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BIOLOGY OF TOOTH MOVEMENT AND
ROOT RESORPTION

INDIAN
ACADEMY

DENTAL

Leader in continuing dental education
www.indiandentalacademy.com

Periodontium





Periodontium is a connective tissue organ covered by epithelium ,
that attaches the teeth to the bones of the jaws and provides a
continually adapting apparatus for support of teeth during function.
4 connective tissues
Two mineralized
-Cementum
-Alveolar bone
Two fibrous
-Periodontal ligament
-Lamina propria of the gingiva.


Cells





Progenitor cells
Synthetic cells
a) Osteoblasts
b) Fibroblasts
c) Cementoblasts
Resorptive cells
A) Osteoclasts
B) Fibroblasts
C) Cementoclasts

Extra cellular elements


Fibres
-Collagen
-Oxytalan
Ground Substance
-Proteoglycans
-Glycoproteins


Principle Fibres of the Periodontal
Ligament(Collagen Fibres)
1.
2.
3.
4.
5.

Alveolar crest group
Horizontal group
Oblique group
Apical group
Interradicular group


GINGIVAL FIBRES
1.
2.
3.
4.
5.

Circular
Alveologingival
Dentoperiosteal
Dentogingival
Transseptal fibres(Accesory fibres)


Alveolar bone

1.
2.





Two parts
Alveolar bone proper
Supporting alveolar bone
A.- Cortical Plate
B.- Spongy Bone
Alveolar process is formed by intramembranous
ossification.
They can be remodelled owing to the structure.


Active stabilization of teeth against
forces of low magnitude


Response to normal function:
Forces applied on the teeth are1-2 kgs when soft
Upto 50 kgs against harder food


Tooth
movementVanarsdall


Peridontally Compromised Teeth


Historical Perspective
1.
2.
3.
4.
5.
6.

Celsus
Reitan
Openheim
Norton
Burstone
Davidovitch

TOOTH MOVEMENT

Application of orthodontic force –
tooth movement on account of
resorption on the pressure side and
deposition on the tension side.


Cascade of
activitiesTooth
movement
(Norton)


Classification of orthodontic
forces- Schwartz


Four degrees of biologic efficiency.
1st –Below threshold stimulus.
2nd-Most favourable 15-20 gms per square cm.Less than the
blood pressure.
3rd-Medium strength.They stop the blood. flow.Tissues are not
crushed.
4th –Forces are so high that the tissues are crushed. Irrepairable
damage may be caused to the tissues involved.


Theories of orthodontic tooth movement
1) Bioelectric theory -electric signals produced when
alveolar bone flexes and bends. Also called the
piezoelectric theory.
2) Pressure tension theory(Schwartz1932)-related to
cellular changes produced by chemical messengers.
Bien Hydrodynamic damping of tooth movement, J. D. 1966.


Theories are mutually dependent.

Bioelectric theory

1.
2.

2 unusual characteristics-quick decay rate
-equivalent signal opposite direction


Bioelectric theory






Crystal deformation-electrons migrate due to distortion
of cross linkages between the collagen fibres in the
bones.
Electropositive response (convexity) –resorption
Electronegetive (concavity) -deposition
Ions in fluids bathe the bone and cause “streaming
potential”. Similar but not the same.
No place in natural control of body.


Bioelectric theory





Stress generated signals importantastronauts.(can also be explained OB
differentiation)
Chewing /orthodontic forces.
Bioelectric signals-active growth, not
exactly known. Exogenous signals –
modify tooth movement-lag phase before
tooth movement.

Effect of Pulsed Electromagnetic Field on Tooth
Movement- Stark and Sinclair Ajo - 1987 Feb
Simple non invasive pulsed
electromagnetic (25-Hz) field can cause an
effect on the rate and amount of tooth
movement.
 20-experimental,20-control
Guinea pigs




AFTER 10 DAYS
Tooth movement
Osteoclast cell count


Observations1.

Protein metabolism indicated by creatinine ,craetinine
phosphokinase, uric acid.

2.

Na Ca K which are postulated to be the effect of pulsed
electromagnetic stimulation on the cell membrane are not increased.

3.

Exciting possibily for future consideration - Ability to initiate and
enhance the bone deposition-use with functional appliances.


Effect of Pulsed Electromagnetic Field on Tooth
Movement- Stark and Sinclair Ajo - 1987 Feb
PRE AND POST EXPERIMENT


CONTROL AND EXPERIMENTAL
GROUP


INCREMENTAL MOVEMENT

Structure of the bone


Pressure -Tension Theory


Relies on chemical signals and not
electrical signals for cellular differentiation
and tooth movement.


Cells causing remodeling of bone

2.

OB
OC



ORIGIN OF THE CELLS

1.

1)

OB-Neural crest cells(OB)- Pre Osteoblasts

a)

Contact inhibition.

b)

G1,G2 blocked cells.

Differentiation of cells under
mechanical influence


Cells causing remodeling of bone
2)




OC- Hematogenous in origin
Monocytes have been suggested to be the
predecessors. Progenitors ???
Blocked cells local preosteoclasts &
circulating preosteoclasts.


Differentiation of cells under
mechanical influence-OB & OC


Vit D metabolites


They are known to effect bone formation and
deposition via the differentiation of the comitted
progenitor cells into mature cells.


OSTEOBLASTS



RESORPTIVE FUNCTION
1) OB-Physical barrier-layer of cells on the bone surface.
If these cells are stimulated by PTH they change shape
(round) thus exposing the underlying mineral of the tooth
– only affects already differentiated cells.

.


Shape change in cells: mechanism for the
transduction of mechanical forces ( SandyBdj;1992)







Relationship exists bw cell shape and metabolic
activity.
Flattened cells synthesize more DNA than rounded
cells.
PG and PTH induce change in shape.
Suggested – in pressure sites the cells are rounded
and have catabolic effects-tension sites the cells are
flattened and in a synthetic mode.

OSTEOBLASTS




RESORPTIVE FUNCTION
2) Release certain mediators –cytokines-Bring about
osteoclastic resorption.
They are defined as short range soluble
mediators,released from the cells which modulate the
activity of other cells - ( Bone remodeling- Sajeda
Meghji 1992; Bdj ) - lymphokines.


Cytokines:Mediators of bone remodeling( -SandyBdj;1992
-Biology of tooth movement- Norton and Burstone)



Osteoclasts don’t work
independently -signal
transmitted to the
osteoclast by an
Osteoblast Cytokine.


Cytokines:Mediators of bone remodeling ( SandyBdj;1992,-Biology of tooth movement- Norton and Burstone)



RESORPTIVE FUNCTION



3)Osteiod layer covering
the bone is removed by
OB - secrete
collagenase.

•

P TIMP
TIMP-TISSUE INHIBITOR OF
TIMP-TISSUE INHIBITOR OF
METTALOPROTEINASES
METTALOPROTEINASES

OSTEOBLASTS
FORMATIVE


a)
b)
c)
d)

1)Pressure
2)Production of first messenger( physical/
chemical)
Deformation may lead to ca influx
Hormones(PTH)
They bind to the cell
They bind to the cell
Prostaglandins( macrophages )
surface receptors.
surface receptors.
Neurotransmitters(SP)


OSTEOBLASTS


a.
b.
c.



3)Second messengers
c AMP
c GMP
Ca

4)Increased bone activity


Trans membrane signaling pathway

PHOSPHOINOITIDASE
PHOSPHOINOITIDASE
INOSITOL
INOSITOL
TRIPHOSOHATE
TRIPHOSOHATE


Role of Prostaglandins (Tooth eruption and
orthodontic movement:Sandy-Bdj,1992)





Discovered by VON
Phospholipids
EULER –1934
phopholipase
Prostate gland
Arachidonic acids
Yamasaki –injection of
c AMP
exogenous PG increased
osteoclast numbers.
Prostaglandin's
Ca+2


ARACHIDONIC ACID METABOLISM




Leukotrienes and HETE (Leucocytes)
(Hydroxyeicosatetraenoic Acid) , produced
from the same substrate.



Since PGs do not fully account for bone
remodeling associated with tooth movement ,
lipoxygenase products may be involved.


OSTEOCLASTS


Resorptive action
PTH- systemic factor
Cytokines
Mechanical
Ruffled border
Lysosomal enzymes


Osteocytes


Osteocytes – cytoplasmic processes which help to gauge
the pressure changes and signal the OB.


Events during bone remodelling


PDL and bone response to sustained
forces on pressure side1.

Undermining resorption

2.

Fontal resorption


Oteoclast differentiation






2 waves
-1st wave –local cell population.
-2nd wave-blood flow.
Optimal force-frontal resoption on pressure
side
Excess force would cause –undermining
resorption.

Pattern of bone deposition and resorption


Tooth movement


Tooth movement may be divide into (Graber .Vanarsdall)
- Initial –Undermining resorption
- Secondary period-Frontal resorption



Initial phase- 3 main stages

1.

Degeneration

2.

Elimination of destroyed tissue

3.

Establishment of new attachment

Tooth movement


1.Degeneration

1.

Blood flow
Degradation of vessel walls
Cellular changes

2.
3.

-Swelling of mitochondria
-Rupture of cytoplasmic membrane leaving only isolated nuclei
between the fibrous elements



The source of cells which differentiate into osteoclasts is
lost. Area is cell free.
Glassy appearing sterile necrotic area caused due to
excessive pressure application -HYALINIZATION

Tooth movement
2.Elimination of destroyed tissue


Adjacent undamaged areas give rise to the osteoclasts
(multinucleated giant cells) which cause remodeling of
the bone on the peripheral areas.



Invasion of the hyalinized areas by the cellular elements.



Adjacent alveolar bone-undermining resorption

3.Establishment of new attachment


Synthesis of new tissue once the hyalinized tissue is
removed - Fibroblasts.

Macrophages adjacent to
hyalinized areas


Tooth movement




In secondary phase
Osteoclasts differentiate and cause frontal resorption.
Osteoblasts deposit on the tension surface.
On the tension side resorption occurs on the spongiosa
surface of the alveolar bone.
On pressure apposition takes place on the spongiosa
surface.
Remodelling also takes place on the on the periosteal
surface of the bone - helps to maintain the thickness of the
alveoar bone.

Differential Time Course Bw Frontal and
Undermining Resorption


Differential Time Course Bw Frontal and
Undermining Resorption




Initial loading leads to some amount of
tooth movement- movement increases with
time-light forces.
Movement takes place in a stepwise
fashion with heavy forces.


Effects of Tooth Movement and Force
Distribution




Distribution of forces and tooth movement
differ depending upon the type of tooth
movement.
Tipping
-Forces used to
tip the teeth
must be kept low
50gms.

Distribution



Tipping-hyalinization
Caution -alveolar
crest.


Distribution


Bodily tooth movement-uniform loading of
the teeth is seen.

.


Effects of Tooth Movement and
Force Distribution
Bodily tooth movement
Slight tipping due to the
hyalinized zone formed and
resorption adjacent to it.
Further tipping prevented by
the stretch of the fibres.




Distribution
Rotation







Practically
impossible to bring
about pure rotation
tipping is the
actual mechanism
2 pressure sites and 2 tention sites.usually 1 side shows
frontal and other undermining resorption.After 3-4 weeks
frontal resorption prevails.
Supracrestal fibres-gingival fibres, trans gingival fibres.
Long retention period, supracrestal fibrotomy.

TRANSSEPTAL FIBRES


Effects of Tooth Movement and Force Distribution


Intrusion –light forces are actually needed for intrusion as the

forces are highly concentrated over a very small area.
 If bone compact
as in adults-interrupted
force maybe better.
allows time for cell
proliferation.
 Gingival fibres are relaxed
- cause formation of
bony spicules - crestal areas.


Ditribution(Proffit)
1.
2.
3.
4.
5.
6.

Tipping –35-60gms
Bodily –70-120gms
Uprighting –50-100gms
Rotation –35-60gms
Extrusion –10-20gms
Intrusion-10-20gms


Effects of force duration and decay



1.
2.
3.

Duration – the second messenger
produced only after 4 hours.
Forces –
Continuous
Interrupted light and heavy
Intermittent


Force Duration and Decay
Ideal to have light
continuous forces but
heavier forces can be
allowed if a period of
regeneration and repair
is allowed.

4 week appointment
cycle.



Force Magnitude(Heavy pressure)


Force Magnitude(Light pressure)


AJO-DO 1985 Step Reassessment of force magnitude - Quinn and
Yoshikawa

Modifying the force magnitude as suggested by Storey and Smith

Pressure Versus Response






pressure - movement
Platue
Decline at the
end
Optimum forcelightest force
producing
maximum
or near maximum movement

Pressure Versus Response



A1-anchor teeth
M1- teeth to be moved


Stationary anchorage




Bodily versus tipping movement- anchor
teeth would move less but if the force is
really high enough to bring posterior teeth
into optimum movement rage they would
move the same amount.
Large forces


Drug Effect on the Response of
Orthodontic Forces



1.
2.

3.

+ve effect
PG
-ve effect
Bisphosphanates-act as specific inhibitors of
osteoclast mediated bone resorption.
PG inhibitors –NSAIDS, indomethacin ,
tricyclic antidepressants,anti arrhythmic
agents,anti malarial drugs, methyl xanthines.
Corticosteroids (reduce the inflamation)

Drug Effect on the Response of
Orthodontic Forces
Phospholipids
Corticosteroids

phopholipase

Arachidonic acids
NSAIDS
Prostaglandins


The effect of acetaminophen on tooth movement in rabbits
-1997 Angle Orthodontist John J. Roche et al
 It is a weak prostaglandin inhibitor - recommended
for use to relieve pain during orthodontic tooth
movement.
 14 rabbits were used.
 Lower first molar and incisor teeth on one side were
prepared with a perforation hole buccolingually.
 Maxilla was excluded from the study-21-day period.
 Over the 21 day period, each rabbit was force-fed
1000 mgs of Tylenol (10 ml of solution) per day


The effect of acetaminophen on tooth movement in
rabbits -1997 Angle Orthodontist John J. Roche,
George J. Cisneros, George Acs.


On day 21, the rabbits were sacrificed
Impressions of the final interdental distance were
obtained and poured in stone for future examination.



Acetaminophen does not seem to retard orthodontic tooth
movement, related to its lack of anti-inflammatory
properties



Concentrated in the central nervous system


The effect of acetaminophen on tooth movement in rabbits
-1997 Angle Orthodontist John J. Roche, George . Cisneros,
George Acs.


Role Of Prostaglandins In Orthodontic Tooth
Movement- Dr Anand Patil


1microgram (µgm) / injection (inj) of PG-E1 along with lignocaine
as a vehicle was injected on three different days in the vestibular
region distal to the right upper canine in 15 Patients.



The left side was the controlled side with injection of vehicle alone.



Occlusograms of pre and 60 days post canine retraction was obtained
and distal canine movement was calculated by using stable land
marks such as 1st rugae area .



The results showed statistically significant 57% increase in
orthodontic distal canine tooth movement on prostaglandin injected
side as compared with matched controlled left side.

Pre & post
Retraction
Occlusograms

AJO-DO 1983 Jan (62-75): Histochemistry of enzymes
associated with tissue degradation incident to orthodontic
tooth movement - Lilja, Lindskog, and Hamm



Acid phosphatase
LDH as indicators of bone activity.



Activity of prostaglandin synthetase since some
prostaglandins - important local activators of bone
resorption.



The maxillary right first molar in each rat was
moved in a buccal direction.



A tipping movement had been produced by the
orthodontic forces, and thus two pressure zonesbuccal and lingual.



Acid phosphatase activity Cells randomly
distributed along the bone surface in the alveoli in
non treated cases.



Prostaglandin synthetase - found exclusively in
the bone marrow-not in PDM.



Low force - rapid redistribution to the pressure zones of cells with a
high acid phosphatase activity.



Accompanied by a high enzyme activity in the adjacent osteocytes.



Low forces caused no change in the distribution and activity of LDH at
any time during the treatment.



After 1 day of high force a zone devoid of LDH activity developed in
the buccal pressure zone



No change in the activity of this enzyme was found in the bone
marrow during the treatment



Pressure areas



Tension areas


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