Effect of intra-radicular rehabilitation techniques on push-out bond strength of fiber-reinforced posts in extremely flared canals

Statement of the problem: Which technique should be followed to restore excessively flared canals, augmentation of intra-radicular dentin or customization of fiber post? The question asked by many practitioners.
Purpose: To compare the effect of different intra-radicular rehabilitation techniques on push-out bond strength of fiber posts in extremely flared canals.
Materials and Methods: Eighteen freshly extracted human maxillary central incisors roots were endodontically treated and embedded in acrylic blocks. The root canals were excessively flared and divided into six groups according to the technique of intra-radicular rehabilitation; Gr1: Augmentation of intra-radicular dentin by bulk-fill packable composite then cementation of Glassix plus post, Gr2: Augmentation of intra-radicular dentin by bulk-fill packable composite and direct use of Glassix plus post, Gr3: Augmentation of intra-radicular dentin by flowable composite then cementation of Glassix plus post, Gr4: Augmentation of intra-radicular dentin by flowable composite and direct use of Glassix plus post, Gr5: Customization of Glassix plus post by bulk-fill packable composite then cementation of the customized post, and Gr6: Customization of Glassix plus post by bulk-fill packable composite with simultaneous cementation. The roots were sectioned, thermocycled and the specimens were subjected to push-out test in universal testing machine. The maximum failure load was recorded and used to calculate the push-out bond strength. Data was statistically analyzed and failure mode was assessed using magnifying lens.
Results: The highest mean value was recorded in Gr1, followed by Gr2, then Gr4, Gr3, Gr5, with the lowest mean recorded in Gr6. ANOVA test revealed the difference was statistically significant (p=0.0028). Tukey post hoc test revealed no significant difference between groups 1,2,3,4. Gr3 and Gr4 were not significantly different from all other groups.
Conclusions: 1) Higher bond strengths are achievable with augmentation of excessively flared canals compared to customization of prefabricated fiber posts, 2) Augmentation of intra-radicular dentin is highly recommended by bulk-fill packable composite rather than flowable composite, 3) Cementation of light-transmitting post is an important step after augmentation of root dentin by bulk-fill composite, and 4) Use of light-transmitting post in conjunction with bulk-fill composite exhibits synergetic effect in curing depth manifested by high bond strengths. However, the use of one step-single curing method is not recommended.
Clinical Significance: For extremely flared canals, it is advisable to use bulk-fill packable composite for augmentation of root dentin, followed by adhesive cementation of light-transmitting post. Always remember that augmentation of intra-radicular dentin is much better than customization of fiber post.