The aim of this in vitro study was to evaluate the fracture resistance of upper and lower incisors restored with glass fiber reinforced posts (FRP). There were 32 upper and 32 lower incisors endodontically treated and FRPs were cemented, using pretreated (Rocatec) and non-pretreated posts. Crowns were fabricated and cemented with Ketac-cem or Panavia. Additionally, eight upper and lower incisors with intact natural crowns were used as control groups. Mandibular incisors restored with FRPs attain fracture strengths comparable to those of natural teeth. The fracture strength of all teeth was increased by using Rocatec. Cementation of the crowns using Panavia only increased the fracture strength in upper incisors. Rocatec used to pretreat the posts and crowns cemented using an adhesive cement appear to reduce the risk of clinical failure.