Download The development of an index of orthodontic treatment priority

tjaoftai JcmmmlcfOnJudaula 11 (1989) 309-320
C 19*9 European Orthodontic Society
The development of an index of orthodontic treatment
priority
* University College Hospital, London
** University Dental Hospital of Manchester, England
SUMMARY The aim of this study was to develop a valid and reproducible index of orthodontic
treatment priority.
After reviewing the available literature, it was felt that this could be best achieved by using two
separate components to record firstly the dental health and functional indications for treatment,
and secondly the aesthetic impairment caused by the malocclusion.
A modification of the index used by the Swedish Dental Health Board was used to record the
need for orthodontic treatment on dental health and functional grounds. This index was modified
by defining five grades, with precise dividing lines between each grade.
An illustrated 10-point scale was used to assess independently the aesthetic treatment need of
the patients. This scale was constructed using dental photographs of 12-year-olds collected
during a large multi-disciplinary survey. Six non-dental judges rated these photographs on a
visual analogue scale, and at equal intervals along the judged range, representative photographs
were chosen.
To test the index in use, two sample populations were defined; a group of patients referred for
treatment, and a random sample of 11 -12-year-old schoolchildren. Both samples were examined
using the index and satisfactory levels of intra- and inter-examiner agreement were obtained.
Introduction
Whilst many indices exist to record malocclusion, it is important to distinguish those that
classify malocclusions into types (Angle, 1899)
and those that record prevalence in epidemiological studies (Bjork et al., 1964), from those
indices that attempt to record treatment need or
priority. Furthermore, indices used to record
treatment success and treatment difficulty will
have differing requirements.
Many indices have been developed with the
intention of categorizing malocclusions into various groups, according to the urgency and need
for treatment (Summers, 1971; Salzmann, 1968;
Linder-Aronson, 1974; Lundstrdm, 1977; Grainger, 1967; Draker, 1960). Individuals with
greatest treatment need can then be assigned
priority when orthodontic resources are limited,
and when the availability of treatment is
unevenly spread. Similarly, individuals with little
need for treatment can be safeguarded from the
potential risks of treatment (Shaw, 1988).
Recent research has called into question many
of the previously held views on the benefits of
orthodontic treatment (Shaw et al., 1980). There
may be small effects on the susceptibility to
temporomandibular dysfunction (Roth, 1973;
Mohlin and Thilander, 1984) and periodontal
disease (Horupe/ al., 1987;Sandali, 1973;Davies
etal, 1988; Addy etal, 1988). However, so many
studies have been undertaken on these subjects,
with differing conclusions, and often only weak
statistical associations, that it is difficult to
believe that the effect, with a small number of
specific exceptions, can be anything but minor.
There will be a reduced incidence of trauma to
incisors where treatment reduces their prominence. However, treatment needs to be carried
out early (before the child is 10-years-old) if the
peak incidence of trauma is to be avoided
(Jarvinen, 1979). The avoidance of tooth impaction is also desirable.
The main benefit to the patient of orthodontic
treatment may be in improved aesthetics and
social-psychological well-being, and additionally
the effect this may have on attitudes to dental
health. This has important implications in the
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Peter H. Brook* and William C. S h a w "
310
construction of any treatment priority index.
Such an index must involve an aesthetic assessment, and allow appropriate weighting for this
component.
Subjects and materials
Development of the dental health component
With these criteria in mind, the index of treatment priority used by the Swedish Dental Board
(Linder-Aronson, 1974) was used as the basis for
grading the functional and dental health indications for treatment. There arefivegrades, grade 1
representing little or no need for treatment and
grade 5 representing great need of treatment
(Table 1). An attempt was made to try to
establish from the literature meaningful values
for cut-off points between grades for each occlusal trait that represents a quantifiable threat to
the dentition.
Most of the traits are recorded using a millimetre rule, modified to incorporate a device for
angular measurements. Crowding was recorded
by measuring the largest displacement between
teeth in the arches, using a modified version of
the index described by Lau et al. (1984).
In use, only the highest scoring trait need be
recorded, as this determines the grading of the
patient.
The aesthetic component
The second part of the overall assessment of
treatment priority, was to record the aesthetic
impairment contributed by the malocclusion.
For this component the SCAN Index (Standardized Continuum of Aesthetic Need) was utilized
(Evans and Shaw, 1987).
This scale was constructed using dental photographs of 1000 12-year-olds collected during a
large multi-disciplinary survey. Six non-dental
judges rated these photographs on a visual
analogue scale, and at equal intervals along the
judged range, representative photographs were
chosen giving a 10-point scale from 0.5 (attractive dental appearance) to 5.0 (unattractive dental appearance) (Fig. 1).
Testing the index
Two-hundred and twenty-two patients referred
to a regional orthodontic centre for advice or
treatment were examined under ideal lighting
conditions with radiographs available. Both
components of the index were applied and the
patients were also asked to give their own rating
on the aesthetic scale.
Intra-examiner error was estimated by the same
examiner seeing 67 of these patients on two
occasions, at least one week apart, without
reference to notes. A second examiner assessed
72 of the patients independently of the first
examiner to estimate inter-examiner error. To
simulate the use of the indices in a screening
programme, 333, 11-12-year-old school children
were examined. A cross section of schools
attended by children from a broad range of social
backgrounds were visited, and all available children in thefirstyear of secondary education were
examined. Each child was examined in the school
medical room using an angle-poise lamp for
lighting, a simple millimeter rule and a dental
mirror. Again, both components of the index
were applied, and the self rating recorded on the
SCAN scale. In addition a dental surgery assistant recorded her rating on the SCAN scale.
Forty-six children were chosen at random for reexamination.
Amongst the school sample 58 (17.4 per cent)
of the children were undergoing, or had completed orthodontic treatment. The orthodontist
involved in the treatment of each of these
children was contacted so that details of the
original malocclusion and information from the
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The following criteria were considered to be
important in the development of a new index of
orthodontic treatment need.
1. Separate components to record:
(a) Functional and dental health indications
for treatment.
(b) Aesthetic impairment.
2. For the functional and dental health component, each occlusal trait thought to contribute
to the longevity and satisfactory functioning
of the dentition, needs to be defined, and
easily measurable cut-off points between each
grading need to be established.
In view of the uncertainty of the relative contribution that each occlusal trait makes to the
longevity and satisfactory functioning of the
dentition and indeed the doubt surrounding the
importance of aesthetics in the provision of
orthodontic care, the indices needed to be sufficiently flexible to allow for adjustment of cut-off
points and relativities between the categories, as
the results from adequate longitudinal research
become available.
PETER H. BROOK AND WILLIAM C. SHAW
311
ORTHODONTIC TREATMENT PRIORITY
Table 1 Index of orthodontic treatment need dental health component: for use on patients.
Grade 4—Great
Increased overjet greater than 6 mm but less than or equal to 9 mm.
Reverse overjet greater than 3.5 mm with no reported masticatory or speech difficulties.
Reverse overjet greater than 1 mm but less than or equal to 3.5 mm with reported masticatory or speech difficulties.
Anterior or posterior CTOssbites with greater than 2 mm displacement between retruded contact position and intercuspal
position.
Posterior lingual crossbites with no occlusal contact in one or both buccal segments.
Servere displacement of teeth greater than 4 mm.
Extreme lateral or anterior open bite greater than 4 mm.
Increased and complete overbite causing notable indentations on the palate or labial gingivae.
Patient referred by colleague for collaborative care e.g. periodontal, restorative or TMJ considerations.
Less extensive hypodontia requiring pre-restorative orthodontics or orthodontic space closure to obviate the need for a
prosthesis (not more than 1 tooth missing in any quadrant).
Grade 3—Moderate
Increased overjet greater than 3.5 mm but less than or equal to 6 mm with incompetent lips at rest.
Reverse overjet greater than 1 mm but less than or equal to 3.5 mm.
Increased and complete overbite with gingival contact but without indentations or signs of trauma.
Anterior or posterior crossbite with less than or equal to 2 mm but greater than 1 mm displacement between retruded contact
position and intercuspal position.
Moderate lateral or anterior open bite greater than 2 mm but less than or equal to 4 mm.
Moderate displacement of teeth greater than 2 mm but less than or equal to 4 mm.
Grade 2—Little
Increased overjet greater than 3.5 mm but less than or equal to 6 mm with lips competent at rest.
Reverse overjet greater than 0 mm but less than or equal to 1 mm.
Increased overbite greater than 3.5 mm with no gingival contact.
Anterior or posterior crossbite with less than or equal to 1 mm displacement between retruded contact position and intercuspal
position.
Small lateral or anterior open bites greater than 1 mm but less than or equal to 2 mm.
Pre-normal or post-normal occlusions with no other anomalies.
Mild displacement of teeth greater than 1 mm but less than or equal to 2 mm.
Grade 1—None
Other variations in occlusion including displacement less than or equal to 1 mm.
study models could be used in place of the
recordings taken at the school visits. In practice,
as many of the children were only just commencing treatment, the gradings were little changed.
Results
Reproducibility of the index
Dental health component
Intra-examiner agreement ranged from a Kappa
value of 0.837 for the referred population seen
under ideal conditions, to 0.754 for the nonreferred population. In total there were 14 errors
out of 118 re-tests and in all cases the disagreement was only by one grade. Guidelines for the
interpretation of the Kappa statistic (Landis and
Koch, 1977) are shown in Table 2.
Inter-examiner agreement ranged from 0.7310.797. In total there were 21 out of 154 measurements that were not agreed. There were only 2
cases where the error was by more than one
grade.
SCAN component
For the referred sample there were three raters;
the patient and the two examiners. This gave two
patient ratings (PI and P2), two ratings by
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Grade 5—Very great
Defects of deft lip and/or palate.
Increased overjet greater than 9 mm.
Reverse overjet greater than 3.5 mm with reported masticatory or speech difficulties.
Impeded eruption of teeth (with the exception of third molars) due to crowding, displacement, the presence of supernumerary
teeth, retained deciduous teeth and any other pathological cause.
Extensive hypodontia with restorative implications (more than one tooth missing in any quadrant) requiring pre-restorative
orthodontics.
81:4
PETER H. BROOK AND WILLIAM C. SHAW
05
1-5
45
25
Figure 1 The SCAN Scale. Originally presented in colour in a horizontal arrangement. 0.5 extreme left. 5 extreme right.
Table 2
Guidelines for the interpretation of Kappa.
Kappa statistic
Strength of agreement
<0.00
0.00-0.20
0.21-0.40
0.41-0.60
0.61-0.80
0.81-1.00
Poor
Slight
Fair
Moderate
Substantial
Almost perfect
Table 3 Examiner variability. Pearson's correlation
coefficients for SCAN.
Referred Population
PB1
PB2
PI
examiner 1 (PB1 and PB2), and one rating by
examiner 2 (WCS). The examiner reproducibility, and the comparability of patient and examiner ratings, were investigated using Pearson's
correlation coefficient. The results are listed in
Table 3 with the number of repeat examinations
in parenthesis.
Whilst the correlations between the orthodon-
P2
PB2
PI
P2
WCS
0.87
(72)
0.50
(82)
0.45
(72)
0.36
(72)
0.40
(72)
0.67
(72)
0.71
(82)
0.73
(72)
0.37
(82)
0.29
(72)
tists were quite high, they were poorer than those
obtained by Evans and Shaw (1987), where selfretaining lip retractors were used during the
orthodontists' and the patients' assessments. For
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35
313
ORTHODONTIC TREATMENT PRIORITY
General features of the referred and non-referred
populations
The numbers of patients falling into each Dental
Health Index grade for each group are illustrated
Table 4 Examiner variability. Pearson's correlation
coefficients for SCAN.
School Population
DSA1
DSA2
SI
S2
PB1
PB2
0.78
(46)
0.66
(46)
0.61
(46)
0.70
(46)
0.69
(46)
0.78
(46)
0.80
(46)
0.85
(46)
0.64
(46)
0.68
(46)
0.81
(46)
0.88
(46)
0.61
(46)
0.69
(46)
0.95
(46)
DSA2
SI
S2
PB1
Table 5 Distribution of Dental Health grades.
Dental
health
grade
Referred population
School population
Numbers
Numbers
Grade 1
Grade2
Grade 3
Grade 4
Grade 5
1
11
40
112
39
0.5
5.4
19.7
55.2
19.2
24
93
107
92
17
7.2
27.9
32.1
27.6
5.1
Total
203
100.0
333
100.0
Percentage
Percentage
in Table 5, and Figs. 2 and 3. The SCAN Index
scores are illustrated in Table 6, and Figs. 4 and
5.
Discussion
Reproducibility
Dental health component
In general, the reproducibility of this index was
very good. The same grade was re-chosen 86.4
per cent of the time with different examiners, and
in 93 per cent of cases for the same examiner
under the more ideal clinic setting (the referred
population).
The common traits causing disagreement, in
descending order of frequency were; crowding,
increased overjet, crossbites and overbites.
Crowding represents a problem in recording
when the patient is in the mixed dentition.
Further refinement of the index in terms of the
mixed dentition analysis of crowding, may lead
to an improvement in reproducibility.
Evidently, the less than ideal conditions of the
school examination resulted in poorer reproducibility. Should reproducibility levels similar to
that of the referred population be required, then
better lighting, better patient seating facilities
and a more relaxed work rate would be required.
SCAN component
Whilst the correlation coefficients for the SCAN
ratings were reasonably high for the school
survey, they were less satisfactory for the referred
population. It was felt that this may have been
due to the omission of the self-retaining lip
retractors for this sample.
During the original development of the index,
both front and side views of the dentition were
available. This enabled conditions such as large
overjets to be more readily assessed. During the
surveys, it was noted that the areas around 1.5
and 4.0 on several raters graphs, showed slight
inconsistencies. An inspection of the index
demonstrates the difficulties that may be leading
to these effects. Both the representations of 2.0
and 4.5 show increased overjets, that a lay person
in the absence of a side view, may not find too
displeasing.
So, in summary, incorporation of side views
may assist in identifying large overjets. Some
guidelines for assessing the relative attractiveness
of features not depicted on the scale, may also be
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this reason, self-retaining cheek retractors were
used routinely for the examination of the nonreferred sample.
In the school survey, 46 subjects were rated
twice by the orthodontist (PB) on the SCAN
scale. Additionally, there was a rating by the
dental surgery assistant on two occasions (DSA1
and DSA2), and two subject ratings (SI and S2).
Again, these relationships were examined using
Pearson's correlation coefficient (Table 4).
On this occasion intra-examiner agreement for
the orthodontist (PB) was better. The DSA's
reproducibility was less good. There was however, superior inter-examiner agreement on this
occasion. There was also better correlation
between the subjects' and the professionals'
ratings.
314
PETER H. BROOK AND WILLIAM C. SHAW
REFERRED POPULATION DHI
2
3
4
5
DENTAL HEALTH INDEX SCORE
Figure 2 Distribution of ratings for the Dental Health Index obtained from examination of 222 patients referred to a regional
orthodontic centre.
desirable. Self-retaining cheek retractors are a
useful aid to recording dental aesthetics.
The referred sample
As expected, the referred sample showed a large
proportion of patients scoring in the higher
grades of the Dental Health Index, with all but 6
per cent in the highest three grades. The orthodontists' SCAN ratings showed a similar shift to
the unattractive side. The patient ratings showed
this effect to a much smaller extent.
The school population
There was a much more even spread of patients
amongst the grades of the Dental Health Index
for this population, with approximately one
third of the subjects in grade 3, and one third
either side of this. The professional ratings using
the SCAN Index, showded a distribution skewed
towards the attractive end of the scale. The
patient ratings are skewed even further towards
the attractive end of the scale, i.e. there was a
tendency for subjects to overrate their dental
attractiveness.
Comparison of the two samples
From an overview of the data recorded from the
samples, it appears quite obvious that there are
significant differences between them. Indeed the
median test and the /-test demonstrate this
readily for the Dental Health component and the
SCAN component respectively (p< 0.0001).
However, the findings from the two surveys
are not directly comparable. Firstly, the referred
sample had a wide age spread, and secondly,
when applying the Dental Health component to
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1
315
ORTHODONTIC TREATMENT PRIORITY
SCHOOL POPULATION DHI
2
3
4
5
DENTAL HEALTH INDEX SCORE
Figure 3
Distribution of ratings for the Dental Health Index obtained from examination of 333 unselected schoolchildren.
the referred population, the examiners had
access to radiographs. For the school sample, it
was necessary to set criteria for such parameters
as unerupted or missing teeth, i.e. except for
incisors and first molars, all teeth were assumed
to be present, at age 11-12 years, premolars and
canines were assumed to be unerupted but not
impacted, missing upper lateral incisors and
lower incisors were assumed to be developmentally absent whereas missing upper central incisors and first molars were assumed to have been
extracted.
In an attempt to overcome this, a sub-group of
25 from the referred sample, with a similar age
range to the school sample was selected. Any
conditions that would have required radiographs
to confirm the diagnosis, were regraded using the
Table 6
score).
SCAN
rating
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Total
Distribution of SCAN ratings (Orthodontist
Referred Population
School 1Population
Numbers
Numbers
0
2
19
17
28
33
39
48
8
8
202
Percentage
0.0
1.0
Percentage
8.4
13.8
16.3
19.2
23.6
3.9
3.9
16
54
65
59
62
33
26
12
5
1
4.8
16.2
19.5
17.7
18.6
9.9
7.8
3.6
1.5
0.3
100.0
333
100.0
9.4
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1
316
PETER H. BROOK AND WILLIAM C. SHAW
REFERRED POPULATION SCAN
5
6
7
8
SCAN RATING
Figure 4 Distribution ot raungs for the SCAN index obtained from examination of 222 patients referred to a regional
orthodontic centre.
criteria set for the population seen without
radiographs.
It was still evident that the samples were drawn
from different populations (Mest p< 0.001 for
the SCAN ratings; median test p< 0.001 for the
Dental Health ratings). These tests seemingly
validate the index, at least in terms of the
priorities of patients or dentists in bringing about
referral to an orthodontist.
acceptable as it has been shown that most of the
traits can be recorded with a high degree of
precision (Helm et al., 1975; Helm, 1977) with up
to 80 per cent agreement. However in their pure
form they do not record treatment priority.
The allocation of weighting factors to traits
can give an overall figure that is intended to
represent a score of severity, and thus treatment
priority. Several indices of this type have been
developed (Summers, 1971; Draker, 1960; GraComparison with previous methods of recording inger, 1967). Correlation coefficients for exatreatment priority
miner agreement for such indices have ranged
Angle's classification (Angle, 1899) has been
from a Spearman correlation coefficient of 0.903
shown to have poor reproducibility (Gravely and
(Summers, 1971) to as low as 0.34 (Albino et al.,
Johnson, 1974) and has no usefulness in record1978) in a community screening setting. The
ing treatment priority. For epidemiological use,
validity of such indices relies on acceptance of the
the registration techniques described by Bjork et
authors' weightings.
al. (1964) and Baume et al. (1973) may be quite
Indices based upon the classification of mor-
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4
317
ORTHODONTIC TREATMENT PRIORITY
SCHOOL POPULATION SCAN
30
P
E 20 R
C
E 15 N
T
A
G 10E
19.5
17.7
18.6
9.9
7.8
5 -
3.6
1.5
1
2
3
4
5
6
7
8
0.3
10
SCAN RATING
Figure 5
Distribution of ratings for the SCAN index obtained from examination of 333 unselected schoolchildren.
phological traits rely on the subjective opinion of
an experienced judge to define the dividing lines
between each trait (Linder-Aronson, 1974;
Lundstrom, 1977; Malmgren, 1980). Used as
such, the percentage concordance ranges from
55.9 to 74.6 per cent (Malmgren, 1980).
Subjective clinical opinion alone has agreement of about 80 per cent in most studies
(Bowden and Davies, 1975; Helm et ai, 1975)
but the validity of such judgements depends
upon the examiners' knowledge of the harmful
effects of malocclusion. In addition, inexperienced examiners will find it difficult to apply
such techniques.
The orthodontic index of treatment need"
described in this report has examiner agreement
levels that compare well with any of those
previously described (80.5-93 per cent). As its
development was based upon a full analysis of
the available literature (Brook, 1987) and the
experience gained from a longitudinal survey
(Shaw et ai, 1986), it is not felt that its validity
can be inferior to that of other indices. The
inclusion of a separate index to record aesthetic
impairment removes the most subjective element
from indices of this kind. Good levels of agreement for this component have been demonstrated (Pearson's correlation coefficient values
from 0.71-0.95).
Some support for the validity of the index
comes from the observation that fewer subjects
in the lower grades were referred for orthodontic
advice. The extent to which it represents common professional opinion is presently being
evaluated. However, true validity (i.e. that the
index measures what it purports to measure)
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25-
318
PETER H. BROOK AND WILLIAM C. SHAW
Table 7 Interrelationship between the SCAN and Dental Health Index scores.
(Cumulative Percentages)
SCAN Score
0.5
1.0
1
2
3
4
5
2.1
4.2
4.5
4.8
4.8
Total
4.8
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
Total
5.4
15.6
19.5
20.4
21.0
6.3
25.8
37.2
39.6
40.5
6.6
31.8
51.3
57.3
58.5
7.2
34.8
60.9
75.3
76.8
7.2
35.1
64.5
84.9
86.7
7.2
35.1
65.7
91.5
94.5
7.2
35.1
67.2
93.9
98.2
7.2
35.1
67.2
94.8
99.7
7.2
35.1
67.2
94.8
100.0
7.2
35.1
67.2
94.8
100.0
21.0
40.5
58.5
76.8
86.7
94.5
98.2
99.7
100.0
100.0
must await the compilation of a greater body of
knowledge than that which is currently available.
It may accurately reflect contemporary professional opinion, but this may be erroneous.
Epidemiological uses for the index
During testing of the index on the school sample,
it was felt that it represented a simple, quick and
reasonably reproducible method of recording
orthodontic treatment need. As all the traits are
simple to record, it may be possible for less highly
trained personnel to apply the index, following
suitable training and calibration.
tions could produce a similar percentage. An
alternative method would be to combine the
scores from the two components to give an
overall score, then define limits based on this
figure.
Eventual definitions of cut-offs must reflect the
setting in which treatment would be provided
and include a consideration of the success rate of
the treatment which would be available, the
iatrogenic risks, and the cost (Shaw, 1987).
Conclusions
An index with two components has been developed to record orthodontic treatment priority.
The first of these components records need for
As developed so far, the index records the dental
treatment on dental health and functional
health need for treatment, and the aesthetic
grounds. The second component records the
impairment, and by implication the socialaesthetic impairment, and by implication, the
pschological need for treatment. As yet, no
justification for treatment on social-psychologiattempt has been made to combine these into an
cal grounds.
overall assessment of treatment need, or to define
scores below which treatment should be withThe indices were tested on a sample of patients
held.
referred for orthodontic treatment and advice,
To assist discussion in this area, a table
and on a random selection of 11-12-year-old
showing the cumulative percentages of patients
school children. It was easy and quick to use and
having varying combinations of the Dental
had acceptable reproducibility. True validation
Health grades, and the SCAN ratings has been
of such an index must await the emergence of
constructed from the non-referred sample (Table
further research data on the effects of malocclu7).
sion, but the present index can be adaptable to
new information. Work is currently in progress
Many authors quote figures of around 50 per
to gauge the extent to which the index reflects
cent for the percentage of children who would
common professional opinion.
benefit from orthodontic treatment (Gardiner,
1956; Haynes, 1982; Foster and Walpole Day,
Defining specific ranges within which patients
1973). From Table 7, it can be seen that this
should, or should not be offered treatment has
number would be obtained if patients scoring 'not been attempted but a mathematical model
grade 3 or less on the Dental Health Index and
has been suggested that can define combinations
2.0 or less on the SCAN scale were excluded (51.3 of the gradings that will encompass varying
per cent), leaving 48.7 per cent. Other combinaproportions of a target population.
Further development of the index
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DHI
Grade
ORTHODONTIC TREATMENT PRIORITY
Acknowledgements
Address for correspondence
Professor W C Shaw
Department of Orthodontics
University Dental Hospital of Manchester
and Turner Dental School
Higher Cambridge Street
Manchester M15 6FH
England
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The authors would like to thank Mr G. O. Taylor
and his staff for providing access and assistance
for the school visits, Mrs H. Worthington and
Mrs C. Mitropoulos for advice with the study
design and statistics, Mr J. Sinclair for computational assistance and Mrs C. Corkill for acting as
a scribe. The study was supported in part by a
grant from the DHSS and BLG.
319
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PETER H. BROOK AND WILLIAM C. SHAW