Effect of straight-line minimally invasive access cavity on the mechanical properties of maxillary first premolars: a finite element analysis / 中华口腔医学杂志

Objective: To investigate the effects of straight-line minimally invasive access cavity on the mechanical properties of endodontically treated maxillary first premolars using finite element analysis. Methods: Micro-CT data of twenty maxillary first premolars were collected for three-dimensional reconstruction. Three access cavities, including the conventional access cavity (ConvAC), the truss access cavity (TrussAC) and the straight-line minimally invasive access cavity (SMIAC), as well as the root canal treatment procedure, were simulated in all the 20 reconstruction samples of three-dimensional models, respectively. The peak von Mises stress on the cervical area of each model, as well as the stress distribution under vertical and oblique loading circumstances, were subsequently determined by using finite element analysis. Results: In comparison to the stresses of ConvAC [buccal cervical (BC): (188.7±13.4) MPa, palatal cervical (PC): (200.9±25.7) MPa], the stresses of TrussAC [BC: (146.0±12.9) MPa, PC: (167.6±15.9) MPa] (t=9.01, P<0.001; t=4.59, P<0.001) and SMIAC [BC: (142.6±13.7) MPa, PC: (168.1±17.4) MPa] (t=9.64, P<0.001; t=3.76, P=0.004) significantly reduced the peak von Mises stress on the cervical area of the maxillary first premolars after root canal treatment. Under vertical loading conditions, SMIAC also reduced the central tendency of stresses on the occlusal surface, cervical area and root. In the case of oblique loading conditions, similar results were observed. Under both loading conditions, there was no significant difference in the peak von Mises stress on the cervical area of the maxillary first premolar between TrussAC and SMIAC groups. Conclusions: The design of SMIAC could preserve the mechanical properties of the maxillary first premolar following root canal treatment, which might have certain clinical feasibility.

Vital pulp preservation treatment in mandibular right first molar with vertical root fractures: a case report / 华西口腔医学杂志

This case presents vertical root fracture with vital pulp in mandibular right first molar. Examinations of the history, clinical tests, laser Doppler flowmetry, and radiographs revealed that the tooth showed positive response to electric pulp testing and was normal compared with the healthy control tooth. This study aimed to use a novel vital preserving surgical technique (microapical surgery and nanometer bioactive materials) to make an effective therapeutic decision for the vital tooth with vertical root fracture.

Endodontic infection management in root canal preparation: question and solution / 华西口腔医学杂志

The essence of pulp and periapical disease is bacterial infection. Thus, satisfactory infection control is the premise and foundation of healing, in which root canal preparation is a critical procedure. Root canal system anatomy, infection degree, physical cutting during root canal preparation, and certain cleaning measures affect the quality of infection control. Appropriate evaluation of the grades of infected root canals before treatment is necessary because different grades of root canal infection demand various disinfection schedules to facilitate tissue healing and guarantee the long-term success rate of endodontic treatment.

Bone morphogenetic protein 2-induced human dental pulp cell differentiation involves p38 mitogen-activated protein kinase-activated canonical WNT pathway / 国际口腔科学杂志·英文版

Both bone morphogenetic protein 2 (BMP2) and the wingless-type MMTV integration site (WNT)/β-catenin signalling pathway play important roles in odontoblast differentiation and dentinogenesis. Cross-talk between BMP2 and WNT/β-catenin in osteoblast differentiation and bone formation has been identified. However, the roles and mechanisms of the canonical WNT pathway in the regulation of BMP2 in dental pulp injury and repair remain largely unknown. Here, we demonstrate that BMP2 promotes the differentiation of human dental pulp cells (HDPCs) by activating WNT/β-catenin signalling, which is further mediated by p38 mitogen-activated protein kinase (MAPK) in vitro. BMP2 stimulation upregulated the expression of β-catenin in HDPCs, which was abolished by SB203580 but not by Noggin or LDN193189. Furthermore, BMP2 enhanced cell differentiation, which was not fully inhibited by Noggin or LDN193189. Instead, SB203580 partially blocked BMP2-induced β-catenin expression and cell differentiation. Taken together, these data suggest a possible mechanism by which the elevation of β-catenin resulting from BMP2 stimulation is mediated by the p38 MAPK pathway, which sheds light on the molecular mechanisms of BMP2-mediated pulp reparative dentin formation.

Maxillary second molar with curved single root and single canal: a case report / 华西口腔医学杂志

Incidence rate of single root canal in maxillary second molar is very low. The emergence of curved single root canal in maxillary second molar with single root is especially rare. A case of curved single root canal in maxillary second molar with single root was successfully treated and reported in this article. This report also highlighted the role of cone beam computed tomography as an objective method to confirm the three-dimensional anatomy of teeth.

Tooth anatomy risk factors influencing root canal working length accessibility / 国际口腔科学杂志·英文版

The aim of this study was to analyze the specific influence of root canal anatomy on the accessibility of working length during root canal therapy. Four hundred seventy-six root canal therapy cases (amounting to a total of 1 005 root canals) were examined. The anatomy risk factors assessed in each case included: tooth type (tooth location), root canal curvature, and root canal calcification, as well as endodontic retreatment. The investigation examined the correlation between each of these anatomic factors and the working length, with statistical analysis consisting of Chi-square tests and multiple logistic regression analysis. In an independent factor analysis, tooth type (tooth location), root canal curvature, canal calcification, and endodontic retreatment were determined to be the primary risk factors. In a multiple-factor regression model, root curvature and canal calcification were found to most significantly influence root canal working length accessibility (P<0.05). Root canal anatomy increases the difficulty of root canal preparation. Appropriate consideration of tooth anatomy will assist in accurate determination of preparation difficulty before instrumentation. This study alerts clinical therapists to anatomical factors influencing the working length accessibility, and allows for a direct estimate of success rate given in situ measurements of tooth factors during the root canal treatment procedure.

Isolation and identification of side population cells in human lung adenocarcinoma cell line A549 / 中华肿瘤杂志

<p><b>OBJECTIVE</b>To isolate and characterize the side population cells (SP cells) in the lung adenocarcinomas cell line A549.</p><p><b>METHODS</b>The protein expression of ABCG2 in human lung adenocarcinoma cell line A549 was detected by immunohistochemistry. SP and NSP cells in the cell line A549 were isolated by FACS, and their differentiation was analysed. ABCG2 expression in the two cell subsets was detected by RT-PCR. The cell growth curves, cell division indexes, cell cycles, plate clone formation tests, migration and invasion assays, chemotherapeutic susceptibility tests, tests of the intracellular drug levels, and the tumor cell implantation experiments on nude mice were applied to study the biological properties of the two cell subsets. The expression of ABCG2 in the transplanted tumor in nude mice was detected by immunohistochemistry and RT-PCR.</p><p><b>RESULTS</b>The positive rate of ABCG2 expression in the A549 cells by immunohistochemistry was 2.13%. SP and NSP cells were isolated by FACS. The SP cells could produce both SP and NSP cells, while NSP cells only produced NSP cells. SP cells expressed ABCG2, but NSP cells did not. The proliferation and migration abilities of the two cell subsets were similar, but the invasion and tumorigenic ability of SP cells was significantly higher than that of NSP cells. The susceptibilities to DDP and its intracellular levels of the two cell subsets were similar, but the susceptibilities to 5-FU, VP16, NVB and GEM and their intracellular levels of NSP cells were significantly higher than those of the SP cells.</p><p><b>CONCLUSIONS</b>SP cells in the human lung adenocarcinomas cell line A549 is enriched with tumor stem cells. An effective way to get lung adenocarcinomas stem cells is to isolate SP cells by FACS.</p>

The clinical analysis on the effects of different difficulty in root canal preparation / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the effects of root canal preparation treated by endodontists of different levels in different difficulty associated with the root canal anatomy factors.</p><p><b>METHODS</b>Totally 422 teeth with 901 root canals were randomly selected from the Conservative Dentistry Department, West China Stomatology Hospital, and these teeth were respectively treated by junior specialist postgraduates, senior specialist postgraduates and endodontic specialists. Grading criteria of root canal risk factor and root canal therapy difficulty assessment were found based on 6 items: Tooth type, working length, root curvature, calcification, number of canals, and the previous endodontic treatment. The effects of root canal preparation with different difficulty in different groups were analyzed with RxC Chi-square test.</p><p><b>RESULTS</b>Success rates of root canal preparation in junior group and senior group during three difficulty groups were statistically different (P < 0.05), and the root canal therapy difficulty group I > group II > group III. The operator factors in root canal therapy difficulty group I and group II were not significantly different P > 0.05). But in root canal therapy difficulty group III, the endodontic specialist group have highest success rate in root canal preparation.</p><p><b>CONCLUSION</b>The cases of root canal treatment should be treated by endodontist of corresponding level according to the difficulty. In difficult cases, endodontic specialist can provide better root canal preparation result.</p>

Strategies of endodontic infection control / 华西口腔医学杂志

Microbe infection is not only the key pathogenic factor of primary endodontic infectious diseases, but also the arch-crimina of endodontic treatment fail. Therefore, the endodontic treatment success is based on the debridement of infectious root canal, elimination of bacteria, and the prevention of endodontic reinfection. It is beset with difficulties to control the endodontic infection in clinic because of the bacterial variety, anatomic complexity of root canal, and limitation of the root canal therapeutic methods. In order to get the ideal prognosis of the root canal treatment, in the procedure of the therapy, it should be the tight isolation of tooth, reasonable choose of the root canal preparation technique, rational use of root canal preparation instrument, effective irrigation of root canal, proper root canal dressing, and the 3-dimensional obturation of root canal.

Anatomic study of canal isthmuses of mandibular permanent incisors by micro-CT / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the anatomic feature of the canal isthmus of mandibular permanent incisors by Micro-CT.</p><p><b>METHODS</b>Thirty-three mandibular permanent incisors with two canals were selected through the radiograph in proximal view. These teeth were then scanned using Micro-CT and reconstructed. The scanning layer thickness was 20 microm. We observed the apical 6 mm of the 33 roots, and 300 sections were gained each tooth, giving a total of 9900 sections. The numbers of canals at each level in the apical 6 mm were recorded. The numbers of sections showing isthmuses at each level of the root canals were recorded too. Data were analyzed using the Chi-square statistic to test the null hypothesis that location of the sections in each of the apical 6 mm and presence of the isthmus were independent. The minimum root canal wall thickness was measured in each of the apical 6 mm of the roots.</p><p><b>RESULTS</b>Isthmuses were found to be present at all levels with prevalence from 10.0% to 85.5%. The Chi-square test indicated a significant difference in the distribution of isthmuses with section (P = 0.0O1). The incidence of isthmuses was higher at the apical 3-6 mm level, and the highest incidence (85.5%) was at 5 mm level. There were many more sections containing complete isthmuses (49.7%) than those containing partial isthmuses (4.5%). The thickness of the minimum root canal was less than 0.5 mm.</p><p><b>CONCLUSION</b>The mandibular incisors have a high incidence of isthmus and are narrow in proximal direction. Debridement of the isthmus is a major challenge during surgical and nonsurgical root canal treatment.</p>

The antibacterial efficacy of KaVo KEY laser on Enterococcus faecalis within infected root canals and roots surface in vitro / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the antibacterial efficacy of KaVo KEY laser on Enterococcus faecalis (E. faecalis) within infected root canals and roots surface in vitro.</p><p><b>METHODS</b>Fifty single-rooted teeth were selected, and infected root canals and roots surface vitro models were prepared. Then, these specimens were divided into three groups. First group were untreated as blank control. The other two groups were the laser groups: Irradiated 15 s and 30 s respectively with 80 mJ and 140 mJ in root canals and on roots surface. Microbiological samples were collected from root canals and roots surface at two time points (before irrigation and immediately after irrigation). The dentin chips from three different zone of part of root canals in each group were immediately collected and were cultured for 24 h in brain heart infusion (BHI).</p><p><b>RESULTS</b>The number of E. faecalis in root canal and root surface in each of the groups were effectively reduced (P < 0.05), and there was no significant difference between each two groups (P > 0.05). Compared with the blank control, the bacterial number in 100 microm of dental tubules decreased after specimens treated with 80 mJ, and the experimental group irradiated 15 s was a significant decease (P < 0.05). The other groups were no changed in different zone of dental tubules.</p><p><b>CONCLUSION</b>KaVo KEY laser is effective on sterilizing infected root canals and roots surface. It has also significant effect on bacterial in superficial dental tubules with low energy and short time.</p>

Porphyromonas gingivalis induced interleukin-6 expression by Nod/Rip2-mediated signaling pathway / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate into the signaling pathway of Porphyromonas gingivalis (P. gingivalis) on cytokine expression in human dental pulp cells (HDPC).</p><p><b>METHODS</b>Anaerobic method was employed to culture P. gingivalis, and then HDPC were intracellularly infected by P. gingivalis. The extraction of total RNA, real-time quantitative polymerase chain reaction (qPCR) and enzyme linked immunosorbent assay (ELISA) was used for mRNA expression of Nods and Rip2, protein secretion of interleukin-6 (IL-6).</p><p><b>RESULTS</b>HDPC expressed Nods, Rip2 mRNA and IL-6. The up-regulation of Nods and Rip2 mRNA started after P. gingivalis infection, reached maximal level at 2 h, and then decreased at 6 h; whereas elevated IL-6 was found when P. gingivalis infected.</p><p><b>CONCLUSION</b>P. gingivalis activate host innate immune responses in HDPC, and induce IL-6 production through Nod/Rip2-mediated signaling pathway.</p>

Shaping ability of two nickel-titanium rotary systems in simulated S-shaped canals / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the shaping ability of two nickel-titanium rotary systems (ProTaper and Hero642) in simulated S-shaped canals.</p><p><b>METHODS</b>Thirty simulated S-shaped canals were randomly divided into three groups and prepared by ProTaper, Hero642, ProTaper combined with Hero642 respectively. All the canals were scanned before and after instrumentation, and the amount of material removed in the inner and outer wall and the canal width after instrumentation were measured with a computer image analysis program.</p><p><b>RESULTS</b>There was significant difference in the amount of material removed at the inner side of apical curvature and outer side of apex between ProTaper combined with Hero642 and ProTaper files (P < 0.05) at the same tip size. The inner and outer wall of the canals were evenly prepared by ProTaper combined with Hero642, and the taper of canals were better than those prepared by Hero642.</p><p><b>CONCLUSIONS</b>ProTaper combined with Hero 642 had better shaping ability to maintain the original shape and could create good taper canals in the simulated S-shaped canal model.</p>

Establishment of a model of intracellular infection on human dental pulp fibroblast by Porphyromonas gingivalisin vitro / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To establish a model of intracellular infection of human dental pulp fibroblast (HDPF) by Porphyromonas gingivalis in vitro.</p><p><b>METHODS</b>HDPF was incubated with live Porphyromonas gingivalis with a multiplicitas of infection (MOI) from 100 for 0.5, 1.0, 2.0 hours. HDPF infected with live Porphyromonas gingivalis were observed by inverted microscope. Metronidazole, Penicillin, Streptomycin were added to the medium to kill any extracellular bacteria. Then the cells were lysed by sterile distilled water, dilutions of the lysates of cells were cultured anaerobically. Colony of invasive bacteria were then observed. HDPF exposed live Porphyromonas gingivalis with a MOI 50 and 100 for 1.0 hour, then cells survival rate were detected by MTT assay.</p><p><b>RESULTS</b>After infected with Porphyromonas gingivalis 2.0 hours, cells were eumorphism. Porphyromonas gingivalis of incubation for 1.0, 2.0 hours was invasive cells. MTT assays indicated 99.07% cells survival rate with a MOI from 50 and 74.43% cells survival rate with a MOI from 100.</p><p><b>CONCLUSION</b>A model of HDPF intracellular infection with Porphyromonas gingivalis was successfully established in vitro.</p>

Root canal curvature in chinese mandibular permanent incisors / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the root canal curvature in Chinese mandibular permanent incisors.</p><p><b>METHODS</b>Two hundred and ninety nine Chinese mandibular permanent incisors were included in this study. The root canals were inserted with stainless steel 15# K files, and then taken radiography from the facial and proximal view by X-ray paralleling technique. Canal curvatures were evaluated by measuring the angle, the radius of the curvatures, and the length of the curved part of the canal. Based on the curved angle and the shape of curved canals, the root canals were classified.</p><p><b>RESULTS</b>The curved angle, radius, and the curved canal length was 5.28 degrees +/- 5.52 degrees, 16.19 mm +/- 12.38 mm, 4.10 mm+/-2.01 mm, respectively in the facial view; 9.99 degrees +/- 5.84 degrees, 18.86 mm +/- 9.71 mm, 3.27 mm +/- 2.39 mm, respectively in the proximal view. The prevalence of straight, light, moderate, and serve curved root canals in mandibular permanent incisors was 15.7%, 66.9%, 16.7%, and 0.7%, respectively (P<0.05) based on the curved angle. The prevalence of straight, L shape, and S shape curved root canals was 7.7%, 50.5%, and 41.8%, respectively (P < 0.05).</p><p><b>CONCLUSION</b>Most of the root canals in mandibular permanent incisors are curve.</p>

Shaping ability of multi-taper nickel-titanium files in simulated resin curved root canal / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To compare the shaping ability of ISO standard stainless steel K files and multi-taper ProTaper nickel-titanium files in simulated resin curved root canals. METHODS Thirty simulated resin root canals were randomly divided into three groups and prepared by stainless steel K files, hand ProTaper, rotary ProTaper, respectively. The amount of material removed from inner and outer wall and canal width after canal preparation was measured, while the canal curvature before and after canal preparation and canals aberrations were recorded.</p><p><b>RESULTS</b>The stainless steel K files removed more material than hand ProTaper and rotary ProTaper at the outer side of apex and inner side of curvature (P < 0.05). The mean degree of straightening in stainless steel K files group was significantly bigger than in ProTaper group (P < 0.05). The canals prepared by ProTaper had no evident aberration.</p><p><b>CONCLUSION</b>The shaping ability of ProTaper is better than stainless steel K files.</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>

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>

Anesthetic efficacy of 2% mepivacaine in conservative dentistry / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To determine the efficacy of 2% mepivacaine in conservative dentistry.</p><p><b>METHODS</b>The patients who needed cavity preparation or access to pulp chamber received local infiltration with 2% mepivacaine. Anesthesia time, anesthetic efficacy and cardiovascular system influences were assessed. 3% lidocaine with epinephrine served as control.</p><p><b>RESULTS</b>In experiment group, the anesthesia effects were quicker and anesthesia duration was longer than that in control group. Doctors highly appreciated the anesthetic efficacy. Two groups did not show any evident change in blood pressure and heart rate.</p><p><b>CONCLUSION</b>2% mepivacaine is a safe and efficacious local anesthetic drug in conservative dentistry.</p>

Separation of Bacteroides forsythus ATCC43037 proteins by horizontal two-dimensional gel electrophoresis / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To set up a rapid, efficient, reliable and accurate method for separation of Bacteriodes forsythus proteins.</p><p><b>METHODS</b>Bacteroides forsythus ATCC43037 cells were harvested by centrifugation, washed in Tris buffer to remove excess medium, and lysed by sonication. The sonicated lysis proteins were extracted step by step with ReadyPrep Sequential Extraction Kit (Bio-Rad). The supernatant of B. forsythus proteins were used for two-dimensional gel electrophoresis. The first dimension IEF (isoelectric focusing) was run with Immobiline DryStrip (pH 3-10) and the second dimension SDS-PAGE was run with Excelgel SDS, gradient 8-18 precast gel and buffer strips. The separated proteins were stained with Coomassie Brilliant Blue and silver staining kit (Plusone Silver Staining Kit, Protein, Pharmacia Biotech).</p><p><b>RESULTS</b>1. The protein spots were clear when sample cups were used in the middle of IPG strip during IEF. 2. B. forsythus proteins were separated clearly by horizontal two-dimensional electrophoresis and most of B. forsythus whole-cell proteins were acidic proteins (P13-7).</p><p><b>CONCLUSION</b>Horizontal two-dimension electrophoresis is a useful method for separating B. forsythus proteins.</p>