A retrospective study of endodontic microsurgery about 302 patients / 华西口腔医学杂志

OBJECTIVES@#To investigate the outcome of endodontic microsurgery and analyze the potential prognostic factors, and to evaluate the value of surgical classification by Kim and Kratchman.@*METHODS@#Collecting clinical examination and radiographical examination of endodontic microsurgery cases (which were followed up at least 1 year), which were classified according to Kim and Kratchman, and we analyzed the outcome of endodontic microsurgery and its potential prognostic factors.@*RESULTS@#302 patients (400 teeth) who received endodontic microsurgery were included. The one year success rate of endodontic microsurgery was 94.25%. Different classification had significant influences on the outcome of endodontic microsurgery (@*CONCLUSIONS@#Endodontic microsurgery is an effective treatment method for saving affected teeth, and it can get a good result. Tooth position and classification are the potential prognostic factors. The surgical classification of Kim and Kratchman can help to predict the outcome of endodontic microsurgery.

Effects of cement base with different thickness on stress distributions of restored tooth / 医用生物力学

Objective To study the effects of cement base with different thickness on the stress distributions of restored tooth by finite element method. Method A three dimensional finite element model of a restored first mandibular molar with class 1 cavity was developed based on Micro CT. The thicknesses of cement base with light cured glass ionomer (Vitrebond) and self cured calcium hydroxide (Dycal) were chosen as 0.5 mm, 1.0 mm, 1.5 mm and 2.0 mm, respectively. Occlusal load of 250N was applied to compare the peak maximum and minimum principal stresses of the tooth, restoration and cement base in each model. Results With Dycal of 2mm, the peak maximum principal stress of the tooth was higher than its tensile strengths, and the peak maximum/minimum principal stress of the cement base was both higher than its tensile and compressive strength. Moreover, the peak maximum principal stress of the restoration was about 90% closer to its tensile strength with Dycal of 1.5 mm and 2 mm. With Vitrebond, it also showed that the peak maximum principal stress of the tooth, restoration and cement base appeared in the models with cement base of 1.5 mm and 2.0 mm. Conclusions To prevent the failure in restored tooth, it is advised to use thinner cement base, and the thickness of cement base should be considered from 0.5 mm to 1.0 mm in clinic.

Micro-CT evaluation of root canal deviation after preparation / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To establish a new evaluation system of curved root canal deviation by the technique of micro-CT.</p><p><b>METHODS</b>Curved simulated root canals were prepared with ProTaper NiTi-hand files by crown-down technique. After root canals were scanned by micro-CT and analyzed by image processing software, the planar area and centers' transportation of each cross-section were compared to evaluate the prepare effect of ProTaper, and a three-dimensional model about it were established.</p><p><b>RESULTS</b>The same cross-section's area of the root canals which was prepared with ProTaper NiTi-hand files were essentially consistent. With the data analysis of micro-CT, a system of combining planar and three-dimensional index to evaluate the root canal deviation were established. The shapes of root canal before and after prepared with ProTaper showed less deviation, which proved the shaping ability of ProTaper could meet the requirements for clinical use.</p><p><b>CONCLUSION</b>A three-dimensional root canal central axis model is established using micro-CT. It provides a new method to analyze the shaping ability of the instrumentation after root canal preparation. It will give us a more direct view to analyze the situation of the root canal deviation combining the two-dimensional image and the three-dimensional model.</p>

Influence of hand-mixed methods on compressive strength of zinc phosphate dental cement / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To study the influence of hand-mixed methods on the compressive strength of the zinc phosphate dental cement.</p><p><b>METHODS</b>Three skilled nurses used three kinds of common clinical hand-mixed methods (included the unidirectional rotation method, the alternate pro and con bidirectional rotation method and the pulling and pushing with folding method) to mix the zinc phosphate dental cement on the same condition (i.e. same indoor temperature and humidity, the same mixing ratio, mixing time, mixing frequency and the same mixing instruments and so on). The mixed zinc phosphate cement was packed into the plastic cylinders with 10 mm-high and 5 mm-bore. After the mixed zinc phosphate cement coagulated, compressive strength was tested separately.</p><p><b>RESULTS</b>The compressive strength of the zinc phosphate dental cement mixed with the alternate pro and con bidirectional rotation method was the best, and the value was (106.11+/- 4.82) MPa. The compressive strength of the zinc phosphate dental cement mixed with the pulling and pushing with folding method was lower, and the value was (77.57 +/- 6.26) MPa. The compressive strength of the zinc phosphate dental cement mixed with the unidirectional rotation method was the lowest, and the value was (54.41 +/- 5.08) MPa. The compressive strength of the zinc phosphate dental cement mixed with the unidirectional rotation method and the pulling and pushing with folding method could not achieve the clinical required compressive strength (about 100 MPa), while the compressive strength mixed with the alternate pro and con bidirectional rotation method was above 100 MPa.</p><p><b>CONCLUSION</b>The alternate pro and con bidirectional rotation method to mix the zinc phosphate dental cement is recommended in clinic.</p>

Differential analyses of mRNA expression of gtfs from Streptococcus mutans in different pH condition / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To determine the expression level of each gtf under different pH cultural conditions and to find the relationship between gtf expression levels with environmental pH in different strains of Streptococcus mutans (S.mutans).</p><p><b>METHODS</b>S. mutans form clinical isolation with different extracellular polysaccharides (EPS) producibility and UA159 were selected. Their ability to produce EPS under pH5.5 and pH7 were tested. Then in two strains, the relative quantity of gtfA, gtfB, gtfC, gtfD's mRNA which were related to S. mutan's ability to produce EPC, were examined by real-time reverse transcription-polymerase chain reaction (real-time RT-PCR) methods under different pH culture condition.</p><p><b>RESULTS</b>At pH5.5, expression levels of gtfA, gtfB, gtfD were increased while that of gtfC were decreased in both strains, and that of gtfB, gtfC were higher in strain which produces more ECP.</p><p><b>CONCLUSION</b>The expression levels of gtfs related closely to the cariogenicity of S. mutan.</p>

Three-dimensional finite analysis of the stress in first mandibular molar with composite class I restoration when various mixing ratios of bases were used / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To analyze the possible damage to the remaining tooth and composite restorations when various mixing ratios of bases were used.</p><p><b>METHODS</b>Testing elastic modulus and poission's ratio of glass-ionomer Vitrebond and self-cured calcium hydroxide Dycal with mixing ratios of 1:1, 3:4, 4:3. Micro-CT was used to scan the first mandibular molar, and the three-dimensional finite element model of the first permanent mandibular molar with class I cavity was established. Analyzing the stress of tooth structure, composite and base cement under physical load when different mixing ratios of base cement were used.</p><p><b>RESULTS</b>The elastic modulus of base cement in various mixing ratios was different, which had the statistic significance. The magnitude and location of stress in restored tooth made no differences when the mixing ratios of Vitrebond and Dycal were changed. The peak stress and spreading area in the model with Dycal was more than that with Vitrebond.</p><p><b>CONCLUSION</b>Changing the best mixing ratio of base cement can partially influence the mechanistic character, but make no differences on the magnitude and location of stress in restored tooth. During the treatment of deep caries, the base cement of the elastic modulus which is proximal to the dentin and restoration should be chosen to avoid the fracture of tooth or restoration.</p>

Study on the effect of concentrations of glucose on initial adherence of Streptococcus mutans / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To study the effect of concentrations of glucose on the initial adherence of Streptococcus mutans (S. mutans) to saliva-coated hydroxyapatite (SHA), and to compare the initial adherence of S. mutans from caries-active group with that of S. mutans from caries-free group.</p><p><b>METHODS</b>Each 10 clinical isolates of S. mutans from caries-active and caries-free subjects were used in this study. And S. mutans UA159 was also included in this experiment. SHA was used to simulate tooth surface in oral cavity. S. mutans clinical isolates and strain UA159 were cultured in TPY liquid medium containing 3H-TdR in the same radioactive concentration and glucose in 0.2%, 1.0%, 5.0% concentration. Then grown cells were harvested to produce a suspension. SHA and radiolabelled bacterial suspension (A550(nm) = 0.52) were mixed for 90 minutes, samples were assayed by using liquid scintillation counter, and binding abilities of strains were evaluated by the count per minute (CPM).</p><p><b>RESULTS</b>The initial adherence ability of S. mutans from caries-active group was higher than that of S. mutans from caries-free group (P < 0.05). And the initial adherence ability of S. mutans cultured in different concentration of glucose was also significantly different (P < 0.05), 5.0% glucose group had the highest adherence ability, and 0.2% glucose group had the lowest adherenceability.</p><p><b>CONCLUSION</b>(1)Difference of the initial adherence of S. mutans might relate to difference of carious experiences; (2) Glucose may play an important role in S. mutans initial adherence, to some extent, S. mutans cultured in the higher concentration of glucose has the higher initial adherence property.</p>

Histological evaluation of direct pulp capping with a self-etching adhesive and calcium hydroxide / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the beagles' pulp response following direct pulp capping with Clearfil SE BOND (SB).</p><p><b>METHODS</b>130 sound teeth were used. 120 had their pulps mechanically exposed and were divided in two groups. In group A, teeth were capped with SB. In group B, teeth were capped with calcium hydroxide (CH). The left 10 teeth were used as control. After 7, 30 and 90 days, the teeth were extracted and processed for light microscopical examination.</p><p><b>RESULTS</b>In 7 day observation period, inflammatory reaction in SB group was slighter than that of CH group, but the difference was statistical insignificant. In the 30 day and 90 day observation period, inflammatory reaction was slight in both groups, but specimens with dentin bridge formation was significantly less in SB group than in CH group (P < 0.05).</p><p><b>CONCLUSION</b>SB showed acceptable biocompatibility with pulp, but its ability to induce hard tissue barrier on pulp exposure is weaker than CH.</p>

Clinical analysis of 1 423 cases of root canal therapy / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the clinical quality of root canal therapy (RCT) in West China Dental Hospital of Sichuan University.</p><p><b>METHODS</b>1 423 RCT teeth were finished from Mar. 2001 to Feb. 2002 in West China Dental Hospital. Root canal filling quality and treatment period of these teeth were evaluated. 695 teeth of the total were revisited 2 years later and 2-year success rate were evaluated.</p><p><b>RESULTS</b>The ratios of adequate filling, underfilling, and overfilling were 79.97%, 14.62% and 5.41%, receptively. Full canal RCT ratio of molar was 89.44%. Average RCT treatment period was 2.8 weeks. 2-year success rate of RCT was 94.39%.</p><p><b>CONCLUSION</b>Clinical RCT level of West China Dental Hospital was satisfactory from 2001 to 2002.</p>

Role of heat shock protein 70 expression in DNA damage induced by benzo(a)pyrene / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To explore heat shock protein 70 (HSP70) expression of A549 cells and its role in DNA damage caused by benzo(a)pyrene (BaP).</p><p><b>METHODS</b>Human adenocarcinoma A549 cells were cultured in vitro, exposed by different concentrations of BaP (0, 1.25, 2.50, 5.00, 10.00 micro mol/L) for 6 hours, or 10 micro mol/L of BaP for different time (0, 4, 8, 12, 16, 24 and 48 h). Then HSP70 expression and DNA damage were detected using Western-blot and single cell gel electrophoresis (SCGE) assay respectively, and the relationship between HSP70 expression and DNA damage was further analyzed.</p><p><b>RESULTS</b>The integral optical densities of HSP70 in A549 cells treated with 1.25, 2.50, 5.00 and 10.00 micro mol/L BaP for 6 h (49.63 +/- 1.30, 45.72 +/- 1.03, 40.53 +/- 0.95, 37.50 +/- 1.20 respectively) were lower than that of the control cells (59.43 +/- 1.17) (P < 0.05). When A549 cells were exposed to 10 micro mol/L BaP for 4, 8, 12, 16 h, the integral optical densities of HSP70 were 33.33 +/- 0.80, 29.23 +/- 0.91, 12.51 +/- 0.96, 9.50 +/- 1.25 respectively, and there was an increasing tendency of the expression of HSP70 for 24 - 48 h (20.06 +/- 1.38, 24.51 +/- 1.39), however, all were different from that in control group (56.59 +/- 0.85) (P < 0.05). DNA damage scores in 10(6) A549 cells treated with 2.50, 5.00 and 10.00 micro mol/L BaP for 6 h (23,718 +/- 2,938, 30,128 +/- 2,937, 44,231 +/- 3,846) were significantly higher than that of the control cell (9,615 +/- 1,923) (P < 0.05). When A549 cells were exposed to 10 micro mol/L BaP for 4, 8, 12, 16, 24, 48 h, DNA damage scores (16,667 +/- 4,003, 38,461 +/- 1,924, 5,615 +/- 3,847, 76,282 +/- 2,937, 7,513 +/- 1,110 and 58,975 +/- 9,487) were also higher than that of control group (P < 0.05). There was a negative correlation between DNA damage and the expression of HSP70 when A549 cells were exposed to different concentrations of BaP.</p><p><b>CONCLUSION</b>HSP70 might enhance intracellular defenses against DNA damage induced by BaP.</p>

Effects of mitogen activated protein kinase signal transduction pathways on heat shock protein 70 gene expression in endothelial cells exposed to benzo(a)pryene / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To investigate the effects of mitogen activated protein kinase (MAPK) signal transduction pathways on heat shock protein 70 (HSP70) gene expression in endothelial cells exposed to benzo(a)pryene (BaP).</p><p><b>METHODS</b>Porcine aortic endothelial cells were pre-treated or by PD98059 (10 micro mol/L) or SB203580 (20 micro mol/L) for 1 hour, then treated with different concentrations of BaP (0, 0.1, 0.5, 1.0, 5.0 and 10.0 micro mol/L) for 24 hours respectively;Expression levels of three phosphorylated MAPKs [extracellular signal regulated protein kinase (ERK), c-Jun amino-terminal kinase (JNK), and p38] and HSP70 were determined by Western-blot.</p><p><b>RESULTS</b>The three phosphorylated MAPKs expressional levels especially p-ERK1 had different extents of changes with dose-response relationship under BaP exposure. BaP inhibited the expression of HSP70, which significantly decreased in medium and high dose group (>or= 1.0 micro mol/L) but did not decrease in control group (P < 0.05). Although the inhibitor of ERK (PD98059) could partly weaken the inhibited effects of BaP on HSP70 expression, HSP70 expression levels of endothelial cells pre-treated with PD98059 were still significantly lower than that of control cells (P < 0.05).</p><p><b>CONCLUSION</b>ERK1 pathway might play some roles in HSP70 gene expression in endothelial cells exposed to BaP, and other unknown signal pathways might also have some effects on this process.</p>

Initial clinic research on curved canal preparation by reverse flaring technique / 华西口腔医学杂志

<p><b>OBJECTIVE</b>Curved canal preparation is much difficult in root canal therapy(RCT). Step back technique and routine technique are still regular methods in curved canal preparation. The purpose of this study was to introduce a new method reverse flaring technique, and to investigate its preparation efficiency in intermediate-curvature canals.</p><p><b>METHODS</b>48 cases of lower first molars RCT were collected, which were first treated because of pulpitis or apical periodontitis in West China College of Stomatology, Sichuan University from Nov. 2001 to Aug. 2003, mesial canal curvature was intermediate (30 degrees-60 degrees), determined by Schineider method. Cases were divided into two groups, in reverse flaring technique group, canal preparation in 27 cases were finished by reverse flaring technique, 21 cases by step back technique as control. In working length determination and fitting master cone stages, cases in two groups which fit full working length were recorded, determined by radiograph, and analyzed by chi 2 test.</p><p><b>RESULTS</b>In working length determination stage, cases which fit full working length in reverse flaring technique group were significantly more than that of step back technique group (P < 0.05), in fitting master cone stage, cases which fit full working length in reverse flaring technique group were also significantly more than that of step back technique group(P < 0.05).</p><p><b>CONCLUSION</b>In working length determination stage, cases which fit full working length in reverse flaring technique group were significantly more than that of step back technique group (P < 0.05), in fitting master cone stage, cases which fit full working length in reverse flaring technique group were also significantly more than that of step back technique group(P < 0.05).</p>

Expression of the heat-shock protein 70 family polymorphism in A549 cell line exposed to benzo(a)pyrene / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To study the pattern of polymorphism expression of heat-shock protein 70 (HSP70) family in A549 cell line treated with different concentrations of benzo(a)pyrene (BaP) and its probable biological effect.</p><p><b>METHOD</b>Two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) was used for the HSP70 expression analysis.</p><p><b>RESULTS</b>2D-PAGE showed that when A549 cells were exposed to different concentrations of BaP (0.1, 1.0, 5.0, 10.0 micromol/L) for 24, 48 h respectively, the HSP72 in A549 gradually declined as BaP concentrations increased [the integral OD (IOD)] for 24 h were: 150.36 +/- 26.03, 98.57 +/- 13.34, 64.92 +/- 15.03, 34.65 +/- 19.10, 32.92 +/- 18.71 respectively, for 48 h: 126.85 +/- 17.41, 106.19 +/- 15.32, 73.64 +/- 21.02, 35.18 +/- 11.95, 16.27 +/- 9.35 respectively), while the IOD of HSP73 did not show any remarkable change (24 h: 102.29 +/- 21.24, 87.71 +/- 18.70, 71.19 +/- 14.08, 71.87 +/- 15.16, 72.78 +/- 17.31 respectively; 48 h: 86.66 +/- 16.86, 75.67 +/- 10.61, 66.83 +/- 12.63, 67.29 +/- 10.26, 91.37 +/- 13.68 respectively).</p><p><b>CONCLUSION</b>BaP can inhibit HSP72 expression and with certain dose-effect relationship, but cannot affect HSP73 expression.</p>

The expression of cytochrome P450 1A1 of endothelial cells induced by benzo(a)pyrene / 中华劳动卫生职业病杂志

<p><b>OBJECTIVE</b>To explore the effect of benzo(a)pyrene (BaP) on the expression and the activities of cytochrome P450 1A1 (CYP1A1) of porcine aortic endothelial cells.</p><p><b>METHODS</b>Porcine aortic endothelial cells were cultured in vitro, and treated with different concentrations of BaP (0, 0.5, 1.0, 5.0, 10.0 micro mol/L) for 24 hours, CYP1A1 expression was determined by Western blot and immunohistochemistry. At the same time, the ethoxyresorufin-o-deethylase (EROD) activities were measured by spectrofluorometer.</p><p><b>RESULTS</b>By Western blot, the expression of CYP1A1 of control cells was not found, but the expression of CYP1A1 of cells treated with BaP was found; By immunohistochemistry, only part of endothelial cells treated with BaP had positive expression of CYP1A1. The peak activities of EROD induced by BaP was at the concentration of 0.5 - 1.0 micro mol/L.</p><p><b>CONCLUSION</b>BaP could induce part of endothelial cells to synthesize CYP1A1. BaP of 0.5 - 1.0 micro mol/L could induce peak activities of EROD.</p>