Objective To compare the effects of different crown materials on the stress distribution of dental implants by finite ele-ment method.Methods A three-dimensional finite element model of implant-supported crown restoration of the right mandibular first molar was established.Four kinds of crown restoration materials were used,including polymer infiltrated ceramic network Vita Enamic,resin nanoceramic Lava Ultimate,zirconia ceramic Cercon,and polyether-ether-ketone breCAM.A displacement load of 0.01 mm or 200 N was applied to the occlusal surface of the right mandibular first molar,and the analysis of reaction force,the maximum variability of shape,the maximum principal stress,the maximum equivalent stress was performed.Results The results of stress analysis under 0.01 mm displacement load showed that the maximum equivalent stress of Cercon was 937.30 MPa,and that of breCAM was 67.09 MPa.The stress concentration of crowns and implants was obvious.The maximum equivalent stress of the surrounding alveolar bone of Cercon was the highest(26.61 MPa),and that of breCAM was the lowest(3.87 MPa),which was about 1/7 of that of maximum group.The stress concentration range of resin-matrix ceramics and polyether-ether-ketone was relatively small,and the distribution was more uniform.When 200 N was applied,the maximum principal stress and the maximum equivalent stress distribution of the four models were similar,and the maximum variability of shape of breCAM was larger at the loading site.Conclusion Under the same displace-ment load,the stress concentration of polyether-ether-ketone and resin-matrix ceramics crown was lower than that of zirconia.There was no significant difference in stress concentration in the implant and surrounding alveolar bone among polyetheretherketone,resin-ceramic composite,and zirconia crown restorations under the same load.Further research on long-term durability of PEEK and resin-matrix ce-ramicsis needed through practical and clinical trials.

Objective:To explore the epidemiological characteristics of Streptococcus pyogenes, namely β-hemolytic Group A Streptococcus (GAS) in children in Shenzhen. Methods:Multilocus sequence typing (MLST) data on the epidemic clonal population of GAS infection in children in Shenzhen Children′s Hospital from January 2016 to December 2018 were retrospectively analyzed.In the present study, 32 GAS strains belonging to 7 different emm types were from 32 children′s with impetigo, cellulitis, scarlet fever, sepsis, pneumonia, obstructive sleep apnea hypopnea syndrome, bronchitis, allergy with rhinitis, buttock abscess, allergic purpura or pharyngeal tonsillitis, which were isolated from 23 throat swabs, 5 sputum samples, 3 pus and 1 blood.Using polymerase chain reaction technology, 7 pairs of allelic housekeeping genes ( gki, gtr, murI, mutS, recP, xpt and yqiL) of 32 GAS isolates were analyzed, and the target gene products were subjected to sequencing.Then the obtained gene sequences of each allele were submitted to the MLST database to obtain the allele profile.Finally, the allele profiles were introduced in the MLST database again to confirm the sequence typing (ST). Results:The GAS clone groups of emm 1.00 and its subtypes, emm 4.00, emm 12.00 and its subtypes, emm 22.00, emm 28.00, emm 75.00, and emm 89.00 belonged to the sequence typing ST28, ST39, ST36, ST46, ST52, ST49, and ST921, respectively. Conclusions:From 2016 to 2018, the MLST clone populations of GAS isolates causing infections in children in Shenzhen are classified as ST28, ST39, ST36, ST46, ST52, ST49 and ST921.

All of neural stem cell within the central nervous system and derived from transplantation or embryonic stem cell have the ability of differentiating into various kinds of neural cells. Regeneration of neural cells plays a critical role on function recovery damaged central nervous system (CNS). Advances in repairing of injury in central nervous system with neural stem cell and embryonic stem cell in recent years are reviewed in this article.
Adult Stem Cells ; cytology ; Animals ; Central Nervous System Diseases ; physiopathology ; surgery ; Embryonic Stem Cells ; cytology ; Humans ; Nerve Regeneration ; physiology ; Neuronal Plasticity ; Neurons ; cytology ; Stem Cell Transplantation

OBJECTIVE To investigate the disinfectant-sulfanilamide resistance gene(qacE△1-sul1)and integrase gene(IntⅠ1)of Acinetobacter baumannii(ABA)isolated in pediatric clinic and analyze the relationship between these genes and multidrug resistance.METHODS Twenty eight strains of A.baumannii were collected and isolated from the sputum culture in the deep trachea of children with pneumonia during 2006.Identification of bacteria and susceptibility test by VITEK-32 automicroscan using GNI and GNS cards,were undertaken,qacE△1-sul1 gene and IntⅠ1 gene were analyzed by polymerase chain reaction(PCR).RESULTS Three of 28 strains of A.baumannii showed multidrug resistance,the positive rate was 10.71%.A.baumannii 4 strains were resistant to sulfamethoxazole/trimethoprim(SXT)with the positive rate 14.29%.Eleven strains that carrying qacE△1-sul1 genes and 4 strains carrying IntⅠ1 genes were detected,the positive rate was 39.29% and 14.29%,and qacE△1-sul1 and IntⅠ1 genes positive strains of A.baumannii were resistant to SXT,the other 7 qacE△1-sul1 positive strains were sensitive to SXT.CONCLUSIONS The main drug resistance in ABA resistant to SXT is to obtain qacE△1-sul1 gene.It should be paid attention to qacE△1-suⅠ1 positive but sensitive to SXT strains.It indicates that the strain carrying integron Ⅰ may show multidrug resistance.

Objective To investigate the cerebral CT appearances of toxic encephalopathy of tetramine and improve the recognition on this disease. Methods Four cases of toxic encephalopathy of tetramine were collected and their cerebral CT appearances were retrospectively analyzed. Results Cerebral CT appearances in acute phase (within 8 days): (1) cerebral edema in different degree. CT abnormalities consisted of cortical hypodensities and complete loss of gray-white matter differentiation. The CT value were in 11-13 HU, and to be watery density in serious case,(2)subarachnoid hemorrhage. It demonstrated the signs of poisoning hypoxic ischemic encephalopathy in chronic phase. Conclusion The cerebral CT appearances of toxic encephalopathy of tetramine had some character in acute phase and it can predict the serious degree of intoxication, but there was no characteristic findings in chronic phase.

The relationship between the resegmentation of somite and the segmental pattern of dorsal root ganglia was investigated by grafting the dissociated segmental plate cells (DC) of quail embryo to replace the right segmental plate to reconstruct an artificial disordered somite pattern. Seventeen hours after grafting, the DC somites were formed in the area of grafting. The DC somites were disordered in number, size and arrangement, some were near neural tube and some were further away from neural tube. After 29-32 h of grafting, the medial wall of DC somite was broken down and migrating mesenchymal cells moved toward notochord and formed sclerotome (the sclerotome in situ) between myotomes and neural tube as well as notochord. Each sclerotome was divided into two parts, the rostral and caudal sclerotome, as the somites on control side. The DC somites located further away from neural tube resegmented after 33-38 h, and the outside or lateral wall, not the medial wall, was distrupted and allosclerotome were formed outside to or among myotomes. So that the sclerotome could came from any side of the somitic epithelia as long as they disorganized and became mesenchymal cells in time. Corresponding to the sclerotome on control side, there were two kinds of dorsal root ganglia, the dorsal root ganglia in situ and alloganglia at the experimental side. The number, size and arrangment of sclerotomes formed in situ were independent on the somite from which they created, but corresponded to those of the sclerotome on the control side. So did the dorsal root ganglia in situ as the sclerotome in situ. The number of allosclerotoms was also independent on the somites from which they were derived, but matched the number of the sclerotome in situ, and the number of alloganglia was the same as the allosclerotomes.