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(4) Cementum & PDL (Development (Stages (2) Bud Downward growth of…
(4) Cementum & PDL
Development
Week 4
: Stomatodeum (Primitive Oral Cavity)
Top
: Frontal Prominence (Brain)
Bottom
: Developing Heart
Side
: 1st Arch
Week 6
: Tooth Formation
Oral epithelium (Gives rise to enamel epithelium)
Mesenchymal cells
Stages
2)
Bud
Downward growth of epithelium
Determines tooth morphology
3)
Cap
Unequal epithelium growth
4)
Bell
Unequal epithelium growth
Determines position/height of cusps
Early stage:
Histodifferentiation
Advanced stage:
Morphodifferentiation
1)
Placode
Downward growth of epithelium
Components
Oral Epithelium
Enamel Organ
Enamel
Differentiated
:
Ameloblasts
Undifferentiated
:
IEE (Columnar) into ameloblasts
OEE (Cuboidal)
Stellate Reticulum (GAGs)
Mesenchyme
Undifferentiated:
Dental Papilla
Dentin
Pulp
Undifferentiated:
Dental Follicle
Located bottom of enamel organ; Surrounds entire organ
Cementum
PDL
Alveolar Bone
Differentiated:
Cementoblast
Cementocyte
Fibroblast
Differentiated:
Odontoblast
Fibroblast
Macrophages/Dendritic/Lymphocytes
Undifferentiated Mesenchyme
Hertwig's Epithelial Root Sheath
Located at
cervical
root of enamel organ
Fusion of IEE & OEE
Function (1): Guides root formation
Function (2): IEE causes papilla differentiation into odontoblast
Function (3): Secretes
Hyaline Layer of Hopewell Smith
(Binds cementum to dentin)
Fate (1): Apoptosis
Fate (2): Become
Cementum
Fate (3): Become
PDL
Fate (4): Become
Epithelial cell rests of Malassez
(Induce undifferentiated cells to differentiate)
Fate (5): Become
Cementoblasts
Cementum
Cementum
Structure
Thickest at apex/root
Thinnest at cervical area
Continuous deposition throughout life
Cementocyte will degenerate (Avascular) unlike bone
Supporting
NO blood vessels
NO nerves
NO lymph
SUPPORT FROM PDL
Types
Extrinsic Fibre
:
Fibres operating outside
Perpendicular to root surface
Intrinsic Fibre
:
Fibres operating inside
Parallel to root surface
Common Type
Acellular Extrinsic Fibre
First formed
Mainly for Attachment
Cellular Intrinsic Fibre
Found near root
Cementogenesis
Collagen/ECM
Cementoblast entomed
Matrix vesicles
(like dentinogenesis)
Heterogeneous nucleation
Incremental lines of (Salter)
Acellular vs Cellular
L
OSER
FRCS
DPH
Location: Apical/Cervical
First: First/Second
Rate: Fast/Slow (Lines)
Calcification: More/Less
Sharpey: More/Less
Demarcation(Dentin): Clear/Unclear
Precementum: Yes/No
Housing: Lacunae/Canaliculi
L-F-R-C-S-D-P-H
Clinical Implications
PDL
Increase
(1) Children
(2) Occlusal Loading
Decrease
(1) Aging
Decrease fibroblasts
Decrease organic matrix/cells
Decrease width of PDL
Decrease repair/regeneration
Increase elastic fibres
Irregular structure
Guided Tissue Regeneration
Block gingival/epithelial cell growth
Allow PDL & Bone to regenerate
Cementum
Increase
(1) Tooth Grinding
(2) Functional position
(3) Age
Becomes less permeable
Increase width
Increase resorption bays
Decrease
Dentinal Hypersensitivity
Cementum meets Enamel (30%)
Cementum does not meet Enamel (10%)
Cementum grows over Enamel (60%)
Cementicle (Hang Around)
Result of trauma
Can be free in PDL
Masses of cementum
Hypercementosis
Harder to extract
Ankylosis - Immobility
Cementum & Alveolar Bone fuse
PDL obliterated
PDL
Structure
:
Hourglass shape
Narrowest at mid root
Between root & lamina dura
Components
:
Supportive
:
Nerves
Vessels
Lingual & Palatine arteries
Nerves
Sensory
Nociception
Myeliated & Unmyelinated
Autonomic
Periodontal blood vessels
Unmyelinated
Blood Vessels
Lingual Artery
Palatine Artery
ECM
Collagen (Develop from tooth side)
Reticulin (Type 3)
Oxytalan / Elastin
GAG/GP
Sharpey Fibres (A-H-O-A-I)
Alveolar Crest (Vert)
Horizontal (Hori)
Oblique (Vert);
Develop first
Apical (Vert)
Inter-radicular (Only in multi rooted; Both)
Cells Types
:
Ectomesenchymal cells
Epithelial cell rests of Malassez
Fibroblasts (
Synthesize & Degrade)
Osteoblasts/Odontoblast/Cementoblasts
Osteoclasts/Odontoclast/Cemetoclast
Macrophage/Monocyte
Functions:
(1) Sensory
(2) Attachment
(3) Nutritive
(4) Absorb Shock
(5) Regenerative
S-A-N-A-R
