1
The rationale
for orthodontic
treatment
Chapter contents
1.1 Definition 2
1.2 Prevalence of malocclusion 2
1.3 Need for treatment 2
1.3.1 Dental health 2
1.3.2 Psychosocial well-being 3
1.4 Demand for treatment 3
1.5 The disadvantages and potential risks of
orthodontic treatment 4
1.5.1 Root resorption 4
1.5.2 Loss of periodontal support 4
1.5.3 Decalcification 4
1.5.4 Soft tissue damage 4
1.6 The effectiveness of treatment 5
1.7 The temporomandibular joint and
orthodontics 5
1.7.1 Orthodontic treatment as a contributory factor in TMD 5
1.7.2 The role of orthodontic treatment in the prevention
and management of TMD 5
Principal sources and further reading 6
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Numerous surveys have been conducted to investigate the prevalence
of malocclusion. It should be remembered that the figures for a particular
occlusal feature or dental anomaly will depend upon the size and
composition of the group studied (for example age and racial characteristics),
the criteria used for assessment, and the methods used by the
examiners (for example whether radiographs were employed).
It has been estimated that approximately 66 per cent of 12-year-olds
in the UK require some form of orthodontic intervention, and around
33 per cent need complex treatment. The results of the recent survey
of children in the United Kingdom is given in Table 1.1.
Now that a greater proportion of the population are keeping their
teeth for longer, orthodontic treatment has an increasing adjunctive
role prior to restorative work. In addition, there is an increasing acceptability
of orthodontic appliances with the effect that many adults who
did not have treatment during adolescence are now seeking treatment.
The decision to embark upon a course of treatment will be influenced
by the perceived benefits to the patient balanced against the risks of
appliance therapy and the prognosis for achieving the aims of treatment
successfully. In this chapter we consider each of these areas in turn,
starting with the results of research into the possible benefits of orthodontic
treatment upon dental health and psychological well-being.
1.3.1 Dental health
Caries
Research has failed to demonstrate a significant association between
malocclusion and caries, whereas diet and the use of fluoride toothpaste
are correlated with caries experience. However, clinical experience
suggests that in susceptible children with a poor diet, malalignment
may reduce the potential for natural tooth-cleansing and increase the
risk of decay.
Periodontal disease
The association between malocclusion and periodontal disease is weak,
as research has shown that individual motivation has more impact than
tooth alignment upon effective tooth brushing. Certainly, good toothbrushers
are motivated to brush around irregular teeth, whereas in the
individual who brushes infrequently their poor plaque control is clearly
ofmoreimportance.Nevertheless,itwouldseemlogicalthatinthemiddle
of this range that, irregular teeth would hinder effective brushing. In addition,
certain occlusal anomalies may prejudice periodontal support.
2 The rationale for orthodontic treatment
1.1 Definition
1.2 Prevalence of malocclusion
It is perhaps pertinent to begin this section by reminding the reader
that malocclusion is one end of the spectrum of normal variation and is
not a disease.
Ethically, no treatment should be embarked upon unless a demonstrable
benefit to the patient is feasible. In addition, the potential advantages
should be viewed in the light of possible risks and side-effects,
including failure to achieve the aims of treatment. Appraisal of these
factors is called risk–benefit analysis and, as in all branches of medicine
and dentistry, needs to be considered before treatment is commenced
for an individual patient. In parallel, financial constraints coupled with
the increasing costs of health care have led to an increased focus upon
the cost–benefit ratio of treatment. Obviously the threshold for treatment
and the amount of orthodontic intervention will differ between
a system that is primarily funded by the state and one that is private or
based on insurance schemes.
Decision to treat
depends upon
Benefits of treatment versus Risks
Improved function Worsening of dental health
(e.g. caries)
Improved aesthetics Failure to achieve aims of
treatment
1.3 Need for treatment
Orthodontics is that branch of dentistry concerned with facial growth,
with development of the dentition and occlusion, and with the diagnosis,
interception, and treatment of occlusal anomalies.
Table 1.1 UK child dental health survey 2003
In the 12-year-old age band:
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Children undergoing
orthodontic treatment
at the time of the survey 8%
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Children not undergoing
treatment – in need
of treatment (IOTN dental
health component) 26%
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
No orthodontic need
(NB includes children who
have had treatment in past) 57%
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Crowding may lead to one or more teeth being squeezed buccally or
lingually out of their investing bone, resulting in a reduction of periodontal
support. This may also occur in a Class III malocclusion where the lower
incisorsincross-bitearepushedlabially,contributingtogingivalrecession.
Traumatic overbites can also lead to increased loss of periodontal support
and therefore are another indication for orthodontic intervention.
Finally, an increased dental awareness has been noted in patients
following orthodontic treatment, and this may be of long-term benefit
to oral health.
Trauma to the anterior teeth
Any practitioner who treats children will confirm the association
between increased overjet and trauma to the upper incisors. A recent
systematic review has provided additional evidence for this association.
This paper used a meta-analysis technique to synthesize the results
from previous studies. Eleven studies were deemed to fit the reviewers’
criteria. The authors found that individuals with an overjet in excess
of 3 mm had more than double the risk of injury. The odds ratio for
traumatic injury was calculated to be 2.30 for overjets less than 3 mm.
Overjet is a greater contributory factor in girls than boys even though
traumatic injuries are more common in boys. Other studies have shown
that the risk is greater in patients with incompetent lips.
Masticatory function
Patients with anterior open bites (AOB) and those with markedly
increased or reverse overjets often complain of difficulty with eating,
particularly when incising food. Classically patients with AOB complain
that they have to avoid sandwiches containing lettuce or cucumber.
Speech
The soft tissues show remarkable adaptation to the changes that occur
during the transition between the primary and mixed dentitions, and
when the incisors have been lost owing to trauma or disease. In the
main, speech is little affected by malocclusion, and correction of an
occlusal anomaly has little effect upon abnormal speech. However, if a
patient cannot attain contact between the incisors anteriorly, this may
contribute to the production of a lisp (interdental sigmatism).
Tooth impaction
Unerupted teeth may rarely cause pathology. Unerupted impacted
teeth, for example maxillary canines, may cause resorption of the
roots of adjacent teeth. Dentigerous cyst formation can occur around
unerupted third molars or canine teeth. Supernumerary teeth may also
give rise to problems, most importantly where their presence prevents
normal eruption of an associated permanent tooth or teeth.
Temporomandibular joint dysfunction syndrome
This topic is considered in more detail in Section 1.7.
Those occlusal anomalies for which there is evidence
to suggest an adverse effect upon the longevity of
the dentition, indicating that their correction would
benefit long-term dental health
• Increased overjet
• Increased traumatic overbites
• Anterior crossbites (where causing a decrease in labial
periodontal support of affected lower incisors)
• Unerupted impacted teeth (where there is a danger
of pathology)
• Crossbites associated with mandibular displacement
1.3.2 Psychosocial well-being
While it is accepted that dentofacial anomalies and severe malocclusion
do have a negative effect on the pyschological well-being and selfesteem
of the individual, the impact of more minor occlusal problems
is more variable and is modified by social and cultural factors. Research
has shown that an unattractive dentofacial appearance does have
a negative effect on the expectations of teachers and employers.
However, in this respect, background facial appearance would appear
to have more impact than dental appearance.
A patient’s perception of the impact of dental variation upon his
or her self-image, is subject to enormous diversity and is modified by
cultural and racial influences. Therefore, some individuals are unaware
of marked malocclusions, whilst others complain bitterly about very
minor irregularities.
The dental health component of the Index of Orthodontic Treatment
Need was developed to try and quantify the impact of a particular
malocclusion upon long-term dental health. The index also comprises
an aesthetic element which is an attempt to quantify the aesthetic
handicap that a particular arrangement of the teeth poses for a patient.
Both aspects of this index are discussed in more detail in Chapter 2.
The psychosocial benefits of treatment are however countered
to a degree by the visibility of appliances during treatment and their
effect upon the self-esteem of the individual. In other words a child
who is being teased about their teeth will probably also be teased
about braces.
Demand for treatment 3
1.4 Demand for treatment
After working with the general public for a short period of time, it
can readily be appreciated that demand for treatment does not necessarily
reflect need for treatment. Some patients are very aware of mild
rotations of the upper incisors, whilst others are blithely unaware
of markedly increased overjets. It has been demonstrated that awareness
of tooth alignment and malocclusion, and willingness to undergo
orthodontic treatment, are greater in the following groups:
• females
• higher socio-economic families/groups
• in areas which have a smaller population to orthodontist ratio,
presumably because appliances become more accepted
One interesting example of the latter has been observed in countries
where provision of orthodontic treatment is mainly privately funded, for
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example, the USA, as orthodontic appliances are now perceived as a
‘status symbol’.
With the increasing dental awareness shown by the public and the
increased acceptability of appliances, the demand for treatment
is increasing rapidly, particularly among the adult population who
may not have had ready access to orthodontic treatment as children.
In addition, increased dental awareness also means that patients
are seeking a higher standard of treatment result. These combined
pressures place considerable strain upon the limited resources of
state-funded systems of care. As it appears likely that the demand
for treatment will continue to escalate, some form of rationing of
state-funded treatment is inevitable and is already operating in some
countries. In Sweden for example, the contribution made by the state
towards the cost of treatment is based upon need for treatment
as determined by the Swedish Health Board’s Index (see IOTN in
Chapter 2).
4 The rationale for orthodontic treatment
1.5 The disadvantages and potential risks of orthodontic treatment
Like any other branch of medicine or dentistry, orthodontic treatment
is not without potential risks (see Table 1.2).
1.5.1 Root resorption
It is now accepted that some root resorption is inevitable as a consequence
of tooth movement. On average, during the course of a conventional
2-year fixed-appliance treatment around 1 mm of root length
will be lost. However, this mean masks a wide range of individual variation,
as some patients appear to be more susceptible and undergo
more marked root resorption. Evidence would suggest a genetic basis in
these cases. Radiographic signs which are associated with an increased
risk include shortened roots with evidence of previous root resorption,
pipette-shaped or blunted roots, and teeth which have previously
suffered an episode of trauma. In addition, more resorption is seen in
cases where extensive movement of root apices has been undertaken.
1.5.2 Loss of periodontal support
As a result of reduced access for cleansing, an increase in gingival
inflammation is commonly seen following the placement of fixed
appliances. This normally reduces or resolves following removal of the
appliance, but some apical migration of periodontal attachment and
alveolar bony support is usual during a 2-year course of orthodontic
treatment. In most patients this is minimal, but if oral hygiene is poor,
particularly in an individual susceptible to periodontal disease, more
marked loss may occur.
Removable appliances may also be associated with gingival inflammation,
particularly of the palatal tissues, in the presence of poor oral
hygiene.
1.5.3 Decalcification
Caries or decalcification occurs when a cariogenic plaque occurs in
association with a high-sugar diet. The presence of a fixed appliance
predisposes to plaque accumulation as tooth cleaning around the components
of the appliance is more difficult. Decalcification during treatment
with fixed appliances is a real risk, with a reported prevalence of
between 2 and 96 per cent (see Chapter 18, Section 18.7). Although
there is evidence to show that the lesions regress following removal of
the appliance, patients may still be left with permanent ‘scarring’ of the
enamel Fig. 1.1.
1.5.4 Soft tissue damage
Traumatic ulceration can occur during treatment with both fixed and
removable appliances, although it is more commonly seen in association
Table 1.2 Potential risks of orthodontic treatment
Problem Avoidance/Management of risk
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Decalcification Dietary advice, improve oral hygiene, increase
availability of fluoride
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Abandon treatment
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Periodontal Improve oral hygiene. Avoid moving teeth
attachment loss out of alveolar bone
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Root resorption Avoid treatment in patients with resorbed,
blunted, or pipette-shaped roots
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Loss of vitality If history of previous trauma to incisors,
counsel patient
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Relapse Avoidance of unstable tooth positions at end of
treatment
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Retention
Fig. 1.1 Decalcification.
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The temporomandibular joint and orthodontics 5
Table 1.3 Failure to achieve treatment objectives
Operator factors Patient factors
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Errors of diagnosis Poor oral hygiene
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Errors of treatment planning Failure to wear appliances
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Anchorage loss Repeated appliance breakages
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Technique errors Failed appointments
1.6 The effectiveness of treatment
The decision to embark upon orthodontic treatment must also consider
the effectiveness of appliance therapy in correcting the malocclusion
of the individual concerned. This has several aspects.
• Are the tooth movements planned attainable? This is considered
in more detail in Chapter 7 but, in brief, tooth movement is only
feasible within the constraints of the skeletal and growth patterns
of the individual patient. The wrong treatment plan, or failure to anticipate
adverse growth changes, will reduce the chances of success.
In addition, the probable stability of the completed treatment needs
to be considered. If a stable result is not possible, do the benefits
conferred by proceeding justify prolonged retention, or the possibility
of relapse?
• There is a wealth of evidence to show that orthodontic treatment is
more likely to achieve a pleasing and successful result if fixed appliances
are used, and if the operator has had some postgraduate
training in orthodontics.
• Patient co-operation.
The likelihood that orthodontic treatment will benefit a patient is
increased if the malocclusion is severe, the patient is well-motivated
and appliance therapy is planned and carried out by an experienced
orthodontist. The likelihood of gain is reduced if the malocclusion is
mild and treatment is undertaken by an inexperienced operator.
In essence, it may be better not to embark on treatment at all, rather
than run the risk of failing to achieve a worthwhile improvement.
1.7 The temporomandibular joint and orthodontics
The aetiology and management of temporomandibular joint dysfunction
syndrome (TMD) have aroused considerable controversy in all
branches of dentistry. The debate has been particularly heated regarding
the role of orthodontics, with some authors claiming that orthodontic
treatment can cause TMD, whilst at the same time others have advocated
appliance therapy in the management of the condition.
There are a number of factors that have contributed to the confusion
surrounding TMD. The objective view is that TMD comprises a
group of related disorders of multifactorial aetiology. Psychological,
hormonal, genetic, traumatic, and occlusal factors have all been
implicated. It is accepted that parafunctional activity, for example
bruxism, can contribute to muscle pain and spasm. Success has been
claimed for a wide assortment of treatment modalities, reflecting
both the multifactorial aetiology and the self-limiting nature of the
condition. Given this it is wise to try irreversible approaches in the first
instance. The reader is directed to look at two recent Cochrane reviews
(see further reading) on the use of stabilization splints and occlusal
adjustment.
1.7.1 Orthodontic treatment as a contributory
factor in TMD
A survey of the literature reveals that those articles claiming that
orthodontic treatment (with or without extractions) can contribute to
the development of TMD are predominantly of the viewpoint (based
on the authors’ opinion) and case report type. In contrast, controlled
longitudinal studies have indicated a trend towards a lower incidence
of the symptoms of TMD among post-orthodontic patients compared
with matched groups of untreated patients.
The consensus view is that orthodontic treatment, either alone or in
combination with extractions, does not ‘cause’ TMD.
1.7.2 The role of orthodontic treatment in
the prevention and management of TMD
Some authors maintain that minor occlusal imperfections lead to
abnormal paths of closure and/or bruxism, which then result in the
development of TMD. If this were the case, then given the high incidence
of malocclusion in the population (50–75 per cent), one would
expect a higher prevalence of TMD than the reported 10 per cent. A
number of carefully controlled longitudinal studies have been carried
out in North America, and these have found no relationship between
the signs and symptoms of TMD and the presence of non-functional
occlusal contacts or mandibular displacements. However, other studies
have found a small but statistically significant association between TMD
and some types of malocclusion including Class II skeletal pattern
(especially associated with a retrusive mandible); Class III; anterior
open bite; crossbite and asymmetry. Further well-designed studies are
with the former as a removable appliance which is uncomfortable is
usually removed. Over-enthusiastic apical movement can lead to
a reduction in blood supply to the pulp and even pulpal death. Teeth
which have undergone a previous episode of trauma appear to be
particularly susceptible, probably because the pulpal tissues are
already compromised.
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required to delineate the aetiology of TMD in more detail, bearing in
mind that this term probably comprises a range of related disorders.
A review of the current literature would indicate that orthodontic
treatment does not ‘cure’ TMD. It is important to advise patients, particularly
those who present reporting TMD symptoms, of this and to
note this in their records.
Whilst current evidence indicates that orthodontic treatment is not
a contributory factor and also does not cure the TMD, it is advisable to
carry out a TMD screen for all potential orthodontic patients. At the
very least this should include questioning patients about symptoms; an
examination of the temporomandibular joint and associated muscles
and recording the range of opening and movement (see Chapter 5). If
signs or symptoms of TMD are found then it may be wise to refer the
patient for a comprehensive assessment and specialist management
before embarking on orthodontic treatment.
Key points
• The decision to undertake orthodontic treatment or not
is essentially a risk–benefit analysis where the perceived
benefits in commencing treatment at that time outweigh
the potential risks.
• If there is any uncertainty as to whether the patient will
co-operate and/or benefit from treatment, then it is
advisable not to proceed at that time.
6 The rationale for orthodontic treatment
Al-Ani, M. Z., Davies, S. J., Gray, R. J. M., Sloan, P., and Glenny, A. M.
(2005). Stablisation splint therapy for temporomandibular pain
dysfunction syndrome. Cochrane Database of Systemic Reviews,
2004, Issue 1.
American Journal of Orthodontics and Dentofacial Orthopedics, 101(1),
(1992).
This is a special issue dedicated to the results of several studies set up
by the American Association of Orthodontists to investigate the link
between orthodontic treatment and the temporomandibular joint.
It is essential reading for all those involved in dentistry.
Chestnutt, I. G., Burden, D. J., Steele, J. G., Pitts, N. B., Nuttall, N. M., and
Morris, A. J. (2006). The orthodontic condition of children in the United
Kingdom, 2003. British Dental Journal, 200, 609–12.
Davies, S. J., Gray, R. M. J., Sandler, P. J., and O’Brien, K. D. (2001).
Orthodontics and occlusion. British Dental Journal, 191, 539–49.
This concise article is part of a series of articles on occlusion.
It contains an example of an articulatory examination.
Egermark, I., Magnusson, T., and Carlsson, G. E. (2003). A 20-year followup
of signs and symptoms of temporomandibular disorders in subjects
with and without orthodontic treatment in childhood. Angle
Orthodontist, 73, 109–15.
A long-term cohort study which found no statistically-significant
difference in TMD signs and symptoms between subjects with or
without previous experience of orthodontic treatment.
Holmes, A. (1992). The subjective need and demand for orthodontic
treatment. British Journal of Orthodontics, 19, 287–97.
Koh, H. and Robinson, P. G. (2004) Occlusal adjustment for treating
and preventing temporomandibular joint disorders. The Cochrane
Database of Systemic Reviews, 2003, Issue 1.
Luther, F. (1998). Orthodontics and the TMJ: Where are we now? Angle
Orthodontist, 68, 295–318.
An authoritative review of the literature on this subject.
Murray, A. M. (1989). Discontinuation of orthodontic treatment:
a study of the contributing factors. British Journal of Orthodontics,
16, 1–7.
Nguyen, Q. V., Bezemer, P. D., Habets, L., and Prahl-Andersen, B. (1999).
A systematic review of the relationship between overjet size and
traumatic dental injuries. European Journal of Orthodontics, 21,
503–15.
Office for National Statistics (2004). Children’s dental health in the United
Kingdom 2003. Office for National Statistics, London.
Shaw, W. C., O’Brien, K. D., Richmond, S., and Brook, P. (1991). Quality
control in orthodontics: risk/benefit considerations. British Dental
Journal, 170, 33–7.
A rather pessimistic view of orthodontics.
Turbill, E. A., Richmond, S., and Wright, J. L. (1999). A closer look at GDS
orthodontics in England and Wales 1: Factors influencing effectiveness.
British Dental Journal, 187, 211–16.
Wheeler, T. T., McGorray, S. P., Yurkiewicz, L., Keeling, S. D., and
King, G. J. (1994). Orthodontic treatment demand and need in third
and fourth grade schoolchildren. American Journal of Orthodontics
and Dentofacial Orthopedics, 106, 22–33.
Contains a good discussion on the need and demand for
treatment.
References for this chapter can also be found at www.oxfordtextbooks.co.uk/
orc/mitchell3e. Where possible, these are presented as active links which
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Principal sources and further reading
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