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15 November 2012, Volume 5 Issue 11 Previous Issue    Next Issue

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Diagnosis and location for ambushed and impacted tooth XU Lai-qing，JIANG Meng，DING Hong，LI Na，WANG Hu. 2012, 5(11): 641-645.  Abstract ( )   Cone beam computed tomography（CBCT）which permits to execute three-dimensional reconstructions on axial，sagittal and coronal planes can accurately demonstrate the diagnosis information of the ambushed or impacted teeth，including the shape，location，amount，orientation and the relationship with adjacent structures.

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Diagnosis and treatment of impacted posterior teeth DUAN Yin-zhong. 2012, 5(11): 646-653.  Abstract ( )   Compared to anterior impacted teeth，posterior impacted teeth are greatly different in the ideals of designments and treatments. This article has introduced the cause and treatments for upper and lower impacted premolars and molars，especially for the third impacted molars. Treatment for impacted posterior teeth mainly focuses on the functions but not esthetics. Extraction therapy can be chosen for difficult eruption. The third molars will mesially drift and erupt when the decayed first or second molars are extracted.

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Orthodontic treatment for labially impacted canines HE Hong，HUA Fang. 2012, 5(11): 654-657.  Abstract ( )   It has been a challenge for orthodontists to treat labially impacted canines. There are lots of papers concerning the orthodontic treatment of impacted canines in the literature， however the selection of treatment methods varies a lot among them. In order to provide references for clinicians， this article discusses the prevalence， etiology， examination， early diagnosis， as well as preventive and orthodontic treatment methods of labially impacted canines.

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Surgical-orthodontic eruption of impacted teeth ZHOU Hong-zhi. 2012, 5(11): 657-661.  Abstract ( )   Ectopic impaction of the functional tooth is a kind of complicated mal-occlusion. Orthodontic eruption of such tooth，in cooperation with surgical assistance，is usually necessary to rebuild aesthetics and function of the natural dentition. Oral surgeons play important roles in the procedure，which needs the capability or knowledge of the general design of the treatment，localization of the impact tooth，analysis and clearance of the obstruction，surgical techniques for the exposure，and healing mechanics of the eruption. Good surgical treatments are essential for the comfort of the patient，duration time of the procedure，and final success of the orthodontic eruption.

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Orthodontic treatment for inverted impacted upper central incisors JIN Zuo-lin，HUI Wen-ting. 2012, 5(11): 661-665.  Abstract ( )   The inverted impacted upper central incisors are unusual in clinic. Compared to other impacted teeth，the ideals of designments and treatments are different. The lost upper central incisors will affect the esthetics and functions， so it's better to receive treatment as soon as possible，which contributes to the reestablishment of the patient’s self-confidence. This article has introduced the causes， treatments and retention in inverted impacted upper central incisors.

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Orthodontic treatment of palatal impacted canines LIU Yi. 2012, 5(11): 665-670.  Abstract ( )   Impacted teeth are one of the most common abnormalities of tooth development，impacted canines have the most incidence rate，and palatal impactions are more than labial impactions. It has always been a challenge that how to diagnose and treat palatal impacted canine accurately. Locations of impacted canine are getting easy with the help of CBCT. Surgical exposure has less bleeding because of laser’s usage，which facilitates the bonding procedure. Canine traction processes are arranged in order，which increase the efficiency of whole treatment. Soft tissue considerations and fixed retention for 3-6 months are needed for a perfect result.

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Construction and identification of PG0352 mutant stain in P. gingivalis W83 LI Chen*，HE Xiao-ning，PAN Ya-ping，GUO Yan. 2012, 5(11): 671-676.  Abstract ( )   Objective    To construct PG0352 mutant strain and identify it by PCR，RT-PCR and spot assay. Methods       This study was carried out at Center Laboratory of China Medical University Affiliated Stomatology Hospital from July to December 2011. We construct the transformation cassette including PG0352 upstream gene，erm gene and PG0352 downstream gene，transformed this cassette to P. gingivalis W83 by electroporation and screened in TSB agar plate including erythromycin and identified these strains by PCR，RT-PCR and spot assay. Results    There were colonies in TSB agar plate，PG0352 gene was placed by erm gene，and the enzymic activity was abrogated. Conclusion    PG0352 mutant strain can be obtained，which is necessary to clarify the function of PG0352.

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Effects of Er﹕YAG laser on bond strength between dentin and VITA MarkⅡ blocks LI Rui-qing*，ZHAO Bin，YAN Hui，ZHANG Yuan. 2012, 5(11): 676-678.  Abstract ( )   Objective    To observe the bond strength between dentin and VITA MarkⅡblocks after Er：YAG laser. Methods    Thirty human premolars extracted were chosen，grinding the mesial and distal surface of each premolar，then get 30 dentin samples for 3 mm×3 mm respectively. All the dentin samples were randomly divided into four groups，10 samples in each group：Group 1，Er﹕YAG laser（60mj，2Hz）；Group two，acid etching（35% phosphoric acid）；Group 3，acid etching combined with Er﹕YAG laser. 2 samples were randomly chosen from each group and observe the morphological changes of dentin with SEM；the other 8 samples of each group were bonded with VITA MarkⅡblocks by 3M ESPE RelyX Unicem. Compare the bond strength between dentin and VITA MarkⅡblocks after bond strength test. Result    The bond strength in the group of acid etching combined with Er﹕YAG laser showed the highest（20.4504），and there was statistically significant difference with the other groups（P＜0.001）. There was no statistically significant difference between the group of acid etching （15.2624）and Er﹕YAG laser（15.2360）. Conclusion    Acid etching combined with Er﹕YAG laser could significantly enhance the bond strength between dentin and VITA MarkⅡblocks.

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A survey and analysis of Permanent teeth caries in 12-year-old children in Daqing city YOU Xin，LIU Huimin，ZHENG Jie,MA Shu-yan，DONG Jie. 2012, 5(11): 679-681.  Abstract ( )   Objective    To investigate the current statues of caries in permanent teeth and development  trend of the disease among 12-year-old students in Daqing，and to provide scientific fundation to guide the oral health. Methods           A total of 510 students were randimly selected in Daqing for disease epidemiology investigation .The results were analyzed by using statistical software SPSS17.0 . Results    The prevalence of caries was  27.06%和32.11%， which showed no difference（P＞0.05）.The filling rate of students in 2011（15.1% ）was higher than that in 2010（9.5%）（P＜0.05）.The DMFT was 0.58 ± 0.77和0.68 ± 0.98 ，which showed no difference（P＞0.05）. The prevalence of caries of female（30.43%）was higher than male（21.24%）（P＜0.05）. Conclusion    The caries rate is at low level among 12-year-old students in Daqing，which increaseds with age. The growth rate of caries in female is higher than in male. Dental caries filling rate is low.

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Experimental study of the bonding interface between different base material and veneering porcelain  LI Zhen-chun，WANG Xiang，XING Wen-zhong. 2012, 5(11): 682-685.  Abstract ( )   Objective    To observe the changes of chemical elements between the different base material and the veneering porcelain with the electron probe，and analyze the pattern of chemical combination of the different base material and the veneering porcelain. Methods    Using the maxillary lateral incisor as a model，Ni-Cr alloy，zirconia，the Au-Pd alloy，press casting ceramic，Co-Cr alloy and mixed Au-Pd alloy base crown were selected and fired opaque and body porcelain respectively according to the recommended procedures by manufacturere. The thickness of ceramic layer was controlled with in 2mm on the labial side. The experimental sample was cut with the low speed diamond saw. Grind， polish and ultrasonically clean the cut surface. The zirconia sample and press casting porcelain sample were sprayed with gold in vacuum. Then observe the interface with electron microscopy， and analyze the situation of the elements exchange and transfer with the line scan and point scan of electron probe in the interfacial depth of about 10 μm. Results    Element diffusions appeared between the Ni-Cr alloy，zirconia，the Au-Pd alloy，Co-Cr alloy，mixed Au-Pd alloy base crown and veneering porcelain. Some elements could penetrate into veneering porcelain in the range of 1-2 μm，and the extent of element diffusion weakened until it disappeared with the increase of depth. The interface of press casting porcelain crown and veneering porcelain was not found. Conclusion    The composition between press casting crown and veneering porcelain is homogeneity. There is chemical combination between the 5 kind of base crown and the veneering porcelain during the process of firing.

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A primary study of the occlusal function in Class Ⅱ division 1 malocclusion before and after orthodontic treatment WANG Yan-ling*，HAN Liang，ZHANG Yong，ZHANG Jin. 2012, 5(11): 686-691.  Abstract ( )   Objective    Compare the occlusal function change of patients with Class Ⅱ division 1 malocclusion before and after orthodontic treatment， to evaluate the influence of orthodontic treatment on occlusal contact change，which incorporated with the data of foreign and domestic researchers，to comparatively analyze the reliability for occlusal reconstruction and the instructional significance for clinics on Class Ⅱ division 1 malocclusion.  Methods    T-scan Ⅱ system 4.02 was used to record total occlusal force （TOF），asymmetry index of occlusal force （AOF），center of force （COF），maximal movement of COF （MMCOF）and time of occlusion （TO） before and after orthodontic treatment of 30 ClassⅡ division 1 malocclusion patients（age averaged 12.33 years） with integrity dentition in the maximum intercuspation（MIP），and T test was used for statistical analysis. Results    After orthodontic treatment，TOF was increased gradually， and there was significance between before and after orthodontic treatment，preoperative level （P＜0.05）. COF was in the grey ellipse，which was much closer to the center of grey ellipse and maxillary medial line to the preoperative level （P＜0.01）；AOF，MMCOF and TO were lower after treatment preoperatively，and significant difference was observed（P＜0.01）. Conclusions    The result suggest that，premature contact，occlusal interferences and other unbalanced occlusal diseases may exist in ClassⅡ Division 1 malocclusion，After orthodontic treatment，the occlusal force and balance on Class Ⅱ division 1 malocclusion patients can be improved. The occlusal contact the T-scan Ⅱ system reflects is objective，exact and precise，and the measurement results of T-scan Ⅱ could be the marker for the clinic.

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Angle class Ⅲ malocclusion treated with tongue crib and chin cup TIAN Yu-lou，PIAO Mei-ling，WANG Jing，LIU Fang，HAN Kun，Lü Pin. 2012, 5(11): 690-693.  Abstract ( )   Abstract：Objective To summarize the application of tongue crib to correcting bad tongue habit to treat anterior crossbite. Methods A total of 24 cases of anterior crossbite were chosen for this study. There were 12 males and 12 females，aged from 5 to 11 years with average age of 7.5 years. All cases were treated by tongue crib to correct bad tongue habit and eliminate the abnormal thrust to the mandibular arch;chin cup was used to restrain the over-growth of mandible. Results When treatment finished，all the 24 cases obtained satisfactory results，and tongue bad habit and position were corrected;anterior crossbite was corrected;occlusion was perfect and facial profile was improved. Conclusion Tongue crib can effectively correct bad tongue habit and position，eliminate the abnomal thrust to the mandibular arch. It is a preferable scheme of interceptive orthodontics for anterior crossbite.

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Effect of photopolymerization on microhardness of dual-polymerized resin around a translucent fiber post in root canal DENG Xiang-dong，ZOU Kang-yuan，CHEN Jue-qing. 2012, 5(11): 694-696.  Abstract ( )   Abstract：Objective    To evaluate the effect of photopolymerization on adhesion of dual-polymerized resin cement at three locations when a translucent fiber post was used. Methods    Single-rooted bovine teeth received fiber post systems using a dual-polymerized resin cement. In Group 1，the posts were cemented but not photopolymerized，and in Group 2，the posts were both cemented and photopolymerized. After cementation，approximately 1.5 mm thick sections were obtained for regional microhardness evaluations. Results    The microhardness of resin near the canal orifice was significantly higher than others. Conclusion    The mode of polymerization of the cement tested in combination with the translucent fiber post system dose not affect the microhardness of the cement in the root except that near the canal orifice.

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The mechanism and influencing factors of denture base resins' sorption and solubility   HUANG Hua-li，ZUO Wei-wen，LUO Meng，ZHU Song. 2012, 5(11): 697-699.  Abstract ( )    Abstract：Denture base resin is an important component of complete denture and removable partial denture. However，its water sorption and solubility and the release of residual monomers often negatively affect its general function and service life，and even are detrimental to patients’ health. In the present paper，we review the mechanism and related issues of denture base resins' sorption and solubility.