Growth and development of tooth/ oral surgery courses

GROWTH
AND
DEVELOPMENT OF TOOTH
INDIAN DENTAL ACADEMY
Leader in continuing Dental Education
www.indiandentalacademy.com

CONTENTS
• Introduction
• Definition of Growth & Development
• Formation of Dental lamina
• Developmental stages of tooth
• Development of Enamel, dentin, cementum, pulp,
periodontal ligament.
• Factors affecting growth & development
• Developmental anomalies and prosthetic
considerations
• Summery & Conclusion
• References. www.indiandentalacademy.com

INTRODUCTION
It is essential to study the growth &development of tooth, to
diagnose & treat the developmental anomalies of teeth
successfully.
According to Todd.
• Growth refers to an increase in no and size
• Development refers to an increase in complexity and maturity.
• Growth may be defined as an increase in weight and spatial
dimensions that an organism or organ goes through. The
organism or organ gets heavier and takes up space. For growth
to occur, three things must happen: (1) increase in number of
cells, (2) increase in size of cells, and (3) increase in the product
of the cells.
• Development is an organism or organ going toward maturity.www.indiandentalacademy.com

FORMATION OF DENTAL LAMINA
• At about 21st
day of embryonic life the embryo folds along two planes
rostocaudal and lateral.
• The head fold is critical for the formation of primitive stomatodeum or oral
cavity, lined by stratified squamous epithelium, oral ectoderm.
Neural Crest Cells: This is ectomesenchymal tissue, termed neural crest from
its site of origin, arises from crest of neural fold, where neutralizing and
epidermalizing influences the interact.
- Pleuripotential cells with great migratory propensities.
Primary Epithelial Band: Roughly horse shoe shaped epithelial bands
corresponding in position to future upper and lower jaws.
Formed as a result of change in orientation of mitotic spindle and cleavage plain
of dividing cells and gives rise to dental lamina and vestibular lamina.

• The band of epithelium that invades the underlying
ectomysenchyme along each of horse shoe shaped future dental
arches called Dental lamina at about 6th
week of embryonic life.
Importance:
• Primordium for the ectodermal portion of deciduous teeth.
• Successional tooth buds .
• Buds for permanent molars from distal extension of dental
lamina.
• Dental lamina degenerates at about 5th
year of life.
• Remnants persist as epithelial pearls / islands.
Vestibular Lamina / Lip Furrowband:
• Epithelial thickening labial and buccal to dental lamina in each
dental arches.
• Forms oral vestibule.www.indiandentalacademy.com

Dental lamina

STAGES IN TOOTH DEVELOPMENT
The stages are named after the shape of the epithelial part of
the tooth germ.
1) BUD STAGE:
a) The ectodermal cells along the dental lamina multiply
rapidly in to round or ovoid swellings at different points
corresponding to the position of future deciduous teeth.
b) These form the primordium for the enamel organs of the
tooth bud.
c) It consist of
i. low columnar cells at periphery and polygonal cells at the
centre.
ii. Dental papilla.
iii. Dental sac.

Bud stage

2) CAP STAGE:
This stage is characterized by the shallow invagination on the
deep surface of the bud as a result of continued proliferation.
• In this stage cells of enamel organ can be histologically
differentiated as follows:
• Outer enamel epithelium (OEE). – peripheral cuboidal cells.
• Inner enamel epithelium (IEE) – columnar cells.
• Stellate reticulum
–polygonal cells located in the center.
–provides cushion like effect, thus supports
and protects delicate enamel forming cells
• Enamel knot – the densely packed cells in the center enamel
organ.
• Enamel cord – a vertical extension of the enamel knot between
inner and outer enamel epithelium.
• Dental papilla – the ectomesenchymal cells proliferate and
condense under the influence of proliferating epithelium.
• Dental sac – the dense fibrous layer.

Cap stage

3) BELL STAGE:
• The epithelial invagination deepens and the margins continue to
grow, thus the enamel organ assumes bell shape.
• Stage consist of
• IEE – Single layer of tall columnar cells called ameloblasts.
• Stratum Intermedium – squamous cells present in between
IEE and stellate reticulum. Shows high degree of mitotic
activity.
• Stellate reticulum – star shaped cells. Collapses before enamel
formation.
• OEE – flattens to low cuboidal form.
– surface laid in folds at the end of bell
stage prior to enamel formation begins.
• Dental lamina
• Dental papilla – odonto blasts differentiation.
• membrane performativa.
• Dental sac – circular arrangement of fibers and resembles
capsular structure.

Advanced bell stage
Bell stage with permanent tooth bud

4) ADVANCED BELL STAGE :
• Future dentino enamel junction.
• Cervical portion of enamel organ forms the hertwig’s
epithelial root sheath.
Hertwig’s Epithelial Root Sheath and Root formation:
• Root development starts after enamel and dentin formation
reaches future cemento enamel junction.
• Enamel organ forms hertwig’s epithelial root sheath
consisting of inner and outer enamel epithelium. It modes
the shape of roots and initiates radicular dentin formation.
• The sheath looses its continuity after radicular dentin
formation.

• Cementoblast form cementum over dentin.
• Epithelial diaphragm – the inner and outer enamel
epithelium bend at the future CEJ into horizontal plane
narrowing wide cervical opening. The cells proliferate
along with adjacent connective tissue cells of pulp.
• Apical foramen opening is narrowed by the deposition of
dentin and cementum at the apex of root.
• In multi rooted teeth the differential growth of epithelial
diaphragm causes division of root trunk in to two or three
roots.
• The long tongue like extensions of the horizontal
diaphragm develops two in mandible, three maxilla.
Before this the free ends grow towards each other and fuse.
• The cervical opening of coronal enamel organ is divided in
to two or three openings and dentin formation starts on the
periphery of each opening.www.indiandentalacademy.com

Cervical loop
Heartwig’s epithelial root sheath and
forming root

Break up of dental lamina and crown pattern determination during Bell
stage: two events
• The dental lamina joining tooth germ to oral epithelium breaks up in to
discrete islands.
• IEE folds because of differential mitotic activity and thus the shape of future
crown pattern can be recognized.
• The point of maturation of cells determines site of future cusp developments.
• The determination of shape of the tooth is emphasized by following:
– One proposes that factors responsible are present within ectomesenchyma
with distinct graded fields for each tooth family.
– Clone model; proposes that, each tooth class derived from
ectomesenchymal cells programmed by epithelium to produce teeth of
given pattern.

AMELOGENESIS
Two step process:
• 30% partially mineralized dentin formation.
• involves removal of organic matter and water with significant influx of
more than 96% mineral content.
• The enamel organ consist of 4 layers:
• Outer enamel epithelium – early stages single layer cuboidal cells.
– prior to enamel formation becomes irregular shaped with folds.
– during amelogenesis cells develop specialization for active transport of
materials.
• Stellate reticulum – star shaped cells.
• Functions :
• Buffering action against physical forces that might distort the developing
DEJ conformation.
• Permits limited flow of nutrients.

• Stratum intermedium – flat to cuboidal shape in one or
three layer, decrease in thickness after dentin formation.
• Function:
• Role in production of enamel by controlling fluid diffusion
in to and out of ameloblasts.
• Inner enamel epithelium.
• Cervical loop

LIFE CYCLY OF AMELOBLASTS
1) MARPHOGENIC STAGE
• Low columnar cells with large oval centrally located
nuclei, golgiapparatus, centrioles at proximal end of cell.
2) ORGANIZING STAGE
• Cells of inner enamel epithelium become toll columnar,
golgi apparatus, centrioles move to distal end nucleus
proximally with mitochondria .
• Junctional complexes determine what may or may not
enter into or out of ameloblasts.
• Nutritional supply to IEE after pre-dentin formation.
3) FORMATIVE STAGE
• Organogenesis & histo-differentiation .

4) MATURATION STAGE:
• Occurs after most of enamel matrix has been
formed
• starts at occlusal & incisal edges.
• Ameloblasts short columnar enamel matrix.
• Stratum intermedium ---spindal shaped
• Absorptive function indicated by microvilli &
cytoplasmic vacuoles.

5) PROTECTIVE STAGE.
• Stratified epithelial cells covering the formed enamel is
called reduced enamel epithelium.
• Protects the enamel by separating it from the connective
tissues of dental sac
6) DESMOLYTIC STAGE
The reduced enamel epithelium proliferate & induces
atrophy of connective tissues separating it from oral
epithelium so that fusion of two epithelia occurs,
elaborates enzymes, causes connective tissue desmolysis.

FORMATION OF ENAMEL MATRIX
• The ameloblasts secrete the enamel after a layer of predentin
formation .
• Aprismatic layer of enamel forms dentino enamel
membrane.
THE DEVELOPMENT OF TOME’S PROCESS
• The projection of ameloblasts into the enamel matrix are
termed as tome’s process .
• Cells contains typical secretory granules as well as rough
endoplasmic reticulum &mitocondria.
• Distal terminal bars.
• the ameloblasts show extensive golgi complex with rough
endoplasmic reticulum occupying supra nuclear
compartments.

• Identified by the presence of abundant membrane in
foldings. The secretions of these sites along with adjacent
ameloblasts results in formation of enamel partitions that
delimit a pit with tome’s process thus inter rod enamel is
found.
• Second site one face of distal portion of tome’s process
fills pits with matrix.so rod enamel formed.
• The narrow space between rod an inter-rod by squeezing
out tome’s process, is filled with organic material called as
rod-sheath.
• In the outer third of enamel rods have slightly different
profile an rectilinear trajectory because of distal portion
orientation to cell body.
• Final few increments are aprismatic enamel.

3) MATURATION STAGE
Transitional phase
• Ameloblasts undergo morphologic changes for
maturing enamel; involves reduction in height
,decrease in volume & organelle content.
• Absorptive cell morphology ;villous surface
&cells with mitochondria.

Maturation Proper
• Ameloblasts are involved in removal of organic matrix
&water content of enamel matrix.
• Ruffled ended ameloblasts show proximal leaky junction
&tight distal. Pumping action of calcium into enamel
matrix is produced by membrane associated with calcium
adenosinetriphosphatase.
• Smoothened cells show distal junctions that is leaky and
proximal tight. It leaks out small proteins and other
molecules.
• Removal of organic matrix is attributed to degrading
enzymes, polypeptide fragments leave enamel through
leaky distal junction of smoothened cell.www.indiandentalacademy.com

MINERALIZATION AND MATURAION OF ENAMEL MATRIX.
Two stages:
• First stage immediate partial mineralization occurs
in matrix segment and interprismatic substance in
the form of crystalline apatite. Comprises about
25% to 30% of total mineral content.
• Second stage / maturation – characterized by
gradual completion of mineralization.
– It is a integration of two processes
– Ultra structural level shows
• Maturation is characterized by growth of crystals
• The original ribbon shaped crystals increase in
thickness more rapidly than in width.
• Organic matrix becomes thin and provides room for
growing crystals.www.indiandentalacademy.com

Dentinogenesis and
amelogenesis
Amelogenesis

DENTINOGENESIS
Formation of odontoblasts
• The odontoblasts are tall columnar cells with increased
protein synthesizing organelles and centrally located
nuclei.
• Cells are 40 µm in length and 7 µm in width.
• Proline appears in rough endoplasmic reticulum and golgi
apparatus and migrates into cell processes in dense
granules, which are emptied into extra cellular collagenous
matrix of predentin.

FORMATION OF MANTLE DENTIN
• The odontoblasts deposit first dentin collagen in to ground
substance.
• The type III collagen fibers with fibronectin called
VonKorff’s fibers.
• Odontoblast continue to increase in size and produce type I
collagen fibrils orient parallel to future DEJ.
• Dentinal tubules enclose several cell processes of
odontoblasts.
• Predentin is formed along pulpal borders remains for one
day before calcification and next layer of dentin formation.
• Initially 4 µm of dentin is formed, slows to 1 µm per day
after teeth erupts and moves into occlusion and decrease
further after root development.
• Reparative dentin may form at a 4 µm per day rate for
several days after tooth is restored.

MINERALIZATION
• The earliest crystal deposition is in the form of very fine
plates of hydroxy apatite on the surface of collagen and
ground substance.
• The crystals are arranged with their long axis paralleling
the fibril axis and in rows conforming into 64nm striation
pattern.
• Within globular islands of mineralization crystal
deposition appears to take place radially from common
centers in a so called spherulite form.
• Two patterns of mineralization ie globular & linear
calcification

• Mineralization is achieved by continuos deposition of
mineral .initialy in the matrix vesicle &then at
mineralization front.
• Calcospherite mineralization is occasionally seen along
pulp al predentin .
• The peritubular dentin is highly mineralized.
• The ultimate crystal size 3nm in thickness &100nm in
length.
• Root Dentin:less degree of mineralization ,phosphoryn
content is less.
• Secondary &Tertiary Dentin
• Neonatal Line www.indiandentalacademy.com

Bell stage of tooth development both
dentinogenesis and amelogenesis
Dentinogenesis

CEMENTO GENESIS:
• Cementoblast formation
• Cementoblast cell structure shows secretary
organelles.
• The uncalcified matrix is called cementoid .
• Cementum formation occurs in rhythmic
process.

Mineralization of Cementum:
• Mineralization occurs after some cementum
matrix is laid down.
• The calcium&phosphate ions from tissue fluid are
deposited & arranged as unit of hydroxy apatite .
• Cellular –cementum present in apical half of root.
• A cellular cementum in coronal half of root.
• The cementoid layer observed over mineralizing
cementum..
• Sharpey’s fibers.www.indiandentalacademy.com

• Pulp tissue originates from dental papilla which
determines whether the tooth is incisor or molar.
• At about 8th
week of embryonic life dental pulp
development begins at future incisor location.later
on more posterior tooth.
• Young dental papilla shows organized vascular
network by the time dentin formation begins.
• Differentiation of fibroblasts & odonto blasts.
• Large myelinated nerves following blood vessels
enter into pulp&pulp organization begins.
DEVELOPMENT OF PULP

Maturing pulp

DEVELOPMENT OF PERIODONTAL LIGAMENT
• Develops from cells of dental follicle
• Cells of dental follicle differentiate into cementoblasts,
fibroblasts, osteoblasts.
• The formation of periodontal ligament occurs after
completion of root dentin & cementum.
• The fibers of periodontal ligament are embedded in
cementum of tooth&alveolar bone&orient in characteristic
fashion after tooth eruption.

Factors affecting growth&development
broadly classified as
1. Genetic:
i. Inherited
ii. Mutagenic
2. Environmental Factors:
a. Infections :
i. Systemic:
- Rudella
- Influenza
o ii. Local: periapical infection
affecting deciduous tooth

b. Exanthematous diseases: measles ,chickenpox ,scarlet fever.
c. Physical injuries: trauma , radiation,extra temperature.
d. Hormonal disturbances: parathyroid ,thyroid ,growth
hormone, pituitary hormone .
e. Nutritional deficiency : vitamin A,Vit B complex Vit C,Vit
D, proteins, aminoacides.
f. Hypocalcemia
g. Birth injury-premature birth ,traumatic birth,RH hemolytic
disease.
h. Congenital syphilis:
i. Ingestion of chemicals
j. Idiopathic
k. Miscellaneous drugs & chemicals:teratogenic
l. Maternal disease & defects
m. Embryonic defectswww.indiandentalacademy.com

DEVELOPMENTAL DISTURBANCES OF TEETH & PROSTHODONTIC
CONSIDERATIONS
1) Amelogenesis imperfecta / hereditary enamel dysplasia
/heriditary brown enamel/heriditary brown opalescent teeth.
Classification; by witkop sauk

Hypoplastictype-1.Pitted autosomal dominant
2.Local autosomal dominant
3.Smooth autosomal dominant
4.Rough autosomal dominant
5.Rough autosomal recessive
6.Smooth x-linked dominant
Hypocalcified-- a) Autosomal dominant
b) Autosomal recessive
Hypomaturation-a) Autosomal dominant with tarodontism
b) X-linked recessive
c) Pigmented autosomal recessive
d) Snow capped teeth

Clinically;
• Hypoplastic type shows enamel not formed to full
thikness
• Hypocalcified Soft enamel
• Hypomaturation enamel can be chipped away
• Discoloration from yellow to dark brown

Prosthodontic consideration:
• Full crown restoration.

2) Environmental enamel hypoplasia:
– Defective organic enamel matrix
– Both dentitions,both enamel&dentin may be involved .
– Effect of an injury ameloblasts.
*Conditions--
A.Nutritional deficiency
B.Exanthemetous disease
– Both the conditions show pitting of enamel
– Prosthodontic consideration:
– Full crown restoration
C.congenital syphilis www.indiandentalacademy.com

Clinical features:
Prosthodontic consideration: full crown restoration,
veneering.
D. Enamel hypoplasia –decreased calcium level in the blood.
Clinical features
Prosthodontic considerations
E. Enamel hypoplasia birth injury
F. Enamel hypoplasia due to trauma or infection
Clinical features - Turner’s hypoplasia
Prosthodontic considerations
G. Fluoride ingestion mottled enamel
Clinical features : White flecks,opaque areas,pitting brown
stains,corroded appearance.
Prosthodontic considerationswww.indiandentalacademy.com

Dentinogenesis imperfecta/Hereditary opalescent dentin
Shields & co-workers classified as –
a.Type I- occurs with osteogenesis imperfecta
– Autosomal dominant
– Desiduous teeth severly affected
– Discoloration of teeth
– Short blunt roots
b.Type II-not associated with OI
- Autosomal dominant
- Radio graphs show obliterated pulp chamber
c.Type III- Brandy wine type
Multiple pulp exposures in deciduous teeth
• Shell teeth
• Prosthodontic considerationswww.indiandentalacademy.com

Dentin dysplasia(root less teeth):atypical dentin,abnormal
pulp
a. Type I-radicular
• Delayed eruption,extreme mobility short roots
• Prosthodontic considerations
b.Type II-coronal
In deciduous teeth obliterated pulp chamber. In
permanent thistle tube shaped.

Regional odonto dysplasiaGhost teeth
clinically delay or failure to erupt irregular
appearance of teeth.
Prosthodontic consideration fabrication of
restorations

Developmental disturbances in size
1) Microdontia
• True generalized-pituitary dwarfism
• Relatively generalized
• Single tooth
2) Macro dontia
Developmental disturbances in shape of the
tooth
1) Gemination
An attempt at division of single tooth germ by
invagination resulting in incomplete formation
of two teeth
2)Fusion
Union of two developing tooth germwww.indiandentalacademy.com

3) Concrescence fusion of teeth after root
formation
4) Dilacerations
5) Dens in dent : an invagination in the
surface of crown before calcification
6) Dens evagination
7) Taurodontism
Klinefelter syndrome males with extra
x-chromosome in sex chromosome .
8) Talon cusp
Prevalent in persons with Rubinstein-
taybi syndrome
9) Supernumerary roots

1) Number of Teeth
Anodontia
• Congenital absence
– Total Anodontia-
hereditaryectodermal dysplasia
– Partial Anodontia

2) Supernumerary teeth
• Gardener’s syndrome

Prosthodontic Considerations
• During crown preparation patient may complain about sensitivity
because of exposed dentin and there may be requirement of
provisional restoration before permanent prosthesis is fabricated
and cemented to avoid discomfort to the patient because of
exposed dentinal sensitivity.
• Cementum resorption can occur because of trauma or excessive
occlusal forces. In severe cases resorption may continue in dentin.
Followed by repair by forming an cementum I.e. anatomical or
functional.
• Under excessive occlusal stresses there will be hypercementosis.
• The periodontal ligament tissue of a tooth which was out of
function for a long time, will take time to adapt to new functional
demands, this applies to bridge abutments, teeth opposing bridges
or dentures.

Summary & Conclusion:
• Tooth development occurs in following
stage Bud stage, cap stage, Bell stage

References
• Orban’s oral histology &embryology
• Ten cate’s oral histology
• essentials of oral pathology&oral medicine by
R.A.Cowson.E.N.Odell 7th
edition
• Color atlas of oral pathology 4th
edition by Hamiltan
B.G.Robbinson;Arthur,S.Miller.
• Color atlas of clinical oral pathology by
Blad.W.Neville,Douglas D.damm,Deank-white 2nd
edition
• Text book of oral pathology by Shafer 4th
edition.
• Permar’s Oral Embryology and Microscopic Anatomy –
eighth edition, Rudy C. Melfi.

Thank you

Growth and development of tooth/ oral surgery courses

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