输油管接头的铸造工艺设计及其优化【研究类】【无图】
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输油管接头的铸造工艺设计及其优化
32页 9000字数+说明书+开题报告+任务书+答辩PPT+外文翻译
中期检查报告.doc
任务书.doc
外文翻译--关于重铸合金镍铬牙科铸造合金中元素的释放和细胞毒性的体外分析 中文版【优秀】.doc
外文翻译--关于重铸合金镍铬牙科铸造合金中元素的释放和细胞毒性的体外分析 英文版【优秀】.pdf
输油管接头的铸造工艺设计及其优化开题报告.doc
输油管接头的铸造工艺设计及其优化答辩PPT.ppt
输油管接头的铸造工艺设计及其优化论文.DOC
输油管接头的铸造工艺设计及其优化
摘要:
通过分析零件的结构和特点，选用粘土湿型砂手工造型方法，采用两箱造型并确定了浇注位置和分型面。确定了机械加工余量、起模斜度、铸造收缩率等工艺参数。根据各铸造工艺参数，用Pro/E软件画出铸件的3D图。根据铸件形状特点，设计了内腔处1#、底部2#两个砂芯。采用开放式中注浇注系统对铸件进行浇注，利用奥赞公式计算阻流截面积，确定浇注系统的各截面积和尺寸，并完成对冒口的初步设计。用View Cast铸造模拟软件对未设冒口的的铸件进行凝固过程数值模拟，模拟结果显示所产生的缺陷与之前设想一致。采用顶部收缩冒口和两侧各圆柱形冒口对铸件进行补缩。再用View Cast软件对带有冒口和浇注系统的铸件进行充型和凝固过程数值模拟，模拟结果显示浇注过程平稳，未出现紊流现象，铸件无缺陷。通过减小尺寸对冒口进行优化。
关键词：铸造工艺；数值模拟；凝固过程；充型过程
目录
第一章 绪论1
1.1选题背景和研究意义1
1.2本课题在国内外的研究状况及发展趋势2
1.3 主要研究内容3
1.3.1铸造工艺研究3
1.3.2浇注系统的设计3
1.3.3补缩系统的设计3
1.3.4用铸造软件模拟3
第二章 铸件简述5
2.1零件名称5
2.2 用途5
2.3 材质5
2.4 技术要求6
第三章 铸造工艺方案7
3.1工艺方法和说明7
3.2 分型面选择7
3.3 浇注位置的选择7
3.4 型腔数量的设计8
3.5 砂芯设计8
3.5.1 造芯方法与造芯数量8
3.5.2 砂芯的结构与尺寸9
3.6 工艺参数10
3.6.1 铸件的尺寸公差10
3.6.2 铸件的质量公差10
3.6.3 机械加工余量10
3.6.4 铸件模样的起模斜度11
3.6.5 铸造收缩率11
3.6.6 最小铸出孔及槽11
3.7 浇注系统的设计11
3.8 冒口的计算13
第四章 铸件充型及凝固过程数值模拟15
4.1 View Cast的实现过程15
4.2 铸造工艺方案的凝固过程模拟15
4.3 利用View Cast软件设计冒口17
4.4冒口的优化20
4.4.1 凝固过程数值模拟20
4.4.2 充冲型过程数值模拟22
结束语25
致谢26
参考文献27
附录28
第三章 铸造工艺方案
3.1工艺方法和说明
该输油管接头铸件质量约658.8g，属于较小型铸件。铸件的外部结构简单但其内部结构复杂，壁厚较小且分布较均匀，单件生产。出于降低铸件生产成本和保护环境的考虑，同时满足铸件精度及技术要求较高，本工艺中采用湿型粘土砂手工造型铸造方法来生产。
3.2 分型面选择
为了铸件能合理地从模具中取出，采用水平浇注，该零件的分型面只有一种，如下图3.1所示：
- 内容简介：
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西安文理学院本科毕业设计（论文）中期检查表题 目输油管接头的铸造工艺设计及其优化学生姓名白粉毅学 号08102080241专业名称机械设计制造及其自动化指导教师何斌锋 罗振元检查时间2011-4-班 级08机电2班毕 业 设 计（论文） 进 展 情 况 通过对铝合金材料的铸造工艺设计相关资料的学习，以及对整个铸造工艺设计步骤的了解，现基本完成以下设计工作：1.完成了输油管接头铸件的三维设计，包括两部分：确定铸件的收缩率及机械加工余量，进而由此计算铸件尺寸；铸件三维实体的绘制。2.输油管接头铸造工艺方案及参数的确定：铸造类型，铸造所选砂型，分型面的确定，浇注位置的确定，铸件的尺寸及重量公差，最小铸出孔3.开始设计输油管接头浇注系统设计：，包括浇注系统中各浇道的结构尺寸设计计算；砂芯的设计：芯头结构及芯头尺寸确定。并对浇注系统、型芯的三维图进行绘制。下一步设计工作内容是采用铸造模拟软件对所设计浇注系统进行模拟验证，看设计的浇注系统是否能够实现铸件无缺陷的要求，并根据模拟结果进行浇注系统的优化及补缩系统设计。 指 导 教 师 意 见签字： 年 月 日教研室意见签字： 年 月 日西安文理学院本科毕业设计（论文）任务书题 目输油管接头的铸造工艺设计及其优化学生姓名白粉毅学 号08102080241专业班级08机械2班指导教师何斌锋罗振元 职 称助教工程师教 研 室机械教研室毕业设计（论文）任务与要求1、输油管接头在输油管连接处起连接和转向作用。这就要求输油管接头的质量和密封性能很高。传统的铸造方法都是建立在“试错法”的基础上，这种方法最大的缺点就是周期长，成本高，引入计算机模拟技术在输油管接头的铸造工艺中，可以缩短周期，同时降低成本。2、明确设计任务要求，查阅相关文献资料，确定输油管接头铸造工艺的设计步骤。3、要求根据接头的实际工作情况设计出该接头铸造工艺过程。4. 设计出铸造工艺后，根据零件图采用ProE绘制出该接头的三维造型，并将设计的包括浇、冒口在内的浇注系统造型。5. 采用铸造模拟软件对所设计浇注系统进行验证，看设计的浇注系统是否能够实现铸件无缺陷的要求。6. 绘制出该铸造工艺图。毕业设计（论文）工作进程起止时间工作内容开始至寒假第一周第二周至第八周第七周第九周至第十二周第十三周搜集课题相关资料，了解课题发展动向开题报告设计计算、绘图及模拟试验验证中期检查撰写设计说明书（论文）答辩开始日期 2012-1-10 完成日期 2012-5-11 教研室主任（签字） 系主任（签字） 西安文理学院本科毕业设计（论文）附录关于重铸合金镍铬牙科铸造合金中元素的释放和细胞毒性的体外分析摘要 铸造合金的重铸影响其组成和元素的释放，这可能是不同于纯合金在周围组织的细胞毒性作用。为了调查研究元素的释放和细胞毒对市售常用于制作固定义齿的牙科铸造镍铬合金的影响而展开体外研究。对含三种成分的镍铬合金99 Wiron（A），合金陶瓷（B），高镍CB（C） 进行了测试。合金试样（每份3 95毫米）的铸造和分组情况如下：第一组（A1/B1/C1）：100纯合金；第二组（A2/B2/C2）：50未重铸50重铸合金; 第三组（A3/B3/C3）：100重铸合金。将每个组的磁盘中每种合金类型转移到改良后的杜尔贝科鹰中，并且在温度为37摄氏度，二氧化碳含量5%的环境下放置3天。使用电感耦合等离子体质谱对从金属合金到培养基的镍，铬，钴，铜和钼元素释放进行了研究。使用老鼠纤维细胞和MTT实验进行细胞毒性测试。实验控制包括6种来源包括细胞不包括合金试样。用t检验双向方差分析进行数据分析。对于各个铸造组每10亿中释放元素的总量公布，第一组，A1-6.572，B1-6.732，C1-8.407; 第二组，A2-22.046，B2-26.450;，C2-29.189第三组，A3-84.554 ,B3-88.359，C3- 92.264。在所有试验组更多数量的高镍CB元素比基金属陶瓷和Wiron99被释放。用MTT法分析活细胞百分比分布，第一组，A1-62.342，B1-61.322，C1-60.593；第二组，A2-58.699，B2-56.494，C2-52.688，第三组，A3-53.101，B3-52.195，C3 - 47.586。活细胞存活于Wiron99含量多于金属陶瓷和高镍CB的培养基中；元素释放数量随着重铸合金增加。在100纯合金，50重铸合金和100重铸合金试验中，与合金陶瓷和wiron99相比，三种合金当中高镍CB有显着较高的元素释放相比。100纯合金，50重铸合金和100%重铸标本表明wiron99是元素释放最少的合金。100纯合金是所有组中三种合金的细胞毒性最低的，但它们在50重铸合金和100重铸组中细胞毒性比较大。所有三种不同类型的铸造中Wiron99合金细胞毒性最少，其次是合金陶瓷和高镍CB。合金的重铸显着增加元素释放和其细胞毒性。关键词 重铸 细胞毒性 元素释放 牙科铸造合金 基本金属N. R. Reddy印度，拉邦，安德拉，中正Tirupathi，Teja公司牙医科学研究所A. P. Abraham (&) .K. Murugesa n. V. Matsa印度钦奈Ramapuram，SRM大学，SRM牙科学院，假牙修复术、顶和连接科电子邮件：drponabe临床意义 铸造修复用在密切接触不同时期的口腔组织中，可能会引起局部不良组织反应，如牙龈炎和牙周炎。牙科铸造合金的细胞毒性和生物相容性程度已涉及到合金成分和从合金释放到周围介质的元素。重铸的镍铬合金增加元素释放的数量，从而激发细胞毒性的潜力。介绍在牙科领域的科学和技术的进展材料科学引领了基本的金属合金的发明在牙科的应用。黄金的一个替代品是引入铬合金，用镍铬和钴铬这些做基础合金是考虑到价格较低，同时也具备等同的质量和生物相容性牙科修复工作中使用功能。根据其组成和口腔环境知基本金属合金易产生各类腐蚀。对牙科病人而言，从牙科合金中金属元素的释放是一个潜在的健康问题。已知金属会导致毒性发炎、过敏反应或突变。元素释放的重要后果是细胞毒性存在于培养物周围的组织。铸造修复用在密切接触不同时期的口腔组织中，可能会引起局部不良组织反应，如牙龈炎和牙周炎。牙科铸造合金的细胞毒性和生物相容性的程度与合金成分和从合金释放到周围介质的元素有关。用于浇口等形式的合金或有缺陷的铸件重铸已实行，以防止铸造后材料的浪费。元素的识别和承受细胞毒作用的浓度很重要，因为这将有助于改善和设计新的合金，以避免对口腔有害的元素释放。研究假设重铸基金属合金会改变合金的化学性质，从而影响其元素的释放和随后引起的细胞毒作用。本体外研究的目的是调查镍铬基金属合金重铸的影响及其潜在的毒性作用和释放到培养基的元素。研究的目的是评估镍铬合金元素的释放和细胞毒性及纯合金（第一组），50的纯合金和50的重铸合金（第二组）和100的重新铸造合金（第三组）相关元素释放和细胞毒性。材料和方法进行的体外研究的镍铬合金来自三个不同厂家生产的金属陶瓷（图1；表1）。为了方便和参考合金已编码。表1 镍铬牙用铸造合金的成分说明序号合金名称生产厂商成分 (wt %)*代码1 Wiron 99贝格 (德国)镍-65 A铬-22.5钼-9.5铌-1氧化硅-1铁-0.5铯-0.52 合金陶瓷拉伯李讷 (欧洲)镍-62B铬-26钼-10氧化硅-1.5其他-0.53高镍 CB光市 (日本)镍-60C铬-10铜-15锰-7.9其他-7.1 *表中成分比例为生产厂家提供。 图1 金属陶瓷镍铬合金 图2 铣削模合金试样的制备用数控铣床机将一个半径为5毫米、厚度为的3毫米的圆形铝金属模具中心位置铣削出1厘米厚的铝块（图2）。用绿色镶嵌铸造蜡制备直径为10毫米厚3毫米的蜡模（图3）。德国贝格公司使用金属模具。对于三组合金制备了总数为108的蜡型：第一组100纯合金（A1/B1/C1）；第二组：50的纯合金50重铸合金（A2/B2/C2）；第三组：100重铸合金（A3/B3/C3）。铸造模式表2中给出了三组蜡模的成分比例。直浇道蜡模是将铸造磷酸盐注入环衬干纤维素纸的金属环内粘结而成的。在此之后，他们在感应铸造机上利用失蜡法铸造试样（图4）。德国贝格采用相应的合金。获得用于重铸的金属来自清洗过取来的浇道和此前已在第一组铸造过的合金粒。工作台冷却后剥离铸造环和同时使用250微米的三氧化二铝进行喷砂，以消除表面多余材料。切下浇道，完成标本制作和依次用金刚砂盘、金属剪、橡胶轮和砂纸抛光，使用手工电机工具进行烧结抛光。抛光的磁盘放在洗涤剂溶液浸泡5分钟，然后用软毛刷擦洗，再在自来水下冲洗5分钟。然后将标本放在无菌蒸馏水用超声处理清洁，最后在温度为150 摄氏度下灭菌60分钟。 图3 蜡模 图4 铸件试样组别 类型合金标本序号(A) Wiron 99(B)金属合金(C)高镍 CB第一组 100% 新12A112B112C1第二组50% 新50% 重铸12A212B212C2第三组100% 重铸12A312B312C3 表2 各组标本的成分分布 图5 改良的杜尔贝科鹰培养基（DMEM） 图6 用0.5毫升小鼠纤维细胞悬挂液组织的培养板元素释放 从每个组的每个磁盘转移六磁盘各类型合金到6毫升的改良后杜尔贝科的鹰培养基（DMEM培养基）中，在空气含5的二氧化碳、温度37摄氏度下培育3天。通过补充5新出生的小牛血清，100 U / ml青霉素，链霉素和0.25 微克/升的两性霉素B制备 D MEM培养液（图5）。使用电感耦合等离子体质谱法（ICP-MS）分析了介质中存在的镍，铬，钼，钴和铜。保持用ICPMS分析用去离子水稀释的液体，同时记录读数。一式三份的吸收用来确定合金中十亿分之几（PPB）不同元素释放的平均浓度。细胞培养和细胞毒性试验细胞毒性试验，来自三组不同铸造合金的其余6个的磁盘被放置在一个周围24摄氏度的组织培养皿的中心和0.5毫升悬浮小鼠纤维细胞液添加到良好细胞中（图6），并放置2小时。继这之后将0.5毫升的DMEM加入细胞，在空气含5二氧化碳、温度37中培养3天。这些控制条件包括6种来源其中含有细胞没有合金标本。在培养期后金属板从恒温箱上拆除，通过测量琥珀酸脱氢酶的评估材料的细胞毒性（SDH），采用MTT法检测细胞的活动。将MTT试剂加入到合金标本周围的板里，板被转移到96孔的板，为了读者读酶联免疫吸附（ELISA）数， MTT法遵循的协议概述如表3。表3 MTT法执行议定书 步骤 内容1 每个瓶子放1,000-100,000板细胞2 培养 624 小时3 加入 10 微升 MTT 试剂4 培养 24 小时 直到出现紫色沉淀5 加入100 微升洗涤剂试剂6 在室温下放在黑暗2小时7 在570nm处记录吸光度可以用以下公式计算： ；统计分析从MTT分析和质谱法分析取得统计分析的成果。用来计算的P -值的一种方法是方差分析。利用图凯HSD程序的多重范围测试用来确定在5%的水平重大群体。结果元素释放在三个铸造合金组均可见元素释放。镍，铬，钴，铜和钼等元素被释放。表4和表5总结出在三过程中元素释放通过不同的铸造合金。高镍CB是三种铸造合金中元素释放最高的，其次是金属陶瓷和Wiron 99。在磷含量小于0.05的研究所有元素分析表明，随着重铸材料百分比增加元素释放显着增加的（图1）。细胞毒作用的结果在三组中活细胞的比例列在表6。对三种铸造条件的三个基本金属合金细胞活性平均百分比分析和细胞毒性进行了观察，得出高镍CB最高，其次是陶瓷和wiro n99。结果表明，100%重铸合金比50%的纯和50% 重铸有更多的细胞毒性和50%纯50% 重铸合金比纯合金有更多的细胞毒性（图2）。 10953.67414.0921.1224.40814.7271.4014.86514.94410953.67414.0921.1224.40814.7271.4014.86514.944 图1 三种合金元素释放的比较 图2 各种合金的百分比表4 比较在三个铸造组中不同重铸合金释放元素的平均值组别种类材料平均 标准差P值水平在5%的显著群体第一组100% 纯合金A1 1.095 0.0520.0001 (sig)C1 Vs A1 and B1B11.122 0.081C1 1.401 0.082第二组50% 纯50%重铸合金A2 3.674 0.2880.0001 (sig)C2 Vs A2 and B2.B24.408 0.231C2 4.865 0.296第三组100% 重铸合金A314.092 0.7390.0001 (sig)C3 Vs A3 and B3B314.727 2.028C314.944 2.301表5 对三个铸造组从铸造合金中各元素的释放量（平均 标准差）元素合金第一组 第二组第三组镍Wiron 990.495 0.0102.901 0.16912.180 0.633金属合金0.402 0.0123.664 0.39913.580 2.088高镍 CB0.487 0.0903.354 0.29930.294 24.225铬Wiron990.071 0.0150.090 0.0210.222 0.077金属合金0.346 0.0440.084 0.0140.108 0.076高镍CB0.265 0.0920.458 0.0910.471 0.104钴Wiron 990.029 0.0080.074 0.0070.062 0.036金属合金0.048 0.0210.035 0.0070.065 0.013高镍CB0.027 0.0100.436 0.1280.051 0.015钼Wiron 990.501 0.0530.621 0.1181.629 0.195金属合金0.343 0.0510.524 0.0840.941 0.055高镍CB0.416 0.0290.044 0.0310.143 0.042铜Wiron 99金属合金高镍CB0.207 0.0560.573 0.1564.918 1.047组别合金百分比材料细胞活性百分比 (%)第一组100%纯A162.342B161.322C160.593第二组50%纯50%重铸A258.699B2 56.494C252.668第三组100% 重铸A353.101B352.195C347.556 表6 三个铸造组的细胞活性平均百分比值讨论金属是牙科充填程序已不可分割的组成部分。牙科铸造合金恢复的形式和缺失牙齿的结构的功能应该是生物惰性的。牙科铸造合金释放的金属元素是一种潜在的健康问题 2，8 。众所周知从铸造合金浸出的金属离子是引起会中毒炎症，过敏或突变反应 9，10 。通过体外和体内研究已发现这些被释放的元素。元素释放的一个重要的后果是其细胞毒性影响邻近组织，同时组织反应数量取决于被元素的释放57, 11, 12。合金选择具体条件如固定义齿是由三个因素的影响，即物理性质，化学性质，生物兼容性和成本。从恢复性过程方面来选择合金，黄金被视为高贵金属合金，被认为没有离子浸出，但是组织学研究反对这种错误理解2。黄金的高成本导致牙用铸造合金基金属的引入。镍与铬结合形成高度腐蚀的耐磨合金，主要以镍基为主的这些基金属合金与金合金比较。便宜， 高弹性模量（严厉），硬度高，密度较小，并拥有与黄金可比的耐玷污和腐蚀性1。由于拥有类似的物理、化学性质，基金属慢慢取代黄金用于铸造合金2，3，13，14 。通常商业化的用于固定假牙部分的基金属合金是镍铬合金1,2。根据制造商的不同，这些合金组成可能会有所不同，但基本成分是镍，铬和钼1。加入轻微成分会显着改变微观结构同时影响陶瓷粘结强度的性能以实现粘接所需的金属氧化层。根据生产所需的性能，这些微量元素的使用取决于制造商1。确定这些元素的允许浸出量，以防止在功能的不良副作用（毒性影响）。铸造合金以各种比例与新的合金配合再次被利用，这是进一步降低成本的做法3 。重铸合金的元素释放与纯合金的可能会有所不同。该合金的生物相容性取决于该合金的类型和释放到周围介质或组织的元素 5,15。为了评估从合金释放的元素，将合金存储在一个合适的介质，如人工唾液3个月；或在一个合适的培养基培育3天16-19。在培养基中保存和培养标本是一种切实可行的方法，作为步骤要求较短的时间跨度和更好的元素释放16。为进一步评估释放到介质元素量，重复使用各种方法，如原子吸收光谱法，发射光谱仪，电感耦合等离子体原子发射分光光度计（ICPAES），电感耦合等离子体质谱（ICPMS）20。对于微量元素的测定，ICPMS法是最快速，灵敏，精确和准确的多元素分析技术。用于评估细胞毒性的常用方法有微孔过滤器，琼脂覆盖法，MTT法测试。其中MTT法是一种简单的技术，可以直接从酶标仪计算出读数16。MTT法还有灵敏度高和重复性好，方便，快速，消除需要的放射性化合物和经济性等其他优点。制造商声称由于其组成变异，三种镍铬基合金（99 Wiron，金属陶瓷和高镍CB）常用于来自不同的普通制造公司的部分烤瓷固定假牙的金属加工。根据建议协议，进行标本的清洗和消毒。测试前标本放在150高压灭菌60分钟，以对其进行消毒1，16。重要的是，要注意这个过程可能影响这些合金的腐蚀模式，但是，所有这些合金标本得到相同的待遇，因此任何元素释放的细胞毒作用的差异会导致类型和合金成分或铸造过程的不同。目前的研究结果同意假设，基金属合金的重铸增加其潜在的细胞毒作用和元素释放。在研究中，所有新的合金试样元素释放显着低于重铸的标本。 在纯合金，重铸50和100重铸合金组中，三种合金当中，相对于金属陶瓷和Wiron99，高镍CB合金有显着较高的元素释放相比。在100纯合金，50重铸和100重铸标本表明wiron99的元素释放最少。在这项研究中表明，所有的基金属合金的测试均显示有细胞毒性作用。在活细胞细胞毒性分析结果和细胞活力的百分比中，显而易见在100纯合金标本中Wiron99，金属陶瓷和高镍CB的细胞毒性顺序递增。无论是50重铸或100重铸均表明，在三种合金中，随着合金的重铸活细胞的数量减少。50新的50重铸和100重铸研究表明，活细胞的平均数量和细胞活力的百分比在Wiron99比金属陶瓷和高镍CB更为显着。高镍CB的活细胞数量最少。在选择镍铬合金中，高镍CB是细胞毒性最强的，它明显比金属陶瓷和Wiron99更具毒性。这可能与这些合金在组成上区别有关13。高镍CB合金具有最大的细胞毒作用。对于所有的浇铸条件而言，可能是由于其含铜导致的。据报道，在文献中合金毒性的主要可能是由于铜的含量作用1。据报道，只有在含有16-27铬的镍铬合金中制定一个适当的保护氧化层，钼在氧化层的形成还具有的积极作用。由于铜基合金比非铜合金更容易变色和腐蚀，据观察，在本研究中从高镍CB释放显着的铜量到培养液中。在合金中铬和钼含量低的情况下，铜含量也可以解释这种合金相比其他镍铬合金在细胞毒作用更显著 1，3，17。因此，对于所有合金组， 50重铸组显着超过100的新合金组的细胞毒性，此外，100重铸组显着超过50重铸组的细胞毒性。这可能是由于这些合金的化学成分作用，这可能会提高合金溶出率，因此，从它们释放的元素可能会使ICPMS法分析的数量增加。从目前的研究结果看来，当合金被重铸合金类型和这些合金的元素起不同程度的影响，因此归于其细胞毒作用。局限性 这项研究的结果，需要进行以下相关局限性考虑。在DMEM介质中使用矿物或有机成分可能会影响合金的腐蚀敏感性，从而影响元素释放。虽然在目前的研究使用一个小样本（N= 6），发现不同群体之间的显着差异，充分说明其大型规模效应。然而，进行更充足合金类型的代表性的进一步研究需要更大的样本量。结论从研究中所取得的成果，证明了基金属合金的重铸影响元素的释放进而引起的细胞毒作用的假设。虽然它有重用50的重新铸造合金取自从先前的铸件浇道的形式添加新合金维持物理和化学性质，从这些重铸合金释放的元素更显著，因此将有一定的细胞毒作用。在当前研究的局限性，最可能得出的结论是显示了在纯和重铸形式下高镍CB是最高的元素释放和细胞毒作用，其次是金属陶瓷。在当前研究表明Wiron99是元素释放最少和细胞毒性最小的合金。参考文献1 菲利普斯牙科材料科学 Anusavice KJ（2003） 11日经济日报 圣路易斯 桑德斯 563-620期2 假牙剩余牙槽嵴的关系研究报告 Stein RS（1966） J Prosthet Dent 16 251-285 3 重铸对基金属合金的细胞毒性的影响 Ahmad Al-Hiyasat S, Darmani H (2005) J Prosthet Dent 93 1581644 关于牙用铸造合金的细胞毒作用调查 Al-Hiyasat AS, Bashabsheh OM, Darmani H (2003) Int J Prosthodont 16(1) 8125 从牙用合金金属释放的机制与动力学研究 Brune D (1988) Int Endod J 21 1351426 从牙用合金金属释放的机制与动力学研究 Craig RG, Hanks CT, Brune D (1990) J Dent Res 69 153915427 在合成唾液中钯 - 铜和镍铬合金腐蚀行为 Goehlich V, Marek M (1990) Dent Mater 6 1031108 手术牙科的教科书 Baum L, Philips RW, Lund MR (1995) 3日经济日报 WB Saunders, Philadelphia 529571期9 一些牙用合金体外和体内单独和组合测试的生物反应 Syrjanen S, Hensten-Pettersen K, Kangasniemi, Yli-Urpo A (1985) Biomaterials 6(3) 16917610 牙用合金提取物的细胞毒性和相应的金属盐溶液 Schmaltz G, Langer H, Schweikl H (1998) J Dent Res 77(10) 1772177811 牙用铸造合金的元素释放及其细胞毒性 Al-Hiyasat AS, Bashabsheh OM, Darmani H (2002) Int J Prosthodont 15 47347812 用完整的成分的稳定性和边际的准确性获得投冠和III型冠金合金重铸 Ayad MF (2002) J Prosthet Dent 87 16216613 对于义齿框架的基合金和IV型金合金的比较 Cunningham DM (1973) Dent Clin N Am 17 71972214 一个新的钴-铬-钼耐腐蚀陶瓷合金 Mezger PR, Vrijhoef MM, Newman SM, Greener EH (1988) J Oral Rehabil 15 42142815 牙用合金纤维连接蛋白的生物相容性体外测试表达模式和细胞增殖的关系利率 Grill V, Sandurucci MA, Di Lendarda R, Basa M (2000) Quintessence Int 31(10) 74174716 固定修复的基础 Shillingburg HT, Hobo S, Whitsitt LD, Brackett SE (1997) 3日经济日报 芝加哥Quintessence 365383期17 L - 929成纤维细胞，人牙龈成纤维细胞的响应和各种金属离子的组织肥大细胞Schedle A, Samorapoompichit P, Rausch-Fan XH et al (1995) J Dent Res 74 1513152018 牙用合金生物相容性sanduri体外分析 Grill Vittorio, Maria A (2000) Quintessence Int 31 74174719 牙用钛合金生物相容性实验的体外分析 Wang RR (1998) J Prosthet Dent 80 49550020 替代牙用铸造合金 Moffa JP (1983) Dent Clin N Am 27(4) 733746第 9 页ORIGINAL ARTICLEAn Invitro Analysis of Elemental Release and Cytotoxicityof Recast NickelChromium Dental Casting AlloysNagam Raja ReddyAnandapandian Ponsekar AbrahamKrishnan MurugesanVasanthakumar MatsaReceived: 30 December 2010/Accepted: 22 May 2011/Published online: 3 June 2011? Indian Prosthodontic Society 2011AbstractRecasting of the casting alloys affects thecomposition and elemental release which may have cyto-toxic effect different from the pure alloy in the surroundingtissues. An Invitro study was conducted to investigate theelemental release and their cytotoxic effects from com-mercially available NiCr dental casting alloys, commonlyused for fabricating fixed partial dentures. Three NiCralloys Wiron 99(A), Ceramet (B), and Hi Nickel CB (C)were tested. Alloy specimens (disks 3 9 5 mm) werecasted and grouped as follows: Group I (A1/B1/C1): 100%pure alloy; Group II (A2/B2/C2): 50% new with 50% recast;and Group III (A3/B3/C3): 100% recast. Disks of each alloytype from each group were transferred to Dulbeccosmodified eagle medium and left for 3 days at 37?C in anatmosphere of 5% CO2. Ni, Cr, Co, Cu and Mo elementalrelease from metal alloys into culture medium was inves-tigated using Inductively Coupled Plasma Mass Spec-trometry. Cytotoxicity was tested using mouse fibroblastcells and MTT Assay. Controls consisted of 6 wells con-taining cells with no alloy specimens. Data were analyzedby two-way analysis of variance followed by t-test. Thetotal amount of elements released in parts per billion forvarious casting groups were Group I, A1-6.572, B1-6.732,C1-8.407; Group II, A2-22.046, B2-26.450, C2-29.189;GroupIII,A3-84.554,B3-88.359,C3-92.264.Moreamounts of elements were released in Hi Nickel CB thanCeramet and Wiron 99 in all the three test groups. Per-centage of viable cells from MTT analysis were Group I,A1-62.342, B1-61.322 C1-60.593, Group II, A2-58.699,B2-56.494, C2-52.688, Group III, A3-53.101, B3-52.195,C3-47.586. The viable cells present in the culture mediawere more in Wiron 99 than Ceramet and Hi Nickel CB.Elemental release increased with amount of recast alloy.Amongst the three alloys tested Hi Nickel CB had signif-icantly higher elements released compared to Ceramet andWiron 99 in 100% pure alloys, 50% recast and 100% recastalloys. Wiron 99 showed least element release in 100%pure alloy, 50% recast and 100% recast specimens. 100%pure alloys of all three alloys are less cytotoxic, but theircytotoxicity is more on 50% and 100% re-casted alloys.Out of all three variations of casting Wiron 99 was leastcytotoxic, followed by Ceramet and Hi Nickel CB.Recasting of alloys significantly increased the elementsreleased and their cytotoxicity.KeywordsRecasting ? Cytotoxicity ? Elemental release ?Dental casting alloys ? Base metalIntroductionAdvances in science and technology in the field of dentalmaterial science have lead to the invention of base metalalloys for application in dentistry 1. Introduction ofchrome alloys has provided an alternative to gold, withthese resulted in NiCr and CoCr based alloys which areClinical ImplicationsCast restorations placed in close contact withoral tissues for various periods of time may elicit local adverse tissuereactions such as gingivitis and periodontitis adjacent to them.Degree of cytotoxicity and biocompatibility of dental casting alloyshas been related to alloy composition and elements released fromalloys into surrounding medium. Recasting of NiCr alloys increasesthe amount of elements released and hence the cytotoxic potential.N. R. ReddyC K S Teja Institute of Dental Sciences, Tirupathi, AndhraPradesh, IndiaA. P. Abraham (&) ? K. Murugesan ? V. MatsaDepartment of Prosthodontics and Crown & Bridge, SRM DentalCollege, SRM University, Ramapuram, Chennai, Indiae-mail: drponabe123J Indian Prosthodont Soc (Apr-June 2011) 11(2):106112DOI 10.1007/s13191-011-0075-8considered as economically less expensive and also havethe required qualities and biocompatibility for usage indental restorative work 2, 3.Base metal alloys are prone to various types of corrosiondepending on its composition and oral environment 1. Therelease of metallic elements from dental alloys is a potentialhealth problem to dental patient 4. Metals are known tocause toxic inflammatory allergic or mutagenic reactions.Important consequence of elemental release is cytotoxicityof adjacent tissues in cell cultures 5, 6. Cast restorationsbeing placed in close contact with oral tissues for variousperiods oftime may elicitlocal adversetissue reactionssuchas gingivitis and periodontitis adjacent to them. Degree ofcytotoxicityandbiocompatibilityofdentalcastingalloyshasbeenrelatedtoalloycompositionandelementsreleasedfromalloys into surrounding medium 7.Recasting of used alloys in the form of sprues ordefective casting has been practiced to prevent wastage ofmaterial after casting 3. Identification of the elements andtheir concentrations responsible for cytotoxic effects isimportant because it will help in improving and designingnewer alloys to avoid the release of elements which areharmful to oral cavity.Hypothesis of the study was that recasting of base metalalloys would change the chemical properties of the alloysand thus affect their elemental release and subsequentlyelicit cytotoxic effects. The aim of this invitro study was toinvestigate the effects of recasting of NiCr base metalalloys and their potential cytotoxic effects and elementalrelease into culture media. Objectives of study were toassess the elemental release and cytotoxicity of NiCralloys and correlate elemental release with cytotoxicity ofpure alloy (Group I), 50% pure and 50% re-casted (GroupII) and 100% re-casted (Group III) alloy.Materials and MethodsThe invitro study was undertaken with NiCr alloy formetal ceramic from three different manufacturers (Fig. 1;Table 1). Alloys have been coded for simplicity and ref-erence purposes.Preparation of Alloy SpecimensAn aluminium metal die with a circular space of 5 mmradius and 3 mm depth was milled in the centre portion of1 cm thick aluminium block using computerized millingmachine(Fig. 2).Waxpatterns10 mmindiameter9 3 mm thickness were prepared with green inlay castingwax (Fig. 3) (Bego-Germany) using the metal die. A totalof 108 wax patterns were made for three alloys for Group I:100% pure alloy (A1/B1/C1), Group II: 50% pure 50%recast alloy (A2/B2/C2), and Group III: 100% re-castedalloy (A3/B3/C3).Casting of the PatternThe wax patterns of the three groups were segregated asgiven in Table 2. The sprued wax patterns were invested inphosphate bonded investment in metal casting ring withdry cellulose paper ring liner. Following this they werecasted by lost wax technique in an induction castingmachine (Fig. 4) (Bego-Germany) with the respectivealloys. Metals used for recasting was obtained fromcleaned left over sprues and buttons of the alloys that hadbeen previously cast in group I. After bench cooling thecasting ring was divested and sandblasted using 250 lmaluminium oxide to remove the remnant investmentmaterial. Sprues were cut off and specimens were finishedand polished using carborundum discs, metal trimmers,rubber wheels, sandpapers and polishing cake using handmotor instruments. The polished disks were soaked in adetergent solution for 5 min and then scrubbed using a softbristle brush and rinsed under tap water for 5 min. Speci-mens were then replaced in sterile distilled water andcleaned by sonification and autoclaved at a temperature of150?C for 60 min.Elemental ReleaseSix disks of each alloy type from each group were trans-ferred to 6 ml of Dulbeccos modified eagle medium(DMEM) and incubated for 3 days at 37?C in an atmo-sphere of 5% CO2. DMEM is prepared by supplementingwith 5% new born calf serum, 100 U/ml of Penicillin,Streptomycin and 0.25 l gm/l Amphotericin B (Fig. 5).The media was analyzed for presence of Ni, Cr, Mo, Co,and Cu using an Inductively Coupled Plasma Mass Spec-trometry (ICPMS). Medium was diluted with de ionizedwater and kept in ICPMS and the readings were recorded.Triplicate absorbance was used to determine the meanconcentration of different elements in parts per billion(ppb) released from alloys.Fig. 1 NiCr alloys for metal ceramicJ Indian Prosthodont Soc (Apr-June 2011) 11(2):106112107123Cell Culture and Cytotoxicity TestFor Cytotoxicity test, the remaining 6 disks from variouscasting alloys in three groups were placed in center of a 24well tissue culture plate and 0.5 ml of mouse fibroblast cellsuspension was added to cell well (Fig. 6) and were left for2 h. Following this 0.5 ml of DMEM was added and cellswere incubated for 3 days at 37?C in an atmosphere of 5%CO2. The controls consisted of 6 wells containing cellswith no alloy specimens. After the incubation period theplates were removed from incubator and cytotoxicity ofTable 1 Description of NiCrdental cast alloys* Composition as provided bymanufacturerSerial No.Trade nameManufacturerComposition (wt %)*Code1Wiron 99Bego (Germany)Nickel-65AChromium-22.5Molybdenum-9.5Niobium-1Silica-1Iron-0.5Cesium-0.52CerametLaboline (Europe)Nickel-62BChromium-26Molybdenum-10Silica-1.5Others-0.53Hi Nickel CBHikari (Japan)Nickel-60CChromium-10Copper-15Manganese-7.9Others-7.1Fig. 2 Milled dieFig. 3 Wax patternsFig. 4 Cast specimensTable 2 Distribution ofspecimensGroupTypeNo. of alloy specimen(A) Wiron 99(B) Ceramet(C) Hi Nickel CBI100% New12A112B112C1II50% New50% recast12A212B212C2III100% Recast12A312B312C3108J Indian Prosthodont Soc (Apr-June 2011) 11(2):106112123materials was assessed by measuring Succinic Dehydro-genase activity (SDH) of the cells by using MTT assay.MTT reagent is added to the culture plate with alloyspecimens and it is transferred to 96 well plates for read-ings in Enzyme Linked Immunosorbent Assay (ELISA)reader, the protocol followed for the MTT Assay is sum-marized in Table 3.The readings were calculated by the formula:% Cell Viability Meanabsorbanceof sample ? 100Mean absorbance of control:Statistical AnalysisThe results obtained from the MTT analysis and ICPMSanalysis was subjected to statistical analysis. One wayANOVA was used to calculate the P-value. Multiple rangetests by TukeyHSD procedure were employed to identifythe significant groups at 5% level.ResultsElemental ReleaseElemental release was seen in all three casting alloygroups. Elements released were Ni, Cr, Co, Cu and Mo.Tables 4, and 5 summarize the elemental release by dif-ferent casted alloys in three casting procedures. Hi NickelCB had the highest amount of elemental release among thethree casting alloys followed by Ceramet and Wiron 99.Elemental release significantly increased with the per-centage of recast material used in for all elements analyzedin the study with P0.05 (Graph 1).Cytotoxicity ResultsThe percentage of viable cells in three groups is tabu-lated in Table 6. Mean percentages of cell activity ofthree base metal alloys for three casting conditions wereanalyzed and cytotoxicity was observed to be more in HiNickel CB, followed by Ceramet and Wiron 99. Resultsshowed that 100% recast alloys had more cytotoxicitythan 50% pure and 50% re-casted and 50% pure and50% re-casted alloy had more cytotoxicity than purealloy (Graph 2).DiscussionMetals have been an integral part of dental restorativeprocedures. Dental casting alloys which restore the formand function of missing tooth structure should be biologi-cally inert. Release of metallic elements from dental cast-ing alloys is a potential health problem 2, 8. Metal ionsleached from casting alloys are known to cause toxicinflammatory, allergic or mutagenic reactions 9, 10.These released elements have been detected by invitro andinvivo studies. An important consequence of elementrelease is its cytotoxic effect on adjacent tissue and theamount of tissue reaction depends upon element released.57, 11, 12.Fig. 5 Dulbeccos modified eagle medium (DMEM)Fig. 6 Tissue culture plate with 0.5 ml of mouse fibroblast cellsuspensionTable 3 Protocol for performing MTT assayStepAction1Plate cells at 1,000100,000 per well2Incubate for 624 h3Add 10 ll MTT reagent4Incubate for 24 h until purple precipitate is visible.5Add 100 ll detergent reagent6Leave at room temperature in the dark for 2 h7Record absorbance at 570 nmJ Indian Prosthodont Soc (Apr-June 2011) 11(2):106112109123The selection of an alloy for specific conditions likefixed partial dentures are influenced by three factorsnamely physical properties, bio-compatibility and cost.Gold considered as the high noble metal was the alloy ofchoice for restorative procedures and it was considered thatno ions leached from it but, histological studies disprovedthis misconception 2. High cost of gold has lead to theintroduction of base metal dental casting alloys 2, 3.Nickel combined with chromium forms highly corrosionresistant alloy, These base metal alloys which are primarilynickel based compared with gold alloys are cheaper, havehigh elastic modulus (stiffer), harder, less dense and pos-sess comparable resistance to tarnish and corrosion 1.Due to comparable physical properties base metals haveslowly replaced gold casting alloys 2, 3, 13, 14. Com-mercially available base metal alloys for fixed partialdentures are usually NiCr alloys 1, 2. The compositionof these alloys may vary according to manufacturer but thebasic constituents are Ni, Cr and Mo 1. Addition of minorcomponents significantly changes the microstructure andproperties which affect the bond strength of ceramic tometal oxide layer required for achieving bonding. It is atthe manufacturers discretion to include any of these minorcomponents to produce the desired properties 1.Table 4 Comparison of mean values of elemental release between different re-casted alloys in three casting groupsGroupVariableMaterialMean SDP-valueSignificant groups at 5% levelI100% Pure alloyA11.095 0.0520.0001 (sig)C1Vs A1and B1.B11.122 0.081C11.401 0.082II50% Pure50% re-casted alloyA23.674 0.2880.0001 (sig)C2Vs A2and B2.B24.408 0.231C24.865 0.296III100% Re-casted alloyA314.092 0.7390.0001 (sig)C3Vs A3and B3B314.727 2.028C314.944 2.301Table 5 The amount of various element released from casting alloys for three casting groups. (mean SD)ElementAlloyGroup IGroup IIGroup IIINiWiron 990.495 0.0102.901 0.16912.180 0.633Ceramet0.402 0.0123.664 0.39913.580 2.088Hi Nickel CB0.487 0.0903.354 0.29930.294 24.225CrWiron 990.071 0.0150.090 0.0210.222 0.077Ceramet0.346 0.0440.084 0.0140.108 0.076Hi Nickel CB0.265 0.0920.458 0.0910.471 0.104CoWiron 990.029 0.0080.074 0.0070.062 0.036Ceramet0.048 0.0210.035 0.0070.065 0.013Hi Nickel CB0.027 0.0100.436 0.1280.051 0.015MoWiron 990.501 0.0530.621 0.1181.629 0.195Ceramet0.343 0.0510.524 0.0840.941 0.055Hi Nickel CB0.416 0.0290.044 0.0310.143 0.042CuWiron 99CerametHi Nickel CB0.207 0.0560.573 0.1564.918 1.047Graph 1 Comparison of element release for three alloys110J Indian Prosthodont Soc (Apr-June 2011) 11(2):106112123The permissible leaching of these elements should beevaluated to prevent untoward side effects (cytotoxiceffects) during function. It has been a practice to furtherreduce the cost; the casted alloy is reused again in variousproportions with new alloy 3. The elemental release ofthis re-casted alloy may vary from the pure virgin alloy.The biocompatibility of the alloy depends upon the typeand elemental release from it, into surrounding medium ortissues 5, 15.Toassesstheelementreleasedfromthealloys,thealloyisstored in a suitable medium such as artificial saliva for3 months or in a suitable culture medium and incubated for3 days1619.Storingthespecimeninculturemediumandincubating it is a practical method as the procedure requiresshorter span of time and the elements released were alsobetter 16. Further to evaluate the amount of elementsreleased into the medium various methods have been putforth, such as Atomic Absorption spectrography, Emissionspectrography, Inductively Coupled Plasma Atomic Emis-sion Spectrophotometer (ICPAES), Inductively CoupledPlasma Mass Spectrometry (ICPMS) 20. ICPMS is fast,sensitive, precise and accurate multi element analyticaltechnique for determination of trace elements.The common methods used to evaluate cytotoxicity areMillipore filter, Agar overlay test, MTT assay test. MTTassay is an easy technique; the readings can be calculateddirectly from ELISA reader 16. The other advantages ofMTT are sensitive and reproducibility, convenient, rapid-ity, elimination of need of radioactive compounds andeconomical.Three NiCr based alloys (Wiron 99, Ceramet and HiNickel CB), commonly used for the fabrication of metalceramic fixed partial dentures from different popularmanufacturing companies were chosen due to the variationintheircompositionclaimedbythemanufacturers.Cleaning and sterilization of specimens were performedaccording to recommended protocols. Specimens wereautoclaved 150?C for 60 min prior to testing to sterilizethem 1, 16. It is important to note that this procedure mayaffect the corrosion pattern of these alloys, however all thealloy specimens received the same treatment, thus anydifferences in cytotoxicity of elemental release would beresult of differences in type and composition of alloys orthe casting procedures.The findings of the current study agreed with thehypothesis that recasting of base metal alloys increasestheir potential cytotoxic effect and element release. In thestudy, element release in all the new alloy samples wassignificantly less than the re-casted specimens. Amongstthe three alloys selected Hi Nickel CB had significantlyhigher elements released compared to Ceramet and Wiron99 in pure alloy, 50% recast and 100% recast alloys. Wiron99 showed least element release in 100% pure alloy, 50%recast and 100% recast specimens. All the base metalalloys tested in this study showed to have a cytotoxiceffect.In the cytotoxic evaluation done by analyzing livingcells and percentage of cell viability it was seen that in100% pure alloy specimens Wiron 99, Ceramet and HiNickel CB were cytotoxic in the increasing order. Withrecasting of alloys either with 50% or 100% showed adefinite decrease in the number of living cells in all thethree alloys. In the present study in 50% new50%re-casted and 100% re-casted, the mean of living cells andpercentage of cell viability are more significant in Wiron99 than Ceramet and Hi Nickel CB. Hi Nickel CB showedleast number of viable cells.Among NiCr alloys chosen Hi Nickel CB was mostcytotoxic and it was significantly more cytotoxic thanCeramet and Wiron 99. This could be related to the dif-ference in the composition of these alloys 1, 3. Thegreatest cytotoxicity showed by the Hi Nickel CB alloy forall the three casting conditions could be due to its coppercontent. It has been reported in the literature that the majorcontribution for toxicity of alloys was probably due tocopper content 1. It has been reported that only NiCrTable 6 Mean values for percentage of cell viability for three castinggroupsGroup% of alloyMaterialPercentage ofviable cells (%)I100% pureA162.342B161.322C160.593II50% pure50% re-castedA258.699B256.494C252.668III100% re-castedA353.101B352.195C347.556%Cell ViabilityGraph 2 Percentage of cell viabilityJ Indian Prosthodont Soc (Apr-June 2011) 11(2):106112111123alloys containing 1627% Cr develop an adequate protec-tive oxide layer. Molybdenum also has an active role in theformation of oxide layer. Since copper based alloys tarnishand corrode more than non copper alloys, it was observedin the present study that a remarkable amount of copperwas released into culture medium from Hi Nickel CB. Thecontent of copper in association with low content of Cr andabsence of molybdenum may also explain significantcytotoxic effect of this alloy in comparison to other NiCralloys 1, 3, 17. Thus for all of the alloys 50% recastgroups were significantly more cytotoxic than 100% newalloy groups and furthermore, the 100% recast groups weresignificantly more cytotoxic than 50% recast group. Thiscould be due to some effect on the chemical composition ofthese alloys which may increase the dissolution rate of thealloys, and thus the elements released from them will beincreased as found in ICPMS analysis. From the results ofpresent study it appears that the alloy types and the ele-ments of these alloys become affected to a different degreewhen the alloy was recast and hence attributes to itscytotoxic effects.LimitationsThe results of the study need to be correlated consideringthe following limitations. The minerals or organic con-stituents in DMEM media used may have an effect oncorrosion susceptibility of the alloys and thus influence theelement release. Although a small sample size (n = 6) wasused in the current study, significant differences werefound between the different groups, indicating its suffi-ciently large effect size. However further studies need to beconducted with greater sample size for a more adequaterepresentation of the alloy types.ConclusionsThe results obtained from the study prove hypothesis thatrecasting of base metal alloys affect their elemental releaseand subsequ
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