Apexification に伴う歯根膜の創傷治癒に関する実験的研究

Abstract

Immature permanent teeth of young dogs were given apexification with use of preparation of calcium hydroxide iodoform and healing of wound of periodontal membrane was investigated radiologically, photographically, histopathologically, and scanning electron microscopically. The results were as follows : 1. From 7th to 14th day after operation, Hertwig epithelial sheaths were observed in the apical portion in the control group. In the experimental group, Hertwig epithelial sheaths were directed toward outer periodontium, detached and necrosed. On the periodontium side of the Hertwig epithelial sheaths, large cementoblasts appeared and calcification of lightly eosin-stained cementum began. 2. From 1 to 2 months, findings of formation of cellular cementum were observed in the control group. In the experimental group, large and tall cementoblasts amassed densely on the periodontium where Hertwig epithelial sheaths necrosed. Between cells, collagen fibers were abundant and periodontium fibers directly below the apical portion ran monotonously and were begining to be compact. 3. At 4th month, bundles of Sharpey fibers connecting cellular cementum and the alveolar bone were observed in the control group. In the experimental group at this stage, early stage of formation of cementum-like hard tissue stained well with Hema-toxylin was observed in the periodontal membrane directly below the central apical portion and continuous cementum-like hard tissue was observed at the apical portion. 4. At 6th month, radiologically and photographically, cementum at the apical portion showed high densitometric curves in microphotograms in the control group. In the experimental group, radioopaque images were seen scattered as if they were to from closure and very irregular densitometric curves were shown in microphotograms. In photographic density also, the values were lower than those of the control group. Histopathologically, the control group showed several branches in the cementum at the apical portion. The experimental group showed coarse cementum-like hard tissue in the whole apical portion, and necrosed tissue, drug, and fibers were found scattered inside the tissue. Electron microscopically, cementum was formed extensively and presented many even surfaces in the control group. In the experimental group, cementum lacunae of various sizes were seen and the border of margins were indistinguishable. However, even cementum surfaces were formed in places. Globular structures evidencing calcification were also observed and matrix fibers were seen among them. 5. At 7th and 8th month, the control group showed about the same findings as those seen at 6th month radiologically and photographically. In the experimental group, photographic density also approached that of the control group. Histopathologically, formation of cementum of the apical portion progressed in the control group and cementum lacunae and branch-like structures were observed inside the apical portion in the experimental group. Electron microscopically, calcified cementum globules amassed and formed smooth even surfaces in the control group and the border of the margins became clearer than those at 6th month and cement canaliculi were also observed in the experimental group.