Objective:To examine the effects of chronic intermittent hypoxia(CIH)on the NF-κB,IL-6 and PGE2 level in rats with periodontitis.Methods:32 male SD rats(6 weeks old)were randomly divided into 4 groups(n =8),group A(normoxic control),B (normoxic periodontitis),C(CIH)and D(periodontitis +CIH).Periodontitis model was established in the upper second molars by liga-tion technique and high-glucose diet in the rats of group B and D.The rats in the group C and D were subjected to CIH in a cycle of al-ternative nitrogen and oxygen in a closed chamber.The chamber was filled with nadir and zenith ambient oxygen every 1 20 seconds per cycle for 8 hours per day.The rats were sacrificed and the gingival tissues were examined for the detection of IL-6 and PGE2 expression by ELISA,and NF-κB expression by immunohistochemistry.Results:Histology revealed apical migration of junctional epithetlium and crestal alveolar bone resorption in group B and D,and in the above phenomena of group D was the severest.The content of NF-κB,IL-6 and PGE2 in group B,C,D was higher than that in group A(P <0.05),and in group D was the highest(P <0.05).Conclusion:Chro-nic intermittent hypoxia can aggravate the inflammation of periodontitis.

Objective:To evaluate the translucency,opalescence and fluorescence reflection of 6 light-cured resin composites. Methods:Disks of 6 resin composites including Filtek Supreme XT-YT(XT),Filtek Supreme XT-A3B(3M),Clearfil Majesty-A3 (MJ),Gradia Direct-A3(GC),Venus-A3(VE)and Charisma Diamond-A3(CA)were prepared in the diameter of 9 mm with the thickness 2.0 mm.PR-650 spectral scanning colorimeter was used to measure and caculate translucency parameters(TP),opal-escence parameter(OP)and fluorescence reflection(FL)and to draw the fluorescence reflection curves.Results:Except XT and MJ,TP value of other resin composites were in the range of natural tooth.Only OP value of XT was in the range of natural tooth en-amel.FL value of XT was close to that of natural tooth dentin.Fluorescent peak wavelength of GC,MJ,VE and CA were in the range of natural tooth,but fluorescent peak height was higher than that of natual tooth.TP was positively correlated with OP(r =0.85,P <0.05).There was no statistic correlation between TP and FL,between OP and FL.Conclusion:The 6 resin composites can simulate optical property of natual tooth,but the opalescence of resin composites is defective.

Objective:To observe the temperature vaxiation in the pulp chamber during Nd-YAG laser irradiation at tooth cervical portion.Methods:60 extracted permanent teeth were divided into 3 groups (anterior teeth,premolars and molars,n =20).The teeth in each group were further divided into 4 subgroups according to the laser power setting (0.4 W,0.8 W)and interval time(1 0 s,20 s)(n =5).After canal preparation the teeth were fixed and filmed using the parallel projection technique.the thickness of the buccal pulp chamber wall was measured by graphic analyzing software.The buccal cervical portion of the teeth was irradiated through 200 μm optical fiber,Temperature in the pulp was measured by K type thermo-electric couples fixed to the pulp chamber wall.Re-sults:The temperature inside the chamber increased with the higher power setting(P <0.01 ),under the same power setting,longer irradiation duration caused higher temperature rise(P <0.01 ).Greater chamber wall thickness was associated with lower temperature rise.Conclusion:The temperature rise in the pulp chamber during laser irradiation is correlated with laser power setting and the thickness of the irradiated tooth tissue.

Objective:To investigate the effect of microgroove surfaces of titanium on the adhesion and cell cycle progression of human gingival fibroblasts(HGFs).Methods:Microgroove titanium surfaces were fabricated on silicon plate by photolithography with parallel grooves:1 5,30 and 60 μm in width and 5 μm and 1 0 μm in depth,the groups were denoted as T1 5 /5,T1 5 /1 0,T30 /5,T30 /1 0, T60 /5 and T60 /1 0,respectively.Smooth titanium surfaces (T0)were used as the controls.Surface topography were observed by ES-EM.HGFs were cultured on the microgroove surfaces.Morphology of “contact guidance”was observed by immunofluorescence tech-nique.Cell cycle distribution was analyzed by Flow cytometry.Results:HGFs on the microgroove surfaces had “contact guidance”par-allel to the microgrooves,whereas the cells on T0 were oriented randomly.T60 /1 0 group had the highest percentage of S phase cells, followed by T30 group and T1 5 group,but still higher than that in the control group.In groups with higher groove width (T60 group and T30 group),the increase of groove depth benefited the increase of S phase percentage,while in T1 5 group,the increase of groove width decreased the S phase percentage.Conclusion:Surfaces of microgrooves with different dimensions achieved “contact guidance”for the cultured HGFs.The surfaces with increasing groove width and depth benefit the cell cycle progression.

Objective:To investigate the effects of 5-aza-2′deoxycytidine(5-aza-dC),a DNA methyltransferase (DNMT)inhibitor, on the methylation status of the RECK gene and the invasion of salivary adenoid cystic carcinoma cell lines.Methods:Methylation-specific PCR,Western blot analysis and quantitative real-time PCR were used to investigate the methylation status of RECK gene and the expression of RECK mRNA and protein in SACC cell lines.The invasive ability of SACC cells was examined by transwell assay. Results:Promoter methylation was only found in ACC-Mcell line and not in ACC-2 cell line.Treatment of ACC-Mcells with 5-aza-dC partially reversed the hypermethylation status of the RECK gene and significantly enhanced the expression level of mRNA and pro-tein of RECK,suppressed ACC-Mcell invasive ability.Conclusion:5-aza-dC can inhibit ACC-Mcell invasion by reversal of hyperm-ethylation status of RECK gene.

Objective:To study the effects of dental fluorosis on the tooth movement following extraction of adjacent tooth in adoles-cents for orthodontic treatment.Methods:50 adolescents were divided into mild(n =1 3),moderat(n =1 0),severe(n =7)and healthy control(n =20)groups according to the fluorosis severity using Dean's index.4 4 were extracted and appliance was applied. X-ray image was taken 1 week and 1 ,2 and 3 months after appliace activation.Tooth movement was measured cephalometrically by Auto CAD.Results:Tooth moving distance was more(P <0.01 )and the alveolar bone resorption area was smaller in fluorosis group than those in healthy control group(P <0.01 )1 ,2 and 3 months after appliance activation.The moving distance was negativelly relat-ed with bone remodling area(P <0.05).Conclusion:Adolescent dental flurosis play an important role in bone remdodeling in extra-tion sites and tooth movement during orthodontic treatment.

Objective:To evaluate the bond strength of root canal sealer AH Plus and GuttaFlow to root canal walls after final rinse with 4 different final irrigation regimens.Methods:60 teeth with single-canal were prepared chemomechanically using 5.25% sodi-um hypochlorite (NaOCl)as root canal irrigant.The teeth were then randomly distributed into 3 groups(n =20)according to the final irrigation protocol:1 7% EDTA followed by 2% chlorhexidine(CHX)(group 1 ),5.25% NaOCl followed by 1 7% EDTA(group 2), 0.9% normal saline(NS)(group 3).The root canals were then filled with sealers using a lentulo spiral and each group was distribu-ted into 2 subgroups according to the sealers(n =1 0):a.AH Plus;b.GuttaFlow.The roots were transversally sectioned to obtain 2mm thick dentinal slices.Then a push-out bond strength test was carried out and failure mode was observed by stereomicroscope. Results:The bond strength of AH Plus was significantly higher than that of GuttaFlow(P <0.05)regardless of the final irrigation reg-imens.When the root canals were filled with AH Plus,the push-out bond strength of group 1 (5.37 ±2.80)MPa was significantly lower than group 2(8.81 ±4.38)MPa and group 3(9.07 ±2.77)MPa(between group 1 and 2 or 3,P <0.05;between group 2 and 3,P >0.05).When the root canals were filled with GuttaFlow,the push-out strength of group 1 ,2 and 3 was (1 .40 ±0.59)MPa, (1 .26 ±0.62)MPa and (1 .05 ±0.27)MPa respectively(P >0.05).The failure modes of AH Plus and GuttaFlow were both mainly mixed,but the proportion of adhesive failure in the canals filled with GuttaFlow were obviously higher than AH Plus.Conclusion:The bond strength to root canal wall of GuttaFlow is significantly lower than that of AH Plus.1 7% EDTA followed by 2% CHX as fi-nal irrigant can reduce the bond strength of AH Plus but has no marked effect on GuttaFlow.

Objective:To explore the stress change rule of craniofacial bone suture and the interface of bone-implant against differ-ent strength and direction of protraction on the implant anchorage in alveolar bone.Methods:The original DICOMdata of 2-D image of craniofacial complex were obtained by high resolution CT scanning.3-D finite element models of craniofacial complex were devel-oped according to the DICOMdata.Forces of 1 -1 0 N inclined at 0 -60°to Frankfort horizontal plane in the anterior and inferior di-rections were respectively applied on the implant anchorage in the alveolar bone at 32 23 .Data of principle stress and Von Mises Stress of each mode of each simulaton was caculated.Results:The change rule of the effectiveness of different force value of protrac-tion in the same direction was the same in different stress zone;that of the same force value of the protraction in differente direction differed in different stress zone.When the protraction angle was less than 30°,the maxillary complex will spin up.In the 30°,the maxillary complex showed the forward growth.Between 40°-50°,the growth direction was the same with the protraction direction. When the protraction angle was more than 50°,the maxillary complex showed down spin.Conclusion:Protraction force of 1 -1 0 N at 30°-50°to Frankfort horizontal plane on implant anchorage in the alveolar bone at 32 23 can induce maxillary complex grow for-ward.

Objective:To study the prosthodontic design for the treatment of maxillary first molar mesio-lingual cusp defect with subfis-sue.Methods:A finite element model of maxillary first model,including mesio-lingual cusp defect with subfissue,periodontal support-ing tissue and a section of the maxilla was established by cone beam CT.Different prosthodontic designs for respective restoration and simulating different bite force were adopted,the Von Mises stress,maximum compressive stress and the crack distribution,J integral and the root displacement were analysed.Results:In the metal pile restoration model,the stress,JINT value and the equivalent stress and displacement of root were the smallest.With the increase of crack depth of the vertical and oblique fissue,the equivalent levels of stress (equivalent stress of J integral),the stress experienced by the dentin along with the peak of the maximum principal,increased signifi-cantly.Under 4 kinds of force direction and 3 repair methods,the equivalent stress peak value,J integral dentin stress,maximum prin-cipal stress peak value and dentin stress peak value of the cracks was 200 N,90°>200 N,45°>600 N,0°>200 N.Conclusion:High elastic modulus and all ceramic crown may lead to minimal equivalent stress,J integral,dentin equivalent stress and maximum principal stress.When subfissure is repaired,teeth fracture remains possible and any possible propagation may exist.The effect of later-al force on the crack and the dentin is greater than that of vertical force for crack expansion and tooth fracture.

40 cases(control group)with aggressive periodontitis (AgP)received scaling and root planning (SRP)and 38 cases(test group)received SRP followed by oral administration of amoxicillin plus metronidazole for 7 d.Gingival crevicular fluid samples were exam-ined for the levels of MMP-1,MMP-8 and tissue TIMP-1 by ELISA before therapy,3 and 6 months after therapy,TIMP-1 /MMP-1 and TIMP-1 /MMP-8 ratios were calculated.The levels of MMP-1 and MMP-8 were decreased in both groups (P <0.05)at 3 and 6 months after therapy.TIMP-1 /MMP-1 and TIMP-1 /MMP-8 ratios were increased in the 2 groups(P <0.05)after treatment,3 months after therapy the ratio in test group was higher than that in control group(P <0.05).