Diagnosis of secondary caries: a laboratory study.

Secondary caries is difficult to diagnose accurately. The purpose of this laboratory study was to investigate various non-invasive clinical and radiographic criteria which might predict the presence of carious dentine beneath the margin of the filling. A total of 331 sites, each 3 mm in length on the tooth restoration margin, were selected on 112 extracted and filled teeth. Thirty of these sites showed obvious carious cavities. Ditching was apparent in a further 70 sites, while 231 sites were clinically intact. Staining of the margin of the filling was recorded and radiographs were taken of posterior teeth. Restorations were then removed and the enamel-dentine junction (EDJ) immediately below the sites was examined for its consistency (hard/soft) and colour (stained/stain-free). Results showed that staining around a filling is not a reliable predictor of softening or discolouration of the dentine beneath. A clinical carious cavity and radiographic evidence of demineralisation indicate soft and discoloured dentine and should trigger operative intervention, while ditching alone should not.