Direct restoration of severely damaged incisors using short fiber-reinforced composite resin.

The aim of this in vitro study was to evaluate the static load-bearing capacity and the failure mode of endodontically treated maxillary incisors restored with complete crowns made of experimental composite resin (FC) with short fiber fillers, with and without root canal posts. Further aim was to evaluate the effect of fiber-reinforced composite resin (FRC) on the failure mode of the restoration. The experimental composite resin (FC) was prepared by mixing 22.5 wt.% of short E-glass fibers (3mm in length) and 22.5 wt.% of semi-interpenetrating polymer network (IPN) resin with 55 wt.% of silane treated silica fillers. The clinical crowns of 30 human extracted maxillary incisors were sectioned at the cemento-enamel junction. Five groups of direct complete crowns were fabricated (n=6); Group A: made from particulate filler composite resin (PFC) (Grandio Caps, VOCO, control), Group B: PFC with fiber post (everStick, StickTeck), Group C: made from PFC with everStick fiber post and FRC-substructure, Group D: made from FC, Group E: made from FC with FRC-substructure. The root canals were prepared and posts were cemented with resin cement (ParaCem Universal). All restored teeth were stored in water at room temperature for 24h before they were statically loaded with speed of 1.0 mm/min until fracture. Data were analyzed using ANOVA (p=0.05). Failure modes were visually examined. ANOVA revealed that restorations made from experimental fiber composite resin had higher load-bearing capacity (349N) (p<0.05) than the control restorations (173N). No significant difference was found in load-bearing capacity between restorations reinforced with FRC-substructure and those without (p>0.05). Restorations made from short glass fiber containing composite resin with IPN-polymer matrix showed better load-bearing capacity than those made with either plain PFC or PFC reinforced with fiber post.