評論
打印
Science and technology
科學技術
Dental X-rays
牙科X光
Little and not often, please
請不要太頻繁,一點就好
Confirmation that dental X-rays can be bad for you
已證實牙科X光對你是有危害的
If you are a suspicious type you may be disturbed by the fact that, despite reassurances of the safety of the procedure, dentists and their technicians, when administering X-rays, usually step out of the room while the deed is done.
盡管牙科X光實施程序的安全已得到了證實，牙醫和技工們還是會在拍X光時離開房間。如果你是一個多疑的人，這樣的事實可能會困擾你。
Not only that, they often drape a lead-lined apron over your body to protect your vital organs. Well, all but one: your brain.
不但如此，在拍X光時他們還經常用鉛襯的圍裙蓋住你的身體以保護重要器官—但是是除了大腦以外的所有器官。
A study by Elizabeth Claus, of Yale University, just published in Cancer, suggests your suspicions might be justified.
耶魯大學的伊麗莎白. 克勞斯醫生的一項研究結果剛在癌癥雜志上發表。此項研究表明你的懷疑可能并非杞人憂天。
Dr Claus thinks she has identified, in those who have had dental X-rays often, a significant rise in the admittedly small risk of developing a brain tumour.
克勞斯醫認為她已發現那些經常拍牙科X光的病人得腦瘤的風險確實有顯著升高。
In rich countries, five men in every 200,000, and twice as many women, develop tumours called meningiomas that affect the membranes surrounding the brain.
在富裕的國家里，每200，000人中就有5名男性得一種叫腦脊膜瘤的腦瘤，此瘤破壞腦膜，而且發病的女性人數是男性的兩倍。
Meningiomas account for a third of primary brain tumours.
腦脊膜瘤的患者占原發性腦瘤患者的三分之一。
Only about 2% of them are malignant, but non-malignant does not mean non-dangerous.
只有2%的腦脊膜瘤是惡性的，但是非惡性并不代表沒有危險。
Even a benign meningioma can kill.
即使是良性的腦脊膜瘤也會至死。
Around 30% do so within five years of diagnosis. Symptoms can include seizures and blindness, and treatment may involve surgery, chemotherapy or, ironically, radiotherapy.
大約30%的至死病例是發生在確診后5年。這種腦瘤的癥狀包括:痙攣和失明，可以通過手術，化療，或者用放射療法來進行治療。
Ironically, because past research studying the after-effects of exposure to things like atom bombs and radiation treatments for cancer suggests the most important environmental risk factor for meningiomas is ionising radiation.
諷刺的是，對人體暴露于類似原子彈輻射和癌癥放射療法的后果的研究顯示，產生腦脊膜瘤的最主要的環境風險因素是離子輻射。
These days, however, the main source of ionising radiation for most people is neither fallout from bombs nor radiotherapy; it is dental X-rays.
然而，現今影響大多數人的離子輻射的主要源頭既不是原子彈的輻射塵埃也不是放射療法，而是牙科X光。
Despite that, surprisingly little research has been done on those X-rays' effects.
盡管如此，令人驚訝的是幾乎沒有牙科X光對人類影響的研究。
Dr Claus and her colleagues have tried to plug the gap.
克勞斯醫生和她的同事們已在努力填補這一空白。
They studied 1,433 Americans who have had meningiomas and compared them with 1,350 others who have not.
他們研究了1433名美國的腦脊膜瘤患者，并把他們與1350名非患者進行對比。
These others were chosen to match the study group's age profile, sex ratio and dwelling place.
這些被選擇的非患者構成符合研究所需的年齡組成，性別比例和所在居住地。
The researchers then inquired about both groups' family, medical and dental histories.
研究人員獲取了這兩組研究對象的家庭，病史，和牙病史的數據。
In the case of their dental histories, participants were asked whether they generally had standard X-rays, known as bitewings, every year, or never had them, or fell somewhere in between.
對于牙病史，參與者被問及他們是否通常每年接受常規的牙醫X光，或是從沒拍過，或是介于以上兩者之間。
They were also asked how often they had had panoramic X-rays—so-called panorexes—taken of their entire mouths, and whether they had ever had braces, the fitting of which often involves a panoramic X-ray.
他們還被問及拍全頜x光—對整個口腔拍攝X光的經常性，以及是否做過牙齒整形—通常是會要求拍全頜x光。
The researchers found that people who had had a meningioma were more than twice as likely as those who had not to have had at least one bitewing X-ray.
研究發現患腦脊膜瘤的病人發病的可能性是那些沒拍過咬翼片的人的兩倍以上。
And the more bitewings they had been given, the greater that likelihood was.
拍咬翼片次數越多的人，可能性越大。
Even more troubling was the finding that people who had been given a panorex when they were under ten had 4.9 times the normal risk of developing a meningioma.
更讓人擔憂的發現是十歲以下拍過全頜x光的人患腦脊膜瘤的概率是正常風險值的4.9倍。
To be fair, only 22 participants in the study had both had a panorex and developed such a tumour.
公平地說，只有22名研究參與者拍過全頜x光并患有腦脊膜瘤。
But according to Dr Claus, the panorex was not common when most of the people in the study had been children.
但據克勞斯醫生說，以前研究對象大部分是兒童，拍全頜x光的現象并不普遍。
Nowadays, she says, before getting braces all the kids have it.
如今，她說，在牙齒整形之前所有兒童都拍過全頜x光了。
What these results mean in practice is debatable.
以上研究發現的實際意義還是有爭議的。
The radiation dose from an individual dental X-ray, Dr Claus points out, has gone down by about half over the past 30 years or so.
克勞斯醫生指出，單次牙醫X光的輻射劑量已在過去的30年降低到原來的一半左右。
In addition, some dentists and orthodontists—though far from the majority—have turned to digital methods that expose patients to even lower levels. But others are using fancy new techniques like cone-beam computerised tomography which actually expose people to much higher levels of radiation.
另外，一些牙科醫生和整牙醫師—雖然并不占多數，已轉用電子手段，這就更大程度的降低了病人所受的輻射程度。
Moreover, guidelines from the American Dental Association state that healthy adults should have a bitewing X-ray no more than once every two or three years, and that there is little reason to X-ray patients who do not have symptoms.
此外，美國牙科協會的指南規定健康成年人每兩到三年不應拍超過一次的咬翼片，并且沒有理由給無病癥的病人拍X光。
These are policies which Dr Claus describes as quite reasonable.
克勞斯醫生認為這些政策是很合理的。
But if what her participants told her is true, not all dentists are heeding their own professional body's advice.
如果研究參與者所告知的都是事實的話，可見并不是所有牙科醫生都留心自身的建議。
Most of those who took part in the study reported having at least one X-ray a year.
大多數參與研究的人表示一年至少拍了一次x 光。
Dr Claus's work, then, is a timely reminder that X-rays are dangerous, that dentists should use them sparingly and that patients who have suspicions about their use are not necessarily paranoid.
克勞斯醫生的工作及時地提醒了我們，拍x光是有危險的，牙醫應該保守地使用它們，這樣看來病人們對x光的疑慮并不是所謂的妄想。
