Subgingival calculus detection with fluorescence induced by 655 nm InGaAsP diode laser radiation

Background: It has been suggested that the 655 nm InGaAsP diode laser radiation can induce considerably higher amounts of fluorescence in subgingival calculus than in cementum. This in vitro study evaluated the use of fluorescence induced by the diode laser radiation for the detection of subgingival calculus. Methods: The study sample consisted of 30 extracted molars, premolars, canines, and incisors. The root surface of each sample was partially covered with subgingival calculus. The source of laser radiation was an InGaAsP diode laser emitting visible radiation at a wavelength of 655 nm. The fluorescent radiation reflected from the cementum and calculus was detected by a photoelectric cell integrated within the diagnostic system. The samples were randomly assigned to 3 experimental groups of 10 teeth each for detection of calculus in various media. Specifically, the fluorescence was determined in air (group A), in electrolytic salt solution (group B), and in blood (group C). For each sample, the intensity of the fluorescent light was evaluated separately for cementum and calculus in triplicate measurements. The statistical analysis was performed using a t test at a level of significance of 5% (P <0.05). Results: The intensities of fluorescence radiation emitted by cementum were 0.4 (+/-0.51) in air, 0.4 (+/-0.51) in electrolytic solution, and 2.13 (+/-0.59) in blood. For calculus, the relative intensities of fluorescence radiation were 54.1 (+/-29.09) in air, 60.77 (+/-28.35) in electrolytic salt solution, and 39.63 (+/-29.79) in blood. The differences in fluorescence between cementum and calculus within each experimental unit were significant (group A: P = 0.0002, group B: P = 0.0001, group C: P = 0.031). The intensity of fluorescence in calculus was also significantly different between the 3 experimental groups. Conclusion: The present study indicates that subgingival calculus can be reliably detected on extracted teeth using laser fluorescence induced by the 655 nm diode-laser radiation. In vivo studies are necessary to evaluate the clinical utility of this procedure.