| Porcelain fused to metal crown (PFM) is a kind of crown prosthesis whose cast metal crown is veneered with a layer of fused porcelain. By the cost of metal alloy, PFM can be difficienate as noble metal alloy and base metal alloy. Nickel (Ni)-Chromium(Cr) based PFM is one of the most popular fixed-restorations. Due to its low-cost, it has been widely used in our country. According to the incomplete statistics, the occupation rate of Ni-Cr based PFM was about50-80%in the total market of PFM approximately, which means more than ten millions of Chinese had Ni-Cr based PFM. In the recent years, the biocompatibility of Ni-Cr based PFM in the oral cavity has been disputed. The focus of dispution refers to the elemental ion release of toxic metals from casting alloys, which is suspected to accumulate to high level and thus lead to some adverse biological effects such as cytotoxicity, genotoxicity and allergy.In order to answer these questions, several epidemiological studies have been conducted. In the historical cohort study,795patients in a dental hospital who had single or multiple Ni-Cr alloy restoration recently and198controls were recruited. Detailed information including time of alloy therapies and when and where each therapy was conducted and how many teeth were replaced by alloy. A clinical examination was conducted to determine if the metal crown was fused to the porcelain and to what extent the surface area of metal crown covered with porcelain Urinary concentrations of Ni and Cr from each subject were measure by graphite furnace atomic absorption spectrometry. The correlation of Ni-Cr based alloy dental restoration, the enhanced excretions of nickel (Ni) and Chromium (Cr) in urine, the renal dysfunction (as measured by serum biochemical examination and urine biochemical examination) and immunological function parameters (as measured by TNF-a, IL-1β, IL-6) was observed. Main results can be summarized as follows:1. The mean urinary level of Ni of all the study population is0.57μg/L (61.08μg/mol creatininea). Urinary level of Ni (62.84μg/mol creatinine) in the patient group was a little higher than that in the control group (54.48μg/mol creatinine), but has no statistical difference. The mean urinary level of Cr of all the study population is0.51μg/L (53.82μg/mol creatinine). Urinary level of Cr in patient group56.65μg/mol creatinine), was significantly higher (p=0.003) than urinary level of Cr in the control group (43.83 creatinine).2. Dental restoration of Ni-Cr alloy can cause temporary increase of the uinary level of Ni. The urinary level of Ni in the patient group of<1month of the restoration duration (87.75μg/mol creatinine) is significantly higher (1.61, p <0.001) than the urinary level of Ni in the control group (54.48μg/mol creatinine). However, the urinary level of Ni decreases after1month. There is no statistical difference between the control group and patient group.3. Dental restoration of Ni-Cr alloy can also cause temporary increase of the uinary level of Cr. All of the urinary level of Ni in the patient group of<1month of the restoration duration(63.80μg/mol creatinine),1-month of restoration duration (62.93μg/mol creatinine), and3-month restoration duration (57.62μg/mol creatinine) are significantly higher than the urinary level of Cr in the control group (43.83μg/mol creatinine). They are1.46(p <0.001)、1.44(P=0.003)'1.31(P=0.023) respectiely. There is no statistical difference between the control group and patient group in6-months and12months above.4. Both higher number of teeth replaced by dental alloys and larger exposure surface of metal crown (not covered with the porcelain) can cause higher Ni excretions. In the patient group of<1month of the restoration duration, the urinary level of Ni in those had3or more Ni-Cr alloys dental restoreation (103.20μg/mol creatinine) is significantly higher than those had less than3Ni-Cr alloys dental restoreation (70.73μg/mol creatinine)(p=0.019) The urinary level of Ni in those have medium and above exposure surface of metal crown (118.37μg/mol creatinine) significantly higher than those who have non or less exposure surface of metal crown (73.02μg/mol creatinine)(p=0.012). In the patient group of<1month and1-month of the restoration duration respectively, there is no significant difference of the urinary level of Cr for the number of teeth replaced by dental alloys. However, the urinary level of Cr in those have medium and above exposure surface of metal crown (19.10μg/mol creatinine) significantly higher than those who have non or less exposure surface of metal crown (55.72μg/mol creatinine)(p=0.003)5. No associations among the duration, number, exposure surface of metal crown dental alloy and the renal dysfunction are identified. No evidence shows the increased excretion of Ni and Cr can cause the damage of kidney by the analysis of the urinary level of Ni, Cr and the renal function.6. Neither the duration, number, exposure surface of metal crown dental alloy, nor urinary level of Ni, Cr, has been identified associations with the increase of inflammatory mediators such as TNF-α、IL-1and IL-6.In the quasi-trial, the urinary level of Ni and Cr were measured in33cases before and after the Ni-Cr alloy dental restoration. The renal function and immunological function parameters before and after the Ni-Cr alloy dental restoration was compared. Main result can be summarized as follows:1. In male, there is no statistical difference of urinary level of Ni and Cr before and after Ni-Cr alloy dental restoration. In female, the urinary level of Ni after Ni-Cr alloy dental restoration (73.69μg/mol creatinine) is1.64of the urinary level of Ni before dental restoration(44.77(μg/mol creatinine), with borderline significance (p=0.068). Also in female, the urinary level of Cr after Ni-Cr alloy dental restoration (124.39μg/mol creatinine) is2.08times of the urinary level of Ni before dental restoration(59.85μg/mol creatinine), with statistical significance (p=0.023). The increase of urinary level of Ni and Cr before and after Ni-Cr alloy dental restoration.in female might be attributed to the high propotion of cases who have large exposure surface of metal crown (52%in femle vs2%in male).2. No associations between dental alloy restoration and the renal dysfunction are identified.3. No associations between dental alloy restoration and the increase of inflammatory mediators such as TNF-α IL-1and IL-6.Conclusion:1. The Ni-Cr alloy dental restoration can cause the temperory increase of the urinary level of Ni and Cr, but the increase is limited in one month for urinary level of Ni and6months for the urinary level of Cr.2. The main causes for the the temperory increase of the urinary level of Ni and Cr are higher number of teeth replaced by dental alloys and larger exposure surface of metal crown.3. The urinary level of Ni and Cr in the study is much lower than the toxicosis reference value. In the study, the increased urinary level of Ni and Cr is less than double while the the mean toxicosis reference value is about20times.4. Whether or not taking Ni-Cr alloy dental restoration, neither the number of teeth replaced by dental alloys, nor larger exposure surface of metal crown has effect on the renal dysfunction and systemic anaphylaxis reaction.5. There is no association between the increased urinary level of Ni and Cr and allergic reaction of human body in this study.6. In conclusion, from the prospective of renal dysfunction and systemic anaphylaxis reaction, Ni-Cr alloy dental restoration is safe to human.Recomedation:1. Patients should make sure if they are allegic to Ni before they have Ni-Cr alloy dental restoration.2. It is not necessary to prohibit the use of Ni-Cr alloy dental restoration, however, caution should be given to avoid the exposure of of metal crown. |
PDF Full Text Request