Objective: To develop a PCR method for detecting S treptococcus sobrinus (S.s) in conventional culture. Method: A pair of specific primers were designed from the dexA gene of S.s , the genome DNA of 12 strains of Mutans Streptococci (8 serotypes from a ～h) and 23 species of the bacteria which were commonly found in oral cavity wer e tested by PCR amplification, the PCR products were identified by electrophore sis. Result: Only S.s of serotype d and g could produ ce 277 bp DNA fragments, and the PCR method could detect less than 1 000 copies of S.s. Conclusion: PCR method is specific and sen sitive in the detection of S.s.

Objective:To study the multiple alternative sp l iceosome of nfic gene in postnatal rat molar tissues. Methods: 3 d postnatal SD rat molar tissues were removed and mRNA was obtained by magne tic beads coupled with oligo-dT18. Two pairs of primers specific to the nfic gene were designed, and nfic gene in the rat molar tissue was amplified b y RT-PCR method.The fragments were inserted into competent DH5? bacteria.Posit ive clones were selected randomly and evaluated by enzyme digestion and sequenci ng.Results:Three alternative spliceosomes of nfic gene with the size of 1.5 kb,900 bp and 650 bp respectively were obtained. The spliceosome s were named rNFIC-1、 rNFIC-2 and rNFIC-3 respectively.Conclusion s:The nfic gene is expressed in postnatal rat molar, and there is a multiple alternative splicing way for the nfic gene to play function.

Objective To study the influence of different root exposure in long-term effect of crown lengthening .Methods To-tally 142 teeths(66 of the front teeths ,46 of premolars teeths ,30 of molars teeths ) of 110 patients collected from August 2010 to October 2012 in stomatological hospital to affiliated zunyi medical college were chosen as research subjects ,then they were randomly divided into the experimental group and the control group .There were 33 anterior teeths ,23 premolar teeths and 15 molar teeths in each group .The experimental group accepted 3 mm root exposure while the control group accepted 4 mm root exposure .The post-operative effect of the two groups was compared .Results The tooth mobility of the anterior cases of control group after 3 months was statistically higher than that of the experimental group (P<0 .05) and the difference of tooth mobility between the two groups in other teeths and times was not statistically significant (P>0 .05) .The bleeding index after 3 months ,the anterior teeths ,premo-lar teeths and molar teeths of the experimental group was statistically higher than that of the control group (P<0 .05) ,while the difference of tooth mobility between the two groups in other times was not statistically significant (P>0 .05) .The postoperative probing difference of depth and attachment loss between the two groups showed no statistically significant (P>0 .05) .Conclusion The root exposure of 3 mm and 4 mm both have a significant effect in crown lengthening .But for the aesthetic point of view ,3 mm should be taken as the root exposure of the anterior cases .

Objective:To observe the temporal and spatial expression and function of mcpr1 gene during murine tooth germ development.Methods:The expression of MCPR1 at different stages of mouse tooth germ were detected by immunohistochemical staining.Results:MCPR1 expression was detected at all stages of tooth germ, but the distribution patterns at various stages were different. It indicated that the temporal and spatial expression pattern of MCPR1 during murine tooth germ development was specific.Conclusion:mcpr1 might play an important role in modulating the differentiation and mature of enamel organ.

Objective:To evaluate the effects of arginine on the mechanic properties of Clinpro? pit and fissure sealant.Methods:Experimental pit and fissure sealants were formulated with arginine at 3％,5％,and 10％(Arg3,Arg5 and Arg10)respectively added into ClinproTM,the surface microhardness(SMH),degree of conversion(DC)and microleakage of the samples were investigated.The morphology of different pit and fissure sealants after curing were observed by scanning electron microscope(SEM).The concentration of arginine released at different time points were analyzed by Liquid Chromatography Mass Spectrometry(LC-MS/MS).Results:The SMH and DC was not statistically different among the groups,the microleakage level in Arg 10 group was higher than that in other groups(P＜0.05),and there was no significant difference among other groups.There were some aggregation of arginine particles in modified agents under SEM.The Arg5 showed a significantly higher release rate of arginine at any time point than Arg3 in 24 hours(P＜0.05).Conclusion:Incorporation of 5％arginine does not affect the physical and mechanical properties of ClinproTM pit and fissure sealant and exhibites good arginine release ability.