The manuscript for the first time put emphasis on the integral characteristics of apical region of mammalian developing tooth root, which we preliminarily proposed as developing apical complex（DAC） by deducing from the fact that this region features distinctive signatures for a structurally and functionally integral entity and leads the simultaneous formation of tooth root and periodontium. In this article, the histological and cellular characteristics and developmental capability of DAC were evaluated. And it was proved that DAC featured a unique“embryonic”characteristic, which not only provides a proper root/periodontal microenvironment, but also contains stem/progenitor cells capable of differentiation into multiple tooth root- and periodontium-forming cells. The sustainable development ability of DAC qualifies it as the growth center of tooth root and as a promising candidate source of cells for tooth root and periodontal regeneration.

Objective To investigate the structure, mechanical and low temperature aging properties of colored dental zirconia ceramics. Methods 5 graded colored dental zirconia ceramics were made by adding colorants and their combinations into a 3Y-TZP（tetragonal zirconia stabilized by 3mol% yttrium） powder, the green body were compacted at 200 MPa, pre-sinter at 1 050 ℃ and maintained for 2 h, then densely sintered at 1 500 ℃ for 2 h. Specimens were cut from each of the 5 graded colored blocks. Physical, mechanical properties as well as chemical stability were tested, microstructure were observed, crystalline phase were identified by X-ray diffraction（XRD）, aging properties were assessed by measurement of the relative content of monoclinic phase and bending strength testing. Results The overall density of colored zirconia ceramics was over 99.7%, linear shrinkage was about 20%, while thermal expansion coefficient was about 11×10-6·℃-1, the crystalline phase was tetragonal, bending strength was over 900 MPa which was slightly lowered than that of the uncolored zirconia, fracture toughness was slightly higher. Good chemical stability in acetic acid was observed. After aging treatment, tetragonal-to-monoclinic phase transformation was detected up to 40%, while bending strength was not significantly degraded. Conclusion The results showed that colored 3Y-TZP ceramics presented good mechanical properties even after aging treatments, and was suitable for dental clinical use.

Objective To select three kinds of perforation repair materials, mineral trioxide aggregate（MTA）, Z350, amalgam. And to evaluate the cytotoxicity of three kinds of perforation repair materials on human periodontal ligament fibroblasts（HPDLF） in vitro. Methods The proliferation of HPDLF to three perforation repair materials were examined by methyl thiazolyl tetrazolium（MTT） assay at 1, 3 and 5 days. The mRNA expression levels of bone -associated alkaline phosphatase（ALP） and osteocalcin（OC） were determined using a real -time quantitative polymerase chain reaction（PCR）. Results MTA shew almost no inhibition to HPDLF, the expression of ALP mRNA and OC mRNA in the HPDLF cultured on MTA were higher. Z350 induced a slight inhibition to HPDLF, and the expression of ALP mRNA but there was no difference in the expression of OC mRNA. Cell proliferation was significantly impaired by amalgam with grade 3, and the expression of ALP mRNA and OC mRNA were significantly reduced. Conclusion MTA have minimum cytotoxicity on HPDLF and can promote cell differentiation and regenerate of periodontal tissue. Z350 have lower cytotoxicity on HPDLF. Amalgam show highest cytotoxicity on HPDLF in the three materials and inhibit cells differentiation.

Objective To evaluate the effect of nicotine on cell proliferation. Methods The cells were cultured with DMEM medium containing 10% fetal bovine serum with 0, 1×10-4 mol·L-1, and 1×10-3 mol·L-1 nicotine for up to 3, 5, 7, 10, 14 days. The cell proliferation was evaluated by MTT. The alkaline phosphatase（ALP） activity was estimated by PNPP. The expression of collagen typeⅠ（COL1） and osteocalcin（OCN） were estimated by reverse transcriptionpolymerase chain reaction（RT-PCR）. Results Nicotine suppressed the cell proliferation. ALP activity increased to peak on 10 days in control and 1×10-4 mol·L-1 nicotine. COL1 expression increased to peak on 10 days in control and 1×10 -4 mol·L -1 nicotine, but there was decreased to the minimum on 10 days and increased on 14 days in 1×10-3 mol·L-1 nicotine. OCN expression increased to peak on 10 days in control, and increased in 1×10-4 mol·L-1 nicontine from 3 days to 14 days, but there wasn′t significant change in 1×10-3 mol·L-1 nicontine. Conclusion Nicotine suppresses osteogenesis through a decrease in ALP and COL1 production by osteoblasts.

Objective To compare the proteomics change of human dental pulp cells induced by recombinant human interleukin -1β（rhIL -1β）. Methods The dental pulp cell entire protein was separated by a two -dimensional electrophoresis（2-DE） technique. The rhIL-1β induction and the normal dental pulp cell protein 2-DE atlas were established. Difference expression protein was confirmed by ImageMaster 2D Elite 5.0 software analysis. To identify differentially expressed proteins spot by matrix -assisted laser desorption/ionization time of flight mass spectrometry, and get peptide mass fingerprinting. Results Comparing the two groups of protein 2 -DE atlas, 39 protein spots were obviously different. Including 15 points in the induction of protein expression were higher, 13 new protein spots, 7 protein points expressions were lower, there were only four points in the control group. After mass spectra identification, 10 protein spots were confirmed at last. Conclusion Pulp cells to rhIL-1β responsiveness is a very complex process, which involve a variety of protein molecules. rhIL-1β related 10 protein spots have been identified in the dental pulp cell for the first time. To explore pulpitis′s early response mechanism provides a new clue and ideas.

Objective To compare the osseointegration and corrosion of different kind of coatings on pure titanium. ethods By plasma spraying technology, nitrogen silicon zirconium-hydroxylapatite（ZrSiN-HA） compound coating as prepared on the surface of pure titanium and the pure titanium was implanted with the mandible of the experimental nimal. The superficial appearance of the compound coating was observed and analyzed by scanning electron icroscope（SEM）. The ZrSiN-HA, nitrogen silicon zirconium（ZrSiN）, hydroxylapatite（HA） and pure titanium were ompared and examined. In the four groups, the bone binding force of coatings were detected, and the superficial ppearance of the break regions were observed by the electronic multipurpose material testing aircraft. In the four roups, the anticorrosive of coatings were compared and examined on the electrochemistry corrosion testing system. esults Experimental results indicated that the implant surface sprayed with the ZrSiN-HA was more compact than hat sprayed with HA. The crystallization was obvious. Compared with the other coatings, the bone binding force of he ZrSiN-HA coating was the highest, and its anticorrosive performance was the strongest. Conclusion The application f ZrSiN-HA coating is advantageous to the long-term retention of implant, and it has huge latent application alue to dental dummy.

Objective To compare the expression of nitricoxide synthase（NOS） in the osteogenesis tissues of gradual distraction and split osteotomy, and investigate molecular biology mechanism. Methods Thirty-six rabbits were randomly divided into gradual distraction group, high split osteotomy group and control group. A batch of 4 animals in each of the first 2 groups were sacrificed respectively on the 1st day, 1st, 2nd and 4th weeks after operation. The local changes of the tissues between bony segments were observed by inspections, radiography, HE staining, and immunological evaluation of NOS. The areas occupied by positive cells with inducible nitric oxide synthase（iNOS） and endothelial nitric oxide synthase（eNOS） were compared statistically within and among different batches. Results Immunologically, little expression of iNOS and eNOS could be detected in normal bone. In gradual distraction group, the iNOS stains were at peak values at 1st day, eNOS at 1st week postoperatively. In split osteotomy group, the iNOS stain were at peak values at 2nd week, eNOS at 1st week postoperatively. The nNOS was not detected in both of the groups. Conclusion Routine procedure of distraction produced better osteogenesis, whereas split osteotomy with free bony segments would lead to abnormal osteogenesis.

Objective To explore the clinical effect of combined application of magnetic attachments and extracoronal attachments in prosthodontics. Methods Twenty-two cases of dentition defect with isolated residual root or residual crown were selected. All the cases accepted the restorative treatment combined magnetic attachments with extracoronal attachments. The clinical effect of dentures and the condition of abutment teeth were evaluated by chief complaint of patients and clinical examination. The follow-up time ranged from 2 years to 4 years. Results Satisfactory functional, stable and esthetic results of dentures were achieved for all the cases. And there was no abutment loosening and no secondary caries. Alveolar bone loss around abutment occurred in 1 case, gingivitis of abutments appeared in 5 cases. Chewing pain occurred in 1 case and unstable state of dentures appeared in 5 cases after the use of denture for 2 years. The dentures of above -mentioned cases were used normally after symptomatic treatment. Conclusion The combined application of magnetic attachments and extracoronal attachments in prosthodontics is an effective treatment option for cases of dentition defect with isolated residual root or residual crown.

Objective To investigate the root canal curvature of permanent anterior teeth from Chuang population. Methods 245 anterior teeth from Chuang population were collected and examined by X-ray radiography both from labiolingual and mesiodistal directions. For 218 type Ⅰ anterior teeth, degree of root canal curvature, radius of curvature and length of the curved part of root canal were measured by a special electronic vernier caliper according to Schneider′s and Sch覿fer′s method and the data obtained were analyzed. Results Root canals of anterior teeth from Chuang population were mainly of type Ⅰ. The number of type Ⅱ, Ⅲ, Ⅳ were about 13 in mandibular central and 12 in mandibular lateral incisors. The incidence of curvature in maxillary central incisors, lateral incisors, canines and mandibular central incisors, lateral incisors, canines were 40%, 80%, 77%, 65%, 66%, 73% in mesiodistal directions, 62%, 69%, 70%, 62%, 41%, 61% in labiolingual directions respectively. The most curvature was moderate and happened in apical third. The heaviest curvature occurred in maxillary canines in mesiodistal direction and mandibular canines in labiolingual direction. The shortest radius and length of curvature occurred in maxillary lateral incisors. Conclusion Root canal curvature of anterior tooth in Guangxi Chuang population is complex. The incidence of typeⅡ, Ⅲ, Ⅳ is high in mandibular incisors.

Objective To get some anatomical knowledge about the second mesiobuccal canal（MB2） of the maxillary second molar of Shandong region by studying the teeth in vitro. The anatomical knowledge may help us to improve the successful rate of root canal therapy of the maxillary molar. Methods 118 maxillary second molars were collected from the different region in Shandong province. Oblique square of pulp opening form was used, then root canals were detected and got through by C-type file. The rate of MB2 detection and getting through was recorded. By taken X-ray, the numbers, the morphologies and classifications of the root canal systems of these molars were recorded. Then the distance between mesiobuccal canal（MB） and MB2 was observed and measured by endodontic operating microscope and digital measurement. At last, we observed the apical foramen from the surfaces of these teeth, and try to analysis the differences between apical foramen and the end points of the roots. Results The rate of MB2 detection was 49.15%, among them 82.76% could be got through by files. 108 molars had three roots, among them, for the mesiobuccal root canal system, 46.30% were Ⅰ root canal system, while Ⅱ and Ⅲ systems were 12.96% and 31.48%, respectively. The distance between MB and MB2 was 1.26 mm averaged. The distance between anatomical apical holes and the end points of roots was 1.13 mm averaged. Conclusion MB2 can be detected in most of maxillary second molars in Shandong region. The dentists should try to detect MB2 in the root canal therapy, and should judge work length by clinical behavior and apical locator rather than by X-ray alone.

Objective To investigate the effects of post space preparation and post restoration on apical sealing ability. Methods 60 extracted mandibular premolars each with single canal were selected. All canals were prepared by manual ProTaper instrument using crown-down technique. The samples were the divided into 5 groups randomly. Group A: 20 samples, the immediate post space preparation group; group B: 20 samples, the delayed post space preparation group; group C: 10 samples, the intact group; group D: 5 samples, a positive control; group E: 5 samples, a negative control. There were two subsets in groups A and B which were restored by temporary materials（A1 and B1）or fiber post and cores（A2 and B2）. Indian ink dye method was used to measure the apical leakage in stereomicoscope. Results The mean length of dye penetration for group A1, A2, B1, B2 and C were （0.52±0.47）, （0.49±0.44）, （1.17±0.77）, （1.12±0.54）, and （0.23±0.40）mm, respectively. Positive group demonstrated maximum dye penetration, and negative group showed no dye penetration. There was no statistically significant difference between group A1, A2 and group C（P >0.05）. However, there were statistically significant differences between group B and group A, C （P<0.05）. The length of dye penetration for group B was longer than that for group A and C. Conclusion The sealing ability was decreased after delayed post space preparation when using the AH-Plus sealer.

Objective To illustrate the morphological changes of mandible after angle-splitting ostectomy. Methods From January 2006 to April 2008, 10 cases had undergone mandibular angle-splitting ostectomy to reduce the width of the lower face. For each patient, CT datum of mandible at three stages （preoperative, immediate postoperative, 6 months postoperative） were collected. By the application software of reverse engineering （Surfacer V9） and true-up and dissection techniques based on three-dimensional spiral computed tomography（3D-CT）, operative efficacy and bone regeneration at the operation area of angle-splitting ostectomy were evaluated 6 months postoperative. Results 1）Concavity could be seen at the angle-splitting ostectomy area 6 months postoperative, especially at the mandibular external oblique line region. Average cup depth was （3.64±1.67）mm by contrasted to preoperative. Diminution of bone volume was 55%±9% for the local operative area 6 months postoperative. 2）Bone regeneration could be seen at the area that mandibular outer cortex had been removed. Compared with immediate postoperative, ratio of neoformative bone was 84.6% ±7.3% 6 months postoperative. The main region of bone regeneration was mandibular angle. Conclusion Mandibular angle-splitting ostectomy is an effective technique for reducing the width of the lower face. Masseter muscular movement should be restricted postoperative to prevent hyperostosis at the angle area.

Objective To establish a new evaluation system of curved root canal deviation by the technique of micro-CT. Methods Curved simulated root canals were prepared with ProTaper NiTi -hand files by crown -down technique. After root canals were scanned by micro-CT and analyzed by image processing software, the planar area and centers′ transportation of each cross-section were compared to evaluate the prepare effect of ProTaper, and a three-dimensional model about it were established. Results The same cross-section′s area of the root canals which was prepared with ProTaper NiTi-hand files were essentially consistent. With the data analysis of micro-CT, a system of combining planar and three -dimensional index to evaluate the root canal deviation were established. The shapes of root canal before and after prepared with ProTaper showed less deviation, which proved the shaping ability of ProTaper could meet the requirements for clinical use. Conclusion A three-dimensional root canal central axis model is established using micro-CT. It provides a new method to analyze the shaping ability of the instrumentation after root canal preparation. It will give us a more direct view to analyze the situation of the root canal deviation combining the two-dimensional image and the three-dimensional model.

Objective To evaluate clinical value of computer assisted technology for locating the impacted tooth. Methods Thirty-five patients with impacted tooth were received spiral CT scan. The DICOM data were processed by Simplant software for locating the impacted tooth. Results The reconstruction images clearly showed detail of the impacted teeth, including 3D surface image, eruption orientation, buccal and lingual location, medial and distal location and relationship with dentition and circumambient anatomic structure. Conclusion The computer assisted technology can localize the impacted tooth precisely and provide valuable information for clinical treatment.

Objective To evaluate the accuracy of Root ZX and Raypex5 root apex locators in detecting vertical root fractures. Methods A total of 20 extracted bi-canal, single-root premolars were extirpated of pulp and expanded to root foramen. The actual length of root canal was measured. The root canal filling amplifier in root canal was hammered and root vertical fractures occurred. The actual length of vertical fracture root canal was measured. Root ZX and Raypex5 were used to measure the canal length in incomplete and complete vertical root fracture respectively. The lengths measured by two kinds of root apex locators were compared with actual canal length. Results All of the simulated vertical root fractures were buccal-lingual fissure through the apical foramen. To incomplete vertical root fracture, Root ZX and Raypex5 couldn′t detect the vertical root fracture. To complete vertical root fracture group, Root ZX and Raypex5 detected the vertical root fracture within ±1.0 mm in 97.5%, 100% respectively. Conclusion The root apex locator lacks of diagnostic value for incomplete vertical root fracture, but provides with preferable veracity for complete vertical root fracture.

Objective To compare the clinical effects and safety of propofol and remifentanil anaesthesia with
sevoflurane and remifentanil anaesthesia for cleft lip and palate repair surgery in children. Methods Forty children
undergoing elective cleft lip and palate repair surgery were randomly divided into two groups, 20 in each group.
Group PR: Propofol and remifentanil anaesthesia; and group S: Sevoflurane and remifentanil anaesthesia. Heart rate
（HR）, mean arterial pressure（MAP）, pulse oxygen saturation（SPO2）, and end tidal carbon dioxide（ETCO2） were observed,
and recorded at the time before the induction（T0）, after 15 min of induction（T1）, after 30 min of in-duction （T2）, and after 1 min of extubation（T3）. The time to extubation, incidence of restlessness, postoperative nausea and vomiting, and the complication of the airway were recorded. Results There were no significantly differences between the two groups with respect to sex, age, weight, category of operation, and the time of operation. In group PR, after the period of induction, two children used atropine for bradycardia. One was 3 years old, and the other was 8 years old. The HR of former was lower than 100 beats per minute, and the latter was lower than 70 beats per minute. The average of HR in group PR was increased after 1 min of extubation compared with that before induction（P<0.05）. In group S, the average of HR was increased in 30 min after induction and 1 min after extubation（P<0.05）, and HR kept in faster range compared with that in group PR（P<0.05） at the 15 min and 30 min after induction. During the operation, SPO2 and ETCO2 of both groups consistently maintained in normal range. The time to extubation was comparable in two groups. The incidence of agitation after surgery was significantly higher in group S（8 cases） than that in group PR（2 cases）. There were no records of nausea, vomiting, asphyxia, and laryngospasm. Conclusion Propofol and remifentanil anaesthesia was more significantly inhibited the HR of children. The emergence agitation has higher incidence in sevoflurane anaesthesia. Both methods can attain extubation requirement quickly.

Objective To compare the expression of CCL28 in minor and major salivary glands and clarify the role it plays in IgA secreting by minor salivary glands in oral cavity. Methods Labial gland and parotid samples were analyzed with real-time fluorescent quantitative PCR assay for CCL28 mRNA. Rank-sum test was used for data analysis using SPSS 10.0 software package. Results CCL28 mRNA was abundantly expressed in labial glands of healthy adults. Its expression was higher than that in parotids（P<0.01）. Conclusion The resuits of this article suggest that the expression level of CCL28 in labial glands is remarkably higher than that in parotids, which reminds us that the high concentration of IgA in minor salivary glands may be associated with their high expression of CCL28.

Objective To evaluate the biological effects of Drynaria fortunei naringin on the proliferation and alkaline phosphatase（ALP） activity of human periodontal ligament cells（hPDLC）. Methods hPDLC were primarily cultured and identified in vitro through enzyme digestion combined tissue culture method. 3-（4, 5-Dimethylthiazol-2- yl）-2, 5-diphenyltetrazolium bromide（MTT） method was used to observe the proliferation of hPDLC with the effects of different concentrations of Drynaria fortunei naringin at difference times. The method recommended by International Federation of Clinical Chemistry and Laboratory Medicine（IFCC） was adopted to investigate the effect of Drynaria fortune naringin on the alkaline phosphatase（ALP） activity of hPDLC. At the same time, we used bright blue method to detect the contents of protein in each sample. Then ALP activity in per milligram protein was accounted. Results Significant proliferative promotion to hPDLC by Drynaria fortunei naringin could be observed at the dose of 10, 1, 0.1 mg·L-1. Significant ALP activity of hPDLC promotion of Drynaria fortune naringin could be observed at the dose of 100, 10, 1, 0.1 mg·L-1 And the dose of 1 mg·L-1 Drynaria fortune naringin had greatest promotion on ALP activity of hPDLC. Conclusion Drynaria fortune naringin might significantly promote the proliferation and increase the ALP activity of hPDLC.

Objective To investigate the antibacterial activity of decoction of Radix glycyrrhizae against Streptococcus mutans（S.mutans） in vitro. Methods The decoction of Radix glycyrrhizae was prepared by boiling particles of Radix glycyrrhizae, the diameter was 0.2-3.2 mm. In distilled water and filtered, the filtrate was collected for study. The minimal inhibitory concentration（MIC） and the minimal bactericidal concentration（MBC） of the decoction against S.mutans were detected using double dilution. The effect of decoction on growth and acidogenic profile of S. mutans were investigated by detecting the Abs of bacteria suspension and the pH value of medium at definite time intervals（0, 3, 7, 12, 23, 40 h） during cultured. Results The MIC determined for decoction was 50 mg·mL-1 and there was no bactericidal effect when concentration of decoction lower than 100 mg·mL-1. The decoction inhibitted multiplication of bacteria significantly and the effects became stronger with concentration increasing. The decoction also inhibitted S.mutans producing acid and the effect became stronger with concentration increasing. The most efficient inhibition were observed when incubated 12 hours. Conclusion The decoction of Radix glycyrrhizae can inhibite the growth and acid-production of S.mutans in vitro.

Objective To investigate and compare the stress of edentulous mucosa and periodontal membranes of the abutments under vertical loads for separated removable partial denture or conical telescope denture. Methods One patient who had lost the second premolar and the first molar on the upper jaw and had Ⅰ mobile abutments was chosen in the study. Two precise three dimensional finite element models were constructed by using screw CT image reconstruction technique and Materialise Mimics, Pro/Engineer WF 2.0, ANSYS Workbench software. Vertical forces were loaded on the two models. Then comparing and analyzing the von Mises stress distribution of the edentulous mucosa and the periodontal membranes of abutments between the separate removable partial denture and conical telescope denture in the software of ANSYS Workbench. Results The von Mises stress values of the edentulous mucosa of separate removable partial denture were larger than that of the conical telescope denture. The von Mises stress values of abutments periodontal membranes of separate removable partial denture were lower than that of conical telescope denture. Conclusion Under vertical loads, compare with conical telescope denture, the separate removable partial denture can protect the abutments.

Objective The aim of this investigation was to study the expression of collagen type Ⅱ in the cartilage of mandibular condyle following asymmetric inter-maxillary traction. Methods Two hundred and twenty SD rats were used in this study（one hundred and four rats loading 0.39 N elastic force, another one hundred and four rats loading 1.18 N elastic force, while twelve rats for control）. The extra-joint device was fixed on the right side by surgery. Half of the experimental group was killed at 3, 7, 14, 28 days. The devices were removed at the 28th day in the rest rats, and the rats were sacrificed at 3, 7, 14, 28 days after removing the device. The type Ⅱ collagen expression levels of all the joints were measured using immunohistochemical techniques. Results The positive expression of the type Ⅱ collagen was mainly observed in the cytoplasm of chondrocyte, especially in maturative and hypertrophic layer. The expression intensity was different in different stages and different sides. Both of the two experimental groups showed the same tendency, while the changes in the light force group were more obviously than the heavy force group. In the right side（force -loading side）, the type Ⅱ collagen expression decreased at the early force -loading period. After the device was removed, the expressions increased immediately but then reach the lowest level. The expression almost recovered to normal level at the end of experiment. In the left side（none force-loading side）, the expression remained increasing after force - loading and reached the peak at the 14th day. Conclusion These results suggest that even in the adult individuals, the chondrocyte showed reaction to the mechanical force by altering type Ⅱ collagen expressionpatterns and it may be the cause of the cartilage remolding after asymmetric inter -maxillary traction. A forward elastic force showed a depressant effect in matrix synthesis, and heavy force had stronger effect. But the rotation of condyle accelerated the matrix synthesis.

Objective To evaluate the feasibility of identifying oral streptococcus by comparing their metabolic profiling, and to find a convenient and rapid way to discriminate oral microorganisms. Methods The pure cultivation of Streptococcus sanguis ATCC 10556 and Streptococcus sobrinus 6715（reference strain） from solid culture were respectively inoculated in TPY liquid medium. Then the growth quantity was measured periodically by turbidimetry and the growth curves of the inoculated bacteria were completed. The culture solutions in the stationary phase of the two bacteria were centrifuged, and then tested with the 1H-nuclear magnetic resonance（1H-NMR） spectrometer respectively. The gained free induction decay（FID） data were all inputted into MestReC Soft and finally transformed into metabolic profiling. The metabolic profils were integrated segmentingly and the results were inputted into SIMCA-P Soft for principal components analysis（PCA）. Results The PCA results showed the obvious clustering phenomena and the points of two group data differentially centralized in two clusters. Therefore, the NMR-based metabonomics profiles can discriminate the two different kinds of bacteria. Conclusion The metabonomics can be expected to be a kind of promising useful method in quick discrimination of oral streptococcus.

Objective To investigate the biomechanical effects of micro-implant anchorage technique with sliding mechanics on maxillary anterior teeth retraction under different implant insertion heights and different retraction hook heights. Methods The three dimensional finite element model of maxillary anterior teeth retraction force system was constructed with CT scanning and MIMICS software and the relationships between brackets, teeth, wire and microimplant were simulating the clinical factions. Then the initial tooth displacement was calculated when the insertion heights were 4 mm and 8 mm and the retraction hook heights were 1, 4, 7, 10 mm respectively. Results With retraction hook height added, the anterior teeth movement changed from lingual crown tipping to labial crown tipping and the intrusion movement was more apparent when the micro-implant was inserted in a higher location. Conclusion The ideal teeth movement control could be achieved by different insertion heights of micro-implant and different retraction hook heights in straight wire retraction force system.

Objective To investigate the effect of experimentally created occlusal disorders（ECOD） on the expression of estrogen in rat condylar cartilage. Methods The model of ECOD was created by moving right upper and left lower first molars anteriorly. The animals in ECOD were sacrificed at 2, 4, 6, 8 weeks later. In removed occlusal disorders group, the moved first molars were extracted at 6 weeks later, and the animals were sacrificed 2 weeks later. The expression of estrogen was detected by SABC technique of immunocytochemistry, and then was analyzed by the density of estrogen-positive chondrocytes. Results 1）Estrogen was abundant in mature layer and hypertrophic layer of rat mandibular condylar cartilage. 2）In control group, the expression of estrogen decreased gradually from 6-week-old to 16-week-old. 3）In both childhood and puberty rats, the expression of estrogen in experiment group was significantly higher at 2 weeks after treatment, while no difference was found at 4, 6, 8 weeks after treatment. However, the expression in removed occlusal disorder group was higher than that in control group and 8 weeks of ECOD group. Conclusion In rat condylar cartilage, the expression of estrogen de-creases with age. Induced by ECOD, the expression of estrogen increases in early stage of remodelling activity.

Objective To investigate the prevalence of tooth erosion of Xuzhou city′s children. Methods The stratified, cluster and random sampling methods were performed. The prevalence of tooth erosion of 1 219 5-year-old children and 786 12-year-old children in Xuzhou city were examined by one qualified dentist. The results of clinical examination were recorded by schedule table. The risk factors of tooth erosion were investigated by questionnaire and analyzed by Logistic regression model. Results In 5-year-old children group, the prevalence of tooth erosion was 10.91%. In 12-year-old children group, the prevalence of tooth erosion was 22.14%. The ranking of tooth erosion were mostly class 1 and class 2. The tooth erosions of class 3 and above were rare. The odds rations for tooth erosion were: Acidic fruits, 1.120; acidophilous milk, 1.062; sport drinks, 1.159; carbonated drinks, 1.151; fruit juice, 1.187; drinking acidic drinks or acidophilous milk before sleeping, 6.102; gastroesophageal reflux disease, 2.311; vitamin C, 1.565; supply chalybeate, 1.598. Conclusion The prevalence of tooth erosions in Xuzhou is extensive. Oral health education and drink and food guidance should be strengthened. The amount and frequency of intake of acidic food and drink should be reduced to promote oral health.

Objective To investigate the epidemiology of dental caries and its correlated factors of 12-year-old children in Dongxiang, Baoan and Yugu races. Methods According to the method of third national oral health epidemiologic investigation, 448 12-year-old children in Dongxiang, Baoan and Yugu races were randomly collected and the epidemiological investigation of dental caries, oral bacteriological detection and oral hygiene behavior were carried out. Results 1）The caries prevalence rate of Dongxiang, Baoan and Yugu races were 40.52％, 44.29％, 46.45％, respectively. The average caries of Dongxiang, Baoan and Yugu races were 0.92, 0.90, 1.13, respectively. 2） The main ranks of Streptococcus mutans in saliva were class 2 and class 3 in Dongxiang and Baoan races. However, it was class 0 or class 1 in Yugu race. The level of Streptococcus mutans in dental plaque was higher in Dongxiang and Baoan races than in Yugu race. 3）The children′s everyday brushing rate was higher in Yugu rance than in Dongxiang and Baoan races（P＜0.01）. But there were no difference between Dongxiang and Baoan races. Conclusion The caries prevalence rates of 12-year-old children in Dongxiang, Baoan and Yugu races are high. The main factors of high caries prevalence rate were low brushing rate and dental plaque couldn′t be removed effectively. Oral health education should be strengthened in the three race areas.

The emergence of allergy caused by Pingyangmycin is rare. A case of allergy caused by minidose and low concentration Pingyangmycin was reported in this article.

A case of 13-year-old female with three-pairs/six-lines of labial frenulums and thumb and forefinger′s deformity was reported. The frenulums of inferior lip were bigger than frenulum of superior lip. There was no family history and her mother didn′t ill with infectious disease and injury in gestation.

Hereditary opalescent dentin is a rare autosomal dominant inherited disease of dentin development. A case of hereditary opalescent dentin was reported, and the pathogenesis, family tree and restoration methods were reviewed.

There are three kinds of mechanisms regulating the growth and development of skeletal tissue：Bone growth, bone modeling and bone remodeling. However, in the current orthodontics literature, there continues to be substantial confusion regarding the usage of the term“bone remodeling”. This article reviews the historical causes for this semantics problem and explains the difference between bone modeling and remodeling, as well as the detailed skeletal regulating mechanisms in the growth and development of cranial-facial bones and orthodontic treatment. At last, this article suggests Chinese orthodontists use the terms“bone modeling”and“bone remodeling”more precisely to avoid scientific confusion and barriers to scientific exchange with other biomedical disciplines.