Elkaffass Ali-Atef, Eltoukhy Radwa-Ibrahim, Elnegoly Salwa-Abd-Elraof, Mahmoud Salah-Hassab
Assistant Lecturer, Operative Dentistry Dept, Faculty of Dentistry, Mansoura University, Egypt.
Clinical Assistant Professor, Operative Dentistry Dept, Faculty of Dentistry, Mansoura University, Egypt.
J Clin Exp Dent. 2020 May 1;12(5):e494-e500. doi: 10.4317/jced.56469. eCollection 2020 May.
Resin composite preheating is an innovative method that could be clinically beneficial by improving the handling properties, marginal adaptation, and surface properties of uncured nanofilled resin composite materials. There is conflict and unclear information regarding the effect of preheating on the microhardness, fracture toughness and surface roughness of nanofilled resin composites. Thus, it is important to assess whether dental clinicians can adopt preheating procedures without compromising composite mechanical strength. Objective: The purpose of this study was to evaluate the effect of preheating on microhardness, fracture toughness and surface roughness of nanofilled resin composite.
In this study, one commercial nanofilled resin composite Filtek Z350 XT was used. A total of 28 disc-shaped specimens were fabricated in a Teflon mold (10 mm diameter x 2 mm thick) for Vickers microhardness indentation test and surface roughness test. The samples were divided into two groups of 14 samples each, one group of samples was light-cured at room temperature (24ºC) without preheating (non-heated group), and the other group was light-cured after preheating (preheated group). Vickers hardness measurements of 14 specimens (n=7) either preheated or non-heated of the top and bottom surfaces was measured by means of microhardness tester by applying 100 g load for 10 s. Surface Roughness measurements (Ra) were obtained from 14 specimens (n=7) either preheated or non-heated with the atomic force microscope. Fourteen single-edge-notched-beam specimens were prepared for fracture toughness test (n=7) either preheated or non-heated with measurements (2.5 x 5 x 25 mm3) and a crack 2.12 mm in length. The specimens were tested via three-point bending mode, using a universal testing machine at crosshead speed of 1.0 mm/min until failure occurred.
Independent sample t- tests revealed no significant difference between non-heated and preheated groups for all tests (>0.05). However, for Vickers hardness test, there were significant differences between top and bottom surfaces for non-heated and preheated groups (<0.05). Moreover, surface roughness average Ra (nm) mean values of preheated group was higher than non-heated group but no significant difference between them was found (>0.05).
Preheating procedure did not negatively affect microhardness, fracture toughness and surface roughness of nanofilled resin composites so preheating is recommended for the other potential clinical advantages. Preheating, nanofilled composites, microhardness, fracture toughness, surface roughness.
树脂复合材料预热是一种创新方法，通过改善未固化纳米填充树脂复合材料的操作性能、边缘适应性和表面性能，可能在临床上带来益处。关于预热对纳米填充树脂复合材料的显微硬度、断裂韧性和表面粗糙度的影响，存在相互矛盾且不明确的信息。因此，评估牙科临床医生能否在不损害复合材料机械强度的情况下采用预热程序很重要。目的：本研究的目的是评估预热对纳米填充树脂复合材料的显微硬度、断裂韧性和表面粗糙度的影响。
在本研究中，使用了一种商用纳米填充树脂复合材料Filtek Z350 XT。在聚四氟乙烯模具（直径10mm×厚2mm）中制备了总共28个圆盘形试样，用于维氏显微硬度压痕试验和表面粗糙度试验。将样品分为两组，每组14个样品，一组样品在室温（24℃）下不预热进行光固化（未加热组），另一组在预热后进行光固化（预热组）。通过显微硬度计，对14个预热或未预热试样（n = 7）的顶面和底面施加100g载荷10s，测量维氏硬度。用原子力显微镜从14个预热或未预热试样（n = 7）中获得表面粗糙度测量值（Ra）。制备了14个单边切口梁试样用于断裂韧性试验（n = 7），试样尺寸为（2.5×5×25mm3），裂纹长度为2.12mm，预热或未预热。通过三点弯曲模式，使用万能试验机以1.0mm/min的十字头速度对试样进行测试，直至发生破坏。
独立样本t检验显示，所有测试中未加热组和预热组之间无显著差异（>0.05）。然而，对于维氏硬度试验，未加热组和预热组的顶面和底面之间存在显著差异（<0.05）。此外，预热组的表面粗糙度平均Ra（nm）平均值高于未加热组，但两者之间未发现显著差异（>0.05）。
预热程序对纳米填充树脂复合材料的显微硬度、断裂韧性和表面粗糙度没有负面影响，因此鉴于其他潜在的临床优势，建议进行预热。预热、纳米填充复合材料、显微硬度、断裂韧性、表面粗糙度。
