Cementum is the avascular mineralized tissue that covers the anatomical root of teeth. It acts as a medium for attachment of collagen fibers that bind teeth to surrounding structures. There are two main types of cementum: acellular cementum which forms early and contains Sharpey's fibers; and cellular cementum which forms later and contains cementocytes. Cementum is formed through cementogenesis, a process involving organic matrix formation by cementoblasts followed by mineralization. It undergoes changes with age and can repair itself through further deposition.

1. CEMENTUM
PROF. OLFAT M. GABALLAH
FACULTY OF DENTISTRY
TANTA UNIVERSITY

2. CONTENTS
• Introduction
• Cementogenesis
• Physical and chemical properties
• Types of cementum
• Incremental line of cementum
• Cells of cementum
• Cemento-enamel junction
• Age change of cementum
• Clinical consideration

4. INTRODUCTION
➢Cementum is avascular mineralized ectomesenchymal
tissue covering anatomical root,
➢It acts as a medium for attachment of collagen fibers that
bind the tooth to the surrounding structures.
➢It resembles bone in a few of its characteristics but is
avascular, non-innervated, and unable to remodel.
➢Cementum thickness varies from one tooth to another and
in different regions of the same tooth.
➢Cementum has the highest fluoride content of all the
mineralized tissues.

5. PHYSICAL PROPERTIES
• Color: it is light yellow. It can be distinguished from enamel by its
lack of luster and its darker hue.
• Hardness: It is less than that of dentin.
• Thickness: it is thinnest at CEJ ( 20- 50 um ) and gradually
increases in thickness toward the apical foramen ( 100 -150).
• Permeability: it is permeable from the PDL and dentin sides
( Cellular cementum is more permeable than cellular cementum )

6. Inorganic Materials Organic Materials
• On a dry weight base it consists of 45% to 50% inorganic
materials.
• The inorganic materials consist mainly of calcium and
phosphate in the form of hydroxyapatite crystals.
• Numerous trace elements are found in cementum with
varying amounts like copper, iron, magnesium, and
potassium.
• It also has the greatest fluoride level of all mineralized
tissues. The most prevalent ionic substitution is fluoride,
which is found in higher concentrations in acellular
cementum than in cellular cementum.
• It contains about 50% to 55% organic materials and water by
weight
The organic portion of cementum consists of
• Collagen fibrils (90%) and non collagenous protein (10%)
• Type I collagen is the predominant collagen of cementum.
• Noncollagenous proteins identified in cementum include:
polysaccharides (proteoglycans), glycoproteins, and,
phosphoproteins.
• Also, Alkaline phosphatase, bone sialoprotein, dentine matrix
protein, dentine sialoprotein, fibronectin, osteocalcin, osteonectin,
osteopontin, proteoglycanes, proteolipids, and several growth
factors.
• Enamel proteins also have been suggested to be present in
cementum
CHEMICAL PROPERTIES

7. STEPS OF CEMENTOGENESIS
• It consists of two steps
• 1- Organic Matrix Formation
• 2- Mineralization

8. CEMENTOGENESIS
Hard tissue formation reaches the future CEJ [cervical loop]
HERS proliferates downwards
Inner cells induce dental papillae cells to differentiate into odontoblasts
Formation of radicular predentin
Rupture of HERS [cell rest of mallassez]
The dental follicle comes in contact with dentin matrix
Differentiation of cementoblasts & cementum formation.

9. • Following complete crown formation, hertwig's epithelial root sheath (which is driven by the
coronoapical expansion of the inner and outer enamel epithelium) transmits an inductive message
to the ectomesenchymal peripheral pulp cells, potentially by secreting some enamel proteins.
• These cells develop into odontoblasts and form a layer of predentine.
• The ectomesenchymal cells from the inner region of the dental follicle come into touch with the
predentin shortly after hertwig's epithelial root sheath is disrupted.
• After receiving a reciprocal inductive signal from dentine or the surrounding Hertwig's epithelial
root sheath cells, infiltrating dental follicle cells develop into cementoblasts, which create
cementum.
• Apoptosis occurs in the cells of the Hertwig's epithelial root sheath, and some cells from the
fragmented root sheath form discrete masses surrounded by a basal lamina, known as epithelial
cell rests of Malassez, which persist in the mature periodontal ligament (ECRM are not simply
residual cells, but they play an important role in PDL maintenance and regeneration).

10. ORGANIC MATRIX FORMATION
• the newly differentiated cementoblasts first elaborate the
organic matrix or "cementoid". That consists of collagen fibres
and ground substances.
• The cementoblast extends its process (fibroblast-like behaviour)
into unmineralized dentin and deposits collagen intrinsic fibres
that mix with the collagen fibres of dentin matrix.
• The mineralization of mantel dentine begins internally and does
not reach the dentine surface until the fibres intertwine, at which
point the mineralization spreads and the dentine cementum
junction is formed.
• Adjacent fibroblasts of the dental follicle produce collagen
fibres that become embedded in the cementum matrix, allowing
the tooth to be attached to the surrounding bone.

11. • Perforating fibres or "Sharpey's fibres" are the
embedded section of periodontal ligament fibres in the
cementum . Then the cementoblasts have now entered a
quiescent stage near the cementum front, ready to act
when needed, whether for continued growth or repair.
• The cementum is applied in successive layers or increments
(rhythmic procedure) until it reaches its ultimate thickness.
• Cementoblasts become entrapped on the cementum
matrix and reside in lacunae in the apical part of the root
as cementum deposition progresses.
• The integration of some cementoblasts within the matrix
appears to be due to the cementoblasts' rapid matrix
deposition.
• On the cementum surface lining, a thin layer of cemented
tissue is normally visible.

12. • MINERALIZATION
• Mineralization begins when some cementoid tissue has been set down. Calcium and phosphate ions
found in tissue fluids are deposited in the matrix. Crystals of hydroxyl apatite are organized
along the fibrils. Apatite crystals can be seen aggregated into groups of nucleation centres, similar
to bone calcifications.

13. • Growth of cementum is a rhythmic process, as a new layer of cementoid is
formed, the old ones become calcified.
• A thin layer of cementoid tissue is usually observed on the cemental
surface.
• The cementoid tissue is formed of the uncalcified cementum matrix
Cementoid

14. TYPES OF CEMENTUM
1-Acellular Cementum ( extrinsic fibers cementum ) ( primary cementum )
2-Cellular Cementum ( intrinsic fibers cementum) (secondary cementum )
3-Intermediate Cementum.
4-Acellular Afibrillar Cementum

15. Acellular Cementum
• It is formed early in tooth development and is crucial during
the initial stages of tooth eruption and root development
• This type of cementum does not contain cementocytes
• Forms majority of the primary cementum
• Seen more in the cervical and middle thirds of the root.
• Contains a lot of extrinsic fibers (Sharpey’s fibers)
• The diameter of extrinsic fibers is roughly calculated at 3—6
μm. They show branching and anastomosing
• The main function of this type of cementum is tooth anchorage
• This type of cementum is formed slowly, hence the incremental
lines are more close to each other.

16. AC

17. • This type of cementum contains cementocytes within the lacunae.
• Usually formed after eruption hence forms majority of secondary
cementum.
• Seen more towards the apical part of the root.
• This type of cementum is formed rapidly so the incremental lines
are far from each other.
• Lacunae with canaliculi are seen, these canaliculi are directed
towards the periodontal ligament ( source of nutrient material
to the cementocytes ) .
• Mainly involved in repair and adaptation of cementum (
functioning cementum )
Cellular cementum

18. Ground section Decalcified section
Cementocyte cell

19. intermediate cementum
• It is a highly calcified non-collagenous material that is nearly identical
in its structure to the aprismatic enamel.
• It is situated between the granular layer of tomes and cementum. It is
restricted in the root apex as patches
because the Cells of Hertwig’s epithelial root sheath become trapped in a
rapidly deposited dentin or cementum
• It has been suggested that the intermediate cementum is formed by the
inner enamel epithelium of the root sheath.
• The function of intermediate cementum is probably to seal the surface of
the sensitive root dentin and cement the dentin with cementum.
• Some investigators reported that no such type of cementum is found.

20. ACELLULAR AFIBRILLAR CEMENTUM
AAC
• cementum overlaps the enamel for a short distance just coronal to the cemento – enamel junction .
This occurs due to early separation of reduced enamel epithelium near the cervix , allowing
the dental follicle to come in contact with the enamel surface. then the Connective tissue-derived
cells deposit AAC. On enamel surface

21. Incremental Lines Of Cementum
• Both cellular and acellular cementum are formed in successive
layers.
• The intervals between these successive depositions are represented
by the incremental lines of Salter
• Histochemical studies indicate that the incremental lines of salter
are highly mineralized areas with less collagen and more ground
substance.
• Deposition of cementum probably continues through life.

22. Cementodentinal Junction
• The junction between cementum and dentin is smooth in permanent dentition and sometimes
scalloped in deciduous dentition.
• Sometimes dentin is separated from cementum by a zone known as intermediate cementum.
This zone has features of both the cementum and dentin.
• This appears as a structure-less layer and is also called as
“ hyaline layer of Hopewell smith”

23. Cemento -Enamel Junction

24. Cementoenamel Junction
• The relation between cementum and enamel is variable. It is generally seen in three types –
• 1. Point junction (butt junction) – cementum and enamel meet each other at a sharp point.
• 2. Overlap junction – cementum overlaps the enamel for a short distance. This occurs due to early
separation of reduced enamel epithelium near the cervix early. allowing dental follicle to come in
contact with the enamel surface.
• 3. Gap junction – cementum and enamel do not meet.
This happens due to delay separation of Hertwig’s epithelial root sheath at the cervical area so, the
root cementum failed to deposit.

25. Cells Of Cementum
➢Cementoblast
➢Cementoclast
➢Cementocytes

26. Cementoblast
• It is the formative cell of cementum
• Cementoblasts are large cuboidal cells containing basophilic
cytoplasm and vesicular nuclei.
• Cementoblasts show all features characteristic of cells
capable of protein synthesis and secretion.
• They exhibit a well-developed rough endoplasmic
reticulum, and Golgi apparatus, numerous mitochondria, a
large nucleus that contains prominent nucleoli, and
abundant cytoplasm.
• Cementoblasts lay down the organic matrix with
collagenous fibers where the hydroxyapatite becomes
crystallized

27. Cementocyte
• Cementocyte is similar to osteocyte. It is seen in a space
designated as a lacuna. The cell is spider shape & possess
radiating processes mostly directed toward the periodontal (
source of nutrition )
• These processes may branch & frequently anastomose with
those of neighboring cells.
• The cytoplasm of cementocytes in deeper layers of cementum
contains few organelles, the endoplasmic reticulum appears
dilated, & mitochondria are spares.
• These characteristics indicated that cementocyte is marginally
active cells.

28. Cementoclast
• It resembles osteoclast.
• It is mononucleated or multinucleated giant cells, often located in
Howship’s lacunae
• It originated from circulating monocytes.
• Resorption of cementum occurs under certain conditions
Like tooth shedding , trauma, pathological diseases,
Calcium deficiency.

29. Functions of Cementum
• Anchorage: the primary function of cementum is act as a medium for attachment
of collagen fibers that bind the tooth to alveolar bone.
• Adaptation: deposition of cementum helps to compensate for the occlusal/ incisal
wear of the tooth substance.
• Repair: minor root fractures and resorption is repaired by deposition of new
cementum.
• The types of repair of cementum :
anatomic repair – repair reestablishes the outline of the root.
Functional repair – if the resorption or defect is large then only a thin layer of
cementum is deposited and alveolar bone proliferates so that a proper functional
relationship is established.
• The anatomical root outline is not reconstructed and a bay-like recess remains.

30. Age Change of Cementum
Permeability ( by age the permeability of cementum decreases gradually ). The permeability from the
periodontal side is lost except in the most recently formed layer of cementum. While the permeability from the
dentin side remains only in the apical region
1. Hypercementosis
Hypercementosis is an abnormal thickening of tcementum.
It may affect one tooth, entire dentition, or only a part of the tooth.
If the overgrowth improves the functional quality of cementum, it is termed cementum hypertrophy.
While, if the overgrowth occurs associated with a pathological condition, it is termed cementum hyperplasia.

32. CLINICAL CONSIDERATION
• Cementum is painless to scale and will repair itself by further deposition.
• Cementum serves to seal the ends of the dentinal tubules to decrease root sensitivity and
to prevent the spread of periodontal-originated infection to the pulp.
• Cementum has more resistance to resorption than bone
• This difference in resistance may be attributed to that, the bone is richly vascularized,
whereas cementum is avascular. For this reason, the proper orthodontic movement is
made possible without cementum resorption but bone resorption leads to tooth
migration.
• Cementum resorption may occur after trauma or excessive forces or improper
orthodontic treatment.
• Cementum resorption ( root resorption ) occurs during tooth shedding ( physiological
process )

33. REFERENCES
➢Nanci a: wheeler's dental anatomy, physiology, and Occlusion. 11th edition - November 9, 2019
➢Kumar GS: Orban’s oral histology and embryology. 15Th Edition 2019
➢Avery: essentials of oral histology and embryology. A Clinical approach, 3rd edition, elsevier's
publisher, Philadelphia.
➢https://2u.pw/oERMmFM
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