Meira Josete B C, Braga Roberto R, de Carvalho Ana Carolina P, Rodrigues Flávia P, Xavier Tathy A, Ballester Rafael Y
Department of Dental Materials, School of Dentistry, University of São Paulo, São Paulo, SP, Brazil.
J Adhes Dent. 2007 Dec;9(6):499-503.
Using finite element analysis (FEA), to determine the nominal shrinkage stress of a composite under different restriction conditions defined by the longitudinal compliance (LC) and C-factor (C) of the testing system, and by the elastic modulus of the bonding substrate (E).
Eight axisymmetric models representing an experimental setup used to determine composite shrinkage stress were simulated. Composite thicknesses of 0.5 mm and 4 mm were tested, defining different C and volumes (C = 6 and vol = 14 mm3 or C = 0.8 and vol = 113 mm3, respectively). The E of the substrate was tested in two levels, 12 GPa and 207 GPa. Two LC values (1 x 10(-6) or 28 x 10(-6) mm/N) were defined for each E value by varying the length of the rods used as bonding substrate (0.3 mm and 9.5 mm for E = 12 GPa; 6.0 mm and 163.9 mm for E = 207 GPa). Materials were considered elastic, homogeneous, and isotropic. Shrinkage was simulated by thermal analogy. Nominal stress (nodal force/cross-sectional area) was calculated for each condition. Results were analyzed using Taguchi's method.
Nominal stress values varied between 1.7 MPa and 30.3 MPa. The main variables were statistically significant (LC: p = 0.0046; C: p = 0.0153; E: p = 0.0155), as well as the LC x E interaction (p = 0.0354). Stress reduction between low and high LC was more pronounced for E = 207 GPa compared to E = 12 GPa. Stress was lower for the high C conditions for both compliance levels.
Not only the C-factor of the testing assembly, but also its LC and the E of the bonding substrate influence stresses generated by composite shrinkage.
使用有限元分析（FEA），确定在由测试系统的纵向柔度（LC）和C因子（C）以及粘结基底的弹性模量（E）所定义的不同限制条件下，复合材料的名义收缩应力。
模拟了八个代表用于确定复合材料收缩应力的实验装置的轴对称模型。测试了0.5毫米和4毫米的复合材料厚度，分别定义了不同的C和体积（C = 6且体积 = 14立方毫米或C = 0.8且体积 = 113立方毫米）。基底的E在两个水平上进行测试，12吉帕和207吉帕。通过改变用作粘结基底的杆的长度（E = 12吉帕时为0.3毫米和9.5毫米；E = 207吉帕时为6.0毫米和163.9毫米），为每个E值定义了两个LC值（1×10⁻⁶或28×10⁻⁶毫米/牛顿）。材料被视为弹性、均匀且各向同性的。通过热模拟来模拟收缩。计算每种条件下的名义应力（节点力/横截面积）。使用田口方法分析结果。
名义应力值在1.7兆帕至30.3兆帕之间变化。主要变量具有统计学意义（LC：p = 0.0046；C：p = 0.0153；E：p = 0.0155），以及LC×E相互作用（p = 0.0354）。与E = 12吉帕相比，E = 207吉帕时低LC和高LC之间的应力降低更为明显。对于两种柔度水平，高C条件下的应力较低。
不仅测试组件的C因子，而且其LC以及粘结基底的E都会影响复合材料收缩产生的应力。
