Objective To investigate the causal relationship between gut microbiota and obstruc-tive sleep apnea syndrome(OSA)using a two-sample bidirectional Mendelian randomization(MR)approach.Methods Eligible single nucleotide polymorphisms(SNPs)were selected from genome-wide association study(GWAS)databases as instrumental variables.A bidirectional MR analysis was conducted to evaluate the causal effects between gut microbiota and OSA.Various statistical methods,including the inverse variance weighted(IVW)method,MR-Egger regression,the weighted model method,and the weighted median method,were employed for association assessment.The MR pleiot-ropy residual sum and outlier(MR-PRESSO)test,along with Cochran's Q test and the leave-one-out cross-validation method,were used to assess heterogeneity and pleiotropy.Results According to the IVW method analysis,an increased abundance of the genus Faecalibacterium(sp002397985)(OR=0.847,95％CI,0.719 to 0.997,P=0.046)was associated with a reduced risk of OSA.Conversely,increased abundances of the genera Bacteroides(OR=1.075,95％CI,1.016 to 1.138,P=0.012),Haemophilus(sp001679485)(OR=1.106,95％CI,1.016 to 1.203,P=0.021),Streptococcus(OR=1.168,95％CI,1.036 to 1.316,P=0.011),and Blautia(sp002159835)(OR=1.169,95％CI,1.035 to 1.319,P=0.012)were associated with an elevated risk of OSA.The reverse MR analysis revealed no significant association between the risk of OSA and the abundance of gut microbiota.The results of Cochran's Q test,MR-Egger test,and MR-PRESSO test indicated no het-erogeneity or horizontal pleiotropy(P＞0.05).Conclusion Causal relationships exist between the five genera(Faecalibacterium,Bacteroides,Haemophilus,Streptococcus,and Blautia)and the risk of OSA.

BACKGROUND:Domestic scholars use the potentiodynamic polarization technique to determine the corrosion potential of the dental aloys, which is used to evaluate the corrosion performance of the lownoble metal. They have discovered that the main reason affecting corrosion resistance is the content of noble metal. OBJECTIVE:To evaluate the corrosion resistance of Ti, Au aloy, Co-Cr aloy, Ti aloy, and Ni-Cr aloy. METHODS: Five aloys were immersed in synthetic saliva solution. The corrosion potential and corrosion current density of the aloys were determined with potentiadynamic polarization technique. RESULTS AND CONCLUSION:The galvanic series of five kinds of aloys were ranged as folows: Au aloy > pure Ti > Ti aloy > Co-Cr aloy > Ni-Cr aloy. Au aloy and pure Ti had more positive potential that were not easy to produce corrosion; Ti aloy and Co-Cr aloy could form stable oxidation film with a strong ability of anti-pitting and crevice corrosion; Ni-Cr aloy potential was more negative and easy to be dissolved. The corrosion current density of five kinds of aloys was ranged as folows: Au aloy < pure Ti < Ti aloy < Co-Cr aloy < Ni-Cr aloy. Au aloy and pure Ti had lowest current density which was 10-8, indicating that the corrosion rate of Au aloy and pure Ti was lower; in contrast, Ni-Cr aloy possessed the maximum corrosion rate. These findings indicate that Au aloy and pure Ti exhibit a very high corrosion resistance. The corrosion rate of Ni-Cr aloy is the highest; therefore, Ni-Cr aloy is the least acceptable material for implant suprastucture.