Effect of root canal molding method on bond strength and cement thickness of milled fiber posts

This study evaluated the bond strength (BS), cement thickness, gap formation, voids, and failure modes of milled fiberglass posts (FGPs). Thirty single-rooted premolars underwent endodontic treatment and were decoronated. Specimens were divided into two experimental groups based on the canal molding technique: acrylic resin (AR) pattern (n = 15) and silicone molds (n = 15). After scanning, retainers were milled from a fiberglass block (Fiber CAD, Angelus) and cemented with dual-cure self-adhesive resin cement (RelyX U200, 3 M ESPE). Radiographs assessed gap presence. The roots were sectioned to obtain 1-mm slices from each root third-one for push-out BS testing and another for scanning electron microscope (SEM) analysis to measure cement thickness (CT) and voids at the adhesive interface. Data on gaps, BS, voids, and CT were statistically analyzed (α = 5%). In the cervical third, the silicone mold showed higher BR compared with the AR technique (p < 0.05). In the apical third of the root, the AR technique showed higher BS than the silicone mold technique (p < 0.05). Regardless of the root third, CT was significantly greater in the AR technique (p < 0.05). Regardless of the technique, CT was lower in the cervical third than in the middle and apical thirds (p < 0.05). The molding technique did not affect gap (p > 0.05). In the apical third, the percentage of voids was higher in the silicone mold group (80.0%) compared with the AR pattern group (20.0%) (p < 0.05). It can be concluded that the molding technique affected the BS of milled FGPs depending on the root third. Although the AR pattern resulted in greater CT, fewer voids were observed in the middle and apical root thirds compared with the silicone molding technique.