| Summary: | 碩士 === 國立成功大學 === 機械工程學系碩博士班 === 101 === The purpose of this study is to examine the time-dependent (viscoelastic) mechanical behaviors of different dental composites through both static and dynamic mechanical analyses, and to use Finite element method (FEM) to simulate the condition of mechanical behavior of tooth under external force.
In the process of this study, four types of commercial dental composite resin were chosen to examine: a nanocomposite, Z350 Flowable; a hybrid composite, Z250; a packable composite, P60; and a low-shrinkage composite, LS. Each one of them was divided into two experimental groups: 5-min (after curing about 5 min) and 30-day (stored in artificial saliva at 37℃ in incubator for 30 days). The experimental process includes three parts. First part emphasizes on using static test (creep ＆ recovery) to measure time-dependent mechanical properties of dental composite resin. Second part is to measure time-dependent mechanical properties of dental composite resin by dynamic test, and through TTSP, producing the viscoelastic master curve. The final part study applies finite element software to validate the responses of dental composite resin which are the outcomes of my first and second part examinations. Additionally, I also established a three-dimensional tooth model in this part of study in order to contrast the discrepancy between elastic and viscoelastic behaviors.
The results of the static test presented that the value of creep compliance of LS in 5-min group was minimum, which is similar to its result in the 30-day group. However, the values of creep compliance of the other dental composite resins in 5-min group are smaller than their outcomes in 30-day group. Doubtlessly, these four different dental composite resins can be admitted to be the linear viscoelastic materials in this study (the order of the creep compliance is: Z350 flow 〉 P60 ≈ Z250 〉 LS). In my dynamic test, the storage modulus in 5-min group showed that the values of modulus increase when temperature reached 50 to 60 °C, and value of loss tangent also increases at 50°C. But this phenomenon did not appear in 30-day group.
Finally, by the contrast of creep compliance which were measured through FEM calculation and DIC method, my experimental conclusion is consistent to the 30-day model. Nonetheless, it mismatches the 5-min model. Thus, this study only focuses on the material properties in 30-day group to proceeds the FEM simulation. The LS model was shown that enamel and resin have the maximum value of Von-Mises stress than other dental composite resin models.
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