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34 © 1998 Blackwell Science Ltd
Journal of Oral Rehabilitation 1998 25; 34–39
Restorative treatment need assessment by dentally andnondentally trained subjectsD . J . L A M B , B . E L L I S * & R . PAT E L Department of Restorative Dentistry and *Department of EngineeringMaterials, University of Sheffield, Sheffield, U.K.
SUMMARY A study was carried out which compared
how two groups of people, one with clinical dental
experience and one without, assessed restorative
dental treatment need. Using a visual analogue scale,
a group of final year dental students (n J 50) and
nonclinical university students (n J 50) assessed the
extent to which they considered common dental
imperfections, viz. spacing of the upper anterior
teeth and discolouration of upper anterior teeth,
Introduction
A person’s dental state begins to affect their quality of
life adversely when tooth loss is sufficient to interfere
with either function or good appearance (Reisine et al.,
1989). Recently, much effort has been directed to
establishing practical guidelines for determining the
amount or type of treatment patients need. Researchers
have shown that functional guidelines can determine
the decision whether or not to replace a missing
posterior tooth (Kayser, 1981). Similarly, guidelines
have been introduced to aid the decision making process
when deciding to restore suspected carious teeth,
variation only being introduced by the clinician’s
interpretation of the objective standards (e.g.
radiographs) which record the degree of pathology
(Elderton, 1993).
Poor appearance of the anterior teeth is usually a
compelling reason for patients to seek restorative dental
treatment (Rosenoer & Sheiham, 1995), but in this area
of practice where need is determined by the sense of
aesthetics, guidelines are difficult to establish and the
warranted restorative correction. The group of
dental students judged the necessity for treatment
of discolouration to be more urgent than correction
of spacing. The nondental group did not differentiate
between the degrees of need. Data were non-normal
in distribution but the use of appropriate statistical
tests showed the differences in mean assessments to
be significant.
amount of treatment sought, prescribed, or necessary
is influenced by variations in the perceptions of patients,
their social peers, and the clinical professionals involved.
Any mismatch between the aesthetic judgements of
these three groups might then lead to demand or
provision of unnecessary treatment. Identification and
correction of such mismatches can only take place when
a measure for defects of appearance is developed.
In the field of orthodontics, measures have been
developed based on comparative panel ratings of an
illustrated range of defects, as in the Index of
Orthodontic Treatment Need (Evans & Shaw, 1987) or
by assessment on a verbally defined range of categories
(Tedesco et al., 1983). Without modification, neither
can be applied to restorative dentistry; the former
because it deals with defects not generally amenable to
restorative correction, and the latter because the small
numbers of broadly defined categories do not allow
minor differences to be identified. An alternative is the
visual analogue scale (VAS). This has been used in the
past mainly for the measurement of feelings such as
anxiety (Hornblow & Kidson, 1976) but has proved
T R E AT M E N T A S S E S S M E N T B Y T R A I N E D A N D U N T R A I N E D S U B J E C T S 35
Fig. 1. Visual analogue scale used in study (not to scale).
useful in dentistry to measure pain (Seymour, Charlton
& Phillips, 1983) and recently its advantages for
measurement of denture security have been emphasized
(Lamb & Ellis, 1996). It is simple to apply in the clinical
environment and is easily understood.
The present study was designed to test whether using
a VAS allowed differences to be detected in the extent
to which two groups responsible for influencing the
demand for restorative treatment perceived the
seriousness of imperfections in the appearance of the
anterior teeth. Two imperfections were chosen;
variation in colour and spacing. To ensure consistency
of examination conditions and avoid the inconvenience
to patients which would be involved by repeated
assessments, the imperfections were presented in a
standardized form by means of colour prints. Two groups
of subjects were studied and the differences between
them analysed. One group consisted of senior dental
students, whose judgements of appearance have been
shown to be similar to those of professional specialist
groups (Kerr & O’Donnell, 1990) and the other of
nonclinical undergraduate university students.
Materials and methods
Subjects
Two groups of subjects were studied. One consisted of
50 senior dental students at Sheffield School of Clinical
Dentistry (dental group, D). It comprised 29 male and
21 female students, all in the age range 21–31 years,
except two who were aged 36 and 39 years. The
other group comprised 50 nonclinical undergraduate
university students (nondental, N), 32 male, 18 female,
age range 18–24 years, in a range of years at Sheffield
University.
Visual analogue scale and standards
The visual analogue scale used was a 10 cm horizontal
line between two end-phrases, that on the left being
‘restorative treatment needed urgently’ and on the
right ‘restorative treatment unnecessary’ (Fig. 1). After
explaining the use of the scale, each subject studied
two colour prints, A and B (Figs 2 a & 2b). Print A
© 1998 Blackwell Science Ltd, Journal of Oral Rehabilitation 25; 34–39
Fig. 2. (a) Example of discoloured maxillary anterior teeth used
in study. (b) Example of spaced maxillary anterior teeth used
in study.
showed an intact dentition with two discoloured
anterior teeth, namely the upper right central incisor
which had been root filled and showed a brownish
discolouration and an upper left lateral incisor on which
an ill-matched crown had been placed. Print B showed
an intact dentition with spacing between the upper
anterior teeth. By making a vertical mark across the
horizontal line of the VAS the subjects in each group
then assessed the degree to which they felt that
restorative correction of appearance was required.
To prevent any bias which might arise from presenting
the prints in an arrangement corresponding to the
horizontal VAS, the prints were presented to the subjects
mounted vertically. The degree of impairment of
appearance was judged by measuring the distance of
the mark from the left-hand extremity of the VAS, thus
the lower the VAS score the greater the assessed need
for correction.
36 D . J . L A M B et al.
Fig. 3. Box and whisker plots of the data sets. Set 1, dental
student assessment of ‘discolouration’ picture (VAS DA); Set 2,
dental student assessment of ‘spacing’ picture (VAS DB); Set 3,
nondental student assessment of ‘discolouration’ picture (VAS
NA); Set 4, nondental student assessment of ‘spacing’ picture
(VAS NB).
Statistical analysis
Distributions of the data were studied and comparisons
between groups made by Minitab for Windows (Minitab
Inc., PA, U.S.A.) using appropriate statistical tests.
Results
The four data sets are represented in Fig. 3 as box and
whisker plots. Figure 4 is a histogram of the data from
the nondental evaluation of picture A (VAS NA), and
Fig. 5 is a probability plot of the same data. Figure 6 is
a histogram of the data from the dental evaluation of
picture A (VAS DA), and Fig. 7 a plot of VAS DB against
VAS DA. Descriptive statistics of the data are summarized
in Table 1 and the data sets are compared statistically
in Table 2.
Discussion
In the past, investigators have shown that when senior
dental students judge the adverse appearance of
orthodontic abnormalities, their judgements are
equivalent to those of a specialist professional group,
with both being more critical than the general public
(Kerr & O’Donnell, 1990). The assessments made by
each group, dental and nondental (VAS D and VAS N)
of each picture (A and B), are given in a box and
whisker plot (Fig. 3) showing that the judgements of
the dental students (VAS DA and VAS DB) lie at the
more extreme ends of the scale. The descriptive statistics
© 1998 Blackwell Science Ltd, Journal of Oral Rehabilitation 25; 34–39
Fig. 4. Histogram of nondental student group assessment of
‘discolouration’ picture (VAS NA).
Fig. 5. Probability plot of nondental assessment of ‘discolouration’
picture (VAS NA). Probability 5 i/(n 1 1), where i 5 rank of
observation, n 5 number of observations.
for all data sets (Table 1) confirm that whereas
discolouration is rated as requiring treatment more
urgently by the dental group than the nondental group
T R E AT M E N T A S S E S S M E N T B Y T R A I N E D A N D U N T R A I N E D S U B J E C T S 37
Fig. 6. Histogram of data from dental student group assessment
of ‘discolouration’ picture (VAS DA).
Fig. 7. Pairwise plot of dental student assessment of spacing
picture (VAS DB) against dental student assessment of
‘discolouration’ picture (VAS DA).
(mean VAS DA 5 25 mm, mean VAS NA 5 49 mm),
spacing is assessed as requiring treatment less urgently
by the dental group than the nondental group (mean
VAS DB 5 71 mm, mean VAS NB 5 51 mm).
© 1998 Blackwell Science Ltd, Journal of Oral Rehabilitation 25; 34–39
Table 1. Descriptive statistics and tests of skewness* of data sets.
VAS DA, dental student assessment of discolouration picture;
VAS DB, dental student assessment of spacing picture; VAS NA,
nondental student assessment of discolouration picture; VAS NB,
nondental assessment of spacing picture, Cp2, Pearson’s second
criterion of skewness 5 3 (mean – median)/s.d.
VAS DA VAS DB VAS NA VAS NB
n 50 50 50 50
Range 2–67 1–99 6–99 3–99
Mean 25·26 71·04 48·90 51·20
Median 22·0 73·5 48·5 51·0
S.d. 17·10 21·92 25·04 27·04
Cp2 1 0·57 –0·33 1 0·048 1 0·022
*Taken from Caswell (1982) and Rees (1995a).
Table 2. Statistical comparison of data sets by Mann–Whitney
test. VAS DA, dental student assessment of discolouration picture;
VAS DB, dental student assessment of spacing picture; VAS NA,
nondental student assessment of discolouration picture; VAS NB,
nondental assessment of spacing picture. H0, no difference between
sets; H0, rejected for P , 0·05; H0, not rejected for P . 0·05.
VAS DA VAS DB VAS NA VAS NB
VAS DA – P , 0·0001 P , 0·0001 P , 0·0001
VAS DB P , 0·0001 – P , 0·0001 P 5 0·0002
VAS NA P , 0·0001 P , 0·0001 – P . 0·05
VAS NB P , 0·0001 P 5 0·0002 P . 0·05 –
Whether the differences are significant depends on
the appropriate statistical analysis of the scores. In the
past, when studying pain response, some investigators
have suggested a normal distribution for VAS scores
(Lui & Aitkenhead, 1991) while others have insisted
that the distribution is non-normal and nonparametric
statistical tests should be employed (Skevington, 1986).
A study on appearance carried out in 1974 showed that
by means of a test resembling the VAS it was possible
to discriminate between degrees of ‘attractiveness’ of
the features. Nonparametric statistical tests were used
but no explanation or analysis of the data was provided
in the text (Giddon, Hershon & Lennartsson, 1974).
More recent work, although using a more conventional
visual analogue scale, also made statistical deductions
without analysis of the data distribution (Howells &
Shaw, 1985).
None of the sets of scores were distributed normally.
Histograms showed the scores of the nondental groups
(Fig. 4 is a histogram of the data VAS NA, that of
38 D . J . L A M B et al.
VAS NB was similar), to form approximately uniform
(rectangular) distributions (Rees, 1995b), a finding
which was confirmed by probability plot (Fig. 5).
Histograms showed the dental data sets to be skewed,
DA to the left (Fig. 6.) and DB to the right. Tests of
skewness confirm this finding (Table 1). Since the
data was non-normal, subsequent comparison of the
differences between the sets was made by
nonparametric tests (Table 2) and showed that while
no significant differences could be detected between
the assessments made by the nondental group of either
the ‘discolouration’ or ‘spacing’ defects, the assessments
of the dental group were significantly different, both
from one another and from the nondental assessments.
Comparison of the pairs of results from the dental group
(Fig. 7.) showed that despite the scatter there was
consistency in judgement and only two members of the
group considered spacing to require treatment more
urgently than discolouration.
It is possible to hypothesize that the difference
between the two groups of assessors lay in their training,
and that dental students, being more aware of the
extent of the normal range of dental imperfections
might be prepared to judge tooth spacing, which is
a common natural occurrence, less critically than a
nondental group. Tooth discolouration, on the other
hand, is often associated with nonvitality and apical
pathology. Influenced by the possible consequences for
the patient, a dental group might allow themselves to
judge the need for treatment to be more urgent.
Clinical implications
Our results show that when judging the need to correct
imperfections of appearance of the anterior teeth,
assessments of dental students and nondental students
do not coincide. Dental students advise correction of
tooth discolouration more readily than nondental
students, and treatment for spacing less readily. The
implication of this is that patients who have discoloured
or spaced teeth and base their judgement on treatment
need on the opinion of their dentist may have opinions
very different from those whose opinions are formed
by their friends and relatives. To give a practical example,
it means that a patient embarrassed by a degree of tooth
spacing which aroused critical comment among his
friends and relatives might have difficulty in persuading
a clinician to accept his degree of concern and correct
the defect, if that clinician thought the defect within
© 1998 Blackwell Science Ltd, Journal of Oral Rehabilitation 25; 34–39
normal limits and its correction might expose him to a
criticism of overprescription.
It has been shown that dental students and dentists
have similar attitudes when assessing treatment need
(Kerr & O’Donnell, 1990). Nevertheless, despite basing
our findings on dental students, we do not imply that
all dentists will tend to overprescribe or underprescribe
for treatment of this nature. Clinical professionals and
members of the public who form the opinion of others
might not necessarily make the same assessment of
discoloured or spaced teeth in other people if they
themselves suffered from the imperfection in question;
this could only be confirmed by study of a client
group consisting of clinical and nonclinical subjects with
discoloured and spaced teeth. Nevertheless, it is valid
to suspect that patients with discoloured teeth or spaced
teeth might often have very different assessments of
their need for treatment if they allow their judgements
to be formed on the sole basis of the opinions of either
their dentist or their friends and relatives.
Conclusions
(i) The visual analogue scale can be successfully
applied to the assessment of defects in dental
appearance.
(ii) The data is non-normal in distribution and
appropriate nonparametric statistical tests must be
used to establish significant differences.
(iii) Groups of dental and nondental students perceive
the need for treatment of imperfections of
appearance of the anterior teeth to differing extents
and clinicians must be aware of the problems this
could pose in practice.
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Correspondence: David J. Lamb, Department of RestorativeDentistry, School of Clinical Dentistry, Claremont Crescent,Sheffield S10 2TA, U.K.