11 - Histogenesis, morphology and physiology of dental cementum. Anatomy and chemical composition. Characteristics of dental cemuntum in childhood

Where do the cells that make up cementum come from? (an element of tooth germ)?

dental follicle

What are the two tissues involved in cementogenesis?

• Mesenchymal - derived from dental follicle

• Ectodermal - from where Hertwig’s epithelial sheet originates

Describe cementogenesis

• Occurs after enamel is completely formed

• Differentiation of odontoblasts from ectomesenchymal cells

• Fragmentation of Hertwig’s epithelial root sheath

• Differentiation of cementoblasts from Hertwig’s sheath cells or follicle cells

• Cementogenesis is made by cementoblasts - which deposit organic matrix of cementum and its mineralisation (cementoid or precementum)

• Completed with the construction of root apex foreclosure

what is cementogenesis made by and what do they do?

• Cementogenesis is made by cementoblasts - which deposit organic matrix of cementum and its mineralisation (cementoid or precementum)

when does cementogenesis occur?

after enamel is completely formed

Morphology of cementum

An angel carries me in

• Acellular afibrillar cementum - located cervical area, composed of a mineralised matrix but there’s no cells or collagen fibres in it

• Acellular extrinsic cementum - located from cervical area to middle of root. Contains fibroblasts arranged perpendicular to root surface

• Cellular intrinsic fibre cementum - cementocytes embedded in matrix of closley spaced fibrils produced by cementoblasts

• Mixed layer cementum - in various places along root

• Intermediate Cementum - thin, acellular, amorphous layer of mineralised structure. Located immediately above the dentin along entire root surface

An angel carries me in

intermediate cementum

• thin, acellular, amorphous layer of mineralised structure. Located immediately above the dentin along entire root surface

Mixed layer cementum

in various places along root

Cellular intrinsic fibre cementum

• cementocytes embedded in matrix of closley spaced fibrils produced by cementoblasts

Acellular extrinsic cementum

• located from cervical area to middle of root. Contains fibroblasts arranged perpendicular to root surface

Acellular afibrillar cementum

• located cervical area, composed of a mineralised matrix but there’s no cells or collagen fibres in it

Physiology of cementum

• it is a hard, avascular connective tissue that cover root of teeth

• Does not undergo continuous remodelling like bone but continues to increase in thickness throughout individuals life

Mineral composition of cementum

• less mineralised than dentin

• Hydroxyapatite with small amounts of amorphous calcium phosphates present

• Hydroxyapatite in cementum isn’t pure, it contains ions incorporated into mineral phase during mineralisation

• High fluoride content compared to other mineralised tissues

Organic composition of cementum

• collagen type 1 and 3

• non collagenous proteins - bone sialoprotein and osteopontin

Mineral and organic composition of cementum

Mineral Composition

• less mineralised than dentin

• Hydroxyapatite with small amounts of amorphous calcium phosphates present

• Hydroxyapatite in cementum isn’t pure, it contains ions incorporated into mineral phase during mineralisation

• High fluoride content compared to other mineralised tissues

Organic composition

• collagen type 1 and 3

• non collagenous proteins - bone sialoprotein and osteopontin

Characteristics of dental cementum in childhood

• relatively thin

• less mineralised

• primarily acellular

• reduced repair capacity