RESUMEN
Several materials are recommended for retrofilling. One of the best materials that have ever been suggested is MTA [Mineral Tioxide Aggregate]. Many studies have confirmed the biocompatibility, proper marginal adaptation and sealability of this agent. The purpose of this study was the evaluation of apical evaluation of apical microleakge in cavity preparation with different dimension for retrograde. In this study, we examined the influence of cavity dimension on sealability of MTA. We selected sixty roots with a single canal. After cleaning and shaping, the canals were obturated with guta-percha and canal sealer by lateral condensation technique. Samples were divided into 5 groups: two positive and negative control groups and three experimental groups. Cavity preparation was performed for all experimental groups with the following methods: A: 1.5mm depth and 0.6mm width B: 3mm depth and 0.6mm width C: 3mm depth and 1.5mm width After cavity preparation, MTA powder was placed in each cavity and wet cotton adjacent to them for 24 hours. Then the samples were placed in Incubator [37 degree C and 100% wet] for 72 hours. Subsequently dye penetration examination was performed; dye leakage was measured by stereomicroscope. We used T-test for statistical analysis. After statistical analysis these results were achived: 1. Increase depth from 1.5mm to 3mm reduce the amount of leakage. 2. No significant difference between leakage of cavities with different width was found [P-value>0.05]. It's better to prepare cavities for retrograde filling with more depth and less width