The laser induced autofluorescence from carious regions of human teeth was studied using a krypton ion laser at 407 flirt as excitation source, a fiberoptical detection system combined with a polychromator and an optical muLtichannel analyzer. In addition, time.resolved and time-gated fluorescence measurements in the nanosecond range were carried out. It was found that carious regions contain different fluorophores which emit in the red spectral range. The emission spectra with maxima around 590 nm, 625 nm and 635 nm are typical for metalloporphyrins, copro-and protoporphyrin. During excitation the fluorescence was bleached. Non-carious regions showed a broad fluorescence band with a maximum in the short-wavelength spectral region with shorter fluorescence decay times than the carious regions. Therefore, caries can be detected by spectral analysis of the autofluorescence as well as by determination of the fluorescence decay times or by time-gated imaging.

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Laser induced shockwave lithotripsy (LISL) on artificially inserted human renal calculi was realized in explanted pig ureters. A pulse stretched Alexandrite solid state laser was used at 750nm. Pulses of 350ns and 1 microseconds duration were transmitted through a 250 microns all silica fiber onto a stone surface, keeping the fiber tip in contact with a stone close to the ureter wall. The high power density of the 350 ns pulses lead to an optical breakdown inside the distal fiber tip causing fiber fragmentation of about 28 mm/100 pulses. Deep penetration of the fiber fragments into the ureter wall was proven histologically. Fiber fragmentation was avoided by increasing the pulse duration up to 1 microseconds. Riks for patient treatment caused by short pulse lithotripsy are discussed.

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