Extraction in orthodontics /certified fixed orthodontic courses by Indian dental academy

Extractions in orthodontic
treatment

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Introduction:
Extraction is necessary part of the treatment in some cases,
but in others it is contraindicated.
Before extractions are considered, an exhaustive study of
the case must be made by a clinical examination of the patient,
paying particular attention to caries or restored or traumatized teeth
which might subsequently give rise to symptoms. Radiographs
should be scrutinize to ensure the presence of all teeth
.


If a clinicain desires to change the facial profile, the choice
of teeth prescribed for extraction will influence the result
significantly. In simple terms, if maximum anterior retraction in
both the upper and lower arches is the objective, most orthodontists
would remove the four first premolars. For lesser retraction in the
lower face ( patients with a large chin button), the upper first and
lower second premolars would be removed. Less overall retraction
occurs with the extraction of the four-second premolars, and the
least occurs with removal of the fours first molars.


DIAGNOSIS AND TREATMENT PLANING.
In 1965, Henry gave two basic criteria for extraction of second
bicuspids:
1.

Mild degree of corwding and an excellent profile.

2.

No crowding and fullness of the lips.


Although Begg stated that second premolars should not be
extracted instead of frst premolars unless they are carious or poorly
formed, there is no reason why Henry’s criteria could not be applied
to the Begg technique. Nance was one of the first to draw attention
to the option of extracting second premolars in mild discrepancy
cases (the sort of case in which we wish we might extract a part of a
tooth rather than a whole tooth). He stated that this avoided a
disned-in-face and that there was less tendency for residual spacing.

Carey advised second premolar extractions in cases with a
discrepancy greater than 5mm. Dewel observed that in the
borderline case, extraction creates more space than is necessary and
this must be closed by reducing the anchorage value of the buccal
segments. Logan noted similar findings and listed other factors of
significance when second premolars were extracted.

1.

The maxillary first premolar is more esthetic than
the second.

2.

The contact point of mandibular first molar and first
premolar tended to stay closed.

3.
Rapid space closure reduces the possibility of
buccal or lingual bone furrows in the extraction site.
4.

Overbite can be controlled easily.

5.

.Closure of anterior open bite is facilitated by
reducing posterior vertical dimension.


DeCastro considers the mammalian dentition as an arrangement of
three independent segments-an anterior segment ending at canine
and two posterior segment. When the second premolar is extracted
in the middle posterior segment, only this segment is shortened.
But, when first premolar are extracted, both the segments are
shortened. Hence there will be greater effect on the functional
integrity of the dentition.


History
The role of extraction in orthodontics was recognized by
John Hunter (in 171) in his natural history of teeth.
Spooner (in 1839) advised the extraction of four premolars
or the 1st molars when defective. Farrar (in 1888) considered
judicious extraction an essential requisite “for the prevention and
correction of irregularities”. He recognized that indiscriminate
extraction may “.......... Create a new difficulty while removing the
original one”. Pierce, writing in the Dental Cosmos of October,
1959, advocated extraction in tooth crowding as a means for
simplifying orthodontic procedure.

E.H. Angle on Extraction
There have always been those who practiced extraction,
even advocating it as a panacea for all types of malocclusion and
for the reduction of dental decay in the remaining teeth.
Extraction to avoid “collapse” and to improve facial appearance
was advocated by Angle in his book.
Angle States : It is difficult to lay down any precise rule regarding
extraction, but it is a matter which involves the broadest
consideration and closest study of each case, after taxing the
judgement as much as any problem in orthodontia.
He gives two reasons for extractions in Class I Malocclusion.

First, where the jaws are so small, either naturally or because of
arrested development, that the angles of inclination would be too
great if all the teeth were placed in line. Procumbency of incisor
teeth.
Second, where extraction is necessary form the
requirements of the facial lines, for the development of the arches
may be such as to afford on abundance of room for the malposed
teeth, and yet placing them in the line of occlusion may result in
marked dental or labial prominence and the facial result be more
unpleasing than if the teeth had been allowed to remain in
malposition.
He states further..........There seems to be a difference of opinion
as to the choice of teeth in case a sacrifice be necessary, either the
first or second bicuspids are dental collapse. The orthodontist
cannot always make the extraction decision on a priority basis. It
is not always possible to predict what the profile will look if the
teeth were not extracted.www.indiandentalacademy.com

Margolis, popularized the view that the most effective extraction
strategy to relieve crowding is to extract the premolar teeth closest
to the is the of crowding and this would dictate extracting first
premolar in most cases.
PROCUMBENCY OF MANDIBULAR INCISORS AS A
CRITERION FOR EXTRACTION.
When the ramus of the mandible is short, as indicated by a line
drawn tangent to the mandibular plane passing through the
occipital bone, instead of tangent to almost tangent to the bone, as
pointed out by Atkinson, the mandibular incisors may appear to be
in precumbent relationship but frequently will be found to be at 90°
or less to the mandibular plane.

When the incisor teeth in different mandible are viewed in cross
section, a variety of relationship can be seen between the body of
the mandible and the teeth. In some mandibles, the entire dental
arch may be situated lingual to the body of the mandible, when
teeth showing an outward flaring to varying degrees.
The mesiodistal relationship of the dental arch to the base of the
mandible is an important factor in determining the need for
extraction when facial esthetics are concerned.
However,
extraction of teeth does not depend solely on the degrees of
procumbency of the mandibular incisors teeth in relation to the
mandibular plane. The size of the gonial angle, the labial lingual
position of the mandibular arch, the presence of tooth crowding
and the relationship of the incisor teeth to the pogonion are most
important factors in determining the need for extraction as a
method of reducing facial prognathism than is incisor
procumbency.

EFFECT OF EXTRACTION ON OVERJET AND OVERBITE
This depends on the type of occlusion present and the tendency of
overbite and over jet shown by the patient, the type of appliance
used and the manner in which it is used. Extraction is not
responsible per se for increase or decrease in overbite.
When the anterior or posterior teeth are crowded with or without
procumbency of the mandibular incisor and the basal arch shows
the presence of the “Simian Shelf” (there is an extreme subalveolar
constriction), extraction is indicated one jaw more than in the other.
Extractions which have to be performed in Class I cases other than
teeth completely displaced from the arch are usually better to be
symmetrical, i.e., the same tooth usually being removed from each
quadrant of the mouth, in both upper and lower arches.

Angle Class II. In some of these cases the upper dental arch may
appear relatively further forward than the lower arch. Where such a
condition has been diagnosed it may be desirable to discourage
forward development of the upper arch more than the lower. Of the
malocclusion in severe and the root apices of the lower teeth are in
correct relationship to one another, extraction of a premolar tooth
from either side of the upper arch will cause a relative impairment of
the forward development of the upper arch and allow the upper
anterior teeth to be moved palatally with appliances thus improving
the upper and lower incisor relationships. The upper first premolars
are usually the teeth of choice though some orthodontist favour the
removal of the second premolars. In Class II treated by this method
the posterior teeth retain their apparent post normal relationship
which in functionally satisfactory and the method is often suitable
for patients who are not likely to respond to extensive appliance
therapy.

Extraction from the lower arch in Class II case are necessitated by
extreme caries. It is almost always essential to extract teeth from
the upper arch least the overject increase. Normally extractions
one avoided in the lower arch unless indicated by the orthodontic
treatment plan, in any particular case or for bringing the lower
molar forward. On that case the second premolars are preferred.
Angle Class III - Similar principles guide the decision to extract
teeth from prenormal cases. When the treatment of Class III cases
is complete, the upper incisor may be inclined labially to an
abnormal extent and may be only be prevented from assuming a
lingual relationship to the lower incisors by the degree of overbite.
Because of the effect upon the forward development of the upper
dental arch extraction of the upper teeth should be avoided in most
cases. If such extractions are inevitable, consideration should be
given to the reduction in numbers of the lower teeth.
.

This is especially so where “the malocculusion is accompanied by
the excessive forward development of the mandible”. For this
reason, if extractions from the lower arch are considered necessary
they should performed as early as possible in order that the
maximum interference with the forward development of the dental
arch is obtained.
ADVERSE POSITION OF ROOT APICES
Provided sufficient space exists the inclination of the crown of the
tooth to an abnormal position is usually readily corrected with
simple forms of orthodontic render extraction necessary for even
where the tooth has not been displaced traumatically, its eruption
likely to be impaired by the root deformity.

PRESERVATION OF SYMMETRY
There is always a continuos normal forward movement of the teeth to
maintain approximal contact. It is explained that the pressure caused
by growth and eruption is guided round he arch by the lips to the
midline where the forces from each side are equal and opposite and
therefore balance one another. If the tooth is extracted form one
side of the dental arch only, the forward movement of the teeth
mesial to the space is impaired and therefore, pressure form that side
is deficient. The pressure from the other side is normal however, the
inequality of pressure may cause the incisors to be inclined towards
the side from which the tooth was removed especially where the
tooth was lost at an early age.


Where teeth are congenitally missing from one arch, the other
arch being intact (the arch relation being normal and the muscular
forces of the tongue, lips and cheek adequate) it may be advisable
to balance it by symmetrical extraction of similar teeth from the
opposite side.
Similarly, where pathological conditions
necessitate the extraction of the tooth from an arch, further
extraction may be justified to preserve symmetry or to maintain
the relative proportion in arch size.


EXTREME ABNORMALITY OF JAW RELATIONSHIP
In those cases where treatment for a malocclusion has not
been sought until a late age of fifteen years and above extraction
of one or more teeth may well reduce the duration of treatment
and overcome a possible lack of cooperation of the patient to a
long course of treatment. It is particularly useful in children who
have very little growth left.


LATE TREATMENT
In those cases where treatment for a malocclusion has not been
sought until a late age of fifteen years and above extraction of one
or more teeth may well reduce the duration of treatment and
overcome a possible lack of cooperation of the patient to a long
course of treatment. It is particularly useful in children who have
very little growth left.


CRITERIA FOR EXTRACTION
The criteria for extraction may be summarized as follows:
1. When the labio-lingual dental relationship to the facial plane
(N-Pg) where the dental arch is not crowded and is situated far
enough in a lingual direction so that existing procumbency of
incisor teeth does not produce facial proganthism while
gonial angle is less than 125° and the ramus of the mandible
is long enough for the base of the mandible to approach a
parallelism with FH plane, extraction becomes a purely

subjective procedure.

2.

The size of the gonial angle. The incisor procumbency in
relation to the Frankfurt plane is more pronounced in the
presence of a short ramus and an extremely obtuse gonial
angle.

3.

The axial inclination of the mandibular incisors and their
effect on the Frankfurt mandibular incisor angle.

4.

The type and degree of irregularity and crowding present
in the dental arches.

5.

The direction of jaw growth.

6.

The relative difference in the size of the basal arches i.e.
Basal arch length.

7.

The thickness and distribution of the soft tissue covering
the facial bone.

If the arrangement of the teeth is asymmetrical and the removal of
only one premolar from an arch will permit the remaining teeth to
be brought into good alignment, this may be done.
When the posterior segment of the maxillary arch are narrower than
the mandibular dental arch, extraction should not be undertaken
until buccal lingual arch relation of the posterior teeth is
established. After this is accomplished the necessity for extraction
should be reevaluated.
TWEED-THE FRANKFURT MANDIBULAR INCISOR ANGLE
The Frankfurt mandibular planes are extended into space and meet
to form the Frankfurt mandibular angle. The third angle is drawn
along the long axis of the most labial mandibular incisor. The
angles forming this triangle are used in diagnosis, classification,
treatment planning and prognosis.

Tweed presents the role of the Frankfurt mandibular angle in
determining the need for extraction as follows:
When the Frankfurt mandibular plane angle range is 20° to 30°, the
prognosis for favorable orthodontic is excellent for those nearest the
20° to good for those near the 30° extreme. Reduction of the
alveolodental proganthism will require extraction of teeth where
necessary to permit tooth alignment over the basal arches.
Tweed found that about 60% of the malocclusions fall within the
20° to 30° range of the Frankfurt mandibular plane angle when
measurement are taken from profile radiograph and more than half
these cases require extraction of teeth.

When the Frankfurt mandibular plane angle is 30° to 35° as
measured the prognosis for reducing the alveolodental prognathism
varies form good at 30° to fair at 35°.
When the Frankfurt mandibular plane angle range is 35° to 40°, the
prognosis of reducing alveolodental prognathism is fair at 35° and
unfavorable at 40°.
When the Frankfurt mandibular plane angle range is 40° upwards,
Tweed considers prognosis to be unfavorable. In some causes the
removal of teeth in the 40° or above Frankfurt mandibular plane
angle cases detracts from rather than enhances facial profile.


How considers tooth crowding to be due to deficiency in arch
width rather than length. He found a relationship to exist between
the total width of the mesiodistal diameters of the teeth anterior to
the 2nd molars and the width of the dental arch in the 1st premolar
region. Arch length is measured at the midline from the distal in
measured at the midline from the distal marginal line of the 1st
molar to the most anterior point of the basal arch as defined by
Salzmam. This is then compared with the arch width for possible
extraction.
Cases with between 37 to 44% of the intercanine fossa width to
mesiodistal arach width (1st molar to 1st molar) are in the doubtful
category and extraction of the 1st premolars is the result of more or
less subjective treatment planning. When the ratio between
intercanine fossa width and the 1st molar to 1st molar width is less
than 37%, it is considered by Howe to be indication of basal arch
deficiency and extractionwww.indiandentalacademy.com is indicated.
of the 1st premolar

SERIAL EXTRACTION
Serial extraction is the planned and sequential removal of the
primary and permanent teeth to intercept and reduce dental
crowding problems. The principle of extraction of specific primary
and permanent teeth was suggested as a means to eliminate arch
length deficiency over 200 years ago, when Bunon proposed an
extraction sequence that would improve arch length deficiency
problems.
The sequence consisted of ;
1. Extraction of the primary canines to permit the self-alignment of
permanent incisor.
2. Extraction of the primary first molars to promote the eruption of
the first premolar.

3. Extraction of the first premolar to relieve the crowding and
permit eruption of the permanent canines.
Rationale :
The rationale for serial extraction has its foundation of several
basic biologic facts and processes;
1. Tooth material arch length deficiency
2. Physiologic tooth movement.
3. Normal dental, skeletal and profile development.
Dental crowding the result of inadequate arch size, insufficient
basal bone and /or excessive tooth material - is epidemiological
the common types of malocclusion.

Physiologic tooth movement or drifting occurs in a rather
predictable pattern dependent primarily on the dental age at the
time of extraction.
If the primary teeth are extracted prematurely, this will influence
the eruption rate and position of permanent successors.
The treatment objective for a serial extraction is to reduce or
eliminate the need for extensive appliance therapy. Although this
is an idealistic goal, it is the initial objective in considering serial
extraction.


The signs or symptoms indicating that an arch length deficiency
exists and that a serial extraction.
Midline shift of the mandibular incisor due to a displaced lateral
incisor.
Premature moss of primary canine, abnormal or symmetrical
primary canine root resorption.
Ectopic eruption of maxillary first molar
Labial but unerupted permanent canines that are extremely
prominent, gingival recession on a labially displaced incisors,
extreme labial displacement of a mandibular incisor, maxillo
mandibular alveolar dental protrusion, unusual shape, size or
number of teeth and crowded maxillary or mandibular teeth that are
excessively inclined labially.

The indication for doing a serial extraction must
correspond to the patients need and biologic characteristic and
must fulfill the desired objectives. There is no absolute sequence
for all situation. However, to select an ideal patient for a serial
extraction, for an 8 year old with normal number, size and shape
of teeth, a class I canine and molar relation with minimal overjet
and overbite mayne chosen with symmetric arch length tooth size
deficiency in the early stage of the middle mixed dentition, a
normal eruption sequence and dental development present
radiographically, a normal skeletal growth pattern, and a normal
AP vertical and transverse skeletal pattern.


Treatment planning and extraction sequencing: Deciding on the
timing and sequencing for extraction of primary and permanent
teeth is the key to success. Unfortunately, there is no plan
applicable to all situations. Every serial extraction must be
individualised to accomplish the objectives for the particular
patients developing malocclusion.

Class I malocclusion - premature loss of primary canine.

This situation is rather common and will usually be accompanied
by a midline shift to the side from which the tooth has been lost.

If the skeletal, profile and dental patterns, the overjet, axial
inclinations and the number, size shape and development pattern are
normal and f there is 5 to 10 mm of arch length discrepancy per
arch, the remaining primary canine should be extracted of the
permanent first premolar have more than half the roots formed, the
primary first premolars should extracted; if not primary first molar
should extracted when the root formation is half completed. The
first premolar should be extracted as they emerge.


Congenitally missing teeth
Congenitally missing teeth excluding 3rd molars are observed in
more than 5% of the population. The teeth most frequently
missing are the mandibular 2nd premolars, maxillary lateral
incisors and maxillary 2nd premolars when a congenitally missing
tooth is observed in the middle mixed dentition period, one should
make a decision as to whether to undertake a serial extraction.
Interview of the fact that dental drifting can close apices, the plan
should be formulated.
Maxillary lateral incisor
Lingually locked in lateral incisor are a definite indication of
tooth size- arch length discrepancy. Delaying extraction may
cause other cross bite or root resorption.

If the objective is to close the space, the desirable characteristic
would be:

1. A crowded mandibular arch no spacing or crowding in the
maxillary arch and a Class I buccal interdigitation.

OR
2. No spacing or crowding in both aches and a Class II buccal
interdigitation.


In the former the maxillary primary lateral incisors and canines and
mandibular primary first molars and canines should be extracted
when the canine roots have half formed. The mandibular first
premolars are extracted when they emerge. It might be necessary
to extract the maxillary primary 2nd molars to facilitate
imterdigitation. Then the maxillary primary canines and lateral
incisors are extracted when the maxillary canine roots are half
formed.

Again the extraction of either the maxillary or mandibular second
premolar may be necessary to facilitate buccal interdigitation.


In patients with Class II tendencies or excess maxillary space, this
procedure is not successful and one should consider prosthetically
replacing missing maxillary laterals.
Mandibular 2nd premolar
In a patient missing a mandibular second premolar in whom there
is maxillary crowding and a Class I buccal interdigitation one can
consider the same sequence as a Class I malocclusion with the
2nd premolar and primary molar removal. This will be more
successful if the extraction are done in the middle mixed
dentition.


Choice of teeth for extraction
The choice of the teeth to be extracted depends on the local
conditions which include the direction and amount of jaw growth,
discrepancy between size of the dental arches and the basal arches;
sate of mobility, position and eruption of the teeth, facial profile,
the degree of alveolodental prognathism, age of the patient and
the state of the dentition as a whole. In adults the teeth to be
extracted other condition being favorable are those that entail the
least amount of tooth movement for obtaining favorable results.


Incisors
They should not be extracted unless damaged beyond satisfactory
repair. Extraction of incisor teeth should be avoided especially
when the canine teeth are in infraversion or superversion since this
tends to produce greater disharmony. When lateral incisors are
severely fractured in young children, it becomes necessary to
extract the broken incisor and move the adjacent canine to occupy
the space. In the mandible, the space left by an extracted incisor
should not be allowed to close by itself, because tooth shifting is
not predictable. Active closure of the space is required by means
of orthodontic appliances. Extraction of mandibular incisor teeth
can lead to disturbance of the entire occlusion. Malocclusion
treated in this manner shows a tendency to develop abnormal
overbite and cusp-to-cusp occlusion of the buccal series of teeth.

When there is a decided discrepany in the size of the maxillary and
mandibular incisors themselves, then consideration may be given
to the removal of an incisor tooth through such cases are rare. The
inter canine distance of the maxillary and mandibular teeth should
be considered when contemplating extraction of incisor teeth.
Occlusion with incisor tooth extraction show a tendency to cusp to
cusp relation on one side of the dental arches with what is known
as "silppage'. There may be a tendency to increased maxillary
overjet and occasionally also a deep overbite.


Canines
They should not be extracted by choice as an orthodontic measure
because of their importance in maintaining facial expressions and
balance. In order to avoid prolonged treatment with appliance or
where it is impossible to bring the canine into normal alignment, it
may be necessary to remove a canine when impacted or in ectopic
eruption.
First Premolar
They are the teeth usually extracted when it is necessary to obtai
stable results in malocclusion with dental arch and basal
discrepancies . The choice depends on the age of the patient, the
presence and severity of caries, presence of extensive filling in the
dental arch.

When forward positioning of the molars is not required to any extent
the 1st premolar should take precedence over the 2nd premolar as the
teeth to be extracted.
Second Premolar
They may be extracted instead of the 1st premolar if they are not
sound or their position in the arch is such that extended orthodontic
tooth movement would be in the maxilla, however, the second and
the third molars before emergence have their crowns inclined distally
and bucally.


After extraction of a maxillary first molar, the adjacent eruption
second permanent molar performs tipping movement in which the
crown moves more mesially. This movement corresponds more
or less with the normal changes in mesio-distal angulation that an
erupting second permanent molar would experience if the first one
had not been extracted at an early age. The tipping movement is
however, a little greater.
A considerably more unfavorable situation exists in that respect in
the mandible. Under normal circumstances a second permanent
molar that originally was mesially inclined would upright itself on
eruption. Extracting the first permanent molar affects the eruption
path of the not yet emerged second molar, which subsequently
will display little or no up righting movement or even will tip
more mesially. This last movement is the opposite to what is
required to achieve an acceptable angulation after emergence.

In contrast to the mandibular teeth, the maxillary 2nd molar in the
absence of the first molar show only a slight abnormality in the
mesiodistal angulation. TO reach a good mesiodistal angulation the
root apices of the maxillary molars do not need to move so far
mesially as those in the mandible. It also makes a difference how
far the eruption of the 2nd molar has progressed a the time the 1st
molars are extracted.
The mesio-lingual rotation of the second molar after extraction of
the first molar is more pronounced in the maxilla than the mandible.
Maxillary second molar rotate about an axis more or less through
the mesiopalatal cusp and the palatal root. Madibular second molar
also rotate mesiolingually but less so.


After extracting the first molar, the adjacent second molars drift
more mesially in the maxilla than in the mandible.
The mesial tipping of the second permanent molars (especially in
the mandible) their mesial drifting and rotation (especially in the
maxilla) and the distal tipping and rotation of the
premolar(especially in the mandible) leads to a ramshackle
occlusion. Both transversely and sagitally, good interdigitation is
lacking.


Asymmetrical extraction:
When in both jaws the first permanent molars are extracted on one
side only, the changes will be limited chiefly to that side. The
midlines will become displaced towards the extraction side. This
deviation is limited in extent and is seldom recognized as an
esthetic disorder. Of course the dental arch midlines often cease
to correspond because the mandibular incisor migrate more than
maxillary incisor.
Pronounced asymmetries and disturbed
occlusions develop when one side a mandibulat molar is extracted
and a maxillary molar on the other side.


Definite contraindications prevail against extracting first
permanent molars. Indications to extract one or more first molar
for orthodontic reasons alone are seldom , if ever, encountered. If
extraction therapy is required, preference for removal goes to
premolars or occasional second permanent molars. Only when
first molars are so defective that there can be no hope of keeping
them intact despite the best care, and the premolars are sound,
would the molars be sacrificed rather than the premolar or should
be realized that such cases will require orthodontic therapy that is
considerably more complex than usual. This certainly is
undesirable in a situation where defective first molars are a
symptom of a generally weak dentition with a high caries
susceptibility.


The only actual indication for extracting first permanent molar is
the impossibility of conserving them for a greater part of life.
Sechwarz stated that when first permanent molars appeared likely
to be lost as a result of caries before the age of 30 years, removal
at an early age is indicated.
In conclusion, a purely orthodontic indication is rarely found for
extracting first molar. Nonetheless, these teeth are sometimes
extracted in the context of orthodontic therapy.


Two circumstances justify this approach. The first is when
removed of qualitative worthless first molar takes the place of
extracting for example a sound premolar. The second is when
orthodontic treatment required for other reasons can be employed
to correct most of the undesirable effects for extracting defective
first molars. In these cases extraction would not be contemplated
as a part of orthodontic treatment if the molars were at all
reasonable in quality.
Second molar extraction: In the last few years, the extraction of
the 2nd molar has become a matter of great interest and
controversy within the dental profession. Liddle believes that
many malocclusion develop because of eruption forces of the
permanent second molars and that premolars is treating the effects
rather than the cause of the malocclusion

CHRONOLOGY AND DIMENSIONS OF SECOND
MOLARS
Calcification of both the mandibular and maxillary second molars
at 2 1/2 to 13 years of age 7 to 8 years the crown are fully formed.
Eruption of the mandibular second molar is seen at 11 to 13 years;
the root development is not completed until 14 to 15 years. The
maxillary second molar erupts at 12 to 13 years of age with its
final root formation realized at 14 to 16 years
Average crown dimension for the mandibular second molars are
10.5mmm both mesiodistally and labio lingually. Crown height
averages 70mm and tooth length 20.9mm.
The maxillary second molar has an average mesiodistal diameter
of 9mm and buccolingual dimension of 11m. mean crown height
is 7mm with the averagewww.indiandentalacademy.com 18mm.
tooth length being

Advantages and indications of second molar extraction
According to Wilson and Graber - the following reasons were
proposed as the major advantages and favorable results of second
molar extraction.
-

Facilitation of treatment using removable appliance.

-

Reduction in the amount and duration of appliance therapy.

-

Disimpaction of third molars.

-

Faster eruption of third molars.

-

Prevention of dished - in appearance of the face at the end
of facial growth.

-

Prevention of late incisor imbrication.

-

Facilitation of first molar distal movement.

-

Distal movement of the dentition only as needed to correct
the overjet.

-

Fewer residual spaces at the end of the orthodontic
treatment.

-

Less likelihood of relapse.

-

Good functional occlusion.

-

Good mandibular arch form.

-

Reduction in incisal overjet.

Chipman believes that the procedure is indicated when;
1.

The second molars are severely carious ectopically erupted
or severely rotated.

2.

Mild to moderate arch length deficiencies exist with good
facial profile.

3.

There is crowding in the tuberosity area with a need to
facilitate first molar distal movement.

According to Wilson premolar extraction in Class I crowded cases
without the use of fixed appliance therapy will result in the tipping
of teeth poor contact points, increase in overbite, and functional
interference. On the other hand according to Wilson, extraction of
the second molar extraction

Timing for mandibular second molar extraction.
Kokich in his summary of presentation given by Scholz Stressed
three criteria is to be met when making the decision on timing of
the dentition.
The third molar crowns should be completely formed but
extraction should be performed before the root begins to develop.
The axial inclination of the third molar buds should not be greater
than 30° relative to the occlusal plane.
Mandibular third molar should be in close proximity to the second
molar roots to ensure adequate mesial drift of the third molar as it
erupts.

Halderson, Higgins, Lehman and Smith agree that the optimal
timing of the extraction of the second molar is when the crowns of
the third molar are fully formed but before any radiographic
evidence of root formation.
Cryer and Fanning believe that the optimum age for this treatment
is between 12 to 14 year and both stresses the importance of the
position of the third molars.
According to Wilson second molars should be extracted as soon as
they erupt particularly in patients with severely tipped third molars.
The third molars should be observed for 6 to 12 months for possible
spontaneous correction.
Rix suggested that the optimal time for extraction is as soon as the
second molars erupt provided the mesial angulation of the 3rd molar
is not greater than 45°. www.indiandentalacademy.com

Liddle on the other hand advocates early diagnosis and possible
enucleation of the second molar (8-12 year). He notes that third
molar would erupt by 13 years of age and are in occlusion by 14
years.
Breakspear recommends not extracting second molar if the roots of
the 3rd molars are half formed even if the latter have a favorable
angulation.
In summary, the consensus of opinion in both anecdotal and
quantitative reports is that the optimal time of the second molar
extraction, is as soon as it erupts if the third molar crown is
complete, but before radiographic evidence of root formation, the
angulation of the third molar bud plays a crucial role in the
extraction decision.

Tulley believes that extraction of the second molar (both
maxillary and mandibular) may minimize the deterioration of the
incisor alignment which tends to occur in the middle and later
teens period.
Goldberg also referred to the extraction of the upper second molar
when more space is required to get the first molar in Class I
relationship and to avoid impaction of the third molar.
Reid believed that this procedure causes decrease in the overbite,
while premolar extraction tends to deepen the bite. He also
suggested that a mesial exial angulation of the first molar is a
favorable diagnostic factor when contemplating second molar
extraction.


Removal of maxillary second molars instead of the premolars has
been proposed by Graber for the correction of Class II div I in
conjunction with extra oral appliances. In these cases the second
molars are extracted and a lower fixed lingual arch is placed with
occlusal rest on the mandibular 2nd molars until the maxillary
third molars erupt and are on contact. Graber's rationale for this
therapy is that only as much space as is required need to be used
with the subsequent mesiovertical eruption of the maxillary third
molar filling the gap. Graber believes that growth increments
during therapy partly reduce the requirements for distal
movements and that root movement requirements of the
maxillary incisor do not appear to be as great with first premolar
extraction.

According to Graber, 3 criteria should be met before this
treatment is employed;
a.

There should be excessive inclination of the maxillary
incisors with no spacing.

b

Overbite must be minimal or negative and

c.

Third molar should be present and in a good position to
erupt.

Goldberg also referred to the extraction of the upper second
molars when more space is required to get the first molars in
Class I relationship and to avoid impacting of the third molars.

Third molar extraction.
The influence of the third molars on the alignment of the anterior
dentition is controversial. There is no conclusive evidence to
indict the third molars are being a major extiologic factor in post
treatment changes in incisor alignment. The role of the
mandibular third molars in the relapse of lower anterior crowding
following the cessation of retention in orthodontically treated
patients has provoked much speculation in dental literature.
THE PRESENT CONTROVERSY
In a survey I 1971, Laskin found that the third molars sometimes
produce crowding of the mandibular anterior teeth. As a result of
such opinion as Laskin reported, the removal versus the
preservation of third molars became the subject of contention in
dental circles.

The different view range between the extreme expresses in two
different statement:
1.

Third molars should be removed even on a pryphylactic
basis because they frequently are associate with the future
orthodontic and periodontic complication as well as other
pathological condition.

2.

There is no scientific evidence of a cause and effect
relationship between the presence of third molars and
orthodontic and periodontic problems.

Third molar are teeth that are most often congenitally missing.
Estimates of the percentage of the persons with one or more third
molars missing range from 9% to 20%.

The average age for third molar crypt formation is 7 years. Its
earliest occurrence was reported at 5 years and its latest at 15years.
Bjork identified three skeletal factors that are separately influencing
third molar impaction.
1.

Reduced mandibular length measured as the distance from
the chin point to the condylar head.

2.

Vertical direction of condylar growth as indicated by the
mandibular base angles.

3.

Backward-directed eruption of the mandibular dentition
determined by the degree of alveolar prognathy of the lower
jaw.

In a case study of Jensen, there was more crowding in the quadrant
with a 3rd molar present than in the quadrant with a 3rd molar
missing. There was a mesial displacement of the lateral dental
segments on the side with the third molar in the mandibular arch,
but not in the maxilla.
Bergstrom and Jenson concluded that the presence of a third molar
appeared to exert some influence on the development of the dental
arch, but not to the extent that would justify either the removal of
the tooth germ or the extraction of the third molars.


Third molar enueleation at the age of 8 years has been practiced in
England since 1936 by Henny and Morant.
There are 3 major areas of economic concern in the third molar
extraction:
1.

Can the cost of the routine removal of the third molars as a
preventive procedure be justified?

2.

What are the risk and cost involved in the routine use of
general anesthsia?

3.

What are the added cost of hospitalization?


Pathological changes associated with third molars according to
Lilly can be divided into two categories.
1.

Those associated with erupted or partially erupted third
molars (caries, periodontitis and other inflammatory
condition, malcocclusion etc).

2.

Those associated with un erupted or impacted teeth
(follicular cyst, neoplasia).


A report presented by National Institute of Dental Research, 1979,
stated;
Crowding of lower incisor in produced by many factors which
include tooth size, tooth shape, narrowing of the inter canine
dimension, retrusion of incisors and growth changes occuring in
the adolescent stage of development. Therefore, it was agreed that
there is little rationale based on the present evidence for the
extraction of the 3rd molar solely to minimize present or future
crowding.
Orthodontic therapy in both maxillary and mandibular arches may
require posterior movement of both first and second molars by
either tipping or translation which can result in the impaction of
the third molars. To avoid impacting third molars and to facilitate
retraction procedure.

ORTHODONTIC CONTRA INDICATIONS FOR
EXTRACTION OF THIRD MOLARS.
From an orthodontic stand point clinicians should attempt to
persuade both the general practitioner and the oral surgeon to
postpone the decision for the removal of third molars in the patients
with malocclusion until the orthodontic treatment plan is completed.
Certain situations need special attention
When mandibular first premolars are extracted or one congenitally
missing. If the orthodontic treatment plan calls for closure of the
available space in the lower arch and no extraction approach in the
upper arch, then the first molar relationship will become Class III.
The maxillary second molar will have little or no occlusal contact
with the opposing tooth that is the madibular second molars. The
preservation and proper alignment of the mandibular third molars
will allow them to interdigitate with the maxillary second molar.

When the orthodontic treatment plan calls for extraction of first or
second permanent molars, particularly in the non-growing persons
with Class II malocclusion or open bite tendencies.
When the first or second molars have been extracted because of
extensive caries and periapical involvement. In any situation
which extraction of first or second permanent molars is
considered, it is important to evaluate the size and morphology of
the un erupted third molars by taking periapical radiograph before
the extraction are recommended. One has to recognize that the
presence of normally developed third molar does not
automatically mean that the tooth will erupt into the line of
occlusion.

Conclusion.
The influence of the third molars on the controversial. There is
no conclusive evidence to indict the third molars as being the
major etiologic factor in the post treatment changes of incisor
alignment.


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