激光熔覆技术烤瓷冠边缘适合性的实验研究

Experimental study on marginal fit of selective laser melting porcelain-fused-to-metal crown

目的通过对传统失蜡铸造和激光熔覆两种技术制作的钴铬合金烤瓷冠以及浅凹型和直角肩台型两种牙体预备形态制作的激光熔覆技术烤瓷冠的边缘适合性进行比较,以探讨激光熔覆技术烤瓷冠的边缘适合性。方法选取上颌前磨牙30颗,随机分成3组,每组10颗,按烤瓷冠要求常规牙体预备。A、B组用浅凹型边缘,C组用直角肩台。A组为传统失蜡铸造钴铬合金烤瓷冠,B、C组为BEGO德贝尔激光熔覆技术钴铬合金烤瓷冠;3组全用聚羧酸锌水门汀粘结剂粘固,经环氧树脂包埋后,沿颊腭向中间剖开烤瓷冠和牙体,用金相显微镜及电子显微镜观察和测量各组的颊、腭侧冠边缘间隙的大小。结果 A组烤瓷冠的水平边缘间隙为79.61±11.45μm,垂直边缘间隙94.90±7.09μm,绝对边缘间隙114.94±8.60μm;B组激光熔覆技术钴铬合金烤瓷冠的水平边缘间隙67.76±9.20μm,垂直边缘间隙82.54±9.92μm,绝对边缘间隙105.35±9.84μm;C组激光熔覆技术钴铬合金烤瓷冠的水平边缘间隙72.72±9.03μm,垂直边缘间隙88.11±9.53μm,绝对边缘间隙102.48±9.15μm。B组与A组比较差异有统计学意义(P<0.05);B、C组之间的差异无统计学意义(P>0.05)。结论激光熔覆技术钴铬合金烤瓷冠边缘水平边缘间隙、垂直边缘间隙、绝对边缘间隙均小于120μm,均达到临床可接受的范围内。激光熔覆技术钴铬合金烤瓷冠比传统失蜡铸造钴铬合金烤瓷冠边缘适合性更好。牙体预备采用浅凹型(B组)和直角肩台型(C组)制作的激光熔覆技术钴铬合金烤瓷冠边缘适合性无明显差异。

Objective To evaluate the marginal fit of Debel SLM PFM crown comparing with the conventional fabrication crown by measuring marginal gaps of two kinds of Co-Cr alloy PFM crowns and two types finished line（chamfer and shoulder）. Methods Thirty extracted maxillary premolars were randomly divided into three groups（A group, B group, C group, n=10 each）. Teeth were prepared according to the requirements of PFM crown. Teeth in group A and B received a chamfer finish line preparation, whereas teeth in Group C received a shoulder finish line. Teeth of A group were restored with conventional Co-Cr alloy PFM crowns. B group and C were restored with Debel SLM PFM crowns. Then, PFM crowns of three groups were attached to their teeth respectively with zinc polycarboxylate cement.Specimens were sectioned in half along the mid long-axis and in the buccopalatal direction after they were embedded in epoxy resin. The marginal gaps were measured by using metallurgical microscope and electron microscope at the buccal and palatal edge of each section. Results The horizontal marginal gap, vertical marginal gap and absolute marginal gap in Group A were 79.61±11.45μm, 94.90±7.09μm and 114.94±8.60μm respectively. In Group B they were 67.76±9.20μm,82.54 ±9.92μm and 105.35 ±9.84μm. In Group C they were 72.72 ±9.03μm, 88.11 ±9.53μm and 102.48 ±9.15μm.Horizontal marginal gap, vertical marginal gap and absolute marginal gap of Debel SLM PFM crowns in Group B was significantly smaller than that of traditional Co-Cr alloy PFM in Group A（P〈0.05）; The difference was significant（P〈0.05）. There was no significant difference between Group B and Group C in horizontal marginal gap, vertical marginal gap and absolute marginal gap（P〉0.05）. Conclusion Horizontal gaps, vertical gaps and absolute gaps of three groups were in suitable range. The marginal fit of Debel SLM PFM crown was better than that of conventional Co-Cr alloy PFM crown;There was no significant difference between shoulder and chamfer preparation designs in the marginal fit of Debel SLM PFM.