**4. Remineralization and white spot lesions**

The pathophysiology of dental caries is a continuous process of demineralization and remineralization wherein a net mineral gain is required to prevent lesion progression. To achieve this, the balance between the pathological factors such as fermentable carbohydrate ingestion, salivary function inhibition, acidogenic bacteria and protective factors like antibacterial agents, composition and rate of flow of saliva, fluoride and diet needs to be maintained [28]. Fermentation of carbohydrates leads to formation of organic acid by acidogenic bacteria that cause diffusion of calcium and phosphate ions out of the tooth leading to the formation of white spot lesions at an early stage, which further progresses to cavitation if the process continues [5]. This can be prevented by remineralization or mineral gain which is defined as the process whereby calcium and phosphate ions are supplied from a source external to the tooth to promote ion deposition into crystal voids in demineralized enamel [29].

Saliva is the major source of these minerals consists of calcium (Ca), phosphate (P), fluoride (Fl) ions in addition to salivary proteins such as proline-rich proteins, statherin, histatins which increases the concentration of calcium ions and salivary enzymes such as lysozymes and peroxidases. Normally the saliva is supersaturated with calcium and phosphate ions but when the pH decreases (<5.5) due to the fermentation of carbohydrates, as mentioned above, this equilibrium is lost and demineralization starts. To prevent this, saliva acts as a remineralizing agent by providing Fl ions to regain homeostasis and thereby acts by preventing demineralization, promoting remineralization and having an antibacterial effect. Therefore, a variety of treatment modalities are available to treat initial carious lesions also known as white spot lesions based on the above theory, which will be discussed in the upcoming treatment modalities [30].

### **5. Treatment**

#### **5.1 Various methods of treatment**

There are various treatment options available to treat WSLs depending on their extent and severity [31] (**Table 8**).

#### *5.1.1 Micro-abrasion*

Micro-abrasion is the application of an acidic and abrasive compound to the surface of the enamel. The micro abrasion process removes small amounts of surface enamel but also leaves a highly polished enamel surface. The micro-abraded enamel surface does not have the ideal enamel surface appearance as interprismatic spaces would be absent.


#### **Table 8.**

*Various WSLs and their treatment options.*

The micro-abrasion process abrades surface enamel while compacting calcium and phosphate into the interprismatic spaces. This polished surface reflects light differently than natural enamel. Therefore, a portion of the whitened enamel is removed and a portion is camouflaged by the highly polished surface.

Following this procedure, a 4-min 2% sodium fluoride treatment is recommended. If the micro-abrasion technique does not produce optimal aesthetic results, and if the whitened enamel is still prominent, vital tooth bleaching should be considered [32].

#### *5.1.2 Whitening*

Also known as vital tooth bleaching or bleaching. It is the process of lightening the colour of enamel. To date, there are two techniques of tooth whitening that have been prescribed:

