Fluorescence spectroscopy of dental calculus

Background:  Correct diagnosis of the presence and extent of subgingival calculus is important for periodontal treatment planning and reassessment after periodontal therapy. Traditional tactile methods often lack sensitivity. The present investigation shall contribute to understanding the fundamental fluorescence properties that may be useful for optical detection of both supra‐ and subgingival calculus. Objectives:  The aim of this study was to investigate emission spectra from supra‐ and subgingival calculus under a wide range of excitation wavelengths. Methods and Results:  Extracted human molars with either supragingival or subgingival calculus deposits on the root surface were selected ( n  = 3 each). Emission spectra were recorded from the calculus of each tooth and corresponding areas of clean root surfaces using a fluorescence spectrophotometer at excitation wavelengths from 360 nm up to 580 nm in steps of 20 nm. The spectra were corrected for the wavelength dependent instrument sensitivity and normalized to peak intensity (the highest peak was set at 1.0). Emission spectra of calculus exhibited distinct fluorescence bands between 570 and 730 nm not present in clean root surfaces. This fluorescence emission was strongest for excitation wavelengths from 400 to 420 nm. No differences were observed between supra‐ and subgingival calculus. Conclusions:  Human dental calculus can clearly be differentiated from clean root surfaces by emission spectrophotometry. The characteristic fluorescence emission of supra‐ and subgingival calculus may be due to a variety of porphyrin derivatives and may provide the basis for future diagnostic procedures.