Research progress in ecological prevention of dental caries / 中华口腔医学杂志

Dental caries is one of the most common oral diseases around the world. Dental plaque attached to the surfaces of teeth is the main biological factor leading to caries. Although fluoride is still one of the most commonly used methods to prevent caries, with the change of epidemiological characteristics of caries and the update of the understanding of caries etiology, it is necessary to use other ecological methods such as antimicrobial peptides, arginine, probiotics and natural products, etc. to enhance the effect of fluoride in preventing dental caries. The present article reviews the research progress on the ecological approaches for caries prevention in recent years.

Immunogenicity and prediction of epitopic region of antigen Ag I/II and glucosyltransferase from Streptococcus mutans / 华中科技大学学报（医学）（英德文版）

The levels of Streptococcus (S.) mutans infections in saliva were evaluated and a comparison for specific antibody levels among children with different levels of S. mutans infection was made. The promising epitopic regions of antigen AgI/II (PAc) and glucosyltransferase (GTF) for potential vaccine targets related to S. mutans adherence were screened. A total of 94 children aged 3-4 years were randomly selected, including 53 caries-negative and 41 caries-positive children. The values of S. mutans and those of salivary total secretory immunoglobulin A (sIgA), anti-PAc and anti-Glucan binding domain (anti-GLU) were compared to determine the correlation among them. It was found the level of s-IgA against specific antigens did not increase with increasing severity of S. mutans infection, and the complete amino acid sequence of PAc and GTFB was analyzed using the DNAStar Protean system for developing specific anti-caries vaccines related to S. mutans adherence. A significantly positive correlation between the amount of S. mutans and children decayed, missing, and filled teeth index was observed. No significant difference was detected in specific sIgA against PAc or GLU between any two groups. No significant correlation was found between such specific sIgA and caries index. A total of 16 peptides from PAc as well as 13 peptides from GTFB were chosen for further investigation. S. mutans colonization contributed to early children caries as an important etiological factor. The level of sIgA against specific antigens did not increase with increasing severity of S. mutans infection in children. The epitopes of PAc and GTF have been screened to develop the peptide-based or protein-based anti-caries vaccines.

Push-out bond strength of self-adhesive methacrylate resin-based sealers to root dentin / 华中科技大学学报（医学）（英德文版）

This study examined the adhesive strength of two self-adhesive methacrylate resin-based sealers (MetaSEAL and RealSeal SE) to root dentin and compared them with RealSeal and AH Plus in properties. A total of 48 extracted human single-rooted teeth were used to prepare the 0.9-mm thick longitudinal tooth slice (each per tooth). Standardized simulated canal spaces of uniform dimensions were prepared in the middle of radicular dentin. After treated with 5.25% sodium hypochlorite (NaOCl) and 17% EDTA, tooth slices were allocated randomly to four groups (n=12) in terms of different sealers used: MetaSEAL, RealSeal SE, RealSeal, and AH plus groups. The simulated canal spaces were obturated with different sealers in each group. There were 10 slabs with 20 simulated canal spaces (n=20) used in each group for push-out testing. The failure modes and the ultrastructures of fractured sealer-dentin interfaces were examined. The remaining 2 slabs in each group underwent partial demineralization for observation of the ultrastructure of resin tags. The results showed that the push-out bond strength was 12.01±4.66 MPa in MetaSEAL group, significantly higher than that in the other three groups (P<0.05). Moreover, no statistically significant differences were noted in the push-out bond strength between RealSeal SE (5.43±3.68 MPa) and AH Plus (7.34±2.83 MPa) groups and between RealSeal SE and RealSeal (2.93±1.76 MPa) groups (P>0.05). Mixed failures were predominant in the fractured sealer-dentin interfaces in MetaSEAL and AH Plus groups, while adhesive failures were frequently seen in RealSeal SE and RealSeal groups. In conclusion, after complete removal of the smear layer, MetaSEAL showed superior bond ability to root dentin. The RealSeal SE is applicable in clinical practice, with its adhesive strength similar to that of AH Plus. The self-adhesive methacrylate resin-based sealer holds promise for use in endodontic treatment.

Comparison between visual clinical examination and the replica method for assessments of sealant retention over a 2-year period / 国际口腔科学杂志·英文版

To compare the levels of agreement and the survival rates of sealant retention for different sealing materials over a 2-year period assessed using the visual clinical examination and replica methods, sealant retention data were obtained by visual clinical examination and from replicas of the same sealed tooth at baseline and at 0.5-, 1- and 2-year evaluation points in 407 children and were compared for agreement using kappa coefficients. Survival curves of retained sealants on occlusal surfaces were created using modified categorisation (fully retained sealants and those having all pits and fissures partly covered with the sealant material versus completely lost sealants that included pit and fissure systems that had ≥1 pit re-exposed) according to the Kaplan-Meier method. The kappa coefficient for the agreement between both assessment methods over the three evaluation time points combined was 0.38 (95% confidence interval (CI): 0.35-0.41). More sealant retention was observed from replicas than through visual clinical examination. Cumulative survival curves at the three evaluation times were not statistically significantly higher when assessed from replicas (P=0.47). Using the replica method, more retained sealant material was observed than through visual clinical examination during the 2-year period. This finding did not result in a difference in the survival rates of sealants assessed by the two assessment methods. When replicas cast in die stone are used for assessing sealant retention, the level of reliability of the data is higher than that of data obtained through the commonly used visual clinical examination, particularly if such assessments are conducted over time.

Push-out bond strength of self-adhesive methacrylate resin-based sealers to root dentin / 华中科技大学学报（医学）（英德文版）

This study examined the adhesive strength of two self-adhesive methacrylate resin-based sealers (MetaSEAL and RealSeal SE) to root dentin and compared them with RealSeal and AH Plus in properties. A total of 48 extracted human single-rooted teeth were used to prepare the 0.9-mm thick longitudinal tooth slice (each per tooth). Standardized simulated canal spaces of uniform dimensions were prepared in the middle of radicular dentin. After treated with 5.25% sodium hypochlorite (NaOCl) and 17% EDTA, tooth slices were allocated randomly to four groups (n=12) in terms of different sealers used: MetaSEAL, RealSeal SE, RealSeal, and AH plus groups. The simulated canal spaces were obturated with different sealers in each group. There were 10 slabs with 20 simulated canal spaces (n=20) used in each group for push-out testing. The failure modes and the ultrastructures of fractured sealer-dentin interfaces were examined. The remaining 2 slabs in each group underwent partial demineralization for observation of the ultrastructure of resin tags. The results showed that the push-out bond strength was 12.01±4.66 MPa in MetaSEAL group, significantly higher than that in the other three groups (P0.05). Mixed failures were predominant in the fractured sealer-dentin interfaces in MetaSEAL and AH Plus groups, while adhesive failures were frequently seen in RealSeal SE and RealSeal groups. In conclusion, after complete removal of the smear layer, MetaSEAL showed superior bond ability to root dentin. The RealSeal SE is applicable in clinical practice, with its adhesive strength similar to that of AH Plus. The self-adhesive methacrylate resin-based sealer holds promise for use in endodontic treatment.

Effects of interleukin-1β on mineralization potential of dental pulp stem cells / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the effects of pro-inflammatory cytokine interleukin-1β (IL-1β) on mineralization potential of dental pulp stem cells (DPSC).</p><p><b>METHODS</b>Rat DPSC were cultured in vitro and randomly divided into three groups, IL-1β (10 µg/L), osteogenic inductive medium and non-osteogenic inductive medium. After 3, 7, and 12 days of treatment, the cultures were evaluated for cell proliferation and calcium deposit. Real-time polymerase chain reaction was used to detect the gene expression levels of osteocalcin (OC), bone sialoprotein (BSP), dentin sialophosphoprotein (DSPP) and dentin matrix protein 1 (DMP-1). In vivo test, after 3 day's treatment with IL-1β, the cell-scaffold complexes were implanted subcutaneously in mice for 8 weeks. Histological analysis was performed to evaluate hard tissue formation.</p><p><b>RESULTS</b>In vitro test, after 3-day's treatment, IL-1β improved cell proliferation to 137.22 DNA µg/L and cell viability becomes (97.12 ± 7.18)% of control. The gene expression levels of OC, BSP, DSPP and DMP-1 are (378.19 ± 16.22)%, (427.12 ± 18.22)%, (247.19 ± 10.11)% and (198.29 ± 10.23)% respectively. The results of IL-1β's group was notable increased compared with non-osteogenic induction medium and the statistical differences are significant. IL-1β induced the odontogenic differentiation of DPSC. However, these effects tended to continuously decrease with treatment time. Histological analysis demonstrated that in the group treated with IL-1β hard tissue was markedly formed in vivo.</p><p><b>CONCLUSIONS</b>IL-1β may induce the mineralization of DPSC and play an important role in host defenses and tissue repair.</p>

Long-term results of dual anti-collagen membrane in guided tissue regeneration / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the long-term clinical effect of dual anti-collagen membranes in guided tissue regeneration (GTR).</p><p><b>METHODS</b>This randomized clinical trial included 26 teeth in 24 patients, presenting a total of 31 lesions consisting of intrabony defects and furcation defects. Twenty-six teeth were divided into two groups and treated by GTR with dual anti-collagen membranes and atelocollagen membranes, respectively. At baseline, 6 months, 1, 3 and 6 years, the following parameters were recorded: clinical attachment level, probing depth, gingival recession and the quantity of alveolar bone analyzed by computer assisted densitometry image analysis (CADIA).</p><p><b>RESULTS</b>At 1 year after GTR surgery, the gain of clinical attachment in dual anti-collagen membranes group was (3.93 ± 1.74) mm, compared with (2.25 ± 1.90) mm in atelocollagen group (P = 0.044). The increasing of the value of CADIA in dual anti-collagen membrane and atelocollagen group were (53.14 ± 21.35) and (32.96 ± 17.97), P = 0.031. At 3 and 6 years, clinical parameters remained basically stable in both groups, compared to that at 1 year after surgery.</p><p><b>CONCLUSIONS</b>The regeneration of periodontal tissues obtained by GTR with dual anti-collagen membranes could be maintained on a long-term basis.</p>

Evaluation of preparation of curved root canals using hand-used ProTaper / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the shaping ability of hand-used ProTaper on curved canals using Endodontic Cube.</p><p><b>METHODS</b>Fifty-four curved root canals in vitro were selected and divided into three groups according to the curved degree (alpha), group A: 0 degrees < or = alpha < 25 degrees , group B: 25 degrees < or = alpha < 40 degrees , group C: 40 degrees < or = alpha < 55 degrees . Endodontic Cube was assembled, and each sample was sectioned perpendicular to the axis of the tooth into four sections with Isomer-Buhler in low speed. Then the root canals were prepared with hand-used ProTaper. Before and after shaping, photograph of all the sections were taken under a stereomicroscope. Statistical analyses were performed.</p><p><b>RESULTS</b>The dentin cutting quantity of the whole canal prepared with ProTaper in group B and C was larger than that of group A. The deviation distance of the whole canal prepared by ProTaper in group C was significantly larger than that in group A, and the deviation distance in middle portion larger than that in group B. The maintaining ability in the middle portion of group C by ProTaper was worse than that of group A and B.</p><p><b>CONCLUSIONS</b>The curvature of root canal may increase the cutting quantity of the -dentin and reduce the ability of remaining original canal shape prepared by ProTaper.</p>

Human papillomavirus as an independent predictor in oral squamous cell cancer / 国际口腔科学杂志·英文版

<p><b>AIM</b>There is an increasing evidence for the role of high risk human papillomavirus (HPV) in the pathogenesis of oral squamous cell carcinoma (OSCC). The purpose of this study is to evaluate the relevance of HPV infection to the survival and prognosis of OSCC.</p><p><b>METHODOLOGY</b>Fifty-two patients with OSCC were followed from 4 to 88 months with a median of 50.7 months. HPV DNA was identified in formalin-fixed, paraffin-embedded tumor specimens by nested PCR with MY09/MY11 and GP5+/GP6+ primer pairs and the HPV genotype was determined by direct DNA sequencing. Association between the HPV status and risk factors for cancer as well as tumor-host characteristics were analyzed. Survival curves were calculated by the Kaplan-Meier method and analyzed using the log-rank test.</p><p><b>RESULTS</b>HPV was found in 40.4% of the tumors with HPV16 accounting for 63.5%, HPV18 for 30.8%, HPV6 for 3.9% and HPV11 for 1.8%. No infection with more than one HPV genotype was detected. HPV infection was significantly associated with poor histological grade, TNM stage I-II, alcohol usage and no smoking status. Multivariate analysis showed that HPV had an independent prognostic effect on the overall survival after adjusting other confounding factors such as histological grade, TNM stage and tobacco usage. The presence of HPV was significantly correlated with a better survival in patients with OSCC.</p><p><b>CONCLUSION</b>HPV infection can act as an independent predictor for the survival and prognosis of OSCC.</p>

The TP53 and RPS6 alterations at the invasive tumor front, center and stroma of oral squamous cell carcinoma / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To assess the difference of genetic alteration patterns among different areas in the same oral squamous cell carcinoma (OSCC).</p><p><b>METHODS</b>Studied the loss of heterozygosity (LOH) and microsatellite instability (MI) at chromosomal loci TP53 and RPS6 on the invasive tumor front (ITF), the center/superficial part and stroma cells by combining laser capture microdissection (LCM) and PCR technique.</p><p><b>RESULTS</b>There existed a high frequency of LOH and MI on chromosomes loci TP53 and RPS6. The frequency of RPS6 and TP53 aberration at the stroma was 23.5% (4/17) and 43.8% (7/16), respectively. While in epithelial part (both ITF and center), it reached up to 64.7% (11/17) and 70.6% (12/17) respectively, and the difference was significant (P < 0.05). The overall frequency of the two markers was statistically higher at the ITF (20/32) than at the center/superficial part (15/34) (P < 0.05).</p><p><b>CONCLUSIONS</b>The current study revealed that genetic alterations were different in different areas of the same tumor and there existed a relationship between the histological grading and genotypes of OSCC.</p>

Location of GbpC protein in Streptococcus mutans UA159 / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To determine whether the glucan binding protein C (GbpC) with LPXAG motif is anchoring to the cell wall of the Streptococcus mutans UA159 (S. mutans UA159).</p><p><b>METHODS</b>S. mutans UA159 GbpC C terminal gene segment was amplified by PCR, the gene sequences and the deduced amino acid sequences were analyzed. In order to locate the GbpC of S. mutans, the study isolated the wall fraction following digestion of the cell wall by N-acetylmuramidase, and the GbpC was detected by Western blot analysis. GbpC S. mutans UA159 was located with gold particles. Furthermore, the dextran-dependent aggregation (ddag) phenotype of the S. mutans UA159 under stress condition was observed.</p><p><b>RESULTS</b>S. mutans UA159 GbpC C-terminal LPXTG motif was replaced by LPXAG motif. GbpC was observed in the cell wall component and immunogold experiment showed that the gold particles distributed around the cell wall surface. S. mutans UA159 exhibited ddag+.</p><p><b>CONCLUSIONS</b>GbpC with LPXAG motif was still anchoring to the cell wall.</p>

Immunolocalization of Secretion complex in Streptococcus mutans / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the distribution pattern of the Secretion complex in Streptococcus mutans by means of the subcellular localization of SecA and SecY.</p><p><b>METHODS</b>The specificity of anti-SecA antibody and the anti-SecY antibody were examined by Western blot. An indirect postembedding immunogold method was used to determine the subcellular localization of the SecA and SecY in the cytoplasmic membrane of the Streptococcus mutans GS-5.</p><p><b>RESULTS</b>Immunoblotting results showed that the anti-SecA antibody and the anti-SecY antibody specifically recognized a single band of about 95 000 and 47 800 respectively. Immunogold electron microscopy revealed a single intense focus of gold particles at a discrete location on the cytoplasmic membrane of the Streptococcus mutans GS-5.</p><p><b>CONCLUSIONS</b>SecA and SecY clustered to an asymmetric microdomain, which suggests that Sec complex present a uni-site on the cytoplasmic membrane of Streptococcus mutans.</p>

Survey of root canal curvature in maxillary anterior teeth / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate root canal curvature in maxillary anterior teeth.</p><p><b>METHODS</b>About 400 human maxillary anterior teeth were examined by indirect digital radiography both from labiolingual and mesiodistal directions. The root canal curvature was analyzed.</p><p><b>RESULTS</b>The major sort of maxillary anterior teeth was type I. The proportion of maxillary center incisors, maxillary lateral incisors, maxillary canines curved in mesiodistal were 11.17%, 16.19% and 21.43%, in labio-lingual were 39.59%, 40.00% and 29.59%, both in labiolingual and mesiodistal directions were 4.60%, 35.24% and 24.49%. About 50% of maxillary anterior teeth were moderate curve, the degree of root canal curvature of maxillary canines was larger than that of maxillary incisors, and radius of curvature and length of the curved part of root canal of maxillary canines were smaller than that of maxillary incisors.</p><p><b>CONCLUSION</b>Root canal curvature in maxillary anterior is complex, especially in maxillary canine. In order to improve quality of root canal therapy, we need to understand types of root canal, degree of root canal curvature and radius of curvature completely.</p>

Effects of retinoic acid on differentiation of periodontal ligament cells / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the effect of retinoic acid on differentiation of periodontal ligament cells (PDLCs) and gingival fibroblasts (GFs).</p><p><b>METHODS</b>The periodontal ligament cells and gingival fibroblasts were cultured, challenged with different concentrations of retinoic acid in medium and detected for the alkaline phosphatase (ALP) activity and its mRNA by biochemical technique, in situ hybridization and RT-PCR.</p><p><b>RESULTS</b>ALP activity in normal PDLCs was higher than that in GFs. The mRNA signals were positive in PDLCs, and negative in GFs. After treated with different concentrations of retinoic acid, ALP activity of PDLCs was increased than that of the control, and its mRNA signals were enhanced, especially in 5 x 10(-6) mol/L. The treated GFs showed a slight increase of ALP activity and a weak band of mRNA signals only in 5 x 10(-6) molUL concentration.</p><p><b>CONCLUSION</b>There were differences between PDLCs and GFs in differentiating into osteoblast-like cells.</p>

Effects of Porphyromonas gingivalis lipopolysaccharide on collagen phagocytosis by human periodontal ligament fibroblasts / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the effects of Porphyromonas gingivalis (P. gingivalis) lipopolysaccharide (LPS) on collagen phagocytosis of human periodontal ligament fibroblasts (hPDLF).</p><p><b>METHODS</b>Fluorescence localization and flow cytometry was used to test the collagen phygocytosis of hPDLF stimulated by the various concentration of LPS for 48 hours in vitro.</p><p><b>RESULTS</b>The collagen phygocytosis of hPDLF was increased significantly by 0.1 microg/mL LPS (P < 0.05).</p><p><b>CONCLUSION</b>This study indicates that P. gingivalis LPS may enhance the degradation of collagen by stimulating the phagocytic activity of the hPDLF in periodontitis.</p>

Expression pattern and level of cytotoxic T lymphocyte-associated antigen-4 targeted anti-caries plasmids in eukaryotic cells / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate and compare the expression pattern and level of targeted anti-caries plasmids encoding different-size antigens in eukaryotic cells.</p><p><b>METHODS</b>The A-P fragment of PAc (surface protein antigen) was removed from pGJA-P encoding the signal peptide, extracellular domains of human CTLA-4, human Ig hinge, CH2 and CH3 domains, A-P fragment of PAc and GLU (glucan binding domain) region of GTF-I of Streptococcus mutans, to obtain the plasmid pGJGLU. pCI vector skeleton of pGJA-P or pGJGLU was replaced by pVAX1 to construct plasmids pGJA-P/VAX and pGJGLU/VAX. CTLA4-Ig-GLU fragment was removed from pGJGLU and inserted into the vector pEGFP-N1 to obtain the recombinant plasmid pGJGLU/GFP. The CHO cells were transfected with those plasmids by using liposome and the expression of fusion protein was observed with fluorescence microscope. ELISA was used to detect the expression level of fusion proteins in cultured supernatants.</p><p><b>RESULTS</b>Specific vesicles with green fluorescence could be observed in the CHO cells transfected with pGJGLU/GFP. The recombinant fusion protein could be detected in the cultured supernatants of CHO cells transfected with pGJA-P/VAX, pGJGLU/VAX and pGJGLU/GFP, of which the concentration was different. The highest concentration of recombinant fusion protein was observed in the supernatants of CHO cells transfected with pGJGLU/VAX.</p><p><b>CONCLUSIONS</b>CTLA-4 targeted fusion protein could be expressed and secreted by eukaryotic cells. The size of antigen may affect the expression level of CTLA-4 targeted anti-caries DNA vaccine.</p>

Analysis on results of endodontic treatment and influencing factors / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To assess the clinical outcome of root canal therapy (RCT) and the various factors that may influence the outcome of RCT.</p><p><b>METHODS</b>A total of 695 teeth from 357 patients were retrospectively studied three years after endodontic treatment. Pre- and intra-operative information was collected from the original patient records. The post-operative sign or symptom, periapical status and coronal restoration integrity were examined 3 years after obturation. Data were subjected to bivariate and multivariate analysis.</p><p><b>RESULTS</b>The cure rate for 695 teeth was 75.1%, 96.0% of which was considered to be functional. The tooth group, pre-operative pulp and periapical status, quality of root filling and integrity of coronal restoration were revealed by means of bivariate analysis to exert a significant influence on treatment outcome. The logistic analysis indicated that the odds for cure in the teeth with pre-operative periapical radiolucency, underfilling and "open" coronal restoration were significantly lower by 2 folds, 3 folds and 1.6 folds than their counterparts, respectively.</p><p><b>CONCLUSIONS</b>The pre-operative periapical status, quality of root filling and the integrity of coronal restoration are main predictors of outcome in RCT.</p>

A study of the physicochemical and biological properties of mutanase from Trichoderma harzianum / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To determine the physicochemical properties of the mutanase of Trichoderma harzianum isolated from China and to study the influence of mutanase on the adherence of oral Streptococci and the structure of oral biofilms.</p><p><b>METHODS</b>Six fungal strains belonging to Trichoderma were tested for mutanase production in the same cultural condition, the strain producing the highest mutanase activity was studied further and the pH and temperature optimum of the enzyme was determined. The RT-PCR method was used to obtain the gene coding for mutanase and the product was cloned to pMD18-T simple vector for sequencing. Inhibition effects of mutanase on the adherence of Streptococcus sobrinus OMZ176, Streptococcus sobrinus 6715, Streptococcus mutans MT8148 were studied by adherence test. The optical sectioning of biofilms with or without mutanase supplementation were analyzed by confocal laser scanning microscopy (CLSM).</p><p><b>RESULTS</b>The highest enzymatic activity was achieved by Trichoderma harzianum Th1, the maximum activity was at pH 5.5 and at 40 degrees C. The nucleotide sequence was 92% homology with that of a known gene coding a mutanase (GenBank accession No. AJ243799). The adherence of Streptococcus sobrinus OMZ176, Streptococcus sobrinus 6715, Streptococcus mutans MT8148 was significantly inhibited by mutanase. Compared with control, the biofilms with mutanase supplementation had lower height and sparser structure.</p><p><b>CONCLUSIONS</b>The mutanase from Trichoderma harzianum Th1 can inhibit the adherence of oral Streptococci and had an influence on the structure of oral biofilms.</p>

Construction of human bone morphogenetic protein-7 gene fluorescent eukaryotic cell expression vector and test of bioactivity in vitro / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To construct fluorescent eukaryotic cell expression vector with human bone morphogenetic protein-7 (hBMP-7) gene and to transfect mouse stromal cell line W-20-17 to detect the bioactivity of pEGFP-hBMP-7 in vitro.</p><p><b>METHODS</b>pEGFP-hBMP-7 plasmid was constructed by subcloning technique and identified by enzyme cutting and electrophoresis. W-20-17 cells were transfected with pEGFP-hBMP-7 by means of lipofectamine-2000 media methods. Transfection efficiency and gene expression were evaluated by fluorescent microscopy. ALP, von Kossa and osteocalcin (OC) were tested to determined the phenotypes of osteoblast.</p><p><b>RESULTS</b>After 48 hours, the gene transfection efficiency was 40%. Based on GFP and immunofluorescence of pEGFP-hBMP-7, there was the expression of aim gene. After gene transfection, there were not significant different of cell morphology feature and cell proliferation. ALP activity, the number of calcium nodules and the expression of OC increased.</p><p><b>CONCLUSIONS</b>pEGFP-hBMP-7 with bioactivity was constructed, which could induce W-20-17 cells to differentiate to osteoblasts.</p>

Comparison of penetration and obturation density using nickel-titanium and stainless-steel spreader in curved canals / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To compare the initial penetration depth of nickel-titanium (NiTi) and stainless-steel (SS) spreader during lateral compaction and the quality of the seal in curved canals.</p><p><b>METHODS</b>Forty extracted mandibular premolars with a single curved canal were divided into two groups: no more than 20 degrees and more than 20 degrees based on degree of curvature. All canals were instrumented using a rotary instrumentation technique. NiTi and SS spreaders were used to obturate the canals containing a master cone while the penetration depths were measured. Horizontal sections were cut in 2 and 4 mm from the apex and photographed under stereomicroscope. The percentage of gutta-percha-filled are (PGP) of cross-sections was measured using an image analysis program.</p><p><b>RESULTS</b>In canals of more than 20 degrees, the penetration depths and PGP of 2 mm from the apex of NiTi spreaders were higher than SS spreader. In canals of no more than 20 degrees, there were no significant difference between them (P > 0.05). At 4 mm from the apex, there was no significant difference between two groups.</p><p><b>CONCLUSION</b>NiTi spreaders has a higher penetrated depth and obturation density than SS spreaders in severed curved canals.</p>