Effect of Short and Long Fiber-Reinforced Composite Resins Used as Post and Core on Fracture Resistance of Premolars: An in vitro Study

Background: Endodontically treated (ET) premolars with a compromised tooth structure have been recorded to end with a high prevalence of catastrophic fracture. Objective: To compare the fracture resistance (FR) of ET premolars with MOD cavities restored with two fiber-reinforced composites as cores or post-cores. Methods: 60 premolars were divided into six groups (n=10): five experimental groups (A-E) and one control group with sound teeth (F). The experimental groups with MOD cavities were endodontically treated and restored differently. Group A was restored with a core of one bulk fill composite resin (OBF). Groups B and C were fixed with either a core of EverX flow short fiber-reinforced composite (SFRC), a layer of Ribbond polyethylene fiber, or OBF. In order to fill a 6 mm post space within the palatal roots, groups D and E first underwent direct layering with SFRC or Ribbond and OBF coverage. Samples were thermocycled and subjected to a fracture resistance test using an Instron machine at 0.5mm/min. Results: The highest FR value was recorded for the sound teeth (1789N), and the least was for group A (938N). All the experimental groups recorded significantly lower FR compared with sound teeth (p