Extraction in orthodontics

*Historical review.*Reasons for Extraction. *Factors determining the needs for extraction.*Analysis made to determine whether to extract or not.*Determination of space needed for alignment of teeth.*Controversy regarding the effects of extraction.*Factors considered in chosen the teeth for extraction.*Choose of tooth for extraction.*Compensating Extraction.

Historical review

The role of extraction in orthodontics was recognized by John Hunter “1771” in his natural history of the teeth.

Spooner “1839” advised the extraction of four premolars or first molars when defective.

Pierce writing in the Dental cosmos of October “1859," advocated extraction in teeth crowding as a mean for simplifying orthodontic procedures.

In “1887” Angle wrote on his new system to regulate and retain the teeth. He stated that, if the teeth were placed in their proper occlusal relationship, normal function would be developed the supporting bone to hold them in this position. In that same year, the first edition of his book, on the same subject was published. Other editions supposedly followed up to “1897” when the fifth edition, expanded in scope, came out.

Farrar “1888” Considered Judicious extraction an essential request for the prevention and correction of irregularities.

In “1896” Calvin case published an article regarding the need for extraction to correct facial deformities.

Angle “1900” in the sixth edition of his book “Malocclusion of the teeth “describes extraction for the relief of crowding and in the treatment or various types of Malocclusion.

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In a “1902” article, Angle set forth his line of reasoning toward the development of his treatment philosophy. In this article, Angle states “that my belief is that if we would confer the greatest benefits upon our patients from an aesthetic standpoint we must work hand in hand with nature and assist her to establish the relations of the teeth as the Creator intended they should be, and not resort to mutilation .

In “1903” Case published an article in which he takes issue against the injudicious extraction of permanent teeth.

Ottlengui in “1905” stated that, in an article published in “1907” in items of interest, by this time one might almost say that the question of the hour was to extract or not? Many orthodontists were arguing that extraction is almost a crime and even a new word was coined for those who ruthlessly remove sound teeth from so called crowded arch, and we heard much of odontocides. On the other hand men long counting as experts in this branch of work still argued that often either for reason of expediency or for actual benefit to the physiognomy, extraction was permissible and even advisable.

A cothinker and supporter of Case, Matthew Cryer also published an article in “ 1905 “ in which he defends the use of extraction.

In “1907” the seventh edition of Angle’s book was been published which was been completely stripped of all extraction case materials present in the sixth edition. In this edition, Angel’s has been said that extraction plays no part in orthodontic treatment, on the basis that if crowded teeth are aligned in correct relation to each other, the improved function of the masticatory system will result in growth of the jaws, which in turn will create adequate space for the dentition. Since then he has always been considered the leading exponent of non extraction technique . Thus , the major concept of orthodontic in these early years was one of the expansion outward to a greater arch to eliminate individual teeth irregularities .

In the Extraction Debate of “1911," at this “1911” meeting of the National Dental Association Calvin, Case presented an article entitled the question of extraction in orthodontic. In this article he discusses the causes as he believes it is intimately bound up in the discussion of extraction. He claims that the writings of the “new school” (Angle) say that the causes of malocclusion are “local “, whereas Case claims that they “partly at least, arise from the law of heredity and from other laws that govern the development of plants and animals, and especially to laws that govern the mixture of dissimilar types.

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This is not the first time that Case queried this line of thinking. In 1905 he wrote, “But why enter such a field of doubt, of danger, and of possible failure, merely to satisfy a sentiment that God does not make the mistake of placing in the mouth of the human individual more teeth than is necessary for perfect harmony in all physical and aesthetic relations? Why ignore the possibility and the frequent undoubted fact that inherited inharmonious in contiguous structures over which we have no control made it impossible for us to place all of the teeth in the arch without fulfilling the designs of an inherited deformity. In my humble estimation it should be the highest aim of the orthodontist to remove without hesitation such portions of those naturally produced anatomical disharmonies as are within his reach, and which characterize the principal deformity, instead of attempting to carry out in so limited a degree the original designs of the Maker when he fashioned an Apollo. “(The Apollo reference her is a very sophisticated thrust at Angle whose concept of beauty was based on this statue.).

On other area of controversy between Case “rational school “and Angle’s ”new school“. Angle’s group believed that bone could be induced by mechanical means to grow beyond its inherent size, especially the mandible. Case’s group believed otherwise. In this area Case wrote that “The correctness of the statement that the mandible will grow to a harmonizing size will depend entirely upon whether it has been stunted in normal growth development, which is quietly improbable, unless we assume the absurdity that the same cause at the same time produced the over-development of the upper jaw. Malrelations of this character point directly to heredity.

It is more than likely that Charles Tweed was familiar with Case’s concept of extraction because Tweed was extremely unhappy with the faces he was producing. The idea of treating cases again with extraction formed the basis of his further work, which leads to the formulation of what is become known by Tweed philosophy.

Reasons for Extraction

1- Crowding When the dental arch is too large to fit in the basal arch without irregularities

it is necessary to decrease the size of the dental arch by reduction of the number of the teeth.

N.B : There are a different methods of gaining space including, stripping and expansion but mainly they applied for mild crowding with many limitation in its uses. However the subject of this review is the extraction.

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2- Anteroposterior dental arch malrelation

As in crowding it is necessary to remove teeth to give space for correction of discrepancies in dental arch relationship. This applied particularity in the Class II D.1 when the upper arch is too far forward in relation to the lower dental arch. The backward movement of the upper anterior teeth require the removal of a teeth to provide spaces.

Factors determining the needs for extraction

1-Gonial angle :-Incisor procumbency in relation to the FH plane is more pronounced in the presence of short ramus and an extremely obtuse gonial angle.2-Axial inclination of mandibular incisors.3-Type and degree of crowding.4-Direction of jaw growth.5-Difference in the basal arches length.6-Age of the patient.7-Thickness and distribution of the soft tissues covering the facial bones.

Analysis made to determine whether to extract or not

I-Arch analysis II-Cephalometric analysis

I- Arch analysis

·Bolton tooth ratio analysis

This analysis aimed to estimating the overjet and overbite relationship that will obtained after treatment is finished. This analysis also show the effect of extraction on posterior occlusion. When one is contemplating the extraction, it is useful before selecting the teeth for extraction, to ascertain the effect of extraction on the ratio designed by Bolton. Care must be taken in the uses of this analysis, since Bolton’s formula do not take into account the incisors angulation.

·Howe’s analysis

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Howe’s considered teeth crowding to be due to deficiency in basal arch width and length “ BAL”.

The BAL

Tooth material should be 37% , if it less than 37% he considered that is

due to basal arch deficiency necessitating extraction of first premolars. The premolar basal arch width should equal approximately 44% of mesiodistal width of the 12 teeth anterior to the second molar if the basal arch is sufficient large to accommodate all of the teeth. Case between 37- 44% may require extraction of first premolar. When the premolar basal arch width is larger than the premolar width at the cuspal region, than the basal arch is sufficient to allow expansion at the premolars. This permit arrangement of crowded anterior teeth in more regular manner.

·Kesling diagnostic setup

The teeth are cut from the cast at the level of A and B points then repositioned according to Tweed formula “ FMIA = 65o ” . This method determine the followings:-

-If the case is indicated for extraction or not and aid in choosing the teeth to be extracted.

- The amount of the space created, by extraction and the tooth movement necessarily to close the space.

- It is best mathematical representation of the problem during the mixed dentition.

- Help in determine the type of anchorage, either minimum, moderate or maximum anchorage.

·Harvold symmetrograph

The symmetrograph is a transparent plastic device with an inscribed grid . The midline of symmetrograph is superimposed over the median palatine raphe. This quickly give us information about the followings :-

- Arch asymmetry .- Drifted, tipped and rotated teeth. - Also it is useful in planning individual tooth movement and determination of appliance design .

·Peck and Peck analysis

Many studies indicated that deviations of crown shape influence and contribute to the mandibular incisor crowding . Peck and Peck construct an index

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using the mesiodistal and faciolingual dimensions in the form of a mesiodistal ( MD) over faciolingual ( FL )ratio. The index equals the MD crown diameter in millimeters divided by the FL crown diameter in millimeters and multiplied by 100. They also adapted numerical ranges as clinical guidelines for the maximum limit of desirable MD, FL index values for the lower incisors : 88 - 92 for the mandibular central incisors and 90 - 95 for the mandiblular lateral . Lower incisors within or below the ranges must be considered favorably shaped for good alignment. Any lower incisor with an MD/FL index above these ranges , however, possesses a crown shape deviation which may influence or contribute to the crowding phenomenon. It can be seen, therefore, that reaproximation can function as an exacting procedure to correct deviations of the mandibular incisor tooth shape and to help achieve post-treatment stability. The minor correction require removing 2 mm. from each side.

II-Cephalometric analysis

a) Tweed method

Tweed considered that, the lower incisors should be uprighted over the basal bone to achieve harmonious and symmetric occlusal and facial balance and to gain a stable result.

When the teeth in the dental arch can’t be placed into regular alignment without increasing the axial procumbency of the incisors, it become necessary to reduce the number of the teeth to be accommodated in the arch.

Tweed diagnostic facial triangle :-It is the basis for diagnosis, treatment planing and prognosis. It consists of

the following :FMA (FH-MP) = 25o .

IMPA (1

-Mp) = 90o .

FMIA (1

-FH) = 65o .

* Roles of FMA in determining the need for extraction :-

1-When the FMA = 20 30o o , the correct position of 1

vary from 95o when

FMA = 20o to 85o when the angle is increased to 30o . The prognosis vary from excellent for those nearest the 20o to good for those nearest the 30o . When the FMA is below 20o the aim should not to exceed the IMPA over 92o .The FMIA should be upward of 70o .

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2- When the FMA = 30 35o o , the correct position of 1

vary from 85 80o o .

The prognosis for reducing the alveodental progonathism varies from good to those nearest 30o to fair to those nearest 35o .

3- When the FMA = 35 40o o , the prognosis for reducing the alveodental progonathism varies from fair at 35o and unfavorable at 40o .

4- When the FMA is over 40o the prognosis is extremely unfavorable. In some cases, the removal of the teeth in 40o or more FMA detracts from father than enhance facial appearance.

Tweed’s formula for treatment is given as follow :-1- Non extraction - FMIA = 65o or grater and sufficient arch length.2- Borderline - FMIA = 62o - 65o with sufficient arch length.3- Extraction - FMIA = 62o or less.

b) Stiener analysis

He relate the lower incisors to NB line and use a linear measurement of 4 mm and angular measurement of 25o .

He uses the “ rule of thumb “ that one-third of the space is lost and that every degree of distal or mesial movement of the lower incisors represents the 2.5 mm .In liner movement.

Steiner bases his decision regarding extraction of teeth upon number of factors; the discrepancy between space available and space required the amount of room for expansion and its maintenance; the distance mesially of distally which he must position the lower incisor to achieve his concept of a well-balanced face; the possibility of relocation of the lower first permanent molar the possibility of utilizing any of the space left by the exfoliation of the second deciduous molars; the amount of space consumed by the use of intermaxillary elastics during treatment; and the space which might be gained through extraction of teeth. A combination of these factors and their net results determine whether or not extraction is indicated.

c) Holdaway analysis

He has proposed that the lower incisor and pogonion be related to each other by the reference to the line NB : both are liner measurement expressed in mm . The ratio of this measurement to each other , and not their value , is important . Anything within 2 mm. of an equal ratio is in very good facial balance. If the ratio is off 3 mm., Holdaway will tolerate it ; if there is a 4 mm. difference, he extracts to return to the 3 mm. variance.

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Determination of space needed for alignment of teeth (Yamaguchi )

1. On the dental cast determine the amount of space needed to align the teeth without crowding on the basal arch. This is calculated as follow :-

Difference between teeth material - Arch length = Amount of crowding

2. Curve of spee

Right Left

2

0 5. = Amount of space needed for leveling the curve of

space.

3. The Tweed formula for correction of the angulation of 1

denoting that for

every 1 degree retraction of the lower incisors require 0.8 mm space.

Controversy regarding the affects of extraction

There are a great controversy about the effect of extraction on the lower anterior face height, soft tissue profile and TMJ. These will be discussed as follow:-

1-Lower anterior face height and mandibular position

Many orthodontists agree that nonextraction treatment is associated with downward and backward rotation of the mandible and an increase in the lower anterior face height. They also agree that extraction treatment is associated with upward and forward rotation of the mandible and a decrease in the lower anterior face height.

Many orthodontists also believed that extraction permits the posterior teeth to move forward resulting in decrease in the vertical dimension of occlusion. The mandible is then allowed to overclose which in turn reduce the facial vertical dimension, particularly the lower anterior face height

Schudy, among other, recommended a nonextraction approach in the treatment of the hypodivergent facial type and an extraction approach in the treatment of hyperdivergent facial type. He also advocated extraction of teeth to close down the bite

Pearson, also recommended extraction of premolars in patients with large anterior facial height and a steep mandibular plane, even when dental and skeletal

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discrepancies are deemed to be mild, in the belief that mesial movement of molars may allow anterior rotation of the mandible.

Klapper et al., as a result of their study, recommended the extraction of teeth in dolichofacial patient (retrognathic facial type with long lower face height ) to help control the vertical dimension. They also believed that extraction should be avoided in brachyfacial patients (prognathic facial type with short, lower anterior face height) to avoid vertical overclosure.

On the other hand Chua et al ., found that extraction, on treatment of class I and class II malocclusion, was not associated with any change in the lower anterior face height ( ANS-Me). While the nonextraction treatment is associated with downward and backward rotation of the mandible (N-Me).

Staggers, in his study on the treated class I cases found that an increase rather than decrease of the lower anterior face height either with or without extraction of premolars. He also found a slight increase in the mandibular plane angle and extrusion of the maxillary and mandibular first molars. In class II or III cases in which a portion of extraction space is closed by forward movement of molars, the overclosure of the mandible with the subsequent reduction of the vertical height is suspected. Staggers, her considered loss of the vertical height is difficult to occur, since the extrusion of molars , that mostly accompany the orthodontic mechanic, will compensate for the forward movement of molars.

2- Soft tissues

Orthodontists have long recognized that the extraction especially the premolar often is accompanied by changes in the soft tissues profile. At times these changes will result in improvement in the facial profile. At other times, extraction can lead to what is sometimes called the “ Orthodontics look “ or “ dished - in “ profile. For this reason , there has been a tendency to avoid extraction of premolar wherever possible and, in some cases, to extract second rather than first premolars.

Lo and Hunter studied the nasolabial angel changes that occurred in the treated Class II,Division 1 malocclusion. The patients had a minimum of 3 mm. upper incisor retraction at treatment completion. They summarized the followings:- 1-The nasolabial angel increased with the increase in the maxillary incisor retraction.The mean ratio of increase was 1.6 degrees to 1 mm. 2-There was a strong and significant correlation between the change in the nasolabial angel and the increase in lower face height. The average ratio of increase was 2.2 degrees to 1 mm.

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3- The response of the nasolabial angel from the extraction group was not significantly different from that of the nonextraction group.

Looi and Mills, studied the effect of extraction versus non extraction on the soft tissue profile. They concludes:-1. Following retraction of upper incisor teeth in class II, Division 1 malocclusion, the upper lip drops back to a certain extent and it’s probably desirable in most cases. Where the incisors are retracted excessively, the lip do not fall back to a corresponding extent and any further dropping back may be more associated with backward movement of point A and therefore removing support from the base of the lips. 2. Retraction of the lower incisors has more effect on the lower lip, which seems to follow the incisors closely. Although in some cases this may be desirable, in many cases it is not and retraction of the lower incisors should be avoided.3. The reduction of overjet has the effect of “ uncurling “ both lips; this enables them to be held together without undue effort.4. There is a wide individual response in the reaction of the soft tissues to change in the underlying hard tissues; it is not possible to predict the effect on the lips of a given movement of the teeth.

Talass etal, analyzed the soft tissue profile change that result from retraction of maxillary incisors at minimum of 3 mm either with or without extraction. The result of this study summarized as following:-1. The upper lips were retracted “ mean 3.7 “ .2. The Anteroposterior position of the lower lip seem to be unchanged.3. Increased nasolabial angle by mean of10 5. ·

4. Decrease of interlabial gap by about 2.4 mm .5. Increased lower lip length by mean of 3.4 mm .6. Increase upper lip thickness by mean of 2.3 mm .7. Increase the soft tissue lower face height.

They considered three measurements that were of clinical significance , this measurements are the upper lip retraction, the lower lip length and the increase in the labiomental angle .

Drobocky and Smith examined the change in the facial profile during orthodontic treatment with extraction of four first premolars. They concluded that the negative effect of extraction on the facial profile are false. Clearly the great majority of patient exhibit controlled amount of profile change that produce improvement in facial esthetics. They also observed that there is a great individual variability in the effect of treatment on the soft tissue profile.

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Young and Smith , compare the soft tissues profile changes of extraction and nonextraction treated patients. They concluded the following :-1. On average, nonextraction patients had less facial changes as a result of orthodontic treatment than a similar group of extraction patients; the magnitude of the mean difference between extraction and nonextraction patients being approximately 6o in the nasolabial angle, 1 to 2 mm in upper lip protrusion, and 2 to 3 mm in lower lip protrusion.2. Although average changes are less in nonextraction patients, the range of individual changes in facial profile is almost as great for nonextraction cases as for extraction cases. Furthermore, the range of response by individual patients is very large; up to 60o for angular measurements of lip position and 11 to 13 mm for liner measurements of lip protrusion.3. It would seem that nonextraction cases should offer much less of an opportunity for the clinician to alter the profile. It has been vigorously argued ( and assumed ) by some that nonextraction treatment is the solution to undesirable facial changes ( and particularly the “ dished- in “ look.).

4. The facial appearance should be judged on an overall basis rather than as a series of individual features. The difference in the nasolabial angel versus the protrusion of the lips illustrates that improvements in one measurement may result in unfavorable changes in another measurement. The consequences of esthetics cannot be judged by comparing numbers

3 - TMJ

First premolar extraction is considered by many to be an etiologic factor in TMJ disorders.

Farrar and McCarthy, among others, believed that extraction of premolars during the course of orthodontic therapy are considered to be a predisposing factor in TMJ anterior disk displacement and TMJ disordered for the following reasons :-

1. Extraction of premolars permits the posterior teeth to move forward resulting in a decrease in the vertical dimension of occlusion. The mandible is then allowed to overclose, and the muscles of mastication become foreshortened. As result, TMJ problems are likely go occur. Although this theory is popular, particularly among general practitioners, no controlled study has published results supporting this hypothesis.

2. Another theory that has been proposed is that first premolar extractions lead to overretraction of the anterior teeth, particularly the maxillary anterior. This overretraction of anterior teeth is thought to displace the mandible an the condyles posteriorly. Posterior condylar displacement has long been associated with TMJ disorders. As with the previous hypothesis, this theory has not been substantiated by research.

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Kundinge, among others, were measured the anterior and posterior condylar space through the corrected axial tomogram. They had shown that,either in their cross sectional or longitudinal studies, the extraction of premolars did not affect the so called condylar positions of extraction treated subjects. Concerning the forward rotation of the mandible, as an etiologic factor in the TMJ disorders, it was mentioned previously.

Reilly et al., examined clinically the TMJ in extraction orthodontic patient before and after orthodontic treatment for the presence of the sings or symptoms of TMJ disorders. As a result of their study, they support the hypothesis that orthodontic treatment is not costive of TMJ disorders.

Beattie et al., recall 65 extraction and nonextraction border line cases to examine clinically the long term effect of orthodontic treatment on the TMJ. The mean posttreatment interval was 14 years. They found no difference between the extraction and the nonextraction cases. So they concluded that extraction decision should not be distorted by unwarranted assumptions about the long-term functional superiority of one strategy or the other.

Factors considered in chosen the teeth for extraction

a) The condition of the teeth :Fractured, hypoplastic, grossly carious teeth and teeth with large restorations

are the teeth of choice for extraction in orthodontics. Tooth condition must be balanced with other considerations of tooth position in deciding an extractions.

b) The position of teeth :The position of the tooth apex must be considered, as it is more difficult to

move the apex than to move the crown. Severely malposed teeth and which are difficult to align, are the teeth of choice for extraction.

c) The position of crowding :pleasing final appearance, occlusal balance, the final tooth position and

interdental contacts, must be considered before extraction.

Choose of tooth for extraction

First premolar “ Tulley “

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-This tooth is positioned near the center of each quadrant of the dental arch, and is therefor near the sit of crowding. For this reason, it is the tooth most commonly removed for relief of crowding.

- Extraction of the first premolar is indicated in bimaxillary protrusion case and the case of marked crowding.

- The upper first premolars extraction is indicated for treating a class II C.1 malocclusion particularly where there is a considerable overjet.

- Lower first premolars should not be extracted in class II except where the lower crowding is very sever, and the discrepancy in arch relationship is not very marked.

- In treatment of class II D. 2 malocclusion, the extraction of the upper first molar is practiced but tend to leave some residual spaces. In this cases the extraction of lower first premolar will causes further collapse to the lower incisor teeth and deep bite become traumatic to the lower anterior and palatal soft tissue.

- In class III cases, the extraction of upper first premolars should be avoided . Extraction of the mandibular first molar in these cases, in the absence of the crowding, leads to presence of residual spacing, as a result of the tongue action on the lower incisors and the growth of the mandible.

Second premolar “ Tulley and logan “

* Indications :-1. When the arch length discrepancies is 7.5 mm or less “ premolar unit “ and

no indication for incisor retraction “ Mild arch length deficiency “.2. If mesial movement of fist permanent molar is required. 3. Create space for the second permanent molar.4. Open bite closure in class I cases. 5. When less maxillary incisor retraction are needed.6. When it is badly decayed, beyond the limit of orthodontic tooth movements

or take too much orthodontic procedures.7. When the facial contour are in good balance and proportion

* Advantage :-· Less complicated mechanics .·Decrease maxillary incisors retraction.·Decrease the uses of class II elastics.

·Decrease anterior torque problem.

First permanent molar “ Tully - Jensen “

* Consideration for the first permanent molar :- 1. Considered the cornerstone of the dentition.

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2. It maintain the height of the bite. 3. Always, it is at right position in the arch. 4. It is essential tooth in orthodontic treatment .Due to the previously mentioned considerations, this tooth bas been esteemed

as untouchable from the every beginning of the history of orthodontics.

* Indication :-When the extraction of 4 first premolars with the enaculation of the third

molars does not sufficient to relief the crowding and correct the dental basal arch discrepancies.

* Requirement for first permanent molar extraction :-1. The third molars must be present in x-ray film in normal size and good

position.2. Extraction of 4 first premolars and 4 third molars causes loss of 25 % of the

teeth and also the space of third molars is more or less wasted . When the first permanent molars are extracted, all of it’s space can be used and only 12.5 % of the teeth are lost.

3. Removal of weak, restored, endodontically treated molar is much more better then the removal of intact premolar.

4. The first permanent molar should extracted before the eruption of the second permanent molars. This allow the second permanent molar to erupt in mesial direction, and the same is true for the third molar.

* Advantage of the first permanent molar extraction :-1. Anchorage problems are minimal because mesial movement of the second

permanent molars are desirable and necessary to allow the normal eruption of the third molar.

2. Patient appearance is natural and so difficult to discover that the patient has orthodontic and extraction treatment.

* Contraindication1. In case of premature loss of deciduous molars with the tendency of class III

arch relationship. The extraction of the only occluding cheek teeth may allow a postural prenormal occlusion to developed.

2. In class II D.1 malocclusion and before eruption of the second permanent molar. The extraction of first permanent molar will allow the second permanent molar to drifled mesially and occupy much of the extraction space without improving in incisal relationship.

Second molar extraction “Magness”

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* Indication :-1. where the third molar is present and of normal size and position2. In cases of open bite by temporarily reducing the molar functional area

* Advantages :-1. Less surgical trauma and decrease the possibility of precoronitis.2. Reduce the amount and duration of orthodontic treatment.3. Better esthetic reduce the probability of dished-in .4. More stability reduce the probability of relapse.5. No problem of extraction space and anterior diastema.6. Provide only amount of space needed .7. No problem in borderline cases .8. Elimination of the third molar as a possible cause of relapse .

* Contraindication :-1. Missed third molar or bicuspid .2. Sever bimaxiallry protrusion .

3. Sever anterior space deficiency .

Upper Incisors teeth

Central incisor : Extracted only when it beyond restoration .Lateral incisor : Extracted only when it severely malformed or severely

malposed e.g. palataly positioned apex .

Lower incisor”Canut”

* Indication :-1. Anomalies in the number of anterior teeth.2. Tooth size anomalies.3. Ectopic eruption of incisors .

4. Moderate class III malocclusions.

* Clinical implication :-1. An accentuated overjet is contraindication to removed of single lower

incisors.2. Removal of an incisors cause the canine to displace mesially.3. Diagnostic setup of final occlusal status must be evaluated.

4. In certain cases, and particularly among adults, the space either fails to close or else opens up with ease; visible diastema thus results in an area of considerable aesthetic and periodontal importance.

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* Advantages :- One way of preventing relapse is to extract an incisor with extreme

malpositioning, which moreover limits the sometimes unnecessary movement of many teeth; correction thus becomes more circumscribed to a specific dentition zone. The loss of gingival tissue of the disappearance of the external alveolar lamina constitutes an additional indication for extraction of the affected incisor.

Upper and lower canines

Extracted only when it beyond restoration .

Compensating Extraction

When one permanent teeth are lost early or are congenitally missing in one side, the remaining teeth may move toward the extraction space and sometimes the anterior teeth may across the midline with the subsequent asymmetry. To avoid this, a balanced extraction should be made in which teeth in the other side as removed. It is not necessarily to extract the same tooth in the other side.

The following general principles are applied when considering compensation extractions :

(1) In a class I malocclusion where there is crowding but a normal overbite and overjet, unavoidable extraction or missing teeth in one buccal segment, a compensating extraction should be made in the opposing arch to reduce the movement of the center line and to maintain the overbite.

(2)Where the overbite is excessive and there is a class II tendency, unavoidable extractions or missing teeth in the lower arch will require a compensating extraction in the upper arch but not vice versa.

(3)Where there is a class II tendency, unavoidable extractions or missing teeth in the upper arch require compensating extractions in the lower arch but not vice versa.

The aim of compensating extraction is to avoid lateral asymmetry, midline and to establish normal occlusion.

References

Bernstein, L . : Edward H . Angle versus Clavin S . Case : Extraction versus nonextraction. Part I . Historical revisionism. Am. J. Orthod. Dentofac . Orthop. 102 : 464 - 470 , 1992.

Beattie, J. R. ,Paquette, D. E and Johnston, L. E. : The functional impact of extraction and nonextraction treatment :A long term comparison in patients with “borderline,” equally susceptible Class II malocclusions. Am. J. Orthod. Dentofac . Orthop. 105 :444-449, 1994.

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Canut, J. A. : Mandibular incisor extraction : indications and long-term evaluation. European Journal of orthodontics. 18 : 485 - 489 , 1996.

Chua, A. , Lim, J. Y. S. and Lubit, E. C. : The effects of extraction versus nonextracton orthodontic treatment on the growth of the lower anterior face height. Am. J. Orthod. Dentofac . Orthop. 104 : 361 - 369 , 1993.

Daugaard-Jensen, L. : Extraction of first molars in discrepancy cases. Am. J. Orthod. 64 : 115 -136 , 1973.

Drobocky, O. B. and Smith, R. J. : Changes in facial profile during orthodontic treatment with extraction of four firs premolars. Am. J. Orthod. Dentofac . Orthop. 95 : 220 -230 , 1989.

Editorial section : On second-premolar extraction and the moderate borderline malocclusion. Am. J. Orthod. 73 : 459 - 460 , 1978.

Farrar, W. B. and McCarthy, W. L. : A clinical outline of temporomandibular joint diagnosis and treatment. Montgomery, Ala . : Walker Publishing , 1983 ; 84 - 8 . Quoted from Kundinger, K. K. , Christensen, L. V. , Donegan, S. J. and Ferguson, D. J. : An evaluation of temporomandibular joints and jaw muscles after orthodontic treatment involving premolar extractions. Am. J. Orthod. Dentofac . Orthop. 100 : 110 - 115 , 1991.

Holdaway, R. A. : A soft-issue Cephalometric analysis and its use in orthodontic treatment planning . Part I. Am. J. Orthod. 84 : 1-28 , 1983.

Jensen, I. D. : Extraction of first molars in discrepancy cases. Am. J. Orthod. 64 : 115-136, 1973.

Klapper, L. , Navarro S. F. , Bowman, D. and Pawlowski B. : The influence of extraction and nonextraction orthodontic treatment on brachyfacial and dolichofacial growth patterns. Am. J. Orthod. Dentofac . Orthop. 101 : 425 - 430 , 1992.

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