Detection of subgingival calculus with a novel LED-based optical probe

Background: A recently introduced detection device is designed for objective subgingival calculus diagnosis. The aim of the present study was to assess the possibility of detecting subgingival calculus with this novel LED-based optical probe in vitro. Methods: Twenty extracted human teeth with calculus on the root surface were fixed on a translation stage. Measurements on the root surface were carried out in increments of 0.25 mm with an angulation of 0 to 10 degrees 45 degrees, or 90 degrees to the optical fiber. Teeth were covered either with sodium chloride (NaCl) or blood in order to determine the influence of ambient fluids. Successional areas of positive measurements were defined as "length of positive values" (LPV). The results were compared to the clinical and histological findings. Results: Clinically and histologically apparent calculus on the root surface was accompanied by positive measurement values. A reduction of the angulation between probe and root surface resulted in shorter LPV when measurements were performed in blood (P < 0.05) and longer LPV employing NaCl as the ambient fluid (P < 0.05). For both blood and NaCl, sensitivity and/or specificity values decreased when using lower angulations. Conclusion: The optical probe offers the possibility of subgingival calculus detection and may, therefore, be suited to determine the endpoint of root surface instrumentation during non-surgical periodontal therapy.