**6. Clinical status quo**

In terms of the clinical status quo for prevention of incipient caries lesions during orthodontic treatment, one has to first reference the AAO sponsored informed consent form, in which there is an emphasis on excellent oral hygiene, regular visits to the general dentist, and access to fluoridated water (AAO, 2009). In looking at practice trends, a recent survey by the Journal of Clinical Orthodontics does provide some information about the usage of some of the preventive measures previously outlined (Keim *et al.,* 2008). Despite its proven efficacy, only 9.3% of orthodontists deliver fluoride varnish to their patients. The article also mentions that only 7.4% of orthodontists employ the fluoride-releasing glass ionomer adhesive for bracket bonding, which is understandable given its questionable physical properties. There were no data in the article detailing the usage of ACP products or resin sealers. In any event, the fact that more than half of orthodontic patients develop incipient

White-Spot Lesions in Orthodontics: Incidence and Prevention 321

application of computer imaging make microradiography a standard method used in caries

Polarized light evaluations of enamel sections have been useful in describing the early caries lesion and alterations in structure upon further demineralization or remineralization. Generally, it provides information on absorption color and boundaries between minerals of differing refraction indices. Materials such as enamel act as beam splitters and divide light rays into two parts. Polarized Light microscopy (PLM) in turn exploits the interference of split light rays, as they are reunited along the same optical path to extract information about materials. Essentially, polarized light microscopy allows the visualization of areas with different porosities. The histologic features seen under a polarized light microscope allow the examiner to distinguish carious and non-carious enamel by their respective distribution of pores (Gwinnett, 1966). Polarized light examination of enamel specimens is a wellestablished procedure in which it is customary to view quinoline-imbibed sections orientated so that normal enamel is blue/green in color (Gilmour and Edmunds, 1998).

Quantitative Light-induced Fluorescence (QLF) is one method of assessing levels of enamel demineralization. With QLF, real-time fluorescent images are captured into a computer and stored in an image database. Optional quantitative analysis tools enable the user to quantify parameters like mineral loss, lesion depth, lesion size, stain size and severity with high precision and repeatability. The QLF method is based on the auto-fluorescence of teeth. When teeth are illuminated with high intensity blue light they will start to emit light in the green part of the spectrum. When enamel demineralization takes place, minerals are replaced mainly by water from saliva, causing a decrease in the light path in the tooth substance. This results in less light absorption by enamel. Because fluorescence is a result of light absorption, the intensity of fluorescence decreases in demineralized regions of the enamel, which appear darker than sound tooth structures (de Josselin *et al.,* 1995; al-Khateeb *et al.,* 1998; Rousseau *et al.,* 2002). Thus, the fluorescence of the dental tissue has a direct relation with the mineral content of the enamel. The effectiveness of QLF for measurement of enamel demineralization has been demonstrated in several studies. The use of QLF allows for quantitative analysis has been reported to be well correlated (0.73-0.83) with the degree of mineral loss from early enamel lesions *in-vitro* when measured by longitudinal microradiography. (Hafstrom-Bjorkman *et* al., 1992; Emami *et* al., 1996; Lagerweij *et al*., 1996). The use of QLF as a method of following caries development during orthodontic treatment has been suggested and encouraged by the results of several *in-vitro* studies. (Benson *et al*., 2003 and Pretty *et al*., 2003). Recent studies also indicate that QLF is suitable for *in-vivo* monitoring of mineral changes in incipient enamel lesions (Van der Veen *et al*.,

Confocal Laser Scanning Microscopy (CLSM) is yet another method of assessing enamel demineralization. This technique accelerates and simplifies the measuring of mineral loss. The enamel specimens are sectioned in half, stained with fluorescent dye, and analyzed

research for the assessment of lesion profiles.

**8.3. Quantitative light-induced fluorescence** 

2000 and Al Khateeb *et al*., 2002).

**8.4 Confocal laser scanning ,icroscopy** 

**8.2 Polarized light microscopy** 

caries lesions (Gorelick *et al.,* 1982; Richter *et al.,* 2009) and that only 9.3% of orthodontists give their patients fluoride varnish (Keim *et al.,* 2008), raises questions about emphasis of preventive care in today's orthodontic practice.
