Intra-radicular hydrostatic pressure changes during the cementation of post-retained crowns

The intra-radicular hydrostatic pressures generated during the cementation of parallel-sided dental posts have been measured. Pressures are generated only when cement is inserted into the prepared post hole. Using zinc phosphate cement, with posts placed 2 min from the commencement of mixing, pressure has been shown to depend on post diameter, the closeness of fit, and the powder-liquid ratio. The maximum pressure recorded was 1.7 x 10(4) kN/m2 using a 1.3 mm diameter post, a mean cement film thickness of 37 microns, and an ideal powder-liquid ratio of 3.0. Pressures similar to that generated using zinc phosphate cement were recorded when black copper phosphate was used as the lute, but zinc polycarboxylate generated less pressure, and an ortho-ethoxy benzoic acid cement markedly less pressure. Before it is possible to confirm the ideal luting cement for posts, further studies of the effectiveness of cement release channels, and post retention, are necessary.