Objectives: Because subgingival dental calculus in periodontal pockets is associated in the etiopathogenesis of progressive human periodontitis, and is difficult to accurately detect with conventional manual explorers and probing instruments, there is an urgent clinical need for more reliable diagnostic methods for the detection and localization of subgingival dental calculus. A low-power (< 1 milliwatt) diode laser emitting visible red laser fluorescence at a 655 nm wavelength in the near-infrared electromagnetic spectrum (Diagnodent Pen, Kavo Dental Corp., Charlotte, NC USA), and fitted with a periodontal probe-like rigid cylindrical sapphire tip, is approved for clinical patient care by the United States Food and Drug Administration and commercially marketed for subgingival dental calculus detection, but has received relatively little research attention. This study assessed the in vitro reproducibility and accuracy of this visible red laser fluorescence-emitting instrument for dental calculus detection on root surfaces of extracted human teeth.;Methods: A total of 50 extracted single and multi-rooted human teeth (11 incisors, 4 canines, 7 premolars, and 28 molars) with a range of visually-evident dental calculus deposits were initially evaluated with a SZX10 research stereomicroscope (Olympus America, Inc., Center Valley, PA USA) at 10x magnification for the presence of dental calculus on tooth root surfaces, which was recognized by its dark color and raised surface morphology. One dental calculus-positive and one dental calculus-negative root surface was selected per tooth as test surfaces for further evaluation. The presence and nature of dental calculus deposits on each test root surface was scored on a 0-2 scale with a modified Subgingival Calculus Index (SCI) by an experienced, board-certified periodontist using an 11/12 Old Dominion University dental explorer. Two independent dentist examiners with varied educational and clinical experience backgrounds (one a board-certified specialist in periodontics with 35 years of clinical dental care experience, and the other a general dentist in an advanced general dentistry residency program with 6 years of clinical dental care experience), each assessed the test root surfaces with the visible red laser fluorescence-emitting instrument using two different evaluation protocols. In the first evaluation protocol, each examiner perpendicularly directed the visible red laser fluorescence-emitting instrument tip twice along test root surfaces, and recorded the maximum laser fluorescence intensity values obtained from each pass, which potentially ranged from 0-99. In the second evaluation protocol, each examiner assessed test root surfaces twice for maximum laser fluorescence intensity values with the laser instrument tip directed parallel to the tooth root surface and advanced in an apical direction from the tooth cementoenamel junction, similar to how a periodontal probe is introduced in vivo into periodontal pockets. Correlation coefficient analysis evaluated intra- and inter-examiner reproducibility of visible red laser fluorescence intensity values obtained with both evaluation protocols. A two-tailed, independent samples, Student's t- test evaluated mean visible red laser fluorescence intensity values measured between dental calculus-positive and dental calculus-negative root surfaces, and also statistically compared mean visible red laser fluorescence intensity scores recorded on dental calculus-positive tooth root surfaces exhibiting a modified SCI score = 2, as compared to a modified SCI score = 1. Sensitivity, specificity, positive predictive value, negative predictive value, and odds ratio analysis assessed the occurrence of dental calculus- positive and -negative root surfaces associated with two visible red laser fluorescence intensity threshold levels recommended for clinical diagnostic purposes by the manufacturer (≥ 5 and > 40).;Results: A total of 50 root surfaces exhibited a modified SCI score = 0 (no root surface dental calculus detected), whereas 19 root surfaces revealed modified SCI scores = 1 (root surface dental calculus detected in thin deposits, but not in a markedly-raised ledge), and 31 root surfaces had modified SCI scores = 2 (root surface dental calculus detected in a markedly-raised ledge). A high level of both intra- and inter-examiner reproducibility of visible red laser fluorescence intensity readings was found with both tooth root evaluation protocols, despite the marked differences between the two dentist examiners in their educational backgrounds and length of clinical dental care experience, with correlation coefficient values ranging from r = 0.948 to r = 0.999 for duplicate assessments made by the two independent examiners themselves and between them. Mean visible red laser fluorescence intensity values recorded by the two independent examiners with the instrument perpendicularly directed along tooth root surfaces (first evaluation protocol) were 98.9 (standard deviation +/- 0.4) and 99.0 (standard deviation +/- 0.0), respectively, on dental calculus-positive root surfaces, which were significantly greater than mean values of 10.9 (standard deviation +/- 6.0) and 12.3 (standard deviation +/- 8.1), respectively, recorded on dental calculus-negative root surfaces (P < 0.0001 for each examiner; two-tailed, independent samples, Student's t-test). Similarly, mean visible red laser fluorescence intensity values recorded by the two independent examiners with the instrument directed apical and parallel to the tooth root surface (second evaluation protocol) were 76.9 (standard deviation +/- 26.4) and 79.7 (standard deviation +/- 23.8), respectively, on dental calculus-positive root surfaces, which were significantly greater than mean values of 4.2 (standard deviation +/- 2.7) and 4.9 (standard deviation +/- 4.1), respectively, on dental calculus-negative root surfaces ( P < 0.0001 for each examiner; two-tailed, independent samples, Student's t-test). Significantly greater visible red laser fluorescence intensity scores were found on dental calculus-positive root surfaces with modified SCI scores = 2, as compared to modified SCI scores = 1, but only when the visible red laser fluorescence-emitting instrument tip was directed parallel to the tooth root surface and advanced apically like a periodontal probe. A threshold level of ≥ 5 for visible red laser fluorescence intensity readings provided 100% sensitivity, 68% specificity, a 75.8% positive predictive value, a 100% negative predictive value, and an odds ratio relationship of 20.1 [95% confidence interval = 8.8, 45.8] for the presence of dental calculus on tooth root surfaces. In comparison, a threshold level of > 40 for visible red laser fluorescence intensity values offered 90% sensitivity, 100% specificity, a 100% positive predictive value, a 90.9% negative predictive value, and an odds ratio relationship of 36.6 [95% confidence interval = 16.7, 80.2] for the presence of dental calculus on tooth root surfaces.;Conclusions: These in vitro findings document, for the first time, a high level of intra- and inter-examiner reproducibility of visible red laser fluorescence intensity measurements on human tooth root surfaces, regardless of the whether the instrument is directed either perpendicular or parallel to extracted tooth root surfaces. Dental calculus- positive root surfaces on extracted teeth exhibited significantly higher visible red laser fluorescence intensity scores than dental calculus-negative root surfaces, particularly when dental calculus deposits were present in markedly-raised ledges. In addition, a threshold level of > 40 for visible red laser fluorescence intensity readings offered greater diagnostic accuracy than a threshold level of ≥ 5 for identification of dental calculus on root surfaces of extracted teeth. These findings provide further in vitro validation for use of the visible red laser fluorescence-emitting instrument for detection of dental calculus on root surfaces of human teeth. Additional validation studies, conducted clinically in vivo, on the visible red laser fluorescence-emitting instrument are warranted.
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