Quantitative Light-Induced Fluorescence

QLF is applied to measure the changes in the enamel fluorescence of white spot lesions and to quantify its reversal or progression. A xenon arc lamp is used as a light source, and an optical filter system, producing blue light with a maximum wavelength of 370 nm, is connected to the microscope by a liquid light guide (Inspektor Research Systems BV, Amsterdam, The Netherlands). The fluorescence emitted by the tooth is collected with a charged coupled device (CCD)-video microcamera (Panasonic WV-KS 152, Matsushita Electric Industrial Co, Ltd, Osaka, Japan) equipped with high pass yellow filter (γ>520 nm) to exclude any excitation or ambient light that may reach the detector and a special dental mirror to reflect the image of the lesion connected to the camera [14].

After drying the tooth surface (for 5 s), images of clinically detected white spot lesions are obtained by QLF, in a completely dark environment. A computer program (Software Inspektor QLF 2.00f; Inspektor Research System BV, Amsterdam, The Netherlands) is utilized to display, store, browse, and analyze the images. The QLF parameters are: 1) the area of the lesion (white spot area [WS], mm²) that is the sum of all points within the lesion with fluorescence loss > 5%; and 2) the mean fluorescence loss (ΔF, %, detection threshold of 5%) [20].

The QLF analysis was performed at baseline and after 1 month. The differences between the 1 month and baseline values were calculated as follows: ΔWS area = WS area baseline – WS area after 1 month (the same for ΔΔF), where ΔWS is the variation of the white spot lesion area and ΔΔF is the variation of the mean fluorescence loss. The data were analyzed using the Kruskal-Wallis test. This analysis will be repeated after the 6th, 12th, and 18th months of the treatment by BMS.