QLF™ concept: a blue excitation light beam (B) with peak intensity at 405 nm illuminates a tooth; a yellow filter (F) transmits green (G) and red (R) fluoresced photons to the eye or camera.
Left: white light image of a premolar visualizing an initial caries lesion visual as a white spot. See encircled area Right: fluorescence image shows GF: the white spot is now shown as a dark spot.
Green Fluorescence (GF) principle shown schematically: blue photons (B) enter the tooth and scatter in enamel and fluoresce green (G) at the dentine (D) and enamel (E) junction DEJ. Where there is a white spot below in the enamel part, blue rays scatter and will not reach the DEJ; fluoresced photons will scatter back at the white spot, both effects resulting in a visual dark spot when viewed with QLF™.
RF. Bacterial metabolites as in cavities and plaque or calculus on the tooth fluoresce bright red. See the areas indicated by the arrows.
Red (R) and Green (G) Fluorescence schematically: the red fluorescence (RF) is caused by excitation of red extrinsic fluorophores from bacterial metabolites.
Monte Carlo result of photons which scattered and fluoresced inside a tooth enamel block with inside a block of bacterial metabolites at a depth of 0.250 mm below the surface, as shown at the left top of the figure. The block in the middle shows green and red fluoresced photons that emerged out of the surface. is the number of photons used, the number of fluoresced red photons, the number of fluoresced green photons.
Monte Carlo graph of the red over green number of photons (R/G) that emerged out of the surface in the enamel and bacterial metabolite model of Fig. 6.
Example of sound and clean teeth as viewed with QLF™.
Example of removable signs of bacterial activity. The same element before (left) and after (right) brushing. The arrows point at the areas of interest,
Locations with high concentration of porphyrines are clearly visible as brightly red areas. Plaque is shown in the left image and calculus in the right one.
Example of a clear white spot along the gingival margin together with (nonremovable) signs of bacterial activity inside the tooth (left, see arrow). Example of a leaking margin of a composite filling infiltrated with nonremovable plaque (middle, see arrows). Right image: area within the dotted ellipse: occlusal surface showing discoloration at the dark fissure line and signs of bacterial activity underneath the surface. After opening the fissure a dental carious lesion was found underneath.
Left: example of a sound sealant: there is no RF visible at the margins of the sealants (see arrows). Right: a compromised sealant where plaque infiltrated the space between sealant and tooth (see regions indicated by the arrows).
Sensitivity and specificity for the detection of carious lesions with QLF or visual. Both methods are used subjectively.
Bacteria involved in RF.
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