Stresses and deflections in the floor of model cavity preparations

Summary In this study the finite element method was used in conjunction with an axisymmetric model of an idealized first molar to determine the stresses, as well as deflections in the floor of a cylindrical cavity preparation as caused by condensers of various sizes. It was found that for the 0·25 mm thickness of dentine, the 2 mm condenser and a 2 kg load, a tensile stress of approximately 70 MN/m2 was obtained near the centre of the preparation. Under the same load and a 4 mm condenser a tensile stress of only 42 MN/m2 was obtained. Bowen & Rodriguez (1962) and Lehman (1967) reported that the tensile strength of dentine was in the order of 51.7 MN/m2 and 41.5 MN/m2 respectively. Thus it was demonstrated that for certain combinations of load, condenser size, and cavity dimensions, the tensile strength of the dentine in the cavity floor could be exceeded and failure of the cavity floor could ensue.