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ePaper created 2017-10-05, 09:25:28 | version 1.38.0
Chi-square-Test (laser application with absorber) n = 3 p > 0.05 p > 0.05 group I group II group III p > 0.05 group IV p > 0.05 laser_magazine Chi-square-Test (laser application without absorber) Chi-square-Test (laser application with/without absorber) Chi-square-Test n = 12 n = 3 p > 0.05 p > 0.05 p > 0.05 p > 0.05 n = 6 p > 0.05 p > 0.05 p > 0.05 p > 0.05 group I+II (with smear layer) group III+IV (without smear layer) group I+III (with pH-cycling) group II+IV (without pH-cycling) group I-IV (with absorber) group I-IV (without absorber) The dimension of the pattern we detected after pH-cycling in Groups 1 and 3 was not dependent on removal of the smear layer. In fact, it was dependent on pH-cycling, because without pH-cycling (Groups 2 and 4) such a pattern could not be detected. Con- cerning these facts, the width of detected patterns in this study could be associated with demineralisation and remineralisation and be connected to the acid resistance of the treated dentinal samples. We as- sumed that the width of the pattern was inversely proportional to acid resistance; that is, it is consis- tent with the amount of demineralisation. Thus, an enhancement of acid resistance was demonstrated with reduced pattern width. This was the statistically significant finding after fluoridation compared with laser application in Group 1. We assumed that on surfaces with a smear layer fluorides were more eas - i ly incorporated into the dentinal surface and served as a depot. This was first used up after acid contact. In the histological examination, reduced demineral- isation width was observed for this reason. In pa- tients with hypersensitive tooth necks, in most cases, a relatively uniform and amorphous smear layer is missing, there are more areas with wider tubule ori- fices and sometimes even loss of intertubular den- tine compared with non-sensitive tooth necks.39 p > 0.05 p < 0.05 p > 0.05 p > 0.05 p > 0.05 p > 0.05 Clinical observations have demonstrated at least a temporary reduction of pain after a single fluoride application.32 So the question is, whether the effects detected after pH-cycling and fluoridation can en- hance and sustain acid resistance in vivo. Tab. 3_Results of statistical analysis of morphological effects depending on surface treatment in SEM examination; p = 0.05. Acid resistance after fluoride application Our study demonstrated a statistically significant association between fluoride application and an enhancement of acid resistance on smear layer- afflicted surfaces only. With removal of the smear layer, no differences between the treatment modali- ties were observed. We assumed that fluoridation of a surface without a smear layer did not exceed the effects achieved with laser application or laser–fluo- ride treatment. Clinical investigations of such a com- bined treatment with fluoridation found no addi- tional positive effect,34 and this result is in agreement with the morphological findings of our in vitro study. Furthermore, laser application or a combined treat- ment on acid-etched surfaces was not inferior to fluoridation alone. An improvement in acid resist- ance has been observed when fluorides are applied prior to laser application.40 Hsu et al.22 demonstrated such a combined treatment with melting and setting of the dentinal surface in an in vitro study. Further laser 3_2017 4545