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ePaper created 2017-10-05, 09:25:28 | version 1.38.0
laser_research Fig. 3_Left side: Schematical illustration of the detected pattern with breakpoints. White arrows are showing the measure points (black lines); red arrows illustrate the width of the pattern (red band); deep dentin is marked in yellow. Right side: Original specimen. phological changes in the dentinal structure, but led to ultrastructural modification of the superficial dentinal layer. Since the degree of pain is strongly correlated to the number of open tubules at the dentinal surface10, removal of the smear layer prior to treatment best simulated hypersensitive dentine. Ac- cordingly, under SEM examination, a great number of open tubules were observed in the control quadrants in Groups 3 and 4. Results after laser–fluoride treatment Laser-treated surfaces with a smear layer showed narrowing or complete closure of the denti- nal tubules, but the results were not statistically sig- nificant. In comparison to the control and fluorida- tion, a statistically significant reduction in the num- ber of open tubules was found after laser and laser–fluoride treatment of acid-etched surfaces. This demonstrated that laser application can induce sealing of hypersensitive dentine to some extent. These results are in accordance with those of Umana et al.,19 who evaluated the effect of 810 nm, among others, diode laser application (Claros Nano, Elexxion) at different energy settings on human dentinal surfaces after removal of the smear layer. With an energy setting of between 0.8 W and 1 W (continuous wave, non-contact mode for 10 sec- onds), they found a narrowing of dentinal tubule orifices, and hence deduced that the diode laser was able to seal dentinal tubules. In our study, melted surfaces predominantly were detected after laser application with statistical sig- nificance in Groups 1 and 3. Laser application fol- lowed by fluoridation appeared to enhance the oc- cluding effects, but this was not of statistical signifi- cance. Melting of dentinal surfaces after laser appli- cation using different parameters with or without fluoridation has also been described previously.22–24 Marchesan et al.25 too demonstrated such a melting Furthermore, we analysed samples in relation to pre- and post-treatment, that is, with smear layer re- moval and pH-cycling. Figure 2 provides an overview of the pre- and post-treatment classification of the groups. In all samples with a smear layer (Groups 1 and 2 combined), no statistically significant differ- ences were observed (chi-square test, p > 0.05; Table 3), whereas statistically significant differences between the treated quadrants in all samples with the smear layer removed (Groups 3 and 4 combined) were detected (chi-square test, p < 0.05; Table 3). After laser application and after laser–fluoride application, fewer wide-open and partly occluded tubules, and smooth and unstructured surfaces were observed. Melted surfaces predominantly were detected after laser and after laser–fluoride application. Regarding all samples with pH-cycling (Groups 1 and 3 com- bined) and without pH-cycling (Groups 2 and 4 com- bined), no statistically significant differences were observed (chi-square test, p > 0.05; Table 3). _Discussion The histological and SEM examinations demon- strated that the application of a diode laser (809 nm, 1 W, 10 Hz, 60 seconds) did not induce harmful mor- Tab. 2_Results of statistical analysis of the histological examination of group I (with smear layer, with pH-cycling); p = 0.05. 42 3_2017 42 laser Wilcoxon-Test Mann-Whitney-U-Test laser + fluoridation – laser (with/ without absorber) fluorides – laser (with/ without absorber) control – laser (with/ without absorber) fluorides – laser + fluorides (with/ without absorber) control – laser + fluorides (with/ without absorber) control – fluorides (with/ without absorber) p > 0.05 p > 0.05 p > 0.05 p > 0.05 p > 0.05 p > 0.05 p > 0.05 p > 0.05 p > 0.05 p > 0.05 p > 0.05 p > 0.05