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    How to detect caries around amalgam restorations

    The Canary System helps solves a common clinical challenge by detecting caries around the margins of amalgam restorations.

    Detecting caries around amalgam restorations is a major clinical challenge. Typically, older amalgam restorations may cause some marginal staining, but visually the margins may appear intact and sound.

    The detection of secondary caries in its early stages is not easy. Using detection methods such as radiography, explorer, fluorescence caries detection aids and visual examination may not provide any relevant information. Discoloration next to the restoration or ditched amalgam margins is not necessarily predictive of secondary caries.

    Fig. 1Fig. 1In this clinical situation, the patient had been complaining of pain on the maxillary left side. Visually, the restorations appeared worn but the margins were intact (Fig. 1). A bitewing radiography did not reveal any radiolucency around the restorations on the teeth (Fig. 2). 

    Bitewing radiographs may not be the ideal for detecting enamel secondary caries,3, 4, 5 particularly if they are located on the occlusal or smooth surfaces. The restoration also masks the ability of radiographs to detect caries along the preparation walls.6 All of these factors create difficulties in determining the source of pain.

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    We were faced with a challenge. Do we watch and wait for further symptoms to develop? Do we remove the restoration to see if we can detect caries? Are there other caries-detection devices that can detect caries around the amalgam margins? 

    There are a number of caries detection devices on the market today, but they have limitations. The fluorescence-based devices such as SPECTRA, DIAGNODent and SOPRO are not detecting caries, but other components that glow or fluoresce at a particular wavelength. The literature indicates that: bacterial porphyrins (bacterial breakdown products), stain, tartar  and food debris all fluoresce under the wavelengths used in these devices, whether or not caries is present.7 8 9      

    Fig 2.Fig. 2A number of studies have concluded that measuring fluorescence is not suitable for detecting caries around restoration margins or beneath dental sealants due to false positive readings.10, 11, 12, 13 The CR Clinicians’ Report (March 2012) found that existing restorations interfered with readings.14  Fluorescence does not give any information about lesion size or depth, and does not penetrate beneath the tooth surface due to the scattering of light from stain, plaque, organic deposits and surface features such as pits and fissures.15, 16



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    Stephen Abrams
    Stephen Abrams is a general dental practitioner with over 36 years of clinical experience. Upon graduation from the University of ...


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