GOOD MORNING
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com

www.indiandentalacad...
Poet OGDEN NASH
must have known the
suffering
when he penned the
words ,
”..some tortures are
physical and some are
mental...
EVOLUTION . . .
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Evolutionary Concept
During evolution several significant changes
took place in the jaws and teeth. When the
reptilian evo...
Stages of tooth evolution
Graphically there are four stages of tooth
development:
 The reptilian stage (HAPLODONT)
 Earl...
…move towards future…the MAN.

The REPTILIAN stage

There is no occlusion. prehension both jaws single
Teeth mainly byco...
Early mammalian (triconodont)
Not

seen now except a few breeds of dogs
and other carnivores.
Exhibits

three
cusps in l...
Largest
cusp is in
middle,with
smaller cusp
anteriorly
and
posteriorly.


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Occlusion absent

tiger

Tritubercular (triangular)stage




According to some theories the triconodont
line of three ch...
HELLLO…..frens !!! meet other members of my FAMILY…..

Quadritubercular stage

During next stage of accommodation to the c...
Hi..myself GIBBON

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HA…HA…HAAA !!!

we are… GORILLAS’

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HELLO….myself MONKEY

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DON’T run..I am

ORANGUTAN

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The shapes of individual teeth in these animals are
very close to their counterparts in HUMAN MOUTH.

NOTE the TEETH in OC...
Characteristics of DENTITION
The teeth of the vertebrates are characterized
depending upon :
MODE

OF ATTACHMENT

ACRODO...
Depending on the NUMBER OF SUCCESSIVE
SET
POLYPHYODONT : teeth replaced throughout life .
ex:

SHARK TEETH

SHARK

…so be...
Depending on the NUMBER OF SUCCESSIVE SET
DIPHYODONT : two sets of teeth.
Ex:

HUMAN BEING
PRIMARY DENTITION

Step furthe...
so care for your TEETH…..
and SMILE

…..or BETTER choose yourself

PERMANENT DENTITION
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Depending on the NUMBER OF SUCCESSIVE SET
MONOPHYODONT

: one set of teeth .

SHEEP and
GOAT
Ex.

GOAT

SHEEP
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TYPE

or SHAPE OF TEETH

HOMODONT

: a single type of teeth

HETRODONT

: having various type of
teeth . Ex. Human bein...
ORIGIN OF TEETH


THEORY OF CONCRESCENCE




THEORY OF TRITUBERCULY






The mammalian dentition was produced by th...
Development of TOOTH

Dr. Raj Kumar Jaiswal

www.indiandentalacademy.com
CONTENTS














PRIMARY EPITHELIAL BAND
VESTIBULAR LAMINA
DENTAL LAMINA
BUD STAGE
CAP STAGE
Enamel Knot
E...




Development of TOOTH involves many
BIOLOGICAL PROCESS including
EPITHELIAL MESENCHYMAL relationship
Morphogenesis
F...
WHAT IS
ECTOMESENCHYME?


When the histology of primitive Oral cavity is
Examined ,it can be seen to be lined by
primitiv...
Primary Epithelial Band





After 37th day of development, continuous
band of epithelium forms around the mouth
from t...
Primary Epithelial Band
Vestibular Lamina

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Dental Lamina
Vestibular Lamina




Vestibule forms as a result of proliferation of
vestibular lamina into the ectomesenchyme.
Its cel...
Dental Lamina


Within the Lamina itself continued and
localized proliferative activity leads to
formation of series of E...
Bud Stage






First epithelial incursion into the
ectomesenchyme of jaw.
Simultaneous with the differentiation of eac...
BUD STAGE

TOOTH BUD and
DENTAL LAMINA

EIGHT WEEK
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CAP STAGE
ENAMEL
ORGAN

TENTH WEEK
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BELL STAGE
ENAMEL ORGAN
of DECIDUOUS
TEETH
PRIMORDUM of
PERMANENT
TOOTH

About 4
MONTHS

PRIMORDIUM of
FIRST
PERMANENT
MOL...








Enamel organ (dental organ)

Consists of:
 Peripherally located low columnar cells.
 Centrally located polyg...
Enamel Organ(dental organ)

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Condensed Ectomesenchyme


Immediately subjacent to enamel organ
known as DENTAL PAPILLA





That surrounds tooth bud...
Tooth Germ

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Cap stage(proliferation)




Tooth bud continues to proliferate BUT not
expand uniformly.
Unequal growth in different p...


Stellate reticulum (Enamel pulp)





Polygonal cells in center of epithelial
enamel organ between inner enamel
epit...
CAP STAGE
Oral Epithelium

Dental Lamina
Tongue
Tooth Germ
Meckel’s Cartilage
Lip
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ENAMEL CORD

DENTAL LAMINA
PERMANENT TOOTH BUD
ENAMEL CORD or SEPTUM
DENTAL PAPILLA

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ENAMEL NICHE

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ENAMEL KNOT
The cells in the center of the ENAMEL ORGAN
are densely packed and form ENAMEL KNOT.

ENAMEL CORD

A vertical ...
Bell stage(Histodifferentiation
& Morphodifferentiation)


As the invagination of epithelium deepens & the
margin continu...


AMELOBLASTS
 Attached to one another by JUNCTIONAL
COMPLEX.
 Attached to cells of stratum intermedium by
DESMOSOME.
...


Stratum intermedium







Between the Inner Enamel Epithelium & newly
differentiated stellete reticulum the epithe...


Stellate reticulum






Expand further due to accumulation of
intercellular fluid.
Before enamel formation begins ,...
Stellate Reticulum
Accumulation of intercellular fluid

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Collapsed


Outer enamel epithelium





Cells flatten to low cuboidal form.
At the end of bell stage and preparatory
to formati...


Dental lamina


In all teeth except permanent molars the
dental lamina proliferates at its deep end
to give rise to en...


Dental papilla







Enclosed in invaginated portion of enamel
organ.
Before inner enamel epithelium produce
ename...


Dental sac




Before formation of dental tissue begins,
dental sac shows circular arrangement of
its fibers and rese...
BELL STAGE
Gland of Serres
Oral Epithelium
Dental Lamina
Stellate Reticulum
Bud for Permanent Tooth
External Enamel Epithe...
INITIAL

A B D DP
DF
E EO
O N HS

BELL
STAGES
STAGE

ADVANCE STAGES

AMELOBLAST
BONE
DENTINE
- DENTAL PAPILLA
- DENTAL FOL...
Advanced Bell Stage


The boundary between the inner enamel
epithelium and odontoblasts outlines future
dentino-enamel ju...
ADVANCED BELL
STAGE
Oral Epithelium
Inner Enamel Epithelium
Enamel and Dentin
formation starting at
Cusp tip
Dental
Papill...
…magnified view showing HARD

TISSUE FORMATION

AMELOBLASTS

ENAMEL

STRATUM
INTERMEDIUM

STELLATE
RETICULUM
PRE DENTIN

D...
COLUMNAR AMELOBLASTS
ENAMEL MATRIX
MINERALIZING DENTINE
PREDENTINE
ODONTOBLASTS
FIBROBLASTS OF PULP
HERTWIG’s ROOT SHEATH
...
Hertwig’s Epithelial Root Sheath
and Root Formation
Root development begins after enamel and
dentin formation has reached ...
EPITHELIAL DIAPHRAGM AND PROLIFERATION ZONE OF PUL

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ELONGATION
of HERS
CORONAL to
EPITHELIAL
DIAPHRAGM

ROOT
SHEATH
BROKEN

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

Prior to beginning of root formation , root
sheath forms EPITHELIAL DIAPHRAGM








The outer and inner enamel ep...
ROOT FORMATION

INITIAL STAGES

CERVICAL LOOP

MIDWAY

FINAL STAGE

APICAL FORAMEN
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At the same time the connective tissue of Dental sac
surrounding the root sheath proliferates and invades
continuous Doubl...


In multi-rooted teeth:









Differential growth of epithelial diaphragm causes
division of the root trunk in ...
During of growth of TOOTH GERM…

EPITHELIAL
DIAPHRAGM HORIZONTAL EPITHELIAL FLAPS
PROLIFERAT and UNITE
EXPAND
ECCENTRICALL...
FORMATION IN PROGRESS
as a result
BEGINNING OF
ROOT ELONGATION OCCURS
DENTIN
FORMATION AT
BIFURCATION

MESIAL

DISTAL

DEV...
Initiation
Specific cell of dental lamina have potential to
form enamel (dental) organ. Different teeth at
different time/...
LACK of INITIATION results in:

ABSENCE of either SINGLE TOOTH or MULTIPLE TEETH
LEADING TO CROSS BITE
DECIDUOUS DENTITION...
SUBMERGING LOWER 2 nd
MOLAR
Due to
CONGENITAL ABSENCE
PERMANENT 2 nd
PREMOLARS

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OLIGODONTIA

IMPEDES THE
DEVELOPMENT
OF ARCH
Missing teeth

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ABNORMAL INITIATION results in :
Development of
SINGLE or MULTIPLE SUPERNUMERARY teeth
CLIEDOCRANIAL DYSPLASIA
MESIODENS

...
Proliferation
Enhanced proliferative activity ensues at point
of initiation and results in the BUD,CAP, and
BELL stages of...
Histodifferentiation
The cells become restricted in their functions.
They differentiate and give up their capacity
to mult...
DISTURBANCES during this stage may lead to…
AMELOGENESIS IMPERFECTA : Hypoplastic type
AMELOGENESIS IMPERFECTA : Hypominer...
Morphodifferentiation

The morphologic pattern,or basic form and relative size
of the future tooth,is established by
morph...
Disturbances may effect the FORM and SIZE of the
tooth WITHOUT impairing the function of ameloblasts
and odontoblasts.
MIC...
Apposition
Apposition is the deposition of the MATRIX of
the hard dental structures.
Appositional growth of enamel and den...
Factors affecting DEVELOPMENT


Systemic factors


ACCELERATING EFFECT :on the

whole very rare but reported to be due t...


RETARDING AFFECT : more common in
permanent dentition due to
 Hypo thyroidism
 Hypo pitutarism
 Cleidocranial dysost...
Eruption of Tooth and
Theories of
eruption

Dr. Raj Kumar Jaiswal

www.indiandentalacademy.com
Eruption



Latin – ‘erumpere’ – to break out.
Properly refers/understood to mean the
axial or occlusal movement of the ...
Theories of Eruption
Tooth eruption is an essential process for the
survival of many different species and although
the mo...
Most talked about theories are:
 Root formation(elongation)theory
 Bone remodeling theory
 Vascular pressure theory
 P...
Root formation theory
In 1978 HUNTER attributed to mechanism of root
elongation
 Root

formation follows crown formation ...
BUT….

www.indiandentalacademy.com
Bone

at the base of socket cannot act as a
fixed base because pressure on bone results
in its resorption.
Some teeth mo...
STOPPED

BONE
TOOTH GERM

BONE

OCCLUSAL MOVEMENT
OF CROWN

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BONE RESORPTION
Advocates of root formation theory like a
postulated existence of “Cushion Hammock
Ligament”straddling the base of the soc...
Bone remodeling theory
Is

important to permit tooth movement.
In animals that exhibit genetic deficiency of
OSTEOBLAST ...
These experiment establish ABSOLUTE
requirement for DENTAL FOLLICLE to achieve:
Bony remodelling and tooth eruption.
Pro...
These growth factors seem to Chemoattaract
monocytes from the peripheral bood vessels
around the dental follicle.
Resorpti...
Factors influencing tooth to erupt Intraosseously:
 Density of bone.
 Rate of bone resorption.
 The overlying tissue
Bo...
Vascular pressure theory

CONSTANT suggested that blood pressure
provided the eruptive force but there has been
evidence f...
Could the
VASCULATURE be
source of ERUPTIVE
FORCE…???

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There is close relationship between Osmotic tissue
fluid pressure and Blood pressure.
 NESS and SMALE suggested that the ...




The Pulsatile nature of blood flow within the
follicle and periodontal ligament and its
significance for tooth erupt...
Tooth develop,erupt and function in a vascular
site constantly exposed to PULSATIVE
forces arising from blood flow.
Repeta...
BUT…..
Even the resection of root and thus the
vasculature CANNOT prevent the
eruption of tooth.

www.indiandentalacademy....
Periodontal ligament traction theory
The eruptive movement could be brought about a
combination of events envolving a forc...
The removal of bone to create eruptive pathway is
also dictated by the tissues surrounding the
tooth.
Evidence to support ...




Drugs that interrupt proper collagen
formation in ligament also interfere with
eruption.
Tissue culture experiment h...
PERIODONTAL LIGAMENT
Before CONTRACTION
ORAL MUCOSA

After CONTRACTION

BONE

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Pulp theory
This theory suggests that a propulsive force is
generated by extrusion of pulp through
THREE mechanisms.


...
Here in first stage ,
There is growth of dentine.
This causes interstitial growth of the pulp tissue
VASCULAR SYSTEM DEVEL...
BUT……
HERZBERG and SCHOUR removed
the PULP of RODENTS incisors and found
that
its eruption rates were UNAFFECTED.

www.ind...
Genetic input theory
If tooth eruption is to be explained at the
cellular and molecular level ,a degree of
genetic control...
A classification of these relationships has been
represented by SANK.
 Inherited defects : amelogenesis imperfecta
 Diso...
Although variety of theories have attempted to
identify the eruptive force , none been fully
supported by experimental evi...
Mechanics of eruption
When a tooth starts to erupt there is change in
its momentum , therefore a force MUST be
present.
 ...
Calcification the crown provides a new mass against
which the force within the follicle can act.
Although the action force...
In order for a tooth to
the tooth erupts the
dynamic relationships between move the action of
the surrounding alveolar bo...
On emergence the resistance is greatly reduced
resulting in accelerated rate of eruption until
a new equilibrium of forces...
Shedding of deciduous teeth
The physiologic process resulting in
elimination of the deciduous dentition is
called SHEDDING...
Physiologic tooth movement
Is described as :
 Pre-eruptive tooth movement
 Eruptive tooth movement
 Post eruptive tooth...
Pre-eruptive tooth movement
When deciduous tooth germ first differentiate
they are extremely small and there is a good
dea...


This crowding is gradually alleviated by the
lengthening of the jaws , which permits the 2nd
deciduous molar tooth germ...
INCISOR and CANINE
 Eventually come to occupy a position in their
own bony crypt on lingual surface of their
deciduous.
P...
ERUPTING INCISOR

DECIDUOUS INCISOR

BONE BETWEEN DECIDUOUS
TOOTH
AND SUCCESSOR
ENAMEL OF PERMANENT INCISOR
DENTIN

www.in...
ERUPTING INCISOR
ENAMEL DISSOLVED AWAY

DENTIN

GINGIVA
PULP

FOLLICLE
ENAMEL SPACE
REDUCED ENAMEL
EPITHELIUM
ALVEOLAR BON...
ERUPTING CANINE

DECIDUOUS CANINE

RESORPTION

RESORPTION OF ROOT

RERSORPTION OF BONE

PERMANENT CANINE

www.indiandental...
ERUPTING PREMOLAR
DECIDUOUS FIRST MOLAR

ROOT RESORPTION
PERMANENT TOOTH GERM

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PERMANENT MOLAR tooth germ


No predecessors , develop from backward
extension of the dental lamina as there is little
sp...
OCCLUSAL surface facing DISTALLY,and can
swing into position

MAXILLA
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PERMANENT MOLAR develop with
their axis showing MESIAL
inclination , VERTICAL later.

MANDIBLE
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ERUPTION OF MOLAR
At 6 to 7 years
At 4 years 6 months

Perm.FIRST MOLAR at 3 years

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EXFOLIATED

DECIDUOUS CANINE

DECIDUOUS MOLAR

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Pre eruptive movements of both deciduous and
permanent tooth germs are best thought of as
the movement required to place t...
Histology
As pre eruptive tooth movements occurs in a
intraosseous location , such movement is
reflected in the patterns o...
Eruptive tooth movement
During this phase the tooth movement from
its position within the bone of the jaw to
the functiona...
HISTOLOGY
Significant developmental event associated with the
eruptive tooth movement are:
 Formation of roots
 Periodon...
The architecture of tissue in advance of erupting
successional teeth from that found in advance of
deciduous teeth.
The fi...
GUBERNACULAR CORD

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“in dried skull holes can be identified in jaw on the
lingual surface of the deciduous teeth”
These holes which once conta...
GUBERNACULAR CANALS

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

Once erupting tooth appears in the oral cavity its
subjected to environmental factor that help to
determine its positio...
Post eruptive tooth movement
These are those movements made by the tooth
after it has reached its functional position in t...
Movement made to accommodate the
Growing Jaws


These are completed toward the end of 2nd
decade when jaw growth ceases.
...






Seen histologically as readjustment of the
position of the tooth socket achieved by
formation of new bone at alve...
Compensation for OCCLUSAL
wear




Is often stated that it is achieved by continued
cementum deposition around apex of t...
OCCLUSAL PLANE

DEPOSITION of CEMENTUM

ALVEOLAR BONE

ATTRITION

COMPENSATION OF OCCLUSAL
WEAR
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Accommodation for INTERPROXIMAL wear
Wear also occurs at the contact points between
teeth and their proximal surfaces.
Thi...
APPOSITION
RESORPTION

MESIAL DRIFT
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Anterior component of force :

When teeth are brought in contact ,ex:when jaws
are clenched , a forwardly force is generat...
Billiard ball analogy
“…if the two touching balls are in line with the
pocket , no matter how the first ball is struck
sec...
BILLIARD BALL ANALOGY

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Cuspal inclination is a significant factor which
can be demonstrated by selectively grinding cusp
in such a way as to eith...
Contraction of Transseptal
ligament
The periodontal ligament are important in maintaining
tooth position. It is suggested ...
OCCLUSAL PLANE
TRANSSEPTAL FIBRES

ACTION of

FIBRES

TRANSSEPTAL
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

The approximal contacts are disked , teeth
move to reestablish contact ,however if the
teeth is also ground out of occl...
Soft tissue pressure
The pressure generated by cheeks and tongue may
push teeth mesially. However if such pressure
from so...
TYPES OF ERUPTION
Three distinct type of teeth are differentiated by their
eruption pattern :
 CONTINUOUSLY GROWING
 Too...
CONTINUOUSLY EXTRUDING
Teeth stop forming once root formation is
SHEEP
CATTLE
complete.
 Well defined crown and root.
 M...
CONTINUOUSLY INVESTED TEETH
Human teeth belong to this type of eruption.
 Teeth stop forming after predictable amount of
...
ERUPTION RHYTHM
The

circadian rhythm in eruption is potentially
significant in clinical practice.
 The teeth intrude tr...
CLINICAL SIGNIFICANCE


Timing of eruption


Controlling intervention
 Excessive eruption of posterior teeth is a
major...


Teeth erupt primarily during night with
little or no net eruption during the day , it
is quite possible that wearing th...


Daily rhythm in skeletal growth


Skeletal growth requires an adequate levels
of HGH which increases in the night.
 T...
TEETHING
Teething is a term limited by common usage to
eruption of primary dentition which ususally begins
in fifth or six...
Clinical features of TEETHING


LOCAL SIGNS
 Hypermia or swelling of the mucosa
overlying the erupting teeth.
 Patches ...
TEETHING
www.indiandentalacademy.com


SYSTEMIC SIGNS








General irritability and crying.
loss of appetite.
Sleeplessness , restlessness
Increased...
Associated problems


SYSTEMIC




Fever
Diarrhea
Vomiting

LOCAL
Eruption

hematoma

Eruption

sequestrum

Ectopi...
REMNANTS OF ROOTS OF FIRST MOLAR

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PERMANENT CANINE
Causing resorption of
DECIDUOUS LATERAL INCISO
and CANINE

MISSING PERMANENT
LATERL INCISOR
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IMPACTED CANINE
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Deciduous
INCISORS

Perm. CANINE

TRANSPOSITION
www.indiandentalacademy.com
LOCAL FACTORS














Aberrant tooth position
Lack of space in arch
Very early loss of predecessor
Ectop...
…lastly the books


ORAL HISTOLOGY









Tencate
Orban

Dental Anatomy,Physiology and Occlusion
-Wheeler’s
Text b...
THANK YOU…
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Tooth development and eruption /certified fixed orthodontic courses by Indian dental academy

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The Indian Dental Academy is the Leader in

continuing dental education , training dentists

in all aspects of dentistry and offering a wide

range of dental certified courses in different

formats.

Indian dental academy provides dental crown &

Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit

www.indiandentalacademy.com ,or call
0091-9248678078

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  • 8 weeks :BUD stage ,10 weeks :CAP stage ,4months BELL stage
  • Trichome stain for dental lamina
  • Tooth development and eruption /certified fixed orthodontic courses by Indian dental academy

    1. 1. GOOD MORNING INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.com
    2. 2. Poet OGDEN NASH must have known the suffering when he penned the words , ”..some tortures are physical and some are mental , But the one that is both is DENTAL…!!! ” www.indiandentalacademy.com
    3. 3. EVOLUTION . . . www.indiandentalacademy.com
    4. 4. Evolutionary Concept During evolution several significant changes took place in the jaws and teeth. When the reptilian evolve to mammalian , the dentition went from “polyphydont ” (many set of teeth) to “diphydont ” (only two sets of teeth) and then to “homodent ” (all of same teeth) to “heterodent”(different types of teeth like incisors, canines , premolars and molars) . There also arose the necessity for the teeth and bones to develop somewhat synchronously in order that the function of occlusion could be facilitated. www.indiandentalacademy.com
    5. 5. Stages of tooth evolution Graphically there are four stages of tooth development:  The reptilian stage (HAPLODONT)  Early mammalian stage (TRICONODONT)  Triangular stage (TRITUBERCULAR MOLAR)  QUADRITUBERCULAR MOLAR www.indiandentalacademy.com
    6. 6. …move towards future…the MAN. The REPTILIAN stage There is no occlusion. prehension both jaws single Teeth mainly byconfined to simple or combat and  Dentition includes for Jaw movement simplest form of tooth , the that limits Represented used many teeth in hinge movement. procurement of jaw movement. food. cone. www.indiandentalacademy.com
    7. 7. Early mammalian (triconodont) Not seen now except a few breeds of dogs and other carnivores. Exhibits three cusps in line in the posterior teeth. www.indiandentalacademy.com
    8. 8. Largest cusp is in middle,with smaller cusp anteriorly and posteriorly.  www.indiandentalacademy.com
    9. 9. Occlusion absent tiger Tritubercular (triangular)stage   According to some theories the triconodont line of three changed to a three cornered shape , with the teeth still bypassing each other more or less when the jaw opened or closed. Usually seen in dogs and carnivores. cheetah www.indiandentalacademy.com
    10. 10. HELLLO…..frens !!! meet other members of my FAMILY….. Quadritubercular stage During next stage of accommodation to the changes inon It is thethe time as andevelopment created aof humans are the The animals with dentition similar to that projection triangularform and anatomy , the articulationantagonist of the the tooth form that finally occluded with the of the jaws anthropoid apes. opposing accordingly. changed jaw. www.indiandentalacademy.com
    11. 11. Hi..myself GIBBON www.indiandentalacademy.com
    12. 12. HA…HA…HAAA !!! we are… GORILLAS’ www.indiandentalacademy.com
    13. 13. HELLO….myself MONKEY www.indiandentalacademy.com
    14. 14. DON’T run..I am ORANGUTAN www.indiandentalacademy.com
    15. 15. The shapes of individual teeth in these animals are very close to their counterparts in HUMAN MOUTH. NOTE the TEETH in OCCLUSION SKULL of CHIMPANZEE www.indiandentalacademy.com
    16. 16. Characteristics of DENTITION The teeth of the vertebrates are characterized depending upon : MODE OF ATTACHMENT ACRODONT : teeth attached to the jaw by a connective tissue. PLEURODONT THECODONT socket. : teeth are set inside the jaw. : teeth are inserted in the bony www.indiandentalacademy.com
    17. 17. Depending on the NUMBER OF SUCCESSIVE SET POLYPHYODONT : teeth replaced throughout life . ex: SHARK TEETH SHARK …so better TAKE CARE www.indiandentalacademy.com
    18. 18. Depending on the NUMBER OF SUCCESSIVE SET DIPHYODONT : two sets of teeth. Ex: HUMAN BEING PRIMARY DENTITION Step further towards CIVILIZATION… www.indiandentalacademy.com
    19. 19. so care for your TEETH….. and SMILE …..or BETTER choose yourself PERMANENT DENTITION www.indiandentalacademy.com
    20. 20. Depending on the NUMBER OF SUCCESSIVE SET MONOPHYODONT : one set of teeth . SHEEP and GOAT Ex. GOAT SHEEP www.indiandentalacademy.com
    21. 21. TYPE or SHAPE OF TEETH HOMODONT : a single type of teeth HETRODONT : having various type of teeth . Ex. Human being www.indiandentalacademy.com
    22. 22. ORIGIN OF TEETH  THEORY OF CONCRESCENCE   THEORY OF TRITUBERCULY    The mammalian dentition was produced by the fusion of two or more primitive conical teeth and each tubercle with its corresponding root originated as a single tooth. Each of the mammalian teeth was derived from a single reptilian tooth by secondary differentiation of tubercles and roots. This theory is widely ACCEPTED. THEORY OF MULTITUBERCULY  The mammalian dentition is a result of reduction and condensation of primitive tuberculate teeth. www.indiandentalacademy.com
    23. 23. Development of TOOTH Dr. Raj Kumar Jaiswal www.indiandentalacademy.com
    24. 24. CONTENTS           PRIMARY EPITHELIAL BAND VESTIBULAR LAMINA DENTAL LAMINA BUD STAGE CAP STAGE Enamel Knot Enamel Cord Enamel Niche BELL STAGE Histodifferentiation and Morphodifferentiation Structure of TOOTH GERM DENTAL PAPILLA BREAK UP of Dental Lamina CROWN PATTERN Determination Formation of PERMANENT DENTITION Hard tissue formation / CROWN STAGE ROOT FORMATION FORMATION OF SUPPORTING TISSUE www.indiandentalacademy.com
    25. 25.    Development of TOOTH involves many BIOLOGICAL PROCESS including EPITHELIAL MESENCHYMAL relationship Morphogenesis Fibrillogenesis Mineralization www.indiandentalacademy.com
    26. 26. WHAT IS ECTOMESENCHYME?  When the histology of primitive Oral cavity is Examined ,it can be seen to be lined by primitive 2-3 layered epithelium covering an Embryonic Connective Tissue which because of its origin from Neural Crest is termed ECTOMESENCHYME. www.indiandentalacademy.com
    27. 27. Primary Epithelial Band    After 37th day of development, continuous band of epithelium forms around the mouth from the fusion of separate plates of thickened epithelium. Roughly ‘Horse Shoe’ shaped. Gives rise to Vestibular lamina. Dental lamina. www.indiandentalacademy.com
    28. 28. Primary Epithelial Band Vestibular Lamina www.indiandentalacademy.com Dental Lamina
    29. 29. Vestibular Lamina   Vestibule forms as a result of proliferation of vestibular lamina into the ectomesenchyme. Its cells rapidly enlarge and then degenerate to form CLEFT which becomes the vestibule between the cheek and tooth bearing area. www.indiandentalacademy.com
    30. 30. Dental Lamina  Within the Lamina itself continued and localized proliferative activity leads to formation of series of Epithelial Ingrowths into the Ectomesenchyme at sites corresponding to position of future DECIDUOUS TEETH. From THIS POINT development proceeds in three stages :  BUD stage  CAP stage  BELL stage www.indiandentalacademy.com
    31. 31. Bud Stage    First epithelial incursion into the ectomesenchyme of jaw. Simultaneous with the differentiation of each dental lamina round and ovoid swelling arise from basement membrane at ten different point, corresponding to future deciduous teeth. These are primordia of enamel organ ‘the tooth bud’ . www.indiandentalacademy.com
    32. 32. BUD STAGE TOOTH BUD and DENTAL LAMINA EIGHT WEEK www.indiandentalacademy.com
    33. 33. CAP STAGE ENAMEL ORGAN TENTH WEEK www.indiandentalacademy.com
    34. 34. BELL STAGE ENAMEL ORGAN of DECIDUOUS TEETH PRIMORDUM of PERMANENT TOOTH About 4 MONTHS PRIMORDIUM of FIRST PERMANENT MOLAR www.indiandentalacademy.com
    35. 35.     Enamel organ (dental organ) Consists of:  Peripherally located low columnar cells.  Centrally located polygonal cells. Functions of Dental organ  Determining shape of crown  Initiating dentin formation  Establishing dentinogingival junction  Forming enamel As a result of increased mitotic activity (of cells of tooth bud and surrounding mesenchyme)and migration of neural crest cell into the area. The ectomesenchymal cells surrounding tooth bud condense. www.indiandentalacademy.com
    36. 36. Enamel Organ(dental organ) www.indiandentalacademy.com
    37. 37. Condensed Ectomesenchyme  Immediately subjacent to enamel organ known as DENTAL PAPILLA    That surrounds tooth bud and dental papilla known as DENTAL SAC    Tooth pulp Dentin Cementum Periodontal ligament Dental organ,Dental Papilla and Dental follicle constitute TOOTH GERM www.indiandentalacademy.com
    38. 38. Tooth Germ www.indiandentalacademy.com
    39. 39. Cap stage(proliferation)    Tooth bud continues to proliferate BUT not expand uniformly. Unequal growth in different parts of tooth bud lead to cap stage. Outer enamel epithelium   Peripheral cells covering convexity are CUBOIDAL Inner enamel epithelium  Peripheral cells covering concavity are COLUMNAR www.indiandentalacademy.com
    40. 40.  Stellate reticulum (Enamel pulp)    Polygonal cells in center of epithelial enamel organ between inner enamel epithelium and outer enamel epithelium separate as intercellular fluid accumulate. Cells assume branched reticular network. Mucoid fluid rich in albumin.  Gives cushion like consistency may support and protect Enamel forming cells www.indiandentalacademy.com
    41. 41. CAP STAGE Oral Epithelium Dental Lamina Tongue Tooth Germ Meckel’s Cartilage Lip www.indiandentalacademy.com
    42. 42. ENAMEL CORD DENTAL LAMINA PERMANENT TOOTH BUD ENAMEL CORD or SEPTUM DENTAL PAPILLA www.indiandentalacademy.com
    43. 43. ENAMEL NICHE www.indiandentalacademy.com
    44. 44. ENAMEL KNOT The cells in the center of the ENAMEL ORGAN are densely packed and form ENAMEL KNOT. ENAMEL CORD A vertical extension of ENAMEL KNOT that arises in Increasing enamel organ. The FUNCTION of both may be to act as a reservoir of dividing cells for growing ENAMEL www.indiandentalacademy.com
    45. 45. Bell stage(Histodifferentiation & Morphodifferentiation)  As the invagination of epithelium deepens & the margin continues to grow the enamel organ assumes a bell shape.  Inner Enamel Epithelium  Consists of single layer of cell that differentiate prior to Amelogenesis into tall columnar cells called Ameloblasts. www.indiandentalacademy.com
    46. 46.  AMELOBLASTS  Attached to one another by JUNCTIONAL COMPLEX.  Attached to cells of stratum intermedium by DESMOSOME.  These exhert organizing influence on the underlying mesenchymal cells in dental papilla which later differentiate into ODONTOBLASTS.  High glycogen content. www.indiandentalacademy.com
    47. 47.  Stratum intermedium     Between the Inner Enamel Epithelium & newly differentiated stellete reticulum the epithelial cells differentiate into a layer of flattened(squamous) cells called stratum intermedium. High degree of metabolic activity. Absent in part of tooth germ that outlines the root portion of tooth but does not form enamel. Along the inner enamel epithelium both layer considered as single functional unit responsible for formation of enamel. www.indiandentalacademy.com
    48. 48.  Stellate reticulum    Expand further due to accumulation of intercellular fluid. Before enamel formation begins , stellate reticulum collapses reducing the distance between centrally located ameloblast and nutrient capillaries near outer enamel epithelium. Change begins at the height of the cusp or incisal edge and progress cervically. www.indiandentalacademy.com
    49. 49. Stellate Reticulum Accumulation of intercellular fluid www.indiandentalacademy.com Collapsed
    50. 50.  Outer enamel epithelium    Cells flatten to low cuboidal form. At the end of bell stage and preparatory to formation of enamel the formerly smooth surface is laid in folds. Between these folds the mesenchyme of dental sac forms papillae and thus provide rich nutritional supply for the intense metabolic activity of avascular enamel organ. www.indiandentalacademy.com
    51. 51.  Dental lamina  In all teeth except permanent molars the dental lamina proliferates at its deep end to give rise to enamel organ of permanent teeth. Distal extension www.indiandentalacademy.com
    52. 52.  Dental papilla     Enclosed in invaginated portion of enamel organ. Before inner enamel epithelium produce enamel the peripheral cells of mesenchymal dental papilla differentiate into odontoblasts under organizing influence of epithelium. First assume cuboidal form and later columnar and acquire specific potential to produce dentin. ‘Membrana preformativa’ – basement membrane that separates the enamel organ and dental papilla just prior to dentin formation. www.indiandentalacademy.com
    53. 53.  Dental sac   Before formation of dental tissue begins, dental sac shows circular arrangement of its fibers and resembles capsular structure. With development of root, fibers of dental sac differentiate into periodontal ligament fibers that become embedded in developing cementum and alveolar bone. www.indiandentalacademy.com
    54. 54. BELL STAGE Gland of Serres Oral Epithelium Dental Lamina Stellate Reticulum Bud for Permanent Tooth External Enamel Epithelium Dental Papilla Inner Enamel Epithelium www.indiandentalacademy.com
    55. 55. INITIAL A B D DP DF E EO O N HS BELL STAGES STAGE ADVANCE STAGES AMELOBLAST BONE DENTINE - DENTAL PAPILLA - DENTAL FOLLICLE ENAMEL - ENAMEL ORGAN ODONTOBLAST NECK OF TOOTH – HERTWIG ROOT SHEATH www.indiandentalacademy.com
    56. 56. Advanced Bell Stage  The boundary between the inner enamel epithelium and odontoblasts outlines future dentino-enamel junction and cervical portion of enamel organ give rise to epithelial root sheath of Hertwig. www.indiandentalacademy.com
    57. 57. ADVANCED BELL STAGE Oral Epithelium Inner Enamel Epithelium Enamel and Dentin formation starting at Cusp tip Dental Papilla Cervical Loop Alveolar Bone Nerve Bundle www.indiandentalacademy.com
    58. 58. …magnified view showing HARD TISSUE FORMATION AMELOBLASTS ENAMEL STRATUM INTERMEDIUM STELLATE RETICULUM PRE DENTIN DENTIN ODONTOBLASTS PULP www.indiandentalacademy.com
    59. 59. COLUMNAR AMELOBLASTS ENAMEL MATRIX MINERALIZING DENTINE PREDENTINE ODONTOBLASTS FIBROBLASTS OF PULP HERTWIG’s ROOT SHEATH VERTICAL SECTION through NECK of TOOTH www.indiandentalacademy.com
    60. 60. Hertwig’s Epithelial Root Sheath and Root Formation Root development begins after enamel and dentin formation has reached future cementoenamel junction. HERS is formed from enamel organ.  Molds the shape of root  Initiates dentin formation.  Consists of outer and inner enamel epithelium only. www.indiandentalacademy.com
    61. 61. EPITHELIAL DIAPHRAGM AND PROLIFERATION ZONE OF PUL www.indiandentalacademy.com
    62. 62. ELONGATION of HERS CORONAL to EPITHELIAL DIAPHRAGM ROOT SHEATH BROKEN www.indiandentalacademy.com
    63. 63.  Prior to beginning of root formation , root sheath forms EPITHELIAL DIAPHRAGM     The outer and inner enamel epithelium bend at future CEJ into a horizontal plane narrowing the wide cervical opening of the tooth germ. The proliferation of cells of epithelial diaphragm is accompanied by proliferation of cells of connective tissue of pulp which occurs in area adjacent to the diaphragm. The free end of the diaphragm does not grow into connective tissue but the epithelium proliferates coronal to the epithelial diaphragm. The differentiation of Odontoblast & formation of Dentin follow the lengthening of root sheath. www.indiandentalacademy.com
    64. 64. ROOT FORMATION INITIAL STAGES CERVICAL LOOP MIDWAY FINAL STAGE APICAL FORAMEN www.indiandentalacademy.com
    65. 65. At the same time the connective tissue of Dental sac surrounding the root sheath proliferates and invades continuous Double epithelial layer dividing it into network of epithelial strands.  Epithelium is moved away from the surface of dentin so that the connective tissue cells come into contact with the outer surface of the dentin and differentiate into cementoblast that deposit a layer of cementum onto the surface of dentin.  In last stages of root development the proliferation of the epithelium in the diaphragm lags behind that of the pulpal connective tissue. Wide apical foramen is reduced first to width of diaphragmatic opening itself and later is further narrowed by apposition of dentin and cementum to the apex of the root. www.indiandentalacademy.com
    66. 66.  In multi-rooted teeth:       Differential growth of epithelial diaphragm causes division of the root trunk in 2/3 roots. During the general growth of enamel organ the expansion of its cervical opening occurs in such a way that long tongue-like extension of horizontal diaphragm develops. Two extension in lower molars and three in upper. Before division of the root trunk occurs the free end of these horizontal epithelial flaps grow towards each other and fuse. The single coronal opening of the coronal enamel organ is than divided into two-three openings. On the pulpal surface of dividing epithelial bridges dentin formation starts and on the periphery of each opening root development follows in the same way as for singlewww.indiandentalacademy.com rooted teeth.
    67. 67. During of growth of TOOTH GERM… EPITHELIAL DIAPHRAGM HORIZONTAL EPITHELIAL FLAPS PROLIFERAT and UNITE EXPAND ECCENTRICALLY E www.indiandentalacademy.com
    68. 68. FORMATION IN PROGRESS as a result BEGINNING OF ROOT ELONGATION OCCURS DENTIN FORMATION AT BIFURCATION MESIAL DISTAL DEVELOPMENT OF TWO ROOTED TOOTH www.indiandentalacademy.com
    69. 69. Initiation Specific cell of dental lamina have potential to form enamel (dental) organ. Different teeth at different time/definite time. Initiation induction requires ECTOMESENCHYMAL-EPITHELIAL interaction. www.indiandentalacademy.com
    70. 70. LACK of INITIATION results in: ABSENCE of either SINGLE TOOTH or MULTIPLE TEETH LEADING TO CROSS BITE DECIDUOUS DENTITION PERMANENT DENTITION FLATTENING of ARCH MISSING LATERAL INCISORS PARTIAL ANODONTIA www.indiandentalacademy.com
    71. 71. SUBMERGING LOWER 2 nd MOLAR Due to CONGENITAL ABSENCE PERMANENT 2 nd PREMOLARS www.indiandentalacademy.com
    72. 72. OLIGODONTIA IMPEDES THE DEVELOPMENT OF ARCH Missing teeth www.indiandentalacademy.com
    73. 73. ABNORMAL INITIATION results in : Development of SINGLE or MULTIPLE SUPERNUMERARY teeth CLIEDOCRANIAL DYSPLASIA MESIODENS www.indiandentalacademy.com
    74. 74. Proliferation Enhanced proliferative activity ensues at point of initiation and results in the BUD,CAP, and BELL stages of development. Proliferative growth causes regular changes in the size and proportions of the growing tooth germ. www.indiandentalacademy.com
    75. 75. Histodifferentiation The cells become restricted in their functions. They differentiate and give up their capacity to multiply as they assume their new function ; this law governs all differentiating cells. This phase reaches its highest development in the BELL stage , just preceding the beginning of formation and apposition of DENTIN and ENAMEL. www.indiandentalacademy.com
    76. 76. DISTURBANCES during this stage may lead to… AMELOGENESIS IMPERFECTA : Hypoplastic type AMELOGENESIS IMPERFECTA : Hypomineralized type DENTOGENESIS IMPERFECTA AMELOGENESIS IMPERFECTA :Hypomature type SHORT Amber coloured tooth MARKED Attrition www.indiandentalacademy.com
    77. 77. Morphodifferentiation The morphologic pattern,or basic form and relative size of the future tooth,is established by morphodifferentiation,that is,by DIFFERENTIAL GROWTH. Morphodifferentiation therefore is IMPOSSIBLE without proliferation. The ADVANCED BELL stage marks not only active histodiferentiation but also an important stage of morphodifferentiation in the crown,outlining the future DENTINOENAMEL JUNCTION. The DENTINOENAMEL and CEMENTOENAMEL junctions which are different and characteristic for each type of tooth,act as BLUE-PRINT pattern. www.indiandentalacademy.com
    78. 78. Disturbances may effect the FORM and SIZE of the tooth WITHOUT impairing the function of ameloblasts and odontoblasts. MICRODONTIA MACRODONTIA of entire dentition in relation to basal bone MICRODONTIA Oversized LATERAL INCISORS MACRODONTIA of UPPER teeth in relation to basal bone PEG shaped LATERAL CONCRESCENCE: FUSION :union of the dentin GEMINATION :incomplete union of cellular TWINNING:complete division of two teeth,from two tooth division of of twotooth bud Cementum bud of one toothsingleto teeth,from buds. create two teeth two buds. www.indiandentalacademy.com
    79. 79. Apposition Apposition is the deposition of the MATRIX of the hard dental structures. Appositional growth of enamel and dentin is characterized by regular and rhythmic deposition of an extracellular matrix. It is the fulfillment of the plans outlined at the stages of Histodifferentiation and Morphodifferentiation. Both HYPOPLASIA and HYPOCALCIFICATION can occur as a result of an insult to this phase. www.indiandentalacademy.com
    80. 80. Factors affecting DEVELOPMENT  Systemic factors  ACCELERATING EFFECT :on the whole very rare but reported to be due to  Hyper thyroidism  Hyper pitutarism  Turner’s syndrome www.indiandentalacademy.com
    81. 81.  RETARDING AFFECT : more common in permanent dentition due to  Hypo thyroidism  Hypo pitutarism  Cleidocranial dysostosis  Down’s syndrome  Achondroplasia  Hypovitaminoses ( A and D)  Osteopetrosis www.indiandentalacademy.com
    82. 82. Eruption of Tooth and Theories of eruption Dr. Raj Kumar Jaiswal www.indiandentalacademy.com
    83. 83. Eruption   Latin – ‘erumpere’ – to break out. Properly refers/understood to mean the axial or occlusal movement of the tooth from its developmental position within the jaw to its functional position in the occlusal position. www.indiandentalacademy.com
    84. 84. Theories of Eruption Tooth eruption is an essential process for the survival of many different species and although the movement of teeth into function has been the subject of extensive research there is no consensus as to the mechanisms involved Mechanism that brings about tooth movement is still debatable and is likely to be a combination of number of factors. www.indiandentalacademy.com
    85. 85. Most talked about theories are:  Root formation(elongation)theory  Bone remodeling theory  Vascular pressure theory  Periodontal ligament traction theory  Pulp theory  Genetic input theory www.indiandentalacademy.com
    86. 86. Root formation theory In 1978 HUNTER attributed to mechanism of root elongation  Root formation follows crown formation and involves cellular proliferation of new tissue that must be accommodated by either movement of the crown of tooth or resorption of bone at the base of its socket. It is the former that actually happens , but if occlusal movement is prevented resorption of bone at the base of socket occurs. If root formation is to result in an eruptive force the apical growth of root needs to be translated into occlusal movement and requires the presence of a fixed base. www.indiandentalacademy.com
    87. 87. BUT…. www.indiandentalacademy.com
    88. 88. Bone at the base of socket cannot act as a fixed base because pressure on bone results in its resorption. Some teeth move a distance greater than the length of their roots. Eruption movement can occur after completion of root formation. Experimental resection preventing further root formation does not stop eruptive tooth movement. All indicating root formation CANNOT be responsible for eruptive tooth movement. www.indiandentalacademy.com
    89. 89. STOPPED BONE TOOTH GERM BONE OCCLUSAL MOVEMENT OF CROWN www.indiandentalacademy.com BONE RESORPTION
    90. 90. Advocates of root formation theory like a postulated existence of “Cushion Hammock Ligament”straddling the base of the socket from one bony wall to the other sling. Its function was to provide fixed base for growing root to react against… BUT …the structure described as cushion hammock ligament is Pulp delineating membrane that runs across apex of the tooth and has no bony insertion,it CANNOT act as FIXED BASE. www.indiandentalacademy.com
    91. 91. Bone remodeling theory Is important to permit tooth movement. In animals that exhibit genetic deficiency of OSTEOBLAST ,tooth eruption is prevented . If tooth germ is removed experimentally and dental follicle left intact an eruptive pathway is forms in overlying bone. Marks and Cahill have confirmed that tooth has no active role in the process , since metal or silicone replicas of calcified crowns , placed within follicle ,also erupts. www.indiandentalacademy.com
    92. 92. These experiment establish ABSOLUTE requirement for DENTAL FOLLICLE to achieve: Bony remodelling and tooth eruption. Provides the source for new bone forming cells and conduit for osteoclast derived from Monocyte through its vascular supply. RECENT STUDIES show that resorptive process may be regulated by local growth factors such as Transforming growth factor Beta-1(TGF-ß1)and Epidermal growth factor (EGF) produced within or around Dental follicle. www.indiandentalacademy.com
    93. 93. These growth factors seem to Chemoattaract monocytes from the peripheral bood vessels around the dental follicle. Resorptive process begins with the formation of osteoclasts from coalescence of the monocyte. www.indiandentalacademy.com
    94. 94. Factors influencing tooth to erupt Intraosseously:  Density of bone.  Rate of bone resorption.  The overlying tissue Bone  Primary tooth root  Gingiva Must resorb to provide an eruptive path.  Force must be generated to move the tooth vertically. Resorption over tooth seems to be dependent only on the presence of coronal portion of the dental follicle .  www.indiandentalacademy.com
    95. 95. Vascular pressure theory CONSTANT suggested that blood pressure provided the eruptive force but there has been evidence for and against the theory. FOR:  Teeth develop in a vascular site and direct relationship between conglomerates of beneath the developing crown and number of cusps and roots.  Periodontal ligament has a rich vascular supply.  Oscillatory movement of erupted teeth occurs in synchrony with the pulse.  Vasculature is under physiological control throughout life. www.indiandentalacademy.com
    96. 96. Could the VASCULATURE be source of ERUPTIVE FORCE…??? www.indiandentalacademy.com
    97. 97. There is close relationship between Osmotic tissue fluid pressure and Blood pressure.  NESS and SMALE suggested that the pressures derived from the vasculature would be exerted by the tissue fluid.  While tissue fluid osmolarity can reasonably be anticipated to change Apical pressure… Hypotensive rats show no changes in unimpeded eruption rates. www.indiandentalacademy.com
    98. 98.   The Pulsatile nature of blood flow within the follicle and periodontal ligament and its significance for tooth eruption has been noted. Cyclic intermittent forces –impulses have been shown to enhance cellular activity during bone remodelling and gene expression within the endothelium therefore their affects on bone and the tooth. www.indiandentalacademy.com
    99. 99. Tooth develop,erupt and function in a vascular site constantly exposed to PULSATIVE forces arising from blood flow. Repetative impulses acting on the calcified crown similar to the action of a hammer on a nail,are the likely the eruptive force. www.indiandentalacademy.com
    100. 100. BUT….. Even the resection of root and thus the vasculature CANNOT prevent the eruption of tooth. www.indiandentalacademy.com
    101. 101. Periodontal ligament traction theory The eruptive movement could be brought about a combination of events envolving a force initiated by the periodontal ligament fibroblasts. This force is transmitted to the extracellular compartment via FIBRONEXUS and to collagen fibre bundle which align in an appropiate inclination brought about by root formation bring about tooth movement. These fibre bundles have the ability to remodel for eruption to continue and interferance with this ability effects the process. www.indiandentalacademy.com
    102. 102. The removal of bone to create eruptive pathway is also dictated by the tissues surrounding the tooth. Evidence to support this view:  Experiments delineating the role of follicle (from which periodontal ligament forms)  Experiments on continuously erupting Rodent incisor designed to eliminate the effects of root growth and vascular supply show that as long as periodontal ligament tissue is available tooth movement occurs. www.indiandentalacademy.com
    103. 103.   Drugs that interrupt proper collagen formation in ligament also interfere with eruption. Tissue culture experiment have shown that ligament fibroblast are able to contract a collagen gel which in turn brings about movement of disk of root tissue attached to that gel. www.indiandentalacademy.com
    104. 104. PERIODONTAL LIGAMENT Before CONTRACTION ORAL MUCOSA After CONTRACTION BONE www.indiandentalacademy.com
    105. 105. Pulp theory This theory suggests that a propulsive force is generated by extrusion of pulp through THREE mechanisms.    Growth of DENTINE Interstitial PULP growth Hydraulic effects within VASCULATURE www.indiandentalacademy.com
    106. 106. Here in first stage , There is growth of dentine. This causes interstitial growth of the pulp tissue VASCULAR SYSTEM DEVELOPS Hydraulic effects within the vasculature causes eruption of teeth www.indiandentalacademy.com
    107. 107. BUT…… HERZBERG and SCHOUR removed the PULP of RODENTS incisors and found that its eruption rates were UNAFFECTED. www.indiandentalacademy.com
    108. 108. Genetic input theory If tooth eruption is to be explained at the cellular and molecular level ,a degree of genetic control is highly likely. In normal development of the occlusion,incisors develop before premolars and this process of eruption is disturbed in a number of Genetic Disorders. www.indiandentalacademy.com
    109. 109. A classification of these relationships has been represented by SANK.  Inherited defects : amelogenesis imperfecta  Disorders with supernumerary teeth or crowding of teeth  Growth retardation syndromes  Miscellaneous disorders    Hypophostasia Juvenile periodontitis Papillion lefevre syndrome www.indiandentalacademy.com
    110. 110. Although variety of theories have attempted to identify the eruptive force , none been fully supported by experimental evidence. Specific changes in the cellular activity of bone surrounding the erupting tooth provide indirect information about the mechanics of the process that need to be accounted for in ANY theory of eruption. www.indiandentalacademy.com
    111. 111. Mechanics of eruption When a tooth starts to erupt there is change in its momentum , therefore a force MUST be present.  The spherical bony crypt prior to calcification of crown exists because forces are present in the follicle that resists bone apposition. Eventhough the magnitude and direction of the individual forces cannot be determined,a summation of their distribution can be represented as series of RADIAL force vector extending to the surface of a sphere. www.indiandentalacademy.com
    112. 112. Calcification the crown provides a new mass against which the force within the follicle can act. Although the action force is such that the tooth will move occulusally , the bone resorption initially occurs in the opposite direction along the axis of force.  Bone remodeling around the erupting tooth results from the action of many forces within the follicle.In order for a tooth to move the action of eruptive force must be greater than the sum of forces resisting its movement.  As the tooth erupts the dynamic relationships between the surrounding alveolar bone , the eruptive force and the erupting tooth influence the rate of eruption.  www.indiandentalacademy.com
    113. 113. In order for a tooth to the tooth erupts the dynamic relationships between move the action of the surrounding alveolar bone , eruptive force must be greater than the sum of the eruptive force and the forces resisting its erupting tooth influence the Calcification of the movement. RATE OF ERUPTION. crown provides a NEW MASS against which the force within the follicle can SERIES OF RADIAL FORCE act. VECTOR EXTENDING TO THE SURFACE OF A SPHERE. As www.indiandentalacademy.com
    114. 114. On emergence the resistance is greatly reduced resulting in accelerated rate of eruption until a new equilibrium of forces is established. However eruption is only part of total pattern of physiologic tooth movement , because teeth also undergoes complex movement related to maintaining their position in the growing jaws and compensating for masticatory wear. www.indiandentalacademy.com
    115. 115. Shedding of deciduous teeth The physiologic process resulting in elimination of the deciduous dentition is called SHEDDING or EXFOLIATION. www.indiandentalacademy.com
    116. 116. Physiologic tooth movement Is described as :  Pre-eruptive tooth movement  Eruptive tooth movement  Post eruptive tooth movement www.indiandentalacademy.com
    117. 117. Pre-eruptive tooth movement When deciduous tooth germ first differentiate they are extremely small and there is a good deal of space for them in the developing jaw. Because the tooth germs grow rapidly, however they become crowded together particularly in the anterior of jaw. www.indiandentalacademy.com
    118. 118.  This crowding is gradually alleviated by the lengthening of the jaws , which permits the 2nd deciduous molar tooth germ to move backwards and anterior tooth germ move forward.  At the same time the tooth germs are also moving bodily outward and upward , or downward as the case may be , as the jaws increases in length as well as in width and height.  Successional tooth germs develop on the lingual aspect of their deciduous predecessor in the same bony crypt. From this position the tooth germ shift considerably as the jaw develop. www.indiandentalacademy.com
    119. 119. INCISOR and CANINE  Eventually come to occupy a position in their own bony crypt on lingual surface of their deciduous. PREMOLARS  Also in their own bony crypt finally position between the divergent roots of the deciduous molars. www.indiandentalacademy.com
    120. 120. ERUPTING INCISOR DECIDUOUS INCISOR BONE BETWEEN DECIDUOUS TOOTH AND SUCCESSOR ENAMEL OF PERMANENT INCISOR DENTIN www.indiandentalacademy.com
    121. 121. ERUPTING INCISOR ENAMEL DISSOLVED AWAY DENTIN GINGIVA PULP FOLLICLE ENAMEL SPACE REDUCED ENAMEL EPITHELIUM ALVEOLAR BONE ROOT OF DECIDUOUS TOOTH AREA OF RESORPTION PERMANENT TOOTH www.indiandentalacademy.com
    122. 122. ERUPTING CANINE DECIDUOUS CANINE RESORPTION RESORPTION OF ROOT RERSORPTION OF BONE PERMANENT CANINE www.indiandentalacademy.com
    123. 123. ERUPTING PREMOLAR DECIDUOUS FIRST MOLAR ROOT RESORPTION PERMANENT TOOTH GERM www.indiandentalacademy.com
    124. 124. PERMANENT MOLAR tooth germ  No predecessors , develop from backward extension of the dental lamina as there is little space to accommodate these tooth germ.  In MAXILLA : MOLAR tooth germ first develop with their occlusal surface facing DISTALLY,and can swing into position when maxilla has grown sufficiently.  In MANDIBLE : permanent MOLAR develop with their axis showing MESIAL inclination , vertical later. www.indiandentalacademy.com
    125. 125. OCCLUSAL surface facing DISTALLY,and can swing into position MAXILLA www.indiandentalacademy.com
    126. 126. PERMANENT MOLAR develop with their axis showing MESIAL inclination , VERTICAL later. MANDIBLE www.indiandentalacademy.com
    127. 127. ERUPTION OF MOLAR At 6 to 7 years At 4 years 6 months Perm.FIRST MOLAR at 3 years www.indiandentalacademy.com
    128. 128. EXFOLIATED DECIDUOUS CANINE DECIDUOUS MOLAR www.indiandentalacademy.com
    129. 129. Pre eruptive movements of both deciduous and permanent tooth germs are best thought of as the movement required to place the teeth within the jaw in a position for eruptive tooth movement. Pre eruptive tooth movements are combination of two factors:  Total bodily movement of the tooth germ  Growth , in which one part of the tooth germ remains fixed while rest continues to grow , leading to change in the center of tooth germ. Ex: deciduous incisor maintain their position relative to oral mucosa as jaw increase in height. www.indiandentalacademy.com
    130. 130. Histology As pre eruptive tooth movements occurs in a intraosseous location , such movement is reflected in the patterns of bone remodeling within the crypt wall. Ex: bodily MESIAL movement –bone resorption occurs on mesial surface of crypt (OSTEOCLASTIC activity) and bone deposition on distal surface / wall as a “Filling in process” Whether bony remodeling to position bony crypt is important as a mechanism or whether its merely an adaptive e response is DEBATABLE. www.indiandentalacademy.com
    131. 131. Eruptive tooth movement During this phase the tooth movement from its position within the bone of the jaw to the functional position in occlusion and the principal direction of the movement is occlusal or axial. www.indiandentalacademy.com
    132. 132. HISTOLOGY Significant developmental event associated with the eruptive tooth movement are:  Formation of roots  Periodontal ligament  Dentogingival junction The periodontal ligament develops only after root formation has been initiated and once established it must be remodeled to permit continued tooth movement. www.indiandentalacademy.com
    133. 133. The architecture of tissue in advance of erupting successional teeth from that found in advance of deciduous teeth. The fibrocellular follicle surrounding a successional tooth retains its connection with the lamina propria of oral mucous membrane by means of a strand of fibrous tissue containing remnants of the dental lamina known as GUBERNACULAR CORD. www.indiandentalacademy.com
    134. 134. GUBERNACULAR CORD www.indiandentalacademy.com
    135. 135. “in dried skull holes can be identified in jaw on the lingual surface of the deciduous teeth” These holes which once contained the gubernacular cord is known as GUBERNACULAR CANAL. As the successional tooth erupts its gubernacular canal is rapidly widened by local osteoclastic activity , delineating the eruptive pathway for the tooth. www.indiandentalacademy.com
    136. 136. GUBERNACULAR CANALS www.indiandentalacademy.com
    137. 137.  Once erupting tooth appears in the oral cavity its subjected to environmental factor that help to determine its position in dental arch.  Factors:Muscle forces -tongue -cheek -lips  Forces of contact of erupting teeth with other erupting tooth or with other erupted tooth.  Once erupted it continues to erupt at the same rate of 1mm every 3 month, only slowing as it meets its antagonist in opposing arch. www.indiandentalacademy.com
    138. 138. Post eruptive tooth movement These are those movements made by the tooth after it has reached its functional position in the occlusal plane. Divided into 3 categories:  Movements made to accommodate growing jaws  Compensation for occlusal wear  Accommodation for interproximal wear www.indiandentalacademy.com
    139. 139. Movement made to accommodate the Growing Jaws  These are completed toward the end of 2nd decade when jaw growth ceases.  Recent studies have shown that readjustment occurs between 14 and 18 years. www.indiandentalacademy.com
    140. 140.    Seen histologically as readjustment of the position of the tooth socket achieved by formation of new bone at alveolar crest and on the socket floor to keep pace with height of jaws. Apices of teeth move away 2-3mm away from inferior dental canal (regarded as fixed reference point) Seen relatively earlier in girls than boys and is related to burst of condylar growth that separates jaws and teeth , permitting further eruptive movement . www.indiandentalacademy.com
    141. 141. Compensation for OCCLUSAL wear   Is often stated that it is achieved by continued cementum deposition around apex of the tooth , but deposition of cementum occurs only after tooth has moved . No evidence as such is present that forces causing tooth eruption are still available to bring about sufficient axial movement to compensate axial wear. www.indiandentalacademy.com
    142. 142. OCCLUSAL PLANE DEPOSITION of CEMENTUM ALVEOLAR BONE ATTRITION COMPENSATION OF OCCLUSAL WEAR www.indiandentalacademy.com
    143. 143. Accommodation for INTERPROXIMAL wear Wear also occurs at the contact points between teeth and their proximal surfaces. This interproximal wear is compensated by process known as MESIAL or APPROXIMAL DRIFT. Factors which bring about drift:  Anterior component of occlusal force  Contraction of transseptal ligament  Soft tissue pressure www.indiandentalacademy.com
    144. 144. APPOSITION RESORPTION MESIAL DRIFT www.indiandentalacademy.com
    145. 145. Anterior component of force : When teeth are brought in contact ,ex:when jaws are clenched , a forwardly force is generated . This force is a result of  Mesial inclination of most teeth.  Summation of intercuspal plane producing a forwardly directed force. In case of incisor which are inclined labially , it is expected that they move in same direction BUT infact they move MESIALLY explained by “BILLIARD BALL ANALOGY” www.indiandentalacademy.com
    146. 146. Billiard ball analogy “…if the two touching balls are in line with the pocket , no matter how the first ball is struck second enters the pocket as it travels at right angle to the common tangent between the two balls…” Following this example the CANINES and INCISORS move in direction at right angles to the common tangent drawn through contact points. This leads to IMBRICATION often found in older dentition. www.indiandentalacademy.com
    147. 147. BILLIARD BALL ANALOGY www.indiandentalacademy.com
    148. 148. Cuspal inclination is a significant factor which can be demonstrated by selectively grinding cusp in such a way as to either enhance or even reverse the direction of occlusal force.  When opposing teeth are removed , thereby eliminating the biting force the mesial migration of teeth is slowed BUT not halted indicating the presence of some other force. Here the TRANSSEPTAL fibres of periodontal ligament have been implicated.  www.indiandentalacademy.com
    149. 149. Contraction of Transseptal ligament The periodontal ligament are important in maintaining tooth position. It is suggested that transseptal fibre running between adjacent teeth across the alveolar process draw neighbouring teeth together and maintain them in contact . Evidence to support this:  Relapse of orthodontically moved teeth is much reduced if gingivectomy removing transseptal ligament is performed.  Demonstrated experimentally that in bisected tooth the two halves separates from each other , if however the transseptal ligament are previously cut this separation does not occur. www.indiandentalacademy.com
    150. 150. OCCLUSAL PLANE TRANSSEPTAL FIBRES ACTION of FIBRES TRANSSEPTAL www.indiandentalacademy.com
    151. 151.  The approximal contacts are disked , teeth move to reestablish contact ,however if the teeth is also ground out of occlusion and approximate surfaces disked the rate of drift is slowed. So until the contrary is demonstrated it must be assumed that the Mesial Drift is achieved by contractile mechanism associated with transseptal ligament fibres and enhanced by occlusal forces. www.indiandentalacademy.com
    152. 152. Soft tissue pressure The pressure generated by cheeks and tongue may push teeth mesially. However if such pressure from soft tissue is eliminated by constructing acrylic dome over teeth mesial drift still occurs. Suggesting soft tissue pressure does not have a major role , however it does influence tooth position even if it does NOT cause tooth movement. www.indiandentalacademy.com
    153. 153. TYPES OF ERUPTION Three distinct type of teeth are differentiated by their eruption pattern :  CONTINUOUSLY GROWING  Tooth formation and eruption occurs throughout the life. RODENT  Dental tissue are formed from a proliferative base.  Anatomic crown and root very similar morphologically.  Teeth have extensive wear.  Eruption velocity relatively rapid , increases whenever the velocity of wear increases or antagonist tooth is removed.  Ex. Incisor of rodents and lyomorphs. www.indiandentalacademy.com
    154. 154. CONTINUOUSLY EXTRUDING Teeth stop forming once root formation is SHEEP CATTLE complete.  Well defined crown and root.  Moderate occlusal wear.  Height of clinical crown is maintained by eruption and apical migration of epithelial attachment without simultaneous deposition of alveolar bone.  As occlusal wear progress tooth eventually loosens and exfoliates completely.  Ex. Cheek teeth of cattle and sheep.  www.indiandentalacademy.com
    155. 155. CONTINUOUSLY INVESTED TEETH Human teeth belong to this type of eruption.  Teeth stop forming after predictable amount of root development has occurred.  Distinct anatomic crown and root structure.  Alveolar bone remodels in response to eruption.  The clinical crown shortens(in absence of periodontal disease) as the tooth erupts to maintain vertical height and occlusal function and brings about alveolar bone with it.  www.indiandentalacademy.com
    156. 156. ERUPTION RHYTHM The circadian rhythm in eruption is potentially significant in clinical practice.  The teeth intrude transiently in conjunction with masticatory activity and then erupts significantly overnight. The mean daily eruption velocity was seen to be 71um/day. www.indiandentalacademy.com
    157. 157. CLINICAL SIGNIFICANCE  Timing of eruption  Controlling intervention  Excessive eruption of posterior teeth is a major cause of the long face , and control of eruption during growth seems to be key to successful treatment.  The amount of force , its direction and the total hours of wear of appliance are often considered the most important factor that affect treatment outcome. www.indiandentalacademy.com
    158. 158.  Teeth erupt primarily during night with little or no net eruption during the day , it is quite possible that wearing the appliance is affective during the night and early morning period when the eruption is most active. www.indiandentalacademy.com
    159. 159.  Daily rhythm in skeletal growth  Skeletal growth requires an adequate levels of HGH which increases in the night.  The rhythm in tooth eruption also reflects this soon after the child goes to sleep.  The clinician should be aware that there is a rhythm in skeletal growth and modification of treatment may be therefore be more effective during night than during the day. www.indiandentalacademy.com
    160. 160. TEETHING Teething is a term limited by common usage to eruption of primary dentition which ususally begins in fifth or sixth month of a child’s life. In most cases eruption of teeth causes no distress to the child but sometimes causes local irritation , which is usually minor but may be fewer enough to disturb child’s sleep. www.indiandentalacademy.com
    161. 161. Clinical features of TEETHING  LOCAL SIGNS  Hypermia or swelling of the mucosa overlying the erupting teeth.  Patches of erythema on the cheeks.  Flushing may also occur in the skin of adjacent cheek. www.indiandentalacademy.com
    162. 162. TEETHING www.indiandentalacademy.com
    163. 163.  SYSTEMIC SIGNS        General irritability and crying. loss of appetite. Sleeplessness , restlessness Increased salivation and drooling Increased thirst Circumoral rash Cough www.indiandentalacademy.com
    164. 164. Associated problems  SYSTEMIC    Fever Diarrhea Vomiting LOCAL Eruption hematoma Eruption sequestrum Ectopic eruption Transposition www.indiandentalacademy.com
    165. 165. REMNANTS OF ROOTS OF FIRST MOLAR www.indiandentalacademy.com
    166. 166. PERMANENT CANINE Causing resorption of DECIDUOUS LATERAL INCISO and CANINE MISSING PERMANENT LATERL INCISOR www.indiandentalacademy.com
    167. 167. IMPACTED CANINE www.indiandentalacademy.com
    168. 168. Deciduous INCISORS Perm. CANINE TRANSPOSITION www.indiandentalacademy.com
    169. 169. LOCAL FACTORS             Aberrant tooth position Lack of space in arch Very early loss of predecessor Ectopic eruption Congenital absence of teeth Ankylosis of predecessor Retained tooth or persisting deciduous root remnants Arrested tooth formation (trauma) Supernumerary tooth Tumor Cyst Abnormal habit exerting muscular forces www.indiandentalacademy.com
    170. 170. …lastly the books  ORAL HISTOLOGY      Tencate Orban Dental Anatomy,Physiology and Occlusion -Wheeler’s Text book of PEDODONTICS -Shoba Tandon Kardos TB:The mechanics of tooth eruption,Br Dent J 181:91,1996 www.indiandentalacademy.com
    171. 171. THANK YOU… www.indiandentalacademy.com

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