AFM Observation Of Collapse And Expansion In Collagen Fibrils Network Of Dentin Treated With Different Echants/primers

Objectives:The purpose of the present study was to investigate the dentin collagen network collapse in dry condition influenced by different etching agents using atomic force microscopy.Materials and methods:Twenty dentin disks with 2 mm thickness were harvested in midcoronal dentin of non-carious third molar using a diamond saw under water irrigation. Each dentin surface was sequentially wet ground on 800-,1000-,1500-,2000-,2500-and 3000-grit SiC polishing paper and ultrasonically cleaned in de-ionized water for 30 min. The half of each dentin disk was masked, while the other was applied with respective primer/etchant according to the manufacturers'instructions. Depth changes of the dentin surfaces with respect to the protected reference level in both dry and wet condition were observed and measured by AFM. Statistical analysis was carried out using the SPSS software package (SPSS,16.0 for Windows). One-way analysis of variance(ANOVA) was used to determine statistical differences in depth of demineralization depth between the groups at the a=0.05 level of significance.Results:One-way ANOVA analysis of the data revealed that whether in dry or wet condition, the depths of demineralization using Clearfil SE Bond and iBond were significantly lower than those of 37% phosphoric acid and SuperBond C&B (p 0.05). When in dry condition, the depth of demineralization caused by 37% phosphoric acid was significantly higher than that of Super Bond C&B (p< 0.05) while no significant difference in demineralized depth was found between Clearfil SE Bond and iBond. In wet condition, the demineralized depth caused by Clearfil SE Bond was significantly lower than that of iBond, while there was no significant difference of demineralized depth between 37% phosphoric acid and SuperBond C&B. Moreover, whatever the treatment agent is,the demineralized depth in dry condintion was significant higher than in wet condition (p< 0.05).Conclusion:The depth of demineralization and the extent of collagen network collapse in dry condition caused by total-etching etchants is higher than self-etching primer; whatever the etching system is, the collapse of dentin collagen in dry condition is apparent when comparing to wet condition.