Objective To analyze the spatial relationship between the roots of maxillary anterior premolars and the maxillary sinus,thus providing an anatomical basis for timing,planning,surgical approaches,and implant selection at this site.Methods Cone beam CT(CBCT)images were collected from 264 patients(aged 20-65 years)who visited the Ruihua Dental Clinic between January 2017 and March 2023.The minimum distance from the apex of the maxillary an-terior premolar roots to the lower wall of the maxillary sinus was measured on the coronal plane.The classification of the vertical relationship between the tooth root and the lower wall of the maxillary sinus was performed,and comparisons were made bilaterally,between genders,and among different age groups.Results The minimum distance(Q50)from the apex of the first maxillary premolar root to the lower wall of the maxillary sinus was 7.34 mm for the single-root type,7.80 mm for the buccal root of the double-root type,and 7.36 mm for the palatal root.For the second maxillary premo-lar,the median distance was 2.56 mm for the single root type,1.73 mm for the buccal root type,and 1.23 mm for the palatal root type.There was a significant difference in the shortest distance from the apex of the right second maxillary premolar single root to the lower wall of the maxillary sinus among the different age groups(P＜0.05),with the 20-29-year-old group having the smallest median distance(1.52 mm)and the≥40-year-old group having the largest(4.44 mm).There was no significant difference in the effect of sex or laterality on distance(P＞0.05).The most common vertical relationship between the apex of the maxillary anterior premolar roots and the lower wall of the maxillary sinus was non-contact.There was no significant difference in the vertical relationship classification between the single-root and dou-ble-root types(P＞0.05).Conclusion Most maxillary first premolar roots can provide sufficient bone height,which makes it easy to achieve immediate implantation.The maxillary second premolar root frequently involves insufficient bone,which is necessary to make full use of the bone wall of the extraction socket or the sinus floor cortical bone to achieve initial stability.The vertical relationship between the premolar root and maxillary sinus was influenced by age and dental position.Younger age groups often exhibit inadequate bone height,and the indication for immediate implan-tation should be carefully considered.The number of roots does not significantly affect the relationship between the sinus and root;however,double-rooted premolars offer more support for immediate implantation and socket healing due to the small root diameter and bony separation between the roots.

【Objective】 To analyze the demographic characteristics of whole blood donors who responded to blood donation initiatives launched by our blood center, so as to formulate an efficient recruitment strategy and provide scientific reference for solving seasonal, structural and acute blood supply tensions in this region. 【Methods】 Such characteristics as age, gender, household registration, occupation, blood type, education level, number of blood donations, blood donation location and recruitment method of 21 934 whole blood donors who responded to donation appointments issued by our blood center during January 2019 to June 2020 were analyzed, and the corresponding recruitment strategy in this region was established. 【Results】 39.79% of respondents were 36~45 years old, 69.61% were males, 70.49% were non-local permanent residents, and 62.96% were with education background from junior high school to high school. Workers accounted for 36.57%, 400 mL-donation accounted for 56.87%, the percentage of blood type O reached 42.18%, and blood donors with 2~5 donations accounted for 70.27%. The proportion of blood donors from Songshan Lake area(23.46%) ranked the highest, and that from Shuixiang area the lowest (3.26%). 76.42% of donation recruitment were issued via SMS. 【Conclusion】 Blood donors 36~45 years old, with 2~5 donations, donated 400 mL blood, non-local registered male, ordinary employees with the education level of junior high school, technical secondary school or high school should firstly be considered. The targeted areas are the Songshan Lake area, the main urban area coastal areas and southeastern Dongguan near Shenzhen.The corresponding recruitment strategies should be adjusted based on needs and emergency level.