ファイバーポストの長さが歯内療法歯の破折強さに及ぼす影響

Influence of the Fiber Post Length on the Fracture Strength of Endodontically Treated Teeth.

抄録

ファイバーポストは歯内療法治療歯の修復に広く使用されているが，根管内への理想的なセメント埋入深さについては，文献的にまだ議論がある．本研究の目的は，ファイバーポストの根管内挿入長の違いがETTの破折強度に影響するかどうかを評価することである． 歯周治療のために抜歯した長さと量が同程度の直根のヒト永久歯下切歯10本を、セメントエナメル接合部（CEJ）から2 mm上方で全長18 mmに切断し、同じ方法で歯内療法を行った後、無作為に5本ずつ2群に分けた（第1群と第2群、＝5）。歯内療法を行っていない健全な切歯2本を対照群とした（グループ3、＝2）。湿度の高い環境で1週間保管した後、最初の2群にファイバーポストNo.1（Reforpost、Angelus、Londrina、PR、ブラジル）のためのスペースを深さ5mm（グループ1）と7mm（グループ2）に準備し、ファイバーポストを自己接着性レジンセメント（Maxcem Elite、Kerr GmbH、Herzogenrath、ドイツ）を用いて接着固定した。7日後、試料をCEJレベルより2mm下まで、自己硬化性透明アクリル樹脂中に垂直に位置決め固定し、さらに1週間保存した後、各試料の破折まで変位制御試験機を用いて機械的圧縮試験を行った。各試料の荷重-変位曲線が記録され、各群の平均値が算出され、群間の統計的比較分析が行われた。 グループ間に統計学的な有意差は認められなかったが、健全な非処置歯（1045.69±146.19）と比較しても、グループ1（985.09±330.28）と比較して、グループ2（1099.41±481.89）で最も高い平均破壊力（N）が記録された。 この in vitro 試験の限界の範囲内で、ファイバーポストを根管に深く埋入した歯（7 mm）では、短い長さ（5 mm）と比較して、わずかに高い破折力が記録された。しかし、機械的試験で得られた同様の生体力学的性能は、7 mmと5 mmの挿入ポストの間に統計的な差は見られなかった。

Although fiber posts are widely used in the restoration of endodontically treated teeth (ETT), their ideal cementation depth into the root canal is still debated in literature. The aim of the present study was to evaluate whether the different intra-radicular insertion lengths of the fiber posts influence the fracture strength of ETT. A total of 10 permanent human lower incisors with straight roots of similar length and volume extracted for periodontal reason were sectioned 2 mm above the cement-enamel junction (CEJ) to a total length of 18 mm and endodontically treated in the same manner, then randomly divided into two groups of five each (Groups 1 and 2, = 5). Two sound incisors, with no endodontic treatment, were used as the control group (Group 3, = 2). After one week of storage in a humid environment, spaces for fiber post no. 1 (Reforpost, Angelus, Londrina, PR, Brazil) were prepared in the first two groups at a depth of 5 mm (Group 1) and 7 mm (Group 2), and the fiber posts were adhesively cemented using self-adhesive resin cement (Maxcem Elite, Kerr GmbH, Herzogenrath, Germany). After 7 days, the samples were vertically positioned and fixed in a self-curing transparent acrylic resin, up to 2 mm below the CEJ level, and mechanically tested in compression after another week of storage using a displacement-controlled testing machine up to each sample's fracture. The force-displacement curves were recorded for each sample, the means were calculated for each group and a statistical comparative analysis between groups was conducted. Although no statistically significant differences between groups were observed, the highest mean fracture force (N) was recorded in Group 2 (1099.41 ± 481.89) in comparison to Group 1 (985.09 ± 330.28), even when compared to the sound, non-treated teeth (1045.69 ± 146.19). Within the limitations of this in vitro study, teeth where fiber posts were placed deeper into the root canal (7 mm) recorded slightly higher fracture forces in comparison with shorter lengths (5 mm). However, similar biomechanical performances obtained in the mechanical tests showed no statistical differences between the 7 mm and the 5 mm inserted posts.