異なる合着システムを用いて修復した根管治療歯の垂直歯根破折抵抗とクラック形成の検討

Vertical root fracture resistance and crack formation of root canal-treated teeth restored with different post-luting systems.

抄録

根管治療を施した歯の垂直歯根破折（VRF）抵抗性とクラック形成について，異なるポストリューティングシステムを用いて検討することを目的とした．同程度の大きさのヒト上顎側切歯に装飾を施し，5群に分け（n=18，power=0.9），人工歯根膜付きアクリルブロックに埋没させた．根管充填後，同形同大のFRC（Fiber Reinforced Composite）またはTi（Sand Blasted Titanium）ポストを設置するためのポストスペースを作製した．ポストの半分はリン酸亜鉛セメント（C），残りの半分は接着剤によるルーテイング（A）．未処置の歯が対照となった．咀嚼シミュレータで熱サイクルおよび階段荷重を負荷した後，根面象牙質表面のクラック形成を顕微鏡で観察し，無欠陥，クレーズライン，垂直クラック，水平クラックに分類した．その後，歯根が破折するまで荷重をかけた．データは，一元配置分散分析，Tukeyの検定，およびFisherの正確検定によって解析した．すべての試料はVRFを用いない咀嚼シミュレーションに耐えたが，亀裂形成は群間で有意差があった（P=0.009）．コントロールはFRC/C，Ti/C，Ti/Aよりも有意に欠陥が少なかった（それぞれP=0.001，P=0.008，P=0.008)．FRC/Cは垂直クラックの発生率が最も高かった．FRC/Aは欠陥の発生率が最も低かった．VRF耐性は両群間に有意差はなかった（P=0.265）。接着剤入りFRC柱は耐VRF性を向上させないが、欠陥のリスクを低減させた。欠陥の多くはクレーズラインと垂直ルートクラックであった．

The aim was to investigate the vertical root fracture (VRF) resistance and crack formation of root canal-treated teeth restored with different post-luting systems. Human maxillary lateral incisors of similar size were decoronated, assigned to five groups (n = 18, power = 0.9) and embedded in acrylic blocks with artificial periodontal ligament. After root canal filling, post spaces were prepared to place coated fiber-reinforced composite (FRC) or sandblasted titanium (Ti) posts of the same shape and size. Half of the posts were zinc phosphate cemented (C), while the other half was adhesively luted (A). Untreated teeth served as control. After thermal cycling and staircase loading in a chewing simulator, the crack formation on the root dentin surface was microscopically examined and classified as no defect, craze line, vertical crack, and horizontal crack. Subsequently, the samples were loaded until root fracture. Data were analyzed by one-way ANOVA, Tukey's test, and Fisher's exact test. All samples survived the chewing simulation without VRF, but crack formation was significantly different between the groups (P = 0.009). The control showed significantly fewer defects than FRC/C, Ti/C, and Ti/A (P = 0.001, P = 0.008, P = 0.008, respectively). FRC/C showed the highest incidence of vertical cracks. FRC/A had the lowest incidence of defects. There was no significant difference in VRF resistance between the groups (P = 0.265). Adhesively luted FRC posts did not increase VRF resistance but reduced the risk of defects. Most defects were craze lines and vertical root cracks.