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Objective@#To analyze factors affecting stability after fixed orthodontic treatment.@*Methods@#Five hundred and forty-four patients who had finished fixed orthodontic treatment more than two years in First Department of Orthodontics, China Medical University from January, 2000 to December, 2017 were investigated and the rate of regular revisit was counted. The data of 288 patients were successfully collected by calling or sending text messages and the rate of standard use of retainers as prescribed (patients wore retainers for 24 months or longer) was counted. According to the variation of peer assessment rating (PAR) index at the start of retention and the time the data collected, the patients were divided into relapse group (variation of PAR index >5) and non-relapse group (variation of PAR index ≤5). Difference significance analysis and multiple-factor logistic regression analysis were used. Sixty patients wearing retainers well were collected and the curative effects of Hawley retainer and vacuum formed retainer (VFR) were compared, which included overbite, overjet, maxillary irregularity index, mandibular irregularity index, width betwenn canine and width between first molar.@*Results@#The rate of regular revisit was 41.0% (223/544). Two hundred and one of 288 patients (69.8%) who were visited successfully had regular revisit, and 60.4%(174/288) of the patients wore retainers well; 30.2% (87/288) of the patients who were visited successfully didn't have regular revisit, and 10.4% (30/288) of the patients wore retainers well. Difference significance analysis showed that there was highly significant difference between relapse group and non-relapse group in the type of retainer and duration of retention (P<0.01). One hundred and forty of 224 patients (62.5%) in non-relapse group and 37.5% (24/64) of the patients in relapse group used VFR, and the duration of retention in non-relapse group was significantly longer than that in relapse group (P<0.01). Multiple-factor Logistic regression analysis showed that wearing Hawley retainers (OR=3.067, P<0.05) was the risk factor influencing relapse. The duration of retention (OR=0.832, P<0.01) was the protective factor influencing relapse. Independent-sample t test indicated that the variations of maxillary [(0.82±0.36) mm] and mandibular [(1.05±0.22) mm] irregularity index in Hawley retainer group were larger than maxillary [(0.64±0.29) mm] and mandibular [(0.72±0.35) mm)] irregularity index in VFR group, respectively. The differences between the two groups were significant (P<0.05).@*Conclusions@#Duration of retention was implicated in stability after orthodontic treatment. VFR had better effect in the aspects of irregularity index than Hawley retainer.
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Objective@#To analyze the type of malocclusion which was more likely to cause undesirable orthodontic results and the reasons for orthodontic re-treatment.@*Methods@#In this study, 202 patients who received orthodontic retreatment in School of Stomatology, China Medical University from 2004 to 2016 were collected. Forty-seven patients were teenagers under 18 years old, and 155 patients were adults over 18 years old. The chief complaint of all patients was analyzed. Seven orthodontic specialists were invited to analyze the reasons caused the orthodontic re-treatment according to the treatment records, plaster models, photographs, panoramic radiographs and lateral cephalograms. They were offered an evaluation form to fill in by their judgement. The reasons for orthodontic re-treatment and the problems related to previous orthodontic treatment were analyzed.@*Results@#In 202 patients, the chief complaints were protrusion of the teeth [30.2% (61/202)], protrusion of the mandible [20.8% (42/202)], and irregularity of the teeth [17.8% (36/202)]. The proportion of patients chosen undesirable treatment design was 68.3% (138/202). The proportion of patient having unusual growth tendency was 24.3% (49/202). The proportion of patients with poor compliance during treatment and retention was 24.3% (49/202).@*Conclusions@#In this study, the protrusion of the teeth, the protrusion of the mandible and the dental crowding were the main chief complaints for orthodontic re-treatment. Undesirable treatment design and unfavorable growth tendency were the main reasons for orthodontic re-treatment. Poor compliance of patients during the period of treatment or retention was an important reason for the patient to seek orthodontic re-treatment.
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Objective: To test the mechanical properties o f N48 NdFeB magnet.Methods:Samples of N48 NdFeB magnet in the size of 2 mm?3 mm?4 mm were prepared, the residual flux density,coercive force and maximum energy product of the samples were measured, the magnetic density aroun d the magnets,the attractive and repulsive force between two magnets in 0~10 mm air gap were investegated.Results:The residual flux density of t he N48 NdFeB magnet was 1.373 T, coercive force 1 037 A/m and maximum energ y product 368 kJ/m 3.The magnetic density at magnet surface was 0.338 T,it decr eased to 0 at the point that leave magnet surface 20 mm away. The highest attrac tive force was 4.47 N between two magnets, the attractive force was 4.47~0.39 N in 0~5 mm air gap.The highest repulsive force was 2.82 N and the repulsive force was 2.82~0.39 N in 0~5 mm air gap.Conclusion:The magnetic and m echanical properties of the N48 NdFeB magnet can meet the standard of the orthod ontic force.
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Objective:To study the effects of receptor activator of nuclear factor-kB ligand-RANKL in osteoblasts (OBs) activiated by Porphyromonas endodontalis(Pe),and to investigate the bone resorptive pathogenesis induced by Pe.Methods:Primary rat calvarial osteoblasts were cultured, then were infected with Pe ATCC 35406 at the density of 107 and 109 CFU/ml respectively for 24 h.To determine the kinetic effect of Pe on OBs,107 CFU/ml of Pe was used to stimulate the cells for 0,6,12,18 and 24 h respectively, RT-PCR were used to examine the RANKL mRNA expression.Results:The grey level ratio of RANKL mRNA expression to ?-actin in untreated OBs was 0.32,that in the cells infected by 107 and 109 CFU/ml of Pe for 24 h was increased to 1.73 and 2.24 respectively.Infected by 107 CFU/ml of Pe for 6,12 and 18 h,the ratio was 0.93,2.01 and 1.97 respectively.Conclusion:Pe may stimulate RANKL expresson in osteoblasts.