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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 micron 2). The magnesium (Mg) weight percentage was found to be approximately 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.

This case demonstrates an artificial apical barrier formation by using calcium-beta-glycerophosphate paste in a nonvital permanent tooth with an open apex communicating with the maxillary sinus. The long-term satisfactory outcome of this case depended on the resolution of periapical pathosis and root canal obturation without overextension.