Mechanical properties of nickel-titanium archwire used in the final treatment phase of Tip-Edge Plus technique: an in vitro study / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>As the only active component in final treatment phase of Tip-Edge Plus technique, the activation of nickel-titanium orthodontic archwires is one of the factors that affect the torque expression. It is necessary to evaluate the mechanical properties of the nickel-titanium wire used in the final treatment phase in simulated oral environments to forecast the treatment outcomes.</p><p><b>METHODS</b>The mechanical properties of 171 thermal nickel-titanium wires of 0.35 mm (0.014-in) in diameters with different deflection of 40 mm in length were investigated with three-point bending test. The samples were divided into 2 groups: as-received and bended groups. In the bended group, samples were divided into 7 subgroups according to the amounts of deflection and named by the canine angulations (-25°, -19°, -13°, -7°, -1°, +5°, +11°). The deflection of wires was made by inserting the wires into the deep tunnel of Tip-Edge Plus brackets positioned in plaster casts with different canine angulations to mimic the use of nickel-titanium wires in the final treatment phase. Immersed the bended group in artificial saliva (pH 6.8) and preserved at 37.0°C. Eight durations of incubation were tested: 1 to 8 weeks. Three analogous samples of each group and subgroups were tested per week. Stiffness (YS:E) and the load-deflection characteristics of unloading plateau section were obtained.</p><p><b>RESULTS</b>Significant changes in specific mechanical properties were observed in long-term immersed and large deflected wires compared with as-received groups. Both immersion time and deflection affected the mechanical properties of wires in the simulated oral environment, and the two factors had synergistic effect. In groups -25°, -19° and -13°, stiffness (YS:E) increased then decreased and average plateau force and ratio of variance decreased then increased correspondingly at specific time.</p><p><b>CONCLUSIONS</b>In the final treatment phase of Tip-Edge Plus technique, the mechanical properties of nickel-titanium wire are associated with the using time and amounts of deflection and it may affect treatment outcomes. As the main reason for wire deflection, canine crown angulation plays an important role in the wire performance. It may be wise to focus on the canine crown angulations and using time in clinic with Tip-Edge Plus technique and make proper adjustment to help to make sure the treatment outcomes.</p>

Comparative studies of casein phosphopeptide-amorphous calcium phosphate and fluoride products in inhibiting enamel demineralization / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and several fluoride products in inhibiting enamel demineralization.</p><p><b>METHODS</b>Seventy healthy premolars extracted before orthodontic treatment were divided into seven groups (A: CPP-ACP; B: CPP-ACP + fluoride mouth rinses; C: fluoride mouth rinses; D: fluoride glass ionomer protection; E: fluoride resin binder; F: fluoride varnish; G: control group). There were ten samples in each group. The teeth were dipped into an artificial caries solution ten minutes at a time, then applied separately with CPP-ACP, CPP-ACP + fluoride mouth rinses, fluoride mouth rinses, fluoride glass ionomer protection, fluoride resin binder and fluoride varnish on labial enamel. The samples were dipped into an artificial saliva solution (37°C). Then all samples were examined with atomic force microscope (AFM) at the end of first, second and third monthes.</p><p><b>RESULTS</b>At the end of the first month, surface roughness in group D [(114 ± 1) nm] was significantly lower than that in group G[(172 ± 9) nm]. At the end of the second month and the third month, significant difference was found in surface roughness between group G and the rest of groups (P < 0.05); between group B and the rest of groups; and between group C and groups (D, E and F).</p><p><b>CONCLUSIONS</b>CPP-ACP and fluoride could both inhibit enamel demineralization in vitro. Solid fluoride (groups D, E and F) had better results than liquid fluoride (group C).</p>

Expression of CD133+ endothelial progenitor cell in rat periodontal tissue during tooth movement / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the expression patterns of CD133+ endothelial progenitor cell (EPC) on Wister rats during experimental tooth movement.</p><p><b>METHODS</b>40 Wistar rats' teeth movement models were established and divided into experiment group and control group. After loading 1, 3, 5, 7, 14 days killed them respectively. The histological sections were stained with hematoxylin-eosin and rabbit anti-rat CD133 polyclonal antibody to express CD133 immunoreactivity.</p><p><b>RESULTS</b>Expression of CD133 in the new vessels did not appear in control group. In the early experiment, the expression of CD133 was discovered in the new vascular endothelial cells of periodontium in experiment group. Expression of CD133 got the maximum after loading 1 day in experiment group, then decreased gradually, but it was not significantly higher than control group (P > 0.05).</p><p><b>CONCLUSION</b>CD133+ EPC participated vascularized reaction in periodontal tissue of rat during the experimental tooth movement, direct participation was few and indirect effects possibly existed.</p>

Study of 5-bromodeoxyuridine labeling of endothelial progenitor cells from the circulating blood from tooth movement rat / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the optimal dosage and timing for 5-bromodeoxyuridine (BrdU) labeling of endothelial progenitor cells (EPCs) from rat circulating blood.</p><p><b>METHODS</b>The animal model for rat tooth movement was established. EPCs were obtained by density gradient centrifugation. The expressions of specific antigens on cell surface were analysed by immunocytochemistry and fluorescenceochemistry. EPCs were incubated with BrdU at different concentrations (5, 10, 15 micromol/L) for different incubating time (12, 24, 48, 72, 96 h) to identify the optimal BrdU concentration and incubating time for cell labeling. Immunohistochemistry was performed to calculate the labeling index (LI).</p><p><b>RESULTS</b>The culture cell positively expressed CD34, CD133 and could be shown to endocytose DiI-ac-LDL, FITC-UEA-1. Incubation of the EPCs with BrdU at 10 micromol/L and for an optimal length of 72 h appeared to achieve the highest LI (66.8+/-2.9)%, which was significantly higher than group of 5 micromol/L (P<0.05), while there was no significant difference between the group of 15 micromol/L and 10 micromol/L (P>0.05).</p><p><b>CONCLUSION</b>EPCs can be isolated from tooth movement rat circulating blood and cultured. Incubation of the EPCs with BrdU at 10 micromol/L and for an optimal length of 72 h appeared to achieve the optimal LI. This provides a foundation for us to investigate the mechanism of chemiotaxis and differentiation for EPCs.</p>

A three-dimensional finite element study on composite archwire applied in extraction cases / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To explore mechanical properties of the composite archwire (CoAW) applied in extraction cases.</p><p><b>METHODS</b>The mandibular three dimensional model was established by spiral computed tomography scanning and SOLIDWORKS 2001 PLUS software. The archwire model was established by means of ANSYS software. The mechanical analysis and calculation of CoAW were carried out.</p><p><b>RESULTS</b>With the diameter of NiTi part of CoAW gradually augmented (the diameter of stainless steel part kept unchanged), the stress on teeth gradually increased. As the diameter of stainless steel part of CoAW gradually augmented (the diameter of NiTi part kept unchanged), the stress on teeth also gradually increased. The CoAW (0.30 mm NiTi round wire combined with 0.36 mm stainless steel round wire) produced the least force on teeth. There was little contradistinction between six kinds of CoAW and stainless steel wire on the stress of posterior teeth.</p><p><b>CONCLUSIONS</b>The stress on teeth closely correlated with the diameter of the composite archwire.</p>

Dental arch characteristics of the facial asymmetry / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To study the characteristics of dental arches in the patients with facial asymmetry.</p><p><b>METHODS</b>20 facial asymmetrical patients were chosen as the study subjects. They were 8 boys and 12 girls, aged from 12-year to 16-year old. 20 normal occlusion persons without signs of facial asymmetry were chosen as control. Dental casts were measured by 3-dimension measuring machine. Dental arch asymmetry, coordination between upper and lower dental arch, and dental inclination were measured. SAS 6.03 was used in statistical analysis.</p><p><b>RESULTS</b>The distance from cuspid and the first bicuspid to the median palatal raphe in the side of crossbite was larger than that of contralateral side in maxilla. The distance from cuspid, bicuspids and the first molar to the midline in the side of crossbite was smaller than that of contralateral side in mandible (P < 0.05). The dental arch width of cuspid and first premolar in maxilla was smaller than that of mandible (P < 0.05) . Significant buccal inclination of the maxillary posterior teeth coupled with lingual inclination of the mandibular posterior teeth was found on the crossbite side. In contrast, significant lingual inclination of the maxillary posterior teeth coupled with buccal inclination of the mandibular posterior teeth was found on the contralateral side (P < 0.05).</p><p><b>CONCLUSION</b>The width of upper anterior dental arch was smaller, and the inclination of upper and lower posterior teeth between crossbite side and counterside was different in facial asymmetry patients.</p>

Epidemiologic characteristics of influenza in China, from 2001 to 2003 / 中华流行病学杂志

<p><b>OBJECTIVE</b>To understand the epidemiologic characters of influenza in China from 2001 to 2003.</p><p><b>METHODS</b>Data of outpatient visits for influenza-like illness (ILI) each week and outbreaks of influenza were collected through National Influenza Surveillance Network, which includes 11 northern and 12 southern provinces of China. Samples were collected in the outpatients of ILI from 2001 to 2003 and influenza viruses were isolated and identified.</p><p><b>RESULTS</b>Epidemiological and laboratory surveillance data showed that the annual seasonality of influenza epidemic was clear. The peak of epidemic of influenza in northern areas was in winter season, during December to January. However, there were three peaks distributed to Spring (Apr.-May.), Summer (Jun.-Aug.) and Winter (Dec.-Jan.) seasons in the southern areas. In the peak months, the number of ILI visits per day and per surveillance hospital had increased two-fold in northern and by 37% in southern China. The baseline of percentages for ILI visits, which calculated with 75th percentiles (P75), was 13.68% in the north and 13.08% in southern China. The age distribution of ILI was related to seasonal types of influenza. When the predominated strain of the season was influenza B virus, the ratio of the ILI visits younger than 15 year-old, increased obviously. When the predominated stains became influenza A virus, the ratio of patient visits for ILI aged over 25 year-old increased. Of 63 outbreaks of influenza, 92% of them occurred at primary and middle schools and usually occurred in May (32%). The type of strains usually changed around June.</p><p><b>CONCLUSION</b>The quality of national influenza surveillance system is reliable since it was matched between percentages of ILI visits and rates of influenza virus isolation. The different epidemiologic characteristics in north and south of China was noticed. Peak in spring was shown in southern area and which called for more analysis. The change of the types of strains in the outbreaks during April to June in the southern China could provide data for better understanding on the trend of epidemics in the next season.</p>