Comparison of fluorescence parameters between three generations of QLF devices for detecting enamel caries in vitro and on smooth surfaces

Seok Woo Park, Sang Kyeom Kim, Hyung Suk Lee, Eun Song Lee, Elbert de Josselin de Jong, Baek Il Kim

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21 Citations (Scopus)


Background: This study compared two fluorescence parameters (fluorescence loss [ΔF] and red fluorescence gain [ΔR]) among three generations of quantitative light-induced fluorescence (QLF) systems with the aim of determining the validities of these parameters in the three devices for differentiating the severity of enamel caries. Methods: Forty-one extracted human premolars and molars with suspected enamel caries were selected. Fluorescence images of all teeth were obtained using first-, second-, and third-generation QLF systems (Inspektor Pro, QLF-D, and Qraycam, respectively). Fluorescence parameters were then calculated using proprietary software. All of the specimens were also categorized histologically using polarized-light microscopy (PLM) based on histological levels related to the lesion depth into sound enamel (S), caries limited to the outer half of the enamel (E 1 ), and caries involving the inner half of the enamel (E 2 ). The Mann-Whitney test with Bonferroni correction was used to compare fluorescence parameters among the three generations of systems. The sensitivity, specificity, and area under the receiver operating characteristics curve (AUC) at two thresholds (S/E 1 for detecting enamel caries lesions and E 1 /E 2 for differentiating the caries severity) were calculated for evaluating the validities of the fluorescence parameters obtained using all three generations of QLF devices. Results: ΔF did not differ significantly between the devices at any histological level. In addition, ΔF showed large AUCs at the thresholds of S/E 1 and E 1 /E 2 (0.97–0.98 and 0.89–0.90, respectively). On the other hand, ΔR was significantly higher for the third-generation device than for the first- and second-generation devices for E 2 lesions (P < 0.001). At the S/E 1 threshold, ΔR values of the first- and third-generation devices showed larger AUCs (0.96–0.97) compared with that of the second-generation device (0.91), whereas at the E 1 /E 2 threshold the AUC was the largest for the third-generation device (0.87). Conclusions: The ΔF fluorescence parameter did not differ between the three generations of QLF devices, and showed high validity values. In terms of ΔR, the devices of all generations also showed good diagnostic performance for quantifying and detecting enamel caries lesions, but the third-generation QLF system produced superior results.

Original languageEnglish
Pages (from-to)142-147
Number of pages6
JournalPhotodiagnosis and Photodynamic Therapy
Publication statusPublished - 2019 Mar

Bibliographical note

Funding Information:
This study was supported by Korea Institute of Planning and Evaluation for Technology in Food, Agriculture, Forestry and Fisheries (IPET) through High Value-added Food Technology Development Program, funded by Ministry of Agriculture, Food and Rural Affairs (MAFRA) ( 316071031HDD020 ).

Funding Information:
Inspektor Research Systems BV provided the salary for author EdJdJ, but did not have any additional role in the study design, data collection, analysis, decision to publish, or preparation of the manuscript. EdJdJ’s involvement in this research was under the auspices of his status as adjunct professor at Yonsei University College of Dentistry supported by BK21 PLUS Project. The specific role of EdJdJ was to provide his expertise regarding the fluorescence technology. This does not alter the author’s adherence to the policies of Photodiagnosis and Photodynamic Therapy on sharing data and materials. EdJdJ holds several patents with respect to QLF technology. The remaining authors declared no conflicts of interest.

Publisher Copyright:
© 2018 Elsevier B.V.

All Science Journal Classification (ASJC) codes

  • Biophysics
  • Oncology
  • Dermatology
  • Pharmacology (medical)


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