An ultrathin scanning fiber endoscope, originally developed for cancer diagnosis, was used in a case study to locate plaque and caries. The imaging system incorporated software mitigation of background auto-fluorescence (AF). In conventional fluorescence imaging, varying AF across a tooth surface can mask low-level porphyrin signals. Laser-induced auto-fluorescence signals of dental tissue excited using a 405-nm laser typically produce fluorescence over a wavelength range extending from 440-nm to 750-nm. Anaerobic bacterial metabolism produces various porphyrin species (eg. protoporphyrin IX) that are located in carious enamel, dentin, gingivitis sites, and plaque. In our case study, these porphyrin deposits remained as long as one day after prophylaxis. Imaging the tooth surface using 405-nm excitation and subtracting the natural AF enhances the image contrast of low-level porphyrin deposits, which would otherwise be masked by the high background AF. In a case study, healthy tissues as well as sites of early and advanced caries formations were scanned for visual and quantitative signs of red fluorescence associated with porphyrin species using a background mitigation algorithm. Initial findings show increasing amplitudes of red fluorescence as caries severity increases from early to late stages. Sites of plaque accumulation also displayed red fluorescence similar to that found in carious dental tissue. The use of real-time background mitigation of natural dental AF can enhance the detection of low porphyrin concentrations that are indicators of early stage caries formation.
The current rise in childhood caries worldwide has increased the demand for portable technologies that can quickly and
accurately detect and diagnose early stage carious lesions. These lesions, if identified at an early stage, can be reversed
with remineralization treatments, education, and improvements in home care. A multi-modal optical prototype for
detecting and diagnosing occlusal caries demineralization in vivo has been developed and pilot tested. The device uses a
405-nm laser as a scanned illumination source to obtain high resolution and high surface contrast reflectance images,
which allows the user to quickly image and screen for any signs of demineralized enamel. When a suspicious region is
located, the device can be switched to perform dual laser fluorescence spectroscopy using 405-nm and 532-nm laser
excitations. These spectra are used to compute an auto-fluorescence (AF) ratio of the suspicious region and the percent
difference of AF ratios from a healthy region of the same tooth. The device was tested on 7 children’s teeth in vivo with
clinically diagnosed carious lesions. Lesion depth was then visually estimated from the video image using the 405-nm
scanned light source, and within a month the maximum drill depth was assessed by a clinician. The researcher and
clinicians were masked from previous measurements in a blinded study protocol. Preliminary results show that the
ratiometric percent difference measurement of the AF spectrum of the tooth correlates with the severity of the
demineralization as assessed by the clinician after drilling.