**3. Diagnosis**

#### **3.1 Importance**

The clinical manifestation of WSL starts as early as 4 weeks in case of orthodontic treatment. Unnoticed WSL can lead to the disintegration of enamel surface followed by carious lesion which may require aesthetic restorations or in more advanced cases a prosthodontic intervention. This is more commonly seen in high caries risk individuals. In people with low caries activity, the repair mechanisms help in the potential healing of the lesion.

Hence, it is important to plan the treatment according to the caries activity in individuals after a proper diagnosis. The emphasis given to new technologies has made it possible to detect initial lesions before they turn into irreversible cavitation [19].

#### **3.2 Methods**

The ideal method for the detection of WSLs should have a high level of sensitivity (the ability to detect disease when present) and specificity (the ability to confirm that disease is absent).

#### *3.2.1 Conventional methods*

The conventional methods of diagnosing WSLs are visual examination, tactile examination with probing and digital photographic examination. These methods are simple to use, inexpensive, and clinically valid.

#### *3.2.1.1 Visual examination*

For visual examination, the tooth surface must be air-dried for at least 5 s after cleaning with pumice under adequate light to visualise the WSLs. The opacities on the enamel surface will not be visible and the lesion cannot be distinguished the enamel gets wet. Because the micro pores in the surface are filled with water and the refractive index of enamel becomes 1.33, which is close to that of healthy enamel. On the other hand, after the air drying, the pores within the lesion will be filled with air, which has a refractive index of 1.0. Hence, the opaque enamel lesions become evident and distinct from the healthy enamel surface [20].

#### *3.2.1.2 Photographic examination*

The recommended specifications for taking intraoral images are 100 mm macro lens with a small aperture of 25. While taking a photograph the teeth should be inaccurate axial position i.e. the occlusal plane should be parallel to the horizontal plane. Although, these methods are useful in the detection, they do not quantify the depth of the lesions [21].

#### *3.2.2 Contemporary methods*

They are more consistent and enhanced sensitivity towards lesion diagnosis when compared to the conventional methods. This can be classified as:

#### *3.2.2.1 Electric resistance (electronic conductance and impedance)*

An intact enamel surface is a good electrical insulator due to its high inorganic content. Demineralization causes loss of minerals, resulting in increased porosities filled with saliva, this acts as a conductive pathway for electric current. The electric conductivity is directly proportional to the amount of demineralization [22].

E.g., Electrical Caries Monitor, Caries Meter L, CarieScan Pro.

#### *3.2.2.2 Fluorescence*

The autofluorescence of tooth tissue decreases as the demineralization activity increases .This could be attributed to protoporphyrin, a photosensitive pigment present in demineralized dental tissues that are generated due to bacterial metabolic activity [23].

E.g., Fibre-Optic Transillumination (FOTI), Digital imaging Fibre-Optic Transillumination (DIFOTI), Near-infrared digital imaging transillumination (NIDIT), Laser fluorescence (LF), Quantitative light-induced fluorescence (QLF), and Multiphoton imaging

#### *3.2.2.2.1 Fibre-Optic Transillumination (FOTI)*

The concept of transillumination for the detection of WSL is based on the refractive index of different tooth structures [23]. The refractive index will vary when light is passed through different tissues. The demineralized enamel appears as a grey hue

*White Spot Lesions and Remineralization DOI: http://dx.doi.org/10.5772/intechopen.101372*

whereas dentin gives an orange-brown or a bluish hue. Due to the intra and interobserver disparity, Digital imaging FOTI (DIFOTI) was developed in the 1990s. In DIFOTI the images are captured and stored by a CCD camera. Another advanced method is near-infrared digital imaging transil-lumination (NIDIT). In this technique two near-infrared laser diodes are used, which allows superior light to spread into the dental tissues and get better picture quality than visible light [23].

#### *3.2.2.2.2 Laser fluorescence (LF)*

LF uses a red wavelength of 655 nm for caries detection [23]. It is based on the principle when light is applied to the tooth surface, the caries-related changes in the tooth tissues lead to an increase in fluorescence. This can be translated into numeric values, which can vary from 0 to 99.

For example, in DIAGNOdent pen scores from 0 to 10 are interpreted as healthy, while scores above 30 indicate a lesion that requires restorative treatment [23].

#### *3.2.2.2.3 Quantitative light-induced fluorescence (QLF)*

It measures the percentage of fluorescence change in demineralized enamel. This technique allows us to detect the lesion activity as well as to predict the lesion progression. Since demineralized tissue has limited penetration of light, it gives a dark image in QLF [24].

#### *3.2.2.2.4 Multiphoton imaging*

Unlike conventional fluorescence imaging, it uses two infrared photons simul¬taneously to excite a fluorescent compound in the tooth. Caries will appear as a dark form within a bright fluorescing tooth. It also helps to collect information from carious lesions up to 500 μm of depth [25].

#### *3.2.2.3 Thermography*

The concept of thermography for the detection of early enamel caries has been discovered by Kaneko in 1999. It measures the lesion activity rather than its presence or absence. This is based on the principle of change in thermal radiation energy that occurs when fluid is lost from a lesion by evaporation just as in WSLs [25].

E.g., Infrared thermography, Frequency-domain infrared photothermal radiometry and modulated luminescence (PTR/LUM).

#### *3.2.2.4 Terahertz imaging*

Terahertz parametric imaging (TPI) has great potential in the diagnosis of WSL [25]. Terahertz radiation is located between the high-frequency microwave and long-wavelength infrared region of the spectrum. This helps identification of infected tissue inside the tooth followed by 3D plotting which can be applied to obtain the depth of the demineralized tissue. It can also be used to measure the remineralization of enamel [25].
