Effect of airborne-particle abrasion on 3-dimensional surface roughness and characteristic failure load of fiber-reinforced posts

Statement of problem: Debonding is the most common complication of fiber-reinforced posts (FRPs). Airborne-particle abrasion (APA) has been suggested to increase resin cement adhesion to the surface of FRPs. However, which abrasion protocol is the most favorable is unclear. Purpose: The purpose of this in vitro study was to compare the surface roughness and characteristic failure load of three FRP systems following different APA protocols. Material and methods: A total of 150 posts from 3 manufacturers (glass FRP, quartz FRP, and zirconia-enriched glass FRP) were randomly assigned to different surface treatments (NT: no treatment—control; E0: cleaned with 96% ethanol solution; E2: APA for 2 seconds/mm ² —ethanol cleaned, E5: APA for 5 seconds/mm ² —ethanol cleaned; and E10: APA for 10 seconds/mm ² —ethanol cleaned) forming 15 groups in total. APA was performed with 50-μm aluminum oxide. Each post was observed under a 3-dimensional (3D) laser microscope, and average 3D surface roughness (Sa) was measured. Failure was induced with a universal testing machine. Two specimens per group were evaluated under the same microscope to evaluate failure patterns. Surface roughness data were analyzed with the Welch ANOVA (α=.05), followed by the post hoc Games-Howell test. Failure load differences were determined by 2-parameter Weibull statistics and likelihood ratio contour plots (95% confidence bounds). Results: Statistically significant differences were found in the mean surface roughness among the groups (Welch ANOVA, P<.001). APA resulted in a significant surface roughness increase in all tested post systems. No surface roughness difference was found between surface treatments E2, E5, and E10 in any tested post systems. Weibull statistics and likelihood contour plots revealed a significant decrease in the characteristic failure load for glass FRP after surface treatment E2 (88.7 N) compared with the control (95.3 N). Quartz FRP showed a significant decrease in the characteristic failure load after surface treatment E5 (103.6 N) compared with the control (108.9 N). Zirconia-enriched glass FRP showed no significant decrease in the characteristic failure load after any of the tested surface treatments. Qualitative morphological changes and failure pattern differences were observed among the tested post systems after the different surface treatments. Conclusions: APA significantly increased surface roughness in all post systems. APA effects on characteristic failure load were dependent on the material used.