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CememtumPhysical characteristics

1. Colourlight yellow and lighter in colour than dentin2. Thickness acellular cementum (present in cervical and middle 1/3)

is thicker than cellular cementum (present in apical 1/3)3. Permeability permeable from dentin and PDL side. Cellular dentin

is more permeable than acellular dentin

Chemical composition45%-55% inorganic substance and 50% organic substancesCementum contains he greatest amount of fluoride in all mineralisedissues.Ratio of organic: inorganic ratio is nearly equal so cementum can bestudied in both G.S. and D.S

Cementum structureCant see cells and soft tissue in G.S so only lacunae of cementocytes areseen while in D.S cementocytes can be seen.

Acellular cementumClear and contains no cellsCovers the coronal half of the root cervical 1/3 and parts of M 1/3Less permeable than cellular dentinIncremental lines of salter are parallel to the surface and closer toeach otherSharpeys fibers space can be seen in it

Cellular cementum The processes of cementocytes are longer on the PDL side than onthe dentin side as there are more nutrition and blood in the PDL

Note that processes on osteocytes are of equal length while processes on cementocytes are unequal in length.

Incremental lines of SalterHypermineralized area with less collagen fibers and more groundsubstance

They are closer to one another in acellular dentin as that part of the root isformed slowly so cells take more rest while the incremental lines arefurther apart in cellular dentin.

Intermediate Cementum: premature degeneration of ERSH (afterodontoblasts differentiation and before full thickness of dentin forms)occurs at apical 1/3 of premolars and molars root and rare in incisors anddeciduous teeth. Intermediate cementum has both properties of dentinand cementum

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Afibrillar Cementum : formed due to rupture of R.E.E. and enamel exposedto dental sac and cementum starts forming on top of enamel,covering the enamel for a very short distance. It is usually formedat the cervical 1/3 as the R.E.E. is very thin there.

Types of cementum1. acellular cementum2. cellular cementum3. intermediate cementum4. afibrillar cementum

Cemento dentinal junction :1. 30% cementum meets the enamel in a sharp line2. 10% cementum and enamel doesnt meet because of delayed

separation of ERSH (area of dentin not covered by cementum) leads to enamel pearl or uncovered dentin

3. 60% cementum overlaps enamel afibrillar cementum

Functions of cementum1. Acts as a medium for attachment of collagen fibers of PDL2. The continuous formation of cementum keeps the attachment

apparatus intact. the turnover rate of PDL is very high and oldfibers get replaced by new fibers continuously

3. Cementum deposition apically compensate for attrition as teethgets attrition, they lose contact e.g. the upper and lower incisors.However, as teeth always seek contact, they will move up and leave

a space in the apical root and this space will be filled withcementum

4. Its a major reparative tissue however, if its a major problem suchas a vertical root fracture, cementum cant compensate for it

Cementogenesis1. Matrix formation cementum is formed during root formation.

Cementoblast is a protein forming and secreting cell.

2. Maturation maturation occurs layer by layer for collagen fibers

Ages changes of cementum1.Hypercementosis

May affect one tooth or all teethCan be named something else if its localized.

Types of hypercementosis

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1. Hypercementosis hypertrophy functional : increasein number of Sharpeys fibers. If the piece of newlyformed cementum has sharpeys fibers in it, itsfunctional.

2. Hypercementosis hyperplasia non-functional:decrease in number of Sharpeys fibers

2. PermeabilityDecrease form PDL side but remain at thesuperficial recently formed layersPermeability from dentin side remains at apicalarea only (area where cementocytes are there)

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