A system of defining the severity of chronic fluoride toxicity based on enamel defects. The most commonly used indices are the Dean Index [Dr Trendley Dean (1893–1962), American dentist] and the Thylstrup–Fejerskov Index named after A. Thylstrup and O. Fejerskov. The Dean Index grades the enamel lesions according to the degree of severity described. The Thylstrup–Fejerskov Index uses a numerical classification.
http://www.bfsweb.org/facts/dental_fluoro/f_dental_fluoro.htm Information on dental fluorosis classification from the British Fluoridation Society.
The Dean fluorosis index
Criteria for Dean fluorosis index
The enamel represents the usual translucent type of structure. The surface is smooth, glossy, and usually of a pale creamy-white colour.
The enamel discloses slight aberrations from the translucency of normal enamel, ranging from a few white flecks to occasional white spots. This classification is utilized in those instances where a definite diagnosis of the mildest form of fluorosis is not warranted and a classification of ‘norma’ is not justified.
Small, opaque, paper-white areas scattered irregularly over the tooth but not involving as much as 25% of the tooth surface. Frequently included in this classification are teeth showing no more than about 1–2mm of white opacity at the tip of the summit of the cusps of the bicuspids (premolars) or second molars.
The white opaque areas in the enamel of the teeth are more extensive but do not involve as much as 50% of the tooth.
All enamel surfaces of the teeth are affected, and the surfaces subject to attrition show wear. Brown stain is frequently a disfiguring feature.
Includes teeth formerly classified as ‘moderately severe and severe’. All enamel surfaces are affected and hypoplasia is so marked that the general form of the tooth may be affected. The major diagnostic sign of this classification is discrete or confluent pitting. Brown stains are widespread and teeth often present a corroded-like appearance.
Source: Dean, 1942. As reproduced in ‘Health Effects of Ingested Fluoride’, National Academy of Sciences, 1993, p. 169.
The Thylstrup–Fejerskov index
Clinical criteria and scoring for the TF (Thylstrup–Fejerskov) index
Normal translucency of enamel remains after prolonged air-drying.
Narrow white lines corresponding to the perikymata.
Smooth surfaces: More pronounced lines of opacity that follow the perikymata. Occasionally confluence of adjacent lines.
Occlusal surfaces: Scattered areas of opacity <2mm in diameter and pronounced opacity of cuspal ridges.
Smooth surfaces: Merging and irregular cloudy areas of opacity. Accentuated drawing of perikymata often visible between opacities.
Occlusal surfaces: Confluent areas of marked opacity. Worn areas appear almost normal but usually circumscribed by a rim of opaque enamel.
Smooth surfaces: The entire surface exhibits marked opacity or appears chalky white. Parts of the surface exposed to attrition appear less affected.
Occlusal surfaces: Entire surface exhibits marked opacity. Attrition is often pronounced shortly after eruption.
Smooth surfaces and occlusal surfaces: Entire surface displays marked opacity with focal loss of outermost enamel (pits) <2mm in diameter.
Smooth surfaces: Pits are regularly arranged in horizontal bands <2mm in vertical extension.