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Objective To investigate the level and relevant factors of pyrethroid pesticide exposure among pregnant women during the first trimester in rural areas of Yunnan province,and to provide basic data for further study and provide a basis for the formulation of intervention measures to reduce exposure.Methods According to the birth cohort of rural Yunnan built in 2014, pregnant women in the first trimester were recruited in two townships of an agricultural county who were confirmed pregnant and continued pregnancy in antenatal clinics. The concentration of the metabolites of the pesticides in the urine of women was determined by super high performance liquid chromatography and the contact status of pyrethroid pesticides was analyzed using a questionnaire survey. Results A total of 419 women in the first trimester were surveyed and 94.51% of women detected at least one of the pyrethroid metabolites, among which the detection rates of 3－Phenoxybenzoic acid (3－PBA), cis－/trans－3－ (2, 2－Dichloroethenyl)－2, 2－dimethyl－cyclopropanecarboxylate (cis－/trans－DCCA) and 4－fluoro－3－phenoxybenzoic acid (4－F－3－PBA) were 79.47%, 62.05% and 24.58%,and the median concentrations were 3.53 ng/mL, 14.80 ng/m L and less than the minimum detection limit 0.4 ng/m L.Only 12 people (2.95%) reported that they had exposure to pesticides.Self－reported exposure rate was not consistent with the actual exposure rate.Multivariate linear regression analysis showed that the season was a factor affecting the level of three metabolites in women in the first trimester. Higher lever was found in women in spring (t=2.147,P=0.032), summer (t=2.144,P=0.035) and winter (t=2.453,P=0.015) compared to those in autumn.Conclusion Pyrethroid pesticides were widely exposed in the pregnant women in rural areas of Yunnan province. Some women have higher exposure level, which is related to the season.
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Objective To analyze the mechanical properties of V-bends with different materials, sizes of arch wires, angles, shapes, inter-bracket distances by using finite element method, so as to provide references for clinical practice of V-bends. Methods The finite element models of V-bends were established, including two kinds of materials (stainless steel, titanium-molybdenum alloy), two sizes（0.43 mm×0.64 mm, 0.48 mm×0.64 mm）, two V-bend positions, two angles(150°, 165°),and two inter-bracket distances（7,10 mm）, so as to compare and analyze their mechanical properties after simulative loading. Results The maximum force values produced by V-bends with stainless steel arch wire were greater than that of V-bends with β titanium steel arch wire. The force produced by V-bends with 0.43 mm×0.64 mm arch wire was smaller than that produced by V-bends with 0.48 mm×0.64 mm arch wire. The size of arch wire had a more obvious impact on V-bends with symmetrical arch wire. The force of V-bends with asymmetric arch wire was more evidently influenced by the change of inter-bracket distance. For V-bends with the same shape, the smaller the V-shaped angle, the greater the force on the bracket would be. Conclusions The V-bends with different materials, different sizes of arch wires, different shapes and inter-bracket distances will have different mechanical behaviors. In clinical application, the materials, sizes of arch wires, shapes and angles of V-bends should be adjusted properly according to the inter-bracket distances.
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<p><b>OBJECTIVE</b>To explore the treatment plan in patients with congenital lower incisor missing.</p><p><b>METHODS</b>Thirty-six patients with congenital lower incisor missing were included in the investigation. The missing location, missing quantity, malocclusion type and treatment method were analyzed. Bolton index of two groups were analyzed. The first group was congenital missing one lower incisor who treated by extracting two upper first premolars and one lower first premolar. The second group was congenital missing two lower incisors who treated by exacting two upper first premolars.</p><p><b>RESULTS</b>The therapeutic effect of 36 cases were better. Overall ratio in two groups were 91.70% +/- 1.85% and 92.83% +/- 2.74%, anterior ratio were 81.69% +/- 2.12% and 85.46% +/- 2.39%, anterior tooth-size discrepancy were (2.16 +/- 0.64) mm and (4.27 +/- 1.14) mm. There were no significance difference on overall ratio in two groups (P > 0.05). There were significance difference in anterior ratio and anterior tooth-size discrepancy (P < 0.01).</p><p><b>CONCLUSION</b>For patients with congenital missing one lower incisor who need extraction in upper and lower jaws, it is less affection on Bolton index that extracting one premolar at non-missing side than extracting one center incisor in mandible.</p>
Subject(s)
Humans , Bicuspid , Incisor , Malocclusion , MandibleABSTRACT
<p><b>OBJECTIVE</b>To investigate the therapeutic reason of orthodontic patients in Luzhou.</p><p><b>METHODS</b>A questionnaire investigation was made for the following randomly chosen people: 452 teenage patients from orthodontic department of stomatology hospital affiliated to Luzhou Medical College were brought into treatment group. 600 students from Luzhou No. 2 Middle School were brought into non-treatment group. The questionnaire investigation was conducted to two groups. The results were statistically analysed with SPSS 10.0.</p><p><b>RESULTS</b>(1) The main aim for orthodontic treatment was to align the teeth. (2) 37.39% of the patients accepted orthodontic treatment for parent's demand. (3) 76.1% of the patients expected to align the dentition. (4) Most people in treatment group could accept the time and expenses in the orthodontic treatment, but most people of non-treatment group could not accept the expenses in the orthodontic treatment. (5) Most people thought appearance was important.</p><p><b>CONCLUSION</b>Aesthetic is the main reason for orthodontic patients.</p>
Subject(s)
Adolescent , Female , Humans , Male , Dentition , Malocclusion , Orthodontics, CorrectiveABSTRACT
<p><b>OBJECTIVE</b>To study the root resorption caused by edgewise appliance combined with flat bite plate treatment.</p><p><b>METHODS</b>65 patients with edgewise technique and flat bite plate treatment were chosen. All patients were taken panoramic radiograph before flat bite plate treatment, immediately after flat bite plate treatment and 6 months after flat bite plate treatment. Root resorption grade of mandibular permanent incisors were analyzed.</p><p><b>RESULTS</b>There were statistical difference in the root resorption grade of three groups (P < 0.05), but there was no statistical difference between male and female (P > 0.05).</p><p><b>CONCLUSION</b>Flat bite plate can cause root resorption of mandibular permanent incisors, but the root resorption is slight.</p>