Objective　To observe the effectiveness of prevention and cure for maxillary growth deformity following tissue engineered oral mucosa implantation on mucoperiosteal denuded palate process in young rat.Methods　Hard palate mucoperios- teum of a SD baby ratwere excised and oral keratinocyteswere isolated and cultured. Tissue engineered oral mucosawas fabricated with the cultured oral keratinocytes and the membrane made of sodium alginate (SA). 80 female three-week-old SD ratswere used as subjects in this study. The animals were divided randomly into a normal control group and 3 experimental groups, each group included 20 rats. Normal control group (NG) were not operated. Hard palate mucoperiosteum on left side in all experimental groups were excised, exposed bonewere nottreated in denuded group (DG), but repairedwithmembrane inmaterial group (MG) and repaired with the tissue engineered oral mucosa in mucosal group (MUG). All the animalswere sacrificed at 9thweek postop- eratively (12 weeks old), and the clean widths of right and left hard palatal were measured under a dissection microscope. The difference between palatal widths of two sides and the asymmetry ratio between the different groups were compared and analyzed. Results　No significant difference in asymmetrywas discovered between the DG and theMG, butthe asymmetry inMUGwas less than DG orMG.Conclusion　Tissue engineered oral mucosal implantation in palatoplasty is an effective method in preventing and curing secondary maxilla deformity by repairing denuded bone wound.

Objective　The purpose of the study is to investigate the mechanism of immune escape and the expression of Fas and Fas L in oral premalignant lesions (OPLs) and oral squamous cell carcinomas (OSCCs).Methods　64 samples, includ- ing normal oral mucosa(7), hyperkeratosis(9), premalignant lesions(24) and squamous cell carcinomas(24), were studied. The cells in the test specimens, which demonstrate granular staining, were considered as positive. The expression of Fas and FasLwas evaluated semi-quantitatively as follows: -,no expression; +(mild),<5% positive cells; ++(moderate),6%~25% positive cells; +++(intense),26%~50% positive cells; or ++++(very intense),>50% positive cells.Results　In the process of oral carcinogenesis, each stage had Fas expression. The positive staining appeared essentially on cell membrane. Various degrees of Fas expressionwere seen in the diseased tissues. The number of positively stained cells in the moderately and severely dysplastic tissues appeared higher than that in the normal control (P<0·05). In the OSCC group, the level of expression of Fas antigen de- creased significantly by comparison with the normal controls (P<0·05). Fas L expression was discovered in each stage of the process of oral carcinogenesis. The positive staining appeared in cytoplasm. In hyperkeratotic tissues and OPLs, the number of Fas L expression cellswas significantly higherthan that in the normal controls. The number of Fas L expression cells of OSCCs in- creased by comparisonwith both normal controls and OPLs.Conclusion　The results indicate that the expression of Fas and Fas L is involved in oral carcinogenesis and this may be directly related to the mechanism by which the cancer cells evade the host im- mune assault. Perhaps, Fas/FasLsystemmay be used as a prognostic biomarker in predictingthe behavior of oral premalignant le- sions in the near future.

Objective　To study the regulation and effect of the expression of nm23-H1 gene in different processes of re- gional lymph node metastases of oral squamous cell carcinomas(OSCC).Methods　By immunohistochemical analysis in 200 paraf- fin-embedded tissues of OSCC and Western Blot in 9 fresh tissues of OSCC using a monoclonal antibody, the expression of nm23-H1/NDPK-Awere detected in dividing groups accompanied with the clinical and pathological data of cervical lymph node metastases and modes of invasion.Results　The rates of negative expression of nm23-H1/NDPK-A had significant differences be- tween metastatic cases(34/81) and non-metastatic cases(15/119). The nm23-H1/NDPK-A negative group showed higher frequen- cy of lymph node metasteses (P<0.01). In the different metastatic processes, There were significantly differential expressions of nm23-H1/NDPK-A among stage N0,N1 and N2(P<0.01), distinct involved quantities of lymph nodes (P<0.01), dissimilar metastatic involved levels(P<0.05) , definite modes of invasion(P<0.01) and different cell differentiations(P<0.01). There were much higher negative expressions in those cases of N1 stage(23/38), only one lymph node to be involved(23/39), metastas- ized to submandibular nodes or/and superior deep cervical nodes(17/28 and 12/29, respectively),Ⅳc types of invasion(33/54) and poor differentiations(9/19).Conclusion　The results indicated that nm23-H1/NDPK-A played an more important role in switching the initial metastases formation than in influencing the later metastases spread because the negative expressions of nm23-H1/NDPK-A in solid tumors of OSCCwould induce the formation of highmetastatic cellular subpopulations. Itwas also con- firmed that nm23-H1 gene might be a metastatic suppressor and may be useful in predicting the initial lymph node metastases in OSCC.

Objective　The aim of this studywas to analyse the stress distribution in the periodontium of the maxillary first molar and to search optimal loads patternwhen distal movementto provide biomechanical basis forthe clinical practice.Methods　 By spiral CT scanning, a three-dimensional finite element model of the maxillary first molarwas established, and then four differ- ent load patterns were added to the molar to obtain the optimal load partern for molar bodily distal movement.Results　Different loads lead to different stress distributions when distal movement.Conclusion　A distalizing force combined with a countertipping moment (Mt/F=10) and a counterrotationmoment(Mr/F=6) can lead to a lower and uniform stress on the distal side of the peri- odontal ligament,it implys a tendency of translation of the maxillary first molar.

Objective　The purpose of this study is to construct plant expression plasmid containing the gene encoding chimera SBR-CTΔA1.Methods　The target gene fragment P2, including the gene-encoded chimera SBR-CTΔA1(3 498~5 378 bp), was obtained by standard PCR amplification. The PCR products were ligated with pGEM-easy vector through TA clone to form plasmid pTSC. The plasmid pTSC and plasmid pPOKII were digested by restricted endonucleaseBamHI andKpnI, and the digested products were extracted and purified for recombination. Then the purified P2 and plasmid pPOKII were recombined byT4 DNA ligase to form recombinant plasmid pROSC; insertingbargene into the plasmid and form pROSB plasmid. The recombined plasmids were isolated and identified by restricted endonuclease cutting and Sanger dideoxy DNA sequencing.Results　P2 gene was linked to pPOKII plasmid and formed recombinant plasmid pROSC. The DNA sequence and orientation were corrected. And bargene was inserted into pPOSC and form recombinant plasmid pROSB.Conclusion　Plant expression vector pROSC and pROSB containing the gene encoding chimera SBR-CTΔA1, which may provide useful experiment foundation for further study on edible vaccine against caries have been successfully constructed.

Objective　To studytelomerase activity and expression of oncogenes c-mycand p53 in tongue cancer, analyse the interaction among them, and assess their possible correlations with tongue cancer clinicopathological features.Methods　To detective the telomerase activity by TRAP and examine the positive expression of c-mycand p53 in tongue cancer by hybridization in situ.Results　A high telomerase activity existed in lower differentiated tongue cancer (P<0·05); the positive expression of c-mycincreased significantly in lowergrade tongue cancer (P<0·05) and the positive expression of p53 decreased increasingly in tongue cancer accompanied with lymph node metastasis (P<0·05).Conclusion　Telomerase may play a key role in the tumori- genesis of tongue cancer. Meantime, c-mycand p53 exerts important effect on telomerase activation during the course of tongue cancer generation and development.

Objective　In order to investigate the effect of PABA produced byStreptococcus sanguison microecological balance of subgingival plaque, different concentrations of PABAwere applied to see if it can influence the form and adherence of P.gingivalis.Methods　After adding different concentrations of PABA into 1/2 concentration of BHI media, an anaerobic tech- nique was used to cultureP.gingivalis.P.gingivalisgrew in the medium was observed by a scanning electron microscope.Re- sults　Excessively high or low PABA concentration could influence the form and adherence ofP.gingivalis.Conclusion　PA- BA produced byStreptococcus sanguiscan affect the form and adherence ofP.gingivalis.It indicates thatStreptococcus sanguis plays regulative effect on the microecological balance of subgingival plaques.

Objective　To investigate more deeply the function and mechanism of DSPP during tooth development.Meth- ods　Explants of tooth germs from embryonic 17 th day mice were divided into two groups. In the control experiment, explants were cultured in agarose semi-solid medium under serum-free and chemically defined conditions, while explants in the other group were cultured with 30μmol/L, 15 bp antisense oligodeoxynucleotide targeted to DSPP mRNA. After 10 ds, the explants were ex- amined by transmission electron microscope. The width of dentin matrix at the tip of the cuspswere then measured and statistically analyzedwith Studentt-test.Results　Ultrastructure analyses showed that large cisternae of the rough endoplasmic reticulum (RER) existed in the odontoblasts at the tip of the cusps of antisense-treated explants and the average thickness of dentin matrix (2.5μm) was thinner compared to the control ones (3μm,P<0.001). In addition, the collagen fibers in extracellular matrix were disorganized.Conclusion　These findings indicated that DSPP played an important role in keepingtooth normal development, as well as in dentin mineralization by maintaining odontoblasts′secreting ability and controlling fiber structure and orientation.

Objective　The purpose of this study was to compare the compressive strength of phosphate-bonded invest- ments.Methods　The three sorts of investmentswere mixed accordingtomanufacturer′s recommendation before poured in the mol- ds. After heated up to 900℃, every sample was mounted on a universal experimental machine to test its compressive strength in ambient.Results　Significant differences were found between the four groups(P<0·01).Conclusion　From the data above it is concluded that the compressive strength of X-20 Chrome Investment mixed with the special liquid was the highest.

Objective　To observe the prevalence ofPorphyromonas gingivalis(Pg),Treponema denticola(Td) andBac- teridesforsythus(Bf) subgingivally in diseased sites of chronic periodontitis (CP) patients.Methods　Samples of subgingival plaque were detected by 3 kinds of oligonucleotide DNA probe from 60 sites of CP patients and 10 healthy sites of 10 healthy peo- ple.Results　The positive rates ofPg,BfandTdin patients were 91·67%, 90·00% and 95·67% respectively;Pg,Bfand Tdwere detected simultaneously in 83·33% patients andPg,BfandTdwere found to be related with each other(P<0·01). Conclusion　Pg,BfandTdwere prominent periodontopathic bacteria and related each other, might exist in complexes in sub- gingival plaque and coaggretate together.

Objective　The purpose of this studywas to evaluate the role of Angle′s class, overall ratio and anterior ratio in the creation of tooth size discrepancies, and to determine whether any tooth extraction combinations create more severe discrep- ancies.Methods　166 dental casts of orthodontic patients were selected randomly. These models were classified according to an- gle′s criterion. Mesio-distal dimensions of mandibular and maxillary teeth were measured before treatment, and subjected to Bolt- on′s analysis. Hypothetical tooth extraction by the following combinations: all the first premolars, all the second premolars, upper first and lower second premolars, and upper second and lower first premolars, was performed on each patient. The measurement results were again subjected to Bolton′s analysis to seewhether anytooth-size discrepancy had been created. The resultswere eval- uated statistically by means of Logistic regression model.Results　Overall ratio, anterior ratio and extraction models affected me- sio-distal tooth size ratio of both maxillary and mandibular teeth in the final stage of orthodontic treatment, Whereas, the results showed no significant difference among these groups of malocclusion.Conclusion　The results suggested that dentists should al- ways keep in mind that each patient should be treated individually and should be aware of that other factors also played important roles in determiningwhat teeth, if any, should be removed and the Bolton analyses of all kinds of extraction models should be car- ried out, as well as the general Bolton analysis.

Objective　This study was to observe and compare the microbiological effects of laser therapy combined with ultrasonic subgingival scaling and root planning (SRP) versus SRP alone.Methods　26 contra lateral teeth were randomly as- signed to the test group (laser+SRP) or the control group (SRP alone). Subgingival microbial samples were collected,cultured and analyzed at baseline, then repeated immediately after laser treatment atweek 1,week 2 and week 4.Results　Although both groups had significant increase in G+/G-ratio (P<0.01), the changes of G+and G-were more obvious in the test group till week 1(P<0.05). The total CFUof test group diminished significantly just after laser irradiation (P<0.05). That revealed the laser therapy followed by SRP appeared to have a stronger effect on converting the subgingival micro-ecosystem to healthy status. Conclusion　Laser appeared to have a stronger bactericidal actionin vivo,especially on the dark-pigmented G-rods associated with periodontal disease.

Objective　To evaluate the inhibitory effects of topical application of specific immunoglobulin yolk antibodies (IgY) tomutans streptococcion composition of human dental plaque.Methods　Atotal of 24 healthy adult volunteerswere select- ed and randomly distributed into three experimental groups. After a supragingival scaling, the subjects were treated with an appli- cation of IgY containing spray (test group,n=9), a 0.15% chlorhexidine(CH) spray(positive control group,n=9) or a placebo phosphate buffered saline(PBS) spray without any active ingredients(negative control group,n=6) three times daily for three weeks. Pooled plaque samples from the smooth surfaces of teeth were collected for microbiologic analysis before administration (baseline,day 0)、during treatment(days 7、14 and 21)and after withdrawal of the agents(days 28、42 and 56)and plaque index were recorded.Microbial cultivation were performed by serially diluting the samples with PBS solution and cultivating the aliquots on mitis salivarius agar(MS) andMS supplemented with bacitracin (MSB) fororal streptococciandmutans streptococcirespective- ly. The number of colony-forming unit (CFU) per plate was counted and the percentage ofmutans streptococciperoral streptococci in dental plaque were determined. The effect of IgY on colonization ofmutans streptococciwere analyzed by an analysis of variance (ANOVA).Results　The plaque indexes remained unchanged,butmutans streptococciin dental plaque was suppressed signifi- cantly following a shortterm(threeweeks) application of IgY, and lowlevel ofmutans streptococcipersisted for at least 5 weeks af- terwithdrawal of IgY.Conclusion　The results suggest that the immunization with specific immunoglobulin yolk againstmutans streptococcicould be useful for long term suppression ofmutans streptococcicolonization in human dental plaque.

Objective　To investigate the regularity of cervical lymph-node metastasis in oral squamous cell carcinoma pa- tients and determine the treatment principle to cN0patients.Methods　1 024 oral squamous cell carcinoma cases who underwent neck dissection between 1980~2001 were investigated retrospectively.Results　The total rate of cervical lymph-node metastasis of oral squamous cell carcinoma was 36·62%(375/1 024), the metastasis rate of cancer in tongue, buccal, gingival, and floor of mouth was 42·82%, 31·93%, 32·76%, and 25.00%, respectively; the rate of occult metastasis was 20·94%(71/339), the incidence of occult metastasis was closely related to the location of primary lesion and T stage.Conclusion　The results in this study revealed that the therapy regime of the oral squamous cell carcinoma should be based on carefully clinical examination and compositive analysis on primary lesion related to size, location and cervical lymph-node.

Objective　The aim of this article was to discover the corrosion resistance of magnetic attachments, which were encapsulated in stainless steel, when pHvalue of artificial saliva was lower than normal.Methods　Three kinds of magnetic retainers were exposed for 6 months to artificial saliva with pH ranging from 5·6 to 7·0, thermostated at 36·5℃. This study in- cluded electrochemical test as polarization curves, chemical test as immersion test and SEMto analyze the corrosion behavior of the materials.Results　Fe3+ions in stainless steel released more than ten times in an environment pH5·6 than pH7·0. The higher concentration of H+, the more elemental release. That pH value of artificial saliva reduced may affect the corrosion speed. The magnetic retainers were not resistant to acidic environments during exposure.Conclusion　Transient exposure of stainless steel to an acidic oral environment can increase elemental release significantly. So acid resistance of magnetic retainers was relatively weak, and it would affect the life span of magnets.

Objective　To evaluate theNidus vespae′scario-static effect on biofilmmodelin vitro.Methods　Afour-or- ganism bacterial consortiumwas grown in a biofilmmodel on hydroxyapatite (HA) discs in a continuous culture system and exposed to repeated solution pulsing respectively. Therewere three parallel-connected flow cells in the model, sowere the three groupswith different solution pulsed in. Negative control group was pulsed with distilled water, positve control group was pulsed with 250 mmol/L sucrose solution aswell. While 4·0 g/LNidus vespaetogetherwith 250 mmol/L sucrose solutionwas pulsed in the experi- ment group. During the experiment, the pH responses against the pulses were recorded. After the 6 pulses, the biofilm surface structure was observed with a scan electron microscope and the population on the biofilmwas enumerated.Results　Nidus vespae can significantly inhibit the adherence ofStreptococcus mutanstoHA discs compared with the control group of 250 mmol/L sucrose pulsed in, and can facilitate the remove of acid products. It is also found that the extra-cellular polysaccharide is reducedwith the pulsing ofNidus vespae.Conclusion　Nidus vespaein the biofilm model can partially decrease the cariogenic response of sucrose solution pulsed in.

Objective　To investigate the influence of bone remodeling in extraction sites and orthodontic forces on tooth movement with the aim of providing a basis for selecting optimal orthodontic forces, time of tooth movement and reducing the time for tooth moving into extraction sites.Methods　Extraction of upper first molars were performed on 36 male Sprague-Dawley rats whichwere divided equally into 3 groups. A method for quantification of orthodontic tooth movement in the rats was presented. Orthodontic appliance was placed at different time after tooth extraction. Different forces were used to move the maxillary second molars mesially into the extraction spaces. X-ray was taken before appliance activation and after 1, 3, 5, 7, 10, 14 days since appliance activation. Tooth movementwas measured cephalometrically by Imagine AnalysisTechnique, adjusting for magnification by using the known digitized length of the broach.Results　①The tooth on the recent extraction side moved fasterthan that on the healed side.②Tooth movement at all time points on the 0·30 N curve differed from those on the higher force curves (P<0·01), eithermoving into recent extraction sites or healing sites. Comparison between 0·60 N and 1·36 N indicated that mesial molar movement did not differfrom each other after day 5.③The classical toothmovement curve had three parts that represent distinctly different processes: early movement;delay;later movement.Conclusion　①The tooth on the recent extraction side moved faster than that on the healed side.②Moderate force maybewas the optimal orthodontic force. It could be overloaded, but resulted in no further enhancement of tooth movement.

Objective　The purpose of this study was to investigate the physiological process of healing after tooth extrac- tion and the biological reaction of toothmovement into extraction siteswith the aim of selecting optimal time of toothmovement into extraction sites clinically.Methods　Extraction of upper first molars were performed on 30 male Sprague-Dawley rats which were divided equally into 5 groups. Orthodontic appliance was placed at different time after tooth extraction in order to move the maxil- lary second molars mesially into the extraction spaces. The animalswere injected continuouslywith tetracycline and calcein for two days before appliance activation and animal sacrifice. Undecalcified mesio-distal specimans 65~100 microns of thickness were prepared. The quantification of bone remodeling parameters on tooth movement into extraction sites at different time was performed by histomorphometric measurements and computer image analysis.Results　①The bone turnover had two bone modeling process- es: resorption under pressure and formation in tension.②The bone resorption was more active on the mesial surface (pressure side) than that on the distal surface (tension side). While bone formationwasmore active on the distal surface (tension side) than that on the mesial surface (pressure side).③Both the resorptive parameters and the formative parameters across time were mani- fested by a peak at day 7 aftertooth extraction.Conclusion　①Orthodontic retraction into extraction sites should be initiated at an early stage after tooth extraction, so that the advantage of bone remodeling in extraction sites was used.②The optimal time of tooth movement into extraction sites clinically was about a week after tooth extraction.

Objective　The purpose of this studywas to compare the data of three-dimensional soft tissue obtained by us- ing a three-dimensional digital photogrammetry and the two-dimensional data obtained by using a conventional cephalometry.Meth- ods　Three-dimensional characters of facial soft tissue were obtained by using four digital cameras. The authors developed neces- sary hardware and software systems and applied in stereophotogrammetry to obtain the data of three-dimensional facial soft tissues. A total of 40 people with normal occlusion, including 20 males and 20 females, were examinedwith both three-dimensional soft ti- ssue facial morphometry and cephalometry. Three-dimensional soft tissue facial morphometry was performed, and their relations with facial cephalometry were analyzed.Results　Significant correlations were found between 6 pairs of linear measurements, 4 pairs of angular measurements and 3 pairs of linear distant ratio measurements. The data obtained by three-dimensional facial soft tissue morphometry and two-dimensional cephalometry was identical.Conclusion　There was a correlation between the three-di- mensional softtissue facial morphometry and facial cephalometry. The data obtained bythe three-dimensional softtissue facial mor- phometry can partially represent facial hard tissue.

Objective　A functional VEGF-C cDNA was cloned from a patient with squamous cell carcinoma (SCC) of tongue in orderto study the important role of vascular endothelial growth factor (VEGF)-C in lymphatic dissemination of malignan- cies in gene level.Methods　RT-PCR was employed to clone the human VEGF-C encoded cDNA from a surgical specimen of a lingual SCC patient. Then itwas subcloned into plasmid vector pCRII and sequenced.Results　A1·1 kb human VEGF-C cDNA fragmentwas amplified from the lingual SCC. The sequencing results of the fragment demonstrated that it had 99·6% similarity with the reported human VEGF-C cDNA (representing the 559~1 611 bp according the sequence of Genbank Entry X94216). Conclusion　An encoded fragment VEGF-C cDNAwas successfully cloned from a lingual SCC and provided a necessary material for further study.

Objective　To evaluate whether the vascular endothelial growth factor (VEGF)-C cDNAwhich cloned from a patient with squamous cell carcinoma (SCC) of tongue can encode a functional protein or not.Methods　RT-PCRwas employed to clone the functional VEGF-C fragment from the surgical specimen of a lingual SCC patient. Then it was subcloned into expres- sive plasmid vector pBKCMV, whichwas transfected intoE.colito examine its expression.Results　Atruncated human VEGF- C cDNA fragment was amplified from the lingual SCC. The sequencing results of the fragment demonstrated that it had 99.6% similaritywith the reported human VEGF-C cDNA (representing the 559~1611 bp according the sequence of Genbank Entry X94216). Induced with IPTG, theE.coliXL1-Blue MRF′containing the recombinant pBK-VEGF-C expressed a 56 000 fusion protein, which can be recognized by polyclonic anti-humanVEGF-C antibody.Conclusion　Afunctional fragmentVEGF-C cDNA was cloned from a lingual SCC. Itwill promote more intensive research on the function of VEGF-C and its relationshipwithmetas- tasis of oral SCC.

Objective　The aim of this paper is to introduce the clinical and laboratory procedures of fabricating silicone gingival epithesis and evaluate the long-term effects of the epithesis.Methods　Flexible gingival epithesiseswere fabricated bythe same way of fabricating partial denture, and their effects were evaluated in 31 patients by following up for 8~20 months.Results 　Patients′responses to appearance showed that their esthetic appearance had been much improved in all of the patients and the comfort and retention of their epithesises varied from good to excellent in almost all the patients. Discoloration of the epithesises was noticed by the patients within ten months in average. Doctors′examination confirmed patients′responses, and caries was de- tected at the necks of teeth covered by epithesises and slight gingivititiswas discovered in the area underthe epithesises in two cas- es.Conclusion　Flexible gingival epithesis is a simple and effective method for correcting gingival recession, and the fabrication is simple and don’t need special equipment. However, discoloration of the epithesis remains a problem.