In Vitro Detection of Caries Around Amalgam Restorations Using Four Different Modalities

Tamara E. Abrams1, Stephen H. Abrams1, 2, *, Koneswaran S. Sivagurunathan1, Josh D. Silvertown1, Warren M.P. Hellen2, Gary I. Elman2, Bennett T. Amaechi3
1 Quantum Dental Technologies Inc, Toronto, Ontario, Canada
2 Cliffcrest Dental Office, Scarborough, Ontario, Canada
3 University of Texas Health Science Center, San Antonio, Texas, USA

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© 2017 Abrams et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the Quantum Dental Technologies Inc, 748 Briar Hill Avenue, Toronto, Ontario M6B I L3; Tel: 416-523-8453; Fax: 416-265-6795; E-mail:



The aim of this study was to evaluate the ability of PTR-LUM (The Canary System, CS), laser fluorescence (DIAGNOdent, DD), LED fluorescence (Spectra), and visual inspection (ICDAS II) to detect natural decay around bonded amalgam restorations in vitro.


Seventeen extracted human molars and premolars, consisting of visually healthy (n=5) and natural cavitated (n=12) teeth were selected. For the carious teeth, caries was removed leaving some decayed tissue on the floor and or wall of the preparation. For sound teeth, 3 mm. deep cavity preparations were made and teeth were restored with bonded-amalgam restorations. Thirty-six sites (13 sound sites; 23 carious sites) were selected. CS and DD scans were performed in triplicate at 2, 1.5, 0.5, and 0 mm away from the margin of the restoration (MOR). Spectra images were captured for the entire surface, and dentists blinded to the samples provided ICDAS II scoring.


Canary Numbers (Mean±SE) for healthy and carious sites at 2, 1.5, 0.5, and 0 mm from the MOR ranged from 12.9±0.9 to 15.4±0.9 and 56.1±4.0 to 56.3±2.0, respectively. DD peak values for healthy and carious sites ranged from 4.7±0.5 to 13.5±2.99, and 16.7±3.7 to 24.5±4.4, respectively. For CS and DD, sensitivity/specificity for sites at 2.0, 1.5, 0.5, 0 mm ranged from 0.95-1.0/0.85-1.0, and 0.45-0.74/0.54-1.0, respectively. For ICDAS II, sensitivity and specificity were 1.0 and 0.17, respectively. For Spectra, data and images were inconclusive due to signal intereference from the amalgam restoration.


Using this in-vitro model, CS and DD were able to differentiate between sound and carious tissue at the MOR, but larger variation, less reliability, and poorer accuracy was observed for DD. Therefore, CS has the potential to detect secondary caries around amalgam restorations more accurately than the other investigated modalities.

Keywords: Laser fluorescence, Canary System (CS), LED fluorescence (Spectra), Visual inspection (ICDAS II), Margin of the restoration (MOR), Amalgam restorations.