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SUMMARY OBJECTIVE: The aim of this study was to explore the influencing factors of preterm twin pregnancy. METHODS: In total, 602 twin-pregnant women delivered from February 2016 to February 2020 were analyzed retrospectively. According to whether the pregnant women were preterm or not, they were divided into preterm group (n=363) and term group (n=239). Baseline information, such as maternal age, address, and education level of the pregnant women, were collected. The clinical information of pregnant women, such as chorionic, preeclampsia, gestational diabetes, premature rupture of membranes, abnormal fetal position, and fetal weight, were analyzed. Logistic regression analysis was used to analyze the risk factors. p-value <0.05 was considered statistically significant. RESULTS: In the preterm group, monochorionic diamniotic comorbidities were significantly higher compared with the control group (p<0.05). Higher risks of preterm group have lower education (p<0.05). Multiple logistic regression analysis demonstrated that education, preeclampsia, and premature rupture of membranes were risk factors for preterm twin pregnancy. CONCLUSIONS: Preterm birth in twin pregnancy is associated with many risk factors, such as education, preeclampsia, and premature rupture of membranes. Pregnancy supervision and prenatal guidance for twin pregnancy should be strengthened. Furthermore, early detection and diagnosis of comorbidities can improve maternal and neonatal outcomes.
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Objective@#o study the effect of cleaning treatment with hydrofluoric acid (HF) on the surface and bonding strength of IPS e.max and Vita Mark II ceramic inlays. @*Methods@#Fifty pieces of IPS e.max and Vita Mark II ceramic inlay specimens were made separately using CAD/CAM. After uniformly bonding surfaces using 9% HF etching, they were randomly divided into an untreated control group (group A) and the following experimental groups: neutralizing powder (B group), 37% phosphoric acid (group C), ultrasonic cleaning (group D) and neutralizing powder + 37% phosphoric acid + ultrasonic cleaning (group E). Each set of 8 specimens was bonded to Variolink N resin adhesive under standard conditions. The shear adhesive strength was measured after exposure to a constant-temperature water bath at 37 ℃ for 24 h. The location of the fracture and the type of adhesion failure were recorded. The shear adhesion and the average strength of the connection were analyzed. The remaining 2 specimens were used for scanning electron microscopy (SEM) to observe the surface morphology, including the crystal structure, pore pattern, and residue.@*Results @# The results were similar for the IPS e.max and Vita Mark II inlays. The maximum bond strength was observed in the IPS e.max ceramic inlays in group E, with an average bond strength 11.96 MPa higher than that in group A. Among the Vita Mark II porcelain inlays, the maximum bond strength was observed in group E. The average bond strength was 9.74 MPa higher than that in group A. The results of the statistical analysis were similar for the IPS e.max and Vita Mark II porcelain inlays, with significant differences in the bond strengths between groups C, D, and E and the control group (P < 0.05). There was no significant difference in the adhesive strength between groups B and A. At the same time, there was no significant difference in the bond strength between the treatment groups B, C, D, and E (P > 0.05). SEM revealed that the pores on the surface of ceramics subjected to the acid etching treatment were broadened and uniform, with less residue than observed in the control group. The effects of treatments D and E were the best. @*Conclusion@#The HF etching treatment can enhance the bonding strength of IPS e.max and Vita Mark Ⅱ ceramic inlays while leaving little residue, and the joint strength is highest when the joints are treated together.