Detection of subgingival calculus and dentine caries by laser fluorescence

Objectives: Detection of subgingival calculus and dentine caries in the bottom of deep periodontal pockets is often difficult without visual observation. We thus examined the possibility of its detection using autofluorescence induced by laser irritation. Methods: Autofluorescence was measured at various excitation and emission wavelength settings in five specimens each of sound dentine and enamel, subgingival calculus, and root caries. Periodontopathic model teeth with bacterial cells and blood clots were also irritated by laser to obtain autofluorescent images. Results: Subgingival calculus and dentine caries showed a characteristic 700 nm emission when excited at 635 nm or a 720 nm emission when excited at 655 nm; sound dentine or enamel, however, did not. The calculus differentiation power, however, was higher with excitation at 635 nm than at 655 nm. The autofluorescent images photographed at an excitation of 633 nm provided clear calculus identification in periodontopathic model teeth when a 700 nm band-pass filter or a 700 nm high-pass filter was used. However, fluorescence intensity was masked when the calculus surface was covered by bacterial cells or blood clots. For clinical use, it would be important to remove subgingival plaque and debris from root surfaces before attempting to detect subgingival calculus and root caries with this manner. Conclusion: The autofluorescence method employing excitation of 633-635 nm was found to be a powerful tool for detecting subgingival calculus and root caries.