The root canal filling paste Vitapex (Neo Dental Chemical Products Co., Tokyo), made of calcium hydroxide and iodoform with the addition of silicone oil, was experimentally introduced into the mandibular canals of 29 dogs. Tissue reactions to the paste were examined by radiography, histopathology, and electron microscopy. These examinations revealed that the paste was phagocytosed by macrophages and, in general, was gradually resorbed over time. The paste was also found to cause heterotopic calcification and/or ossification within the area of original penetration.

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Calcinosis universalis associated with dermatomyositis occurred in a 58-year-old woman. Tissues removed from the sublingual region in the patient were studied by ordinary microscopy, electron microscopy, and an electron-microanalytic method. The calcified materials were distributed on collagen fibers and seemed to have a relationship with foci of fibrinoid degeneration. Moreover, globular and/or membranous structures, considered to originate from the degenerate cells of the stroma, were observed in these calcified zones. Some of them contained electron-dense materials. Therefore, the globular and/or membranous structures were thought to be concerned with initial calcification in this case. Furthermore, irregular bone tissue was formed adjacent to the calcified masses. In addition, the calcified materials were identified by X-ray diffraction examination and electron microscopy as hydroxyapatite.

The root canal filling material "Vitapex" (Neo Dental Chemical Products Co., Tokyo), made of calcium hydroxide and iodoform with the addition of silicone oil, was experimentally injected into the mandibular canals of dogs, and its effect on the alveolar nerve tissue was examined by light and electron microscopy. No change was observed as long as the injected paste did not come into direct contact with the nerve, but tissue damage was found at sites of direct contact. After removal of degenerated nerve debris by macrophages and Schwann cells, the persisting external membranes or "Schwann tubes" appeared to provide a scaffolding for axonal regeneration and Schwann cell proliferation.