Effect of post-space preparation timing on the bond strength of fiber posts

To compare the effects of immediate versus delayed post-space preparation on the bond strength of fiber posts and the fracture resistance of roots after root canal obturation using iRoot SP and the single-cone technique, and to provide an experimental basis for the selection of the timing of clinical post-space preparation.

This study was approved by the Medical Ethics Committee of the institution, and written informed consent was obtained from all participants. Seventy-two extracted human single-rooted premolars were randomly divided into two groups (n = 36 each): the immediate post-space preparation group (post-space preparation performed immediately after root canal obturation) and the delayed post-space preparation group (post-space preparation performed 1 week after root canal obturation). Cleanliness of the root canal walls was assessed with a dental microscope after preparation in both groups; the ultrastructural characteristics of the dentinal surface were examined via scanning electron microscopy; the fracture resistance of roots was measured with root fracture resistance tests; the bond strength of the fiber posts was measured with the thin-slice push-out test; and the bond failure modes were observed and analyzed under a stereomicroscope.

Under dental microscopy, the dentin surface of the immediate post-space preparation group appeared cleaner than that of the delayed post-space preparation group. Scanning electron microscopy revealed that most dentinal tubules remained open in the immediate post-space preparation group, while the tubules in the delayed post-space preparation group showed incomplete patency. The fracture resistance of the immediate post-space preparation group was (2 872 ± 241.5) N and that of the delayed post-space preparation group was (2 934 ± 353.1) N, with no statistically significant difference (t =-0.328, P = 0.751). The push-out bond strength of the immediate post-space preparation group (10.310 ± 2.907) MPa was significantly higher than that of the delayed post-space preparation group (7.917 ± 2.429) MPa, with a statistically significant difference (t = 4.457, P < 0.001). Analysis of failure modes showed that adhesive-to-dental interface failure was the predominant mode in both groups.

Following root canal obturation with iRoot SP using the single-cone technique, immediate post-space preparation yields superior fiber post bond strength compared to delayed post-space preparation, without compromising root fracture resistance.