The aim of this study was to correlate lesion depth of natural caries, measured with Polarized Light Microscopy (PLM), to Canary Numbers (CN) derived from The Canary System™ (CS), numerical readings from DIAGNOdent (DD), and lesion scores from ICDAS II.


A total of 20 examination sites on extracted human molars and premolars were selected. The selected examination sites consisted of healthy and enamel caries on smooth and occlusal surfaces of each tooth. Two blinded dentists ranked each examination site using ICDAS II and the consensus score for each examined site was recorded. The same examination sites were scanned with CS and DD, and the CN and DD readings were recorded. After all the measurements were completed, the readings of the three caries detection methods were validated with a histological method, Polarized Light Microscopy (PLM). PLM performed by blinded examiners was used as the ‘gold standard’ to confirm the presence or absence of a caries lesion within each examined site and to determine caries lesion depth.


Pearson’s coefficients of correlation with caries lesion depth of CNs, DD readings and ICDAS scores were 0.84, 0.21 and 0.77, respectively. Mean ± SD CN for sound sites (n=3), caries lesion depths <800 µm (n=11), and caries lesion depths >800 µm (n=6) were 11±1, 55±15, and 75±22, respectively. Mean ± SD DD readings for sound sites, caries lesion depths <800 µm, and caries lesion depths >800 µm were 1±1, 7±11, and 8±9, respectively. Mean ± SD ICDAS II scores for sound sites, caries lesion depths <800 µm, and caries lesion depths >800 µm were 0±0, 2±1, and 2±1, respectively. The intra-operator repeatability for the Canary System was .953 (0.913, 0.978).


This study demonstrated that the CS exhibits much higher correlation with caries lesion depth compared to ICDAS II and DD. CS may provide the clinician with more information about the size and position of the lesion which might help in monitoring or treating the lesion.

The present extracted tooth study found that The Canary System correlates with caries lesion depth more accurately that ICDAS II and DIAGNOdent.

Keywords: Polarized Light Microscopy (PLM), Canary Numbers (CN), Canary System™ (CS), DIAGNOdent (DD), ICDAS II, Pearson correlation coefficient (PCC).
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