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 Bowing to the dental products industry, FDA has, for the first time in memory, withdrawn a warning about neurological harm to children and the unborn.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.

    美國衛生當局星期二提出嚴格安全控制水銀牙齒填充料的使用。

    美國食品藥品管理局現將這些填料分類為二級器材，可產生中度危險。二級器材使用通常要采取一些保護措施。但是美國衛生官員通知這種填料不會對大多數人造成傷害。

    "與水銀有關的健康不良事件，不會使病人長期處于危險之中。"美國食品藥物管理中心，設備與放射健康部，感染控制和牙齒器材，綜合醫院麻醉科代理主任蘇三 蘭納爾醫生在星期二下午記者招待會上說，"在過去20年僅有141例不良事件報告，沒有導致死亡。"

    代理機構介紹下列標志性的改變：警告，反對水銀過敏病人使用這種填料；當處理填充材料時，警告，牙科專家使用足夠的通氣設備；和一個關于汞合金牙齒的益處與危險的科學證據討論報告書。

    "我們沒有禁止任何病人使用牙齒汞合金填料（除了過敏者以外）"蘭納爾在記者招待會解釋。

    此新規定帶來了消費者牙齒選擇組織，消費者的憤怒。

    "食品藥物管理局食言，我收到了侮辱，"組織的國家級法律顧問查理斯。布朗說"他們一年前在網站發出警告，并承諾在網站上保留那些警告，警告其對兒童和胎兒的神經性損害。在記憶中這是第一次，偏向牙齒生產工業，食品藥物管理局撤銷了關于對兒童及胎兒神經損害的警告。這是對低收入者和少數兒童的一種蔑視態度，因為他們才是用汞制牙的人。有錢人用則用樹脂的。"

    機構的最新進展經歷慢長的爭論過程，關于這些填料的推測性危險，它覆蓋2006年許多消費組織反對FDA的訴訟文件，包括媽媽反對汞和牙齒選擇消費者。

    作為解決的部分，2009年7月28日FDA 同意分類水銀填料，也被稱為牙齒汞合金，并在網站發布通告說："牙齒汞合金包含水銀，它可能對正在發育中的兒童和胎兒的神經系統有神經毒性效果。"

    美國牙齒學會（ADA）,一個期望二級分類組織，支持FDA 行動。

    "FDA 留下這個關于牙齒治療的討論給牙醫和病人，"ADA 總裁約翰。凡德烈在已準備好的聲明中指出，"這項決定得到ADA的長久支持--在牙醫和病人間關于全范圍治療的討論，幫助病人對牙齒護理作出經驗性的決斷。

    "現在它是令人混淆的，因為（汞）根據它的成份不同而被分類。被包裹的汞作為一個單位起作用，因此它有意義。"ADA消費者顧問埃德蒙。 哈瓦勒和加州大學洛杉磯分�？谇粚W院助理教授，在裁定前說。"期望特別控制是有理由的，像預防高血壓或預防汞過敏一樣并恰當的為牙科人員提供指導。"

    被包裹的汞包含兩個部分，金屬合金和水銀，他們被分開遞送，到牙醫辦公室后混合，FDA 牙產品委員會成員麥克。弗萊明說。

    弗萊明強調，他沒說代表FDA.

    代表在2006年會面回顧這個問題，沒有發現汞不安全。"我們說你們沒有根據FDA 制定的文件作出安全決定。"弗萊明說，"ADA 還沒有宣布并說它對孕婦和兒童不安全，但我們需要更多信息。"哈瓦雷特補充道。

    弗萊明說裁定前他期望FDA采納委員會的建議，包括確保病人知道產品內含水銀并加強對孕婦和育齡婦女預防保護。

    但蘭納爾說FDA 發現"母乳中水銀的濃度值低于環保協會保護量。FDA 認為母親的汞牙齒填料不會使嬰兒處于危險。"

    汞牙包含元素汞與其它金屬像銀，銅，錫，鋅結合。這些填料，含大約50%的汞，已經被幾代人用來穩固腐爛的牙齒。牙科專家抗爭汞受到其他金屬的約束，被包裹不會形成健康危險。然而，消費組織抗爭道汞已知具有神經毒性，以水銀蒸氣形式漏出，然后進入血流。

    然而，蘭納爾星期二說"暴露于汞牙的水銀蒸氣中，不會使6歲和以上的人有危險。"

    據ADA 統計，汞的使用在減少。1990年汞牙占牙齒復原的67.6%, 但到1999年占45.% , 2003年估計占30%.以前用汞填料治療空洞，現在大多數用合成樹脂填充。

    許多國家已經禁止使用或建議反對使用汞填料。