Objective·To analyze the root canal diameter and taper of mandibular first molars using cone-beam CT(CBCT),investigate age-related changes in these parameters,and propose optimized clinical protocols for root canal preparation.Methods·From October 2022 to October 2023,CBCT images of 240 healthy mandibular first molars(120 three-canal type cases and 120 four-canal type cases)were collected from patients aged 20?59 years at the Stomatology Center,Haikou Affiliated Hospital of Central South University Xiangya School of Medicine.The three-canal type and the four-canal type samples were respectively divided into four age groups(20?29,30?39,40?49,and 50?59 years),with 30 cases in each group.Root canal length was measured,and buccolingual and mesiodistal diameters were recorded at four levels(coronal,middle,apical,and foramen).The tapers of the coronal 1/3,middle 1/3,and apical 1/3 segments were calculated in both buccolingual and mesiodistal directions.Differences among the age groups were compared.Results·The buccolingual diameters of all root canals exceeded the corresponding mesiodistal diameters.At several levels of most root canals,the diameters in the<50-year-old groups were significantly larger than those in the 50?59-year-old group(P<0.05).The buccolingual tapers exceeded the corresponding mesiodistal tapers in all root canals of mandibular first molars.The mean mesiodistal tapers in different age groups ranged from 0.07 to 0.34 in the coronal 1/3 segment,0.03 to 0.09 in the middle 1/3 segment,and 0.05 to 0.11 in the apical 1/3 segment.At several levels of most root canals,the tapers in the<50-year-old groups were significantly larger than those in the 50?59-year-old group(P<0.05).Conclusion·Mandibular first molars exhibit age-related narrowing of root canal diameter and reduced taper in individuals aged≥50 years.For initial apical file selection,#15 files are recommended for the distal canals in the three-canal type,while#10 files are advised for all other canals in the three-canal type and all canals in the four-canal type.For patients aged 50 years or older,the files for the distal canals in the three-canal type can be adjusted to#10,and the files for the mesiobuccal and distallingual canals in the four-canal type to#8.Regarding preparation taper,a 0.08-taper orifice opener is recommended for the coronal 1/3 segment.During mid-lower segment preparation,0.04-taper master apical files are suggested for the mesiobuccal and mesiolingual canals in the three-canal type and the mesiolingual and distallingual canals in the four-canal type,0.06-taper files for the distal canals in the three-canal type and the mesiobuccal canals in the four-canal type,and 0.08-taper files for the distobuccal canals in the four-canal type.Root canal obturation is recommended to be performed using vertical compaction with large-taper gutta-percha cones combined with bioceramic sealer.

Objective·To analyze the root canal diameter and taper of mandibular first molars using cone-beam CT(CBCT),investigate age-related changes in these parameters,and propose optimized clinical protocols for root canal preparation.Methods·From October 2022 to October 2023,CBCT images of 240 healthy mandibular first molars(120 three-canal type cases and 120 four-canal type cases)were collected from patients aged 20?59 years at the Stomatology Center,Haikou Affiliated Hospital of Central South University Xiangya School of Medicine.The three-canal type and the four-canal type samples were respectively divided into four age groups(20?29,30?39,40?49,and 50?59 years),with 30 cases in each group.Root canal length was measured,and buccolingual and mesiodistal diameters were recorded at four levels(coronal,middle,apical,and foramen).The tapers of the coronal 1/3,middle 1/3,and apical 1/3 segments were calculated in both buccolingual and mesiodistal directions.Differences among the age groups were compared.Results·The buccolingual diameters of all root canals exceeded the corresponding mesiodistal diameters.At several levels of most root canals,the diameters in the<50-year-old groups were significantly larger than those in the 50?59-year-old group(P<0.05).The buccolingual tapers exceeded the corresponding mesiodistal tapers in all root canals of mandibular first molars.The mean mesiodistal tapers in different age groups ranged from 0.07 to 0.34 in the coronal 1/3 segment,0.03 to 0.09 in the middle 1/3 segment,and 0.05 to 0.11 in the apical 1/3 segment.At several levels of most root canals,the tapers in the<50-year-old groups were significantly larger than those in the 50?59-year-old group(P<0.05).Conclusion·Mandibular first molars exhibit age-related narrowing of root canal diameter and reduced taper in individuals aged≥50 years.For initial apical file selection,#15 files are recommended for the distal canals in the three-canal type,while#10 files are advised for all other canals in the three-canal type and all canals in the four-canal type.For patients aged 50 years or older,the files for the distal canals in the three-canal type can be adjusted to#10,and the files for the mesiobuccal and distallingual canals in the four-canal type to#8.Regarding preparation taper,a 0.08-taper orifice opener is recommended for the coronal 1/3 segment.During mid-lower segment preparation,0.04-taper master apical files are suggested for the mesiobuccal and mesiolingual canals in the three-canal type and the mesiolingual and distallingual canals in the four-canal type,0.06-taper files for the distal canals in the three-canal type and the mesiobuccal canals in the four-canal type,and 0.08-taper files for the distobuccal canals in the four-canal type.Root canal obturation is recommended to be performed using vertical compaction with large-taper gutta-percha cones combined with bioceramic sealer.

Nitrogen is one of the most important nutrient elements for plants and a major limiting factor in plant growth and crop productivity. Glutamine synthase (GS) is a key enzyme involved in the nitrogen assimilation and recycling in plants. So far, members of the glutamine synthase gene family have been characterized in many plants such as Arabidopsis, rice, wheat, and maize. Reports show that GS are involved in the growth and development of plants, in particular its role in seed production. However, the outcome has generally been inconsistent, which are probably derived from the transcriptional and post-translational regulation of GS genes. In this review, we outlined studies on GS gene classification, QTL mapping, the relationship between GS genes and plant growth with nitrogen and the distribution characters, the biological functions of GS genes, as well as expression control at different regulation levels. In addition, we summarized the application prospects of glutamine synthetase genes in enhancing plant growth and yield by improving the nitrogen use efficiency. The prospects were presented on the improvement of nitrogen utility efficiency in crops and plant nitrogen status diagnosis on the basis of glutamine synthase gene regulation.
Arabidopsis ; Genes, Plant ; Glutamate-Ammonia Ligase ; genetics ; Nitrogen ; metabolism ; Oryza ; Plants ; enzymology ; genetics ; Triticum ; Zea mays

ObjectiveTo discuss the influence on diagn osing of femoral vein reflux by using the different ultrasound Doppler probing points. MethodsUsing pulse wave(PW) and color Doppler flow imaging, 134 femoral veins in 67 cases of lower limb varicosity were detected at 3 different probing points to check up the deep venous reflux after Valsava maneuver. The ultrasonographic data were compared with the results of venous DSA and operation to analyze the influence on diagnosis. ResultsThe reflux data obtained from the upper point of superficial femoral vein was most correlative with the results of DSA and operation. ConclusionsThe PW is a satisfactory technique in diagnosing the femoral reflux, and the upper point of superficial femoral vein is a most reasonable probing point.