Quantitative Light-induced Fluorescence (QLF™)

This caries detection system takes advantage of tooth fluorescence to record images that can be analyzed to obtain data on: lesion Area (Area in mm2, lesion depth expressed in percentile fluorescence loss (deltaF in %), and lesion volume (deltaQ in mm2%) and bacterial activity in terms of percentile increase of red fluorescence (deltaR).

The Inspektor™ Pro QLF camera system:
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The Inspektor™ QLF-D Biluminator™ 2+ camera system:
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Both of these devices use blue light to illuminate the tooth. This causes the teeth to fluoresce in green (so-called auto-fluorescence). The resulting QLF images show a higher contrast between sound and demineralized tooth tissue as seen in the figures of the extracted premolar.
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Extracted premolar with white spot as seen with white light.
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The same premolar seen with QLF.

Besides the green auto-fluorescence, the blue light can also generate red fluorescence that can be seen in the picture below. This red fluorescence is believed to be caused by porphyrins that are the result of the metabolic process of specific bacterial strains. The intensity of the red fluorescence has been shown to be related to the activity of those bacteria. In addition to caries related bacteria, some of the most recent studies using QLF have suggested the red fluorescence may also be related to other oral care issues, such as gingivitis and halitosis.

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Clinical QLF showing green auto-fluorescence on the buccal surfaces and red fluorescence at the proximal areas.

A powerful feature of QLF is the ability to follow tooth surfaces over time (longitudinal monitoring). The software includes automatic video repositioning that enables the acquisition of comparable QLF images of the same surfaces at different time points.

The software can also analyze recorded images and, thus, provide an objective assessment of areas of concern over time.

The photos shown below are research images showing remineralization of a white-spot lesion over a 9 month time period.

Remineralization of a white spot after debracketing:
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Images and data courtesy of S. Al-Khateeb, Karolinska Institutet, Stockholm, Sweden

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Inspektor Research System
Image source: Inspektor Research Systems BV, Amsterdam, The Netherlands

Another study (above) demonstrated that with no treatment, lesions present at the start of the study continued to progress; once fluoride dentifrice was incorporated into the test regimen, reversal of the lesions became quickly apparent.