Dental Fluorosis

  • An abnormal condition caused by excessive (chronic, low-dose) intake of fluorides, characterized in children by discoloration and pitting of the teeth and in adults by pathological bone changes.
  • Fluorosis is irreversible and only occurs with exposure to fluoride when enamel is developing.
  • Main problem: porosity in enamel leading to mottling and more brittle enamel (higher tendency of mechanical damage) (D. LaPointe, R. Anderson, 2009)
Water fluoridation in Singapore
  • Earliest exposure of children to fluoride – consumption of fluoridated water
  • Water fluoridation reaches out to majority of the population
  • Sodium silicofluoride is added to the water on its way from the filters to the clear water tank. Fluoridation is a requirement by the Ministry of Health and has been a practice since 1957. It helps in the prevention of dental caries.

Chemical & Physical Characteristics (In mg/l where applicable) *Water from Choa Chu Kang & Bedok Waterworks Water from Other Waterworks WHO Guideline Values (2004)
Fluoride (as F) 0.4 – 0.6 0.4 – 0.6 1.5

Fig 1. Table showing fluoride levels in Singapore waterworks.
(PUB, Singapore's national water agency, 2008)

What is Dental Fluorosis
  • Normal teeth enamel
    • Creamy-white, slightly translucent
    • Composed mainly of hydroxyapatite Ca5(PO4)3(OH) arranged in hexagonal crystals
Normal enamel

Fig 2. Normal teeth with slightly translucent enamel.
(Michael I. Barr, 2008)

  • Fluorosed enamel
    • Porous – porosity along the striae of Retzius causes the opacity observed in fluorosed teeth
Dental Fluorosis - Cariology
Fig 3. Alignment and structure of perikymata and striae of Retzius.
(Jacopo Moggi-Cecchi, 2001)

Dental Fluorosis - Cariology

Fig 4. Diagram showing stages of fluorosis. Increase in porosity corresponds to increase in severity of fluorosis. Zone of porosity extends from enamel surface to enamel-dentine junction with increase in severity of fluorosis. (Fejerskov and Kidd, 2008)

Factors leading to porosity of enamel

  • Hypomineralisation of enamel during amelogenesis disrupting maturation of pre-eruptive teeth
  • Maturation stage of amelogenesis – enamel matrix proteins are gradually removed while mineralisation happens
  • Fluorapatite formation preferential
    • Nature of fluoride ion – small, highly electronegative, high charge density
    • Negative charge density allows a better fit in the lattice compared with the larger asymmetric OH- ion therefore preferential to OH- ions
    • The electrostatic attraction between Ca2+ and the F- will be greater than, between Ca2+ and OH–, making the fluoridated apatite lattice more crystalline and more stable. As a consequence it is less soluble in acid.

  • Excess fluorosis/fluorapatite formation in developing enamel
    • Matrix removal is a necessary prerequisite for unimpaired crystal growth in enamel
    • Fluorosed enamel retains immature matrix proteins (ameloblastin and amelogenin) leading to accumulation of these proteins on the developing enamel
    • Results in incomplete crystal growth at mainly the prism peripheries
    • Causes porosity - widening gaps between the enamel rods and enlarging inter-crystal spaces in parts of the rod
    • Normal close juxtaposition and interlocking of hydroxyapatite crystals does not occur

Signs of Dental Fluorosis
  • Opaque, chalky-white colour
    • About 1 ppm of fluoride in 1ppm of water supply
    • Light refractivity is greatly reduced mainly due to porosity
  • Extent of fluorosis (i.e. porosity and opacity) increases with increase in fluoride exposure during tooth development
  • Important to note that pitting and loss of enamel normally occurs post-eruptively
  • Mild form
    • Porous enamel
    • Opacity in the form of white striations on the perikymata
    • May have light yellow specks or blotches as well
  • Severe form
    • Entirely opaque, white surface
    • Mottling (dark yellow to brown spots and pits)
    • Fluorosed enamel is structurally weak (brittle) and prone to erosion and breakage, especially when drilled and filled

Classification of Dental Fluorosis

  • Dean’s Index
    • H.T. Dean's fluorosis index was developed in 1942
    • An individual's fluorosis score is based on the most severe form of fluorosis found on two or more teeth
    • Entirely based on clinical appearance without deep understanding of pathology involved
Dean’s Index
Classification Criteria – description of enamel
Normal Smooth, glossy, pale creamy-white translucent surface
Questionable A few white flecks or white spots
Very Mild Small opaque, paper white areas covering less than 25% of the tooth surface
Mild Opaque white areas covering less than 50% of the tooth surface
Moderate All tooth surfaces affected; marked wear on biting surfaces; brown stain may be present
Severe All tooth surfaces affected; discrete or confluent pitting; brown stain present

Fig 5. Dean's Index. (American Dental Association, 2005, pg. 28-29 )

  • Thylstrup-Fejerskov Index
    • An extension of Dean’s Index –more pathologically defined
TF (Thylstrup-Fejerskov) Index
Score Criteria
0 Normal translucency of enamel remains after prolonged air-drying.
1 Narrow white lines corresponding to the perikymata.
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.
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.
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.
5 Smooth surfaces and occlusal surfaces: Entire surface displays marked opacity wtih focal loss of outermost enamel (pits) <2 mm in diameter.
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.
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.
8 Smooth and occlusal surfaces: Loss of outermost enamel involving >1/2 of surface.
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.

Fig 6. Thylstrup-Fejerskov Index. (Thylstrup A, Fejerskov O, 1978)

Dental Fluorosis - Cariology

Fig 7. Diagrammatic illustration of fluorosed teeth according to the TF Index (TF 1-9). (Fejerskov and Kidd, 2008)

Dental Fluorosis - Cariology
Fig 8. Examples of fluorosed teeth with corresponding TF ratings. (Fejerskov and Kidd, 2008)

How fluorides affect your teeth - Advantages vs Disadvantages

  • Systemic & topical action by fluoride on cariology prevention (American Dental Association, 2005)
  • Systemic: when flourides are ingested into your body and there is uptake by developing teeth
    • Structural protection - Ingestion in young children with developing teeth leads to incorporation of flouride into their teeth enamel (mainly) and dentine making it stronger and more acid-resistant
    • Fluorapatite formation (T. Aoba & O. Fejerskov, 2002)
      • Adjacent hydroxyls will hydrogen bond to the fluoride ion
      • Protons associated with acid phosphate groups more tightly orientated towards the fluoride ion
      • Fluorapatite is more stable, less soluble, more resistant to acid and therefore prevents caries
    • Systemic leading to topical - ingested flouride also expressed in saliva which bathes teeth in flouride that can be used in remineralisation to prevent development of caries
  • Topical: when flourides are externally applied on post-eruption teeth to produce a protective external coat
    • Develops outer layer that is decay resistant
    • Reduce demineralisation effects of bacterial or acidic action
    • Enhances remineralisation of enamel surface quickly to prevent the development and worsening of caries
  • Excessive fluoride intake when young may result in severe fluorosed teeth i.e. severe porosity of teeth
    • Enamel may become brittle and unable to withstand pressure
      • Difficult for dental procedures which require drilling
    • Enamel mottling - cosmetic appearance reduces aesthetic appeal of teeth
      • No permanent cure for enamel mottling
Note: For more information on the effects of fluoride on teeth, refer to the section on Fluorides.


American Dental Association (2005). Fluoridation Facts. Retrieved Oct 23, 2009 from

D. LaPointe, R. Anderson. (2009). Definitions. Retrieved Oct 24, 2009 from

Fejerskov and Kidd, (2008). Dental Caries. The Disease and its Clinical Management 2nd edition. Oxford: Blackwell Munksgaard Ltd. pg294-303

Jacopo Moggi-Cecchi (2001). Human evolution: Questions of growth. Nature 414, 595-597.

Michael I. Barr (2008). Palm Beach Porcelain Veneers. Retrieved Oct 23, 2009 from

PUB, Singapore's water agency (2008). Water treatment. Retrieved Oct 23, 2009 from

T. Aoba and O. Fejerskov (2002). Dental Fluorosis: Chemistry and Biology. Critical Reviews in Oral Biology & Medicine, 13(2): 155-170

Thylstrup and Fejerskov.(1978). Clinical appearance of dental fluorosis in permanent teeth in relation to histologic changes. Community Dent Oral Epidemiol;6(6):315-28.


An Introduction | Tooth Anatomy and Histology | Dental Caries | Dental Caries - An Infectious Disease or a Chronic Disease |

Early Caries and Enamel Changes | Caries Progression and Dentine Changes | Pulpo-dentinal Changes

Root Surface Caries and Changes in the Cementum | Dental Fluorosis | Erosion of the Teeth | Conclusion

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