歯内療法で治療した咬合面側空洞を有する小臼歯の破壊抵抗および破壊様式に及ぼす最終修復物の種類の影響

Influence of type of final restoration on the fracture resistance and fracture mode of endodontically treated premolars with occluso-mesial cavities.

抄録

はじめに:

本研究の目的は、歯内療法を受けた小臼歯に3種類の修復材（直接複合材、間接複合材、CAD/CAMセラミックインレー）を適用して保存的な咬合性中空部を修復した後の破壊抵抗を比較することである。

Introduction: The aim of this study was to compare the fracture resistance of endodontically treated premolars after the application of three restorative materials (i.e., direct composite, indirect composite, and computer aided design/computer aided manufacturing CAD/CAM ceramic inlays) to restore a conservative occluso-mesial cavity preparation.

材料と方法:

60本の健全な上顎前歯を4つの実験群に分けた。A群：根管治療も前処理も行わないコントロール群、B群：歯を直接Filtek Z250コンポジット修復材で修復した群、C群：歯を間接インレーFiltek Z250コンポジット修復材で修復した群、D群：歯をIPS E.Max CAD/CAMモノリシックセラミックインレーで修復した群。虫歯の治療と根管治療は標準的な手法で行われた。その後、メーカーの指示に従い、ダイレクトコンポジット修復材を用いて修復を行った。各グループは，中・外腔の修復を受け，指定されたグループに従って修復を行った。すべてのグループの歯は，5～55℃のウォーターバスで500サイクルの熱サイクル処理を受けた。その後，コンピュータ制御のインストロン万能試験機の専用治具に各試料を取り付けた。口蓋骨に45°の角度で破損するまで軸方向の圧縮荷重をかけた。力は2mm/minの速度で，目に見える，あるいは音に聞こえる破壊の証拠が観察されるまで加えた。破断時の力はMPaで測定し，破断モードは好ましいもの（セメント・エナメル接合部（CEJ）より上での修復可能な接着性破断）と好ましくないもの（CEJより下での修復不可能な破断）のいずれかとして記録した。得られたデータは，統計ソフトSPSS version 21.0を用いて解析した。4群の最大荷重の平均値の比較には，一元配置分散分析とTukeyの検定を用いた。また，Pearson's Chi-square 検定を用いて，4つのグループの故障モードの分布を比較した。結果の統計的有意性の報告には，p値≦0.05を用いた。

Materials and methods: sixty sound maxillary premolars were divided into four experimental groups; group A: the control group, where neither root canal treatment nor preparation were performed; group B: teeth were restored with a direct Filtek Z250 composite restorative material; group C: teeth were restored with an indirect inlay Filtek Z250 composite restorative material; group D: teeth were restored with IPS E.Max CAD/CAM monolithic ceramic inlays. Access cavities and root canal treatment procedures were conducted using standard techniques. Then, the cavities were restored with direct composite restorative materials following manufacturer's instructions. Each group received mesial-occlusal cavities and restored according to the designated group.Teeth from all groups were exposed to a thermocycling regimen of 500 cycles in water baths at 5-55 °C. Then, each specimen was mounted on a special fixture on a computer controlled Instron Universal Testing Machine. An axial compressive load was applied to the palatal cusp up to failure at an angle of 45°. The force was applied at the rate of 2 mm/min until visible or audible evidence of fracture was observed. The force at fracture was measured in MPa, and the fracture mode was recorded as either favorable [restorable adhesive fracture above the cemento-enamel junction (CEJ)] or unfavorale (non-restorable fractures under CEJ). The obtained data were analyzed using the SPSS version 21.0 statistical software. One-way ANOVA and Tukey's test were used to compare the mean values of maximum load of the four groups. Pearson's Chi-square test was used to compare the distribution of failure mode among the four groups. The p-value of ≤ 0.05 was used to report the statistical significance of results.