Objectives: To describe the fracture pattern of endodontically treated teeth restored with direct composites, with and without glass fibre reinforcement. Methods: Fifty seven extracted maxillary premolar teeth were endodontically treated. The teeth were consequently divided into 4 groups, prepared and restored as follows: group 1 had an occlusal restoration, group 2 an MOD restoration, group 3 an occlusal restoration with fibre reinforcement and group 4 an MOD restoration with fibre reinforcement. The teeth were thermocycled and embedded in acrylic resin with the simulation of a periodontal ligament. The specimens were stored in saline at 37 degrees C during preparation and for a minimum of 24hrs before testing. The specimens were fractured in a universal testing machine with the long axis of the roots at an angle of 30 degrees to the direction of the load. The failure mode was evaluated both visually and microscopically at 10x magnification. Fractures were classified as type 1: fractures of the coronal third of the cusp, type 2: fractures between the coronal third of the cusp and the CEJ, type 3: fractures below the CEJ and type 4: root fractures. Results: For group 1: type 1 fractures 2(14%), type 2 fractures 4(29%), type 3 fractures 6(43%) type 4 fractures 2(14%). For group 2: type 1 fractures 2(14%), type 2 fractures 0, type 3 fractures 11(79%), type 4 fractures 1(7%). For group 3: type 1 fractures 6(40%), type 2 fractures 6(40%), type 3 fractures 3(20%), type 4 fractures 0. For group 4: type 1 fractures 6(43%), type 2 fractures 7(50%), type 3 fractures 1(7%), type 4 fracture 0. Conclusion: The inclusion of glass fibre in the restoration of endodontically treated teeth leads to a more favourable breaking pattern in the event of fracturing.
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