The ultrastructural aspects of initial calcification in the rat subcutaneous tissues elicited by the root canal filling material Vitapex, made up of calcium hydroxide and iodoform with the addition of silicone oil, were studied by means of electron microscopic and cytochemical techniques. The embedded paste caused heterotopic calcifications. These were divided into two types: dystrophic calcification and matrix vesicle calcification which resembled that of bone tissue. These data suggest that Vitapex may be an excellent root canal filling material for differentiation of osteoblasts or cementoblasts from mesenchymal cells in the periodontal ligament.
