3. DEFINITION
Cementum is the calcified a vascular mesenchmal tissue that
forms the outer layer cover of the anatomic root
Types of cementum
There are two main types of cementum they are:- 1.A celluar
cementum and
2.cellular cementum
The two main source’s of collagen fibers in cementum are
sharpey’s fibers which are the embedded portion of principal
fibers of the
4. Periodontal ligament and are formed by the
fibroblasts
Fibers that belong to cementum matrix and are
produced by cementoblasts
Cementoblasts also form the non collagenous
components of the inter fibrillar ground substance
such as proteoglycans, glycoproteins and
phosphoproteins
Proteoglycans are the most likely to play a role in
regulating cell-cell and cell-matrix interactions
5. COMPOSTION
The major proportion of the organic matrix of a
cementum is composed of type one (90%) and type
three about (5%) collagens
ACELLULAR CEMENTUM
It is the first cementum formed, covers
approximately the cervical third or half of the root
and does not contain cell’s
6. This cementum is formed before the tooth reaches
the occlusal plane and it’s thickness ranges froms
30 to 230 um
Sharpey’s fibers are completely calcified, with the mineral
crystals. Oriented parallel to the fibrils as dentin and bone
except in a 10 -50 um wide zone near the cementodentinal
junction where they are only partially calcified
7. •Acellular cementum also contains intrinsic collagen fibrils
that are calcified and irregularly arranged or parallel to the
surface
•CELLULAR CEMENTUM
•Celluar cementum formed after the tooth reaches the
occlusal plane is more irregular and contain cell’s
(cementocytes) in individual spaces (lacunae)
8. that communicate with each other through a
system of anastomising canaliculi
Cellular cementum is less calcified than the
acellular type
Sharpey’s fibers occupy a smaller portion of
cellular cementum and are separated by other fibers
that are arranged either parallel to the root surface
Both acellular and cellular cementum are aranged
in lamellae separated by incremental lines parallel
to long axis root this lines are called rest periods
9. PERMEABILITY OF CEMENTUM
In very young animal’s acellular cementum and
cellular cementum are very permeable and permit
the diffusion of dyes from the pulp and external root
suface
THICKNESS OF CEMENTUM
Cementum deposition is a continuous process that
proceeds at varying rates
10. Cementum formation is most rapid in the
apical regions where it compensates for
tooth eruption, which it self compensate for
attrition
The thickness of cementum on the coronal
half of the root varies from 16-60um
It attains greatest thickness (upto 150-200
um) in the apical third and in the fraction areas
Abnormalities in the thickness of cementum
may range from an absence of cellular
cementum to an excessive deposition of
11. The term hyper cementosis refers to a prominent
thickening of cementum
Hyper cementosis occurs a generalisied thickening of
the cementum
CEMENTUM RESORPTION AND REPAIR
Cementum resorption may be caused by local and
systemic factors
12. Local condition causing cementum resorption
include trauma from occlusion orthodontic
movement pressure from malaligned erupting teeth
cysts and tumors teeth with out junctional
antagoinsts
Systemic condition citied as predisposing to or
including cemental resorption include calcium
deficiency hypothyroidism, hereditary fibrous
osteodystrophy
13. Cementum becomes exposed to the oral
environment in cases of gingival recession and as
result of loss of attachment in pocket formation
CEMENTO ENAMEL JUNCTION
The cementum at and immediately subjacent to
cemento enamel junction is of particular clinical
importance in root scaling procedures
14. Three types of relationships involving the
cementum may exists at cementoenamel junction
In about 60 -65% of cases, cementum over laps the
enamel in about 30% an edge-edge but joint exists
and 5-10% the cementum and enamel fail to meet
CEMENTO DENTINAL JUNCTION
The terminal apical area of cementum where it
joins the internal root canal dentin is known as
cemento dental junction
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