Objective To study the position relationship of mesial contact points of maxillary central incisors in young people in Shanghai. Methods CEREC system was used to measure the proportions of the relevant position of mesial contact points from the plaster models of 20 parallel shaped, 20 triangular shaped and 20 barrel shaped maxillary central incisors. SPSS software was used to analyze the results with statistic methods. Results Significant differences were demonstrated in contact point level/length ratios of three kinds of teeth (P<0.05). Correlation and linear regression were significant between the ratios and the width/length ratios of teeth in square shape. Correlation and linear regression were significant between contact point levels and the lengths of crowns of teeth in all kinds of tooth shapes. No significant difference between men and women were demonstrated in each group (P<0.05). Conclusions Differences were demonstrated in position relationships of mesial contact points of maxillary central incisors of teeth in different tooth shapes. The results of this study could be used to provide theoretical basis for clinical treatment of maxillary central incisors.

Objective To investigate the changes of patients' characteristics in the Department of Endodontics in Stomatological Hospital of Jiangsu Province in the past 8 years. Methods A descriptive study was conducted, by analyzing dental records from one dentist in 2010 and comparing with his dental records in 2002. Results There were 880 patients and 1269 teeth during first period (2002), while there were 1912 patients and 3447 teeth during second period (2010). The results showed that there were significant differences in many aspects except tooth position（χ2=2.84， P > 0.05）. The proportion of male patients increased from 29.43% to 35.46%, while the proportion of teenagers (12year- ) and adults (25year- ) decreased from 12.50% to 8.53% and from 74.20% to 69.61% respectively. Proportions of patients with unstable income and patients with low or no income rose from 8.52% to 26.41% and from 14.09% to 24.06% respectively. The proportion of patiens who received complex therapy (root canal therapy and so on) rose from 39.40% to 44.36%. However, the proportion of patients with high-level satisfaction reduced from 38.75% to 19.56%. The per medical expense was promoted from 95 yuan to 180 yuan, and the growth rate (89.47%) was lower than the capita disposable income growth (209.18%) in the same city. Besides, the coverage rate of medical insurance rose from 7.9% to 30.8%. Conclusions There were significant changes in patients' characteristics except tooth position in the Department of Endodontics in the past 8 years.

Abstract：The patients with microstomia couldn’t use traditional maxillary complete denture. In clinical practice, the maxillary complete denture was divided into two parts during the production process and then the two sections were connected together to form the sectional maxillary complete denture with magnetic connector. After 3 years' follow up, the clinical effect was satisfactory. Taking the patients with limited mouth opening for example, the article mostly introduced the fabrication method and clinical application of sectional maxillary complete denture.

Objective To study the different gene expressions of cap stage (E14.5) and early bell stage (E18.5) in murine molar. Methods The mouse molar germ at E14.5 and E18.5 were removed. Gene chip was used to obtain the different gene expressions. Results There were 76 differently expressed genes, 71 up-regulated genes and 5 down-regulated genes. Conclusion In molar germ of early bell stage (E18.5), genes related to cell metabolism, differentiation, formation of polarity, regulating immune response, regulating transcription and translation, signaling molecules and receptors, stress response are up-regulated dramatically. Genes related to cell apoptosis and amino acid metabolism kinases are down-regulated.

Abstract: Objective To evaluate the effects of precious metal porcelain and zirconia all-ceramic crowns on peri-implant tissue. Methods A total of 120 implants from 78 patients were observed one year after restoration of 60 precious metal porcelain and 60 zirconia all-cerami crowns. Parameters included peri-implant marginal bone resorption length（MBL）， periodontal probing depth（PD），modified plaque index（mPLI），modified sulcus bleeding index（mSBI）, interdental papilla index and satisfaction investigation. Results The differences of MBL, PD, mPLI, mSBI, interdental papilla indexes and satisfaction investigation between two groups were not statistically significant (P>0.05). Conclusions The two crowns can both achieve good clinical results，whereas the long-term effects need further research.

Abstract：　Objective　To examine the expression of CXCR4 and CCR7 in oral squamous cell carcinoma (OSCC), and to evaluate the relationship between their expression and the clinicopathology factors， as well as lymph node metastasis of OSCC. Methods　The expression of CXCR4 and CCR7 in 64 cases of primary tumor tissues of OSCC、39 cases of regional lymph nodes metastasis and 10 cases of normal oral mucous tissue were examined by immunohistochemical technique and RT-PCR. and their relation to cliniopathological parameters was also analyzed. Results　In the tumor cells of OSCC, positive expression rates of CXCR4 and CCR7 protein were 62.5% and 65.6%，respectively, and both were significantly higher than those in normal oral mucous tissue(P<0.01). The positive expression rates of CXCR4 and CCR7 in cases with lymph node metastasis were 74.36% and 84.62%, respectively, but those in cases without lymph node metastasis were 44.00% and 36.00%, respectively. The positive expression was significantly higher in patients with lymph node metastasis than that in patients without lymph node metastasis (P<0.05). In regional metastasized lymph nodes, positive expression rates of CXCR4 and CCR7 were no significantly different (P>0.05). RT-PCR also confirmed the presence of positive CXCR4 and CCR7 expression in OSCC. Moreover, CXCR4 and CCR7 expression was correlated with tumor histological type (P<0.05), depth of tumor invasion（P<0.05）,and TNM stage (P<0.01), but not with age at surgery, gender, and tumor size. Conclusion　CXCR4 and CCR7 expression was correlated with the diverse progression of OSCC, including invasion and lymph node metastasis. CXCR4 or CCR7 may become a potential therapeutic target in advanced cases of OSCC.

Accuracy assessment of the CASSOS 2001—computer-assisted simulation system for orthognathic surgery SONG En, MO Kang-nan, ZHU Fu-dong, GE Wei-li, LI Shenglai, XIE Zhi-jian.(Department of Oral and Maxillofacial Surgery, Stomatological Hospital, School of Medicine, Zhejiang University, Hangzhou 310006, China) Abstract：　Objective　To assess the accuracy of the computer-assisted simulation system for orthognathic surgery. Methods　The study consisted of 25 patients with maxillofacial deformity treated with orthognathic surgery. Their lateral cephalograms and color lateral photos of soft tissue before surgery were input to the CASSOS 2001 system. Carry out cephalometric analysis and simulative orthognathic surgery, and predict occlusal relationship and lateral features of soft tissue. Then input the lateral cephalograms after surgery into the CASSOS 2001 system, and carry out cephalometric analysis. Choose ten parameters and compare predicted surgical parameters with actual postsurgical parameters. Results　Results of four parameters of hard tissue and five parameters of soft tissue in this study were similar. There were statistical differences in only one parameter of soft tissue, the labral length. Conclusion　CASSOS 2001 system is precise for the simulation of changes of hard tissue in orthognathic surgery. It has a little shortcoming in the simulation of soft tissue, especially in the prediction of lips. The positioning error of the marking points, and the soft to hard tissue movement proportion have a large influence in the prediction. CASSOS 2001 system still has great room for improvement.

Abstract:　Objective　By fabricating the surgical stents for implants and analyzing the computed tomography data, realize accurate placement of dental implants and aesthetic restoration. Methods　Twenty patients with some teeth missing were chosen. Impressions were taken, and plaster casts were obtained. According to adjacent teeth and jaw relationship in the plaster models, the surgical stents for implants were fabricated. Patients with stents were CT scanned. All the data were analyzed by a teeth and jaw measurement software. Results　CT data reconstruction could accurately obtain three dimensional anatomic structures of implantology site, and the software could accurately measure the width of bone tissue from bucal to lingual side, the height from the top of bone tissue to the mandibular canal or to the bottom of the maxillary sinus. Thickness of the soft tissue could also be accurately measured. Placement and direction of all implants were very good, and no complication happened. Conclusion　The surgical stents for implants and CT imaging analysis can be effectively used to measure structure of the jaw and help doctors to select the lengths and diameters of dental implants.

Objective The aim of our study was to adopt histological observation of effects of bleaching agents in high concentrations on tooth pulp of rats Methods 60 rats were divided into three groups: bleaching with NaF group, bleaching group and control group. Rat teeth in two experimental groups were bleached for 5 minutes, 10 minutes and 15 minutes. Every 5 rats were killed after bleaching immediately, 3 days and 7days after bleaching respectively. Then histopathologic examination of pulp tissue was taken. Results Slight symptoms were observed in one third of all the teeth. No moderate or severe symptoms were observed in all the teeth after bleaching. Slight symptoms could be observed immediately after bleaching, and they generally disappearred 2 weeks later. There were no significant differences berween two experimental groups. Conclusion The findings from this study demonstrated that HP type tooth bleaching treatment in high concentrations might cause mild, localized pulp reactions. No significant changes could be observed when fluoride was used before bleaching treatment.

Objective　To evaluate the clinical value of SMAS and sternocleidomastoid muscle flap in the parotid gland tumor ectomy. Methods　43 cases with parotid gland tumors were randomly divided into two groups, and all of the operations were performed to preserve the facial nerve and greater auricular nerve. The experimental group was treated by filling defect area with SMAS and sternocleidomastoid muscle flap, and the control group was treated by closing the wound directly Results　All patients healed smoothly with no salivary fistula. The rate of Frey's syndrome and the satisfaction of facial sunken deformities in the experimental group were lower than those in the control group (P<0.05). Conclusion　SMAS and sternocleidomastoid muscle flap in parotid tumor surgery can effectively inhibite the rate of Frey's syndrome, and it can achieve long-term cosmetic results. Hence wide use of clinical applications is commended.

Objective To analyse the clinical efficacy of treating periodontal- endodontic combined lesions in 140 cases. Methods 160 teeth with periodontal-endodontic combined lesions in 140 patients were selected and divided into three groups randomly. Group A was treated with combined method of root canal therapy and periodontal therapy at the same time. Group B was treated with periodontal therapy 2～3 months after the root canal therapy. Group C was treated with root canal therapy. Results After one year, the clinical treatment effects of Group A were superior to those of Group B, but there was no statistical significance(P>0.05). The clinical treatment effects of Group A and Group B were superior to those of Group C obviously, and there was statistical significance(P<0.05).Conclusion Combined method of thorough root canal therapy and seasonable periodontal therapy is effective to treat periodontal pulp combined lesions, which can increase teeth' survival rate.

Abstract: Objective To evaluate the corrosion resistance of Vitallium 2000 plus Co-Cr-Mo alloy and pure titanium in artificial saliva with different fluoride and dissolved-oxygen concentrations. Methods ZahnerIM6e electrochemical workstation and THALES analysis software were applied to measure the polarization curves of the two metal specimens in different artificial saliva, and the Ecorr,Icorr and Rp were acquired. Results In 0.05% F-,DO≥8.1 ppm acidic artificial saliva, polarization curves of titanium specimen shifted, Icorr increased and Rp decreased (P < 0.05); however, polarization curves of Vitallium specimen didn't offset, while Icorr and Rp didn't change basically(P > 0.05). When the F- concentration was increased to 0.2% , the polarization curves of both titanium and Vitallium test pieces shifted, Icorr increased and Rp decreased (P < 0.05). When DO≤0.1 ppm ,the polarization curves of both titanium and Vitallium test pieces shifted, Icorr increased and Rp decreased (P < 0.05). Conclusion Low concentrations of fluorine will not affect the corrosion resistance of Vitallium 2000 plus Co-Cr-Mo alloy, but they can reduce the corrosion resistance of pure titanium. High concentrations of fluorine and low concentrations of oxygen will reduce the corrosion resistance of Vitallium 2000 plus Co-Cr-Mo alloy and titanium.

Objective To compare the effects of chloroform, xylene, d-limonene on cleaning root canals in root canal retreatment. Methods 60 mandibular first premolars were randomly divided into three groups, with 20 teeth in each group . A week after root canal filling，different solvents were used to help clean root canals. The treatment time and the volume of the solvents used were compared. Results Chloroform group consumed the least time to get the original working-length. But its overall clinical operation time and amount of solvent used was not significantly different with those of xylene group(P<0.05). All kinds of clinical operation time were significantly longer in d-limonene group(P<0.05), and more solvent was used(P<0.05). Conclusions In clinical operations, xylene can be used instead of chloroform for fast root canal cleaning. If there is no strict requirement on operating time, d-limonene may be a better choice.

Objective To evaluate and compare the effects of Oravive， Nd:YAG laser and the the combination of the two methods on dentin hypersensitivity. Methods 40 patients with 407 teeth affected by DH（dentine hypersensitivity） were included in the trial. Selected patients were randomly assigned to control group, Oravive group, Nd:YAG laser group or combination group, with 10 patients in each group. DH was assessed with visual analog scale (VAS) before treatment and 30 minutes, 1 week and 6 months after treatment. Results Oravive group resulted in most significant reduction in VAS scores 30 min and 1 week after treatment, while Nd:YAG laser group had obvious desensitizing effects 1 week and 6 months after treatment. The combination group played well at each time point while the control group showed no significant changes throughout the study period. Conclusion Within the limits of the study, Oravive and Nd：YAG laser irradiation both had obvious effects in the treatment of DH, and it’s more effective when they were combined.

Objective To carry out aesthetic restoration of anterior teeth residual roots by orthodontic traction. Methods 11 cases of residual roots were choosn, 7 with root fracture and 4 with root caries, were all beneath gingival margin, and after orthodontic traction, they were then restored with post crown. Results Of 11 cases, one was extracted due to severe periapical inflammation, while the others were rehabilitated with post crown after the root extractions to 2-3.5mm. The treatment was effective and the patients' satisfaction was achieved with the prevalence of 91%.Conclusion The method could increase the bone mass around tooth roots. The crown-root ratios were close to the natural teeth. The coordination of restoration and adjacent teeth, aesthetics and comfort were improved effectively.

Abstract： Objective To compare the fatigue resistance of residual crowns of molars restored with two post and core materials. Methods 20 residual crowns of first mandibular molars were collected, divided into two groups randomly and restored with fiber post-and-core crowns and cast metal latch type fission post-and-core crowns. The fatigue resistance test was implemented, and the values of fatigue resistance and modes of fracture were recorded and compared. Results Residual crowns of molars restored with cast metal latch type fission post-and-core crowns could obtain good fatigue resistance compared with the group restored with fiber post-and-core crown, and the difference had statistical significance (P﹤0.05). Conclusions Restoration of molar residual crowns with cast metal latch type fission post-and-core crown can get better mechanical properties than restoration with fiber post-and-core crown. For patients with habits of sleep bruxism together with tooth clinching, methods like decreasing cusp inclination should be adopted to reduce the vertical and lateral occlusal force.