エナメル質に接着した間接材料の破壊荷重と剪断接着強さの経時変化

Failure load and shear bond strength of indirect materials bonded to enamel after aging.

抄録

本研究では，歯科用ベニアのCAD/CAMに使用される4種類のブロック材料（二ケイ酸リチウム，長石セラミック，ポリマー包埋セラミック，ナノハイブリッドコンポジット）の破壊荷重とせん断接着強さを評価した．試験された仮説は、エナメル質に類似した弾性率と最も高い接着強度を併せ持つ材料が、最も高い破壊荷重を示すというものであった。プレハブCAD/CAMブロックから、円盤状試験片（6.0×0.7 mm；n=10）および円柱状試験片（2.4×2.5 mm；n=10）を作製し、それぞれ破壊荷重試験およびせん断接着強さ試験を行った。材料は平坦化した牛エナメル質表面に接着し、蒸留水中で37℃、90日間保存した後、サーモサイクル（5℃～55℃を2000サイクル）に供した。修復材料のディスクをエナメル質に接着し、破局的破壊が起こるまで、接着界面に垂直に加えられる荷重を増加させた。剪断接着強さを測定するために、チゼルを用いてエナメル質と円柱状の修復材料との接着界面に平行に荷重を増加させた。データは、ワイブル分析および一元配置分散分析の後、Tukey post hoc test (α = 0.05)を行った。修復材料の種類は、エナメル質に接着した際の（平均［SD］）破壊荷重に有意に影響した（P = 0.006）：ポリマー包埋セラミック（1167.9［310.2］N）＝長石質セラミック（1115.0［382.0］N）＝ナノハイブリッドコンポジット（1067.3［251.0］N）＞二ケイ酸リチウム（786.2［304.5］N）。二ケイ酸リチウム(32.81 [11.19] MPa) = ポリマー包埋セラミック(27.04 [7.65] MPa) > 長石質セラミック(21.11 [9.16] MPa) > ナノハイブリッドコンポジット(9.08 [3.66] MPa)。エナメル質に接着した場合、ポリマー包埋セラミックが最も優れた性能を示した。

This study evaluated the failure load and the shear bond strength of 4 block materials indicated for computer-aided design/computer-aided manufacturing (CAD/CAM) of dental veneers: lithium disilicate, feldspathic ceramic, polymer-infiltrated ceramic, and nanohybrid composite. The tested hypothesis was that the material that combined an elastic modulus similar to that of enamel with the highest bond strength values would present the highest failure load. From prefabricated CAD/CAM blocks, disc-shaped specimens (6.0 × 0.7 mm; n = 10) and cylinders (2.4 × 2.5 mm; n = 10) were fabricated for load-to-failure and shear bond strength tests, respectively. Materials were adhesively bonded to flattened bovine enamel surfaces, stored in distilled water at 37°C for 90 days, and subjected to thermocycling (2000 cycles of 5°C to 55°C). Discs of restorative material were bonded to enamel and subjected to an increasing load that was applied perpendicular to the bonding interface until catastrophic failure occurred. A chisel was used to apply an increasing load parallel to the adhesive interface between the enamel and a cylinder of restorative material to measure shear bond strength. Data were subjected to a Weibull analysis and 1-way analysis of variance followed by a Tukey post hoc test (α = 0.05). The type of restorative material significantly affected the (mean [SD]) failure load when bonded to enamel (P = 0.006): polymer-infiltrated ceramic (1167.9 [310.2] N) = feldspathic ceramic (1115.0 [382.0] N) = nanohybrid composite (1067.3 [251.0] N) > lithium disilicate (786.2 [304.5] N). The type of restorative material also significantly affected the (mean [SD]) bond strength to enamel (P < 0.001): lithium disilicate (32.81 [11.19] MPa) = polymer-infiltrated ceramic (27.04 [7.65] MPa) > feldspathic ceramic (21.11 [9.16] MPa) > nanohybrid composite (9.08 [3.66] MPa). The polymer-infiltrated ceramic presented the best performance when bonded to enamel.