"It will lead to urticaria, but it will endanger renal function ..." Recently, an online post "Nickel-chromium porcelain teeth can cause kidney disease" has aroused widespread concern.
Yesterday, the investigation of this rumor reached an authoritative conclusion for the first time. The Oral Materials Committee of the Chinese Stomatological Association published the article "Biological Safety of Nickel-Chromium Alloy for Porcelain Restoration" (hereinafter referred to as "Safety") on the website of Chinese Stomatology. The article concludes that Ni-Cr alloy will bring side effects to a few patients who wear Ni-Cr alloy porcelain crowns, but most of them are confined to the oral cavity, causing few systemic reactions and extremely rare damage to important organs of the body.
Suspense 1 Will Ni-Cr porcelain teeth cause kidney disease?
There is no evidence to solve the problem of kidney disease caused by rare allergic reactions.
The article "Investigation on the Restoration of Nickel-Chromium Alloy Porcelain in Major Stomatological Hospitals in China" published by China Stomatology Network yesterday pointed out that after receiving the authorization from the State Medical Products Administration, the Chinese Stomatological Association recently entrusted Feng, director of the Prosthodontics Department of Peking University Stomatological College, to urgently investigate the use of nickel-chromium porcelain teeth in the prosthodontics departments of eight stomatological hospitals with great influence in China, such as West China Stomatological Hospital of Sichuan University and Stomatological Hospital of the Fourth Military Medical University.
"According to preliminary statistics, since the introduction of Ni-Cr porcelain teeth in China in the late 1970s, about 900,000 Ni-Cr alloy porcelain crowns have been produced by the above eight units, of which only 5 cases may cause allergic reactions, and no cases leading to kidney diseases have been seen." Feng said that there is no evidence to prove the causal relationship between Ni-Cr porcelain teeth and renal damage.
The article "Safety" points out that the incidence of nickel allergy in women reported in the literature is much higher than that in men, which is 10%~30%, while that in men is 1%~3%. This may be because women are more exposed to nickel-containing jewelry, which makes people allergic.
Liu Li, director of the prosthodontics department of the Stomatological Hospital affiliated to Zhejiang University School of Medicine, told the Morning Post reporter that she had never heard of it before, but it is certain that there have been very rare cases of nickel-chromium alloy allergy.
Feng suggested that patients who are worried about kidney disease due to the installation of nickel-chromium porcelain teeth can go to medical institutions for comprehensive and detailed examination, and invite experts in kidney disease, toxicology, internal medicine, nutrition and occupational diseases for consultation.
Suspense why does Ni-Cr alloy have side effects?
Nickel released by alloy is absorbed by human body, but generally it will not cause harm to human body.
Zhao Xinyi, chairman of the Oral Materials Committee of the Chinese Stomatological Association, pointed out that for most people who use Ni-Cr alloy teeth, Ni-Cr alloy has good biological safety, but it will have some side effects for a few patients. The main cause of side effects is the nickel ions released by long-term corrosion of nickel-chromium alloy in saliva as a weak acidic electrolyte.
The article "Safety" also points out that studies show that brushing teeth with toothpaste can also significantly increase the release of nickel-nickel alloy in the mouth.
Zhao Xinyi said that most of the nickel released from the Ni-Cr alloy teeth will be swallowed into the digestive tract and will not accumulate in the mouth. Moreover, the amount of nickel released by nickel-chromium alloy is obviously lower than the amount of nickel ingested in people's diet. However, a small amount of nickel will still be absorbed by the human body. Although the nickel content in blood, saliva and urine will increase within a certain period of time when patients wear Ni-Cr alloy teeth, it is generally within a safe range and will not cause harm to human body. Zheng Gang, director of the Oral Materials Research Office of Peking University College of Stomatology, also said that nickel can be excreted through metabolism.
"Nickel is an essential element for human body and has many beneficial effects on human health," said Xu Jun, deputy director of the Department of Prosthodontics, Peking University College of Stomatology. "In fact, a lot of articles in our real life, such as pots and pans, contain nickel."
According to a rough estimate by the World Health Organization, the daily intake of nickel is 100 to 600 micrograms. Under normal circumstances, the nickel content in adults is about 10 mg.
Suspense 3: Is it necessary to remove the installed nickel-chromium teeth?
There is no need to panic when solving doubts and doubts, and don't blindly disassemble them.
Since the Ni-Cr porcelain tooth storm, many people have gone to the hospital to ask for the original Ni-Cr porcelain tooth to be pulled out. Liu Li said that for patients who are worried about the disease caused by nickel and chromium, hospitals generally do not advocate patient replacement, because the removal of porcelain teeth has unpredictable factors, which may cause damage to teeth. If there are abnormal symptoms, you should go to the hospital to find out the reason first.
"Don't be too alarmed. As long as they are installed in regular hospitals, the nickel-chromium porcelain teeth produced by regular manufacturers are products certified by the State Administration of Medical Supplies. Patients should pay attention to that if it is a nickel-chromium porcelain tooth with a price of one or two hundred yuan, it is likely to be produced through informal channels. Because of the individual differences of patients, after the restoration of nickel-chromium or other porcelain-fused-to-metal restorations, there may be color infiltration at the edge of the crown and neck, gingival gray lines and mild gingivitis, which are normal. " Liuli said.
"If patients are allergic to nickel-chromium porcelain teeth, they will react in a short time after dental implantation, mainly skin allergies and periodontitis; If there are no such symptoms in a few years, there will be no danger of sensitivity. " Feng said that if patients think it is necessary, they can also go to the allergy departments set up in some hospitals to conduct nickel allergy tests in advance.
Wang Xing, president of the Chinese Stomatological Association, pointed out that nickel-containing materials have been used in oral cavity for nearly a hundred years, and nickel-chromium alloy has been used in making porcelain teeth for more than 30 years, which is a relatively mature dental restoration material.
Suspense 4 should nickel-chromium porcelain teeth be banned?
Choosing precious metal porcelain teeth to solve doubts is not in line with China's national conditions.
The article "Safety" points out that at present, some western countries still use nickel-chromium alloy in the dental field. For example, in 2005, Japanese national standards still listed nickel-chromium alloy as an alloy material for clinical use, and it was included in the national insurance plan, and the insurance company paid the expenses; The US Food and Drug Administration also listed Nickel-Chromium alloy as a dental alloy that can be used in clinic.
Why use nickel-containing alloy when it is known that nickel has certain side effects? The article "Safety" lists three reasons: First, few people are allergic to nickel, and they are generally allergic to skin contact, such as bracelets and necklaces. Allergies caused by contact with the mouth are very rare; Secondly, Ni-Cr alloy has good mechanical properties and corrosion resistance, and it has good operability when used to manufacture dentures. In these aspects, besides precious metals, it can be said that nickel-chromium alloy is the best choice; Third, the price is cheap, which can make more people get more satisfactory dental restoration.
Wang Xing said that at present, nickel-chromium porcelain teeth occupy almost 80% of the porcelain teeth market in the domestic market. At present, the price of precious metal porcelain teeth is more than twice that of nickel-chromium porcelain teeth, while all-ceramic teeth are three to four times that of nickel-chromium porcelain teeth.
"Patients should choose the right products according to their own economic ability and aesthetic requirements. If nickel-chromium porcelain teeth are completely abandoned, the manufacturers and distributors of medical devices will ultimately benefit, as will hospitals and doctors. Only the people suffer. " Wang Xing said. (Oriental Morning Post reporter Lu Mei comprehensive report)
◎ Dialogue
Nickel-chromium porcelain alloy for dentistry is "relatively safe"
Oriental Morning Post reporter Lu Mei
Interviewee: Professor Liuli, director of prosthodontics department of Stomatological Hospital affiliated to Zhejiang University School of Medicine, has been engaged in prosthodontics research for nearly 30 years and published more than 50 papers in domestic core magazines. On February 13, the netizen "People Need the Truth" published a post entitled "The use of Ni-Cr heavy metal porcelain teeth should be banned", which quoted Professor Liuli's comments on the application status and existing problems of dental alloys.
The proportion of patients using Ni-Cr alloy porcelain teeth decreased year by year.
Oriental Morning Post: Under normal circumstances, who will choose Ni-Cr porcelain teeth?
Liu Li: Nickel-chromium porcelain teeth are divided into two parts: metal and porcelain crown. According to the current national medical supplies administration standard, the main component of nickel-chromium porcelain teeth is nickel, accounting for 69% ~ 77% of the weight of metal parts; The weight ratio of chromium is between 13% and 16%. In addition, it also contains other metals such as molybdenum, and there are subtle differences among manufacturers.
1970s Ni-Cr alloy porcelain teeth began to enter China. At that time, because it was very rare, it was generally only used for teaching. /kloc-0 was gradually used in clinic in the 1990s, and precious metal porcelain teeth began to appear in the late 1990s. At present, Ni-Cr porcelain teeth are relatively cheap, basically in 500 yuan/tooth, which is accepted by patients with low living standards but installation needs.
Oriental Morning Post: What percentage of porcelain teeth are made of nickel-chromium porcelain?
Liuli: The proportion is decreasing year by year. I checked the consumption of 1 in our hospital and February this year, and found that about 1/4 of the total number of fixed restorations were porcelain teeth with nickel-chromium alloy.
In recent years, the use of precious metals, all-ceramic crowns and other materials is increasing, which is directly related to the improvement of living standards. In underdeveloped areas, the demand for Ni-Cr porcelain teeth is still great.
At present, there is no perfect material in the field of dental restoration.
Oriental Morning Post: How about the use of nickel-chromium porcelain teeth abroad?
Liu Li: As far as I know, nickel-chromium porcelain teeth are still used abroad. It's not that it's banned because of its high toxicity, but it's really rare in Europe, and the reason is similar to what I said before-being replaced by other products with better performance, and the cost is within the patient's ability. Regardless of the price, precious metal or all-ceramic crown is certainly better than nickel-chromium alloy, but this does not mean that nickel-chromium porcelain teeth are unsafe. As long as they are produced and sold through formal channels, the Ni-Cr porcelain teeth certified by the State Administration of Medical Supplies are relatively safe.
Oriental Morning Post: What do you mean by "relative safety"?
Liuli: There is no absolute safety in the medical field, and there is no perfect material in the field of dental restoration at present. However, taking Ni-Cr alloy porcelain teeth as an example, we must pass several biological tests stipulated by national standards before we can get permission to enter clinical application. As doctors, we believe that the materials of porcelain teeth with three certificates (registration certificate, production license and distribution license of the State Medical Supplies Administration) are relatively safe, that is, the materials and products have the nature of pre-clinical safe use.
To be sure, there have been very rare cases of nickel-chromium alloy allergy.
Oriental Morning Post: Is it impossible for "relatively safe" Ni-Cr alloy porcelain teeth to cause disease?
Liu Li: No, in 2002, after consulting domestic and foreign literatures, He Fuming and I co-authored the book "Application Status and Existing Problems of Dental Alloys" and published it in the magazine "Dental Materials and Instruments". Among them, 4 allergic cases were found in the literature: 1994, 2 cases of "pustulosis of palm and sole" caused by dental alloy reported in Japan; There are 1 case of palmoplantar pustulosis caused by Ni-Cr alloy fixed denture and 1 case of allergic stomatitis caused by Ni-Cr alloy in China. Whether nickel-chromium porcelain teeth can cause kidney diseases or other diseases has never been heard before, but it is certain that there have been very rare cases of nickel-chromium alloy allergy.
Oriental Morning Post: Since there have been cases of Ni-Cr alloy allergy, will the hospital explain to the patients that allergies may occur during the operation?
Liuli: Nickel-chromium alloy allergy is an example after all, which has not been reported as a routine project in China before. As doctors, we hope to communicate with patients as much as possible and inform them in advance, but because nickel-chromium alloy is relatively cheap, it is easy to be misunderstood as "deliberately selling high-priced precious metal porcelain teeth". If the patient tells the doctor that he is allergic, the doctor will carefully select the materials with the patient. However, it may be considered to be included in the notification project in the future.