Studies on the remineralization of white spot lesions : longitudinal assessment with quantitative light-induced fluorescence

Sammanfattning: The global aim of this work was to develop and test the light induced fluorescence method using either laser light or a regular, i.e. noncoherent light source for quantification of mineral changes in white spot lesions. Validation studies were carried out to establish the correlation between fluorescence loss and mineral loss. One study was performed to investigate the porosity of white spot lesions of different origins and its effect on the optical characteristics of a white spot lesion. Further, the remineralization process of "open lesions" was studied under different conditions: the effect of acid etching of white spot lesions was investigated in presence or absence of fluoride in an in vitro study. The effect of fluoride supplementation at regularly use of F dentifrice on the remineralization of white spot lesions was investigated in an in situ model. Moreover, the mineral changes in white spot lesions developed in vivo during orthodontic fixed appliance treatment were followed longitudinally. It was concluded that the laser fluorescence method is sensitive and valid for the quantification of mineral loss in natural incipient enamel lesions. Changes in enamel fluorescence reflected changes in mineral content during de- and remineralization processes in the enamel providing the basis for a quantitative method for assessment of mineral changes to a depth of about 450 µm in vitro, in situ, and in vivo. The light induced fluorescence method could operate using monochromatic laser light at the wave length 488 nm, or with a regular (noncoherent) white light source emerging from a Xenon gas-chargeable lamp. Addition of fluoride for the remineralization of "open lesions" caused redistribution of the minerals in the white spot lesions and blockage of their surface layer. In healthy young adults with normal salivary flow and good oral hygiene, fluoride supplementation to the regular use of F dentifrice did not further enhance the remineralization of artificially induced subsurface enamel lesions. Acid etching of white spot lesions enhanced the remineralization process of these lesions. Full remineralization of the so called "open lesions" was not obtained neither in vitro nor in the in vivo environment. Using the QLF method, it would be possible to register the rate of dehydration of a white spot lesion, thus providing information about the nature of that lesion regarding the characteristics of its surface layer.