[Expression of MMP-2 in the periodontal tissues with the mini-screw for molar intrusion with cyclic intrusive force in dogs].

PURPOSE: To observe the expression of MMP-2 in the periodontal tissues of molars in Beagle dogs after different times of intrusion by mini-screw with cyclic intrusive force. METHODS: Three mature Beagle dogs were used for the experiment. On the buccal and palatal sites of the left maxillary second and third premolars, a minis-crew was placed at the inter-radicular septa separately, intruding the tooth with 150 g initial force, which would be reinforced every 4 weeks. The teeth of left side as the experimental group were divided into 3 subgroups, as being intruded 12, 24 and 36 weeks, and the right side as blank control. Then the dogs were sacrificed, and the second and the third premolars with the surrounding periodontal tissue were cut down, fixed, decalcified, wrapped and cut into slices. Immunohistochemical staining with MMP-2 was performed. The average optical density (OD) of MMP-2 was calculated with IPP software, which represented the expression of MMP-2. SPSS 17.0 software package was used for statistical analysis. RESULTS: Immunohistochemical staining revealed that the expression of MMP-2 in control group was low. After tooth intrusion, MMP-2 expression significantly increased in the periodontal tissues of molars, and reached the maximum in the group of 24 weeks. Then MMP-2 expression decreased in the 36-week group but still significantly higher than the control group. There was no significant difference among the 3 subgroups for different intrusion times(P>0.05). CONCLUSIONS: MMP-2 participates in remodeling of the periodontal tissue during tooth intrusion. The expression of MMP-2 is not significantly increased with the extension of the intrusion time with cyclic intrusive force, which suggests that with the use of mini-screw to intrude the molars with cyclic intrusive force, the periodontal tissues of the intruded tooth maintain dynamic balance of bone remodeling.

Cloning and characterization of a salt responsive gene AcPsbQ1 from Atriplex canescens.

PsbQ is an extrinsic subunit of the photosystem II in eukaryotic photosynthetic organisms. Numerous studies have demonstrated that PsbQ can stabilize the inorganic cofactors and enhance the oxygen release in PSII. The decrease of photosynthesis rate under salinity condition is normally attributed to the high concentration of injurious ions, such as Na(+) and Cl(-), which accumulate in the chloroplast and damage thylakoid membrane under salinity stress. In this study, AcPsbQ1 was isolated from a halophyte Atriplex canescens cDNA library. The AcPsbQ1 contains an open reading frame of 699 bp encoding a 233 amino acid protein. In order to investigate its function, AcPsbQ1 was cloned and transformed into Saccharomyces cerevisiae INVSc1. The heterologous expression of AcPsbQ1 in transgenic yeast significantly helped to increase the adapting and recovery ability of yeast cells under the salt and drought. Quantitative real-time PCR assay was performed to reveal the expression pattern of AcPsbQ1 under different abiotic stresses. On exposure to NaCl stress, the transcript level of AcPsbQ1 was significantly enhanced. AcPsbQ1 expression level was also up-regulated under drought stress. These results indicated that AcPsbQ1 might involve in the response to salt stress in A. canescens.

A heavy metal-associated protein (AcHMA1) from the halophyte, Atriplex canescens (Pursh) Nutt., confers tolerance to iron and other abiotic stresses when expressed in Saccharomyces cerevisiae.

Many heavy metals are essential for metabolic processes, but are toxic at elevated levels. Metal tolerance proteins provide resistance to this toxicity. In this study, we identified and characterized a heavy metal-associated protein, AcHMA1, from the halophyte, Atriplex canescens. Sequence analysis has revealed that AcHMA1 contains two heavy metal binding domains. Treatments with metals (Fe, Cu, Ni, Cd or Pb), PEG6000 and NaHCO3 highly induced AcHMA1 expression in A. canescens, whereas NaCl and low temperature decreased its expression. The role of AcHMA1 in metal stress tolerance was examined using a yeast expression system. Expression of the AcHMA1 gene significantly increased the ability of yeast cells to adapt to and recover from exposure to excess iron. AcHMA1 expression also provided salt, alkaline, osmotic and oxidant stress tolerance in yeast cells. Finally, subcellular localization of an AcHMA1/GFP fusion protein expressed in tobacco cells showed that AcHMA1 was localized in the plasma membrane. Thus, our results suggest that AcHMA1 encodes a membrane-localized metal tolerance protein that mediates the detoxification of iron in eukaryotes. Furthermore, AcHMA1 also participates in the response to abiotic stress.

Mechanical properties of nickel-titanium archwire used in the final treatment phase of Tip-Edge Plus technique: an in vitro study.

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

[Comparative studies of casein phosphopeptide-amorphous calcium phosphate and fluoride products in inhibiting enamel demineralization].

OBJECTIVE: To evaluate casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) and several fluoride products in inhibiting enamel demineralization. METHODS: 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. RESULTS: 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). CONCLUSIONS: 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).

[Expression of CD133+ endothelial progenitor cell in rat periodontal tissue during tooth movement].

OBJECTIVE: To investigate the expression patterns of CD133+ endothelial progenitor cell (EPC) on Wister rats during experimental tooth movement. METHODS: 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. RESULTS: 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). CONCLUSION: CD133+ EPC participated vascularized reaction in periodontal tissue of rat during the experimental tooth movement, direct participation was few and indirect effects possibly existed.

[Quantification of remineralized effect of casein phosphopeptiode-amorphous calcium phosphate on post-orthodontic white spot lesion].

PURPOSE: The aim of this study was to quantify the changes in post-orthodontic demineralized enamel lesion surface areas after using casein phosphopeptide-amorphous calcium phosphate (CPP-ACP). METHODS: Ten orthodontic patients (mean age, 17.7 years) were involved in this study who had multiple decalcified enamel lesion after fixed orthodontic therapy. Ten percent of CPP-ACP paste (GC Tooth Mousse, Recaldent, Europe) was taught to spread on tooth surface two times per day immediately after tooth brush. Standardized intraoral images were taken before and after using it. Image analysis software Image-Pro Plus was used to quantify the visible areas of the demineralized lesions which were expressed as a percentage of total labial surface areas of each tooth. The measurement data before and after using CPP-ACP for 1 month and 2 months were analyzed by paired t test. The measurement of image was repeated again 1 month later to determine the repeatability of the method by calculating the intraclass correlation coefficient between the two results of analysis with SPSS13.0 software package. RESULTS: CPP-ACP significantly reduced the visible enamel demineralization (P<0.01, paired t test). The mean reduction in lesion size after treatment was 4.89%(SD:2.05%; 95% CI: 1.93%-8.77%) for 1 month, and 2 months was 8.359%(SD: 3.472%; 95% CI: 3.76%-15.01%). The intraclass correlation coefficient between the two measurements was 0.968. CONCLUSIONS: CPP-ACP can effectively improve the long-standing postorthodontic demineralized enamel white lesion, and the intraoral image analysis is an reliable and repeatable method to measure white spot lesions. Supported by Research Fund from Bureau of Science and Technology of Changchun City (Grant No. 2008108).

[Biological characters of Bemisia tabaci (Gennadius) experimental population on cotton varieties in Xinjiang].

The development, survival, reproduction, and life-span of Bemisia tabaci (Gennadius) on six major cotton varieties (Xinluzao 8, Xinluzao 16, Xinluzao 17, Zhongmian 35, Kang 5, and Dai 80) in Xinjiang were studied under the conditions of (26 +/- 1) degrees C, relative humidity (75 +/- 1)%, and illumination L:D = 16:8 in laboratory. The life table of the B. tabaci experimental population was established, and the population net reproductive rate (R0), intrinsic rate of increase (rm), mean generation time (T), and finite growth rate (A) were estimated. Significant differences were observed in the size, development duration, survival, and fecundity of the experimental population on the six cotton varieties. The fecundity and survival rate of B. tabaci were the highest on Xinluzao 16 and the lowest on Kang 5. Xinluzao 16 was the most appropriate host for the growth and development of B. tabaci population, followed by Zhongmian 35, while Kang 5 was the most unsuitable host.

[Study of 5-bromodeoxyuridine labeling of endothelial progenitor cells from the circulating blood from tooth movement rat].

OBJECTIVE: To investigate the optimal dosage and timing for 5-bromodeoxyuridine (BrdU) labeling of endothelial progenitor cells (EPCs) from rat circulating blood. METHODS: 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). RESULTS: 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). CONCLUSION: 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.

[A three-dimensional finite element study on composite archwire applied in extraction cases].

OBJECTIVE: To explore mechanical properties of the composite archwire (CoAW) applied in extraction cases. METHODS: 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. RESULTS: 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. CONCLUSIONS: The stress on teeth closely correlated with the diameter of the composite archwire.

[Effects of He-Ne laser irradiation on the expression of transforming growth factor beta1 during experimental tooth movement in rabbits].

PURPOSE: The purpose of this study is to investigate the effect of He-Ne laser irradiation on the expression of transforming growth factor beta1 (TGF-beta1) during experimental tooth movement in rabbits. METHODS: Thirty-five rabbits were used in this study. The animals were randomly divided into 7 groups equally: normal group and experimental (1, 3, 5, 7, 14, 21 days) groups, 5 rabbits in each group. An orthodontic appliance, consisting of a coil spring was ligated to the bilateral first maxillary molar and connected to an orthodontic wire ligated onto the incisors, and exerting a force of approximately 80 g. The left side was used as control, and the right side was designed as irradiated side. The animals from each group were sacrificed at the time discontinued. The histological sections were proceeded with immunohistochemical staining of TGF-beta1. Then it was analyzed by Computer Image Analyzing System and statistically processed with SPSS10.0 software package for the paired Student's t test. RESULTS: The expression of TGF-beta1 was demonstrated in the area of tension and pressure of periodontium tissue in both of the irradiated and control sides. The TGF-beta1 staining in the pressure area of the irradiated side decreased significantly at 1 day (P<0.05) compared with the control side. TGF-beta1 staining increased significantly at 3 to 5 days in the pressure area (P<0.05). But in the tension area of the irradiated side, TGF-beta1 staining were significantly increased at 3 to 7 days (P<0.05). The peak value of the area of tension and pressure both appeared at the same time of the 5th day. CONCLUSION: It is concluded that He-Ne laser irradiation can effectively accelerate the expression of TGF-beta1 in periodontal tissue of rabbits during experimental tooth movement.

[Mechanical analysis of composite archwire applied to anterior malocclusion with extraction of bilateral first premolars].

PURPOSE: To optimize the structure of composite archwire applied to anterior malocclusion with extraction of bilateral first premolars. METHODS: The mandibular model was scanned by spiral CT and 30 CT images were obtained, then the mandible finite element model and the archwire model was respectively established by means of SOLIDWORKS software and ANSYS software, mechanics analysis and calculation were carried out. RESULTS: The force produced by composite archwire applied to anteriorly malocclused teeth in the model was greater than by TiNi shape memory alloy but smaller than stainless steel: F(SS)>F(CoAw)>F(NiTi); As the diameter of NiTi in the composite archwire increased (the diameter of stainless steel kept unchanged) , the force on the malocclused teeth gradually increased; As the diameter of stainless steel in the composite archwire increased (the diameter of NiTi kept unchanged),the force on the malocclused teeth increased accordingly. CONCLUSION: The rigidity of the composite archwire increases as the the diameter of NiTi increases; the rigidity of composite archwire also increases as the the diameter of the stainless steel increases.Supported by Research Fund of Jilin Provincial Bureau of Science and Technology (Grant No.20030539-3).

[Dental arch characteristics of the facial asymmetry].

OBJECTIVE: To study the characteristics of dental arches in the patients with facial asymmetry. METHODS: 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. RESULTS: 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). CONCLUSION: 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.

[Epidemiologic characteristics of influenza in China, from 2001 to 2003].

OBJECTIVE: To understand the epidemiologic characters of influenza in China from 2001 to 2003. METHODS: 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. RESULTS: 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. CONCLUSION: 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.