本研究目的為探討不同類型的牙科複合樹脂之黏彈性行為並使用有限元素法(FEM)模擬受外力作用下的力學行為。
本實驗選取4種不同性質牙科複合樹脂商品：抗壓型複合樹脂(P60)、混合填料複合樹脂 (Z250)、奈米填料複合樹脂(Z350 flow)與低收縮的複合樹脂(LS)。每種樹脂都分為兩組:在固化後5分鐘與存放於37℃人工唾液30天後進行實驗。第一部分實驗為靜態的潛變與潛變恢復實驗，透過數位影像相關法計算出樹脂受力時的應變、柏松比(Poisson’s ratio) 和判斷材料的依時特性是否為線性關係。第二部分使用動態機械分析儀量測材料的儲存模數(Storage modulus)，並透過時間-溫度重疊原理(TTSP)建立黏彈性力學中的主曲線(Master curve)。最後一部分是使用有限元素軟體把由第二部分實驗中所建立的主曲線當代入模型中計算並與第一部分靜態實驗所量測到的潛變柔度進行驗證，另外再建立三維的第五類齲齒(Class-V)牙齒模型預測其受力時的力學行為。
在固化後5分鐘的結果顯示LS的潛變柔度較其他3種複合樹脂來的小。在存放30天後進行實驗的潛變柔度結果顯示除了LS外的3種樹脂都比在固化後5分鐘實驗所量測到的結果還要來的小。唯LS與其在固化後5分鐘結果相近，無論是在固化後5分鐘或存放於37℃人工唾液30天後，這4種樹脂都被確定為線黏彈性材料，而潛變柔度的大小為Z350 flow > P60 ≈ Z250 > LS。在動態實驗中，5分鐘的群組內的結果顯示儲存模數在50-60℃時有一個增強的現象，透過儲存模數與消耗模數(Loss modulus)間的相位角可得知樹脂的力學行為在此時黏滯(Viscous)行為所佔的比例提高許多。使用TTSP將動態實驗的數據平移形成主曲線時，並無法將此增加的現象表現出來。在30天的群組並無此現象發生。最後透過FEM計算與DIC量測到的潛變柔度相比，固化30天後的模型與實驗結果相當的一致，但固化後5分鐘的結果則出現很大的誤差。因此在最後Class-V的牙齒模型中，只針對固化30天後的材料性質進行模擬，無論在填補LS的模型中牙釉質與樹脂的等效應力都是最大的。
由以上結果，四種牙科複合樹脂皆為線黏彈性材料，但材料內部結構須達到穩定狀態後，才能用TTSP去描述材料的行為。

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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