Introduction

It was recognized over three decades ago thatany meaningful evaluation of the need for ortho-dontic treatment must include an assessment ofthe aesthetic impairment of a malocclusion(Federation Dentaire Internationale, 1970).Others have also concluded that reliablemeasures of dental aesthetics are essential if the social and psychological implications ofmalocclusion are to be assessed (Howells andShaw, 1985). Further indirect support for the useof measures of aesthetic impairment have comefrom longitudinal studies of the relationshipbetween malocclusion and dental disease (Addyet al., 1988; Helm and Peterson, 1989; Shaw et al.,1991). These investigations confirmed that, in themain, the ill-effects of malocclusion werepsychosocial in nature and related to theaesthetic impairment, rather than any functionaldisadvantage. It is therefore not surprising that

when the Index of Orthodontic Treatment Need(IOTN; Brook and Shaw, 1989) was developed itcontained a standardized measure of dentalaesthetic impairment, the Aesthetic Component(AC), which is applied entirely independently ofthe rating of functional disability or occlusaldiscrepancy (Dental Health Component). TheAC consists of a series of 10 colour photographsarranged on a continuum of attractiveness, withgrade 1 being the most attractive and grade 10the least attractive (Figure 1).

During the initial development of IOTN, the subjective opinion of 74 dentists (44 ortho-dontists and 30 non-orthodontists) was used tovalidate the cut-off points representing thedifferent levels of orthodontic treatment need.The results of that validation exercise found thataccording to professional opinion grades 14 of the AC represent no need for orthodontictreatment, grades 57 represent borderline need,and grades 810, definite need for treatment

European Journal of Orthodontics 24 (2002) 5359 2002 European Orthodontic Society

The Aesthetic Component of the Index of Orthodontic

Treatment Need validated against lay opinion

Orlagh Hunt*, Peter Hepper**, Chris Johnston*, Mike Stevenson*** andDonald Burden**Division of Orthodontics, **School of Psychology and ***Department of Epidemiology and Public Health, Queens University Belfast, UK

SUMMARY This study aimed to determine the threshold of aesthetic impairment whereorthodontic treatment would be sought by a sample of lay people. Using the 10-gradeAesthetic Component (AC) scale of the Index of Orthodontic Treatment Need (IOTN), 215 university students selected the level of aesthetic impairment that represented thepoint at which they would seek orthodontic treatment.

Only nine (4.3 per cent) of the respondents recorded a threshold grade beyond grade 5in the AC. The AC photograph grade 4 was found to be the most commonly selectedthreshold photograph. Subjects who visited the dentist every 6 months were more likely tochoose a threshold photograph closer to the attractive end of the scale than those whovisited their dentist less frequently (P < 0.01).

This study, using lay people rather than dental health professionals, suggests that ascurrently used the AC does not reflect societys aesthetic expectations. The results indicatethat when using the AC of the IOTN the no need for treatment category should be grades13 of the AC, rather than grades 14.

(Richmond et al., 1995). This approach of usingthe subjective opinion of clinicians to verifytreatment need thresholds is not unique and wasused by earlier workers to validate other occlusalindices (Salzmann, 1968; Summers, 1971; Jennyet al., 1983). Since its introduction by Brook and Shaw (1989) the IOTN has been widelyembraced by orthodontists throughout the world(Shaw et al., 1995). However, from a scientific

perspective, it could be argued that the use ofprofessional opinion to validate an orthodonticaesthetic ranking scale is inherently flawed.Numerous studies have confirmed that, by virtue of their training and experience, dentalprofessionals are conditioned to take an overlycritical view of any deviation from normalocclusion (Shaw et al., 1975; Prahl-Andersen,1978). Many dentists favour an interventional

54 O. HUNT ET AL.

Figure 1 The Aesthetic Component (AC) of the IOTN (Brook and Shaw, 1989).

approach even where this is not sought by thepatient or parent, and may not necessarily be ofsignificant benefit (Shaw et al., 1975; Prahl-Andersen, 1978; Downer, 1987).

There is, therefore, evidence to support theview that the AC of the IOTN should be valid-ated against the opinion of people who are notdental professionals. The only previous studythat has attempted to do this (Stenvik et al.,1997) was compromised by virtue of the fact thatthe subjects included children who had alreadybeen selected for orthodontic treatment.

The present study aimed to determine thethreshold at which a sample of lay people wouldseek orthodontic intervention and to comparethis with the threshold level currently suggestedby the AC of the IOTN.

Methods

Two hundred and fifteen social science studentswho were in their first or second year atuniversity were asked to complete a question-naire to determine the point at which they wouldwish to receive orthodontic treatment. Thesubjects comprised 53 males (24.7 per cent) and162 females (75.3 per cent) with a median age19 years (range of 1743 years). The questionnaireswere completed during two separate lectures,one consisting of 75 students, the other consistingof 140 students.

A 35-mm colour slide of the AC of the IOTNwas projected onto a 15 10-m screen in a lecturetheatre containing approximately 100 students at any one time. The purpose and use of the AC were explained in a few paragraphs at thebeginning of the questionnaire. Participants were instructed to record the AC grade thatindicated the point at which they would seektreatment if the photographs represented theirown dentition. In addition, the students alsorated the attractiveness of their own teeth (veryunattractive, unattractive, attractive, or veryattractive) and the importance that they attrib-uted to having straight teeth (very unimportant,unimportant, important, or very important).

Each student was asked about their personalexperience of orthodontic treatment in terms ofwhether they had ever been referred for

orthodontic treatment, if they felt they shouldhave been referred, whether they had everreceived orthodontic treatment, or if they hadever refused orthodontic treatment. In addition,the subjects were asked how frequently theyattended the dentist (every 6 months, once ayear, every 2 years, less often than every 2 years,only when in pain, never), and if anyone in theirimmediate family had ever received orthodontictreatment. Subjects were asked not to conferwhen completing the questionnaires.

Data analysis was performed using theStatistical Package for the Social Sciences (SPSS,Version 9, SPSS Inc., Chicago, Illinois).Descriptive statistics were used to describe thesubjects histories in relation to their orthodonticexperiences and their dental attendance rates.The relationship between the choice of thresholdphotograph and the participant variables wasanalysed using forward stepwise linear regres-sion with the AC rating as the dependentvariable. Independent variables entered into theanalysis included age, gender, whether or notparticipants had been referred for orthodontictreatment, if they felt they should have beenreferred, if they had ever received orthodontictreatment, and if they had ever refusedorthodontic treatment. The frequency of dentalattendance and whether anyone in theirimmediate family had ever received orthodontictreatment were also entered into the analysis.

Linear regression analysis was also used toexamine the relationship between each subjectsopinion of the attractiveness of their own teeth,the importance of having straight teeth, and theirchoice of threshold photograph in the AC. A c 2

test was used for tests of association involvingcategorical data.

Results

Previous experience of orthodontic treatment

The questionnaires returned by four subjectswere incomplete for this section and weretherefore not included. Ninety-two (43.6 percent) of the remaining sample reported that theyhad received orthodontic treatment and 119(56.4 per cent) reported that they had not.

AESTHETIC COMPONENT OF IOTN 55

Among those who did not receive orthodontictreatment, 28 (23.5 per cent) had been offeredtreatment, but declined and a further 30 subjects(25.2 per cent) felt they should have beenreferred for treatment. One hundred and twentysubjects (56.8 per cent) reported that a familymember had received orthodontic treatment.

Frequency of dental attendance

One hundred and twenty subjects (55.8 per cent)reported that they attended the dentist every 6 months, while a further 49 (22.8 per cent)subjects reported that they visited their dentistonce a year. Therefore, the majority ofparticipants (78.6 per cent) attended the dentistat least once a year.

Threshold where orthodontic treatment would be sought

The AC grade 4 was found to be the mostcommonly selected threshold photograph (Table 1). Ninety-two (42.8 per cent) of thesample selected this grade as the point in thescale of severity at which they would seekorthodontic treatment if the photographs hadrepresented their own dentition. Figure 2 showsthe threshold grade selected by the wholesample. By grade 4, 74 per cent of the samplereported that they would seek orthodontictreatment and by grade 5, 95.8 per cent of thesample would seek orthodontic treatment. Only

nine (4.3 per cent) of the respondents recorded athreshold grade beyond grade 5 of the AC(Figure 2).

Linear regression analysis was used to explorethe relationship between the threshold levelselected and each subjects orthodontic experi-ence and dental attendance. The only variablethat was found to influence the cut-off pointchosen on the AC scale was the frequency ofdental attendance. Those who visited theirdentist more regularly chose a cut-off gradecloser to the more attractive end of the scalecompared with those who attended their dentistless frequently (P < 0.05).

The relationship between frequency of dentalattendance and the selected threshold grade ofthe AC is illustrated in Table 2. Analysis usingthe c 2 test revealed a significant associationbetween those participants who visit the dentistevery 6 months and selection of grade 3 or lesson the AC ( c 2 = 9.88, P < 0.01, df = 1).

Subjects rating of the attractiveness of own teethand their opinion on the importance of havingstraight teeth

The responses to this section of the question-naire are reported in Table 3. The majority of thesubjects (67.9 per cent) considered that their owndentitions were attractive or very attractive.In addition, the majority of respondents

56 O. HUNT ET AL.

Table 1 The Aesthetic Component (AC) gradewhere orthodontic treatment would be requested (n = 215).

AC grade No. of Percentage Cumulative subjects of subjects percentage

1 2 0.9 0.92 28 13.0 14.03 37 17.2 31.24 92 42.8 74.05 47 21.9 95.86 1 0.5 96.37 2 0.9 97.28 1 0.5 97.79 1 0.5 98.1

10 4 1.9 100.0

Figure 2 The Aesthetic Component (AC) grade whereorthodontic treatment would be requested.

(86.5 per cent) also felt it was important orvery important to have straight teeth (Table 3).

Linear regression analysis was conducted todetermine whether the participants opinion ofthe attractiveness of their own dentition andtheir perceptions of the importance of havingstraight teeth influenced their choice of cut-offpoint for treatment using the AC of the IOTN.No significant relationship was found betweenparticipants ratings of the attractiveness of theirown teeth and their choice of thresholdphotograph on the AC (P = 0.88). Although notquite achieving statistical significance, the

analysis revealed a trend for those participantswho considered having straight teeth asimportant to choose an AC photograph closer tothe attractive end of the scale (P = 0.07).

Discussion

This study used the consensus opinion of a largesample of university students to determine theacceptable limit of dental aesthetic impairment.The sample chosen represented a wide range oflay opinion, including those who had hadorthodontic treatment and those who had not.Although no evidence exists to suggest that theaesthetic preferences of university studentsdiffer from other young adults, this possibilitymust be considered when interpreting the resultsof this study.

Previous investigations have found thatfemales tend to express greater concern abouttheir facial appearance than males (Tung andKiyak, 1998). Whilst the current sample includedmore females than males, linear regressionanalysis did not detect any gender influence on the threshold chosen for the initiation oforthodontic treatment.

At the time when this cohort were adolescents,orthodontic treatment was widely available andeven if they did not receive orthodontic carethemselves, many of their peers did so. A recentsurvey in Northern Ireland revealed that, among15- and 16-year-olds, 28 per cent had receivedorthodontic treatment (Breistein and Burden,1998). In the current study, 43 per cent of thesubjects reported that they had receivedorthodontic treatment. Even allowing for thosewho had orthodontic treatment after 16 years ofage the sample contained a higher than averagelevel of subjects who had received orthodontictreatment. However, this meant that the samplewas almost equally divided between individualswith and without personal experience oforthodontic treatment. The results of this studytherefore provide a contemporary view ofsocietys perception of acceptable dentalaesthetics among individuals with an up-to-dateawareness of the potential benefits of ortho-dontic treatment. A majority of the subjects (87 per cent) reported that having straight teeth

AESTHETIC COMPONENT OF IOTN 57

Table 2 The relationship between the frequency of dental attendance and choice of AestheticComponent (AC) grade.

AC grade Attends every Attends less often than6 months every 6 months

n (cumulative n (cumulativepercentage) percentage)

1 1 (0.8) 1 (1.1) 2 22 (19.2) 6 (7.4)3 25 (40.0) 12 (20.0)4 41 (74.2) 51 (73.7)5 26 (95.8) 21 (95.8)6+ 5 (100) 4 (100)

Table 3 Subjects perception of the attractivenessof their own teeth and the importance of havingstraight teeth (n = 215).

No. of Percentage participants of sample

How attractive do you think your teeth are?Very unattractive 5 2.3Unattractive 61 28.4Attractive 134 62.3Very attractive 12 5.6Missing data 3 1.4

How important is it to have straight teeth?Very unimportant 6 2.8Unimportant 20 9.3Important 141 65.6Very important 45 20.9Missing data 3 1.4

was important or very important. The age groupof the sample (mean = 20.3 years) was alsoconsidered to be sufficiently mature to be able tomake a balanced judgement on the relativeinfluence of dental aesthetics on social accept-ability, self-esteem, and self-confidence. Anearlier similar study found that children weresignificantly less critical in their aestheticjudgements than young adults (Stenvik et al.,1997).

It could be argued that dental professionalsare best placed to make judgements on theaesthetic values held by potential patients andtheir families. However, there is evidence thatdental professionals assessment of aestheticacceptability differs from the layperson (Prahl-Andersen, 1978; Shaw et al., 1980). This meansthat the thresholds adopted in the AC of theIOTN for determining who is and who is not in need of orthodontic treatment may representthe biased view of a small group of dentalprofessionals, rather than the wider view ofsociety.

In this investigation the subjects were asked to decide at what point they would seekorthodontic treatment using the continuum ofdental aesthetic impairment represented by theAC. The results indicate that the level ofaesthetic impairment represented by grades 6through to 10 were considered to require ortho-dontic treatment by 100 per cent of the subjectssurveyed. The young adults therefore agree withthe professionals assessment that individualswith this level of aesthetic impairment are inneed of orthodontic treatment.

In this type of study, it is always difficult todefine the point on a scale of dentalattractiveness where orthodontic interventionshould be contemplated. However, the resultsindicate that by the time grade 4 was reached amajority of the participants (74 per cent) hadindicated that they would seek orthodontictreatment. A large proportion of the subjects (42 per cent) felt that orthodontic treatment was needed to correct the level of aestheticimpairment represented by grade 4 on the IOTNAC. This result conflicts with the professionallydefined threshold currently used by the AC ofIOTN (Richmond et al., 1995). In normal use, all

the grades up to and including grade 4 of the ACare considered to represent little or no need fororthodontic treatment (Richmond et al., 1995),yet the majority of this sample of young adultsreported that they would seek orthodontic careat a lower level of aesthetic impairment. There isstrong evidence from this study to suggest thatthe threshold point for the initiation oforthodontic treatment should be lowered tograde 3 of the AC, and the little or no needcategory should only include grades 13.

Only one previous investigation has comparedthe professionally defined cut-off values of theAC with the opinion of lay people. In thatNorwegian study, 137 children, 126 of theirparents, and 98 young adults were asked torecord if any of the 10 dentitions in the ACrequired orthodontic correction (Stenvik et al.,1997). The authors found that in the three groupsstudied the threshold selected for orthodonticintervention was grade 5 of the AC. Theytherefore concluded that Norwegian lay peoplewere in agreement with the professionallydefined no need for treatment grouping (grades14 of the AC). It is difficult to explain thedifferent findings between this previous studyand the present investigation. However, in theNorwegian study the way in which the AC wasused was apparently not explained to thesubjects and they were not asked specifically toselect a threshold image on the continuum.

Nearly one-third (31 per cent) of thosequestioned in the current study felt that theywould seek orthodontic treatment for the levelof aesthetic impairment represented by grades23 of the AC. This confirms the highexpectations of dental aesthetic perfectionamong lay people. However, it seems reasonableto define the threshold for the initiation oforthodontic treatment at the point where themajority of lay people would seek treatment, i.e. grade 4. Orthodontic treatment need indices,such as the IOTN, provide the opportunity toreduce subjective bias in determining who is inneed of orthodontic treatment and who is not.However, to be scientifically valid occlusalindices must correctly identify those in need.This investigation using lay people rather thandentists suggests that, as currently used, the AC

58 O. HUNT ET AL.

does not reflect societys aesthetic expectations.To truly reflect lay opinion, a minor adjustmentis required to the AC to lower the thresholdpoint for the initiation of treatment by one gradefrom grade 4 to grade 3.

Using multivariate analysis, the only factorfound to influence the choice of threshold for the initiation of orthodontic treatment was thefrequency with which the subjects visited theirdentist. Those who attended their dentist morefrequently (every 6 months) tended to have alower threshold for the initiation of orthodontictreatment than those who attended lessfrequently. This most likely reflects the greateremphasis placed on dental health and dentalappearance by regular dental attenders.

Conclusions

1. Aesthetic ranking scales used in orthodontictreatment need indices should be validatedusing lay people who have a good awarenessof orthodontic treatment.

2. The results of this study indicate that thethreshold for the initiation of orthodontictreatment defined by the AC of the IOTNshould be lowered so that grade 4 is includedin the treatment need category.

3. This study also found that regular dentalattenders had higher expectations of dentalaesthetics than those who visited their dentistless frequently.

Address for correspondence

Ms Orlagh HuntDivision of Orthodontics, School of DentistryQueens University of BelfastRoyal Victoria HospitalGrosvenor RoadBelfast BT12 6BPUK

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