BACKGROUND:The glass ionomer cement has good biological stability and can sustain the release of fluoride, which has been used as dental repair materials. But because of its low mechanical strength, the glass ionomer cement is confined to the front teeth and other parts with smal er force.
OBJECTIVE:To analyze the compressive strength, microleakage and other physical performances of Fuji IX glass ionomer cement after the addition of 8%modified nano-hydroxyapatite.
METHODS:(1) Universal testing machine was applied to detect the compressive strength of Fuji IX glass ionomer cement, Fuji IX glass ionomer cement added with 8%modified nano-hydroxyapatite, and super glass ionomer to fil the stainless steel cylinder. (2) Fuji IX glass ionomer cement, Fuji IX glass ionomer cement with 8%modified nano-hydroxyapatite and super glass ionomer were used to fil the tooth cavity;then, the microleakage was detected. (3) Fuji IX glass ionomer cement, Fuji IX glass ionomer cement added with 8%modified nano-hydroxyapatite, and super glass ionomer were used to fil stainless steel rectangular specimens. Then, universal material testing machine was applied to detect the bending strength value.
RESULTS AND CONCLUSION:The compressive strength, microleakage, and bending strength of specimens fil ed with Fuji IX glass ionomer cement the addition of 8%modified nano-hydroxyapatite were better than the other two groups, and Fuji IX glass ionomer cement was superior to the super glass ionomer in the compressive strength, microleakage and bending strength of fil ed specimens. It is shown that Fuji IX glass ionomer cement after addition of 8%improved nano-hydroxyapatite can improve the compressive strength and microleakage.

Objective:To evaluate the safety of leadless pacemaker implantation in super-elderly patients.Methods:Eleven patients with average age of 90 (86, 92) years who underwent leadless pacemaker implantation in the Department of Cardiology, Peking University People′s Hospital from March 2021 to May 2022 were included. The clinical data and implantation information were collected. The complications (cardiac tamponade, myocardial infarction, cerebral infarction, pulmonary embolism, pacemaker reinfection, femoral vein hematoma) and death of patients were documented at 24 h, 3 d, and 1, 3, 6 months after pacemaker implantation.Results:There were 9 males and 2 females with the body mass index of 21(19, 23)kg/m 2. The underlying diseases were hypertension, diabetes, coronary heart disease, chronic kidney disease, chronic obstructive pulmonary disease, previous cerebral infarction and moderate to severe tricuspid regurgitation in 9, 9, 9, 6, 4, 4, 4 patients, respectively. The left ventricular ejection fraction was 49% (45%, 52%), the hemoglobin concentration was 118 (114, 122)g/L, 4 patients were taking anticoagulant drugs, and 6 patients were taking antiplatelet drugs. Eight patients were newly implanted with a leadless pacemaker, 2 patients were implanted after removal the old ones, and 1 case was implanted at the same time as removal. The implantation time was 45(40, 47) minutes, the X-ray exposure time was 14 (13, 15) minutes, the release time was 1 (1, 2), the threshold value was 0.50(0.38, 0.75)V/0.24 ms, the impedance was 730 (700, 770) Ω, and the perceived R-wave amplitude 8.2(6.7, 12.8) mV. During the follow-up period of 8 (6, 10) months, no patient had pacemaker dysfunction; and the threshold, R wave sensing, and impedance were stable and maintained within the normal range. No cardiac tamponade, myocardial infarction, cerebral infarction, pulmonary embolism, pacemaker reinfection or death occurred perioperatively and during the follow-up period; 1 patient had hematoma after femoral vein puncture, which improved after compression treatment. Conclusion:This single-center and small-sample study shows that leadless pacemaker implantation is safe for super-elderly patients.