restorative treatment need assessment by dentally and nondentally trained subjects

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


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


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).


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


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.

restorative treatment need assessment by dentally and nondentally trained subjects

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