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)
- 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
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
- Porous – porosity along the striae of Retzius causes the opacity observed in fluorosed teeth
Fig 3. Alignment and structure of perikymata and striae of Retzius.
(Jacopo Moggi-Cecchi, 2001)
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
- 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
- H.T. Dean's fluorosis index was developed in 1942
| 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)
Fig 7. Diagrammatic illustration of fluorosed teeth according to the TF Index (TF 1-9). (Fejerskov and Kidd, 2008)
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
- 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
- Difficult for dental procedures which require drilling
- Enamel mottling - cosmetic appearance reduces aesthetic appeal of teeth
- No permanent cure for enamel mottling
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