ABSTRACT
<p><b>OBJECTIVE</b>To investigate more deeply the function and mechanism of DSPP during tooth development.</p><p><b>METHODS</b>Explants of tooth germs from embryonic 17th 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 30 mumol/L, 15 bp antisense oligodeoxynucleotide targeted to DSPP mRNA. After 10 ds, the explants were examined by transmission electron microscope. The width of dentin matrix at the tip of the cusps were then measured and statistically analyzed with Student t-test.</p><p><b>RESULTS</b>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 (2.5 microns) was thinner compared to the control ones (3 microns, P < 0.001). In addition, the collagen fibers in extracellular matrix were disorganized.</p><p><b>CONCLUSION</b>These findings indicated that DSPP played an important role in keeping tooth normal development, as well as in dentin mineralization by maintaining odontoblasts' secreting ability and controlling fiber structure and orientation.</p>
Subject(s)
Animals , Mice , Embryo, Mammalian , Extracellular Matrix Proteins , Mice, Inbred BALB C , Microscopy, Electron , Molar , Oligoribonucleotides, Antisense , Pharmacology , Phosphoproteins , Protein Precursors , Pharmacology , Sialoglycoproteins , Tooth GermABSTRACT
Objective:To examine the polymerization shrinkage stress of three universal hybrid composite resins by photo-elastic analysis.Method:Epoxide resin disks (d=80 mm,h=4 mm) with a cylindrical cavity (d=4 mm) in the middle were prepared.Composite resins of Charisma,TPH Spectrum and Esthet-X were respectively filled in the cavities for the formation of specimens.Eight specimens were made for each resin.The resin specimens were light cured for 40 s by Dentsply QHL75 Curing lite. Polymerization contraction stress was calculated based on the diameter of the isochromatic rings of first order obtained from the diameter of epoxide resin specimen at 1,2,3,4,5,10,20 and 30 min,1,24 and 48 h after curing. The statistical analysis was carried out with the Wilcoxon test.Results:Polymerization contraction stress rised rapidly in the first 10 min after curing. 1 and 24 h after curing the shrinkage stress(MPa) of Charisma were 2.893 6?0.1 and 4.190 4?0.1,while that of Esthet-X were 2.291 7? 0.1 and 3.143 9? 0.3 ,respectively.The shrinkage stress values of TPH spectrum was between those of Charisma and Esthet-X 24 h after curing. 79% specimens showed shrinkage stress releasing during 24 and 48 h after curing.Conclusion:The rates of the shrinkage stress of the three studied resin composites are different.
ABSTRACT
Objective:To determine whether the immortalized human odo nt oblast-like cell line hTERT-hOd-l has transformed phenotype. Methods: The tumorigenicity, anchorage-independent growth, serum dependence and contact inhibition of the immortalized human odontoblast-like cell line hTERT- hOd-l were observed during continuous culture in vitro. Results: The cells showed to be nontumorigenic in nude mice, and to have no anchorag e-independent growth. The cells maintained the normal serum dependence and cont act inhibition. Conclusion:hTERT-hOd-l is a normal cell line w ithout obvious transformed phenotype.
ABSTRACT
Objective: To investigate the root canal curvatures of anterior teeth in the Han nationality in Shaanxi province.Methods:392 permanent anterior teeth were examined by indirect digital radiography both from labiolingual and mesiodistal directions according to Schneider method, root canal curvatures were analyzed by electronic rule.Results:Root canals of the anterior teeth were mainly of type I. High rate of root canal curvature was found in maxillary canines (68.5%), and most of curves were in the apical third. There was a relationship between the root canal curvatures of maxillary canine and age(P=0.03). Conclusion:Root canal curvatures of maxillary canine are complicated,especially in maxillary canines. The root canal curvatures of maxillary canine decreased with aging.
ABSTRACT
Objective:To clone and sequence cDNA of MH2 domain of Smad1 gene from human dental papilla cells. Methods:Total RNA was isolated from primarily cultured human dental papilla cells and reversely transcribed into single stranded cDNA.The desired DNA product was obtained by PCR with two gene specific primers.The segment was inserted into PUC19 vector and the plasmid was transformed into E.coli JM109.The double stranded cDNA of positive clone was sequenced.Results:The sequence of MHz domain of Smad1 cloned from human dental papilla cells was consistent with that reported by Hoodless et al. Conclusion:Smad1 exists in human dental papilla cells,BMP signaling may be mediated by smad1 in human dental papilla cells.
ABSTRACT
Objective: To examine the effect of mouthwashing before dental procedure on environmental pollution of microorganism in dental clinic. Methods: Air samples in dental clinic after tooth preparation whether using mouthwashes or not pre operationally were collected and cultured with blood agar plates, the bacteria colonies formed on the plates in different groups were counted as the index for air contamination. Results: Environmental contamination from tooth preparation in dental clinic could be reduced significantly by using mouthwash pre operationally( P 0.05), but the size of the colonies formed on the plates in Kou Jie Su group was smaller than that in drinking water group. Conclusion: Environmental contamination from tooth preparation in dental clinic can be reduced by using mouthwash pre operationally. Combination of the pre operational mouthwashing with vacuum aspirator or ventilation installation may be a better way to control the possible cross infection in dental clinic.
ABSTRACT
Objective:To investigate if transforming growth factor-?1 (TGF-?1) induces apoptosis in odontoblast cell line MDPC-23. Methods:MDPC-23 cells were treated with TGF-?1 at 0.5,2.5 or 10 ng/ml for 48 h,apoptosis of MDPC-23 cells was detected by annexin V and propidium iodide (PI) staining, cell death detection ELISA and DNA electrophoretic analysis. Results: Consistent results were obtained from three different methods.TGF-?1 at 0.5-10 ng/ml induced apoptosis of MDPC-23 cells in a dose-dependent manner. Conclusion:TGF-?1 may paly a role in apoptosis of odontoblasts.
ABSTRACT
Objective: To evaluate the function of dentin sialophosphoprotein (DSPP) during mouse teeth development. Methods:Expression of DSPP mRNA in the first molar of Balb/c mice at different developmental stages was detected by in situ hybridization. Resullts: DSPP mRNA in odontoblasts was detected in the samples at middle bell stage and ran through the later stages. In addition, it was detected in ameloblasts as well as in preameloblasts. Conclusion: DSPP expresses with temporospatial characters. It may play an important role in tooth morphogenesis