produce the red fluorescence, with white light correlated images for comparative visual assessment) can be obtained using the QrayCam Pro camera, which provides automatic focusing on the teeth of interest and records the dog identification data in the image file name.

‘QLF-ED’ is used to reflect that it is density of QLF, not the physical thickness, that is reported in the QLF-ED score, as measuring the actual physical thickness of plaque to permit analysis of the correlation between density of fluorescence and physical thickness has proved to be impractical. We have reported the correlation of actual thickness of calculus with QLF density of calculus, though measuring the typically limited thickness of calculus seen in dogs four weeks following scaling has also proved impractical. While a linear relationship between QLF density and calculus or plaque height at a particular location would be ideal, factors other than the volatile sulfur compounds (VSC) produced by gram-negative periodontopathogens that fluoresce - heme within bacteria or in gingival fluid resulting from inflammatory breakdown of red blood cells also fluoresces. The relationship between plaque and calculus height and QLF density thus may not be linear; however, we recognize that the addition of non-VSC-induced fluorescence that is primarily located at the gingival margin actually provides a more critical clinical indicator.

The computer programming to produce an analysis of the combination of extent and density of coverage by dental plaque (on unbrushed teeth) and calculus (on brushed teeth) has been completed by Dr. Elbert Waller (Inspektor Research, BV, Amsterdam). The analysis is reported for individual teeth as a percentage of the combined potential maximum coverage by the potential maximum fluorescence density on that tooth. The density of fluorescence is determined for each group of 10x10 pixels on the tooth surface, recorded as being in one of four bands. The lowest band (<30% of the maximum fluorescence) is considered to be clinically insignificant ‘pre-plaque’ and is assigned a pixel group score of 0.

To validate the QLF-ED index, QLF-ED scores are now being obtained from dogs several weeks following tooth scaling for comparison with the visual (subjective) plaque and calculus indices used by Summit Ridge Farms in trials typically submitted to the Veterinary Oral Health Council. The VOHC tooth set (maxillary I3, C, P3, P4, M1 and mandibular C, P3,P4, M1) on both sides of the mouth is used. A sufficient number of dogs will be scored to permit subsequent correlation coefficient analysis of sub-groups of teeth (bilateral vs. unilateral, complete VOHC set vs. sub-sets).

This comparative date will be reported. This work is supported by a grant from the American Veterinary Dental College.