Dental Fluorosis


Introduction
  • 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

Advantages
  • 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
Disadvantages
  • 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.



References:

American Dental Association (2005). Fluoridation Facts. Retrieved Oct 23, 2009 from http://www.ada.org/public/topics/fluoride/facts/fluoridation_facts.pdf

D. LaPointe, R. Anderson. (2009). Definitions. Retrieved Oct 24, 2009 from http://cariology.wikifoundry.com/page/Dental+Fluorosis

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 http://www.palmbeachporcelainveneers.com/

PUB, Singapore's water agency (2008). Water treatment. Retrieved Oct 23, 2009 from http://www.pub.gov.sg/general/Pages/WaterTreatment.aspx

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.









Links

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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