【作者】 苏润刚；

【导师】 艾红军；

【作者基本信息】 中国医科大学 ， 口腔临床医学， 2002， 硕士

【摘要】 前言 随着稀土永磁合金磁学性能的不断提高，稀土永磁体在口腔修复及正畸领域中的应用日益广泛。其中，义齿磁性固位体由于具有与其它固位方式不同的特点和优势，而在临床中越来越被广泛应用。国内生产的Z-1型磁性固位体，虽然在磁路设计上进行了很好的改进，但因防腐蚀问题等原因，而未能在口腔临床中推广。目前，国外已研制出多种用不锈钢包裹的磁性固位体产品，不论在减少口腔内的漏磁，还是在提高耐腐蚀性能上都取得了较好的效果，使得磁性固位体在口腔中的应用更加安全。 我们结合国内外的研究成果，开发适合于临床应用的同类产品，并进一步改善其结构和性能，使其国产化，必将有力地促进义齿磁性固位体在国内口腔领域中的广泛应用。本实验通过体外培养细胞的形态学观察及MTT比色法，对在义齿磁性固位体中将使用的两种特殊不锈钢的生物相容性进行初步检测，并与口腔科常用的钴铬合金、纯钛的生物相容性进行比较和评价，以便为义齿磁性固位体的临床应用，提供生物学依据。 实验材料和方法 1．实验材料 将实验试样分为：A组：非磁性不锈钢（S₁），B组：磁性不锈钢（S₂），C组：纯钛（Ti），D组：钴铬合金（Co-Cr），E组：PVC材料。将A～E组材料制成长、宽、厚度分别为10mm、9mm、3mm的长方体。消毒灭菌后，放入24孔培养板中，用RPMI 1640培养液配制材料浸提液。选用传代的对数生长期的L-929细胞，用RPMI1640液配制成密度约为1.0×10⁵个／ml的细胞悬液备用。 2．实验方法 取96孔培养板，每孔加人细胞悬液100pl。在l－5组孔中分别加人A－E组的材料浸提液100…，在第6组孔内加人RPMI1640培养液 100 gi后，放人培养箱中培养。分别于培养后的 l－5天各取一块培养板，在倒置相差显微镜下观察活细胞的形态。在每孔中加入 sing／Inl的 M’IT液 20…，继续培养 4 ／J’时后取出。吸出培养液，在每孔中加人DMSO 150pl，用自动酶标仪检测吸光度值。将各组的吸光度值作单因素方差分析和均数间两两比较的统计学分析。计算各组的细胞相对增殖率（RGR）并作细胞毒性级评定。 实验结果 1．细胞的形态学观察：培养24小时，阳性对照组中贴壁生长的细胞呈梭形或多角形，悬浮的细胞呈圆形或不规则形，胞质内出现空泡及颗粒状物质。其余各组的细胞几乎全部贴壁生长，形态正常，胞质均匀。培养 120小时，阳性对照组中的细胞大部分脱落，胞质、胞核浓缩，甚至可见许多质膜崩解、核膜破裂的死亡细胞。其余各组细胞大部分继续贴壁生长，细胞密度增加，可见散在的悬浮的退化细胞及个别的死亡细胞。 2．统计学处理结果：金属材料组及阴性对照组与阳性对照组之间的吸光度值的差异均有统计学意义(P＜0．05或P＜O．01八四种金属材料组的细胞相对增殖率由大到小的顺序依次为：纯钛。S；不锈钢J。不锈钢、钻铬合金。S；不锈钢和S。不锈钢对细胞有轻微的毒性(RGR降低 3％人钻铬合金对细胞表现出二级细胞毒性（RGR降低 11％人但统计学分析结果显示：四种金属材料组与阴性对照组的吸光度值之间的差异均无统计学意义k＞o．05人 ·2· 讨 论 随着磁能积大而体积较小的磁体的应用，义齿磁性固位体性能被不断提高，受到医生和患者的青睐。然而，永磁体产生的静磁场可能对口腔周围软组织等造成负面影响，故应尽量减少磁体周围的磁场强度。另外，磁体在口腔环境中还容易被氧化腐蚀，一旦被氧化腐蚀后，不但磁力下降，而且腐蚀产物还可以产生一定的毒性。因此，各种磁性固位系统都采取了一些防腐蚀措施，如包裹树脂，电镀镍（NiX铬＊r）等方法，但这些措施都不能很好地解决防腐蚀问题。 我们结合国内外的研究成果，开发了新的义齿磁性固位体，通过将其轭铁材料、内装永磁体和磁路设计等的最优化，而最大限度地发挥其功能和安全可靠性。其中使用的轭铁材料采用了超纯高铬铁素体不锈钢u＊，它是一种软磁合金，具有高的磁导率和低的矫顽力，而且具有优越于一般的奥氏体不锈钢的足够的耐腐蚀性。我们还选用了高级的非磁性不锈钢门1）用作包裹磁体的材料，它具有优良的机械性能及耐腐蚀性。在不锈钢的接缝处，还采用了先进的精密激光焊接技术，达到完善的密封效果，有效地保证了磁体不被腐蚀，同时又不影响磁性固位体的固位力。在将这两种特殊不锈钢应用于磁性固位体中以前，为了确保它们不对人体带来某种损害，则需要对其临床应用中的生物相容性作一评价。 体外细胞毒性试验是筛选材料良好的生物安全性的一种重要方法，它与材料在体内的毒性作用有一定的相关性。本实验采用生物相容性优良的纯钛及临床常用的钻铬合金作比较，将材料浸提液与L－929细胞接触培养后，作细胞的形态学观察及MTh比色，评价被测试材料对细胞造成的毒性损害。结果显示上；非磁性不锈钢与S。磁性不锈钢浸提液对细胞的增殖均产生轻度抑制，这可更多还原

【Abstract】 PrefaceAlong with the increasing of the magnetism function, rare earth permanent magnet is being applied to the dental prosthetics and ortho-dontics extensively. Among them, magnetic attachment has been ap-plied to clinic extensively because of having different characteristics and advantages with others. Now, the magnetic retainer, which shell was wrapped up with stainless steel, has already been manufactured in abroad, and has further better characteristics than others whether in the decrease of leaking magnetism, or in the function of resistant cor-rosion. The application of dental magnetic retainer in oral becomes more safe.Combining together the domestic and foreign achievements, we develop a same kind of product suiting for the clinical application, and further improve its construction and function, which will promote an extensive application of magnetic retainer in the domestic dental realm. This experiment investigated the biocompatibility of two kinds of special stainless steel materials that will be used in the magnetic re-tainer by MTT - assay for the culture cells in vitro, and compared with pure titanium and cobalt - chrome alloy that are often used in oral, in order to provided a biological basis for the clinical application of the magnetic retainer.Materials and Methods1. The experiment materials were divided into; A set: the medi-cal stainless steel (S1,) , B set; magnetic stainless steel (S2) , C set; pure titanium, D set; Co - Cr alloy, E set: PVC material. A ~ E set materials were made into some cuboids that length, breadth, thickness were respectively 10 mms, 9 mms, 3 mms. After disinfected and ster-ilized, the materials were put into 24 bores culture plate. Then we used the RPMI 1640 culture liquids to prepare the extracting liquids of those materials. We chose the logarithms generate term L -929 cells, and used the RPMI 1640 liquids to prepare the cell suspending liquids which density was roughly 1. 0 x 10 /ml.2. The experiment methods; To take 96 bores culture plates, and add the cell suspending liquids l00#d into each bore. Respectively add the A ~ E set materials extracting liquids l00#l into the group 1 ~ 5 bores, and add RPMI 1640 culture liquids l00#l into group 6 bore, then put them into the culture box. Respectively take out a culture plate after educating 1 ~ 5 day, and observe the changes of cell form by upside down and discrepancy microscope. To add 5mg/ml MTT liquids 20#J into each bore, and take out the plate after educating 4 hours continuously. To suck out the educate liquids and join DMSO 150#l into the each bore. To examine the optical density by automatic enzyme immunoassay analyzer, and calculate the rate of cells relative growth (RGR) and assess the cytotoxic rank of each materials.Results1. The cell’s morphological observation; The first day, in the positive control the cells growing on the plate showed fusiform or poly-horn shape, and the suspending cells showed circular or irregularform, and appeared vacuoles or grains in the cytoplasm . The cells of the rest groups all almost grew with attaching on the plate, and with enmorphism and the steady cytoplasm. The fifth day, in the positive control the cells almost shed off, which cytoplasm and cell nucleus concentrated, and even there were many dead cells which plasmale-mma collapsed and karyotheca solved. The ceUs of the rest groups all almost grew with attaching on the plate continuously, and the cell’s density creased. There were few suspending degenerate cells or dead cells.2. The results of statistical analysis; There were a significant difference in the optical densities between metal material groups or the negative control and the positive control (P<0.05 orP<0.01). Ac-cording to the rate of cell’s relative growth of the four metal material groups, the sequence from big to small was; the pure titanium, S1 stainless steel, S2stainless steel, cobalt - chrome alloy. S1 stainless steel and S2 stainless steel showed slight cytotoxicity ( the RGR de-creased 3% ) , Cobalt更多还原