Objective  To observe the effect of overdose fluoride on the expression of enamelin in rat mandibular incisor. Methods  Twenty Wistar rats were divided randomly into two groups. Animals were maintained in standard environment with free access to food and distilled water（control group） or water added with 100 mg/L F-（experimental group）. The rats were killed in the eighth week. HE staining was used to observe the morphology of ameloblasts.Immunohistochemical staining was adopted to study the expressions of enamelin in rat incisor. Results  The amelo-blasts of the treated rat were arranged in multi-layer. The ameloblasts in group Ⅱ were thinner than those in groupⅠ. The structure of enamel matrix was in disorder. The expressions of enamelin in ameloblasts and odontoblasts were obviously inhibited in group Ⅱ（P<0.01）. Conclusion  The overdose fluoride inhibits the secretion of enamelin and leads to the abnormal development of enamel matrix.

Objective  To investigate the expression of the human interleukin-1 receptor antagonist（hIL-1ra） in the transfected chondrocytes of temporomandibular joint（TMJ）. Methods  Chondrocytes of TMJ in vitro were transfected by hIL-1ra gene via cationic liposome as a medium. The stable transfected cells were selected by G418. The proliferations of the transduced cell were examined with the growth curve, cell population doubling time. The protein expressing in different periods was detected by immunocytochemistry and enzyme-linked immunosorbent assay（ELISA）. Results  The proliferation suppression of gene transfected cells fell significantly with compared to normal cells. The expression of hIL-1ra was detected in the cell plasma and the cell culture supernatant. The highest expression of IL-1ra protein was at the time of 48 hours after gene transfection. The transiently transfected cells were secreted IL-1ra protein continuously 28 days and the stably transduced cells were secreted IL-1ra protein till 72 days. Conclusion  This study showed that hIL-1ra protein expressed positively in the cell plasma and the culture supernatant after gene transfection within a certain periods.

Objective  To find out how to prepare high-density dental ceramics through isostatic pressing so that sintering shrinkage will be reduced. Methods  To prepare Al2O3 /ZrO2 composite powder first, then to mold through dry-pressing, and to shape the green-body through isostatic pressing. The green-bodies were sintered at the tem- perature of 1 400 ℃ and kept at the temperature for different period of time（2 h, 3 h, 4 h）. After that, the
density and fracture strength were measured and the microstructure observed by scanning electron microscope（SEM）.  Results  The sample product′s density, line-shrinkage, and fracture strength of ceramics was rising with the sintering time lengthened. The sample product kept under the temperature of 1 400 ℃ for 4 hours, the fracture strength was（497.27±78.45） MPa and glass phase distributed evenly in the ceramics and the grains were integrated owing to the glass phase. The longer the sintering time, the more even the microstructure was. Conclusion  The sintering quality and the efficiency were improved through isostatic pressing.

Objective  To investigate the cyclic fatigue modes of Vita markⅡ machinable ceramics under Hertzian′s contact. Methods  Hertzian′s contact technique（WC spheres r=3.18 mm）was used to investigate the cyclic fatigue of Vita markⅡmachinable ceramic. All specimens were fatigued by cyclic loading in moist environment, furthermore, surviving strength was examined by three point test and morphology damage observation. Results  In homogeneous Vita mark Ⅱ machinable ceramics, two fatigue damage modes existed after cyclic loading with spheres under moist environment, including conventional tensile-driven cone cracking（brittle mode） and shear-driven microdamage accumulation（quasi-plastic mode）. The latter generated radial cracks and deeply penetrating secondary cone crack. Initial strength degradation were caused by the cone cracks, subsequent and much more deleterious loss was caused by radial cracks. Conclusion  Cyclic fatigue modes of Vita mark Ⅱ machinable ceramics includes brittle and quasi-plastic mode.

Objective  To evaluate the effect of internal matrix on sealing ability and furcal appearance of perforations repair with amalgam and resin. Methods  Perforations created in the pulpal floor of human extracted molars were repaired as follows: Amalgam, amalgam plus calcium sulfate, light-cured resin, and resin plus calcium sulfate（15 teeth/group）. The furcal appearance of samples was evaluated under an operating microscope after repair.
With the leakage test device, coronal 1 mol/L glucose solution was forced toward the pulpal floor. Leakage was measured by the concentration of leaked glucose in bottom reservoir at 1, 2, 4, 7, 10, 15 and 20 days with enzymatic glucose oxidase method. Results  No significant difference was found between group 1 and group 2（P>0.05）. Leakage in group 4 was obviously lower than group 3（P<0.05） after the 7th day. Conclusion   Calcium sulfate significantly improved the sealing effect of resin and provided successful barriers against its overextension.

Objective  To evaluate the clinical effect of treatment of open apices teeth with mineral trioxide ag- gregate（MTA） compared with apexification using Vitapex in the adult. Methods  The root canals of 41 anterior teeth and premolars with single canal and open apices in adults were cleaned and shaped, and then disinfected with calcium hydroxide. The apical root canals of 21 teeth in experimental group were filled with MTA to create a 3—5 mm apical barrier. The remainder of the canals was filled with AH plus and ObturaⅡgutta-percha. The canals of 20 teeth in control were treated with Vitapex. The root canals were then filled with ObturaⅡgutta-percha when the apical barrier could be detected. The visit times, period and result of the treatment were recorded for all cases. Results  Good result was achieved in the most cases in the experimental group. The postoperative X-ray films showed that the canals of 15 teeth were obturated well. 6 teeth showed over-filling by 0.5—2 mm. The recalled patients declared their teeth to be asymptomatic except one. The recall radiographs indicated that the apical radiolucent areas of the teeth with pre-existing apical lesion decreased apparently or disappeared completely, except one tooth with large apical radiolucency. No new radiolucency was found around the roots. In the control group, the apexification of 11 teeth succeeded, and 9 failed. The average visit times was 3.5 in experimental group and 6.0 in control. The average period of the whole endodontic treatment was 11.8 days in experimental group and 306.8 in control. Conclusion  MTA is more effective and quicker than apexification in treatment of teeth with open apices in adults.

Objective  This study was intended to design a kind of resisting part dint of device in order to preventing the base plate break while being subjected to the dint when partial base plate dint concentrates because of the increase of the magnetic attachment to the original movable artificial teeth. Methods  Ten patients who should increase magnetic attachment was adopted in the study, and we increased a kind of new designed partial cast base plate on the original base plate using laser welding technique, then designed magnetic attachment and artificial teeth. Results  None of ten sufferers appeared the phenomenon of the break of the base plate. Conclusion  The application of the laser welding technique can prevent the break of the base plate when partial dint increase because of the increase of the magnetic attachments.

Objective  To investigate the effects of skeletal Class Ⅲ malocclusion in mixed dentition on speech articulation and to look for which factors lead to the speech errors. Methods  Thirty-eight children with skeletal Angle Ⅲ malocclusion in mixed dentition were selected as a sample group and 40 children with normal occlusion in mixed dentition as a control group. Two phoneticians evaluated their articulations and wrote down error phonemes respectively. The correlation analysis was undertaken between the number of errors and the measurements of patients′ cephalometry. Results  The number of errors were correlated significantly with overbite, UI-LI, OBJ（OB+OJ） and TD-PW. Conclusion  There is articulatory malfunction in the majority of skeletal Angle Ⅲ malocclusion patients in mixed dentition. Articulatory malfunction is related to the position of incisors and the tongue.

Objective  To study the morphology of the soft palate in normal humans with digital radiography and to provide the references for therapy of the cleft. Methods  106 normal people were involved. The morphology of the soft palate was observed with digital cephalometry. Results  All static images of soft palate could be divided into six types：Shuttle-shaped, crescent-shaped, strip-shaped, S-shaped, hamulus-shaped and anomalous shaped. The dynamic image was knee-shaped. Conclusion  The morphology of the soft palate is varied.

Objective  To study 13 different cephalometric measurements of the anteroposterior jaw relationship in Angle Class Ⅱ division 1 statistically and geometrically, and to discuss the effects of various factors on this relationship, and then to choose the most adequate measurements. Methods  120 patients with skeletal malocclusion Angle Class Ⅱ division 1 were selected. The samples consisted of 60 men and 60 women between 20 to 28 years of age. Lateral cephalometric radiograph for each patient was taken in natural head posture by the same operator. A wire plumb line and suspended weight recorded the true vertical on each radiograph. The subject was then asked to determine the self-balanced position of the head. After determining the self-balanced neutral position, the subject was asked to look into his/her own eyes in the mirror. ANB angle, A-B plane angle, Wits appraisal, AF-BF distance, AXB angle, AB/SN4 distance, AB/PP distance, AXD angle, AD/SN distance, SGn/AB angle, APDI, FABA angle, beta angle and AB/HP distance were measured. Coefficient correlations among measurements were tabulated to determine which combination would produce a higher value. Fuzzy grouping analysis was made. Results  Statistically significant and highly correlated relationships was found among many measurements except Wits appraisal and SGn/AB angle. The thirteen measurements could be divided into five clusters. Conclusion  The cephalometric measurements except Wits appraisal and SGn/AB angle can be used to evaluate anteroposterior jaw relationship. The AB/SN4 distance is the most adequate measurements. ANB angle, A-B plane angle, AF-BF distance, AXB angle, AB/PP distance, APDI, FABA angle and beta angle are similar in describing anteroposterior apical base relationship in Angle Class Ⅱ division 1 patients.

Objective  To compare the color character of VITA shade guide and the custom shade guide with metal substrate. Methods  Color of 9 sites of 5 series of VITA shade guides and custom shade guides with metal substrate were measured by means of PR-650 spectrophotometer. Results  The color range of VITA shade guide were that L* was 56.86—73.86，a* was-1.29—3.69，b* was 7.09—21.94, and the transparence was 3.20—7.59. The color range of the custom shade guide was that L* was 60.59—78.54，a* was -1.09—4.99，b* was 7.60—22.35, and the transparence was 0.23—10.98. L*, a* and b* of the custom shade guide with metal substrate were higher than VITA shade guide, and the transparence was differet. The color difference of homonymy shade tab between custom shade guide and VITA shade guide was larger than 1.5 NBS. Conclusion  There is color difference between VITA shade guide and custom shade guide. Metal substrate has effects on the color of cero-metal prosthesis, and color selection in clinic should be carefully considered.

Objective  To study the root resorption caused by edgewise appliance combined with flat bite plate treatment. Methods  65 patients with edgewise technique and flat bite plate treatment were chosen. All patients were taken panoramic radiograph before flat bite plate treatment, immediately after flat bite plate treatment and 6 months after flat bite plate treatment. Root resorption grade of mandibular permanent incisors were analyzed. Results  There were statistical difference in the root resorption grade of three groups（P<0.05）, but there was no statistical difference between male and female（P>0.05）. Conclusion  Flat bite plate can cause root resorption of mandibular permanent incisors, but the root resorption is slight.

Objective  To explore the influence of chemosensitivity of Tca8113 cells by modified MTT assay after the animal model of Tca8113 were treated by the ultrasound hyperthermia. Methods  The MTT assay of the BALB/C nu/nu mice model of Tca8113 cells treated by the ultrasound hyperthermia in vivo was performed. Results  The chemosensitivity to the 9 kinds of drugs demonstrated no significant differences between the Tca8113 cells in the control group, the 39 ℃-treated group and the groups treated from 41 ℃ to 44 ℃. But significant differences between the 40 ℃-treated group and the 41 ℃ or 42 ℃-treated group existed. In the heating-time grades test, there were no significant differences in the chemosensitivity to the 9 kinds of drugs between these three pairs of group（the control group and the 15 min-treated group, the 30 min-treated and the 45 min-treated group, the 60 min-treated and the 75 min-treated group）. But there were significant differences between the 30 min-treated or the 45 min-treated group and the 60 min-treated or the 75 min-treated group. Conclusion  Ultrasound hyperthermia performed in 42 ℃ for 30—45 min can improve the chemosensitivity of Tca8113 cells to some drugs significantly, which confirms the rationality of synchronous combination of hyperthermia and chemotherapy in the chemosensitivity point of view for the first time.

Objective  To compare the shaping ability of ISO standard stainless steel K files and multi-taper ProTaper nickel-titanium files in simulated resin curved root canals. Methods  Thirty simulated resin root canals were randomly divided into three groups and prepared by stainless steel K files, hand ProTaper, rotary ProTaper, respectively. The amount of material removed from inner and outer wall and canal width after canal preparation was measured, while the canal curvature before and after canal preparation and canals aberrations were recorded.  Results  The stainless steel K files removed more material than hand ProTaper and rotary ProTaper at the outer side of apex and inner side of curvature（P<0.05）. The mean degree of straightening in stainless steel K files group was significantly bigger than in ProTaper group（P<0.05）. The canals prepared by ProTaper had no evident aberration. Conclusion  The shaping ability of ProTaper is better than stainless steel K fil

Objective  To study role of dental follicle in tooth root development. Methods  Sixteen mandibular first molar dental germs from eight five-day postnatal Balb/c mice were divided into two groups randomly. Dental follicle of germs in one group was undetached and that of another group was removed. Subsequently, each of the germs was separately transplanted to back-muscles of adult nude mice. At seventh and fourteenth day after transplanting, the germs were collected, fixed, demineralized, dehydrated, and embedded in wax in sequence. Serial sections of 5 μm thick were made following the routine methods, stained with haematoxylin-eosin dying solution, and observed under a light microscope. Results  All implantations were located in the back-muscles with abundant capillary vasculature. Under microscope, although all tooth germs could further develop after grafting, tooth germs without dental follicle developed slowly with small size and low calcification compared to those with dental follicle. Although position of Hertwig′s epithelial root sheath of all germs seemed no changing, roots of the group with dental follicle could further develop and the roots develop toward the apical direction; this tendency couldn′t be seen in the germs of another group. Inflammatory cells could be seen in and out of the pulp cavity of the two groups at 7th day after grafting, while no obvious inflammatory cell was observed at 14th day after grafting. Conclusion  Dental follicle play an important role in tooth root development. It probably can lead tooth root to develop in normal direction.

Objective  To evaluate the effect of Yishenqinghuo recipe on biological characteristic of rat bone marrow stromal cells（BMSCs） and search for the function and mechanism of this recipe in treatment of periodontitis. Methods  12- to 15-month-old SD rats were allocated into 5 groups. Group A: control group（with no periodontitis model, fed with the same dosage of saline as Group D）; Group B: model group（with periodontitis model, fed with the same dosage of saline as Group D）; Group C: high dosage group（with periodontitis model, fed with a high dosage of medicine）; Group D: middle dosage group（with periodontitis model, fed with a middle dosage of medicine）; and Group E: low dosage group（with periodontitis model, fed with a low dosage of medicine）. Ten days later, serums were collected from all the five groups for in vitro cultivation of BMSCs. Results  There was displayed a similarity in effect between the serum collected from Group C1（serum collected 0.5 h after the last gavage of Group C） and that from Group A after the last gavage, the effect being the best in terms of proliferation of BMSCs. A comparison with the other groups had revealed a striking difference（P<0.01）, with Group B having turned out to be the worst. The serum from Group C2（serum collected 1 h after the last gavage of Group C） after the last gavage could best enhance the generation and activity of ALP, having demonstrated a significant difference（P<0.01） in comparison with the other groups. Conclusion  Yishenqinghuo recipe can improve the proliferation of BMSCs and facilitate the differentiation to osteoblast.

 Objective  To obtain highly enriched osteoclasts in vitro. Methods  The bone marrow cells of 1-day, 12-day, 24-day and 36-day old Sprague-Dawley（SD） rats were separately cultured with the presence of 1,25-（OH）2D3 and dexamethasone, and the osteoclast-like cells were identified by Trap staining and scanning electron microscope observation and were purified by trypsin digestion. The count of Trap positive osteoclast-like cells was analyzed statistically. Results  The osteoclast-like cells of each group were Trap positive cells and could form the bone absorption lacunas in vitro. The amounts of osteoclast-like cells were different statistically between the groups（P<0.05） except between the groups of 1-day old and 12-day old（P>0.05）. Highly enriched  teoclast-like cells were harvested by the digestion of 0.25% trypsin and 0.02% EDTA. Conclusion  It′s indicated that a large amount of highly enriched osteoclast-like cells could be obtained through the culture of bone marrow cells of 10-day and 12-day old SD rats with 1,25-（OH）2D3 and dexamethasone and the digestion of trypsin/EDTA.

Objective  To study the role of microfilament polymerization in menchanotransduction by human perio- dontal ligament fibroblast（hPDLFs）. Methods  In tension-force group, hPDLFs were treated by tension-force values of 18% for 8 h, 16 h, 24 h. In tension-force and inhibitor group, the sample was treated with 5 μg/mL cytochalasin B before using tension-forece. Each sample was collected and the expression of cyclooxygenase-2 was measured by using immunohistoche staining. Results  In tension-force group, the expression of cyclooxygenase-2 enhanced with the extension of loading time. In tension-force and inhibitor group, cyclooxygenase-2 expression was depressed and had no relation with loading time. Conclusion  Tension-force induced cyclooxygenase-2 expression is mediated by microfilament, disruption of the microfilament polymerization will destroy mechanotransduction in hPDLFs.

Objective  To investigate the ectopic osteogenesis potential of human natural bone derived material combined with human bone marrow mesenchymal stem cells（MSCs）. Methods  Cell-scaffold complexes were implanted subcutaneously into the left back of the nude mice, and human natural bone derived material were implanted into the right back as control group. The mice were killed respectively on the postoperative 2 weeks, 4 weeks and 8 weeks. The macroscopic, histopathological, alkaline phosphatase（ALP） activity assay methods were performed to assess the ectopic osteogenesis potential. Results  The cartilaginous osteogenesis were observed in both deproteinated bone and decalcified bone，and the more new bone tissue formed gradually as the time went by after implantation. ALP activity become stronger followed with the time（P<0.05）, and compared with the decalcified bone, deproteinated bone displayed stronger ALP activity（P<0.05）. Conclusion  The MSCs and human natural bone derived material can be used as good seed cells and scaffold materials respectively to construct tissue-engineered bone, and as the scaffold material, deproteinated bone has better osteogenesis ability than decalcifed bone.

Objective  To explore the correlation between homozygous deletions and mutation of p16 gene and the carcinogenesis and progression of squamous cell carcinoma of buccal mucosa. Methods  Thirty buccal cancers, 10 leukoplakias and 8 buccal mucosas were involved. DNA was extracted from the tissues. PCR was used to analy-ses homozygous deletion of p16 gene. PCR-SSCP-DNA sequencing was performed to detect the point mutation of p16 gene. Immunohistochemical techniques were used to detect the expression of P16 protein. Results  Gene dele- tions and point mutations were not found in leukoplakia and normal buccal mucosa. Gene deletions were found in 7 samples out of 30 cases of squamous cell carcinoma of buccal mucosa（23.3%）, while point mutations were found in 5 samples out of 30 cases of squamous cell carcinoma of buccal mucosa（16.7%）. Sequencing analysis showed that 5 cases point mutations were missense mutations, occurred on exon 2. Three cases occurred in the same point, codon 99（GAT→AAT）. The result of immunohistochemical stains showed that 11 out of 12 cases gene inactivation did not expressed P16 protein. Conclusion  Homozygous deletion and point mutation of p16 were the main pattern of gene inactivation in squamous cell carcinoma of buccal mucosa. There was a closely correlation between p16 gene inactivation and the carcinogenesis of squamous cell carcinoma of buccal mucosa.

Objective  To investigate the association of root canal therapy difficulty with canal anatomic factors in Chinese mandibular permanent incisors. Methods  Two hundred and ninety nine Chinese permanent incisors were included in this study. The following anatomic items of the root canal were observed: Root canal length, number of root canal, morphology, curvature, and calcification of pulp chamber and root canal. Based on the root canal therapy evaluation criteria, the root canal therapy difficult scores were assessed. The association of root canal therapy difficulty with canal anatomic factors was analyzed with logistic regression analysis. Results  The root canal therapy difficulty grade Ⅰ, grade Ⅱ and grade Ⅲ in Chinese mandibular permanent incisors were 29.4%，20.1% and 50.5%, respectively. The root canal therapy difficulty was significantly associated with the root canal length, number, calcification, and curvature（P<0.005）. Conclusion  The root canal therapy difficulty in Chinese mandibular permanent incisor is significantly with root canal anatomy.

Objective  To analysis the homology among the extended-V region of the surface proteins in different serotype Streptococcus mutans（c, f, d, g） and to find out it′s significance in anti-caries vaccine. Methods  The DNA
of the bacteria（standarded serotype c, d, f, g and partial serotype c clinicals） was extracted and the extended-V
region（SrV+, 1 384—2 514 bp） was amplified using polymerase chain reaction（PCR）. Then the products were assessed
using restriction fragment length polymorphism（RFLP） by endonuclease DdeⅠ. The genotypings were sequenced and analysised using the program of BLAST on NCBI Gene Bank database. Results  About 1.13 kb fragments were produced both in serotype c and f, the serotype d and g were failed. The RFLP results showed that five different patterns（A, B, C, D, E） among the 117 PCR products were reveled by DdeⅠ. The ration of the genotypings A and B were the most among the strains，the C was lower，the D and E respectively was 1 and 3 strains per genotype. OMZ175（serotype f） was belong to B genotype. Selected one of the A, B, C genotypings to sequenced and blasted. Then the results of the blastn showed that the identities of the gene sequence were 92%—98% between the serotype c and serotype f, part sequence of the serotype g was homology with the SrV+ of the serotype c, the protein sequence among serotype c, d, f, g were 77%—82%. Conclusion  It is reasonable to use some putative pipetides to study the anti-caries vaccine among the extended-V regions of the surface proteins in different serotype（c, d, f, g） in S. mutans.

Objective  To study the shape, thickness and oxide percentage of major metal element of oxide film on Ni-Cr porcelain alloy after anodizing pretreatment. Methods  10 samples were made and divided into 2 groups at random. Then after surface pretreatment, the oxide films of two samples of each group were analyzed using electronic scanning microscope. The rest 3 samples were measured by X-ray photoelectron spectroscopy（XPS） and Auger electron spectroscopy（AES）. Results  Lightly selective solution appeared because the different component parts of the alloy have dissimilar electrode, whose dissolve velocity were quite unlike. The sample′s metal surface expanded, so the mechanical interlocking of porcelain and metal increased bond strength. The thickness of oxide film was 1.72 times of the control samples. The oxide percentage of major metal elements such as Cr, Ni and Mo were higher, especially Cr. It initially involved the formation of a thin oxide bound to the alloy and second, the ability of the formed oxide to saturate the porcelain, completing the chemical bond of porcelain to metal. Conclusion  The method of anodizing Ni-Cr porcelain alloy can easily control the forming of oxide film which was thin and its surface pattern was uniform. It is repeated and a good method of surface pretreatment before firing cycle.