Theoretical method for a radiopacifier proportion calculation in MTA type cements.

This article deals with the problem of determining the proportion by weight of radiopacifying material needed to add to a cement clinker of mineral trioxide aggregated (CE) to comply with ISO 6876/2001 and ANSI-ADA 57 regulations for radiopacity. With this aim, CE was synthesized and mixed experimentally with 5, 10, 15, and 20 wt% of ZrO as radiopacifying material. Radiographic images were taken so that radiographic density was obtained and related to the mmAl scale by using an aluminum step wedge. From a theoretical point of view, absorbed intensity given by the Lambert-Beer law was calculated using mass attenuation coefficients (NIST database) for each chemical element included in each component of the cement samples. In this way, we predicted that by adding above 10 wt% of ZrO to the CE, the requirements stipulated by ISO 6876 for radiopacity were satisfied with discrepancies around 1 mmAl. This theoretical method gives an excellent approximation to determine the amount of radiopacifying material needed to meet the requirements stipulated by ISO.