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ePaper created 2017-01-04, 09:21:41 | version 1.38.0
| industry 24 laser 4 2016 on hard tissues—both on enamel and dentin, it is recommended to work at energies and pulse dura- tions that are significantly above the threshold value of ablation.11 Moreover, efficiency and the safety level of work with the Er:YAG laser can be in- creased by spraying the water spray on the target tooth surface.12 This also improves the efficiency of the cavities preparation. The radiation penetrates into the water molecules, causing the molecules vi- brations to increase and therefore raising the pres- sureandtemperatureintheareaofapplication,thus initiating the ablation process. Note, however, that athicklayerofwatercancausetheoppositeeffect— isolation of the laser beam from the tissue. Preparation of tissue without water can lead to raising their temperature, causing surface carbon- ization, resulting in a color change to soft bronze.11 Properly prepared tissue has a microporous struc- ture. A macroscopic view of cavity prepared with theuseofdrillshowsitssmoothwalls,comparedto the image of the ablation with Er:YAG laser, where the edges and walls of the cavity are of irregular shape.13 After laser preparation, we get the charac- teristic view of craters with smooth walls with no carbonisedareas,pre-meltedenamelanddentin,or the smear layer. Surface of the enamel obtains mi- cro retention structure, enamel prisms are clearly recognizable, dentine tubules are open and free fromthesmearlayer,allowingthebondingmaterial to penetrate deeply and enhancing the adhesion of the composite material to the cavity walls.14–16 Er:YAG laser operating speed depends not only on thelaserbeamparametersandtheoperator'sskills, Figs. 4 & 5: Caries on tooth 47. Figs. 6–8: Cavity of 47 and 48 healed. Fig. 4 Fig. 5 Fig. 8 Fig. 7 Fig. 6 42016