Objective To explore the effect of different pontic designs in resisting stress interruption effect and roller coaster phenomenon through three-dimensional finite element analysis,providing clinical guidance for the application of clear aligners in extraction cases.Methods Four three-dimensional finite element models of different pontic designs in the extraction area of clear aligners were established,including the pontic-free connection design,the conventional hollow pontic design,the partially solid-filled pontic design and the fully solid-filled pontic design.All four aligner models were individually assembled with the dental arch model.A 0.2 mm distal movement of the canine was simulated to observe the initial displacement and periodontal ligament stress distribution of canine and second premolar in each group of models.Results The initial displacement tendency diagram revealed that in all experimental conditions,both the canine and second premolar exhibited tipping movement patterns.However,significant variations in initial displacement magnitudes were observed across different pontic designs.The fully solid-filled pontic-connected clear aligner model exhibited the greatest initial displacement values(both crown and root)and the maximum initial displacement magnitude.Notably,this kind of design displayed movement characteristics closer to bodily movement,indicating superior control efficacy in tooth positioning.Periodontal ligament stress analysis revealed that the fully solid-filled pontic-connected clear aligner model generated the highest maximum principal stress in the periodontal ligament.Conclusion This three-dimensional finite element study reveals that the application of solid-filled pontic in clear aligner therapy could improve biomechanical control at extraction sites by minimizing aligner distortion,reducing stress interruption effect and preventing the roller coaster phenomenon.

Objective To explore the effect of different pontic designs in resisting stress interruption effect and roller coaster phenomenon through three-dimensional finite element analysis,providing clinical guidance for the application of clear aligners in extraction cases.Methods Four three-dimensional finite element models of different pontic designs in the extraction area of clear aligners were established,including the pontic-free connection design,the conventional hollow pontic design,the partially solid-filled pontic design and the fully solid-filled pontic design.All four aligner models were individually assembled with the dental arch model.A 0.2 mm distal movement of the canine was simulated to observe the initial displacement and periodontal ligament stress distribution of canine and second premolar in each group of models.Results The initial displacement tendency diagram revealed that in all experimental conditions,both the canine and second premolar exhibited tipping movement patterns.However,significant variations in initial displacement magnitudes were observed across different pontic designs.The fully solid-filled pontic-connected clear aligner model exhibited the greatest initial displacement values(both crown and root)and the maximum initial displacement magnitude.Notably,this kind of design displayed movement characteristics closer to bodily movement,indicating superior control efficacy in tooth positioning.Periodontal ligament stress analysis revealed that the fully solid-filled pontic-connected clear aligner model generated the highest maximum principal stress in the periodontal ligament.Conclusion This three-dimensional finite element study reveals that the application of solid-filled pontic in clear aligner therapy could improve biomechanical control at extraction sites by minimizing aligner distortion,reducing stress interruption effect and preventing the roller coaster phenomenon.

Objective:To compare the efficacy of oral sulfate solution (OSS) and polyethylene glycol (PEG) electrolyte powder for colonoscopy bowel preparation.Methods:A total of 283 randomized patients from 9 centers in China taking OSS ( n=143) or PEG ( n=140) using two-day split bowel preparation regimen received colonoscopy and assessment. The primary index was the bowel preparation success rate [global Boston bowel preparation scale (BBPS)≥ 6 by independent assessment center]. Secondary indices included BBPS global and segmental scores, investigator satisfaction (5-point Likert scale) with the quality of bowel preparation, patient satisfaction assessed by questionnaires, and patient tolerance assessed by Sharma scale. Compliance and safety were compared between the two groups. Results:The bowel preparation success rates were 100.0% for OSS and 99.3% for PEG [adjusted difference 0.7% (95% CI: -5.3% - 6.7%), P<0.001 for non-inferiority]. The BBPS global score in OSS group was significantly higher than that in PEG group (8.1 VS 7.7, P<0.001). The segment BBPS scores were also higher in OSS group than those in PEG group for all 3 segments (right colon: 2.4 VS 2.3, P=0.002; transverse colon: 2.8 VS 2.7, P=0.018; left colon: 2.8 VS 2.7, P=0.007). Investigator Likert score in the OSS group was significantly higher than that in the PEG group (2.6 VS 2.3, P<0.001). There was no significant difference in compliance between OSS and PEG, except for the second dose (90.9% VS 82.6%, P=0.039). There was no significant difference in patient satisfaction, Sharma score or proportion of patients with tolerance-related symptoms between the two groups. Safety was comparable between the two groups, and all adverse events were mild to moderate. Conclusion:OSS has comparable efficacy with PEG, with higher BBPS scores in all segments, better investigator satisfaction, better compliance in split dose, and comparable patient tolerance and safety.

Objective:To evaluate the advantages of cortical perichondrium retention of costal cartilage in tip plasty.Methods:A total of 618 female cases were retrospectively analyzed from July 2017 to July 2018 in Zhengzhou Meilai Medical Beauty Hospital that underwent comprehensive line of rib cartilage rhinoplasty for beauty, aged 18-52 years with mean 27±6 years. According to different modification graft used in plasty, the cases were divided into reserve costal perichondrium cortex group (experimental group) and simple rib cartilage cortex group (control group). Statistical analyses were carried out 1 month and 12 months after operation. The tip displacement visualization was compared between the two groups and the advantages and disadvantages were evaluated in both.Results:After the surgery of the 618 patients, the rate of displacement in the experimental group was 3.6%, and that in the control group was 7.9% (χ 2=4.95, P<0.05). The rate of the implant exposure in the experimental group was 4.7%, and that in the control group was 9.1% (χ 2=4.38, P<0.05). The reserve costal perichondrium cortex used in the nasoplasty kept the prominent and stable nasal tip after the operation, and longterm follow-up showed there were no displacement and deformation occured in the patients. Conclusions:The application of costal cartilaginous cortex retaining costal perichondrium in tip plasty can obtain good nasal tip protrusion and stable rotation. It is an ideal nasal tip shaping material and worthy of clinical application.

Objective: To investigate the effect of low level laser on osteoclast and collagen fiber remodeling during the process of tooth retention after tooth movement in rats and to provide the experimental basis for clinical application. Methods : In total, 20 eight-week-old Wistar rats were selected to establish a mesial movement model of the maxillary first molar and then randomly divided into four groups after the appliance was removed. In total, 5 rats were included in each group, including baseline group (without force as blank control), control group (without any intervention after removing the force appliance), retention group (teeth were wrapped with orthodontic ligature wires that were screwed into hemp flower as fixed retention to maintain the space between the first molar and incisor after appliances were removed) and retention and low energy laser irradiation group (teeth were wrapped with the orthodontic ligature wires that were screwed into hemp flower as fixed retention and low energy laser irradiation was applied on days 0, 3, 6, 9 and 12 after appliance removal). Two weeks later, all the rats were sacrificed and the first molar tissue blocks of each group were collected. The distribution of osteoclasts and collagen fiber were studied by HE staining, TRAP staining and Masson staining to illustrate the process of alveolar bone and collagen fiber remodeling. Results : Two weeks after appliances were removed, collagen fibers were deposited on both sides of the root in the baseline group, but no osteoclasts were observed in the distal side of the root. In the control group, collagen fibers on the two sides of the root were not obvious and osteoclasts were active on the distal side. In the retention group, collagen fibers were obvious on the two sides of the root and the osteoclasts on the distal side were less active than the control group. Regarding the retention and low energy laser irradiation group, collagen fibers were significantly obvious and osteoclasts were not seen. The difference was statistically significant between the retention and low energy laser irradiation group and the other three groups (P＜0.05). Conclusion These results suggest that fixed retention with simultaneous low level laser can effectively promote the synthesis of collagen fibers and inhibit the activity of osteoclasts during the process of tooth retention after movement, thus reducing the possibility of molar recurrence.

Objective To investigate the value of D-dimer in predicting the progression of lower extremity deep venous thrombosis (DVT) during perioperative period of gastrointestinal surgery.Methods Color Doppler ultrasound was used to dynamically monitor the formation and changes of perioperative deep venous thrombosis (DVT) in 239 patients receiving abdominal surgery in our department from Nov 2014 to Aug 2016.Changes of plasma D-dimer were measured,and clinical data of malignant tumor,infection,age,BMI were collected.The relationship between D-dimer elevation and DVT progression was analyzed.Results Lower extremity DVT after surgery developed in 97 patients,and thrombosis progression occurred in 16.6％ (16/97).Univariate logistic regression analysis showed that continuous increase of postoperative D-dimer was closely related to the progression of thrombosiss.Multivariate Logistic regression analysis showed that the continuous rise of D-dimer was an independent risk factor for thrombosis.ROC curve analysis showed significantly increased risk of thrombosis progression,when plasma D-dimer polymerization increased ＞0.87 mg/L on the 3rd day.Conclusion The continuous increase of D-dimer ＞ 0.87 mg/L predicts DVT progression of lower extremity DVT.

Objective The purpose of this study was to establish and evaluate a mouse model of sepsis for studying the mechanism of sepsis and development of anti-inflammatory drugs.Methods The sepsis in mice was induced by cecal ligation and puncture ( CLP) .The survival rates, microbial load, liver and kidney damages, cytokines and pathological changes were detected to evaluate the mouse models.Results The death of mice was closely related with the ligated sites. The mice with 50%cecal ligation displayed about 40% of 12-day survival rate, however, all the mice with 75% cecum ligation died within 4 days (P<0.01).Compared with the sham surgery group, the mice with 50% cecal ligation had a high microbial load in the blood and abdominal cavity.Leukopenia was also emerged (P<0.001).CLP mice demonstra-ted elevated levels of serum ALT, AST and BUN (P<0.01).The levels of IL1α, IL6, IL10, MIP1α, MIP1β, and TNFαwere increased a lot.The liver and lung showed obvious pathological injury at 48 h post CLP.Conclusions The established mouse model of CLP shows typical characteristics of sepsis and is an ideal tool for further study of anti-inflam-matory drugs.

Objective To investigate the association between the gene polymorphisms of the DNA damage repair gene X-ray repair cross-complementing gene 1 (XRCC1) and susceptibility to chromosome damage in workers exposed to low-concentration benzene in the jewelcrafting industry.Methods A total of 286 workers exposed to benzene in jewelcrafting enterprises were enrolled as study subjects from January 2013 to December 2014.Gas chromatography was used to measure benzene concentration in workplace,cytokinesisblock micronucleus test was used to analyze the level of chromosome damage in peripheral blood,and the Sequenom technique was used to determine the single nucleotide polymorphisms of XRCC1.Results The timeweighted average concentration of benzene in workplace was ＜0.6 ～1.8 mg/m3,lower than the national occupational exposure limit (6 mg/m3).The distribution of allele frequencies met the Hardy-Weinberg equilibrium in genetics(P＞0.05).Increase in age(RR=1.38,95％CI 1.06～3.75) and increase in working years (RR=1.45,95％CI 1.18～2.58) were risk factors for the increase in micronucleus frequency.Compared with those with the wild-type homozygous genotype,the individuals with XRCC1 rs25487 CT genotype showed a significantly higher risk of increase in micronucleus frequency (RR=1.51,95％CI 1.28～3.87,P＜0.05),and the individuals with XRCC1 rs1799782 AA genotype also showed a significantly higher risk of increase in micronucleus frequency (RR =1.65,95％ CI 1.30～3.12,P＜0.05).There was no clear association between XRCC1 rs25489 polymorphisms and micronucleus frequency (P＞0.05).Conclusion Exposure to lowconcentration benzene may cause chromosome damage in workers exposed to benzene,and the XRCC1 polymorphisms rs 25487 and rs 1799782 may be associated with chromosome damage induced by benzene.

Objective To investigate the association between the gene polymorphisms of the DNA damage repair gene X-ray repair cross-complementing gene 1 (XRCC1) and susceptibility to chromosome damage in workers exposed to low-concentration benzene in the jewelcrafting industry.Methods A total of 286 workers exposed to benzene in jewelcrafting enterprises were enrolled as study subjects from January 2013 to December 2014.Gas chromatography was used to measure benzene concentration in workplace,cytokinesisblock micronucleus test was used to analyze the level of chromosome damage in peripheral blood,and the Sequenom technique was used to determine the single nucleotide polymorphisms of XRCC1.Results The timeweighted average concentration of benzene in workplace was ＜0.6 ～1.8 mg/m3,lower than the national occupational exposure limit (6 mg/m3).The distribution of allele frequencies met the Hardy-Weinberg equilibrium in genetics(P＞0.05).Increase in age(RR=1.38,95％CI 1.06～3.75) and increase in working years (RR=1.45,95％CI 1.18～2.58) were risk factors for the increase in micronucleus frequency.Compared with those with the wild-type homozygous genotype,the individuals with XRCC1 rs25487 CT genotype showed a significantly higher risk of increase in micronucleus frequency (RR=1.51,95％CI 1.28～3.87,P＜0.05),and the individuals with XRCC1 rs1799782 AA genotype also showed a significantly higher risk of increase in micronucleus frequency (RR =1.65,95％ CI 1.30～3.12,P＜0.05).There was no clear association between XRCC1 rs25489 polymorphisms and micronucleus frequency (P＞0.05).Conclusion Exposure to lowconcentration benzene may cause chromosome damage in workers exposed to benzene,and the XRCC1 polymorphisms rs 25487 and rs 1799782 may be associated with chromosome damage induced by benzene.

Objective To verify the infantile amnesia phenomenon and discuss the effect of rapamycin injection on infantile amnesia and hippocampal neurogenesis.Methods (1) In experiment one,17-day-old (P17) and 60-day-old (P60) male Sprague-Dawley rats (n=84) were trained in a passive-avoidance task (they were randomly sub-divided into the shocked group and non-shocked group);all rats were tested immediately,2 and 7 days after training for memory retention.(2) In experiment two,P17 rats (n=84) were randomly divided into three groups:vehicle group,20 mg/kg rapamycin group and 40 mg/kg rapamycin group (they were sub-divided into the shocked group and non-shocked group);P17 rats were immediately injected with either vehicle or rapamycin after passive-avoidance training,and memory retention was evaluated 2 and 7 days after training.(3) In experiment three,P1 7 rats (n=48) were randomly divided into four groups:normal group,vehicle group,20 mg/kg rapamycin group and 40 mg/kg rapamycin group;immunofluorescence staining of BrdU/DCX was detected to observe the hippocampal neurogenesis at post-natal day 19 (P19) and post-natal day 24 (P24) after vehicle or rapamycin injection at P17 rats.Results In experiment one,P17 and P60 shocked rats exhibited comparable levels of crossing latencies when being tested immediately (P＞0.05),when being tested after 2 days and 7 days,P17 rats forgot more rapidly than P60 rats (P＜0.05);there were no age-related differences in crossing latencies between the non-shocked groups (P＞0.05).In experiment two,three shocked groups exhibited comparable levels of crossing latencies when being tested 2 days after training (P＞0.05),however,administration of rapamycin could enhance the memory retention 7 days after training;significant differences were noted between the vehicle group and each of the rapamycin treated groups (P＜0.05);there were no dose-related differences in crossing latencies among the non-shocked groups (P＞0.05).In experiment three,less BrdU-positive and BrdU/DCX-positive cells were found in the DG of the hippocampus at 20 mg/kg and 40 mg/kg rapamycin groups as compared with those in the vehicle group at P19 and P24 rats (P＜0.05).Conclusion The infantile amnesia phenomenon is verified,and rapamycin may enhance the memory retention in infant rats by reducing the hippocampal neurogenesis.