Curtis Andrew R, Palin William M, Fleming Garry J P, Shortall Adrian C C, Marquis Peter M
Biomaterials Unit, School of Dentistry, University of Birmingham, St. Chads Queensway, Birmingham B4 6NN, UK.
Dent Mater. 2009 Feb;25(2):180-7. doi: 10.1016/j.dental.2008.05.013. Epub 2008 Jul 24.
To assess the mechanical properties of discrete filler particles representative of several inorganic fillers in modern dental resin-based composites (RBCs) and to assess the validity of a novel micromanipulation technique.
RBCs with microhybrid (Filtek Z250), 'nanohybrid' (Grandio) and 'nanofilled' (Filtek Supreme), filler particle morphologies were investigated. Filler particles were provided by the manufacturer or separated from the unpolymerized resin using a dissolution technique. Filler particles (n=30) were subjected to compression using a micromanipulation technique between a descending glass probe and a glass slide. The number of distinct fractures particles underwent was determined from force/displacement and stress/deformation curves and the force at fracture and pseudo-modulus of stress was calculated.
Agglomerated fillers ('nanoclusters') exhibited up to four distinct fractures, while spheroidal and irregular particles underwent either a single fracture or did not fracture following micromanipulation. Z-tests highlighted failure of nanoclusters to be significant compared with spheroidal and irregular particles (P<0.05). The mean force at first fracture of the nanoclusters was greater (1702+/-909 microN) than spheroidal and irregular particles (1389+/-1342 and 1356+/-1093 microN, respectively). Likewise, the initial pseudo-modulus of stress of nanoclusters (797+/-555 MPa) was also greater than spheroidal (587+/-439 MPa) or irregular (552+/-275 MPa) fillers.
The validity of employing the micromanipulation technique to determine the mechanical properties of filler particulates was established. The 'nanoclusters' exhibited a greater tendency to multiple fractures compared with conventional fillers and possessed a comparatively higher variability of pseudo-modulus and load prior to and at fracture, which may modify the damage tolerance of the overall RBC system.
评估现代牙科树脂基复合材料（RBCs）中几种无机填料的离散填料颗粒的力学性能，并评估一种新型微操纵技术的有效性。
研究了具有微混合（Filtek Z250）、“纳米混合”（Grandio）和“纳米填充”（Filtek Supreme）填料颗粒形态的RBCs。填料颗粒由制造商提供，或使用溶解技术从未聚合的树脂中分离出来。使用微操纵技术在下降的玻璃探针和载玻片之间对30个填料颗粒进行压缩。根据力/位移和应力/变形曲线确定颗粒经历的不同断裂次数，并计算断裂时的力和应力假模量。
团聚填料（“纳米团簇”）表现出多达四次不同的断裂，而球形和不规则颗粒在微操纵后要么发生单次断裂，要么未发生断裂。Z检验表明，与球形和不规则颗粒相比，纳米团簇的断裂不显著（P<0.05）。纳米团簇首次断裂时的平均力（1702±909 μN）大于球形和不规则颗粒（分别为1389±1342和1356±1093 μN）。同样，纳米团簇的初始应力假模量（797±555 MPa）也大于球形填料（587±439 MPa）或不规则填料（552±275 MPa）。
确定了采用微操纵技术测定填料颗粒力学性能的有效性。与传统填料相比，“纳米团簇”表现出更大的多次断裂倾向，并且在断裂前和断裂时具有相对较高的假模量和载荷变异性，这可能会改变整个RBC系统的损伤耐受性。
