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 removin g calcified deposits. The source of laser radiation was a XeCl-excimer lase r (MAX 10, Fa. Medolas, Germany) emitting ultraviolet radiation at a wavele ngth of 308 nm with a pulse duration of 60 ns, Subjects of irradiation were 60 extracted teeth which were devided into 2 groups of 30 samples each wit h (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/cm(2), 2.0 J/cm(2), 3.0 J/cm(2) 4.0 J/cm(2) and 5.0 J/cm(2). For each parameter 6 samples (n=6) were exposed to 308 em excimer-laser radiation. The ablation of hard tissue on the treated root surfaces was measured 3-dimensionally wi th a laser scanning device (100,000 surface points per sample; accuracy: 5 pm) and evaluated with a special image analyzing software (volume, mean, me dian, standard. deviation). In addition, a scanning electron microscopic (S EM) evaluation of the irradiated root surfaces was performed. Statistical a nalysis was done using ANOVA with the Scheffe-test. The lowest amount of ab lation on teeth without calculus was induced with 14.01 (+/-5.86) mu m usin g laser radiation at an energy density of 2.0 J/cm(2). Maximum tissue remov al in this sample group was obtained with 56.67 (+/-21.05) mu m with laser treatment at an energy density of 5.0 J/cm(2). While no ablation of dental cementum was detectable after irradiating root surfaces without calculus at 1.0 J/cm(2), a strong removal of calculus with a mean value of 31.91 (+/-4 .2) mu m was observed under these conditions. The results seem to indicate that a selective removal of subgingival calculus creating a homogenous shap e of the root surface with 308 nn excimer laser radiation is possible. Furt hermore, no signs of the formation of a smear layer nor the induction of th ermal side-effects were observed.