Travess1 D Roberts Harry2 and J Sandy3

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Extractions in orthodontics remains a relatively controversial area. It is not possible to treat all malocclusions without taking out any teeth. The factors which affect the decision to extract include the patient's medical history, the attitude to treatment, oral hygiene, caries rates and the quality of teeth. Extractions of specific teeth are required in the various presentations of malocclusion. In some situations careful timing of extractions may result in spontaneous correction of the malocclusion.

ORTHODONTICS

1.

Who needs

orthodontics?

2.

Patient assessment and

examination I

3.

Patient assessment and

examination II

4.

Treatment planning

5.

Appliance choices

6.

Risks in orthodontic

treatment

7.

Fact and fantasy in

orthodontics

8.

Extractions in

orthodontics

9.

Anchorage control and

distal movement

10. Impacted teeth

11.

Orthodontic tooth

movement

12. Combined orthodontic

treatment

1Senior Specialist Registrar in Orthodontics; 3Professor of Orthodontics, Division of Child Dental Health, University of Bristol Dental School, Lower Maudlin Street, Bristol BS1 2LY; 2*Consultant Orthodontist, Orthodontic Department, Leeds Dental Institute, Clarendon Way, Leeds LS2 9LU Correspondence to: D. Roberts-Harry E-mail: [email protected]

1Senior Specialist Registrar in Orthodontics; 3Professor of Orthodontics, Division of Child Dental Health, University of Bristol Dental School, Lower Maudlin Street, Bristol BS1 2LY; 2*Consultant Orthodontist, Orthodontic Department, Leeds Dental Institute, Clarendon Way, Leeds LS2 9LU Correspondence to: D. Roberts-Harry E-mail: [email protected]

Refereed Paper doi:10.1038/sj.bdj.4810979 © British Dental Journal 2004; 196: 195-203

The role of extractions in orthodontic treatment has been a controversial subject for over a century. It is fair to say that even today, opinion is divided on whether extractions are used too frequently in the correction of malocclusion.

Angle1 believed that all 32 teeth could be accommodated in the jaws, in an ideal occlusion with the first molars in a Class I occlusion, ie with the mesiobuccal cusp of the upper first molar occluding in the buccal groove of the lower first molar. Extraction was anathema to his ideals, as he believed bone would form around the teeth in their new position, according to Wolff's law.2 This was criticised in 1911 by Case who believed extractions were necessary in order to relieve crowding and aid stability of treatment.3

Two of Angle's students at around the same time but in different countries considered the need for extractions in achieving stable results. Tweed became disappointed in the results he was achieving and decided to re-treat a number of patients who had suffered relapse following orthodontic treatment (at no further cost) using extraction of four premolar units.4

The demonstration of his results to the profession in America resulted in a change of philosophy in the 1940s to extraction-based techniques. Begg, in Australia, studied Aboriginal skulls and noted a large amount of occlusal and more importantly interproximal wear.5 He argued that premolar extractions were required in order to compensate for the lack of interproximal wear seen in the modern Australian dentition, through lack of a coarse diet. He also developed a technique that relied on extractions to create much of the anchorage needed for treatment.

Recently, the extraction debate has reopened, with some individuals believing that expansion of the jaws and retraining of posture can obviate the need for extractions and produce stable results. These claims are for the most part unsubstantiated. If teeth are genuinely crowded as opposed to being irregular then arch alignment can be achieved by one of the following:

• Enlargement of the archform

• Reduction in tooth size

• Reduction in tooth number

Arch expansion can be achieved by moving teeth buccally and labially (ie lateral and anterio posterior expansion) but the long-term stability and whether bone grows as teeth are moved through cortical plates remain contentious issues. In the maxilla there is a suture which remains patent in some patients into the second decade. This can also be used in expansion in that it can be 'split' with rapid maxillary expansion. The split suture fills in with bone and thus a wider arch to accommodate teeth is created. There is no good evidence that this method of expansion produces a more stable result than any other method. Longitudinal studies provide useful guidance on whether arch expansion produces stability. These are difficult studies to conduct but increasing mandibular length to accommodate teeth relapses in nearly 90% of cases with resulting unsatisfactory anterior tooth alignment.6

Reduction in tooth size, particularly in the labial segments with interdental stripping, is another potential mechanism to relieve crowding. Variable relapse has been reported but one study noted relapse of some degree in all cases.7

This work was done over 25 years ago and does not reflect contemporary use of inter-dental enamel reduction or current retention regimes.

The reduction in tooth number is usually achieved with extractions and these cases ideally need to be compared with treated non extraction cases with spacing, cases treated by arch expansion to accommodate crowding and untreated normal occlusions. In a review of these issues it was concluded that arch length reduces in most cases, including untreated normal occlusion. Any lateral expansion across the mandibular canines decreases after treatment but this is also seen in those cases which have no orthodontic treatment. It was further recognised that mandibular anterior crowding is a continuing phenomenon seen in patients into the fourth decade and likely beyond.8 The degree of anterior crowding seen at the end of retention is variable and unpredictable.

Proffit9 in a 40-year review of extraction patterns showed 30% of cases were treated with extractions in 1953, 76% in 1968 and 28% in 1993. He suggested the decline in extractions since 1968 was because of concern over facial profile, tempromandibular joint dysfunction (TMD) and stability; the change from the Begg appliance, largely an extraction-based technique to the straight wire technique, which seems to require fewer extractions. The latter may also result with a change in mindset and the use of headgear and prolonged retention.

A dogmatic approach is inadvisable and each case must be assessed on its merits. Some cases, especially where the crowding is mild may not need tooth removal, and a more sensible approach based on the requirements of the individual case rather that the two extremes seen in the past century is advised. Interestingly, in a follow up study over a 15 year period in

Fig. 1 Illustration of a macrodont tooth in the lower labial segment, which also exhibits a talon cusp. Alignment and arch co-ordination is hindered by the size of the tooth and the talon cusp. Some enamel reduction can be undertaken to reduce the width of the tooth but care must be taken not to breach the enamel. In the upper arch, reduction of a talon cusp can help correct an increased overjet, although radiographic examination of pulp chambers in the talon cusp is essential

Scotland, orthodontics replaced caries as the commonest reason for extraction in patients under 20 years of age.10 All extractions are traumatic as far as the patient is concerned and clinicians will seek non-extraction solutions where possible. In the late mixed dentition, between 3 mm and 4 mm of space can be preserved in the lower arch by simply fitting a lingual arch. If this is coupled with molar and premolar expansion of just 2 mm (with no lower canine exapansion) and interdental enamel reduction between anterior contact points then a large proportion of otherwise 'crowded' cases can be treated without the loss of permanent teeth. The decision on whether or not to extract teeth is based on an assessment of many factors including crowding, increase in overjet, change in arch width, curve of Spee, anchorage requirements and other more esoteric factor such as adjusting the torque of the anterior teeth. It is also worth mentioning that the concept of space analysis is probably underused in the United Kingdom, but this is routinely applied elsewhere. This analysis enables a rationale and methodical approach to treatment planning before extractions are recommended.11 It is important then to realise that there are a variety of options as far as mild to moderate crowding cases are concerned.

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