Based on the data of science citation index expanded（SCIE） and MEDLINE in 2007, this paper briefly analyzed the Chinese research papers product on stomatology. Compared with last year, both of the paper number and their shares in world stomatology field were increased, and the range of these papers was broadened and their influence was bigger. In the rank of organization which has published paper, top five units were the same with last year, but their orders were changed.

According to the supply and demand equilibrium research on stomatological professionals, a conclusion could be drawn that the stomatological professionals are in serious shortage. Some strategies to support the demand of stomatological professionals are raised in this essay, such as widening the teaching objectives, stratified recruiting, enhancing the school-running ability of the main stomatological university and so on.

Along with the rapid development of the dental implantology, there are a lot of new theories and new discovery in the design of the implant itself and the osteointegration process on the interface of the implant-bone. In this paper, platform switching bone preservation technique, theory of contact osteogenesis and distance osteogenesis in the interface of implant-bone are introduced. The relationship of these new techniques, and the theory with the implant design and the surgical consideration are discussed.

Objective To evaluate shrinkage range of cleared teeth caused by nitric acid with different temperature and concentration. Methods 48 human teeth were root canal-prepared and filled, then randomly and averagely divided into six groups on the basis of temperature and density of nitric acid and the condition of whether or not added the oscillate. Group A was 20 ℃ with 6% nitric acid, group B was 20 ℃ with 6% nitric acid and oscillate, group C was 20 ℃ with 3% nitric acid, group D was 20 ℃ with 3% nitric acid and oscillate, group E was 30 ℃ with 6% nitric acid and oscillate, group F was 30 ℃ with 3% nitric acid and oscillate. After achieving the standard of the decalcification, all the specimens were gradually dehydrated, and then cleared and conserved using methyl salicylate. Time-consumed and shrinkage range of all the specimens were recorded and analyzed. Results The time of decalcification in group E was the fastest, then was group F, group B. Group C was the last one. The anastole of the specimens was group E＞group B＞group A, group F＞group D＞group C, group B＞group D, group E＞group D, there was significant difference（P＜0.05）. Group C had significant difference with other groups（P＜0.05）. The anastole rate of the specimens had no significant difference between group A and group B, group C and group D, group B and group F, group D and group F. Conclusion In 20 ℃, 3% nitric acid with oscillate to carry out the decalcification can use less time and get less anastole. The result of the tooth-clearing technique is the best.

Objective To observe sclerotic dentin bonding interfacial nanoleakage used total-etching system and self-etching system by confocal laser scanning microscope（CLSM）. Methods 12 maxillary bicuspids with non-caries, natural cervical sclerotic lesions were divided into three groups. Artifically prepared wedge-shaped lesions were made in 12 sound maxillary bicuspids and divided into three groups as controls. Three kinds of dentin bonding agents, Single Bond（SB）, Clearfil SE Bond（CB） and Xeno Ⅲ（XB）, were applied on the surface of the wedge-shaped lesion dentins according to the manufacturer′s instruction. The apical foramens were occluded with self -curing resin. Six specimen groups were individually exposed to 0.1% rhodamine B isothiocyanate in 50% alcohol solutions for 24 h. Then the teeth were section using slow saw and observed the specimens under CLSM. Results Two-way ANVOA revealed significant influence of both type of the dentin substrate and the adhesive systems tested on the lengths of the dye-penetrated pathways, representing the amount of nanoleakage（P<0.05）. The lengths of the dye -penetrated pathways were longer in SB than in CB and XB, whatever in normal dentin or sclerotic dentin（P<0.05）. While the extension of nanoleakage were similar in CB and XB（P>0.05）. There was no statistical significance in the amount of nanoleakage in normal dentin and sclerotic dentin using SB（P=0.148）. In CB and XB, the amounts of nanoleakage in normal dentin were higher than in sclerotic dentin（P<0.05）. Conclusion The nanoleakage phenomena of bonding interface were observed in three bonding adhesives. In sclerotic dentin bonding interfaces, these nanoleakage phenomenon were located among resin and normal dentin as well as sclerotic dentin.

Objective To investigate the expression of surface antigen of human periodontal ligament cells （PDLCs） and dental pulp cells（DPCs） and the impact of ex vivo expansion to the expression of surface antigen. To provide basis of proper surface antigen for further selection of homogenous stem cell subpopulation from PDLCs and PCs. Methods PDLCs and DPCs were isolated and cultured by collagenase type I and dispase. The expression of surface antigen was analyzed by immunohistochemistry and flow cytometry. Results Positive expression of STRO-1 and CD146 were observed in PDLCs and DPCs by immunocytochemistry. Similar to DPCs, PDLCs expressed mesenchymal stem cell markers STRO-1, CD146, CD29, CD44 and CD106, and displayed negative expression for CD34 at passage 1 by flow cytometry. There were no significant difference of STRO-1, CD29 and CD44 expression level between PDLCs and DPCs（P>0.05）. PDLCs expressed significantly higher level of CD106 and significantly lower level of CD146 than DPCs（P<0.001）. The proportion of STRO-1 and CD146 positive cells decreased steadily with passages in PDLCs and DPCs. Conclusion PDLCs have some similar surface antigen as DPCs, and the stem cells properties of PDLCs and DPCs decreased steadily with passages.

Objective To analyze the stress magnitude and distribution of remaining dentin in posterior residual root restored with post-core crown by three-dimension finite element methods. The variables were number, length and material of post. Methods The models of residual root of maxillary first molar restored with post-core crown were created by CT scanning, Mimics software and Abaqus software. Different number, length and material of posts were used in the modeling. The post was cemented with zinc-phosphate cement. A load of 240 N was applied to the occlusal surface in vertical direction and tensile, shear, and Von mises stresses were calculated. Results The maximum stresses on remaining dentin changed irregularly as the number and length of post. The maximum stresses on remaining dentin decreased slightly as elastic modulus of the material of post increase. Conclusion The number, length, material of post have influence on magnitude and distribution of stress.

Objective To investigate the expression of loricrin（LOR） and cytochrome P450 3A5（CYP 3A5） in oral submucous fibrosis（OSF） and to evaluate their roles in the defending ability of epithelium mucosae. Methods The expression of LOR and CYP 3A5 was examined in the specimens of 66 OSF and 14 normal buccal mucosa samples by immunohistochemistry, and the protein and mRNA expression of them was detected by Western blot and reverse transcriptase-PCR（RT-PCR）. Results LOR was overexpressed in 42（63.6%） cases of OSF, and showed a significant difference only between the early and moderately stages of OSF（P<0.05）, but no clear difference between moderately and advanced stages（P＞0.05）. All normal buccal mucosa tissues showed positive immunoreactivity for CYP 3A5 protein in the membrane and cytoplasm of spinous epithelial cells and cytoplasm of endothelial cells, 5（7.6%） cases of OSF showed weak staining of CYP 3A5 in spinous epithelial cells and 33（50%） showed faint in cytoplasm of endothelial cells. A negative relationship between its expression and pathological stages was found in OSF（P<0.05）. RT-PCR results were fully consistent with the immunohistochemical data. But the results of Western blot only showed the expression of CYP 3A5 was significantly higher in normal buccal mucosa samples than OSF. Conclusion The results suggest that the LOR and CYP 3A5 might play a vital role in the change of defending ability of epithelium mucosae as well as the pathopoiesis and carcinogenesis of OSF.

Objective To investigate the effects of Sol-Gel coating on the corrosion resistance of nickel-chronium alloys in vitro. Methods The bond strength of coating-substrate interface sintered at different temperatures（300, 400, 500, 600 ℃） was tested by scratching method. The Sol-Gel coating was analyzed by scanning electron microscope （SEM）, and its corrosion resistance was assessed by a static immersion method. Results The bond strength of coating- substrate interface reaches the peak at 400 ℃. The Sol-Gel coating can apparently inhibit the release of metal ions and improve the corrosion resistance of nickel-chromium alloy. Conclusion Sol-Gel coating can evidently improve corrosion resistance of the nickel-chromium alloy, which has great potential in prospective clinical practice．

Objective To investigate into the signaling pathway of Porphyromonas gingivalis（P.gingivalis） on cytokine expression in human dental pulp cells（HDPC）. Methods Anaerobic method was employed to culture P. gingivalis, and then HDPC were intracellularly infected by P.gingivalis. The extraction of total RNA, real -time quantitative polymerase chain reaction（qPCR） and enzyme linked immunosorbent assay（ELISA） was used for mRNA expression of Nods and Rip2, protein secretion of interleukin-6（IL-6）. Results HDPC expressed Nods, Rip2 mRNA and IL-6. The up-regulation of Nods and Rip2 mRNA started after P.gingivalis infection, reached maximal level at 2 h, and then decreased at 6 h; whereas elevated IL-6 was found when P.gingivalis infected. Conclusion P.gingivalis activate host innate immune responses in HDPC, and induce IL-6 production through Nod/Rip2-mediated signaling pathway.

Faculty of Stomatology, Capital Medical University, Beijing 100050, China） [Abstract] Objective To evaluate the effect of using dental operating microscope and ultrasonic instruments in treating blocked canals. Methods The etiology of canal blockage included calcification, broken instruments, posts, resinifying, etc. 236 blocked canals were treated with ultrasonic tips under dental operating microscope. The success rate was calculated. Results 178 blocked canals were successfully managed with a success rate of 75.4%. The success rate of each category of the blocked canals were: 71.7% for calcified canals, 81.1% for broken instruments, 100% for canals blocked by posts, 62.5% for canals blocked by resinifying therapy, and 84.1% for canals blocked by filling materials. Conclusion The use of dental operating microscope and ultrasonic instruments is proved to be an effective method in the management of blocked canals.

Objective To set up a clinical evaluation method for the matrix system, and compare two matrix systems, Palodent and circumferential, by this method. Methods 101 molars and premolars with class Ⅱ cavities, which were suitable for resin filling without shift and incline of the adjacent teeth, were randomly divided into study group（Palodent） and control group（circumferential）. There were 79 single cavities and 22 paired cavities. One doctorin- charge completed all cavities filling. Probes were used to test overhang of the filling. Dental floss was used to detect the proximal contact index before and after cavity preparing and immediately and one week after cavity filling. Questionnaires were filled in by patients immediately and one week afrer cavity filling. The tooth models of the filling side were taken, then two doctors-in-charge were responsible for establishing the model evaluation index and one of them conducted the evaluation for all of the models. SPSS 14.0 software was used to analyze the data. Results An evaluation system including questionnaire, clinical examination and tooth model evaluation was set up. There were nine indexes in this system. Moreover, this clinical evaluation system was used in this study. It was found that there were no differences on questionnaire and overhang indexes between the two groups. Palodent matrix system got tighter proximal contact than traditional circumferential matrix system. When filling the paired posterior teeth, Palodent matrix system formed better marginal ridge than circumferential matrix system. Conclusion Palodent matrix system is better than circumferential matrix system in filling the paired posterior teeth.

Objective To evaluate a long-term effect on pronunciation and maxillary growth of elder patients with wide isolated cleft palate after bibuccinator myomucosal island flap palatoplasty. Methods Twelve patients over eight years old with wide isolated cleft palate were selected in experiment group, who received bibuccinator myomucosal island flap palatoplasty. The common group comprised 20 age-matched patients with isolated cleft palate receiving traditional palatoplasty named double-flap method. Simultaneously, 30 randomly selected age-matched noncleft children were included in control group. Both preoperative and postoperative effects over five years on pronunciation and maxillary growth were evaluated using professional, clinical pronunciation system and cephalometric measurement between former two groups. The data of former two groups were compared with control group statistically. Results The incisions of all patients in experiment group healed perfectly. After 5-years′ follow-up, the patients′ mouths opening were normal, no secondary hole on the palate, the flap tissue was softer and more colorful than palate mucosa. The long-term pronunciation effects of patients in experiment group were significantly better than that of preoperation（P< 0.05） and the common group（P<0.05）. The status of maxillary growth of patients in experiment group excelled that in common group significantly（P<0.05）, but no significant difference contrast to that in the control group（P>0.05）. Conclusion Bibuccinator myomucosal island flap palatoplasty is a good operative method for elder patients with wide isolated cleft palate to improve their pronunciation and decrease the affect on maxillary growth.

[ Abstract] Objective To get the information of patients′ understand to the knowledge of artificial teeth prosthetics, provide reference for the propaganda of the prosthetic knowledge. Methods 500 patients were chosen as  the research objects. The survey about patients′ understand to the knowledge of artificial teeth prosthetics was made with a reasonable questionnaire designed by us. The questionnaire contained nine sections. The questionnaires were filled in by the patients, dispatched and received by special messengers. The information of the questionnaires was analyzed and summarized. Results 477 effective questionnaires were received. Patients were more familiar with the knowledge of the opportunity to get the oral prosthetic and less familiar with the knowledge of common problems after the oral prosthetic, the curing process before the oral prosthetic and the visiting times of the ordinary cure. However, they were not familiar with the knowledge of the basic concepts of the oral prosthetic, prosthetic materials and construction of dental prosthetic restoration and announcements after the oral prosthetic. They were most unfamiliar with the knowledge of common problems in the oral prosthetic process. Conclusion The propaganda of the oral prosthetic should focus on the basic concepts of the oral prosthetic, prosthetic materials and construction of dental prosthetic restoration, common problems in the oral prosthetic process and announcements after the oral prosthetic. Meeting such problems, dentists should explain them to the patients patiently.

Objective To analyse dental crown fracture occurrence situation in the long-term mastication process, and discuss the correlation factor of crown fracture occurrence. Methods From December, 2005 to December, 2007, 255 crown fracture teeth were chosen as the object of study. The sex, age, teeth position, fracture position and occlusal state of patients were analyzed. Results In 255 teeth, 1）76 teeth（29.8%） were maxillary first molars, 45 teeth（17.6%） were mandibular first molars, 41 teeth（16.1%） were maxillary second molars, 37 teeth（14.5%） were mandibular second molars, 32 teeth（12.5%） were maxillary second premolars, 15 teeth（5.9%） were maxillary first premolars, 9 teeth（3.5%） were mandibular second premolars. 2）The fracture position of 158 teeth（62.0%） overlapped with pit and fissure. The fracture position of 97 teeth（38.0%） occurred in dental inclined surface. 3）The occlusal state of 85 patients（33.3%） was normal. The occlusal surface shape of 55 patients（21.6%） was unnormal. The occlusal shape of 115 patients（45.1%） was unnormal. Conclusion The teeth position and occlusal state has certain relations with occurrence of dental crown fracture. Occlusal force was the basic factor for dental crown fracture, but it was not the only one.

Objective The purpose of this study was to analyze the changes of hard tissues at each treatment stage in patients with skeletal Class Ⅲ malocclusion after orthodontic-orthognathic surgery, and to assess the longterm stability after treatment. Methods 24 patients with skeletal Class Ⅲ malocclusion were selected. Standardized  lateral cephalograms at the following stages were taken for each patient: Before treatment（T0）, 3 months after surgery （T1）, 1 year after surgery（T2）, 3 years after surgery（T3）. A total of 16 hard tissue landmarks were selected and evaluated at different stages. SPSS 12.0 soft ware was used to study the changes of the hard tissues. Results 1）Comparison of angles between stage T0 and T1, except N-S-Ar, N-S-Ba, N-S-Go, NBa-PtGn and Y axis, other discrepancies all had statistical significances. 2）Comparison of angles between stage T1 and T2, only SNPo and U1-SN had significant differences. 3）Comparison of angles between stage T1 and T3, only U1-SN had an obvious change. 4）Comparison of the angles between stage T2 and T3, all angle changes had no statistical significance. Conclusion From three months to one year after surgery, the hard tissue angles varied more or less, but that did not essentially affect the surgery results. It is concluded that the orthodontic-orthognathic treatment of skeletal Class Ⅲ malocclusion had a long-term stability.

Objective To study the mechanism and applicability of Bite-bumper combined with fixed appliance in treatment of lingual tipping deep bite. Methods 14 children aged 12-16 years old with lingual tipping deep bite participated in the experiment. Bite-bumper combined with fixed appliance was used to correct the deep bite. Clinic effect was observed. Lateral cephalograms were taken before treatment and after bite opening. The related hard tissues were estimated through the cephalograms. Results 1）The average duration for bite-opening with Bite-bumper and fixed appliance of 14 patients was 28 days. 2）After bite-opening, the changes in length direction of jaw（SNA, SNB, ANB） had no statistical variances. Anterior and posterior facial height（S-Go, ANS-Me） were increased. No significant changes were observed in the ratio of posterior facial height to anterior facial height（S-Go/N-Me）, angle of mandibular plane（SN-MP） and Y axis. Labial incline in upper and lower incisors（U1-SN, L1-MP） and interincisa angle（U1-L1） were decreased. The posterior teeth（U6-PP, L6-MP） were extruded and the upper incisors（U1-PP） were intruded. The overbite was decreased. Conclusion Bite-bumper combined with fixed appliance can be used effectively for deep bite correction and improve the short face of patients with lingual tripping deep overbite.

Objective To study the method of induced eruption on multiple adjacent impacted teeth in anterior maxillary bone. Methods Twenty-two multiple adjacent impacted teeth of 9 cases were chosen. The position of the impacted teeth and the relationship to each other were assessed on X-ray images, oral examination and plaster model. The impacted teeth were extracted or induced erupted with the closed-eruption technique and fixed orthodontic appliances. Results Of 22 impacted teeth, 19 impacted teeth were moved into arches by induced eruption with the closed-eruption technique and fixed orthodontic appliances. There were not root adsorption or conglutination for 19 impacted teeth. Three impacted teeth with deformed root were extracted. The average time for treatment was 19 months. Conclusion With correct diagnosis, reasonable design, the complicated impacted teeth could be moved into alignment with good esthetic and functional effect.

Objective To isolate and purify the human periodontal ligament stem cells（PDLSC） and investigate the differentiation potentials of PDLSC into neuron-like cells in vitro. Methods PDLSC were isolated and cultivated. PDLSC of passage 2 was plated at a density of 5×103 per mL. At 80% confluence, the PDLSC were preinduced for 24 hours, and were subsequently replaced with an inducing medium containing certain concentration of β-mercaptoethanal （β-ME）. After 6 hours of induction, the results were evaluated by morphological observation, immunocytochemical staining for neuron specific enolase（NSE）, neurofilament（NF） and glial fibrillary acid protein（GFAP） expression and RT-PCR for NSE, NF, GFAP mRNA. Meanwhile, the uninduced PDLSC were used as a negative control. Results PDLSC could be differentiate into cells with typical neuronal morphology. Immunohisto-chemistry and RT-PCR confirmed that the induced cells expressed NSE and NF, two marked enzymes of neuron cell. Conclusion PDLSC can be induced into neuron-like cells in vitro. PDLSC have the capability of multilineage differentiations.

Objective To evaluate the feasibility of repairing the long defects in rabbits by double -bridging technique and chitosan-collagen chambers. Methods Thirty Chinese rabbits were divided into three groups randomly. 15 mm defects in right facial nerve of rabbits were repaired in three groups: double-bridging（groupⅠ）, nerve autografts （group Ⅱ）, and normal control （group Ⅲ）. General observation, electrophysiological study, histological study and image analysis were performed 12 weeks postoperatively. All results were used to evaluate the nerve regeneration. Results Chitosan-collagen chambers were obviously degraded 12 weeks postoperatively and there was no foreign body reaction at this stage. They also restrain the formation of neuroma and provided a good microcircumambience for nerve regeneration. The recovery of nerve regeneration were good in group Ⅰ . The nerve conduction velocity （NCV） and compound muscle action potential（CMAP） of regenerated nerve were analyzed, which showed that there was no significant difference between the group Ⅰ and group Ⅱ（P>0.05）, but they all did not recover to normal level（P<0.01）. Conclusion Double-bridging technique is a simple method for treatment of long nerve defect and its effect is certain. Chitosan-collage chambers is suitable to implant into body in order to repair a nerve defect with excellent biocompatibility.

Objective To isolate，culture and identify a dog periodontal ligament stem cells（PDLSC） line in vitro. Methods The adult dog periodontal ligament cells were isolated by limited dilution of culture cell for single cell clone. Cells originated from one of these clones were assessed through colony-forming efficiency and immunocytochemistry assay and alkaline phosphatase stain was used to identify the source of adult dog periodontal stem cells, at the same time, PDLSC were induced with mineralizatin solution and was found to have long protrude like an osteoblast. Differentiation of PDLSC were assessed, Mineralized potential was studied by Von-Kossa staining. Results The dog PDLSC expressed STRO-1, which was the marker of mesenchymal stem cells. Also Vimentin, osteoblast-like marker alkaline phosphatase and Collagen-Ⅰ expressed weakly. Cells were clonegenic, highly proliferative cells and capable of differentiating into osteoblasts/cementoblasts. Conclusion The evidence suggests that the cultured cells were stem cells from adult dog periodontal ligament.

Objective To explore whether ultrasound-mediated microbubble destruction can enhance the expression efficiency of plasmid pIRES -rhBMP2 -EGFP for bone morphogenetic protein -2（BMP -2） in mice skeletal muscle. Methods Twenty four male BALB/c mice were divided into four groups. The naked plasmid was injected into the pretibial muscle or the quadriceps muscle（group A and group C） without ultrasound-mediated microbubble destruction method. Micobubbles with plasmid were injected into the pretibial muscle or the quadriceps muscle（group B and group D） with destructing microbubbles by ultrasound immediately. Twelve mice（group A and group B, 30 μg plasmid  injected） were killed after 7 days and the tissue samples of the pretibial muscle were obtained to observe the expression of enhanced green fluorescence protein（EGFP） by inverted fluorescence microscope, gene transfection efficiencies were quantified by counting EGFP positive fibers on mice skeletal muscle. After 14 days, the other twelve mice（group C and group D, 100 μg plasmid injected） were killed and immunnohistochemical technique was applied to detect the rhBMP-2 gene expression. Results The percentage of GFP-positive fibers was significantly lower in the group A than that in the group B. After 14 days, expression of rhBMP-2 was detected in cells and interstitial spaces in the group C and group D, and expression efficiency of rhBMP-2 in the group D was significantly higher than that in the group C. Conclusion Ultrasound-mediated microbubble destruction could enhance the transfection and expression efficiency of rhBMP-2 gene in skeletal muscle of mouse in vivo. It is a new gene therapy method for periodontal regeneration.

Objective To investigate the expression of STK15 and P53 proteins in oral precancerous lesions and oral squamous cell carcinoma（OSCC） and elucidate the possible role of P53/STK15 switch activation -indep dendent pathway in oral carcinogenesis. Methods Formalin -fixed, paraffin -embedded tissues of 8 cases of normal oral epithelium, 27 cases of dysplasia with different degree epithelium dysplasia and 43 cases of OSCC with different differentiation were investigated for the expression of STK15 and P53 proteins by using immunohistochemistry. The clinical and pathological significance of STK15 over-expression in oral carcinogenesis were statistically analyzed by SPSS 12.0. Results STK15 protein was not detectable in normal oral epithelium and significantly altered from milddysplasia to OSCC. The percentage of STK15 over-expression were 40.74%（11/27） in dysplasia and 67.44%（29/43） in OSCC（P<0.05）. The percentage of STK15 over-expression in OSCC with positive P53 staining was significantly higher than that in OSCC with negative P53 staining（P<0.05）. STK15 over-expression was significantly associated with regional lymph node involvement（P<0.05）, while no correlation was found for STK15 over-expression and tumor differentiation, as well as TNM stages. Conclusion STK15 up-regulation was an early event in oral carcinogenesis. The up-regulation of STK15 protein in OSCC may partly result from p53 mutations, which probably contribute a role in lymph node metastasis of OSCC as well. P53/STK15 switch activation-independent pathway may play some roles in oral carcinogenesis.

Objective To investigate the intensity changes of different thickness ratios of Empress Ⅱ glass ceramic and GI-Ⅱ glass-infiltrated alumina ceramic before and after Hertzian contact cyclic fatigue. Methods Disk-shaped specimens of different thickness ratios of EmpressⅡglass ceramic and GI-Ⅱglass-infiltrated alumina ceramic were respectively fabricated. Hertzian contact technique was imposed on the specimens. Critical loads of the specimens before and after 105 cycles loading were recorded. Results The average values of critical loads of all specimens reduced significantly after cycles loading（P<0.05）, and critical loads declined with diminishing thickness of the core ceramic. The critical load of GI- Ⅱ glass-infiltrated alumina ceramic was significantly higher than Empress Ⅱ glass ceramic before and after cycle loading（P<0.05）. Conclusion Cycle loading can reduce the strengths of the two kinds of dental ceramic, and the latter is better than the former in the resistance to fracture and cyclic fatigue. Critical loads of the two kinds of dental ceramic are mainly influenced by the core ceramic′s strength and thickness.

Objective To investigate the transformation of microhardness and microstructures of human dental fluorosis after demineralization and remineralization in vitro. Methods Forty human dental fluorosis enamel blocks were demineralized by acid-etching gel, then subjected to 1.0% casein phosphopeptides stabilized calcium phosphate（CPPCP） for remineralization. Surface enamel microhardness was measured on the enamel blocks before and after demineralization and after remineralization. The enamel specimens was observed by stereomicroscope and scanning lectron microscope, then sectioned（100 μm） and examined by transmission light microscope and polarized light microscope. Results Before demineralization, the average knoop hardness value of the fluorosed teeth was（241.53± 21.31）kHV. After demineralization, obvious decrease of the surface hardness of the enamel was observed, the mean value was（175.76±24.99）kHV（P＜0.05）, the percent of the surface microhardness demineralization（%SMHD） was（27.23± 4.79）%, and major demineralization was under the surface of the enamel, which was similar to the early natural enamel caries. After remineralization, obvious increase of the surface hardness of the enamel was observed, the mean value was（210.17 ±21.48）kHV（P ＜0.05）, the percent of the surface microhardness remineralization（%SMHR） was （52.32±4.23）%, major remineralization was under the surface of the enamel. Conclusion Remineralization could be used to prevent and cure the early natural enamel caries of fluorosed dental teeth.

Objective To establish an efficient and stable method for protein extraction of Streptococcus mutans. Methods The collected bacteria were treated by freeze-thaw and ultrasonic（method 1）, ultrasonic（method 2）, boiling （method 3）, boiling and ultrasonic（method 4）, respectively. The index such as state of bacteria broken, concentration of extracted protein and SDS-PAGE of protein were employed to evaluate the effects of above four methods. Results Beside the method 3, the other three methods could break the bacteria effectively, of which ultrasonic was the key factor. The pattern of SDS-PAGE which treated by method 1, method 2 and method 4 was almost same, but method 1 resulted in the best abundance. There was significantly difference among the four protein concentration extracted by four methods（P<0.05）. All methods exhibited good stability and reproducibility. Conclusion Method of freeze-thaw and ultrasonic resulted in an efficient proteins extraction of Streptococcus mutans which demonstrated good stability and reproducibility and easy to handle.

Objective This study simulated clinical implant surgery using squeeze technique by establishing a rational animal model. To measure the morphologic parameters in order to observe the agglutination of the cancellous bone after being compressed. The study wanted to get some favourable support of implant squeeze technique in bone healing and obtaining primary stabilities of implants, so as to provide some reasonable and valid guidance in the application and improvement of implant squeeze technique. Methods The cancellous bone in condyles of femur of dog had been chosen as the experimental position, prepared the implant holes using squeeze technique according to different compressing extent（0, 0.6, 1.2, 2.0 mm）, and then inserted the corresponding implants into them. After different healing periods（1, 2, 4, 12 weeks）, the mongerl dogs were sacrificed and the hard tissue slices were made and then the morphologic parameters were measured. Results The morphologic parameter of the bone tissue shows that after being compressed, the trabecular bone thickness was almost constant，while the trabecular bone number increased，and the trabecular bone spacing decreased, obviously in the 1-week and 2-week groups. The differences went down gradually along with the extend of healing time. Conclusion The clinical implant surgery using squeeze technique can improve peri-implant bone density so it is good for obtaining primary stabilities of implants.

Objective To describe the periodontal condition of population in Qinghai province and provide basic data for the diseases prevention. Methods Referring to the guideline for the third national oral health survey, the method of multistage, stratified, equal capacity, simple random sampling was carried out in population of 12, 35-44, and 65-74 years old in Qinghai province. Gingival bleeding, calculus, periodontal pocket and loss of attachment of population were investigated. Results 1）In 12, 35-44, 65-74 age groups, the prevalence of gingival bleeding was 98.74%, 97.84%, 92.23%, the prevalence of calculus was 89.76%, 99.87%, 92.87%. 2）In 35-44 age group, the prevalence of shallow periodontal pocket was 34.64%, the prevalence of deep periodontal pocket was 5.58%. In 65- 74 age group, the prevalence of shallow periodontal pocket was 50.45%, the prevalence of deep periodontal pocket was 13.12%. 3）In 35-44 age group, the prevalence of 4-5, 6-8, 9-11, 12 mm or more loss of attachment was 40.74%, 18.78%, 4.82%, 1.78%. In 65-74 age group, the prevalence of 4-5, 6-8, 9-11, 12 mm or more loss of attachment was 71.21%, 51.34%, 20.51%, 7.01%. Conclusion The oral health condition of population in Qinghai province is very poor. The periodontal pocket and loss of attachment was severely. The disease prevention should be strengthen in Qinghai province.

Granulocytic sarcoma of oral cavity is a kind of isolated tumor constructed by immature myeloid cells. Two cases of granulocytic sarcoma of oral cavity were analyzed. The literatures about granulocytic sarcoma were overviewed.

[Abstract] Soft tissue clear cell sarcoma usually occurred in the end of the limbs, especially foot and ankle. Soft tissue clear cell sarcoma occurring in the torso and head and neck were even fewer. In this article, parapharyngeal soft tissue clear cell sarcoma was reported.

Incidence rate of 4 root canals in maxillary second molar is very low and most molars have only two mesiobuccal root canals. The emergence of 4 root canals in maxillary second molar with two lingual root canals is especially rare. A case of 4 root canals maxillary second molar with two lingual root canals was successfully treated and reported in this article.