RESUMO
<p><b>OBJECTIVE</b>To study the fracture resistance and the failure pattern of horn-shaped root canal orifice restored by different materials.</p><p><b>METHODS</b>Fifteen human maxillary central incisors were selected. After schedule root canal therapy, the residual dental roots with horn-shape root canal orifice were prepared. The specimens were assigned to three groups randomly. A group was rehabilitated by casting metal post-core crown. B group was rehabilitated by prefabricated fiber post and composite core crown. C group was rehabilitated by shapeable fiber-reinforced composite resin post and core crown. Loads were applied on the samples at 130 degree to the long axis of the root and measured with universal testing machine. The failing patterns were recorded.</p><p><b>RESULTS</b>There were no difference in fracture resistance among three groups (P>0.05). But the failing patterns were different. A group manifested root fracture and separation between cement and root dentin. B group mainly manifested separation between cement and post. C group manifested separation between cement and root dentin.</p><p><b>CONCLUSION</b>For restoration of residual dental root with horn-shaped orifice, fiber composite post-core crown has advantages in residual root protection and once more restoration.</p>