Quantitative Light-Induced Fluorescence objective scoring system for plaque and calculus in dental trials in dogs

Quantitative Light-induced Fluorescence – Extent & Density (QLF-ED) is a dental plaque and calculus objective scoring system designed to be used in VOHC® Seal of Acceptance trials.
Images are taken with a custom-made digital auto-focus camera equipped with both blue light and white light rings (QRayCam Pro). The images are then fed into a proprietary QLF software program (C4 – Inspektor Research Systems, NL) for analysis. Teeth to be scored are digitally contoured, then each 10x10 pixel square on the buccal crown surface of targeted teeth is analyzed for presence of and density of red fluorescence in the blue light image. The result is reported as the percentage of the crown covered by variable thickness plaque or calculus relative to maximum full-crown coverage.
To validate the use of QLF-ED, trials have been run where typical subjective scoring systems (e.g. Modified Logan -Boyce [ML-B] plaque score or Warrick-Gorrel [W-G] calculus score) and QLF images were both scored. The first data were from a dose-response trial; the correlation coefficient ‘r’ values comparing the disclosed subjective and disclosed QLF plaque and calculus scores indicated moderate or strong correlation; these data were based on dogs 21 days after scaling, which is shorter than the minimum required 28 days in VOHC® trials. Recently, additional data were obtained from dogs 30 days following scaling. Some of the teeth were completely covered by plaque, which results in QLF reporting a zero score, rather than 100%. In a previous report of scoring extent of disclosed plaque in dogs by QLF, this zero/100% problem was addressed by exporting the image to PhotoShop to add a white reference spot, then importing the image back into C4. As a result of recent C4 QLF-ED programming work, a one-mouse click reference spot system corrects the zero reports for fully plaque-covered teeth.
QLF-ED is expected to provide a more accurate assessment of plaque and calculus than subjective scores or the simple extent-only plaque QLF score previously described (Wallis et al, 2016), because it combines extent of coverage with fluorescence density (indicative of thickness) on multiple individual sites. The ML-B and W-G scores rely on subjective human eye assessment of coverage on a 0-4 scale and of thickness on a 1-3 scale, with the thickest area being recorded for that tooth.
VOHC® trial requirements include scoring of teeth stained by disclosing solution - scoring undisclosed calculus requires brushing or rubbing away superficial plaque, which would prevent scoring disclosed calculus.
The effect of application of disclosing solution on QLF scores has yet to be fully explored. Does it artificially distort the fluorescence score by augmentation or by creating ‘noise’? If so, scoring undisclosed teeth by QLF would be indicated. To date, while some teeth have been QLF scored for plaque before the disclosing solution is applied, no QLF data have been obtained on undisclosed calculus. Undisclosed plaque in some dogs has been scored, and results will be discussed.