Imaging suggests that the working mechanism of an Er,Cr:YSGG laser in root canal treatment in an irrigation solution can be attributed to cavitation effects inducing high-speed fluid motion into and out the canal.

Under the conditions of this study LAI is statistically significantly more effective in removing artificially placed dentin debris in a root canal as PUI and CI.

No abstract

Microsecond pulsed laser systems, like the Thulium, Holmium and Erbium laser are being used for a broad range of medical applications in a liquid environment. Usually, the tissue ablation mechanism of these lasers is based on the instant formation of water vapor. When used with fiber delivery systems, the refraction of the beam coming out of the fiber will change the moment the liquid boundary turns to vapor. This dynamic change can be used in a controlled way but can also have adverse effects if not appreciated. In this study, the effect of the vapor phase change was investigated for various fiber shapes regarding optical and mechanical properties using high speed imaging and ray-trace simulation.

Laser systems of various wavelengths and pulse characteristics have been introduced in dentistry. At present, the range of applications for the different systems is being investigated mainly differentiating between soft and hard tissue applications. For the preparation of root canals both hard and soft tissues are involved. Ideally, one would like to use one laser system for the whole treatment. In this study, we studied the characteristics of the pulsed 2,78 Er,Cr:YSGG laser (Biolase, Waterlase Millenium), in view of root canal cleaning and desinfection. The laser energy was fiber delivered with fiber tip diameters from 400 µm down to 200 µm. Special thermal and high speed imaging techniques were applied in a transparent model of a tapered root canal and slices cut from human teeth. High speed imaging revealed the dynamics of an explosive vapor bubble at the tip of the Er laser in water and the root canal model. Typically for Erbium lasers, within a time span of several hundred µs, a longitudinal bubble expanded to maximum size of 5 mm length and 2 mm diameter at 100 mJ and imploded afterwards. In the root canal, the explosive bubble created turbulent high speed water streaming which resects soft tissue from the hard tissue. Thermal imaging showed the dynamics of all lasers heating of the canal wall up to several mm depending on the wavelength and energy settings. The mechanism of smear layer removal and sterilization in the root canal, is attributed to cavitation effects induced by the pulsed laser. The heat generation into the dentine wall was minimal.