Download Cementum

CEMENTUM

INTRODUCTION

CEMENTUM IN HEALTH

CONTENTS
 TYPES OF CEMENTUM

CLASSIFICATION

COMPOSITION

PERMEABILITY OF CEMENTUM

FUNCTION OF CEMENTUM

CEMENTO ENAMEL JUNCTION

CEMENTODENTINAL JUNCTION

THICKNESS OF CEMENTUM
 CEMENTUM IN DISEASE

HYPERCEMENTOSIS

ANKYLOSIS

CEMENTUM RESORPTION & REPAIR
 EXPOSURE OF CEMENTUM IN ORAL ENVIRONMENT

INTRODUCTION
 Periodontium is the functional unit of tissues
supporting the tooth.
 It consists of four principal components:




Gingiva
Periodontal ligament
Cementum
Alveolar bone
Cemetum- Its a calcified avascular
mesenchymal tissue that forms the outer
covering of anatomic root.
It provides anchorage mainly to the principal
fibres of periodontal ligament.
CEMENTUM
IN
HEALTH
TYPES OF CEMENTUM
 There are two main types of cementum:
Acellular(primary) cementum
Cellular(secondary) cementum
 Two main sources of collagen fibres in the
cementum are:
Sharpey’s fibres(extrinsic)-which are the
embedded portion of principal fibres of periodontal
ligament and are formed by the fibroblast
Intrinsic fibres-Fibres that belongs to the
cementum matrix and are produced by
cementoblast
Acellular cementum
it is the first cementum formed, it covers
approximately the cervical third or half of the
root.
 It does not contain cells.
 It is formed before the tooth reaches the
occlussal plane and its thickness ranges
from 30-230 micronmeter.
 Sharpey’s fibres make up most of the
structure of acelluler cementum which has a
principal role in suppoting the tooth.

Most fibres are inserted at approximately right
angles into the root surface and penetrate deep
into the cementum. But others enter from
several different direction
Acellular cementum also contains intrinsic
collagen fibrils that are calcified and irregularly
arranged or parellel to the surface

Cellular cementum
 It is formed after the tooth reaches the occlusal plane, is
more irregular and contain cells(cementocytes) in individual
spaces(lacunae) that communicate with each other through
a system of anastomosing canaliculi.
 It is less calcified tahn the acellular type.
 Sharpey’s fibres occupy smaller portion of cellular
cementum and are seperated by other fibres that are
arranged either parallel to the root surface or at random.
 ‘
•Sharpey’s fibres may be completely or partially
calcified or may have a central uncalcified core
surrounded by a calcified border
•Both cellular and acellular cementum are arranged
in lamellae separated by incremental lines parallel to
the long axis of the root. These lines represent “rest
periods” in cementum formation and are more
mineralized than adjacent cementum
CLASSIFICATION
 Based on location,morphology and histological
appearence Schroeder has classified the
cementum as follows:
Acellular afibrillar cementum(AAC)- It contains
neither cells nor extrinsic or intrinsic collagen fibres,
apart from a mineralized ground substance.
Acellular extrinsic fibre cementum(AEFC)-It is
composed of densely packed bundles of Sharpey’s
fibres and lack cells.It is a product of fibroblast and
cementoblast and in humans is found in the cervical
third of roots
 Cellular mixed stratified cementum(CMSC)-
It is composed of composed of extrinsic (sharpey’s
)and intrinsic fibers and contains cells.It is a co
product of fibroblast and cementoblasts.
 Cellular intrinsic fiber cementum(CIFC)Contain cells but no extrinsic collagen fibers.It is
formed by cementoblasts.
 Intermediate cementum It is poorly defined zone near the cementodentinal junction of certain teeth that appears to
contain cellular remnants of Hertwig’s sheath
embedded in calcified ground substance.
COMPOSITION
 Cementum is composed of both inorganic and organic
matter.
 The inorganic content of cementum (hydroxy apatite)is
45% -50% ,which is less than that of bone,enamel or
dentin .
 The organic matrix is composed 90% type I collagen ,5%
typeIII callagen,and non collagenous proteins like
enamel protein ,adhesion molecules like tenacin,and
fibronectin,glycosaminoglycans like chondroitin
sulphate and heparan sulfate.
 The protein extract of mature cementum promote cell
attachment and cell migration and stimulate protein
CEMENTOENAMEL JUNCTION
 Three types of relationship involving the
cementum exist at the CEJ .

In about 60% -65% of cases cementum
overlaps the enamel .

In about 30% of cases an edge-to-edge butt
joint exists.

In 5%-10% of cases the cementum and the
enamel fails to meet.In this case gingival
recession may result in accentuated sensitivity
because of exposed dentin.
CEMENTO DENTINAL JUNCTION
The terminal apical area of the cementum
where it joins the the internal root canal
dentin is known as cemento dentinal
junction.
When the root canal treatment performed
,the obturating material should be at the
CDJ .
There is no increase or decrease in the width
of the CDJ with age.
.
CEMENTUM
IN
DISEASE
HYPERCEMENTOSIS
 Hypercementosis refers to the prominent
thickening of cementum,with nodular
enlargement of apical third of the root.
 It is largely an age related phenomenon .
 It may be localised to one tooth or affect entire
dentition.
 Excessive proliferation of cementum may occur
in a braod spectrum of neoplastic and non
neoplastic conditions.
 ETIOLOGY
 Etiology varies and is not completely understood.
 The spike like type of hypercementosis results from
excessive tension from orthodontic appliances or
occlusal forcers .
 The generalised type may be associated with a variety of
situations like teeth without antagonists ,in teeth with
chronic pulpal and periapical infection.
 Hypercementosis of the entire dentition may occur in
patients with Paget’s disease.
ANKYLOSIS
 Ankylosis refers the fusion of cementum and
alveolar bone with obliteration of PDL.
 It develop after chronic peri apical
inflammation,tooth replantation,and occlusal
trauma and embedded tooth.
 Clinically, ankylosed teeth lack the physiological
mobility of norrmal teeth.
 Ankylosed teeth usually have a special metallic
percussion sound and if the ankylotic process
continues they will be in infraocclusion.
CEMENTUM RESORPTION & REPAIR
 Local condition causing cementum resorption
include trauma from occlusion.pressure from
malaligned erupting teeth,cysts and
tumours,orthodontic movement,periapical
diseases,and periodontal diseases.
 Systemic condition include calcium
deficiency,hypothyroidism,hereditary fibrous
osteodystrophy and paget’s disease.
EXPOSURE OF CEMENTUM TO ORAL
ENVIRONMENT
 Cementum may be exposed to the oral environment
in cases of gingival recession and as a result of loss
of attachment in pocket formation.
 In these cases, cementum is permiable to be
penetrated by organic substances,inorganic ions
and bacteria.
 Bacterial invasion of the cementum occur frequently
in periodontal disease.
 Cementum caries can also develop.