Development of tooth and periodontium

DEVELOPMENT OF TOOTHAND PERIODONTIUM

Dr. SONI BISTA1ST YEAR PG STUDENTPERIODONTOLOGY AND ORAL IMPLANTOLOGY

UNDER THE GUIDANCE:Assoc.Prof.Dr.MANDEEP SINGH DINGRAAsst.Prof.Dr.BIKASH KUMAR

A STAR IN THE

MAKING!!!

DEFINITIONOVERVIEW OF DEVELOPMENT OF TOOTHROOT FORMATIONSTAGES IN TOOTH GROWTHSIGNALING IN TOOTH DEVELOPMENTCEMENTOGENESISPDL FORMATIONALVEOLAR BONE FORMATIONDENTINOGINGIVAL JUNCTION FORMATIONCLINICAL CONSIDERATIONCONCLUSIONREFERENCES

CONTENTS

PERIODONTIUMGREEK MEANING: “PERI”_AROUND “ODONT”_TOOTH

“Tissue investing and supporting the teeth consists of Cementum, PDL, bone lining the alveolus and that part of the gingiva facing the tooth”_Tencate 5th edi.

“Tissue supporting the tooth are developmentally derived from the dental follicle proper, whereas those investing the tooth, that is gingiva, are an adaptation of oral mucosa” _Richard ten Cate

OVERVIEW OF DEVELOPMENT OF

TOOTH

NEURAL CREST DEVELOPMENT3 germ layer..Neural plate within ectoderm..

Neural tubes…Neural crest cells…

DERIVATIVES

PRIMARY EPITHELIAL BANDAfter 37 days of development

A continuous band of thickened epithelium forms around the mouth in upper and lower jaws

This band are roughly horseshoe shaped

Corresponds in position to the future dental arches of upper and lower jaws

Each band of epithelium called as primary epithelial band (Gives rise to)

DENTAL LAMINA VESTIBULAR LAMINA

(At about 7th week)

• First evidence of tooth development.• Continued and localized proliferative activity lead to formation of a

series of epithelial ingrowth into the ectomesenchyme at the sites corresponding to the position of the future deciduous teeth.

FATE: Total activity is about 5 years Eventually, the dental lamina disintegrates into small clusters of epithelium and is

resorbed. In situations when the clusters are not resorbed, (this remnant of the dental lamina is sometimes known as the cell rest of Serres) eruption cysts are formed over the developing tooth and delay its eruption into the oral cavity.

• From this, tooth development proceeds in 3 stages: bud stage, cap stage, bell stage.

DENTAL LAMINA

VESTIBULAR LAMINA:The vestibule forms as a result of proliferation of vestibular lamina into the ectomesenchyme

BUD STAGE

8TH WEEK

Represented by 1st epithelial incursion into the ectomesenchyme of the jaw.Supporting ectomesenchymal cells are closely packed beneath and around the epithelial bud…

CAP STAGE9-10

WEEKS

CONDENSATION OF ECTOMESENCHYME

DENTAL ORGAN

DENTAL PAPILLA

DENTAL FOLLICLE

Proliferativestage

Epithelial bud_proliferate into ectomesenchyme

enameldentin

pulpSupporting

tissue

BELL STAGE

11-12TH WEEK

OUTER DENTAL EPITHELI

UM

STRATUM

INTERMEDIUM

INNER DENTAL EPITHELI

UM

Histodifferentiation and morphodifferention

glycosaminoglycans

CERVICAL LOOP

ADVANCEDBELL

STAGE

Two important events:1.Dental lamina

joining the tooth germ to the oral epithelium breaks up into discrete islands of epithelial cells…

Separating the developing tooth from the oral epithelium.

2. Inner dental epithelium__folds__making it possible to recognize the shape of future crown pattern of the tooth.

INNERVATION:Clusters of blood vessels and pioneer nerve fibers are found ramifying around the tooth germ in dental follicle .

ROOT FORMATION

Major function of HERS(Schour and Massler) Induce and regulate root formation including the size, shape, number of root.HERS characters:1. Consists of inner and outer enamel

epithelium only.

Innercells(short in size) cells in

coronal root

region

Differentiation of radicular differentiation ofPapilla cells dental

follicle

Odontoblasts cementoblasts

First layer of acellular cementum

radicular dentin.

Enamel matrix protein Components of epithelial Basement

membrane

Hertwig’ epithelial root sheath

STAGES IN TOOTH GROWTH

DENTAL CEMENTUMThe dynamic tissue covering the root….

Cementum is the calcified, avascular mesenchymal tissue that forms

the outer covering of the anatomic root.Latin: “Caementum”:quarried stone[i.e. Chips of stone used

in making mortar]

It was first demonstrated microscopically in 1835 by two pupils of purkinje.

It is a specialized connective tissue that shares some physical, chemical & structural characteristics with compact bone.

cEmEnTum

CEMENTOGENESIS Cementum is deposited on the surface of root dentin HERS Hyaline layer of Hopewell-Smith/Intermediate Cementum (after basement supporting root sheath breaks up) • Secrete distinct class of enamel protein in the gap between

collagen fibers(from mantle dentin) and basement membrane.

This layer contains product of epithelial cell activity/form of enameloid

Thus the dentin of the root surface is covered by an epithelial product of the root sheath cells that is more mineralized than other dentin.

+ Functions to “cement” cementum into dentin as well as

provide the initial attachment of ligament fibrils to the tooth.

[Hertwig’s epithelial root sheath is broken up & separated from root, and differentiation of

cementoblasts lead to formation of cementum]

Cementogenesis….• Root sheath fragments into network that allows: follicular cells to pass through it + it comes into

apposition with newly formed root surface. differentiate into cememtoblasts deposit organic matrix against root surface and around

forming ligament fiber bundles/extrinsic fibers. mineralization of this matrix is called cementoid occurs with

deposition of apatite crystals

initially is matrix vesicles

followed by mineralization of collagen fibrils.

Growth factor families involved in the differentiation of cemetoblasts from dental

follicle....TGFβ 1-5BMP2-8

EGF & IGFPGE2 & PGF2α enhance

differentiation by activating protein

kinase cell signalling pathwayFibroblast growth

factor promotes proliferation, migration

& angiogenesisCAP, BSP and osteopontine helps in

attachment of differentiated cells to newly forming tissue

PRIMARY CEMENTUM First formed cementum is acellular

Develops slowly as tooth is erupting

Covers coronal two third of the root

Highly calcified.

Its collagenous component may be derived entirely from extrinsic fibers of the PDL(Sharpey’ fiber)

Also contain intrinsic fibers that are calcified and irregularly arranged or parallel to the surface.

SECONDARY CEMENTUM Develops after tooth is in occlusion. Rapidly formed and less mineralized Deposited around apical two third of the root. Cellular as cementoblasts gets trapped in lacunae within

matrix they form. Its Organic matrix contains collagen fibers derived from

2 sources extrinsic fibers of PDL_are arranged obliquely

as they enter cementum. intinsic fibers(formed as a result of cementoblastic activity)__are parallel to root. Secondary cementum formation is a continuous process Thus thickness of cementum on root surface increases with

age.

FATE OF HERS… Fragmentation of root sheath

disruption of its basal lamina

some cell are lost Most cells persists as strands/clusters

(transform into mesenchymal cells) (where collagen are trapped)

called as epithelial rests of malassez

-dark staining nuclei and little cytoplasm

-appear as a network within PDL close to cementum

-proliferate -are source of

epithelial cells that line dental cysts

PDL formation• After root formation_dental follicle PDL• In front of forming PDL increase rate of cell

division fibroblasts

collagen fibrils of PDL (oblique orientation) + ground substances of

PDL

First collagen bundle appear in the region immediately apical to the CEJ and give

rise to gingivodental fiber groups

Transeptal and alveolar crest fibers develop when tooth merge

into oral cavity

Sharpey’s fiber are fewer in no. and more widely spread

than those emerging from

cementum. _carranza’s

• Rearrangement of fiber ends in the plexus is supposed to accommodate tooth eruption without necessitating the embedding of new fibers into tooth and the bone.

BEFORE TOOTH ERUPTION:•Crests of alveolar bone is above CEJ•Developing fiber bundles of PDL are all directed obliquely.•More apical orientation

DURING TOOTH ERUPTION:•Level of alveolar crest comes to coincide with CEJ•Oblique fibers below the free gingival fibers becomes horizontally aligned called as alveolar crest fibers.•More coronal orientation.

TEETH IN FUNCTION:•Fiber bundles of PDL thickens and are constantly remodeled by fibroblasts

PDL homeostasis A remarkable capacity of PDL is that it maintains its width more or

less, despite the fact, it is squeezed in between two hard tissues. Various molecules have been proposed, which play a role in

maintaining an unmineralized PDL.

• Inhibit mineralized bone tissue

Msx2

• Prevents osteogening differentiation of PDL fibroblasts by repressing cbfa1 activity

Bone sialoprotein

• osteopontin

Matrix Gla protein(Inhibitors of mineralization)

Prostaglandins

ALVEOLAR PROCESS It is the portion of maxilla and mandible that

forms and support the tooth socket(alveoli)

It develops and undergoes remodeling with tooth formation and eruption; they are dependent bony structure.

It forms when the tooth erupts to provide the osseous attachment to the forming PDL & it disappears gradually after the tooth is lost.

BONE FORMATION

As PDL is forming;

new bone deposition

takes place around developing

Ligament fiber bundles against

crypt walls

Cells migrate into PDL from bone marrow (by way of vascular channels)

Occupy perivascular location within PDL

Reinforce the resident perivascular cells

To provide daughter cells

Migrate to bone and cementum

Differentiate into osteoblast and cementoblast and also PDL fibroblast.

Bone formationIntramembranous ossification

Formation of bone matrix

Formation of woven bone

Appositional growth & formation of harvesian system (osteon)

Endochondral bone formationFormation of cartiagenous

model

Stages of Intramembranous Ossification




Formation of bone collar around hyaline cartilage model.

1

2

3

4Invasion of internal cavities by the periosteal bud and spongy bone formation.

5Formation of the medullary cavity as ossification continues; appearance of secondary ossification centers in the epiphyses in preparation for stage 5.

Hyaline cartilage

Primary ossification center

Bone collar

Deteriorating cartilage matrix

Spongy bone formation

Blood vessel of periosteal bud

Secondary ossification centerEpiphyseal

blood vessel

Medullary cavity

Epiphyseal plate cartilage

Spongy bone

Articular cartilage

Stages of Endochondral Ossification

Cavitation of the hyaline cartilage within the cartilage model.

Ossification of the epiphyses; when completed, hyaline cartilage remains only in the epiphyseal plates and articular cartilages

GINGIVAGingiva is the part of the oral

mucosa that covers the alveolar processes of the jaws and tooth

root to a level just coronal to CEJ_McCall

DENTOGINGIVAL JUNCTION

• The epithelium of the gingiva which gets attached to the tooth is called as junctional or attachment epithelium.

• Consists of collarlike band of stratified squamous nonkeratinizing epithelium.

• Forms an epithelial barrier against bacteria.

JUNCTIONAL EPITHELIUM

DEVELOPMENT OF JUNCTIONAL EPITHELIUM AND GINGIVAL SULCUS

After enamel formation is complete, the enamel is covered with REE, which is attached to the tooth by a basal lamina & hemidesmosomes

When tooth penetrates oral mucosa, the REE unites with oral mucosa and transformed into JE

JE proceeds in an apical direction, forming a shallow groove, the gingival sulcus between circumference of tooth & gingiva that encircles the newly erupted tip of the crown

Gingival sulcus deepens as a result of separation of the REE from actively erupting tooth & JE attains its position at CEJ of fully erupted tooth

STAGES OF PASSIVE ERUPTION

SHIFT OF DENTOGINGIVAL JUNCTION

The teeth reach the line of occlusion.J.E and base of gingival sulcus are on the enamel

Stage 1



J.E proliferates so that part is on cementum and part is on enamel.

Stage 2



Entire J.E is on cementum and base of the sulcus is at CEJ.As J.E proliferates from the crown into the root,it doesnot remain at CEJ any longer than at any other area of the tooth.

Stage 3



J.E has proliferated farther on the cementum.the base of the sulcus is on the cementum, a portion of which is exposed.Proliferation of the J.E onto the root is accompained by degeneration of gingival and PDL fibers and their detachment from the tooth.

Stage 4

DURING INITIATION

ANODONTIA

SUPERNUMERY

DURING MORPHODIFFERENTIATION

CLINICAL SIGNIFICANCE

CONCLUSIONThe widespread occurrence of periodontal disease and the

realization that periodontal tissue lost to the disease can be repaired has resulted in considerable effort

to understand the factors and cells regulating the

formation,maintenance and regeneration of the

periodontium…..TenCate et al

REFERENCES• Carranza’s clinical periodontology,11th

edition• Orban’s oral histology and embryology,12th

edition.• Oral histology:development,structure and

function,A.R Tencate,4th edition.• Oral development and

histology,James.K.Avery,Pauline.F.Steele, Nancy Avery.• Images_Google .

Health & Medicine

Development of tooth and periodontium