Comparison of Diode Lasers in Soft Tissue Surgery using CW and Superpulsed Mode: An in vivo Study

Abstract

In 1995, on the IDS, the first diode laser for dentistry was shown. It was an 810 nm diode laser with CW mode.133 Peak power was 6 W. In 2000, a short pulsed diode laser with 810 nm, 20 W, 50 μs pulse and an average power of 2, 0-6, 7 W was introduced which showed a faster cutting and only 50% of the necrosis zone of an CW mode diode laser.154 In 2002, the peak power reached 30 W with a pulse duration of 9 μs, a frequency of 20000 Hz and a limited average power of 10 W. Today frequencies up to 30000 Hz and peak powers of 50 W are possible. To gain a sufficient result, the peak power has to be more than 8 W in this case.141 During the first-year of diode laser treatment in dentistry, only CW mode was possible. Several studies at that time showed that CW mode and 1 W was enough to reach a bactericidal effect on and in roots and root canals so as on implant surfaces.13-16,51,88,106,118,120,154 Application of 3 to 4 W in CW mode led very fast to carbonization of the soft tissue; the carbonization caused higher absorption followed by a heavy thermal damage and necrosis of the tissue.71,148,149,154 To approach better results in soft tissue treatment without much carbonization, it was necessary to interrupt the CW mode. That was done by chopping the CW mode. Pulses down to several 100 μs were realized.141,97,145 The peak power of the pulses was in fact not higher than the peak power of the CW mode pulse, but the applied dose was decreased and the carbonization and thermal damage were reduced. A further progress were pulse durations of 9 μs, a frequency of 20000 Hz and a peak power of 50 W, which could only be generated by DPL (digital pulse technique). Using these parameters could generate a fast, sharply edged cut nearly without thermal damage of the surrounding tissue and only minimal carbonization at the cutting edges. Several studies in the recently past years have shown that short pulses with high peak powers could generate a much better result than lower powers with longer pulse duration.17,24,26,34,35,109,151,152 Therefore, it is a major task of this study to answer the question if highly pulsed diode lasers are more suitable for soft tissue surgery than CW mode diode lasers and how the achievable results differ.