Fluoride Action Network

Diagnostic Criteria for Dental Fluorosis: The Thylstrup-Fejerskov (TF) Index

By Michael Connett | July 2012

The traditional criteria (the “Dean Index“) for diagnosing dental fluorosis was developed in the first half of the 20th century by H. Trendley Dean. While the Dean Index is still widely used in surveys of fluorosis — including the CDC’s national surveys of fluorosis in the United States — dental researchers have developed more finely tuned diagnostic scales. These include the “Thylstrup-Fejerskov Index (“TF Index”) and the “Tooth Surface Index of Fluorosis” (“TSIF“). Whereas the Dean Index identifies five types of fluorosis (questionable, very mild, mild, moderate, and severe), the TF Index identifies nine.

Most “questionable” fluorosis under the Dean Index classifies as a TF score of 1; most “very mild” fluorosis classifies as TF 2 or 3; most “mild” fluorosis is a TF 3 or 4, most “moderate” fluorosis is a TF 4, and all severe  fluorosis is a TF 5-9. (Mabelya 1994).

The Thylstrup-Fejerskov (TF) Index
Score Criteria
0 Normal translucency of enamel remains after prolonged air-drying.
1 Narrow white lines corresponding to the perikymata. [Dean = Questionable/Very Mild]
2 Smooth surfaces: More pronounced lines of opacity that follow the perikymata. Occasionally confluence of adjacent lines.Occlusal surfaces: Scattered areas of opacity <2 mm in diameter and pronounced opacity of cuspal ridges.  [Dean = Questionable/Very Mild]
3 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. [Dean = Very Mild/Mild]
4 Smooth surfaces: The entire surface exhibits marked opacity or appears chalky white. Parts of surface exposed to attrition appear less affected.Occlusal surfaces: Entire surface exhibits marked opacity. Attrition is often pronounced shortly after eruption.  [Dean = Mild/Moderate]
5 Smooth surfaces and occlusal surfaces: Entire surface displays marked opacity wtih focal loss of outermost enamel (pits) <2 mm in diameter. [Dean = Severe]
6 Smooth surfaces: Pits are regularly arranged in horizontal bands <2 mm in vertical extension.Occlusal surfaces: Confluent areas <3 mm in diameter exhibit loss of enamel. Marked attrition. [Dean = Severe]
7 Smooth surfaces: Loss of outermost enamel in irregular areas involving <1/2 of entire surface.Occlusal surfaces: Changes in the morphology caused by merging pits and marked attrition. [Dean = Severe]
8 Smooth and occlusal surfaces: Loss of outermost enamel involving >1/2 of surface. [Dean = Severe]
9 Smooth and occlusal surfaces: Loss of main part of enamel with change in anatomic appearance of surface. Cervical rim of almost unafffected enamel is often noted. [Dean = Severe]
Source: Thylstrup and Fejerskov, 1978. As Reproduced in “Health Effects of Ingested Fluoride” National Academy of Sciences, 1993. pp. 171.
Correlating TF Index Score with Dean Index Diagnosis
(Mabelya 1994)
TF Score Dean Index Diagnosis
Questionable Very Mild Mild Moderate Severe
0 90.2% 7.1%
1 6.1% 50.1% 8.8%
2 3.7% 35.7% 41.0% 4%
3 7.1% 42.2% 50.0% 6.1%
4 7.0% 46.6% 93.9%
5-9 100%
No. of Teeth Examined 895 3696 2293 1226 6730
Average TF Value 1.4 2.5 3.4 3.9 *
SOURCE: Mabelya L, et al. (1994). Comparison of two indices of dental fluorosis in low, moderate, and high fluorosis Tanzanian populations. Community Dentistry & Oral Epidemiology 22:415-20.

Summary of TF INDEX:

“The Thylstrup–Fejerskov (TF) index classifies dental fluorosis in terms of its absence (TF 0) through to the presence of opaque lesions (TF 3), which blend to overtake the entire surface of the enamel, thereby producing the appearance of white chalk (TF 4). In more advanced stages, there is a gradual loss of enamel and anatomical dental deformities (TF 5–9).”
SOURCE: Silva de Castilho L, et al. (2009). Perceptions of adolescents and young people regarding endemic dental fluorosis in a rural area of Brazil: Psychosocial suffering. Health and Social Care in the Community Vol. 17, p. 557.

TABLES: CORRELATING cosmetic concerns with TF RANKING:

Results of U.K. National Survey on Aesthetic Perceptions of Dental Fluorosis 
TF Score % of people who find the tooth unattractive % of people who would not be satisfied with appearance % of people who think treatment is needed
1-2 34% 36.1% 28.9%
3-4 63.1% 58.8% 68.5%
>5 99.5% 99.5% 90.6%
SOURCE: Alkhatib MN, et al. (2004). Aesthetically objectionable fluorosis in the United Kingdom. British Dental Journal 197:325-28.
Perception of Fluorosis based on TF Score and Distance
(Edwards 2005)
% who consider teeth “acceptable”
Teeth Only 62 52 22 9 9
Teeth & Lips at Distance 1 80 56 28 13 11
Teeth & Lips at Distance 2 57 48 28 15 16
Teeth & Lips at Distance 3 53 51 28 21 21
Teeth & Lips at Distance 4 55 37 29 30 22
Teeth & Lips at Distance 5 56 36 42 36 41
SOURCE: Edwards M, et al. (2005). An assessment of teenagers’ perceptions of dental fluorosis using digital stimulation and web-based testing. Community Dentistry & Oral Epidemiology 33:298-306.


“It is clear from the results of this study that participants have a preference for white, blemish-free teeth . . . . As fluorosis severity increases (TF 2 or greater), the rating of images (and perhaps the level of acceptance) declines which is in agreement with earlier work.”
SOURCE: McGrady MG, et al. (2012). Adolescents’ perceptions of the aesthetic impact of dental fluorosis vs. other dental conditions in areas with and without water fluoridation. BMC Oral Health 12:4.

“In this study, [enamel defects] had an impact on individuals’ whose sense of self was defined by appearance and who depended on approval from others about their appearance. These young people saw the appearance of their teeth as a threat to their sense of self although, in some cases, the defects on the teeth were normatively assessed as being of mild severity. . . . The variation between individuals and lack of relationship with severity found in this study has implications for discussions on the impact of fluorosis. In the York Review, fluorosis was considered an adverse effect of fluoridation and fluorosis of TFI greater than or equal to 3 was classified as being of ‘aesthetic concern.’ This study provides some evidence that for some young people with TFI greater than or equal to 3, fluorosis is of no concern but may be for others with lower TFI scores.”
SOURCE: Marshman Z, et al. (2008). The impact of developmental defects of enamel on young people in the UK. Community Dentistry & Oral Epidemiology 37:45-57.

“As found in previous studies, it is clear that the present lay observers were able to distinguish different levels of fluorosis when shown photographs of teeth. . . . Acceptability fell as fluorosis increased . . . especially when fluorosis became more severe (TF3 and TF4). . . . The pupils’ feedback was extremely useful, revealing that they believed the ‘marks’ on the teeth to be due to poor oral hygiene, despite a preliminary tutorial which indicated this was not the case.”
SOURCE: Edwards M, et al. (2005). An assessment of teenagers’ perceptions of dental fluorosis using digital stimulation and web-based testing. Community Dentistry & Oral Epidemiology 33:298-306.

“In the present study only relatively few cases of TF grade 3 were found but there was evidence that this level of fluorosis was unacceptable to the parents and similar observations were made by adolescents in Manchester.”
SOURCE: Sigurjóns H, et al. (2004). Parental perception of fluorosis among 8-year-old children living in three communities in Iceland, Ireland and England. Community Dentistry & Oral Epidemiology 32(Suppl 1):34-8.

“The responses of the subjects regarding their desire for treatment matched closely with their opinions on appearancethere; the majority of subjects expressed concern over the appearance of teeth with TF scores of 3 and higher. . . . Using the TF index, there is general agreement that TF scores above 2 may be of aesthetic concern.”
SOURCE: Hawley GM, et al. (1996). Dental caries, fluorosis and the cosmetic implications of different TF scores in 14-year-old adolescents. Community Dental Health 13:189-92.

“The results, based on just over 3000 responses, showed that lay and dental observers could distinguish between different fluorosis levels. In response to a statement that the teeth appeared pleasing, a large majority agreed when the TF score was 0, but agreement declined as the TF score increased; when the TF score was 3, most people disagreed. Similarly, observers felt that the appearance would increasingly embarrass the child as the TF score increased. Observers, except the dentists, tended to feel that higher TF scores indicated neglect on the part of the child.”
SOURCE: Riordan PJ. (1993). Perceptions of dental fluorosis. Journal of Dental Research 72: 1268-74.

Studies Correlating Caries with TF Index

“The children in the high-fluoride area who had dental fluorosis at or above a TF score of 3 had higher levels of dental caries than those with milder degrees of fluorosis present. This finding suggests that if fluoride intake is too high, severe enamel hypomineralization may result in increased caries risk.”
SOURCE: Cortes DF, et al. (1996). Drinking water fluoride levels, dental fluorosis, and caries experience in Brazil. Journal of Public Health Dentistry 56: 226-8