4 Cementum

Acellular cementum (20-50 m)

Cellular cementum (150-200 m)

Physical Characteristics

2- Thickness

1-Color

Light yellowLighter in color than dentin

3- Permeability

Permeable from dentin and PDL sides.

Cellular C is more permeable than acellular C.

Chemical Composition

45-50 % Inorganic substances

50-55% Organic substances

Hydroxyapatite crystals

Collagen

protein

Polysaccharides

Trace elements

Cementum contains the greatest amount of fluoride in all mineralized tissues

Cementum Structure

Acellular cementum Cellular cementum

Cementoid layer

MalassezCementocytes

Acellular Cementum Thickness is 20-50 µ.

It is clear and structureless

Covers the coronal half of the root.

Incremental lines of Salter are parallel to the surface.

Sharpey’s fibers space can be seen in it .

Alternating layers of

a cellular and cellular cementum could be seen.

Cellular Cementum

Lacunae of cementocytes

Cementocytes

PDL side

Dentin side

CementocytesIncremental lines of Salter

Cementocyte And Osteocyte

Dentin side

PDL side

Lacuna

Canaliculi

Osteocyte

Cementocyte And Osteocyte

Periodontal ligament side

Dentin side

Lacuna

Canaliculi

Osteocyte

Cellular Cementum

Dentin side

PDL side

Viable superficial

cementocytes

Degenerated deep layer’s cementocytes

Incremental Lines Of Salter

They are hypermineralized area with less collagen fibers and more ground substance

In acellular C In cellular C

Intermediate CementumPremature

degeneration of epith. Root sheath of Hertwig ( after

odontoblasts differentiation and

before dentin formation)

It occur at apical 2/3 of premolars and molars roots and rare in incisors and deciduous teeth

Contains entrapped

epithelial cells

Cemento Dentinal Junction

CD

Smooth in permanent teeth Scalloped in deciduous teeth

30% cementum meets the enamel

in a sharp line

10% cementum and enamel doesn’t meet because of

delayed separation of epith root sheath of Hertwig (area of dentin not covered by C).

60% cementum overlaps E (afibrillar

cementum)

Cemento Enamel Junction

Afibrillar Cementum

The enamel at cervical area not covered by

reduced dental epithelium before

tooth eruption

The connective tissue of the dental sac lay down

cementum on the exposed enamel

Types Of Cementum

• 1- Acellular cementum

• 2- Cellular cementum

• 3- Intermediate cementum

• 4- Afibirllar cementum

Functions Of Cementum

1- Acts as a medium for attachment of collagen fibers of PDL (Sharpey’s fibers).

2- The continuous formation of cementum keeps the attachment apparatus intact.

Cementoid T

Cementoblast

3- Cementum deposition epically compensate for the attrition.

4- It is a major reparative tissue

( as in case of fracture or resorption of root)

Cementogenesis

• 1- Matrix formation • 2- Maturation

Collagen fiber type I

Ground substance

Hydroxy apatite crystals

1- Matrix formation

• Cementum is formed during root formation

Future C E J Epith. Diaph.

H E R

D

Cementoblasts

Cementoblast is a protein forming and secreting cell.

D

Cem

ento

bla

st

Large open face nucleus

R E R

Golgi apparatus

Mitochondria

Alkaline phosphatase

Secretory granules

Collagen fibers + ground substance.

Cementum

Cementoid layer

Cem

ento

bla

sts

Maturation occur layer by layer for the collagen fibers

Age Changes Of The Cementum

DD

Localised

1- Hypercementosis.

May affect one tooth or all teeth Hypercementosis

Hypercementosis hyperplasia

Hypercementosis hypertrophy

Increase number of Sharpey’s fibers

Decrease number of Sharpey’s fibers

Types Of Hypercementosis

2- Permeability

From periodontal

side, but remain at the

superficial recently formed

layers

From dentin side

remains at apical area

ONLY