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MEASURING OTHER ORAL CONDITIONS

Malocclusion

Malocclusion is a difficult entity to define, because individual perceptions of what

constitutes a malocclusion problem differ widely. As a result, no generally accepted

epidemiological index of malocclusion has yet been devised. Thoughtful, still-valid

commentaries on the problems of classifying and scoring malocclusions were published

in the 1970s by Jago and Foster.

Angle's classification, which dates from the 19th century, may still be useful in

treatment planning, but is of no use in epidemiological surveys. Most other indexesrecord specific conditions rather than the status of the whole occlusion.

The Malalignment Indexassesses rotation and tooth displacement, whereas the

Occlusal Feature Indexrecords crowding and cuspal interdigitation and vertical and

horizontal overbite. The HLD Indexwas used for assessing treatment needs back when

there was a public orthodontic program in New York State. Grainger developed the

Treatment Priority Index (TPI) for assessing treatment needs; this index was once used

in a national study of orthodontic needs of children. These indexes have not seen much

use in the years beyond their introduction. The Occlusal Index, measures nine

characteristics: dental age, molar relation, overbite, overjet, posterior crossbite,

posterior open bite, tooth displacement, midline relations, and missing permanent

maxillary incisors. It demands a fair degree of examiner skill and training.

The very proliferation of these indexes, all around the same period in history,

underlined the difficulties in measuring this complex condition. The FDI jumped on the

bandwagon with its attempt to develop an internationally accepted index and simplified

method of determining malocclusion. It was not successful; the result was a carefully

qualified method of measuring occlusal traits. It has been used, but seems to be of no

more value than the other indexes described.

WHO, continuing its efforts to provide simplified, standardized basic methods of

recording oral disease, suggests a three category assessment: no anomalies, slight, or

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more serious. Slight is defined as tilted or rotated teeth or mild crowding; the more

serious anomalies, confined to the four incisors, are as follows:

1. Maxillary overjet estimated to be 9 mm or more.

2. Mandibular overjet, anterior crossbite equal to or greater than a full tooth

depth.

3. Open bite.

4. Midline shift estimated to be more than 4mm.

5. Crowding or spacing estimated to be more than 4 mm.

The complexities of malocclusion, and the frustrations that have grown up with

the inadequacies of these indexes, have led many researchers to believe that functional

malocclusion is virtually unmeasurable for epidemiological purposes. In terms of trying

to interpret group data on overbites, crowding, and other clinical conditions, that may

well be true. Orthodontic indexes developed in the late 1980s, however, take a different

philosophical approach in that they assess aesthetics rather than clinical measures of

function. One is the Dental Aesthetic Index (DAI), published in 1986 after years of

testing. The DAI starts from the premise that the impact of malocclusion on other oral

pathology is doubtful, and the main benefit of orthodontic treatment is in the individual's

social and psychological Well-being. The DAI makes objective measurements, but ofaesthetic acceptability according to social norms. Its validation in a number of different

countries provides an impressive scientific base. In Europe, the SCAN (Standardized

Index of Aesthetic Need) index scores a self-perception of dental attractiveness from a

set of photographs. It uses an ordinal scale from 0.5 to 5.0 to determine the individual's

own perception of the aesthetics of his or her own dentition.

Oral Cancers and Clefts

Like other cancers, oral cancer is usually expressed as a proportion or rate. The age

adjusted annual incidence for oral cancer in white patients aged 65 or older, for

example, was 19.9 per 100,000 in 1979-1981. Five-year survival rates are also useful

cancer measures: a five-year survival rate of 67%, for example, means that 67% of

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persons who had the condition diagnosed five years or more ago are still alive. Cancer

is a reportable disease; almost all data on cancer epidemiology comes from analysis of

regional or national registries.

The occurrence of cleft palate is also usually expressed as a proportion; about 1 birth

in 700 exhibits this condition. Soft-tissue abnormalities of various kinds, as well as the

more rare types of oral pathoses, are also most suitably expressed as proportions or

rates. Cleft lip and palate, as a congenital abnormality, is supposed to be recorded on

birth certificates.

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