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Epidemiology and Public Health Aspects of Malocclusion Sven Helm J DENT RES 1977 56: C27 DOI: 10.1177/002203457705600313011 The online version of this article can be found at: http://jdr.sagepub.com/content/56/3_suppl/C27

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Epidemiology and Public Health Aspects of Malocclusion SVEN HELM

Institute of Orthodontics, Royal Dental College, 160, Jagtvej, DK-2100 Copenhagen, Denmark

The aim of epidemiologic studies of malocclusion is to describe and analyze the prevalence and distribution of malocclusion in various populations, the ultimate goal being to identify etiologic factors. A further aim is to contribute to the solution of the public health problems concerning assessment of need for orthodontic treatment and organization of orthodontic services. Similar aims apply to epidemiologic studies of dental diseases, for example, caries. But in orthodontics the connection between the two aims is less clear-cut than it is with caries, as, in general, no direct conclusion can be drawn from the occurrence of malocclusion to the need for orthodontic treatment. Abundant epidemiologic data relating to malocclusion have been compiled over this century. But the epidemiology of malocclusion has been lingering at the descriptive stage. This is due mainly to methodologic shortcomings or, rather, short-cuts sustained by tradition and indeed orthodoxy. At an early point it was realized that, due to the complexity of malocclusion, epidemiologic studies had to be based on some kind of classification. Angle's' classification is the only one among several typologic classifications which has gained wide ground in the epidemiology of malocclusion, although probably without the consent of Edward Angle. At the turn of the century, he attempted to systematize the planning of orthodontic treatment among his patients according to their anteroposterior jaw relation. He classified the positional relationship by the sagittal occlusion of the first permanent molars, supplemented by the sagittal relation of the incisors. This classification proved useful for its particular purpose and, subsequently, Angle' examined the distribution according to the different classes of 1,000 children who, incidentally, were receiving orthodontic treatment in his office. Ever since, Angle's classification has been Vol. 56 1977

misused in epidemiologic studies all over the world. Occasionally, it has been emphasized that Angle's classification is not sufficiently differentiated for epidemiologic purposes, and it has also been pointed out that the individual morphologic traits of Angle's classes are not all adequately defined.2 3 As might be expected, therefore, poor intraand interexaminer reliability of recording Angle's classes has been demonstrated.4 Nevertheless, only lately it has been realized that, since the number of combinations of single traits of malocclusion is practically infinite, an exhaustive classification of malocclusion for epidemiologic purposes cannot be made into a limited number of types.2 The logical approach was, consequently, to base such classification on the single traits of malocclusion. A given malocclusion trait represents a certain variation of the morphologic variable concerned. By way of example, congenital absence is a variation in the number of teeth, and deep bite is a variation of vertical overbite. One presupposition for an objective method of registration is the formulation of registration criteria which, for each individual variable, establish a discrimination between normal variation (that is nonoccurrence of a malocclusion trait) and deviation (that is occurrence of a malocclusion trait). For some variables the formulation of criteria is simple, as any variation of these may be interpreted as a malocclusion trait. This applies to the discrete variables, as for instance the number of teeth, where any

congenital variation constitutes

a

deviation.

Conversely, there is no obvious demarcation between normal variation and deviation for the majority of the variables, namely the continuous ones, such as overjet, overbite, molar-occlusion, and space conditions. Therefore it might be claimed that until acceptable criteria of normal variation are developed for these variables, the correC27 MALOCCLUSION

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sponding deviations will remain ill-defined. This, however, would seem to be a semantic rather than a practical epidemiologic problem, since the reverse approach can be made. For each continuous variable, a cut-off point can be chosen as criterion of deviation. Every measure beyond that cut-off point is then taken as a deviation, but without implying that every measure before the cut-off point necessarily represents normality. For example, for deviation of maxillary overjet a certain measure-say minimum 6 mm-may be chosen, for distal molarocclusion a cuspto-cusp distal relationship of first molars, and so forth. Although such criteria are necessarily to some extent arbitrary, they may provide a meaningful basis for registration methods, which can be applied to comparative epidemiologic studies in different populations and to investigations of interrelationships between the various traits. The first comprehensive method for epidemiologic registration of the single morphologic traits of malocclusion was developed by Bjork, Krebs and Solow.5 It has been shown that the majority of the traits can be recorded at a high level of consistency by an experienced examiner,6 and the method has proved useful in studies of nearly 10,000 children from various ethnic groups. Teni years later, the method formed the basis of the FDI Method for Measuring Occlusal Traits7 and, in a simplified version, it is part of the Danish national recording system for the child dental health services.8 While the necessary tools for analytical epidemiologic studies of malocclusion are now available, it would be a mistake to believe that, consequently, the problems of assessing the need for orthodontic treatment are nearly solved. On the contrary, it must be emphasized again that the registration methods mentioned can be used for rmeasuring severity of malocclusion only in terms of degree of deviation, but certainly not directly in terms of impairment, handicap, or treatment priority. In other words, the methods do not provide a treatment priority index. The current major public health problem in this field is to bridge the gap between recognition of the occurrence of the defined single traits or combinations of traits, and determination of the need for treatment of these conditions.

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Various indices of malocclusion have been claimed to provide an objective method both for assessing severity of malocclusion and for estimating priorities of orthodontic treatment. Closer inspection of the properties of these indices would therefore seem to be justified. It is common to all malocclusion indices that the presence of some selected morphologic traits is expressed numerically by means of a scoring system. The simplest procedure consists of assigning a value of one point to each tooth which is not in perfect alignment, without regard to the degree of displacement.9 More often, however, an arbitrary weighting of the scores is performed with regard to the location in the dental arches of a given deviation,'0 or to the degree of the deviation,"' 12 or to a combination of these factors.13-"5 Weighting procedures have also been based on multiple regression methods.16 17 Malocclusion indices have been employed in epidemiologic surveys for comparing malocclusion severity in different populations,18 19 or for studying relationships between malocclusion severity and periodontal disease.20-22 However, valuable information concerning the prevalence and influence of the various morphologic traits is lost, because entirely different traits, or combinations of traits, may produce identical index values. The main purpose of the indices is to interpret malocclusion severity objectively in terms of treatment priority. However, the objectivity involved in such interpretations would seem to be questionable. Irrespective of the weighting procedure employed, it is a common characteristic of all the indices that, fundamentally, the index scores are based on clinical estimations of the severity of the various traits. In other words, the scores are assigned according to clinical concepts of the adverse effects of the traits on facial appearance, function, and oral health. At present, however, sparse evidence is available on the sociopsychologic or physiologic effects of malocclusion in any population. The clinical estimates are therefore largely subjective and, obviously, the indices cannot be more objective than the clinical estimates on which the index scores have been based. In fact, the scoring procedure would be expected to increase, rather than to reduce the

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Vol. 56 1977

uncertainty, since different traits or combinations of traits, yielding similar index values, might well induce different clinical severity estimates. Consequently, it would seem premature to devise indices of malocclusion before associations between various occlusal traits and sociopsychologic and physiologic factors have been established.23 Future epidemiologic research should concentrate on these aspects. However, the problems of assessing need for treatment are urgent, and decisions cannot be postponed. For the time being, the orthodontist's subjective estimate of treatment need, based on professional experience, would seem to be the most realistic, if not the most satisfactory, approach to the problem of assigning treatment priorities. Only, it should be understood that even the best estimate is an intelligent guess rather than a bridge over the aforementioned gap in knowledge. In spite of the incomplete evidence of the adverse effects of malocclusion, surprisingly close interexaminer agreement has been obtained in estimates of need for orthodontic treatment in given samples of children.24'25 When two orthodontists were selecting or rejecting children for treatment, levels of reliability around 85% of the cases have been achieved. These levels of reliability compare favorably with those in recording morphologic traits of malocclusion6 and, also, in recording caries.26 Although the concept of reliability is quite distinct from that of validity,27 such professional estimates would seem to merit attention in public health planning of orthodontic services. During recent years, estimates have become available for the Scandinavian countries and for the United States. In Sweden, random samples of 7-to-16year-old children were investigated in Stockholm and in two counties.28 Excluding children whose need for treatment was judged to be only slight, the estimates of treatment need ranged between 19 and 35%70. In Norway, 31% of the child population of a particular year actually receive orthodontic treatment.29 In Denmark, all children attending the senior school classes in a small town were investigated independently by 6 orthodontists.24 Roughly, one third of the children were unanimously considered by all 6 exam-

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iners to need orthodontic treatment, one third were assigned to the no-treatment category, while one third gave rise to disagreement between examiners. Recently, the United States Public Health Service30 published a study of occlusal relationships in a sample of children 6 to 11 years old, who were selected carefully to represent the 24 million American children of those ages. In this study, 37% of the children were judged to need orthodontic treatment.31 The extent of the most urgent needs has also been assessed. Both in the Swedish and the American study,28' 30, 31 14% of a child population were estimated to present very severe handicap with treatment mandatory, or severe handicap with treatment highly desirable. Moreover, it has been found that about 180%O of Danish children with adolescent dentition show an extreme degree of one or more traits of malocclusion.32 With the present state of knowledge, it would seem justified to conclude that, according to professional estimates, approximately one third of school children would benefit from an orthodontic health service and, furthermore, that orthodontic treatment is urgently needed by at least 14 to 18% of the children. Obviously, it would be a mistake to believe that an increase in the amount of orthodontic treatment from, say, 15 to 30% of a child population would double the demand for resources. The first 15% would include the most severe orthodontic conditions requiring the most comprehensive corrective treatment. The latter 15%, conversely, would to some extent comprise less complicated types of corrective treatment, and, moreover, an appreciable number of cases of interceptive treatment, preventing the development of some of the more severe conditions. The amount of specialist manpower needed is unknown, but in most countries it is thought that a considerable deficit in orthodontic manpower exists. The greatest number of orthodontists in relation to population size in any country is probably found in Norway with, on the average, one clinical orthodontist per approximately 5,000 schoolchildren in the age range 7 to

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16 years.29 In Denmark and in the United States,33 this ratio is about 1:6,500. However, orthodontic manpower is not merely a question of quantity but also of distribution. Like other professional people, orthodontists tend to accumulate in the metropolitan areas and in the larger cities. In Denmark, for example, almost two thirds of the orthodontists work around Copenhagen where the aforementioned ratio is about 1:3,000, while in the remaining part of the country it is approximately 1:13,000. This skew situation

is

improving, however, as an

increasing number of communities are acquiring orthodontists in their child dental services.

Once the basic needs for caries control in a child population have been met, the problems of organizing orthodontic care comes into focus. Traditionally, the responsibility for initiating orthodontic measures and the economic burden of the treatment have rested mainly with the patients, or rather with their parents. Thus, the provision of orthodontic treatment has often been determined by the incidental educational and socio-economic level of the family, instead of the severity of the patient's malocclusion. Since this course of proceedings deviated from the philosophy that essential health services should be available to all who need them, independently of ability to pay, the Danish Act on Child Dental Health included orthodontics.34 In pursuance of this Act, free access to dental care is offered to all schoolchildren, including orthodontic treatment in case of recognized need.35 Lately, authors in the United States36 and Switzerland37 have expressed resentment against social orthodontics. Following public funding of orthodontic services, they visualize a spectacular rise in the demand for treatment of insignificant malocclusions. Government direction and supervision as to diagnosis and limitations of treatment, failure of the patients to meet requirements of co-operation and oral hygiene, and wasted money if corrected teeth must later be replaced by dentures, are among other grievous consequences.

None of these consequences, however, have really been experienced as a problem in the Scandinavian countries, where public child dental services in actual function are

evaluated continually. On the conthe systematic orthodontic examinabased on professional criteria, in the dental services are regarded by the profession to constitute a decisive advance toward a just selection of the patients. Moreover, it is realized that this organization permits optimum planning and timing of treatment taking into consideration the development of the individual child. It is to be hoped that increasing understanding will replace prejudice in many highly developed nations which, in the sense of social welfare, are still developing countries, and that at least all children should be given equal opportunity for receiving compete dental health care. being trary, tions, child

References 1. ANGLE, E.H.: Malocclusion of the teeth, 7th ed. Philadelphia: S.S. White Dental Manufact. Co., 1907. 2. HELM, S.: Prevalence of Malocclusion in Relation to Development of the Dentition, Acta Odont Scand 28:Suppl. 58, 1970. 3. TUNCAY, O., and BIGGERSTAFF, R.H.: Orthodontic Classification: Mystique or Reality?, Am J Orthodont 70:173-178, 1976.

4. GRAVELY, J.F., and JOHNSON, D.B.: Angle's

Classification of Malocclusion: An Assessment of Reliability, Brit J Orthodont 1:79-86, 1974. 5. BJORK, A., KREBS, A.A.; and SOLOw, B.: A Method for Epidemiological Registration of Malocclusion, Acta Odont Scand 22: 27-41, 1964. 6. HELM, S.: Intraexaminer Reliability of Epidemiologic Registrations of Malocclusion, Acta Odont Scand 35:161-165, 1977. 7. BAUME, L.J.; HOROWITZ, H.S.; SUMMERS, C.J.; BACKER DIRKS, 0.; BROWN, W.; CARLOS, J.P.; COHEN, L.K.; FREER, T.J.; HARVOLD, E.P.; MOORREES, C.; SALZMANN, J.A.; SCHMUDT, G., SOLOW, B.; and TAATZ, H.: A Method for Measuring Occlusal Traits, Int Dent J 23: 530-537, 1973. 8. HELM, S.: Recording System for the Danish Child Dental Health Services, Community Dent Oral Epidemiol 1:3-8, 1973. 9. MASSLER, M., and FRANKEL, J.M.: Prevalence of Malocclusion in Children Aged 14 to 18 Years, Am J Orthodont 37:751-768, 1951. 10. SALZMANN, J.A.: Treatment Priority Index of Malocclusion, Int Dent J 20:618-632, 1970. 11. POULTON, D.R., and AARONSON, S.A.: The Relationship Between Occlusion and Periodontal Status, Am J Orthodont 47:690-699, 1961. 12. VAN KIRK, L.E., and PENNELL, E.H.: Assess-

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Vol. 56 1977 ment of Malocclusion in Population Groups, Am J Orthodont 45:752-758, 1959. 13. DRAKER, H.L.: Handicapping Labio-lingual Deviations: A Proposed Index for Public Health Purposes, Am J Orthodont 46:295-

305, 1960. 14. HEIDEBORN, M.: Der "Entstellende-Anomalie"Index, ein Masstab zur qualitativen Erfassung von Dysgnathien auf der Grundlage der durch sie hervogerufenen Enstellung, Fortschr Kieferorthop 30:361-374, 1969. 15. HOWITT, J.W.; STRICKER, G.: and HENDERSON, R.: Eastman Esthetic Index, N Y State Dent J 33:215-220, 1967. 16. GRAINGER, R.M.: Orthodontic Treatment Priority Index, Vital and Health Statistics, National Center for Health Statistics, Series 2, Number 25, U.S. Dept. of Health, Education and Welfare, Washington, D.C., 1967. 17. SUMMERS, C.J.: The Occlusal Index: A System for Identifying and Scoring Occlusal Disorders, Am J Orthodont 59:552-567, 1971. 18. ALTEMUS, L.A.: Frequency of the Incidence of Malocclusion in American Negro Children Aged Twelve to Sixteen, Angle Orthodont 29: 189-200, 1959. 19. SZWEJDA, L.F.: The HLD Index by Race and Ingestion of Fluoridated Water, J Pub Health Dent 25:2-6, 1965. 20. BILIMORIA, K.F.: Malocclusion-Its Role in the Causation of Periodontal Disease, J AllIndia Dent Assoc 35:293-300, 314, 1963. 21. BEAGRIE, G.S., and JAMES, G.A.: The Association of Posterior Tooth Irregularity and Periodontal Disease, Brit Dent J 113:239-

243, 1962. 22. MASSLER, M., and SAVARA, B.S.: Relation of Gingivitis to Dental Caries and Malocclusion in Children 14 to 17 Years of Age, J Periodontol 22:87-96, 1951. 23. FREER, T.J.: Assessment of Occlusal Status. The Matched-Pair Similarity Technic, Int Dent J 22:412-422, 1972. 24. HELM, S.; KREIBORG, S.; BARLEBO, J.; CASPERSEN, I.; ERIKSEN, J.H.; HANSEN, W.; HANUSARDOT[1IR, B.; MUNCK, C.; PERREGAARD, J.; PRYDSO, U.; REUMERT, C.; and SPEDTSBERG, H.:

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Estimates of Orthodontic Treatment Need in Danish Schoolchildren, Community Dent Oral Epidemiol 3:136-142, 1975. 25. BOWDEN, D.E.J., and DAVIES, A.P.: Inter- and Intraexaminer Variability in Assessment of Orthodontic Treatment Need, Community Dent Oral Epidemiol 3:198-200, 1975. 26. HAUGEJORDEN, O., and SLACK, G.L.: A Study of Intra-examiner Error Associated with Recording of Radiographic Caries at Different Diagnostic Levels, Acta Odont Scand 33:169181, 1975. 27. CARLOS, J.P.: Evaluation of Indices of Malocclusion, Int Dent J 20:606-617, 1970. 28. SOCIALDEPARTMENTET: Tandlakarnas utbildning, Stockholm: Departmentets offsetcentral, Ds S 1975:14.

29. HOJEM, J.: Kjeveortopedisk tannhelsetjeneste i Norge i dag, Norsk Tannlageforen Tid 85: 455-462, 1975. 30. KELLY, J.E.; SANCHEZ, M.; and VAN KIRK, L.E.: An Assessment of the Occlusion of the Teeth of Children, U.S. Dept. of Health, Education and Welfare, DHEW Publication No. (HRA) 74-1612, National Center for Health Statistics, Rockville, Md. 1973. 31. Committee on Handicapping Orthodontic

Conditions, Seriously Handicapping Orthodontic Conditions, Washington, D.C.: National Academy of Sciences, 1976. 32. HELM, S.: Unpublished data. 33. American Association of Orthodontists: The American Association of Orthodontists Study of the Availability of Orthodontic Services, Am J Orthodont 68:326-338, 1975. 34. Ministry of the Interior: Lov nr. 217 af 19. maj 1971 om bornetandpleje. 35. National Health Service of Denmark: Sundhedsstyrelsens vejiledning af 28. januar 1972 om omfanget af og kravene til bornetandplejen. 36. SALZMANN, J.A.: The Threat of "Social Orthodontics" in Prepayment Programs, Am J Orthodont 55:302-303, 1969. 37. HOTZ, R.: Orthodontics in Socialized Dentistry, Europ Orthodont Soc Trans 1975:251254.

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Epidemiology and public health aspects of malocclusion.

Journal of Dental Research http://jdr.sagepub.com/ Epidemiology and Public Health Aspects of Malocclusion Sven Helm J DENT RES 1977 56: C27 DOI: 10.1...
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