SummaryDynamic fracture energies and patterns of fracture in extracted human central incisors were determined for groups of intact controls, groups with Vita Dur N® crowns, Vita Hi Ceram® crowns, Dicor® crowns and porcelain veneers. Teeth were struck on their middle labial surfaces by a pendulum impact device.The mean fracture energy for teeth with Dicor crowns was significantly lower than for all other groups (P<0.05). Control tooth crowns fractured obliquely in an apicaldirection. Vita Dur N® and Dicor® crowns, shattered, the underlying tooth usually fracturing in the plane of the impact force. Vita Hi Ceram® crowns chipped at the site of impact and some fractures were located in the roots. Gold crowns remained cemented and fracture occurred at the crown/root junction, or in the root. Porcelain veneers fractured at the site of impact but remained cemented. Dicor® crowns were less fracture resistant than other restoration types tested. Porcelain veneers and full gold crowns stiffened teeth which led to more root fractures than the porcelain