Clinical tests of the caries treatment with a Er:YAG laser system have been very promising. The problem of the Er:YAG laser drilling machine is the speed of preparation. It is not possible to increase the laser energy and repetition rate because this process is directly connected with temperature elevation. Therefore attention has been paid to define the differences between the classical and the laser drilling effect with a safe but effective laser energy and repetition rate. For the experiment, an Er:YAG laser drilling machine with an articulated arm was designed. Thirty samples of extracted human teeth were cut by both this system and classical drilling machine. The circumference, area and structure of surface sections were observed and analyzed.From the comparison of the measured time of preparation significant differences followed from the time of preparation (155 sec is needed for preparation by laser radiation and 28.4 sec for a classical drilling machine). The time of preparation related to 1 mm2 of the cut surface was 5.42sec for the Er:YAG the laser machine and 0.66 sec for the classical method. From this comparison it follows that the laser system is 8 times slower than the classical preparation technique. In both cases the roughness of the surface analyzed by SCAN was found similar. Also, there were no differences between the distribution of the elements, especially calcium and phosphorus.
The advanced method consists in implantation -labelling of the thin surface layers of the solid objects, e.g. hard tooth tissue, by atoms of suitable natural or artificial radionuclides. Nuclides from the uranium series were implanted into the surface by using nuclear recoil effect at alpha decay of 226Ra to 222Rn, alpha decay of 222Rn to RaA, alpha decay of RaA to RaB (beta -emitter) and further alpha or beta emitters. With regard to chosen alpha detection and to the half -lives of the radionuclides, there was actually measured the activity of 222Rn, RaA and RaC' in the thin surface layer. This was followed by the laboratory simulation of the abrasion in the system of" toothbrush -various suspensions of the tooth-pastes -hard tooth tissue (or material standard -ivory)" in specially designed device -the dentoabrasionmeter. The activities of the tissue surface measured before and after abrasion were used for calculations of the relative drop of the surface activity. On this basis the influence of various tooth-pastes containing various abrasive substances was determined.
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