M Beerens

30 CHAPTER 2 After 2 months, photograph galleries were recorded by M.H.V. to allow side- by-side comparison. Photograph galleries were analysed again in random order for subject, but with T1 and T2 photographs side-by-side to score visual transition (VT), i.e. lesions worsening, remaining the same or improving (Table 1). Quantitative light-induced fluorescence imaging QLF images were captured using an intra-oral fluorescence camera (QLF/Clin; Inspektor Research Systems, Amsterdam, the Netherlands) and dedicated software (Inspektor pro version 3.0.0.42; Inspektor Research Systems) with video repositioning technique (Beerens et al. , 2010). Photographs captured at different time points showed the tooth surface from the same angle and with the same size, except for changes due to e.g. differences in gingival swelling. Plaque removal in the clinic was performed prior to QLF photography. QLF images were judged visually for signs of decalcification, which appear as dark areas surrounded by bright green fluorescing sound tooth tissue (de Josselin de Jong et al. , 1995). For all lesions detected, the integrated fluorescence loss (IFL [%.mm 2 ]) over the lesion area was determined at a 5% threshold (Al-Khateeb et al. , 1998) by a single examiner (M.W.B.), who was trained and calibrated by an experienced QLF examiner (M.H.V.) on a dataset of 500 QLF images. The integrated fluorescence loss (IFL [%.mm 2 ]) over the lesion area was assessed on all surfaces where a lesion was seen on the QLF photographs. In a first step, images of surfaces in QLF photographs at T1 and T2 were aligned to adjust small repositioning errors. Then a user-defined contour was created on the QLF photograph surrounding the lesion such that the contour borders were located on healthy tooth enamel as much as possible. Contour borders not on healthy tooth tissue were excluded. The same contour was applied by an automated software algorithm to longitudinal images of the same surface (Inspektor pro version 3.0.0.42; Inspektor Research Systems). In subjects where lesion visibility at T1 was hampered as a result of swollen gingiva, the visible area of the lesion at baseline was the part of the lesion analysed at both time points. The IFL per surface was translated into QLF severity score as described in Table 1 for comparison with ICDAS and VT scores on clinical oral photographs.