gradually disappears when tooth is lost.

1. Houses roots of teeth.
2. Anchors roots of teeth to alveoli.
3. Helps to move teeth for better occlusion.
4. Helps to absorb & distribute occlusal forces.
5. Supplies vessel to Pdl.
6. Houses & protects developing permanent teeth while
supporting primary teeth.
7. Organises eruption of primary & permanent teeth.

2nd mnth of I.U life maxilla & mandible forms a groove
Contains tooth germ with alveolar nerve & vessels
Basal septa develops between adjacent tooth germs
Primitive madibular canal is seperated from dental crypt

External plate of Cortical bone
.
Inner socket wall - Alveolar bone proper /
lamina dura
.
Cancellous bone.

ALVEOLAR BONE
(FUNCTION)
ALVEOLAR
BONE
PROPER
LAMELLATED
BONE
BUNDLE
BONE
SUPPORTING
ALVEOLAR
BONE
CORTICAL
PLATE
SPONGY
BONE

• Surrounds the root of tooth
• Consists partly laminated & partly partly bundle bone.
• Laminated bone - lamellae arranged parallel to adjacent
marrow spaces

Bundle bone
- anchors principal fibers
- scarcity of fibrils in intercellular substance
- conatins few fibers so appear dark in H&E stain
- formed in area of recent bone apposition.

• Alveolar bone proper – inner wall of socket
• Perforated by many openings hence c/d cribriform
plate
• Bone between teeth – interdental septum
• Interdental & interradicular septa contain perforating
canals of Zuckerkandl & Hirschfeld

• Consist of cancellous bone bordered by cribriform plate
of approximating teeth and facial & lingual cortical plates
• If the interdental space is narrow, the septum consist of
only cribriform plate
• Meiodistal angulation of crest of interdental septum –
parellels line drawn between CEJ & approximating teeth
• Young adults – 0.75 – 1.49mm
• Increase with age – avg 2.81mm

CORTICAL
PLATES
SPONGY
BONE

• Compact bone
• Forms outer & inner plate
• Thinner in maxilla
• Maxilla – perforated
• Mandible – dense
• Bone underlying gingiva
• Cribriform plate & cortical plate are compact bone
seperated by spongy bone.

Spongy bone
Type I
(Interdental &
interradicular
trabecule are
regular)
Type II
(irregularly
arranged, numerous
, delicate)

• Trabeculae – less prominent in upper jaw
• Marrow spaces in alveolar process – hemopoietic /fatty
marrow.
• Condylar process, angle of mandible , maxillary
tuberosity- hemopoietic cellular marrow.

• Embryo & newborn – red hematopoietic marrow.
• This undergoes physiologic change – fatty / yellow
inactive(seen in adults).
• Red marrow found – ribs , sternum , vertebrae , skull &
humerus.
• Foci of red marrow seen in jaws accompanied by
resorption of bony trabeculae.

Periosteum:-Tissue covering the outer surface of the
bone.
• Inner layer of osteoblasts surrounded by osteoprogenitor
cells.
• Outer layer rich in blood vessels and nerves and
composed of collagen fibres and fibroblast.
• Cellular events at periosteum modulate bone size

Endosteum is the tissue lining the inner bone cavities.
• It is composed of single layer of osteoblasts and
sometimes a small amount of connective tissue.

2/3rd
INORG
ANIC
1/3rd
ORGANIC

• Alveolar bone
-Cells & intercellular matrix
-Remodelling
-Fenestration & dehichence
-clinical consideration
-Difference between adult & child alveolar bone
-Physiology of root resorption

OSTEOBLAST
 Produce the organic matrix
 Derived from multipotent mesenchymal cells.
 Most active secretory cells in bone
 Uninucleated & synthesize collagenous &
noncollagenous proteins
 Contain a cytoplasm rich in synthetic and secretory
organelles.

OSTEOCYTES
 Osteoblast produce extracellular matrix, osteoid
 Get trapped within matrix c/d as osteocytes.
 No. depends on rapidity of bone formation.
 They reduce in size & create a space around it –
osteocytic lacuna.
 Narrow extensions of lacunae – canaliculi.
 Osteolytic processes – present within canaliculi.

 At distal end contact adjacent cells & also maintain
contact with osteoblast & bone lining cells.
 Canaliculi penetrate bone matrix & permit diffusion of –
nutrients , gases & waste products.
 Interconnecting system maintain bone integrity &
vitality.

OSTEOCLAST
• Derived from greek word “bone & broken”
• Lie in resorption bays – Howship’s lacunae
• 40-100 microm in diameter with 15 -20 closely packed
nuclie.
• Cytoplasm – acid phosphatase.
• Cathepsin containing vesicles & vacuoles present close to
ruffled border – indicate resortive activity

• Haematopoietic mesenchymal stem cells
precursor
Pre osteoclast pre osteoblast condrocytes
Osteoclast osteoblast
Osteoprotegerin – inhibitor
Calcitonin - inhibitor
RANKL
M-CSF

• Mainly – type I collagen
• Noncollagenous protiens – osteocalcin , osteonectin ,
BMP , phosphoprotiens & proteoglycans.
• Paracrine factors – cytokines , chemokines & growth
factors : local control of mesenchymal condensation.

• Bone changes in shape, resistance to forces, repair of
wound, calcium & phosphate hemostasis in body.
• Throughout life
• Function :
1. Prevent accumulation of damaged & fatigued.
2. Allow bone to respond to changes in mechanical forces.
3. Facilitate mineral homeostasis.

Coordination of activities of OSTEOBLASTS
and OSTEOCLASTS.

• Regulation of bone remodelling :
• Systemic factors - hormones (parathyroid, calcitonin, vit
D3)
• Local factors - functional requirements of tooth, age
related changes in bone cells

Bone contains 99% body calcium(major source)
Decrease in the blood calcium levels
PTH stimulates osteoblast to relase IL-1 & IL-2
Coalesces monocytes into multinucleated
osteoclast
Monitored by parathyroid hormone
Leukemia inhibiting factor secreted
by osteoblast

Resorb bone , release calcium
Breakdown of collagen release osteogenic
substrates which stimulates osteoblast
Bone deposition
Feedback mechanism

Attachment of osteoclast to mineralized
surface of bone
Sealed acidic environment that
demineralizes bone & exposes organic
matrix
Degradation of matrix to its constituent
amino acids
Sequestration of mineral ions and amino
acids with in osteoclastwww.indiandentalacademy.com

• Superior alveolar arteries – maxilla
 Inferior alveolar arteries – mandible
 Supply to bone enters the interdental septa through
nutrient canals with veins, nerves, lymphatics
 Dental arterioles enter the marrow spaces through
perforations in cribriform plate
 Lymphatics

• FENESTRATION – isolated areas where root is
denuded of bone & root surface is covered only by
periosteum & overlying gingiva.
• Marginal bone is intact.

• DEHISCENCE - when denuded area extend through
marginal bone.
• 20% of teeth
• Predisposing factors – prominent root contours ,
malposition, labial protrusion.
• Facial> lingual
• Anterior>posterior
FENESTRATION & DEHISCENCE

• Orthodontic movement :
• Tooth movement only possible if resorption takes place
in direction in which tooth is being moved- creates
pressure
• This causes tension on pdl on opposite surface of root.
• Resorption - pressure side
• Apposition – tension side
• Enire alveolus is allowed to shift with tooth
• Pressure side increase in cAMP.

Teeth without antagonist:
• Spongy bone – pronounced rarefraction
• Bony trabeculae – less numerous & thin
• Alveolar bone proper is preserved bcoz it continues to
receive some stimuli from tension of pdl.

Healing fractures / extraction wounds
• Embryonic type of bone is formed later replaced
by mature bone.
• Emryonic /immature bone – greater no. , size &
irregular arrangement of osteocytes.
• Radiolucent than mature.

• Resorption
• Mandible – resorbs downward & outward
• Maxilla – upward & inward
• Cause – decreased blood supply , localized inflammation
or unfavourable pressure from prosthesis.

• Bone resortion is universal
• Occurs more on posterior teeth
• Related to bacterial plaque & pocket formation
• Exotoxins produced by gram –ve bacteria lead to
increase in cAMP which increase osteoclastic activity.

• Bone is reduced in height
• Bone margin remain approx perpendicular to
the tooth surface
• The interdental septa and facial and lingual
plate are affected

• Occur in an oblique direction
• A hollowed out trough is seen in the bone along the
side of root
• Base of defect is located apical to the surrounding
bone
• Increase with age
• Appear most often on the distal surfaces and mesial
surfaces

• Concavaties in the crest of
interdental bone confined
within the facial and lingual
wall
• They make about one third
(35.2 %) of all defects and
about two third (62 %) of all
mandibular defects.

• Produced by loss of
interdental bone including the
facial plates and lingual plates
without concomitant loss of
radicular bone
• More common in maxilla

• Plateau like bone margins caused by resorption of
thickened bony plates.
•Bony enlargement caused by
exostosis, adaptaion to
function or buttresing bone
formation.

•Fusion of cementum & alveolar bone with obliteration of the Pdl
•Occurs in teeth with cemental resorption.
•Results in resorption of root & replacement by bone tissue.
•Proprioception is lost.
•Occurs more frequently in primary dentition
•Clinical diagnosis.
•Radiographic diagnosis
http://www.psaltis.info/imageMFP.JPG

•According to krakowiak et al the prevalence of ankylosis
of primary molars was found to be 3.7% .
•Eighty-two of the 2234 children examined exhibited
ankylosis.
•Black (0.93%) <white (4.10%).
•The mandibular first primary molar was ankylosed at an
earlier age and more frequent.
•The frequency of ankylosis of the second primary molar
increased in older children.
•The high incidence of ankylosed primary teeth was seen
in children between seven and eleven years of age.
Ankylosed primary molars.ASDC J Dent Child, 1978www.indiandentalacademy.com

Feature Children Adults
Trabeculae Less More
Marrow spaces Large Small
Calcification Less More
Lamina dura Thin Thick
Pdl space Wider Less

With existing successor tooth:
• Pressure of erupting permanent tooth.
•Dental follicle & stellate reticulum
•Stellate reticulum cells s ecrete parathyroid hormone
related protien (PTHrH) that binds to PTHrH receptors
•Interlukin -1alpha also secreted.
•This stimulate monocyte recruiting factors like colony
stimulating factor, monocyte chemotactic protien etc.
•Monocyte fuse and differentiate osteoclast and
odontoblast cells.
Physiologic root resorption in primary teeth : molecular &
histological events;Jr of oral sciences;2007www.indiandentalacademy.com

•PTHrH – increase RANKL and downregulate OPG.
•PTHrH treatment of cementoblast – leads to reduction in
OPG & supports osteoclastogenesis.
•Physiologic resorption of primary teeth is not continuous
process & periods of active resorption is followed by
intermittent period of rest & also by period of repair.
•Cementum or bone depostion – prominent in delayed –
shedding stage.

•Degradation of PDL precedes root resorption &
sepecifically removal of fibers.
•Collagen digestion is mediated by matrix degrading
enzyme – matrix metalloproteinase (MMPs) & tissue
inhibitors of metalloproteinases(TIMPs).
•PDL cells from primary teeth produce more MMPs &
Respond to proinflammatory cytokines enhanching
expression of MMPs.
• with incresed forces – osteopontin & bone sialoprotein
more heavily expressed in PDL of resorbing primary teeth.

PRIMARY TEETH SHOWS LESS PROTECTING
FACTORS AGAINST ROOT RESORPTION
•According to Mabel et al PDL cells from primary &
permanent tooth have similar morphological features.
•Fewer ECRM clusters & higher immunoreactivity to
CK14 – primary teeth
•Howship’s lacunae found only in primary teeth,
associated with TRAP –positive cells & increase in COX-2
expression.
•OPG expression in primary teeth – non resorptive
cervical areas.
International Journal of Paediatric Dentistry ;2011.

•

Carranza 10th edition
Ten Cate’s ,Oral Histology 7th edition
Orban’s Oral Histology & Embryology 12th edition
Anil Kholi, Textbook of dental and Oral Histology and
Embryology
Shantipriya reddy , Essentials of Clinical Periodontology 2nd
edition
James Avery, Essentials of Oral Histology and Embryology
: a clinical approach
Physiologic root resorption in primary teeth: molecular and
histological events;journal of oral sciences ;2007

• Primary teeth show less protecting factors against root
resorption;International journal of Paediatric
dentistry;2011
• Ankylosed primary molars.ASDC J Dent Child, 1978

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