It is related to prolonged exposure to fluoride, especially during childhood, so it is important as oral specialists to know how to prevent it, detect it early and intervene appropriately in each case.

What is dental fluorosis?

Dental fluorosis is an irreversible alteration in the development of enamel caused by excessive intake of fluorides during tooth formation. It manifests itself through opaque white spots or mottled striations that may turn yellow or brown in the most severe cases. They can also cause cracks in the enamel and deformities that can affect both anterior and posterior teeth.

In most cases, it is mainly a cosmetic problem, although it can have a great impact on the self-esteem and social interactions of those who suffer from it, leading to the search for corrective dental interventions.

While fluoride is essential for caries prevention, its uncontrolled use can have adverse effects on enamel structure. This is visible in regions where drinking water naturally contains high concentrations of fluoride ion. Although fluorosis tends to be endemic in these areas, it is not an infectious condition.

Development of fluorosis during tooth enamel formation

Amelogenesis, or the development of tooth enamel, takes place in several stages: morphogenesis, differentiation, secretion, maturation, protection and demolysis. Throughout these phases, a complex protein matrix is produced, composed of amelogenin, ameloblastin, enamelin and tuftelin, as well as enzymes such as metalloproteinase MMP-20 and kallikrein (KLK4), which help in the progressive degradation of this matrix. This matrix serves as the basis for hydroxyapatite crystals, the mineral component of enamel, to grow in an orderly fashion to consolidate a resistant structure.

Fluorosis affects the maturation stage, when excess fluoride interferes with vesicular transport of proteins and slows their degradation, which prevents good mineralization of the enamel, which becomes weaker and more porous. It usually affects homologous teeth.

Causes of fluorosis and main risk factors

The main risk factors for fluorosis are related to overexposure to fluoride during childhood. Children under 8 years of age are the most vulnerable, since at this stage the formation of dental enamel has not been completed.

Some risk factors for dental fluorosis may include:

• Access to drinking water with high levels of fluoride.
• Taking fluoride supplements unnecessarily.
• Infant formulas prepared with fluoridated water.
• Food and beverages processed with fluoridated water.

Child malnutrition is another cause that can aggravate the effects.

In addition, it is essential to inform parents about the recommended amounts of fluoride in toothpaste at each stage of childhood. This knowledge will allow them to ensure that children are not exposed to fluoride levels higher than those appropriate for their development.

Diagnosis and classification of fluorosis

Fluorosis is detected visually by clinical inspection of the enamel, analyzing its opacity, pigmentation and texture. To know how mild or severe it is, there are multiple classification indexes. Two of the most commonly used indices are:

Dean's Community Fluorosis Index (CFI)

The Dean index, developed by H. Trendley Dean, is recommended by the World Health Organization (WHO). It is common in epidemiological studies because of its simplicity and classifies fluorosis into six categories:

• Normal: White enamel, glossy.
• Questionable: Slight loss of translucency, few white spots.
• Very slight: White opacities covering less than 25% of the tooth surface.
• Mild: White spots covering up to 50% of the surface.
• Moderate: Brown stains and worn enamel.
• Severe: Major structural defects, such as cracks and extensive staining.

Thylstrup and Fejerskov index (TF)

This classification is more detailed, based on the histopathology of fluorosis, describing microscopic and macroscopic changes, so it is the most useful for planning individualized clinical treatments. It classifies lesions on a nine-grade scale:

• TF1-TF2: Slight white opacities.
• TF3-TF4: More noticeable striations, slight loss of enamel.
• TF5-TF6: Brown pigmentation, surface irregularities.
• TF7-TF9: Remarkable wear, deep cracks and fractures.

Available treatments for fluorosis according to its severity

Following the Thylstrup and Fejerskov (TF) Index, we can see below some approaches for the different levels of dental fluorosis:

Mild cases

In categories TF1 and TF2, tooth whitening helps to reduce the contrast between the areas affected by fluorosis and the healthy ones. Agents such as hydrogen peroxide or carbamide peroxide are used, capable of penetrating the enamel and breaking down the pigments responsible for the discoloration. It is safe and non-invasive and can be enhanced with LED light.

It should be taken into account that tooth whitening can cause postoperative sensitivity, so it is advisable to perform microabrasion in certain cases. For this purpose, hydrochloric or phosphoric acid is used with abrasives, such as silicon carbide or pumice stone, in order to remove the superficial layer of the enamel.

Moderate cases

In moderate grades TF3 and TF4, it is common to combine macroabrasion, microabrasion and tooth whitening treatments. Although macroabrasion is usually recommended for severe cases, it can be used to remove rough areas of tooth enamel using diamond or carbide burs, followed by soft abrasion and a final esthetic treatment.

In certain cases, minimally invasive techniques such as low viscosity light-curing resins, which can penetrate the porous structure of tooth enamel to visually mask lesions, can also be used.

Severe cases

For cases ranging from TF5 to TF9, where there is loss of tooth structure, a composite resin restoration is recommended to replace the affected areas. In more extreme cases, we resort to porcelain veneers, which are minimally invasive and give good esthetic results if there is sufficient structure, or directly to full crowns.

In short, dental fluorosis can be treated even though it is an irreversible condition. The most important thing is to make an accurate diagnosis to determine the severity of the case in question before any treatment is carried out. Minimally invasive treatment is preferable in order to preserve tooth structure. This combination of factors safeguards the function and esthetics of patients' teeth and helps restore their self-esteem.

In addition, dental fluorosis underscores the need for parental education as a preventive measure. With regular visits to the dental clinic it is possible to detect signs early enough to monitor fluoride exposure and recommend the most appropriate products accordingly. The key is to find a balance between the benefits of fluoride for caries prevention and the risk of developing fluorosis.