Objective To compare the effect of different nickel-titanium rotary files on fracture resistance of teeth by observing status of dentinal microcracks after root canal preparation with.Methods 6 5 mandibular anterior teeth with single oval canal were randomly divided into three experimental groups (n=20)and a control group (n=5),SAF、ProTaper Universal and ProTaper Next system were used to prepare root canal in experimental groups,while the control group were left unprepared.Roots were sectioned from 3,6,9 mm to the apex,its status of dentinal microcracks was evaluated under a stereomicroscope.Results Root fracture inci-dence rate of group ProTaper Universal was significantly higher than that of group SAF and group ProTaper Next (P<0.05). There were no statistically significant differences in incidence rate of dentinal microcracks between group SAF and group ProTaper Next (P>0.05).Conclusion Roots with oval shaped canal prepared with SAF and ProTaper Next produce less dentinal microc-racks,which decrease risk of vertical root fracture.

Objective:To establish a model for the study of tooth initiation and early development by in vitro culture of mouse mandibular arch . Methods:42 mandibular arches of 11dpc fatal mouse were dissected and cultured in Trowell organ culture system for 11 days.Regular histologic observation was performed to observe the initiation and development of tooth.Results: Mandibular arches grew well in Trowell culture system.The initiation and early development of tooth was found.The explants maintained to cap stage.On day 11,necrosis of the cultured mandibular arches was observed and the culture was ended. Conclusion:In vitro cultured mandibular arch can be used as a model for the study of tooth initiation and early development.

Objective: To observe the clinical disinfection effect of root canal with non-filling medication. Methods: 36 patients who required root canal therapy(RCT) for apical periodontitis (acute or chronic) or pulp necrosis were involved in the study.RCT was completed after two visits in both groups. Non-filling medication was used as disinfection in 18 teeth of 18 patients (experimental group) while FC in another 18 teeth of 18 patients (control group) randomly at first visit.One week later,root canal was regularly filled to complete RCT.From each case, bacteria specimens were collected and identified before sealing and filling. Results: Bacteria were detected in every specimen in both groups before sealing,which were mixture of aerobes and anaerobes.One week later,only one strain was detected in one specimen of each group. Conclusion: Non-filling medication can be used as an effective disinfection to sterilize root canal.

Objective:To investigate the expression of dental matrix protein 1(DMP1)in carious human permanent teeth and its possible role during the reparative process after pulp injury.Methods:10 of noncarious third molars (NC),10 of shallow carious (SC),10 of intermediate carious (IC) and 10 of deep carious (DC) were prepared for the detection of DMP1 in odontoblasts by immunohistochemical staining. DMP1 expression in odontoblasts was analyzed by image analysis system and expressed as integral optical density (IOD).Results:DMP1 was majorly detected in cytoplasms and processes of odontoblasts and odontoblast-like cells.The IOD values in the groups of NC,SC,IC and DC were 0.265?0.018,0.309?0.021,0.678?0.031 * and 0.691? 0.033 * respectively;that in the reparative dentin in DC group was 0.856?0.045 ** ( *vs NC P

Objective:To observe the expression of nuclear factor kappa B(NF-kB) during the replacement of primary and permanent teeth in dog. Methods:By immunohistochemistry, expression of NF-kB was examined in the tissues around deciduous tooth root at resorption stage in 2 dogs aged 3-4 months.Results:NF-kB positive signals were observed in the osteoclasts up to the permanent tooth germ and in odontoclasts in the medial wall of the pulp cavity of deciduous teeth.Conlusion:NF-kB may involve in the eruption of permanent teeth during the stage of the replacement of primary and permanent teeth.

Objective Comparing with traditional teaching methods of oral histopathology, to probe whether the interactive teaching system of the digital microscope can improve the teaching effi-ciency of experiment of oral histopathology courses. Methods The subjects were the 2010 grade students (40 students) and the 2011 grade students (38 students) majoring in stomatology of South Medical University, and they were evenly divided into 2 groups at random. In the first part of the ex-periment of Grade 2010, the teaching of traditional optical microscope was used in a group of experi-mental courses, and interactive teaching with digital microscope was used in the other group. In the second part of the experiment the two groups swapped the teaching method. While in the whole exper-iment of Grade 2011, traditional optical microscopes were adopted in one group, and in contrast, the interactive teaching system of the digital microscope was adopted in the other group. The P values of the 5 indexes were less than 0.05. After the courses, the 2010 grade students received the questionnaire survey and the 2011 grade students received the quiz about the experimental course, and then the evaluation results of the two groups were compared for t inspection, using SPSS software t test. Result The questionnaire results of Grade 2010 showed that the scores of digital microscope interactive group were higher than those of traditional teaching group in satisfaction with teaching , teacher-student interaction, classroom atmosphere active degree, learning interest, and the understanding of the teach-ing content. The experiment course content test results of Grade 2011 showed that the digital interactive group students averaged 46.26, while the average score of the traditional teaching group was 42.78%. The difference between the two groups had statistical significance, P=0.001. Conclusion Compared with the traditional teaching methods, the interactive teaching system of the digital microscope can enhance the academic grades, improve the teaching efficiency of experiment of oral histopathology courses, and elevate the teaching quality.

砄bjective: To investigate the effect of calcitonin gene related peptide(CGRP) on calcification function of human dental pulp cells(HDPCs) in vitro . Methods: HDPCs cells were exposed to calcitonin gene related peptide at the dosages(mol/L) of 10 -12 , 10 -10 and 10 -8 for 3,6,9, 12 and 15 days respectively. Cell growth was studied by cell counting , alkaline phosphatase(AL) by a AL kit, osteocalin by immunoradiological tecnique and type I collagen mRNA expression by RT PCR. Results: CGRP did not show any effect on the growth of HDPCs, but it increased the expression of AL, osteocalin and type I collagen mRNA in HDPCs in a dose dependent and not time dependent manner. Conclusion: CGRP plays an important role in promoting differentiation and calcification function of HDPCs

Objectives:To study the preparation techniques of gelatin microspheres encapsulated with sodium fluoride and evaluate the anticaries functions in dental plaque model in vitro. Methods:Fluoride gelatin microspheres were prepared by emulsion polymerisation method. The encapsulation rate and drug contents were tested by ISE. In vitro inhibition of demineralization were also examined. Results:The mean size of fluoride GMS was (16.81?8.77)?m.The encapsulation rate was 76.73%.The drug content was 5.61%.The release profile in vitro showed sustained effects. Fluoride GMS can prevent demineralization more efficiently. Conclusions:Fluoride gelatin microspheres may be an promising topical fluoride release system.

ObjectiveTo survey and analyze the changes of dental medical students' concerns before and after their internship in order to provide practical evidences for intern orientation and junior students education.MethodsAnonymous questionnaires were designed with single choice and multiple-choices and were accomplished by 175 dental medical students of different grades to investigate their' concerns before and after the clinical internship and choices for future employment.Results 47％ freshmen,43％ junior,45％ graduates were willing to work in dental restoration field,30％sophomore and 39％ senior were willing to work in orthodontics field.Before the internship,the most concem of 97％ students was the teaching quality of the practice hospital; 67％ students worried that patients may unsatisfy with the treatment.After the internship,the quality of the practice hospital was considered most important by 79％ students; 51％ students worried that internship may influence the postgraduate entrance exam.ConclusionTeachers should strengthen their self-cultivation and cope with the key concerns before the practice based on the investigation and survey after the practice.Meanwhile teacher should provide employment guidance for students based on students' interests and practice skill ability,encourage them to broaden their horizon and pay attention to the long-term interests in an aim to pave the way for future employment.

BACKGROUND:Previous studies have confirmed the presence of bis-(3'-5')-cyclic dimeric guanosine
monophosphate signaling pathway in Streptococcus mutans, which construct the streptococcus mutans gcp gene knockout strains.
OBJECTIVE:To compare the gene expression differences between Streptococcus mutans wild strains and gcp mutant strains, and to screen the biofilm-related genes from them for the fol ow-up study.
METHODS:The total RNA of two kinds of strains were extracted and stained with cy3 and cy5 respectively after reverse transcription. The gene chip was scanned after hybridization and the differential gene were obtained
through the data analysis. The different expression genes were verified by real-time PCR.
RESULTS AND CONCLUSION:Differential genes were mainly relative about glucose metabolism and biofilm formation. We selected two genes for real-time PCR verification. The PCR results were consistent with the
microarray results. After Streptococcus mutans gcp gene knockout, the gene expressions of gcp mutant strains were upregulated and the gene expressions of phosphotransferase system were downregulated, this result
suggested that two different genes were related with the c-di-GMP signal pathway downstream.