IN VITRO EVALUATION OF A DIFFERENTIAL REFLECTOMETRY DENTAL CALCULUS DETECTION INSTRUMENT

Abstract

Objectives: The presence of subgingival dental calculus on tooth root surfaces, an important risk factor in the pathogenesis of human periodontitis, is clinically challenging to reliably detect with existing tactile-based, manual forms of dental instrumentation. In 2003, the United States Food and Drug Administration granted approval for marketing in the United States of a differential reflectometry-based device (DetecTar, NEKS Technologies, Laval, Quebec, Canada) for detection of subgingival dental calculus in humans. The instrument employs a light-emitting diode to deliver red light from the visible light region of the electromagnetic spectrum, with a 635 nm-specific wavelength, onto tooth root surfaces through an optical fiber extending to the tip of a periodontal probe-like handpiece. The optical fiber also collects light reflected back from oral surfaces, from which the optical signature of dental calculus is identified by matching the spectra of the reflected light to an internal computer software database containing red light spectra characteristic of dental calculus in its reference library. To date, only a limited amount of in vitro and in vivo research has been conducted on the DetecTar differential reflectometry device. As a result, the purpose of this study was to to assess, with an in vitro typodont model system, the ability of the DetecTar differential reflectometry device to reliably identify subgingival dental calculus on tooth root surfaces. Methods: A total of 108 subgingival sites on mandibular posterior plastic teeth, of which 73 (67.6%) exhibited artificial dental calculus deposits, were mounted within typodont models of the human oral cavity, comprised of white plastic teeth emerging from and surrounded by anatomically-accurate pink silicone gingival and palatal soft tissues. Each typodont was attached to a phantom head with simulated soft tissue mouth shrouds. Sheep blood was irrigated into subgingival and interproximal areas around typodont teeth to simulate gingival tissue inflammation, and artificial saliva applied onto supragingival typodont tooth surfaces to further simulate typical oral cavity conditions in humans. The 108 test subgingival surfaces were then evaluated with the DetecTar differential reflectometry device in duplicate readings performed by a single periodontist examiner blinded to the typodont distribution of subgingival dental calculus. Emission of a sustained audible signal tone from the DetecTar differential reflectometry device upon entry of its optical fiber tip into typodont periodontal pockets indicated detection of subgingival dental calculus. The diagnostic performance of the DetecTar differential reflectometry device, relative to in vitro detection of subgingival dental calculus, was assessed among all test root surfaces, as well as among proximal and non-proximal root surfaces, with calculations of sensitivity, specificity, positive predictive value, negative predictive value, positive likelihood value, negative likelihood value, diagnostic odds ratio, accuracy (diagnostic effectiveness), and Youden’s Index. Results: Among all root surfaces, the DetecTar differential reflectometry device revealed a sensitivity of 75.4%, specificity of 86.3%, positive predictive value of 86.0%, negative predictive value of 75.9%, positive likelihood value of 5.5, negative likelihood value of 0.3, diagnostic odds ratio of 19.6, accuracy (diagnostic effectiveness) of 80.6%, and Youden’s index value of 0.62, for in vitro detection of subgingival dental calculus. More favorable diagnostic test findings for the device were found on non-proximal (buccal and lingual) than proximal (mesial and distal) root surfaces, with accuracy (diagnostic effectiveness) values 22.7% lower at proximal sites, indicating a poorer performance capability of differential reflectometry within interproximal periodontal pockets. Only a fair level (kappa = 0.42) of reproducibility was found in duplicate scoring of tooth root surfaces for subgingival dental calculus by the DetecTar differential reflectometry device. Conclusions: These study findings suggest marked limitations in the potential clinical utility of the DetecTar differential reflectometry device for detection of subgingival dental calculus. The device demonstrated markedly decreased in vitro accuracy on mesial and distal typodont tooth root surfaces, as compared to non-proximal tooth sites, and exhibited only a fair level of reproducibility in duplicate assessments. The overall performance of the DetecTar differential reflectometry device appears to be inferior to similar assessments of typodont tooth root surfaces conducted by other investigators with more conventional tactile-based, manual instrumentation. Based on these in vitro findings, routine clinical utilization of the DetecTar differential reflectometry device in dental practice is not recommended.