Durability of adhesion between an adhesive and post-space dentin: Push-out evaluation at one and six months.

Aims The aim of this study was to investigate, by means of the push-out test, the bond of Prime & Bond NT at various post-space dentin locations and the influence of time of water storage on bond strength values. Methods 30 single-rooted teeth were used for the bond strength measurement. In each tooth fiber posts were cemented with the commercial bonding system “Prime & Bond NT” in combination with the resin-based filling material “Opticore Cure Core Composite”. After 24 h (group A: 10 roots), 1 month (group B: 10 roots), and 6 months (group C: 10 roots) of water storage, the specimens were sectioned in 1 mm-thick slices for the push-out test. The data were divided into three regions (coronal/middle/apical) and analyzed using Kruskal-Wallis Test and Mann-Whitney U Test (p<0.05). Results The bond strength values registered did not show statistically significant differences within group A and C; within group B statistically significant differences were found between the coronal and the middle thirds and between the coronal and the apical third. The apical bond strength values did not show any statistically significant difference among the three groups (Kruskal-Wallis test); in the middle thirds a statistically significant difference was found at 6 months when compared with the 24 h and 1-month samples. In the coronal thirds was found a statistically significant difference between 1 month and 6 months. Analysis of the specimens under optical microscope revealed a prevalence of adhesive failures between fiber post and root dentin. Conclusions Bond strength values are lower at the apical third. Over time the adhesion of the fiberpost/luting cement/post-space dentin does not remain stable.