Fracture strength of fragment-bonded teeth. Effect of calcium hydroxide lining before bonding

Purpose: To measure, in vitro the strength of intact teeth, fracture-bonded teeth, and fracture-bonded teeth bonded after a preliminary calcium hydrox ide lining of the dentin part of the remaining tooth. Materials and Methods : The study used 30 young, similarly aged sheep incisors. Twenty incisors w ere fractured 2.5 mm from the incisal edge and another 10 incisors remained non-fractured and served as control (Group 1). Group 2 comprised 10 fractu red incisors, which after 3 weeks water storage were bonded by use of acid etching and a dentin bonding agent. In Group 3, the root part of 10 fractur ed incisors were lined with calcium hydroxide and kept in water for 3 weeks . Then the lining was removed with a hand instrument before bonding as abov e. The strength of the teeth in Goups 1-3 was measured and the mean fractur e strengths representing the three groups were compared by Newman-Keuls' mu ltiple range tests at a 5% level of significance. Results: The mean fractur e strength of the lined teeth (9.6 MPa) was significantly different from th at of intact teeth (17.8 MPa) as well as from that of the bonded but unline d teeth (15.8 MPa). The latter two means were not significantly different. It is concluded that the use of calcium hydroxide on the fracture surfaces of fractured teeth before bonding lowers the fracture strength of the resto red teeth.