Effect of coronal macroretentions and diameter of a glass-FRC on fracture resistance of bovine teeth restored with fiber posts

Abstract

Aim: The aim of this study was to evaluate fracture resistance of bovine teeth restored with glass fiber posts of different diameter and shape.

Methods: Eighty single-rooted bovine teeth were prepared, embedded in a PVC cylinder using acrylic resin, and allocated into eight groups (N.=10) based on the post diameter (White Post DC) and shape: smooth double-tapered fiber post -- G1, G2, G3, and G4 with cervical diameters of 1.4 mm, 1.6 mm, 1.8 mm, and 2 mm, respectively; double-tapered fiber post with coronal macroretentions -- G5, G6, G7, and G8 with cervical diameters of 1.4 mm, 1.6 mm, 1.8 mm, and 2 mm, respectively. A three-step etch-and.rinse adhesive and resin cement system was used for postcementation. Afterwards, the core build-up was standardized with composite resin (Oppalis). The specimens were stored for seven days and later submitted to monotonic load at a crosshead speed of 0.05 cm/min (45 degrees ) until failure. The fracture loads were determined and the fracture mode was recorded.

Results: The post diameter (P=0.0007) and post-surface characteristic (P=0.0149) factors affected the fracture resistance results significantly (2-way ANOVA). Low fracture strength values were noted in the group with narrower diameter and macroretentions (G5). The macroretentions damaged the fracture resistance results when post diameter was 1.4 mm (G1 and G5). On fiber posts having diameters of 1.6 mm, 1.8 mm, and 2 mm, macroretentions did not impair fracture strengths significantly.

Conclusions: A direct relation between the diameter of the fiber post and the fracture strength seems likely. Coronal macroretentions reduced fracture strength in thinner fiber posts.