Effect of Different Post-space Pretreatment Agents on the Push-Out Bond Strength of Fibre Posts Cemented With Self-Adhesive Resin Cement: An In Vitro Study

Background: The long-term success of fibre post restorations is multifactorial and depends on several biomechanical and restorative factors, including the ferrule effect, the amount of remaining coronal tooth structure, restoration design, occlusal loading, and the quality of adhesion between the fibre post, resin cement, and radicular dentin. Among these factors, durable adhesive bonding is considered essential for enhancing post retention and the longevity of the restoration. The smear layer created during post-space preparation may compromise this adhesion by limiting resin infiltration. Pretreatment of the post space with different conditioning agents has been proposed to improve the bonding performance of self-adhesive resin cements; however, comparative evidence regarding these four conditioning agents remains limited. The present study aimed to evaluate and compare the effect of different post-space pretreatment agents on the push-out bond strength of glass fibre posts luted with self-adhesive resin cement. Materials and methods: Forty extracted human permanent maxillary central incisors were endodontically treated and randomly allocated into four groups (n = 10) according to the post-space pretreatment agent used: Group I (17% ethylenediaminetetraacetic acid (EDTA)), Group II (10% citric acid), Group III (10% polyacrylic acid), and Group IV (37% phosphoric acid). Following standardised post-space preparation, glass fibre posts were cemented using a self-adhesive resin cement. Each specimen was sectioned into 2-mm-thick slices representing the coronal, middle, and apical thirds of the root. Push-out bond strength was evaluated using a universal testing machine and expressed in megapascals (MPa). Data were analysed using one-way analysis of variance (ANOVA) followed by Tukey's honestly significant difference (HSD) post-hoc test for intergroup comparisons, and a linear mixed-effects model (REML) followed by Tukey's multiple comparisons test for within-group comparisons among the coronal, middle, and apical root thirds. A P-value < 0.05 was considered statistically significant. Results: The 37% phosphoric acid group demonstrated the highest push-out bond strength at all root levels, followed by 10% polyacrylic acid, 10% citric acid, and 17% EDTA, which consistently showed the lowest values. Bond strength progressively decreased from the coronal to the apical third in all pretreatment groups. One-way ANOVA revealed significant intergroup differences at the coronal, middle, and apical root levels (all P < 0.0001). Tukey's HSD post hoc analysis demonstrated significant pairwise differences between most groups, except between the 10% citric acid and 10% polyacrylic acid groups at the middle and apical thirds. Linear mixed-effects model analysis showed significant differences in bond strength among the coronal, middle, and apical thirds within each pretreatment group (all P < 0.0001), with the greatest reduction occurring between the coronal and apical thirds. Conclusion: Post-space pretreatment significantly influenced the immediate push-out bond strength of glass fibre posts cemented with self-adhesive resin cement. Among the conditioning agents evaluated, 37% phosphoric acid demonstrated the highest bond strength. Further in vivo studies are needed to confirm the clinical applicability of these findings.