Objective

A class of ultra-rapid-cure resin-based composites (RBCs) exhibited immediate post-irradiation surface viscoelastic integrity using an indentation-creep/recovery procedure. The aim of this study was to determine whether such behavior is more generally characteristic of a wider range of RBCs.

Methods

Eight representative RBCs were selected based on different clinical categories: three bulkfills (OBF, Filtek One Bulk Fill; VBF, Venus Bulkfill; EBF, Estelite Bulkfill), three conventional non-flowables (XTE, Filtek Supreme XTE; GSO, GrandioSo; HRZ, Harmonize) and conventional flowables (XTF, Filtek Supreme XTE Flow; GSF, GrandioSo Flow). Stainless steel split molds were used to fabricate cylindrical specimens (4 mm (dia) × 4 mm). These were irradiated (1.2 W/cm²) for 20 s on the top surface. Post-irradiation specimens (n = 3), within their molds, were centrally loaded with a flat-ended 1.5 mm diameter indenter under 14 MPa stress: either immediately (<2 min) or after 24 h delayed indentation. Stress was maintained for 2 h, then – after removal – recovery measurements continued for a further 2 h. Indentation depth (%) versus time was measured continuously to an accuracy of <0.1 μm. Data were analyzed by One-way ANOVA and Tukey post-hoc tests (α = 0.05).

Results

Time-dependent viscoelastic indentation was observed for all RBCs. For immediate indentation, the maximum indentation range was 1.43–4.92%, versus 0.70–2.22% for 24 h delayed indentation. Following 2 h recovery, the residual indentation range was 0.86–3.58% after immediate indentation, reducing to 0.22–1.27% for delayed indentation. The greatest immediate indentation was shown by VBF followed by XTF and GSF. OBF, HRZ, XTE and GSO had significantly lower indentations (greater hardness). XTE showed a significantly reduced indentation maximum compared to OBF (p < 0.05). Indentations delayed until 24 h post-irradiation were reduced (p < 0.05) for most materials.

Significance

The indentation-creep methodology effectively characterized resin-based composites within several categories. Viscoelastic properties evaluated by the indentation-creep method confirmed that highly filled RBCs were more resistant to indentation. Indentations were reduced after 24 h post-irradiation due to further matrix-network development.

中文翻译：

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光聚合树脂基复合材料的辐照后表面粘弹性完整性

客观的

一类超快速固化树脂基复合材料 (RBC) 使用压痕蠕变/恢复程序在辐照后立即显示出表面粘弹性完整性。本研究的目的是确定这种行为是否是更广泛的红细胞的普遍特征。

方法

根据不同的临床类别选择了八种具有代表性的红细胞：三种散装（OBF，Filtek One Bulk Fill；VBF，Venus Bulkfill；EBF，Estelite Bulkfill），三种常规非流动剂（XTE，Filtek Supreme XTE；GSO，GrandioSo；HRZ， Harmonize）和传统的流动性（XTF、Filtek Supreme XTE Flow；GSF、GrandioSo Flow）。不锈钢对开模具用于制造圆柱形试样（4 毫米（直径） ×  4 毫米）。这些被辐照 (1.2  W/cm ² ) 20 s 在上表面。辐照后样品 (n  =  3) 在其模具内， 在 14  MPa 应力下集中加载直径为1.5 mm的平压头：立即（<2 分钟）或延迟24 小时后压痕。应力保持 2小时，然后——在移除后——恢复测量再继续进行 2小时。连续测量压痕深度 (%)与时间的关系，精度 <0.1 μm。数据通过单向方差分析和 Tukey事后检验 ( α = 0.05) 进行分析。     

结果

所有红细胞均观察到时间依赖性粘弹性压痕。对于立即压痕，最大压痕范围为 1.43-4.92%，而24 小时延迟压痕的最大压痕范围为 0.70-2.22% 。 恢复2小时后，立即压痕后的残余压痕范围为 0.86-3.58%，延迟压痕则降至 0.22-1.27% 。最大的直接缩进显示为 VBF，其次是 XTF 和 GSF。OBF、HRZ、XTE 和 GSO 的压痕显着降低（更大的硬度）。与 OBF 相比，XTE 的压痕最大值显着降低（p  <  0.05）。缩进延迟大多数材料 的辐照后24小时减少（p  <  0.05）。

意义

压痕-蠕变方法有效地表征了几个类别中的树脂基复合材料。通过压痕-蠕变方法评估的粘弹性证实高度填充的红细胞更耐压痕。 由于进一步的基质网络发展，在辐照后 24小时后压痕减少。