2009 Volume 52 Issue 4 Pages 348-354
Dissolution of calcium hydroxide may be a key mechanism for the biological properties of mineral trioxide aggregate (MTA). However, the dissolution may also be a factor that affects the physical properties of this material. In this study, we analyzed the distribution of various elements in MTA leached in water, in order to investigate compositional changes that occur during the process of calcium dissolution. MTA (ProRoot® MTA, white) was mixed according to the manufacturer's instructions, placed in cylindrical molds and stored for 24 hours at 37℃ in 100% humidity. The specimens were then suspended in distilled water for 7, 14 and 28 days. Specimens without water immersion served as controls. The distribution of Ca, Si, Bi and Al was analyzed with an electron probe microanalyzer (EPMA) along the cross-section of the specimens. Elemental analysis of the surface was also conducted in selected specimens. Formation of a layer of low Ca concentration (Ca-leached layer) was clearly detected in the periphery of leached MTA specimens. This layer showed a relatively clear boundary and increased in thickness with time. Moreover, precipitates composed mainly of calcium carbonate were formed on the surface of MTA. Si and Al formed a zone of increased concentration within the Ca-leached layer. It was concluded that water exposure of MTA resulted in the formation of a Ca-leached layer, although the process was not a one-way dissolution process but involved surface precipitation of calcium carbonate and Si and Al concentration within the Ca-leached layer.
