The bracketless invisible aligner technique has been considered as a new developed orthodontic technique since its appearance during the period of late 1990s. It is characterized with the advantages of more aesthetic, comfortable, simple, high- efficient and predictable compared with current traditional orthodontic techniques depending on brackets and wires for orthodontic tooth movements. There have been many opportunities for further development and clinical application for the technique with the developments of material sciences, computer software and hardware technology, rapid prototyping techniques, et al. Nevertheless, kinds of difficulties and challenges have been and should be met either at present or in the future for this relatively new technique which just occurred around 10 years ago. The histories, developments with opportunities and challenges and prospects of the technique will be reviewed and discussed in this paper.

Objective As a new kind of reinforcing filler, ultrafine diamon（d UFD）is added into photocurable composite core materials. The properties of the materials are then measured to see if there is any improvement. Methods Different content of barium glass and UFD were added into resin matrix to fabricate six groups of photocurable composite core materials. For each group of the materials, the flexural strength, Vicker′s micro- hardness and depth of cure were measured. Data of the flexural strength and Vicker′s micro- hardness was then collected and analyzed by One-Way ANOVA. Results For the two kinds of composites with barium glass of 60% and 70%, only a small quantity of modified UFD with 0.2% weight percentage could improve the flexural strength of the composites by 34% and 21% respectively, the microhardness was improved by 23% and 30% respectively. The depth of cure of the composite core materials were more than 2 mm, which had reached the demand of the corresponding ISO criteria. The addition of UFD could make the composite core materials darker and grayer. Conclusion Micro- quantity of UFD can improve the mechanical properties of composite resins notably, and it will not affect the curability of the materials, but the defect in the color need to be reformed.

Objective The aim of this study was to investigate the in vitro effect of cell behavior on a new titanium alloy and coarsening surface with sandblasting and duplicate treated by sandblasting and acid etchin（g SLA）, including cell proliferation, morphology as well as alkaline phosphatase expression. Methods The cell derived from calvarial bone of neonate and co- cultured with the surface treated titanium alloys in vitro. The samples were treated by mechanical polishing, the sandblasting and the SLA. Cell proliferation on samples for 3 d was examined by MTT assay and cell morphology was observed by scan electron microscope. Alkaline phosphatase activity was measured at 5 d by ALP- special assay. Results The sandblasting and the SLA surface showed a significant different to smooth surface in the proliferation osteoblasts. The cells were elongated and spread well and having plentiful filopods on the coarse surface. The basal ALP activity indicated that optical density value of osteoblasts was not significant difference between coarse surface and smooth surface. Conclusion The observed effects are attributed to coarsening surface and support the concept that roughness can enhance the differentiation, good morphology and alkaline phosphatase expression of the cells. These results suggest that the good biological performance evaluation of sandblasting and etching surface is merited.

Objective To analyze the relationship between inorganic ingredien（ts Ca, P and F）concentration of plaque residues in the primary teeth and caries status，sugar exposure frequency. Methods Subjects were 93 of 3- 5 years old children living in Beijing area. According to their caries status, they were classified into two groups: Severe early childhood cari（es S- ECC）group and caries fre（e CF）group. Plaque samples were collected from subjects respectively. Ca, P and F concentration of plaque residues was measured by atomic absorption spectroscopy, spectrophotometer and fluoride electrode respectively. The information of daily sugar exposure frequency of children was obtained from a standardized questionnaire filled by their parents. The relationship between inorganic ingredients （ Ca, P and F） concentration of plaque residues and daily sugar exposure frequency was analyzed and the relationship between inorganic ingredien（ts Ca, P and F）concentration of plaque residues and caries status in the SECC group was also analyzed. Results The mean values for Ca, P and F concentration of plaque residues were lower in the S- ECC group, but the difference was not statistically significan（t P>0.05）. The daily sugar exposure frequency in the S- ECC group was higher than that in the CF group. There were no relationships between Ca, P and F concentration of plaque residues and caries stat（us dmft, dmfs）, sugar exposure frequency in the primary dentition. Conclusion Plaque residues from CF subjects did not contain a greater pool of calcium, inorganic phosphorus, and fluoride ions than that from S- ECC subjects.

Objective To investigate the effect of occlusal force on the etiology of open bite patients who suffer from temporomandibular disorde（rs TMD）. Methods One hundred and two women patients with open bite were divided into TMD（ +） group and TMD（ - ） group according to patients with or without TMD. Occlusal force, occlusal contact areas, occlusal average pressure and occlusal center were evaluated with pressure sensitive sheets. The results were analyzed by SPSS 11.0 statistic software. Results Occlusal force and occlusal contact areas in TMD（ +） group were significantly lower than that in TMD（ - ） group. Occlusal average pressure and occlusal center had no significance between two groups. Conclusion The results indicate that the decrease of occlusal force and occlusal contact areas may have some relationships with TMD in open bite patients.

Objective To investigate effect of interference therapy induced by epidermal growth factor receptor （ EGFR）- antisense cDNA in signal transduction of Hep - 2 laryngeal squamous cell carcinoma in vitro. Methods AdEasy Vector System was used to construct the recombinant adenovirus vector sense/antisense- pAdEasy- EGFR. The recombinant adenovirus vector introduced EGFR- sense/antisense cDNA fragment into HEK293 cell. The purified recombinant adenovirus sense/antisense- pAdEasy- EGFR transfected Hep- 2 cells in vitro. The inhibition of EGFR protein expression and proliferation of Hep- 2 cells, the changes of cell cycle and DNA content in Hep- 2 cells were examined by MTT, Western blot analysis, flow cytometry essay, and immunocytochemistry respectively. Results The higher titre sense and antisense mRNA expression recombinant adenovirus containing 1 032 bp EGFR- cDNA was constructed and prepared successfully. When antisense- pAdEasy- EGFR was transferred into Hep- 2 cells the inhibition of cell proliferation and EGFR protein expression in Hep- 2 cells were investigated effectively. Conclusion The antisense- pAdEasy- EGFR effectively interfere the Hep- 2 signal transduction pathway and induce apoptosis which results in inhibiting proliferation of laryngeal squamous cell carcinoma.

Objective To investigate the mechanical character, microleakage and mineralizing potential of nanohydroxyapati（te nano- HAP）- added glass ionomer ceme（nt GIC）. Methods 8% nano- HAP were incorporated into GIC as composite, and pure GIC as control. Both types of material were used to make 20 cylinders respectively in order to detect three- point flexural strength and compressive strength. Class Ⅴ cavities were prepared in 120 molars extracted for orthodontic treatment, then were filled by two kinds of material. The microleakage at the composite- dentine interface was observed with confocal laser scanning microscop（e CLSM）after stained with 1% rhodamin- B- isothiocyanate for 24 hours. Class Ⅴ cavities were prepared in the molars of 4 healthy dogs, filled with composite, and the same molars in the other side were filled with GIC as control. The teeth were extracted to observe the mineralizing property with polarimetric microscope in 8 weeks after filling. Results Three- point flexural strength and compressive of nano- HAP- added GIC were increased compared with pure GIC（ P<0.001，P<0.05）. The nanoleakages and microleakages appeared at the material- dentine interface in the two groups, but there were more microleakages in control group than in experiment grou（p P=0.004）. New crystals of hydroxyapatite were formed into a new mineralizing zone at the interface of tooth and nano- HAP- added GIC, while there was no hydroxyapatite crystals formed at the interface of tooth and pure GIC. Conclusion 8% nano- HAP- added GIC can tightly fill tooth and have mineralizing potential, and can be used as liner or filling material for prevention.

Objective The purpose of this study was to compare the quality of apical seal of the canals that obturated with differently tapered gutta- percha cone using continuous wave technique. Methods 62 extracted human mandible incisors were prepared with Gates- Glidden drill and Hero642 to a final file of No. 30 and 0.06 taper. The teeth were randomly separated into 0.02 taper grou（p 30 teeth）, 0.06 taper grou（p 30 teeth）and positive control group （ 2 teeth）. The teeth of 0.02 taper group and 0.06 taper group were respectively obturated with a 0.02, or 0.06 tapered gutta- percha cone and Cortisomol sealer using warm vertical condensation technique separately. The teeth of positive control group were not obturated. In 0.02 taper group and 0.06 taper group, 10 teeth were placed in India ink for 24 hours, 10 teeth were placed in India ink for 10 days, 10 teeth were placed in India ink for 90 hours after 67 days storage in Hank′s balanced salt solution. The teeth of positive control group were placed in India ink for 24 hours. The apical leakage was evaluated by the linear measurement under the stereomicroscope. Results The dye penetration of positive control group was along the whole canals. The apical leakage of 0.02 taper group increased along with time, while no difference was found among 0.06 taper group. There was a significant difference in the degree of leakage between 0.02 taper group and 0.06 taper group in 67 da（ys P=0.041）, but not in 24 hours and 10 days group（s P=0.601，P=0.471）. Conclusion Better apical seal was obtained when using the same tapered guttapercha cone with root canal.

Objective To evaluate the clinical application effect of a three- dimensional craniomaxillofacial measurement instrument. Methods A three- dimensional craniomaxillofacial measurement instrument was developed. Twelve patients of unilateral fracture of zygoma complex were treated with the help of the three- dimensional craniomaxillofacial measurement instrument. Results The therapeutic effects of twelve patients were satisfactory with the threedimensional craniomaxillofacial measurement instrument. No complication occurred, such as infection, injury of nerves and veins. Conclusion Three - dimensional craniomaxillofacial measurement instrument can exactly measure craniomaxillofacial hard tissue, and has adjuvant effect to restore and fix the fracture of unilateral zygoma complex.

Objective To compare the influence of propofol and isoflurane on pro- inflammatory and anti- inflammatory cytokine response to perioperative period of tongue cancer surgery. Methods Twenty- four adult patients undergone the operation of tongue cancer were assigned to two groups randomly, propofol group （ Group P） and isoflurane grou（p Group I）. In group P, anesthesia was induced with fentanyl 2- 3 μg/kg, propofol 2 mg/kg, atracurium 0.6 mg/kg and maintained with propofol 5- 8 mg·kg- 1·h- 1 and inhalation of 50% nirous oxid（e N2O∶O2=50%∶50%）. In group I, anesthesia was induced with 3%- 4% isoflurane, fentanyl 2- 3 μg/kg, diazepam 0.06- 0.1 mg/kg, atracurium 0.6 mg/kg and maintained with inhalation of 50% N2O and isofluran（e ended- tidal isoflurane was maintained at 0.6%）, in two groups atracurium was given intermittently. Blood samples were taken from peripheral vein before anesthesia （ T0）, at the end of operatio（n T1）, 24（h T2）and 48（h T3）after operation for determination of serum IL- 6 and IL - 10 concentrations. The mean arterial pressure （ MAP） and body temperature in two groups were recorded. Results IL- 6 and IL- 10 levels increased significantly in two groups at T1, T2 and T3 compared with T（0 P<0.01）. The increasing trend of IL- 6 and IL- 10 levels were similar in both groups, whereas the level of IL- 6 at T1 in propofol group was lower than that of isoflurane group significant（ly P<0.01）, however the level of IL- 10 was much higher in propofol group than that of isoflurane group at T1 and T（2 P<0.05）. Conclusion The influence of total  intravenous anesthesia of propofol on post- operation inflammatory response is much gentler than isoflurane.

Objective To evaluate the effects of headgear- activat（or HGAC）combination appliances on bone and dentition of juveniles with Class Ⅱ division 1 malocclusion using Pancherz′s analysis approach. Methods Fifteen patients( 8 males of 10- 13 years old and 7 females of 9- 12 years old, average age was 11.2 years old, ANB≥5°, overjet≥6 mm, Class Ⅱ molar relation) were treated with HGAC appliance for more than 14 hours everyday and for total of 8 - 10 months cephalograms were taken before and after the treatment. The data was analyzed with Pancherz′s analysis and pare t te（st SPSS 11.5 software) . Results After the therapy, SNA and ANB angles re - duced, the change of SNB angle was trivial, pg/OLP was forward movement. The axial inclination of the lower incisors increased and of the upper incisor reduced. Overjet of the incisors was improved, in which skeletal factor was improved to 44.64% and dentition factor was 55.36%. The first molar on the mandible was forward movement. Molar relationship was also improved, in which skeletal factor was improved to 65.65%, and dentition factor was 34.35%. Conclusion HGAC can efficaciously treat Class Ⅱ division 1 malocclusion with maxillary protrusion, stimulate modification of the mandibular condyle and fossa, and promote the development of the mandibles. Dentition was improved more than skeletal on overjet, and skeletal was improved more than dentition on molar relationship.

Objective To compare the microleakage of compomer sealant with non - rinse conditioner and resin sealant with phosphoric aci（d 35%）by dye test and scanning electron microscop（e SEM）observation. Methods 16 extracted third permanent molars were divided into 4 groups: Group Ⅰ, non- rinse condition（er NRC）+ Prime & Bond NT+ Dyract seal; Group Ⅱ, phosphoric acid（ 35%）+ Concise sealant; Group Ⅲ, phosphoric acid（ 35%）+ Dyract seal; Group Ⅳ, NRC+Prime & Bond NT+Concise sealant. The teeth were then coated with nail polish, placed in a 50% AgNO3 dye for 18 hours, and sectioned with a diamond saw. SEM observation was performed to evaluate microleakage in the teeth. Results Silver nitrate penetration was found in each group. The percentage of microleakage in group Ⅰ was higher than that in group Ⅱ, and group Ⅳ was higher than that in group Ⅱ（ P<0.01）. The percentage of microleakage of resin sealant with phosphoric acid was lower than that in compomer sealant with NRC （ P<0.01）. On SEM observation, resin tags and few gaps were found in groups with phosphoric acid. Some gaps and bubbles were found at the bottom of the fissures, particularly in the narrow fissures because of the failure of sealant penetration. Conclusion Resin sealant used with phosphoric acid was better than compomer sealant with NRC on microleakage.

Objective To study the influence of manufacture technique on the translucency and color of dental porcelain. Methods Specimens were made of VITA VMK 95 dentin porcelain and enamel porcelain and divided into 3 groups: Sintering times grou（p 1, 2, 4, 6, 8 and 10 times）, sintering temperature grou（p 910, 920, 930, 940 and 950 ℃）, sintering vacuum grou（p 95, 65, 35 and 0 kPa）. Transmittance, Y, dominant wavelength and saturation were measured by PR- 650 spectra scan spectrocolorimeter. Results Transmittance of dentin porcelain increased after 6 times repeated sintering. Transmittance of enamel porcelain increased first after the second sintering, and then became decreasing when sintering more than 2 times. Transmittance of enamel porcelain deceased when sintering temperature was lower than standard. Decrease of sintering vacuum caused the transmittance of dentin and enamel porcelain decreased. The changing of value was coordinated with transmittance. Dominant wavelength and saturation had negative correlation with sintering times and temperature, and positive correlation with vacuum. Conclusion Sintering times, temperature and vacuum all had prominent effects on the translucency and color of dental porcelain. Comparing with dentin porcelain, enamel porcelain was more sensitive with the modification of manufacture technique.

Objective Actinomyces are members of the indigenous oral microbiota which have been implicated in root caries, but their role in childhood caries initiation and progression is not well - understood. The distribution of Actinomyces in supragingival plaque on the primary teeth and the relationship between oral Actinomyces spp. and childhood caries primarily were investigated. Methods Forty children aged from three to five years old were divided into two groups. Twenty children were caries - free and twenty were caries - susceptible. Dental plaque samples from different places of the teeth were collected with sterile toothpick and polymerase chain reaction was performed with specific primers which were designed for this research. Results Actinomyces spp. were detected 100% in the cariesfree group, while 95% in the caries - susceptible group. There was no significant differences between the two groups （ P >0.05）. Actinomyces naeslundii, Actinomyces odontolyticus, Actinomyces gerencseriae, Actinomyces israelii and Actinomyces viscosus all could be detected in both groups. The prevalence of Actinomyces naeslundii, Actinomyces gerencseriae and Actinomyces odontolyticus were higher in caries- free group than those in caries- susceptible group （ P <0.05）, while the prevalence of Actinomyces israelii and Actinomyces viscosus had no significant difference between the two grou（ps P>0.05）. Conclusion Actinomyces is the main colonized bacteria in the supragingival plaque of children. The prevalence of the Actinomyces spp. may have a negative relationship with the childhood caries, and has nothing to do with different places of the teeth.

Objective To analyze the prognostic factors affecting the disease- free survival in T1/T2N0M0- staged patients with squamous cell carcinoma of tongue and compare the effectiveness of different neck treatment modalities. Methods 97 consecutive patients with early- staged squamous cell carcinoma of tongue were included in this study. The treatment and following- up records were reviewed retrospectively. Cox proportional hazard model was used to identify the statistically significant prognostic factors in the 6 potential factors. Kaplan-Meier method was used to estimate the disease - free survival and analyze the survival rate among the different levels, and log- rank method for comparison of the different distribution of the survival. A special focus was on the effectiveness of different neck treatment modalities. Results T stage, treatment methods of primary tumor, the modalities of neck treatment and cell differentiation were statistically significant prognostic factors. The value of P and relative ri（sk RR）were P<0.001, RR=4.387; P=0.04, RR=0.496; P=0.003, RR=0.504; P<0.001, RR=2.620, respectively. The difference of disease- free survival was statistically significant among the different levels under the different factors. Conclusion The disease- free survival was affected by neck treatment modalities remarkably in cN0 stage patients. Selected neck dissection together with adjuvant irradiation could decrease the recurrence risk by 49.6% according to the results of this study. TNM stage system could describe the characteristics of the patients with early- staged squamous cell carcinoma of tongue reasonably.

Objective To study the status of teeth loss and their restorations of the middle- aged and elders in Liaoning province. Methods Investigated the tooth losing and their restoration of middle- age（d 35- 44 years old）and elde（rs 65- 74 years old）according the method of the third national epidemiological investigation of oral health. The data was statistically analyzed by SPSS 11.0 software. Results Of all 1 584 the subjects, the sum of tooth loss were 6 776, mean tooth loss were 4.28. The rate of completion of dentition was 37.44%. There were 104 middle- aged and elders who happened deletion of dentition. There were 887 middle- aged and elders who happened defection of dentition. The tooth loss of maxillary and mandible was 3 550 and 3 226 respectively. The rate of prosthetic restoration was 52.77%. Conclusion The oral health status of middle- aged and elders should be taken very importance, especially those who lived in rural area. Dental caries and periodontal disease should be prevented so that to promote the status of middle- aged and elders oral health and to improve the quality of life.

Objective The purpose was to analyze the effects of three sterilization methods（ dry heat sterilization, steam sterilization, chemical sterilization） on the corrosion of dental fissure burs. Methods 100 dental fissure burs were distributed to 10 groups. One was control, the burs in the other 9 groups were treated by dry heat sterilization, steam sterilization, chemical sterilization with 5, 10, 15 cycles respectively. Weight method， scanning electron microscope, micro- hardness measurement were used to analyze the corrosion of dental fissure burs. Results The fissure burs gained their weight with cycles of sterilization. 5, 10, 15 cycles of dry heat sterilization, 10, 15 cycles of steam sterilization and 15 cycles of chemical sterilization, the weight of fissure burs were significantly increased （ P<0.05）. Scanning electron microscope showed differences on the surfaces of dental fissure burs among the three sterilization groups. After sterilization, spot or partial erosion were seen on the surface of the burs. The steam sterilization groups showed the most evident changes, followed by chemical sterilization groups and dry heat sterilization groups. X- ray energy spectrometer showed the steam sterilization groups had the largest percentage of W, followed by dry heat sterilization groups, chemical sterilization groups and control group. Fe had the opposite trends. Micro- hardness reduced after sterilization. The reduction was most clear in steam sterilization group, followed by chemical sterilization and dry heat sterilizati（on P<0.05）. The difference between 5 and 10 times of steam sterilization and 5, 10, 15 times of chemical sterilization were significant differenc（e P<0.05）. There was no significant difference between 5, 10, 15 times of dry heat sterilization （ P >0.05）. Conclusion The corrosion is most severe in steamsterilization group, followed by chemical sterilization, dry heat steriliza -tion. Dry heat sterilization shows less corrosion.

Objective To study the apoptotic effect on the squamous cell carcinoma cell line TCa83 induced by recombined adenovirus vector containing TRAIL gene and CMV promoter. Methods The TCa83 cell line was firstly infected with different titre of AdCMV- EGFP containing enhanced green fluorescence protein gen（e EGFP）as control, and investigated the transducing rate through fluorescence to obtain the definite titre. Then TCa83 cell line was infected with AdCMV- TRAIL in proper titre, and TRAIL gene was detected by means of RT- PCR. After TCa83 cell line was infected with AdCMV- TRAIL and AdCMV- EGFP at day 1, 3, 5, 7, the activity of TCa83 cell line were evaluated by MTT and the apoptosis were detected by flow cytometer. Results Proper titre was of 1 000 particles/cell, and TCa83 cell line could be infected 100% in this titre. TRAIL gene was detected by RT- PCR after infected with AdCMV- TRAIL. The activity of TCa83 decreased in both groups, but the AdCMV- TRAIL group decreased more sharply than AdCMV- EGFP grou（p P<0.001）. Both AdCMV- TRAIL and AdCMV- EGFP could lead to apoptosis of TCa83 cells, but the AdCMV- TRAIL function stronger than AdCMV- EGFP. Especially there was remarkable statistic difference between two group（s P <0.000 1）. Conclusion AdCMV- TRAIL could effectively decrease the activity of TCa83 cell line and induce apoptosis.

Objective To study c- fos and substance P expression in the central nervous system following mechanical and chemical nociceptive stimulation to the masseters in rats with occlusal interference. Methods Occlusal interference was made by bonding a 2 mm long dentin screw in the pulp cavity of the first maxillary molar in the left side. Seven days after occlusal interference, the rats in occlusal interference and mechanical stimulus group and mechanical stimulus control group were light anesthetized and nociceptive mechanical stimulus were applied to the ipsilateral masseter. Pain response was recorded and all the animals were killed 2 hours later. The rats in the other two groups were deep anesthetized and 100 μL 5% formalin was injected into the ipsilateral masseter, killed 2 hours later. The brainstem and cervical spinal cord were processed c- fos and substance P immunoreactivity and data were quantitatively analyzed. Results Both mechanical and chemical stimulus to the ipsilateral masseter induced increasing neuronal c- fos expression in the trigeminal nucleus and in the cervical spinal dorsal horn in occlusal interference and mechanical stimulus group and occlusal interference and chemical stimulus grou（p P<0.05）. Following mechanical stimulation to the ipsilateral masseter, substance P expression in the trigeminal nucleus transition zone was increased in occlusal interference and mechanical stimulus grou（p P<0.05）. Conclusion The central neuronal sensitization in the brainstem may play an important role in the masticatory muscle pain induced by occlusal interference.

Objective Three- dimensional finite method was used to analyze stress and strain distributions of periodontal ligament of abutments under dynamic loads. Methods Finite element analysis was performed on the model under dynamic loads with vertical and oblique directions. The stress and strain distributions and stress- time curves were analyzed to study the biomechanical behavior of periodontal ligament of abutments. Results The stress and strain distributions of periodontal ligament under dynamic load were same with the static load. But the maximum stress and strain decreased apparently. The rate of change was between 60%- 75%. The periodontal ligament had time- dependent mechanical behaviors. Some level of residual stress in periodontal ligament was left after one mastication period. The stress- free time under oblique load was shorter than that of vertical load. Conclusion The maximum stress and strain decrease apparently under dynamic loads. The periodontal ligament has time- dependent mechanical behaviors during one mastication. There is some level of residual stress left after one mastication period. The level of residual stress is related to the magnitude and the direction of loads. The direction of applied loads is one important factor that affected the stress distribution and accumulation and release of abutment periodontal ligament.

Objective To make a mechanical analysis on three- dimensional finite element models of the mandibular first molar with the maximum distal occlusal（ DO）structure defect after the root canal therapy and filling and crown restoration under static and impact loads and to provide a guideline for planning restoration for the clinic. Methods The research adopted reverse engineering technology to build the model of three- dimensional finite element. The form of the intercuspal occlusion and cusp to cusp occlusion during the circulation of posterior teeth occlusion movement were simulated. Half- sine pulse/impact was chosen for the impact dynamic. The impact ratio was indicated to the stress change between impact loads and static loads. Results Under the two kinds of loads, the maximum Mohr stress values of the metal crowns were shown in all models. The restoration effects between the two kinds of models were compared, the maximum Mohr stress value of the crown metal and dentin was not obviously difference. The maximum Mohr stress values of dentin were all obviously smaller than the stretch limit strength of dentin. The impact ratio closed to 1. Conclusion The impact loads accorded with the oral actual situation more than the static loads, but the suitable analysis of the static loads could be accepted. The restoration of metal crown is necessary. The effects between the amalgam filling and full crown restoration and composite resin filling and full crown restoration is not difference obviously.

Objective To observe the morphology and proliferation of epithelial cell rests of Malasse（z ECRM） during tooth emergence and occlusal function, and to evaluate its roles. Methods Cytokeratin 14 （ CK14） was applied as special marker of ECRM cells. The morphology and distribution of ECRM were examined by light and transmission electron microscopy. PV two- step immunohistochemical method was used to detect the expression of CK14 and proliferating cell nuclear antige（n PCNA）in ECRM. Results ECRM experienced instinct morphological changes during tooth emergence and occlusal function. They were observed as network of epithelial cells labeled by CK14, especially in furcation level regions of mouse molars and active cell proliferation during occlusion found period. Cell apoptosis was observed in many ECRM by transmission electron microscopy during late stage of the progess. Conclusion ECRM may not only an accidental left- over of early embryonic development but rather play significant roles in occlusion found period.

Objective To investigate the effects of different static compressive stress on the biological characteristics of the mandibular condylar chondrocyt（es MCC）. Methods The static compressive stress with a magnitude of 12, 24, 36 kPa were exerted on the third passage of MCC for one hour. The MCC was dyed by immunohisto- chemical method. The changes of the expression of collagen type Ⅰ , Ⅱ , Ⅲ and proteoglycan （ PG） were evaluated by a pathologic portraits analytic system. Results The static compressive stress with a magnitude from 12 to 24 kPa can enforce the expression of collagen type Ⅰ, Ⅱ, Ⅲ and PG of MCC. However, the decrease of expression of collagen type Ⅰ and PG of MCC was detected when exerted by the static compressive stress with a magnitude from 24 kPa to 36 kPa. Conclusion The static stress of proper magnitude can make MCC more differentiate. However, the static stress of over- magnitude may make the biological characteristics of MCC weaken and express some characteristics of dedifferentiation.

Objective To evaluate the effects of grooved, alkali- and heat- treated, acid- etched and TiO2 blasted surfaces of titanium substrates on F- actin cytoskeleton of osteoblasts in vitro. Methods Osteoblasts derived from fetal rat calvarial were cultured on 6 different commercially pure titanium discs- groove（d G）, sandblaste（d SB）, sandblasted and acid- etchin（g SLA）surfaces and alkali- and heat- treate（d AH1, AH2, AH3）surfaces. For F- actin cytoskeleton measurement, osteoblasts whose filamentous actin was stained with phalloidin- TRITC were cultured for 1, 2, 4, 12 h, evaluated by CLSM observation. Results Osteoblasts attached to the different types of surfaces after 1 hour culture were similar. The actin cytoskeleton formed a ring of cortical filaments around the nucleus after 1 hour on SB, AH2, AH3, SLA surfaces. Actin filaments condensed along edges of pits. The actin filaments of seeded cells were spread after 2 h. The actin filaments on G formed bundles around the nucleus. The filaments began to parallel to the grooves. On AH1, the fibres formed a ring of cortical filaments around the nucleus with some cytoplasmic fibres radially oriented. On AH2, AH3, SB, the fibres orignised in a cytoplasmic meshwork with fibres which terminate at the ridge of depressions. The cell were suspending itself over the depressed areas. Actin filaments on SB were distinct and well formed that were oriented paralled to one another and the long axis of cells. After 4 h, actin filaments appeared organised in a parallel to one another and the long axis of cells. After 12 h, the actin filaments on all surfaces were well spread and were oriented paralled to another and to the long axis of the cell. The filaments  formed bundles which reached to holes or adhered to the ridge of raised points, suspending cells over depressed areas. Conclusion After 12 h, the actin filaments on all surfaces were well spread and were oriented paralled to another and to the long axis of the cell. It was concluded that F- actin cytoskeleton of osteoblasts were spread best on SB surfaces among all surfaces.

Objective To observe the effects of 17β- estradiol on the intracellular calcium of masticatory muscles myoblast. Methods Myoblasts from maxillofacial skeletal muscle of one week old female Sprague- Dawley rats were cultured. Fluo- 4- AM as the Ca2+ indicator and the laser confocal microscope system were used to observe the effects of estrogen on the cytoplasmic Ca2 + concentration in the normal pH condition and the acid condition （ pH= 6.7）. Results In the normal pH condition, when 17β- estradi（ol 10- 9, 10- 8, 10- 7 mol/L）were added to cells cytoplasmic Ca2+ immediately increased then decreased right away, and in the end came into a new Ca2+ homeostasis in the base line. In the acid condition, 17β- estradio（l 10 - 9, 10 - 8, 10 - 7 mol/L） made the cytoplasmic Ca2 + decreased immediately then came into a new Ca2 + homeostasis under the base line. Conclusion The results suggest that estrogen may maintain the skeletal cytoplasmic Ca2+ concentration in a lower level and reduce the cytoplasmic Ca2+ accumulation to keep the normal functions of masticatory muscles myoblast.

The structural theory and fabrication of a self- designed rotating auxiliary spring in edgewise technique were described. Rotating auxiliary spring was applied to correct rotated tooth in clinic. It indicated that rotating auxiliary spring was an easy- fabricated, convenient- manipulated device, and could produce an effective treatment results in correcting rotated tooth, especially in the final adjustment stage.

Papillon- Lefèvre syndrom（e PLS）is an extremely rare inherited disease as an autosomal recessive trait. The disorder is characterized by diffuse palmoplantar keratoderma and premature loss of both deciduous and permanent teeth. This paper described a case of PLS with classic clinical features and briefly reviewed the relevant literature.