Substance removal on teeth with and without calculus using 308 nm XeCl excimer laser radiation. An in vitro investigation.

It was the aim of this in vitro study to determine the potential effects of 308 nm XeCl excimer laser radiation on root surfaces when used for removing calcified deposits. The source of laser radiation was a XeCl-excimer laser (MAX 10, Fa. Medolas, Germany) emitting ultraviolet radiation at a wavelength of 308 nm with a pulse duration of 60 ns. Subjects of irradiation were 60 extracted teeth which were divided into 2 groups of 30 samples each with (group 1) and without calculus (group 2). Specimens were irradiated with 800 laser pulses at 5 different energy-densities per pulse of 1.0 J/cm2, 2.0 J/cm2, 3.0 J/cm2, 4.0 J/cm2 and 5.0 J/cm2. For each parameter 6 samples (n=6) were exposed to 308 nm excimer-laser radiation. The ablation of hard tissue on the treated root surfaces was measured 3-dimensionally with a laser scanning device (100,000 surface points per sample; accuracy: 5 microm) and evaluated with a special image analyzing software (volume, mean, median, standard deviation). In addition, a scanning electron microscopic (SEM) evaluation of the irradiated root surfaces was performed. Statistical analysis was done using ANOVA with the Scheffé-test. The lowest amount of ablation on teeth without calculus was induced with 14.01 (+/-5.86) microm using laser radiation at an energy density of 2.0 J/cm2. Maximum tissue removal in this sample group was obtained with 56.67 (+/-21.05) microm with laser treatment at an energy density of 5.0 J/cm2. While no ablation of dental cementum was detectable after irradiating root surfaces without calculus at 1.0 J/cm2, a strong removal of calculus with a mean value of 31.91 (+/-4.2) microm was observed under these conditions. The results seem to indicate that a selective removal of subgingival calculus creating a homogenous shape of the root surface with 308 nm excimer laser radiation is possible. Furthermore, no signs of the formation of a smear layer nor the induction of thermal side-effects were observed.