Fluorescence-aided root canal treatment: Optimizing imaging conditions with the ZEISS EXTARO 300

Prof. Kazuo Kitamura builds on his earlier clinical work on fluorescence-aided root canal treatment (FARCT). In this study, he measures how microscope settings affect the visibility of protoporphyrin IX (PpIX) red fluorescence, a marker of bacterial contamination. In 15 molars, fluorescence images of the canal orifices were taken with the ZEISS EXTARO 300 while magnification, illumination intensity and working distance were changed one at a time. Fluorescence stayed strong at magnification factors of 0.4-1.0, dropped at 1.6 and fell sharply at 2.5. It rose steadily with illumination intensity, peaking at 100%, and fell as working distance increased, with the highest values at 200 mm. Red and green signals changed in parallel, so these settings affect the brightness of the whole image, not just the bacterial signal. The author recommends a magnification factor of about 1.0 and full illumination for routine FARCT. During instrumentation, a working distance of about 250 mm is a practical compromise. For observation-only steps, such as checking for residual fluorescence before root canal filling, 200 mm gives the best visibility. Standardizing these settings may make FARCT more reproducible.

^{Original Title & Source: Keisuke Saigusa, Tatsuya Hasegawa, Katofumi Koyanagi, Masayuki Sadamura, Kazuo Kitamura. Effects of imaging conditions on fluorescence intensity during fluorescence-aided root canal treatment, Photodiagnosis and Photodynamic Therapy, Volume 62, December 2026}