Laser fluorescence detection of subgingival calculus using the DIAGNOdent Classic versus periodontal probing

Deposits of subgingival calculus on the root surfaces of the teeth are difficult to detect with conventional methods such as tactile probing. This study compared the performance of a 655-nm wavelength laser fluorescence (LF) system (DIAGNOdent Classic with a periodontal tip) with conventional periodontal probing under defined conditions in a laboratory simulation, using an experienced examiner. Models with a total of 30 extracted teeth with varying levels of subgingival deposits scattered on their root surfaces were prepared, and silicone impression material applied to replicate periodontal soft tissues. The models were located in a phantom head, and the presence of subgingival calculus recorded at 8 points per tooth (240 sites), then the entire scoring process repeated after 1 and 2 weeks. The optimal LF threshold was determined as a fluorescence score of 7 using Receiver Operating Characteristic curves. When compared the gold standard of direct microscopic examination of roots, LF was more sensitive, specific, and accurate than tactile probing (68.3 vs. 51.7 %; 92.1 vs. 67.8; and 80.2 vs. 59.8 %, respectively), and was also more reproducible (Cohen kappa 0.60 vs. 0.39). These data support the concept of using LF as an adjunct to clinical diagnosis.