Root resorption in orthodontics /certified fixed orthodontic courses by Indian dental academy

INDIAN DENTAL ACADEMY
Leader in continuing dental education
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CONTENTS
o

INTRODUCTION

o

HISTOLOGY OF CEMENTUM

o

CLASSIFICATION OF ROOT RESORPTION

o

BIOLOGY OF ROOT RESORPTION

o

CONTEMOPORARY REVIEW OF ETILOGICAL
FACTORS

o

PREVENTION AND MANAGEMENT

o

CONCLUSION


Introduction


Root resorption is an essential
phenomenon that plays a
crucial role in the physiological
and dynamic process of tooth
eruption
Resorption of deciduous roots
during permanent tooth
eruption is a necessary
process that eventually results
in the exfoliation of the
deciduous tooth in anticipation
of the arrival of its permanent
successor


Periapical radiograph
showing selective
resorption of deciduous
canine root during
eruption of permanent
maxillary canine.



However, as the saying goes “.. to every
coin, there are two sides ”, root resorption
may not always be a wanted process



Root resorption that occurs in permanent
teeth is an unwanted process and is
considered pathologic.



The external resorption of roots has
perplexed the orthodontic specialty since
the early reports of Ottolengui in 1914



External apical root resorption ( EARR ) of
permanent teeth is an uncommon and
frequent sequel to orthodontic tooth
movement



Although apical root resorption occurs in
individuals who have never experienced
orthodontic tooth movement, the incidence
among treated individuals is seen to be
significantly higher www.indiandentalacademy.com



Enormous amount of literature has been
published regarding this single iatrogenic
issue



The incidence of reported root resorption
during orthodontic treatment varies widely
among investigators.



Most studies agree that the resorption
process ceases once the active treatment
is terminated



Root resorption was found to be associated with
orthodontic treatment all the way back to the early
1900’s



1927, Albert Ketcham was the first to bring the
message that apical root resorption is a common
and occasionally severe iatrogenic consequence of
Orthodontic treatment.



Advent of the common-place dental x-ray
equipment made it possible for Ketcham to
evaluate a large series of treated cases.



Since then extensive research has been carried out
pertaning all aspects of root resorption and every
potential causative factor has been studied.



Even today, research is being carried out to
identify the exact mechanism of root
resorption and the factors which may be
responsible for its initiation.



The research is mainly concentrated at the
molecular level and is aimed at identifying
and understanding the molecular signaling
that takes place during this process

Histology of
cementum


Cementum


Layer of calcified tissue covering the
dentin of the root



Specialized connective tissue similar in
physical and chemical properties to the
bone but is avascular and has no
innervations



First demonstrated in 1835 by two pupils
of Purkinje

Cementum is less readily resorbed compared to alveolar
bone, a feature that is important for permitting orthodontic
tooth movement
The reason for this feature is unknown but it may be related
to:


Differences in physicochemical or biological properties
between bone and cementum



The presence of an unmineralized layer the “cementoid”
on the surface of the cementum



The increased density of Sharpey’s fibres (particularly in
acellular cementum)



The proximity ofwww.indiandentalacademy.comrests to the root surface
epithelial cell

Physical characteristics


Light yellow color with a hardness less than that of dentin

Composition


45%-50% inorganic substances
• Calcium and phosphate ( in the form of
hydroxyapatite )
• Numerous trace elements
• Highest fluoride content in the body



50%-55% organic substances
• Type I collagen
• Proteoglycans ( protein polysaccharides )

Structure


Types ( under light microscope )


Acellular cementum
• Do not incorporate the spiderlike cementocytes
• Covers the root dentin from the CEJ to the apex
but is often missing at the apical third.



Cellular cementum
• Incorporates cementocytes in spaces called
lacunae
• A typical cementocyte has numerous cell
processes or canaliculi, radiating from its cell body
• These branch or anastamose with other processes

mostly directed towards the periodontal surface
of the cementum

Electron microscope
A –A - acellular
ACELLULAR CEMENTUM
view of an embedded
cementum
B – CELLULAR CEMENTUM
cementocyte

Collagen fibres
• Arranged in both cellular and acellular cementum in a very
complex fashion
•In some areas relatively discrete bundles of collagen
fibrils are seen, particularly in tangential sections
•These are Sharpeys fibres


Function of cementum


Primary function – furnish a medium for attachment
of collagen fibers that bind the tooth to the alveolar
bone.



There is a continuous deposition of cementum
(unlike bone, it does not resorb under normal
conditions)



New cementum is laid down as the most
superficial layer ages ( hence keeps the attachment
apparatus intact)




Also serves as a major reparative tissue
for root surfaces



Root damages ( minor fractures ,
resorptions can be repaired by deposition
of new cementum )


Classification of root
resorption


ACCORDING TO TYPE



Physiologic root resorption



Pathologic root resorption


ACCORDING TO LOCATION



Internal root resorption



Extrernal root resorption


ACCORDING TO SEVERITY

o

Surface resorption

o

Inflammatory resorption

o

Replacement resorption


SURFACE RESORPTION



Occurs constantly as microdefects on all
roots.



These normally repair themselves without
notice.



May occur anywhere but most common
periapically.



Stops when the instigating agent is removed
and there is repair of the cementum.


INFLAMMATORY RESORPTION



Occurs when root resorption
progresses into the dentinal
tubules to reach the pulpal
tissue


REPLACEMENT RESORPTION



Produces ankylosis of a tooth because bone
replaces the resorbed bone substance.


According Brezniak and Wasserstein
( classification of Orthodontically induced root
resorption )



Cemental or surface resorption with remodeling



Dentinal resorption with repair (deep resorption)



Circumferential apical root resorption.




Cemental or surface resorption
with remodeling:


In this process, only the outer
cemental layers are resorbed,
and they are later fully
regenerated or remodeled. This
process resembles trabecular
bone remodeling.



Dentinal resorption with repair (deep
resorption):


In this process, the cementum and the outer
layers of the dentin are resorbed and usually
repaired with cementum material. The final
shape of the root after this resorption and
formation process may or may not be identical
to the original form.




Circumferential apical root resorption:


In this process, full resorption of the hard tissue
components of the root apex occurs, and root
shortening is evident. Different degrees of apical
root shortening are, of course, possible.



When the root loses apical material beneath the
cementum, no regeneration is possible.



External surface repair usually occurs in the
cemental layer. Over time, sharp edges may be
gradually leveled. Ankylosis is not a common
sequel of orthodontically induced root resorption

ETIOLOGY



Root resorption may occur as a result of :
•
•
•
•

Dental trauma / surgical procedures / Infections
Orthodontic treatment
Pressure from tumors / cysts
Irritation from chemicals ( Eg. H2O2 during
bleaching)


Pulpal infection root
resorption


The most common stimulation
factor for root resorption is
pulpal infection.



Following injury to the
precementum or predentin,
infected dentinal tubules may
stimulate the inflammatory
process with osteoclastic activity
in the periradicular tissues or in
pulpa tissues, consequently
initiating external or internal root
resorption.

•Clinically teeth are not usually
symptomatic in the early period
of the process, and resorption
may be seen at this stage only in
radiographs. However, as the
process progresses, the teeth
may becme symptomatic and
periradicular abscesses may
develop with increasing tooth
mobility.
•Radiographically, radiolucency
is observed in the external root
surface of the dentin and
adjacent bone, or in the internal
root canal dentinal walls.


Periodontal infection root
resorption


Infrequently, external root
resorption may occur after
injury to the pre-cementum,
apical to the epithelial
attachment, followed by
bacterial stimulation
originating from the
periodontal sulcus.



Injury may be caused by
dental trauma, and chemical
irritation may be caused by
bleaching agents, eg
hydrogen peroxide 30 %,
orthodontic or periondontal
procedures.



Bacteria from the
periodontal sulcus may
penetrate patent dentinal
tubules, coronal to the
epithelial attachment, and
exit apical to the epithelial
attachment without
penetrating the pulpal
space.



Consequently, the damaged
area of the root surface is
colonized by hard tissue
resorbing cells, which
penetrate into dentin
through a small denuded
area causing the resorption
inside the root to spread.



At first stage, the resorptive
process does not penetrate
the pulp space because of
the protective layer of
predetin, but rather spreads
around the root in an
irregular fashion. With time,
the preocess may penetrate
into the root canal ww.indiandentalacademy.com
w



Aditionally, periodontal infection
resorption will include the
alveolar bone adjacent to the
resorption lacuana in the tooth.



If the resorptive process
reaches a supragingival area of
the crown, the vascularized
granulation tissue of the
resorption lcuna may be visible
through the enamel showing a
pink discoloration at the crown.



Radiographically, periodontal
infection resorption can be seen
as a single resorption lacuna in
the dentin usually at the crestal
bone level, expanding to the
conronal and apical direction.
With progression of the process,
radiolucency may be observed at
the alveolar bone adjacent to the
resorption lacuna of the dentin.

Orthodontic pressure
root resorption


The injury originating in the
orthodontic root resorption is
from the pressure applied to the
roots during tooth movement.
Continuous pressure stimulates
the resorbing cells in the apical
third of the roots, a possibility of
significant shortening of the
root.



Teeth are asymptomatic and
the pulp is usually vital unless
the pressure of the operative
procedure is high, which
disturbs the apical blood supply.



Radiographically, orthodontic
pressire resorption is located in
the apical third of the root and
no signs of radiolucecy can be
observed in the bone of the
root.

Impacted tooth or tumor pressure root resorption


Pressure root resorption can be observed
during the eruption of the perimanenet
dentition, especially of maxillary canines
( affecting lateral incisors ) and mandibular
third molars ( affecting madubular second
molars ).



Tumors and osteosclerosis impingning on
the root of the tooth could also be an
etiological factor for pressure resorption,
which includes both the injury and the
stimulation phases. Stimulation is related to
the pathological process that activates the
resorptive cells, tumors that produce root
resorption are most frequently those in
which growh and expansion are not rapidm
such as cysts, ameloblastomas, giant cell
tumors, and fiber-osseoseous lesions.



This type of root resorption is
asymptomatic with vital pulp
through –out the process unless
the impacted tooth or tumor is
located near the apical foramen,
disturbing the blood supply to the
pulp.



Radiographically, the resorption
area is located adjacane to the
stimulation factor, the impacted
tooth or the tumor. There are no
radiolucent areas as no infection
is involved in the process.

Impacted maxillary canine in close proximity to lateral incisor apex


Ankylotic root resorption



In severe traumatic injuries ( intrusive
luxation or avulsion with extended dry
time ), injury to the root surface may
be so large that the healing with
cementum is not possible, and the
one may come into contact with the
root surface without an intermediate
attachment apparatus. This
phenomena is termed dentoalveolar
ankylosis.



The process may be reversed if less
than 20% of the root surface is
involved. Because there is no
stimulation factor and the process
proceeds as a result of the direct bone
attachment to dentin, the term
‘ankylotic resorption’ is adequate.

oClinically, ankylotic teeth lack the
physiologic mobility of normal teeth.
This is one diagnostic sign for
ankylotic resoprtion. In addition,
these teeth usually have special
metalli percussion sound and if the
process continues, they are in infraocclusion.
oRadiographically, resorption lacunae
are filled with bone, and the
periodontal ligament space is
missing. No radiolucent areas are
observedm and at some stage, the
whole root may be replaced by bone.

Biology of root
resorption




Force application on teeth in orthodontics leads to
adaptive changes in the entire surrounding
periodontium.



This Orthodontic force leads to microtrauma of the
PDL and activation of a cascade of cellular events
associated with inflammation.



The first signs of change in response to these forces
is seen as remodelling changes by the PDL and the
surrounding alveolar bone because of the high
adaptability and regenerating capabilities of these
two tissues.




However, root resorption may occur when the pressure
on the cementum exceeds its reparative capacity and
dentin is exposed allowing multinucleated odontoclasts
to degrade the root substance.



Orthodontically induced root resorption begins
adjacent to hyalinized zones and occurs during and
after elimination of hyaline tissues. Removal of
hyalinized tissue leads to removal of cementoid and
mature collagen, leaving a raw cemental surface that
is readily attacked by dentinoclasts.



There is a positive association between removal of
hyalinized tissue and root resorption.


The cellular process




The studies in mice and rats conducted by Brudvik and
Rygh confirmed that orthodontically induced root
resorption is a part of the hyaline zone elimination
process.



The first cells to be involved in this necrotic tissue
removal are cells that are negative for tartrate resistance
acid phosphatase (TRAP –ve ) and that have no ruffled
borders.




These are Macrophage-like cells, are most
probably activated by signals coming from the
sterile necrotic tissue, the result of the
orthodontic force application.



Macrophages are scavenger cells from the
hematopoietic lineage, and their role is to
eliminate necrotic tissues. As described by
Brudvik and Rygh, the initial elimination
process takes place at the periphery of the
hyaline zone, where blood supply to the
periodontal ligament exists or is even
increased.



During removal of the hyaline zone, the nearby
outer surface of the root, which consists of the
cementoblast layer covering the cementoid, can
be damaged, thus exposing the underlying
highly dense mineralized cementum.



It is possible that the orthodontic pressure itself
directly damages the outer root surface layers
in such a way that there is a need for their
removal as well.




The root surface under the main hyaline zone is
resorbed only several days later when the repair
process in the periphery is already taking place.



The cells responsible for this later stage of removal
include TRAP +ve cells. These cells, in the process
of removal of necrotic periodontal tissue, continued
to remove the cemental surface also.



These finding have been confirmed by studies of
human premolars that were moved buccally before
their extraction.

Orthodintic force

Compression of
PDL

Removal of
hyaline material

Removal of
superficial
surface of
cementum

Root
resorption

Hyalinization
& inflammation

Activation of
osteoclasts

The repair process



Morphologically, the repair process of the
resorbed lacunae is described as beginning
from the periphery, the bottom, or all directions.



It begins about two weeks after force removal,
with the placement of acellular cementum
succeeded by cellular cementum. This process
is evident in 38% and 82% of human premolar
lacunae after two and five weeks, respectively.




In bone, osteoclasts undergoing apoptosis leave at the
bottom of the lacuna a protein layer that is composed
partially of osteopontin and bone sialoprotein. This layer is
recognized later as the cemental line with which the
osteoblasts meet on bone formation.



According to Bosshardt and Schroeder the odontoclasts
leave the root lacunar surfaces exposed with no sediment
at the base of the crater. Recently, however, it has been
reported that a specific cementum attachment protein
(CAP) has been identified in human cementum



This protein has the ability to bind to mineralized root
surfaces with high affinity. Its role in cementogenesis and
cementoblast recruitment is still under investigation.
Individual variations characterize the repair process as
evident in EARR


Methods of
measurements of
root resorption




EARR can be defined operationally as the
degree a root has shortened from its original
( or expected ) length by clastic activity



Broadly, two methods have been used to
quantify resorption :
 Ordinal

scale data :Visually assessed grades
of resorption assigned

 Ratio

scale data: Measurements with
calipers or some computer aided device)

GRADE 4

THE ORDINAL SCALE USED TO MEASURE EARR

Loss of E. & MALMGREN
BY LEVANDER atleast
o

one-half the
original length

GRADE 2
GRADEI0
3
oEvidence of of
Scalloping
Normal
One-fourth

erosion
and root
Intact root
the blunting
periapically
of apex
morphology
resorbed

oApical outline
Root length

probably and
is smoothnot
yet affected
continuous
oDistance

between the
root and
lamina dura is
uniform

Contemporary review of
etiological factors
associated with root
resorption


Type of malocclusion


Among different malocclusions, based on Angle’s
classification system, studies have observed a
statistically significant difference between class I and
class II div 1 malocclusion, with the latter exhibiting
more resorption.



Janson et al reported a higher resorption potential for
class II div 2 cases in comparison with class I , class II
div I and class III patients.



The rationale was that excessive intrusion mechanics
were necessary to correct the deep overbite in these
cases and also the torque required to correct the
palatal inclination of the incisors was high.



EXTRACTION VS NON
EXTRACTION
 The

analysis of literature reveals that
both the extraction and the non
extraction treatment have the potential
to produce damage, with the
extraction therapy being potentially
more detrimental.

 Among

all the extraction patterns,
extraction of all the first premolars
showed the greatest resorption
potential.



Mechanotherapy Begg Vs edgewise
 Although

previous studies by could not
find any significant resorption rate
between Begg light wire mechanics and
edgewise ( Tweed ) techniques, a
recent study by McNab et al has
reported a higher incidence of
resorption, as well as amount of root
resorption in patients treated with the
Begg appliance.

 They

concluded that the incidence
rate of root resorption was 3.72 times
higher when extractions were
performed as part of Begg appliance
therapy.

 Root

resorption was also observed in
all three stages of Begg treatment,
with the second stage exhibiting the
least severity

Type of tooth movement :


Intrusion and torque movements are found to be
most commonly associated with the resorption
process.



This is evident when studying class II div 2 correction
as well as Begg mechanics. The intrusion performed
in the first stage and the torquing in the third stage
make the Begg technique more vulnerable to
resorption.



The highest root resorption is reported to occur when
3 to 4.5 mm of torquing movement was performed.

Length of treatment time


The length of treatment time and root
resorption have been positively
correlated by almost all studies



These studies revealed have shown
that increased treatment time makes
tooth roots more prone to iatrogenic
response.

Type of force applied
( Continuous vs interrupted )


Interrupted forces were shown
according to studies to cause less
severe apical blunting and smaller
resorption- affected areas.



The authors of these studies
emphasize the use of less detrimental
discontinuous forces ( in the form of
elastic usage, instead of elastomeric
chains ) during space-closure stages
of orthodontic mechanotherapy.

Tooth specificity:


Evaluation of the vulnerability of specific teeth to the
resorption process in the literature has resulted in
common agreement among authors that the maxillary
incisors are the teeth that are the most susceptible to
the process.



However, Controversy still exists regarding which
incisors resorb the most: the centrals or the laterals..



The majority of the studies published reported that the
central incisors were more susceptible to the process.



Following the incisors in susceptibility to resorption in
the maxillary arch are the molars, followed by the
canines.



In the mandibular arch the most resorption-vulnerable tooth
is the canine, followed by the lateral and central incisors.



Among the posterior teeth, the most resorbed are the
mandibular molars ( with the distal root exhibiting more
resorption ), followed by maxillary molars, mandibular
premolars, maxillary first premolars, and maxillary second
premolars.



Beck and Harris in their classic article, described the
relationship of mechanotherapy to root resporption in the
distal roots of molars. According to them anchorage
archwire bends at the mesial of molars for bite opening
cause the distal roots to be compressed in the tooth
sockets, thereby initiating root resorption

Root shape


Various authors have evaluated abnormalities in
root shape and its association to the resorptive
process.



Among differently shaped root ends ( normal,
blunted, dilacerated, pipette shaped, pointed, and
incomplete) , the least resorption was observed in
blunted root ends and the greatest was seen in
pointed or tapered root ends.



This phenomena is explained by the fact that the
pressure from the axial component of orthodontic
forces is felt most at the root apex regions which
are abnormal in shape. This results in localized
ischemic necrosis, which denudes the
precmentum and cementoblasts, permitting
colonization of dentinoclasts.



In comparison to the normal root shape,
dilacerated roots show the most resorption
followed by pipette- shaped and the
incomplete roots.



Hence, any abnormal root shapes observed
in the pre-treatment diagnostic records
should be observed with caution and should
be monitored throughout the treatment
period for any iatrogenic damage.

Root length:


A positive correlation is found
between the root length and root
resorption. The studies in this regard
report that longer roots are more
prone than shorter ones to resorption.



This may be due to the greater
displacement required to produce an
equal amount of torque, versus
shorter roots.

History of trauma:


Previous history of trauma and the
presence of pretreatment root resorption
have been positively correlated with root
resorption seen after orthodontic treatment.



Also studies have found a relationship
between cortical plate proximity and
increased root resorption. All these findings
point towards the importance of obtaining
pretreatment diagnostic records and proper
evaluation. So that any risk elements can
be identified and described.

Overjet or overbite:


Studies to date have agreed with a
positive correlation between an
increase in overjet and root
resorption.



The main reasons attributed to this
phenomenon are the greater amount
of torque and greater root
displacements required to correct
excessive overjet.

Age, Gender and ethnicity: are
they contributing factors?


Biologic factors such as age at the start of
treatment and gender, have long been
associated with risk factors for the initiation of
root resoption.



Age at the start of the orthodontic treatment
and incidence of root resorption have been
poorly correlated in almost all recent studies.



Conflicting results have been seen when
gender is considered. Various studies
supported that females are more prone to root
resorption whereas various others stated that
men were more prone.



The majority of the studies support a
lack of correlation between gender and
resorption.



The relationship between ethnicity and
root resorption was evaluated recently.
The results showed less severity
among Asians in comparison to
Caucasians and Hispanics.

EFFECT OF DRUGS


Drugs such as corticosteroids and alcohol have been
identified as predisposing factors.



An increased risk for root resorption among asthamatic
patients was also recently reported by Mc Nab et al.
they did a tooth – specific analysis and found a higher
incidence of resorption for the roots of maxillary molars.



The changes they observed were attributed to changes
in the immune system of patients and the close
proximity of maxillary molar roots to the maxillary sinus.


Prevention




Quantitative as well as qualitative analyses of resorptive
process are required to prevent the occurrence of the most
common iatrogenic damage following orthodontic tooth
movement.

Before treatment



General considerations. The patient/parents must be
informed about the risk of EARR as a consequence of
orthodontic treatment.



Root resorption should be discussed during
consultation.



Every informed consent form signed by the
patient/parents (and the orthodontist) should specifically
outline the risk of EARR



The rule of thumb is better to inform early
than to later apologize.



It is obvious that if the orthodontist decides
to initiate treatment after reviewing all of the
relevant data collected, the expected
esthetic and functional benefits far outweigh
the minor root changes observed in most
patients.

At the start of treatment



The importance of diagnostic records and
thorough evaluation of them should not be
overlooked from a medico-legal point of view.



Obtaining records periodically during active
treatment is a must.



Of the various methods ( clinical, histological,
radiographic, biologic markers), radiographs
remain the most important tool for evaluation
of pre treatment, in-progress, and post
treatment status of tooth roots.



Recent researchers have recommended
periapical films for patients at high risk of root
resorption and bone loss. They have also found
that abnormalities were clearer in periapical
films.



Levander et al have supported the use of digital
images for the purpose of visualizing root
resorption. Digital images provide a better image
quality than the conventional radiographs and
also the radiation exposure is lesser to the
patient.



The use of computerized tomography for
evaluation of resorption and its sensitivity in sitespecific ( mesial, distal, buccal, or lingual )
detection of the process has been reviewed
lately.



Recently, Mah and Prasad discovered
biologic markers for root resorption in
crevicular fluid. In their experiment, they
measured dentin sialophosphoprotein
and found their levels to be high in GCF
that was in proximity to resorbing
primary and permanent tooth roots.



This research may be in future used as
a simple and practical method for
predicting initiation of the process


Management


Is the process reversible?


Review of literature reveals that when a
tooth loses its apical material beyond
the cementum, no regeneration is
possible.



The reparative process begins 2 weeks
after the force is discontinued, and the
effects are evident within 6-8 weeks.



Acellular cementum is laid down in the
initial stages, followed by cellular
cementum.



The according to various authors, the
process starts from either the
peripheral region, the apex, or in all
directions, and individual variations
seem to be very common as far as the
repair is concerned.

Midtreatment approach to
root resorption


Progress periapical films or panoramic
radiographs should be analyzed during
the treatment.



A review of literature supports a
temporary halt in orthodontic treatment
for a period of 4 – 6 months.



The resorptive process ceases and
the reparative process starts within
this period.



Appropriate follow up and necessary
counseling should always accompany
this approach.




The role of drugs in decreasing root
resorption has been reported in some
recent publications.



Drugs such as bisphosphonates,
Nambumetone ( an NSAID ), various
hormones and cytokines including
prostaglandin E2 and L-thyroxine etc
have been tried and tested to little
clinical success.



A recent report by Baily et al
evaluated the effect of lowintensity pulsed ultrasound
( LIPUS ) in the healing
process of orthodontically
induced root resorption in
humans. The result of this
study are quite encouraging,
as it demonstrates a noninvasive method to reduce
root resorption in humans.

Conclusion




External apical root resorption is an iatrogenic
consequence of orthodontic treatment. Keeping this in
mind, we as orthodontists should take all known
measures to reduce its occurrence.



Although several protective procedures have been
suggested, none of them can actually prevent EARR
with any degree of certainty.



Probably in the future, more genetically based studies,
as well as other basic science research, might clarify
the exact nature of EARR and hopefully help to
prevent or even eliminate this phenomenon.


THANK YOU


References




Current principles and techniques : Graber Vanarsdal : 3 rd
edition



Root resorption: The possible role of extracellular matrix
proteins: Adam Lee ; Glen Schneider : AJO 2004 ; 126



Critical issues concerning root resorption : A
contemporary review : Krishnan V. ; World Journal of
orthodontics,vol & no.1 2005, pg 30-39



Root resorption in orthodontic therapy: : Edward F. Harris
; Seminars in orthodontics : 183-191



Root resorption- diagnosis,classification and treatment
planning based on stimulation factors : Dental
Traumatology 2003 : 19;175-182



Contemporary Orthodontics, William R. Profitt, 3rd edition



Oral Anatomy, Histology & Embryology, B.K.B.
Berkovitz, 3rd edition



Brezniak N, Wasserstein A. Root resorption after
orthodontictreatment: Part 1. Literature review. Am J
Orthod 1993;103:62-6.



Brezniak N, Wasserstein A. Root resorption after
orthodontic treatment: Part 2. Literature review. Am J
Orthod 1993;103:138-46.



Predicting and preventing root resorption : Part I :
Diagnostic factors : Glen T. Sameshima : AM j
Orthod ; May 2001, 119


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