Structure and Chemical Composition of an Experimentally Formed Apical Barrier after the Application of Calcium-Glycerophosphate

Transformation in the structure and composition of calcium-glycerophosphate (Ca-GP) was investigated using a scanning electron microscope fitted with an energy dispersive X-ray microanalysis (EDX) system. Ca-GP was packed inside roots that were subsequently implanted into the mandibles of rats to stimulate the formation of an apical barrier. Scanning electron microscopic observations of packed Ca-GP revealed three types of structures: globular aggregates, plate or flake-like aggregates, and granular aggregates. The average Ca/P molar ratios of EDX by area mode—postoperatively obtained at days 1, 3, 5, and 7—were 1.300, 1.533, 1.472, and 1.495 (analytic area: 0.01 to 0.03 mm²) and those of EDX by point mode were 1.220, 1.451, 1.487, and 1.467 (analytic point: 0.05 μm²). The magnesium (Mg) weight percentage was found to be ∼1.9 at days 3, 5, and 7, similar to Mg-substituted whitlockite. These findings suggest that Ca-GP are transformed, over a period of 3 days into Mg-substituted whitlockite as a result of being hydrolyzed by tissue fluid.