Extraction in orthodontics

Mustapha assad mohammed&

Muna shehab ahmed

Extractions• Before planning the extraction of any permanent teeth it is important to ensure that all

remaining teeth are present and developing in a satisfactory position. The factors governing the choice of teeth for extraction include the following:

1) Prognosis.

2) Position.

3) Amount of space required and where. Provided that relief of crowding only is indicated, the following is a general guide: 1–2 mm per quadrant, first pre-molar extractions should be avoided and a specialist opinion sought; 3–5 mm per quadrant, often indicates premolar extractions; more than 5 mm per quadrant, extractions and space maintenance, or even the extraction of more than one tooth per quadrant, may be necessary.

4) The incisor relationship.

5) Anchorage requirements and desired buccal segment relationship at the end of treatment.

6) Appliances to be used.

7) Patient's profile.

• If extractions are required in both arches, forward movement of the buccal segments to close space spontaneously will be facilitated if the same tooth is removed in both the maxilla and the mandible

• The position of the tooth being extracted within the arch will affect the anchorage balance between the teeth anterior and posterior to the extraction site. This means that extraction of first premolars will give greater space for alignment and/or retraction of the incisors than extraction of second pre-molars, which in turn provides more space than extraction of first molars, and so on.

In patients with excessive incisor protrusion, retracting the incisors improves facial esthetics. This young woman sought treatment because of dissatisfaction with the appearance of her teeth. After orthodontic treatment with premolar extraction and incisor retraction, dental and facial appearance were significantly improved. A and B, Appearance on smile before and after treatment. C and D, Profile before and after

Contemporary Extraction Guidelines• Less than 4 mm arch length discrepancy: 1. Extraction rarely indicated (only if there is severe incisor protrusion).2. In some cases, this amount of crowding can be managed without arch expansion

by slightly reducing the width of selected teeth, being careful to coordinate the amount of reduction in the upper and lower arch.

• Arch length discrepancy 5 to 9 mm: 1. Nonextraction or extraction treatment possible.2. The decision depends on both the hard- and soft-tissue characteristics of the

patient and on how the final position of the incisors will be controlled; any of several different teeth could be chosen for extraction. Nonextraction treatment usually requires transverse expansion across the molars and premolars, and additional treatment time if the posterior teeth are to be moved distally, to increase arch length.

Contemporary Extraction Guidelines

•Arch length discrepancy 10 mm or more: Extraction almost always required.For these patients, the amount of crowding virtually equals the amount of

tooth mass being removed, and there would be little or no effect on lip supportand facial appearance.

The extraction choice is:1. four first premolars 2. or perhaps upper first premolars and mandibular lateral incisors.3. Second premolar or molar extraction rarely is satisfactory because it does not

provide enough space near crowded anterior teeth or options to correct midline discrepancies

Incisors• Extraction of a lower incisor tends to result in lingual tilting of the

remaining lower labial segment teeth and a reduction in intercaninewidth, which will produce an increase in overbite and often an increase in crowding, particularly in a growing child.

• Occasionally, if the lower canines are distally inclined and the lower labial segment crowded in a child who refuses fixed appliance treatment, an acceptable compromise can be reached by extraction of one or two lower incisors. If a lower incisor is excluded from the arch, its extraction may result in satisfactory alignment, but often a sectional lower fixed appliance is indicated to achieve good root paralleling.

• Upper incisors are rarely the teeth of choice for extraction, but where trauma or morphology have reduced their prognosis, or an incisor is grossly displaced, there may be no alternative.

Canines• Because of their position as the cornerstone of the arch, canines are

usually only considered for extraction if they are:• severely displaced and/or crowded out of the arch. Occasionally, in cases

with severe crowding, the first premolar erupts into contact with the lateral incisor. This can be aesthetically acceptable ,which is a great bonus, particularly in the upper arch, as the canine is broader than the first premolar and extraction of the latter alone would not provide sufficient space for alignment of the former.

• However, the occlusion should be checked to ensure that no displacing contacts are present on lateral excursions. Otherwise, fixed appliance therapy is usually required following removal of a canine to achieve a satisfactory contact between the lateral incisor and the first premolar.

(a)Result following removal of displaced lower canine

(b)patient who had both upper palatallydisplaced canines extracted.

A B

First premolars• First premolars are the teeth of choice for relief of moderate to severe crowding in

either arch.• By virtue of their position within the arch, extraction of the first premolars

provides space for alignment and retraction of the labial segments, as well as relief of buccal segment crowding.

• Extraction of a first premolar in either arch usually gives the best chance of spontaneous occurrence of acceptable alignment.Also, if space closure is complete, a good contact between the canine and first premolar can often be achieved. This is of particular value in the lower arch where, provided that the canine is mesially inclined, spontaneous alignment of the lower labial segment may occur. This is most rapid within the initial 6 months following extraction.

• If the canines are distally inclined, they will not upright spontaneously into the extraction space and fixed appliances will be required for their retraction.

(a)–(c) Class I malocclusion with moderate upper and lower crowding, treated by extraction of all four first premolars; (d)–(f) occlusion a year after extractions.

B

A

C

D

E

F

First premolars• In the upper arch the first premolars usually erupt prior to the

maxillary canine and maximum spontaneous improvement in the position of this tooth can be achieved if the first premolar is extracted just before its emergence. However, if space is at a premium, a space maintainer should be fitted first.

• If the crowding is mild, extraction of first premolars may result in residual spacing. If fixed appliances are then used to close the remaining space, there is a danger of over-retracting the labial segments, which may have deleterious effects upon the profile. In cases with mild crowding, consideration should be given to extracting teeth further distal in the arch

Residual spacing in a patient with mild crowding who had all four first premolars removed

Second premolars• The indications for extraction of second premolars include the

following:1. congenital absence of the second premolars and crowding of the

arch;2. hypoplasia of the second premolars and crowding of the arch;3. severe displacement of the second premolar;4. mild to moderate crowding (2–4 mm per quadrant);5. where space closure by forward movement of the molars rather

than retraction of the labial segments is indicated.

Second premolars• Extraction of the second premolars is preferable to

extraction of the first premolars in cases with mild to moderate crowding as their extraction alters the anchorage balance, favouring space closure by forward movement of the molars.

• In order to facilitate this and to ensure a satisfactory contact between the first premolar and the first molar, fixed appliances are required, particularly in the lower arch.

First permanent molars

• First permanent molars are never an orthodontist's first choice. However, their extraction may be indicated if their prognosis is compromised to such an extent that they are unlikely to last for a reasonable time.

Second permanent molars• Indications for extraction of second permanent molars include the following:

1. facilitation of distal movement of the upper buccal segments;2. relief of mild lower premolar crowding;3. provision of additional space for the third permanent molars and thus reduction

of the likelihood of their impaction;4. prevention of lower labial segment crowding.

• Because of the greater tendency for mesial drift in the upper arch, extraction of second permanent molars will not provide space for the relief of premolar or labial segment crowding without using appliances

Extraction of second molars allowedspontaneous relief of anterior crowding, with early eruption of the third molars

Third permanent molars• Early extraction of these teeth has been advocated in

the past to prevent lower labial segment crowding. However, most oral surgeons are now unwilling to remove symptomless wisdom teeth. Research into the role of the third permanent molar in lower labial segment crowding has not demonstrated a clear-cut case of cause and effect. Studies have shown that patients with absent third molars are less likely to exhibit crowding, but are also likely to have smaller teeth than average.

Serial extractionsSerial extractions were introduced in the 1940s to treat Class I malocclusion complicated by severe labial segment crowding. The aim was to spontaneously guide the developing dentition into good alignment without the use of appliance treatment by selectively timing deciduous and permanent tooth extractions.

The disadvantages of the procedure include:• Extractions may require multiple procedures under general anaesthesia and are a stressful experience for the patient.• Early loss of the first deciduous molar may result in mesial drift of the buccal segments with further space loss.• The lower canine may still erupt into the first deciduous molar space before the first premolar resulting in first premolar impaction.• There is no spontaneous correction of an incorrect incisor relation-ship, hence it is only useful in Class I cases.• There is a risk of lower incisor retroclination and deepening of the overbite.• Patients may still require later appliance treatment.Serial extraction is rarely undertaken in its classically described form because of the disadvantages stated above and the current wide availability of fixed appliances. Occasionally, a modified version of the procedure may be carried out (e.g. extraction of deciduous canines to allow alignment of the incisors or for interceptive treatment of palatal maxillary canines) to simplify later appliance treatment.

• Balancing extraction:Extraction of a contralateral tooth during the mixed dentition to minimise a shift of the dental centreline

• Compensating extraction:Extraction of an opposing tooth during the mixed dentition to prevent its over-eruption and to maintain occlusal relationships between the arches