The Effect Of Different Combinations Of Irrigations On Bond Strength Of Fiber Post

Objective:To evaluate the bond strength between fiber posts and dentin surface of post space after treating with different combinations of irrigation and provide references for clinical practice.Materials and Methods:1.Forty human single-rooted premolars were sectioned transversely at 2 mm coronal to the cemento-enamel junction(CEJ).After root canal therapy,the specimens were incubated in normal saline for seven days at room temperature.The post spaces were enlarged for a No.4(diameter,1.3 mm)glass fiber reinforced composite post with matching drill.Following post space preparation they were divided into four groups(n=10)randomly and each group was rinsed with different solution{ group A,distilled water;group B,0.5%NaCLO;group C,0.5%NaClO+MTAD;group D,0.5%NaClO+17%EDTA}and dried.Fiber posts were cemented using Self-Etch Resin Cement(3M ESPE Adper? Easy One).After 24 hours,one 2mm thick slice was obtained from each apex of specimen.Slice samples were then subjected to a pull-out bond strength test and failure modes were examined.Data of bond strength were analyzed by one-way analysis of variance(ANOVA)and LSD-t test.The chi-square test was performed on the fracture interface using the composition ratio calculation method.2.Four human single-rooted premolars were sectioned transversely at 2 mm coronal to the cemento-enamel junction(CEJ).After root canal therapy,the specimens were incubated at room temperature and normal saline for seven days.The post spaces were enlarged for a No.4(diameter,1.3 mm)glass fiber reinforced composite post with matching drill.Following post space preparation they were assigned to four groups(n=10)randomly and all canals were rinsed with different solution{ group A,distilled water;group B,0.5%NaCLO;group C,0.5%NaClO+MTAD;group D,0.5 % NaClO+17% EDTA}and dried.After irrigation,specimens were thenlongitudinally sectioned in labio-lingual direction and examined under scanning electron microscopy(SEM)for smear layer removal at the apical,middle,and cervical thirds of the root canal.Results:1.The bound strength of group A,B,C and D was 12.85±0.90,14.47±0.76,20.47±1.05 and 24.83±1.39 MPa respectively(A vs B,P<0.01;A vs C,P<0.01;A vs D,P<0.01,B vs C,P<0.01,B vs D,P<0.01,C vs D,P<0.01).Fracture specimens of each group were hybrid damage except group A.2.SEM observation showed the post space dentin surfaces were covered with a large area of smear layer,and dentinal tubules tended to be opened rarely in group A.In group B,most of the smear layer was removed,the dentinal tubules were partially opened,and some contained debris.In Group C,from the apical to the cervical area,the cleaning effect was uniform,the surfaces of post space were basically free of smear layer,and a small number of dentinal tubules contained debris.In group D,no smear layer was observed on the surfaces of the post space,all the dentinal tubules were clean and opened with slight demineralization around the tubules.Conclusion:The preparation process of the post with 0.5%NaClO solution and 17%EDTA solution could remove smear layer and improve the bond strength effectively.