- 學位論文
金屬瓷冠上不同鑲瓷面厚度對其陶瓷抗斷裂強度之探討
Porcelain Fracture Resistance in Metal-Ceramic Crowns with Different Veneer Thickness
摘要
實驗目的：鑲瓷面的斷裂在臨床上甚為常見，且其所產生的美觀與功能的問題，往往會造成病人以及牙醫師的困擾。本實驗的目的探討不同厚度的鑲瓷面，作用在植體的金屬瓷冠上時，其鑲瓷面的抗斷裂強度是否會受厚度的影響。 材料與方法：40顆寬高長為8×8×8 mm的立方體形狀的金屬瓷冠製作成兩種不同厚度的鑲瓷面，在咬合面、頰側面、近心面、舌側面及遠心面等比例削減1.5mm及2.5mm的厚度，以製作分別為Group 1與Group 3：鑲瓷面為1.5mm；Group 2與Group 4：鑲瓷面為2.5mm，並分成為四組，每組各10顆。並選用Brånemark RP的植體類比體，從平台開始露出約2 mm的高度，並注入硬石膏倒模型，以製作寬高長為30×30×84 mm的實驗模具。植體類比體接上簡易式支台齒後，以暫時黏著劑將金屬瓷冠接上。首先，在Group 3與Group 4的金屬瓷冠上，先以80牛頓、頻率為3Hz，作100,000次垂直的動態力，施壓在近心側邊緣崤咬合面內1mm以作測試，以模擬半年內口腔的咀嚼運動。之後，將所有實驗組的金屬瓷冠固定上拉力測試機（Instron 5566），並以0.5mm/min的速度施壓在金屬瓷冠上近心側邊緣崤咬合面內1mm，直到鑲瓷面發生斷裂，並記錄各組金屬瓷冠的平均抗斷裂數值（kgf）。且利用掃瞄式電子顯微鏡觀察裂紋的型態。以二方分類變異數分析法（two-way ANOVA）與獨立樣本T-檢定（independent t test）來比較不同組之間的差異，同時觀察二項變因，包括不同厚度的鑲瓷面以及動態力是否參與對金屬瓷冠是否有所影響。統計顯著之水準定義：p＜0.05。 實驗結果：（1）Group 3與4的金屬瓷冠經過垂直的動態力測試後，鑲瓷面並沒有發生斷裂，只有凹洞的產生。（2）各實驗組經過單次負載測試後，所得的平均瓷抗斷裂值分別為：Group 1：129.63±12.65 kgf；Group 2：116.08±10.83 kgf；Group 3：84.18±3.98 kgf；Group 4：66.94±11.05 kgf。（3）經過單次負載測試，對於厚度不同的鑲瓷面，只有進行過週期性疲勞測試的實驗組（Group3&4），其瓷抗斷裂的平均值呈現統計上的差異。（4）進行週期性疲勞測試的金屬瓷冠，在電子顯微鏡的觀察下，凹洞處的陶瓷有裂紋形成及裂紋向外擴散的情況。另外，進行單次負載測試的金屬瓷冠，斷裂面較為平整。 結論：根據本實驗的結果，臨床上當補綴物其鑲瓷面的厚度減少至1.5 mm內，能降低鑲瓷面斷裂的機會，而不減少其美觀。
並列摘要
Purpose: Fracture of ceramic veneers is frequently observed in clinical practice and poses an esthetic and functional dilemma both for the patient and the dentist. The purpose of this study was to compare the porcelain fracture resistance between two different thickness of porcelain on the cement-retained implant metal-ceramic crowns. Material and methods: Forty (8×8×8 mm, W×H×L) cubic-shaped single metal-ceramic crowns were fabricated with two different thickness (1.5 mm or 2.5 mm) of porcelain and divided into four groups (10 crowns each): Groups 1 & 3 (1.5 mm), Groups 2 & 4 (2.5 mm). All the samples were cemented on 1mm Easy abutment above a Brånemark RP implant analog embedded in a 30×30×84 mm type IV die stone block. Groups 3 & 4 were first exposed to a vertically dynamic loading of 80N for 100,000 cycles to simulate masticatory function at mesial marginal ridge of the occlusal surface. Afterwards, all the samples were positioned in a custom testing apparatus and vertically loaded on the mesial marginal ridge of the occlusal surface with a universal testing machine (Instron 5566) at a crosshead speed of 0.5 mm/min until fracture. SEM fractographic analysis was utilized to determine the fracture patterns. Mean values of load at fracture (kgf) were recorded in each group and compared with a 2-way ANOVA and independent t-test (p＜0.05)(factors: porcelain thickness, with/without dynamic loading). Results: 1. No obvious ceramic fracture except digging pits was observed in Groups 3 & 4 after dynamic loading. 2. Mean values of loads required to fracture the crowns were as follow: Group 1: 129.63 ± 12.65 kgf; Group 2: 116.08 ± 10.83 kgf; Group 3: 84.18 ± 3.98 kgf; Group 4: 66.94 ± 11.05 kgf. 3. Dynamic loading prior to fracture test reduced the mean fracture loads significantly in Groups 3 & 4. 4. Cohesive or adhesive fracture of the porcelain can be observed in all four groups in fracture test. Conclusions: From a clinical viewpoint, to diminish the porcelain thickness of about 1.5mm, can decrease the probability of porcelain fracture of metal-ceramic crowns.
參考文獻
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