**2. Aetiology/causes**

WSL usually has a multifactorial manifestation. It is vital to ascertain the causes, before planning and providing treatment options to the patient. This is because the results of the treatment will vary depending on the substructure available [8–12].

Causes of WSL include,


#### **2.1 Fluorosis**

During the phase of enamel mineralisation, if there is excessive fluoride exposure, and as a result the enamel would become hypomineralized, leading to a condition called fluorosis. Studies conducted by McKay and Black [11] conclude, that fluoride can be beneficial or harmful depending on certain factors, like the age, dosage, and health of the patient [13]. In preventive measures, many times a dentist uses fluoride to reinforce the enamel, hence a controlled dosage is required to make the use of fluoride extremely beneficial (**Figure 1**).

It is observed that fluorosis generally appears symmetrically and can present itself in 3 ways i.e., white spots, brown spots or pitting. In milder cases, it presents itself as narrow white lines, following the perikymata, cuspal snow capping or snowflaking whereas, in severe cases the brown discoloration is apparent due to the infiltration of chromophoric proteins [3] (**Table 1**). In any case, WSL and fluorosis are two different entities and can be differentiated as follows [14]:

### **WSL:**

