Micro-pushout Bond Strengths of Short Root Posts

Objectives: Root posts with a reduced length (6 instead of 9 mm) and retention for the core are offered to allow an apically root canal filling as well as the positioning of the core on the bottom of the pulp chamber. They are prefabricated with a surface coating. The aim of the study was to compare the micro-pushout bond strengths (µPBS) of the new 6 mm posts with those of conventional 9 mm posts that were inserted only with 6 mm depths. Methods: The clinical crowns of 60 freshly extracted anterior human teeth were cut perpendicular. Root canals of all teeth were treated. 3 types of 6 mm deep post space preparations were performed using respective instruments: for the 6 mm post with coating (6CO) and without coating (6UN) and 9 mm conventional post (9UN). Respective titanium (Ti) and FRC posts (n=10) were inserted using RelyX Unicem, stored wet and undergone thermocycling (5°/55°C, 5000x). Then the roots were cut horizontally into 1 mm thick slices. µPBS were measured and calculated for the coronal (CR), medium (MR) and apical (AR) region regarding the individual surface areas. Statistical significant differences were calculated (ANOVA, Bonferroni correction, α=0.05). Results: For Ti highest µPBS were found using 6CO at CR (11.0±6.4 N/mm2) and for FRC using 9UN at CR (11.1±6.6 N/mm2). Lowest µPBS were assessed for Ti at 9UN-MR (4.7±2.8 N/mm2) and for FRC at 6UN-MR (5.7±4.1 N/mm2). µPBS did not differ significantly comparing post types of the same material as well as root segments of the same post type (p>0.05, 1-way ANOVA). Whereas overall post types as well as post segments turned out to be a significant factor (p<0.05, 4-way ANOVA). Conclusions: Short posts of Ti as well as FRC revealed at least similar µPBS than conventional posts.