Thesis or Dissertation 破歯細胞に関する形態学的研究:歯髄処置経験乳歯における核数の分布について

八木原, 澄

The root dentine of human deciduous tooth is physiologically resorbed by multinucleated odontoclasts. Previously, authors investigated the distribution of number of nuclei per human odontoclast and showed that the mean number of nuclei per cell is 5.3 and the median is 4. After endodontic treatments of human deciduous tooth, odontoblasts were removed and root canals were filled with material with alkaline calcium hydroxide. Therefore, the structure of root dentine after endodontic treatments is different from that before treatments. The present study aims to clarify the number of nuclei per odontoclast in human deciduous teeth after endodontic treatments with Vitapex®, a calcium hydroxide-based root canal filling material, and to compare it with that in human deciduous teeth without endodontic treatments. After extraction of deciduous teeth, they were fixed, decalcificated and embedded in paraffin, and six specimens were selected randomly. The specimens were serially sectioned into 4 ㎛-thick sections and they were stained with TRAP and methyl green, and sections were observed by light microscopy. TRAP-positive cells forming resorptive lacunae on the dentine were identified as odontoclasts, and 99 odontoclasts in anterior teeth and 101 cells in molar ones were investigated to determine the distribution of nuclei per cell. The mean number of nuclei per cell was 20.8 and the median was 14. In the distribution of number of nuclei per odontoclast, there were statistically significant differences between teeth with endodontic treatments and ones without them. These results suggest that the presence of calcium hydroxide-based root canal filling material and root dentine with different structure may cause change in number of nuclei of odontoclasts.
乳歯の生理的歯根吸収は多核巨細胞である破歯細胞によって行われる. 過去に著者らはヒト健全乳歯歯根を吸収する破歯細胞の核数を調査し, 平均値は5.3, 中央値は4であることを報告した. 乳歯の歯髄処置後, 象牙質に象牙芽細胞は存在せず, 根管内にはアルカリ性の水酸化カルシウム製剤が充填されるため, その歯根象牙質は正常象牙質とは異なる構造を持つ. そのため, 歯髄処置経験乳歯における破歯細胞の核数を明らかにすることは, 健全乳歯破歯細胞の核数と比較検討し, 歯髄処置の与える影響を考える上で重要である. 本研究は歯髄処置に着目し, 水酸化カルシウム系根管充填剤であるビタペックス®(ネオ製薬)にて歯髄処置後1年から1年10か月経過後に生理的交換期に達したヒト失活乳歯歯根吸収面にみられる破歯細胞の核数の分布を連続切片による観察から検索することを目的とした.乳歯を抜去後, 固定, 脱灰, パラフィン包埋後, TRAP陽性反応を示す20本の乳歯から乳前歯3本, 乳臼歯3本の合計6本の試料を無作為抽出した. 試料において4㎛厚の連続切片を作製し, TRAP・メチルグリーン染色後写真撮影を行った. 連続切片による観察から歯根象牙質上に吸収窩を形成しているTRAP陽性を示す破歯細胞に含まれる核数を計測した. 乳前歯99個, 乳臼歯101個の破歯細胞の核数について検索した結果, 平均値20.8, 中央値14であった. 本研究の結果とヒト健全乳歯の破歯細胞の核数の間には統計学的な有意差が認められた(p<0.01). これらの結果は水酸化カルシウム系根管充填剤の存在と歯髄処置による象牙質のpHおよび構造変化が破歯細胞の核数に影響を与えている可能性を示唆している.
Hokkaido University(北海道大学). 博士(歯学)

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