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ePaper created 2016-10-12, 10:31:46 | version 1.38.0
11 3 2016 laser research | Insummary,itcanbestatedthat,under“freehand” conditions ex vivo, only minimal carbonisation of the tissuewasdetected.Althoughthestructuresbeneath this layer showed stronger histological staining, the tissue morphology was completely preserved. There is no detectable evidence of ruptures in the tissue or inthevessels.Theresultsfromtheseexperimentsin- dicate that the cutting efficiency at 980 nm with 3 W outputpowerisatmostaboutthesamecomparedto the445 nmat2 Woutputpower.Thethermaldamage zones and the proportion of carbonised tissue in the region of the cut appear more extensive when using 980 nm.Inaddition,theareaofdestructionoftheep- ithelium (detachment of sub-epithelial connective tissue) lateral to the incision is larger when using 980 nm. The histological results correspond with the available literature when using 980 nm. Irradiation of bone samples also show a consider- ably more pronounced carbonisation and necrosis zone with 980 nm compared to 445 nm (980 nm at 2 W,cw;445 nmat2 W,cw;Fig.6).WithNIRradiation, there is incineration on the surface with a pro- nouncedcarbonisationlayer.Itisconnectedtoawide necrosis zone. When comparing with the same cross-section specimen with 445 nm, there was a narrow carbonisation zone on the surface with an equally narrow necrosis zone beneath it. Cell culture trials Diode lasers primarily induce thermal effects. However, regarding to a wavelength of 445 nm, only afewreportsoftheeffectoflaserradiationatthecel- lularlevelareavailable.Thegoalofcellculturestudies thereforewastoinvestigatetheinteractioneffectsof this radiation in comparison with the established IR infraredlasers.First,itwastobeinvestigatedwhether the wound healing behaviour after laser application of 445 nm and 980 nm differed from that from me- chanical interventions. Furthermore, it was to be in- vestigated whether this laser radiation leads to spe- cific cell damaging effects.23 For the simulation of oral soft tissues, HaCaT and MG-63cellsasmonolayerculturesoncoverslipswere irradiated by diode lasers of wavelengths of 445 nm and980 nmwithpowersettingsof2and3 Wincontin- uouswaveoperation(Figs.7a–d).Forthesimulationof a surgical incision, linear irradiation with a defined traverse speed (3 mm/s) and a defined distance to the monolayer culture (1 mm) was applied. As reference, a mechanicalwoundwasmadewiththelaserapplication tipwithoutthelaserbeingactivated(Figs.7a–d).After irradiation, the morphology of the cells was docu- mented using HE staining and the wound healing be- haviour was assessed by light microscopy. The occur- rence of cytoskeleton alterations and DNA double strand breaks after irradiation was analysed by using fluorescencestaining(phalloidin,p-H2AX;Figs.7a–d). Using the 445 nm wavelength, thermal coupling occuredalreadyatapowerof2W,whereasat980nm this effect required a minimum output power of 3 W andapigmentedmarking.Thermographicanalysisin- dicated a considerably higher temperature increase on the monolayer surface during irradiation with 445 nm(>400°C)incomparisonwith980 nmcaused by the increased absorption of cells at 445 nm. The healing process of the lesions for both laser wave- lengths in the monolayer are comparable to the me- chanical injury (Figs.7a–d). There was no evidence of an increased occurrence of double-strand breaks for bothlasersystems.23 IncontrasttoUVirradiationasa reference,laserirradiationwithbothwavelengthsdid not increase the risk of DNA damages as an indicator for genetic risk (Figs. 7a–d). Antimicrobial effects For many indications, an antimicrobial effect has also been attributed to laser irradiation of differing Fig. 8: Temperature increase T (°C) after irradiation of cultures of E. faecalis and S. salivarius in agar plates at identical conditions with a 445 nm laser and a 980 nm laser in cw mode. The 980 nm laser causes a significantly higher temperature increase. Fig. 9: Haemostatic effects of 445 nm laser irradiation. Coagulation of porcine whole blood (0.1 W, cw/non-contact mode, fiber to object distance 10 mm). Fig. 8 Fig. 9 32016