Objective To investigate the correlation of morphological characteristics and failure modes of two types
of glass-fiber posts luted with self-adhesive resin cement and etch-and-rinse adhesive system. Methods Thirty-six
intact single-rooted premolars were collected and removed the crown. After root canal therapy, teeth were randomly divided into 4 groups. Group A: Self-adhesive with POPO fiber post. Group B: Etch-and-rinse with POPO fiber posts. Group C: Self-adhesive with Para Post. Group D: Etch-and-rinse with Para Post. Each root was sectioned into six 1mmthick serial slices and a push-out test was performed. The dentin-cement-post adhesive interface of each specimen and failure modes after fracture were evaluated by stereomicroscope observation. Results Interface morphology observe indicated that voids present in group B（64.2%） and D（66.7%） were significantly higher than group A（5.8%） and C （13.7%）（P ＜0.001）. Interface gaps appeared at the resin -dentine interface in group D（41.2%） were significantly higher than group A（13.5%） and C（11.8%）（P＜0.008 3）, and the failure modes in each group were significantly different （P＜0.008 3） except for group A and B（P=0.69）. Conclusion Voids present in cement layer were associated with the luting agent involved. Morphological characteristics of the fiber post-resin luting agent-root dentin adhesive interface were discrepant with failure modes in different root region. There were interaction between adhesive systems and fiber posts.
