Objective:Analysis of hepatitis B surface antigen negative donations, initial detection of reactivity followed by subsequent differential tests or repeat the infection status of non-discriminated reactive (NDR) unresponsive blood donors to explore whether different nucleic acid detection systems have differences in the detection of HBsAg -/NDR. Methods:The test result and reactivity rates of blood donor samples received from January 2020 to August 2022 were compared, and some samples were repeated for both nucleic acid testing systems, and the characteristics of the HBsAg -/HBV DNA + blood donors were analyzed. Results:Through the analysis of nucleic acid result from January 2020 to August 2022, repeated nucleic acid detection can improve the detection of HBsAg -/NDR blood donors, and the detection rate is offset in different cycle threshold valve ( Ct value) intervals or different sample absorbance to cut-off absorbance ratio ( S/ CO value) interval. Also grouping of Ct values or S/ CO values revealed that there was variability in detection rates between intervals in the two nucleic acid detection systems (PCR: X2=108.23, P<0.001, TMA: X2=40.95, P<0.001), mainly concentrated in Ct values less than 38.5 or S/ CO values between 10 and 15. And analysis of selected HBsAg -/HBV DNA + blood donor populations revealed that repeat nucleic acid testing was found for donors of different age ( X2=9.38, P=0.025), number of blood donations ( X2=22.52, P<0.001), occupation ( X2=24.92, P=0.002) and education level ( X2=10.37, P=0.016) significant differences, while there was no statistically significant difference for blood donors by gender ( X2=9.38, P>0.05), with far more males (67.50%) than females. Conclusions:For blood donors with a Ct value of less than 38.5, or an S/ CO value between 10 and 15, or a blood donor at the age of 41 to 50 years, another detection technology can be combined to improve the detection rate, reduce the potential risk of virus transmission of HBsAg -/NDR blood donors, and ensure the safety of clinical blood.

Objective: To further study the most suitable parameters for automatic full crown preparation using oral clinical micro robot. Its purpose is to improve the quality of automated tooth preparing for the system and to lay the foundation for clinical application. Methods: Twenty selected artificial resin teeth were used as sample teeth. The micro robot automatic tooth preparation system was used in dental clinic to control the picosecond laser beam to complete two dimensional cutting on the resin tooth sample according to the motion planning path. Using the laser scanning measuring microscope, each layer of cutting depth values was obtained and the average value was calculated. The monolayer cutting depth was determined. The three-dimensional (3D) data of the target resin teeth was obtained using internal scanner, and the CAD data of full-crown tooth preparation was designed by CAD self-develged software. According to the depth of the single layer, 11 complete resin teeth in phantom head were automatically prepared by the robot controlling the laser focused spot in accordance with the layer-cutting way. And the accuracy of resin tooth preparation was evaluated with the software. Using the same method, monolayer cutting depth parameter for cutting dental hard tissue was obtained. Then 15 extracted mandibular and maxillary first molars went through automatic full crown tooth preparation. And the 3D data of tooth preparations were obtained with intra oral scanner. The software was used to evaluate the accuracy of tooth preparation. Results: The results indicated that the single cutting depth of cutting resin teeth and in vitro teeth by picosecond laser were (60.0±2.6) and (45.0±3.6) μm, respectively. Using the tooth preparation robot, 11 artificial resin teeth and 15 complete natural teeth were automatically prepared, and the average time were (13.0±0.7), (17.0±1.8) min respectively. Through software evaluation, the average preparation depth of the occlusal surface of 11 resin teeth was approximately (2.089±0.026) mm, the error was about (0.089±0.026) mm; the average convergence angle was about 6.56°±0.30°, the error was about 0.56°±0.30°. Compared with the target preparation shape, the average shape error of the 11 resin tooth preparations was about 0.02-0.11 mm. And the average preparation depth of the occlusal surface of 15 natural teeth was approximately (2.097±0.022) mm, the error was about (0.097±0.022) mm; the average convergence angle was about 6.98°±0.35°, the error was about 0.98°±0.35°. Compared with the target preparation shape, the average shape error of the 15 natural tooth preparations was about 0.05-0.17 mm. Conclusions The experimental results indicate that the automatic tooth preparation for resin teeth and the teeth were completed according to the specific parameters of the single cutting depth by the micro robot controlling picosecond laser respectively, its preparation accuracy met the clinical needs. And the suitability of the parameter was confirmed.