J Adhes Dent. 2023 Apr 25;25:99-106. doi: 10.3290/j.jad.b4051477.
To assess the mechanical performance and enamel-crack propensity of large MOD composite-resin restorations on maxillary molars with severely undermined cusps.
Thirty-six extracted maxillary third molars (n = 12) received a standardized slot-type MOD preparation (5-mm depth by 5-mm bucco-palatal width) with severe undercuts, leaving unsupported buccal and lingual enamel cusps. A short-fiber reinforced composite resin base (SFRC, everX Flow, GC) was used for both the experimental direct approach and semi-direct CAD/CAM inlays (Cerasmart 270, GC). In the control group using a direct approach, Gradia Direct (GC) composite resin was used alone without SFRC. Optibond FL (Kerr) adhesive was used in all three groups (also for the immediate dentin sealing of inlays). Artificial masticatory forces were simulated under water using closed-loop servo-hydraulics (MTS Acumen 3). Each specimen was mounted at a 30-degree angle and positioned so that a cylindrical antagonistic cusp (actuator) contacted the internal palatal cusp slope of the restoration. Cyclic loading was applied at a frequency of 5 Hz, starting with a load of 200 N, increasing by 100 N every 2000 cycles. Samples were loaded until fracture and the number of endured cycles and failure modes of each specimen was recorded. Each sample was also evaluated for crack propensity during the experiment and for final failure mode (reparable failures above the CEJ [cementoenamel junction] vs irreparable failures below the CEJ).
Shrinkage-induced cracks (>3 mm) were found in most specimens for both direct groups (66% to 83%) but not with inlays. The survival of inlays with a SFRC base was superior to that of the direct SFRC restorations and Gradia Direct (control) restorations (Kaplan-Meier survival analysis and post-hoc log-rank test p < 0.000). The direct control group without SFRC exhibited not only the poorest survival but also 100% catastrophic failure (vs 42% and 17% for SFRC direct and SFRC inlays, respectively).
Large MOD restorations with severely undermined cusps were most favorably restored with an SFRC base and a CAD/CAM inlay, yielding the highest survival rate, more reparable failures and absence of shrinkage-induced cracks. When a low-cost restoration must be chosen, the SFRC base will significantly improve the performance and failure mode of directly layered restorations.
评估上颌磨牙严重牙尖下凹的 MOD 复合树脂大嵌体的机械性能和釉裂倾向。
36 颗离体上颌第三磨牙（n=12）接受标准化的槽型 MOD 预备（5mm 深，5mm 颊舌向宽度），伴有严重的牙尖下凹，颊舌向无支持的牙釉质牙尖。使用短纤维增强复合树脂基底（SFRC，everX Flow，GC）进行实验直接法和半直接 CAD/CAM 嵌体（Cerasmart 270，GC）。在直接法的对照组中，单独使用 Gradia Direct（GC）复合树脂，不使用 SFRC。在所有三组中均使用 Optibond FL（Kerr）胶粘剂（也用于嵌体的即刻牙本质密封）。在闭环伺服液压（MTS Acumen 3）下在水下模拟人工咀嚼力。每个标本以 30 度的角度安装，并定位为使圆柱形拮抗牙尖（致动器）接触修复体的内部腭牙尖斜面。以 5Hz 的频率施加循环载荷，起始载荷为 200N，每 2000 次循环增加 100N。加载直至断裂，并记录每个标本的循环次数和失效模式。在实验过程中，每个样本还评估了裂纹倾向，并对最终失效模式（CEJ[牙骨质-釉质交界]以上的可修复性失效与 CEJ 以下的不可修复性失效）进行评估。
直接组的大多数标本都出现了收缩诱导裂纹（>3mm）（66%至 83%），但嵌体组没有。SFRC 基底的嵌体的存活率优于直接 SFRC 修复体和 Gradia Direct（对照）修复体（Kaplan-Meier 生存分析和事后对数秩检验 p<0.000）。无 SFRC 的直接对照组不仅存活率最差，而且 100%发生灾难性失效（SFRC 直接和 SFRC 嵌体组分别为 42%和 17%）。
对于严重牙尖下凹的大 MOD 修复体，使用 SFRC 基底和 CAD/CAM 嵌体修复效果最佳，存活率最高，可修复性失效更多，且无收缩诱导裂纹。当必须选择低成本修复体时，SFRC 基底将显著改善直接分层修复体的性能和失效模式。
