U.S. health authorities on Tuesday placed tighter safety controls on the use of mercury dental fillings.

The U.S. Food and Drug Administration will now categorize the fillings as Class II devices, which puts them into the middle range of risk. Class II devices usually carry some kind of precautions regarding their use.

But U.S. health officials noted that the fillings pose no real harm to most people.

"Patients are not at risk for long-term, mercury-related adverse health events," Dr. Susan Runner, acting director of the Division of Anesthesiology, General Hospital, Infection Control and Dental Devices, part of the U.S. Food and Drug Administration's Center for Devices and Radiological Health, said during a news conference Tuesday afternoon. "There have only been 141 adverse event reports over 20 years. None resulted in death."

The agency did recommend the following labeling changes: a warning against the use of these fillings in patients with mercury allergy; a warning that dental professionals use adequate ventilation when handling the material for the fillings; and a statement discussing the scientific evidence on the benefits and risks of dental amalgam.

"We're not contraindicating dental amalgam in any patient group [other than those who have allergies]," Runner noted during the news conference.

The new ruling brought an angry reaction from the consumer organization Consumers for Dental Choice.

"I'm outraged. FDA broke its word," said Charles Brown, the group's national counsel. "They put a warning a year ago on the web site and promised to keep those warnings on the web site that warned of neurological damage to children and unborn children. Bowing to the dental products industry, FDA has, for the first time in memory, withdrawn a warning about neurological harm to children and the unborn. It's a contemptuous attitude toward lower income and minority children because they're the ones that get amalgam. The rich get resin."

The agency's latest move follows a lengthy debate on the supposed dangers of these fillings, which was capped by a lawsuit filed in 2006 against the FDA by several consumer groups, including Moms Against Mercury and Consumers for Dental Choice.

As part of that settlement, the FDA agreed to classify mercury fillings, also known as dental amalgam, by July 28, 2009, and posted a notice on its Web site that said: "Dental amalgams contain mercury, which may have neurotoxic effects on the nervous systems of developing children and fetuses."

The American Dental Association （ADA）, one of the organizations that had expected a Class II classification, supported the FDA action.

"The FDA has left the decision about dental treatment right where it needs to be -- between the dentist and the patient," the ADA's president, Dr. John Findley, said in a prepared statement. "This decision underscores what the ADA has long supported -- a discussion between dentists and patients about the full range of treatment options to help patients make educated decisions regarding their dental care."

"Right now, it's confusing because [amalgam] is classified according to its different components. The encapsulated amalgam functions as a unit, so it just makes sense," Dr. Edmond Hewlett, an ADA consumer advisor and an associate professor at the UCLA School of Dentistry, said before the ruling. "And it's reasonable to expect special controls such as precautions for people who are hypersensitive or are allergic to amalgam as well as proper handling guidelines for dental personnel."

Encapsulated amalgam contains two parts, a metal alloy as well as mercury, which are delivered in separate sections that are mixed after they have been delivered to the dentist's office, said Dr. Michael Fleming, a member of the FDA Dental Products Panel.

Fleming emphasized that he was not speaking on behalf of the FDA.

The panel, which met in 2006 to review the issue, did not find that amalgam was unsafe. "We said you can't make a determination of safety based on the documents the FDA produced," Fleming said.

"The ADA has not come out and said it is unsafe in pregnant women and children, but that we need more information," Hewlett added.

Fleming said before the ruling that he expected the FDA to incorporate the committee's recommendations, which included making sure that patients be informed of the mercury content of the product and beefing up precautions for pregnant women and women of child-bearing age.

But Runner said the FDA found that "…concentrations of mercury in breast milk is an order of magnitude lower than EPA protective dose. FDA does not believe that maternal dental amalgam fillings put infants at risk."

Dental amalgam contains elemental mercury combined with other metals such as silver, copper, tin and zinc. The fillings, about 50 percent mercury, have been used for generations to stabilize decaying teeth. Dental experts contend that when mercury is bound to the other metals it's encapsulated and doesn't pose a health risk. Consumer groups, however, contend that mercury, a known neurotoxin, does leak out in the form of mercury vapor and then gets into the bloodstream.

However, Runner said Tuesday that "exposure to mercury vapor from dental amalgam do not put individuals age 6 and older at risk."

According to the ADA, the use of amalgam is declining. In 1990, dental amalgams made up 67.6 percent of all dental restorations, but by 1999 it was 45.3 percent and, in 2003, an estimated 30 percent. Cavities that previously would have been treated with dental amalgam are now mostly filled with a resin composite.

Several countries have already either banned or advised against the use of mercury fillings.

美国卫生当局星期二提出严格安全控制水银牙齿填充料的使用。

美国食品药品管理局现将这些填料分类为二级器材，可产生中度危险。二级器材使用通常要采取一些保护措施。但是美国卫生官员通知这种填料不会对大多数人造成伤害。

"与水银有关的健康不良事件，不会使病人长期处于危险之中。"美国食品药物管理中心，设备与放射健康部，感染控制和牙齿器材，综合医院麻醉科代理主任苏三 兰纳尔医生在星期二下午记者招待会上说，"在过去20年仅有141例不良事件报告，没有导致死亡。"

代理机构介绍下列标志性的改变：警告，反对水银过敏病人使用这种填料；当处理填充材料时，警告，牙科专家使用足够的通气设备；和一个关于汞合金牙齿的益处与危险的科学证据讨论报告书。

"我们没有禁止任何病人使用牙齿汞合金填料（除了过敏者以外）"兰纳尔在记者招待会解释。

此新规定带来了消费者牙齿选择组织，消费者的愤怒。

"食品药物管理局食言，我收到了侮辱，"组织的国家级法律顾问查理斯。布朗说"他们一年前在网站发出警告，并承诺在网站上保留那些警告，警告其对儿童和胎儿的神经性损害。在记忆中这是第一次，偏向牙齿生产工业，食品药物管理局撤销了关于对儿童及胎儿神经损害的警告。这是对低收入者和少数儿童的一种蔑视态度，因为他们才是用汞制牙的人。有钱人用则用树脂的。"

机构的最新进展经历慢长的争论过程，关于这些填料的推测性危险，它覆盖2006年许多消费组织反对FDA的诉讼文件，包括妈妈反对汞和牙齿选择消费者。

作为解决的部分，2009年7月28日FDA 同意分类水银填料，也被称为牙齿汞合金，并在网站发布通告说："牙齿汞合金包含水银，它可能对正在发育中的儿童和胎儿的神经系统有神经毒性效果。"

美国牙齿学会（ADA）,一个期望二级分类组织，支持FDA 行动。

"FDA 留下这个关于牙齿治疗的讨论给牙医和病人，"ADA 总裁约翰。凡德烈在已准备好的声明中指出，"这项决定得到ADA的长久支持--在牙医和病人间关于全范围治疗的讨论，帮助病人对牙齿护理作出经验性的决断。

"现在它是令人混淆的，因为（汞）根据它的成份不同而被分类。被包裹的汞作为一个单位起作用，因此它有意义。"ADA消费者顾问埃德蒙。 哈瓦勒和加州大学洛杉矶分校口腔学院助理教授，在裁定前说。"期望特别控制是有理由的，像预防高血压或预防汞过敏一样并恰当的为牙科人员提供指导。"

被包裹的汞包含两个部分，金属合金和水银，他们被分开递送，到牙医办公室后混合，FDA 牙产品委员会成员麦克。弗莱明说。

弗莱明强调，他没说代表FDA.

代表在2006年会面回顾这个问题，没有发现汞不安全。"我们说你们没有根据FDA 制定的文件作出安全决定。"弗莱明说，"ADA 还没有宣布并说它对孕妇和儿童不安全，但我们需要更多信息。"哈瓦雷特补充道。

弗莱明说裁定前他期望FDA采纳委员会的建议，包括确保病人知道产品内含水银并加强对孕妇和育龄妇女预防保护。

但兰纳尔说FDA 发现"母乳中水银的浓度值低于环保协会保护量。FDA 认为母亲的汞牙齿填料不会使婴儿处于危险。"

汞牙包含元素汞与其它金属像银，铜，锡，锌结合。这些填料，含大约50%的汞，已经被几代人用来稳固腐烂的牙齿。牙科专家抗争汞受到其他金属的约束，被包裹不会形成健康危险。然而，消费组织抗争道汞已知具有神经毒性，以水银蒸气形式漏出，然后进入血流。

然而，兰纳尔星期二说"暴露于汞牙的水银蒸气中，不会使6岁和以上的人有危险。"

据ADA 统计，汞的使用在减少。1990年汞牙占牙齿复原的67.6%, 但到1999年占45.% , 2003年估计占30%.以前用汞填料治疗空洞，现在大多数用合成树脂填充。

许多国家已经禁止使用或建议反对使用汞填料。