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Objective@#To analyze effect of fractured file removal from the middle third root canal on root fracture resistance using finite element analysis, which provides a theoretical basis for clinical prognosis evaluation.@*Methods@#Two finite-element models were established, the fractured file removal model (fractured file located in the middle third of root canals, followed by ultrasonic file removal and root canal preparation) and the control model (root canal preparation only), and compressive displacement dependencies on compressive force was computed and compared with experimental data for validation. The validated finite-element models were used to analyze the stress distribution differences during the initiation, propagation and completion of the crack between fractured file removal specimen and control one.@*Results@#The critical breaking force of the fractured file removal specimen was 406 N, and the finite element simulation result was 396 N. The critical breaking force of the control specimen was 502 N, and the finite element simulation result was 483 N. The position of crack initiation in the finite element simulation was basically consistent with that in the experiment. The experimental data of compressive test and the results of finite-element computation were in agreement, thus validating the finite-element model. In the process of continuous pressure, the stress distribution of the control root is relatively uniform, and the location of crack initiation and the direction of propagation have a certain unpredictability. Compared with the control root, the stress concentration on the root with fracture file removal was obvious, especially on edges, and the number of cracks are much more. Because of the thinner radicular wall, the crack propagation rate is faster too. Therefore, the overall root fracture resistant is decreased obviously.@*Conclusions@#During the fractured file removal procedure, amount of dentine removed should be minimized, and the edges and corners which caused by fractured file removal should be shaped to smooth in order to reduce the stress concentration and prevent the root from fracture.
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Objective@#To investigate the effect of PR domain zinc finger protein 9 (PRDM9), one of the histone methylated transferases, on osteogenic differentiation ability of periodontal ligament mesenchymal stem cells (PDLSC).@*Methods@#PDLSC with PRDM9 gene knocked down by PRDM9 shRNA using recombinant lentiviral vector were allocated into the PRDM9sh group, and the transfected shRNA was as the control group. The gene expression efficiency was evaluated by reverse transcription polymerase chain reaction (RT-PCR). Alkaline phosphatase activity (ALP), alizarin red staining, mineralization and osteocalcin, which belongs to osteogenic differentiation markers detected by RT-PCR and Western blotting to detect the osteogenic differentiation ability of stem cells from periodontal ligaments in vitro. In vivo, PRDM9sh and control group cells was transplanted into the dorsal dermal to explore the osteogenesis. The area percentage of new osteogenic tissue was calculated by image pro software and statistically analyzed.@*Results@#RT-PCR results showed that the relative expression of PRDM9 gene in PRDM9sh (0.460±0.017) was significantly lower than that in control group (1.000±0.107) (P<0.05). The results of ALP activity determined at 5 days postinduction in a significant decrease in PRDM9sh cells (0.762±0.063) compared with control group (1.225±0.058) (P<0.01). Alizarin red staining induced by osteogenesis at 2 weeks and 3 weeks showed that the staining of PRDM9sh was significantly lighter than that in control group. Quantitative calcium analysis results showed that the calcium ion concentration induced by osteogenesis at 2 weeks and 3 weeks [(0.071±0.004), (0.075±0.001)] in PRDM9sh was significantly lower than that in control group at 2 weeks and 3 weeks [(0.282±0.006), (0.485+0.004)] (P<0.01). RT-PCR results showed that the relative expression of osteocalcin mRNA in PRDM9sh (1.059±0.148) was significantly lower than that in control group at 2 weeks (2.542±0.190) (P<0.01). Western blotting results showed that osteocalcin expression in PRDM9sh was significantly lower than that in control group at 1 and 2 weeks after osteogenesis induction. Animal transplantation experiments results indicated that PRDM9 significantly inhibited the osteogenesis of PDLSC in vivo, and the proportion of osteogenic area calculated showed that the osteogenic capacity of PRDM9sh [(3.8±2.41)%] was significantly lower than that in control group [(24.54±7.06)%](P<0.05).@*Conclusions@#Depletion of PRDM9 repressed the osteogenic differentiation of stem cells from periodontal ligament in vitro and in vivo.
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Root canal preparation is one of the important procedures in root canal treatment as well as one of the key factors to the success of root canal treatment. It consists root canal cleaning and shaping, and further provides a favourable condition for root canal obturation. Because of the complexity and irregularity of root canal system, complications may occur during the root canal mechanical preparation, such as root canal ledges, transportations, perforations, instruments separating and flare ups. Understanding the reason and management of root canal mechanical preparation complications is helpful to prevent its occurrence and to reduce the unfavourable prognosis as well. This article discusses and systematically analyzes the reason, prevention and management of the complications in root canal mechanical preparation, in order to enhance the awareness of clinicians on these complications.
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Objective@#To compare the phase transformation behavior, bending property and cyclic fatigue resistance of CM-wire, R-phase and M-wire nickel-titanium endodontic files treated by 3 heat treatment techniques.@*Methods@#Hyflex CM (25 mm, 25#/0.06) made from CM wire, TF (25 mm, 25#/0.06) made from R-phase heat treatment, ProTaper Next X2 (25 mm, tip size 25#/0.06) made from M-wire, Mtwo (25 mm, 25#/0.06) and ProTaper F2 (25 mm, tip size 25#/0.08) made from conventional nickel-titanium wire were chosen. Five of each files were chosen for differential scanning calorimetric (DSC) evaluation (n=5). The specimens were prepared from adjacent portions of the shaft. The weight and length were typically (20±1) mg and 2-3 mm. Another eight of the 5 nickel-titanium files were undergone cantilever-bending test, respectively (n=8). Further ten of the 5 instruments were submitted to the cyclic fatigue test by using a simulated metal root canal (n=10). The data of Ms, Mf, As, Af, ΔH, bending load, number of cyclic fatigue (NCF), fragment length were analyzed using one-way analysis of variance at a significance level of P<0.05.@*Results@#The Af of Hyflex CM [(60.27±0.94) ℃] and ProTaper Next [(51.40±0.32) ℃] were higher than body temperature of 37 ℃. The bending load values at 3.0 mm deflection of Hyflex CM [(0.867±0.074) N], TF [(1.275±0.146) N], Mtwo [(2.281±0.426) N], ProTaper Next [(3.104±0.252) N] and ProTaper [(4.227±0.483) N] increased gradually and significantly. The NCF of Hyflex CM (582±99), TF (427±85), ProTaper Next (158±22), Mtwo (129±32) and ProTaper (65±20) decreased gradually.@*Conclusions@#The 3 heat treatment techniques exert tremendous influence on the phase transformation behavior and mechanical characteristics of the files, which demonstrate improved bending property and cyclic fatigue resistance than the conventional ones.
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Objective@#To investigate the association between the frequency and filling rate of lateral canals and the sealing quality in the apical third roots of the permanent teeth with failed endodontic treatments, so as to explore the failure factors of root canal therapy.@*Methods@#Clinical records of the permanent teeth with failed endodontic treatments were collected from the Department of Endodontics, Capital Medical University School of Stomatology during a period of 2 years. The teeth were diagnosed as chronic apical periodontitis and then undergone endodontic microsurgery. The sealing quality of the apical root canal was observed by means of periapical radiographs. The surgical treatments were performed and the resected root apices were collected. The samples were scanned by micro-computed tomography and the 3D volume rendered images of the resected root apices were reconstructed. Moreover, the frequency and the filling rate of lateral canals in the apical third roots were calculated. The potential relationship between tooth position and the presence of lateral canals was evaluated.@*Results@#Totally 89 teeth with 89 root apices met the inclusion criteria and were included in the present study. The rate of correct-filling, underfilling and overfilling was 40% (36/89), 32% (28/89), and 28% (25/89), respectively, examined by periapical radiographs. Amongst all of the 89 samples, lateral canals were found in 44 samples. The incidence of apices with lateral canals was 49% (44/89). Furthermore, 3 out of 44 samples were fully filled with material in the lateral canals, and the rest 41 samples showed no filling materials. The filling rate of the lateral canals was 7% (3/44). However, no significant difference was detected between the tooth position and the presence of lateral canals (P>0.05).@*Conclusions@#The sealing quality of the apical third roots in permanent teeth with failed endodontic treatments was not good enough. The incidence of apices with lateral canals was high, but the filling rate of the canals was low. Further studies are needed to explore the relationship between lateral canals and the failure of endodontic treatment.
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The excellent magnification and illumination of the operating microscope not only helps to improve the quality of conventional root canal therapy, but also plays an important role in the diagnosis and treatment of the difficult cases of endodontic diseases. It has an irreplaceable position over other equipment especially for the treatment of root canal therapy complications and the apical surgery. The structure and operation of the operating microscope are relatively complicated. The proficiency of the dentist may influence the evaluation of its clinical application effect. Based on the review of literature and author's clinical experience, this paper evaluates the role of operating microscope in the diagnosis and treatment of endodontic diseases.
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Objective:To evaluate the effects of different growth conditions on E.faecalis growth in the microfluid chip and the penetration of E.faecalis into microtubes.Methods:Four units on the chip were randomly selected as control,BHI,nutrient-Tdeprived (PBS) and pH 10 groups.The growth of E.faecalis was monitored by microscope for a period of 72 h after the suspension of E.faecalis had been added into the chip.Results:The microscopic analysis showed a distinct variation in the growth rate and morphological feature under different experimental conditions.he depth of bacterial penetration was significantly greater in BHI group.Conclusion:This study demonstrated that environmental changes can significantly influence the growth and penetration of E.faecalis into the micro tubes.
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<p><b>OBJECTIVE</b>This study aims to assess and compare the prevalence of Porphyromonas endodontalis (P. endodontalis) in root canals associated with primary and secondary endodontic infections by using 16s rDNA PCR and real-time fluorescence quantitative polymerase chain reaction (RTFQ-PCR).</p><p><b>METHODS</b>A total of 120 adult patients with one radiographically documented periapical lesion were included. Sixty teeth presented with primary endodontic infections and 60 with secondary endodontic infections requiring retreatment. P. endodontalis was identified by using 16s rDNA PCR techniques. The positive DNA expression of P. endodontalis in two types of infected root canals were quantitatively compared by using SYBR GREEN I RTFQ-PCR.</p><p><b>RESULTS</b>The prevalence of P. endodontalis in the root canals with primary endodontic infections was significantly higher than that in root canals with secondary endodontic infections (P = 0.001). However, RTFQ-PCR results showed no significant difference in DNA expression quantities between the primary and secondary endodontic infections root canals (P = 0.303).</p><p><b>CONCLUSION</b>P. endodontalis is more highly associated with root canals having primary endodontic infections, although P. endodontalis colonize in both root canals with primary and secondary chronic apical periodontitis.</p>
Subject(s)
Adult , Humans , DNA, Bacterial , Dental Pulp Cavity , Gram-Negative Bacterial Infections , Polymerase Chain Reaction , Porphyromonas endodontalis , RetreatmentABSTRACT
<p><b>OBJECTIVE</b>To evaluate the shaping ability of Reciproc, WaveOne,Mtwo and ProTaper instruments in simulated S-shaped root canals.</p><p><b>METHODS</b>A total of 40 simulated S-shaped resin blocks were divided randomly into four groups, each group was prepared with Reciproc (group A), WaveOne (group B), Mtwo (group C) and ProTaper (group D), respectively. The preparation time and reduction of working length after preparation were measured. Pre- and postoperative images were obtained by a scanner and superimposed using Photoshop. Changes of coronal curve and apical curve curvature, as well as material removal from the inner and outer canal wall at 10 points beginning 1 mm from the end point of the canal, were measured using ImageJ. Centering ability was determined, accordingly. The data were analyzed using the one-way ANOVA and Student-Newman-Keuls.</p><p><b>RESULTS</b>The preparation time of group A and group B were (42.1 ± 2.7) and (41.5 ± 3.2) s respectively, significantly less than that of group C and group D [(62.7 ± 2.8), (62.8 ± 5.2) s] (P < 0.05).Reductions of working length after preparation were not significantly different among the four groups (P > 0.05). Coronal curve curvature changes of group A, group B and group D were (4.69 ± 0.63)°, (4.15 ± 0.89)° and (4.13 ± 0.59)° respectively, significantly less than that of group C[(5.26 ± 0.70)°], P < 0.05. Apical curve curvature changes were not significantly different among the four groups (P > 0.05). At the 2 mm point, the centering ability of group A[ (-0.242 ± 0.042) mm], group B[(-0.191 ± 0.077) mm], and group D[(-0.272 ± 0.046) mm] was better than group C[(-0.343 ± 0.057 mm] significantly (P < 0.05). At the 3 mm and 4 mm point, the centering ability of group A and group B was better than group C and group D significantly (P < 0.05). Whilst at the 5 mm point, the centering ability of group D was better than group A and group B (P < 0.05).</p><p><b>CONCLUSIONS</b>Reciproc and WaveOne could complete preparation faster and could maintain the original S-shaped canal curvature better than Mtwo and ProTaper, especially in the apical part.</p>
Subject(s)
Humans , Analysis of Variance , Dental Alloys , Dental Instruments , Dental Pulp Cavity , Equipment Failure , Nickel , Root Canal Preparation , TitaniumABSTRACT
<p><b>OBJECTIVE</b>To study the prevalence of Parvimonas micra (Pm) and the associations between Pm and pulp dominant pathogens in order to reflect the colonization of Pm in the infected root canals with chronic periradicular periodontitis.</p><p><b>METHODS</b>A total of 120 teeth diagnosed as chronic periradicular periodontitis from 104 patients were included into the study. The teeth were allocated into untreated (primary infectious) and root-canal- treated (secondary infectious) groups with 60 in either group. Samples were collected from the root canals using sterile files and paper points, and subsequent extraction of bacterial DNA was undertaken. The Pm 16S rDNA level was evaluated using 16S rDNA PCR. The prevalence of Pm in chronic periradicular periodontitis was determined accordingly. Then, the associations of Pm and Enterococcus faecalis (Ef), Porphyromonas endodontalis (Pe) as well as Porphyromonas gingivalis (Pg) were analysed.</p><p><b>RESULTS</b>Pm was detected in 40% (24/60) of the samples from the primary infectious group, 5% (3/60) from the secondary infectious group. The prevalences of Pm from the two groups were different significantly (χ² = 21.06, P < 0.05). Significant correlations (untreated group OR = 5.98, root-canal-treated group OR = 33.50) between Pm and Pe were identified in both groups, while the correlations between Pm and Pg as well as Ef were not of significance, respectively.</p><p><b>CONCLUSIONS</b>A significantly higher relevance ratio of Pm was estimated in the primary infectious group than the secondary infectious one. Pm and Pe were correlated significantly in the infected root canals, suggesting a symbiotic relation between these two bacteria.</p>
Subject(s)
Humans , Chronic Periodontitis , DNA, Bacterial , Dental Pulp Cavity , Microbiology , Enterococcus faecalis , Periapical Periodontitis , Microbiology , Polymerase Chain Reaction , Porphyromonas endodontalis , Porphyromonas gingivalis , Root Canal TherapyABSTRACT
<p><b>OBJECTIVE</b>This study aims to develop and observe a model system of the periapical biofilm structure of Enterococcus faecalis (E. faecalis).</p><p><b>METHODS</b>A total of 24 intact human single-rooted premolars extracted for orthodontic reasons were collected and randomly divided into eight groups (n = 3). The specimens were subjected to ultraviolet disinfection, inoculated with E. faecalis (ATCC 29212) suspension adjusted to 1 x 10(8) CFU x mL(-1), and incubated at 37 degrees C for 1, 2, and 7 d. Specimen groups were prepared for scanning electron microscope to examine the biofilm formation. The specimens in the confocal laser scanning microscope (CLSM) groups were stained with propidium iodide (PI) and ConA-fluorescein isothiocyanate (ConA-FITC) to examine the biofilm formation. The images were randomized, and biofilm coverage (%) was assessed using Photoshop CS5.</p><p><b>RESULTS</b>The biofilm coverage (%) on the cementum increased with increasing incubation period. The biofilm coverage of the 7 d group was significantly higher than those of the 1 and 2 d groups (P < 0.05). The values of the latter two groups were not significantly different (P > 0.05). Dense aggregations composed of E. faecalis and the amorphous matrix were observed on the root cementum surfaces of the specimens in the 7 d group. The bacteria were stained red by PI, and the matrix was stained green by ConA-FITC under CLSM observation. The biofilm coverage (%) on the samples in the 7 d group was 17.23% +/- 1.52%, showing multi-level space structure and water channels.</p><p><b>CONCLUSION</b>E. faecalis forms bacterial biofilms on the root cementum surface in 7 d. The biofilms were composed of E. faecalis and the amorphous matrix.</p>
Subject(s)
Humans , Biofilms , Dental Pulp Cavity , Enterococcus faecalis , In Vitro Techniques , Microscopy, ConfocalABSTRACT
<p><b>OBJECTIVE</b>This study aims to evaluate the shaping capability of Reciproc, WaveOne, Mtwo, and ProTaper instruments in simulated root canals.</p><p><b>METHODS</b>A total of 40 simulated resin blocks were divided randomly into four groups. Each group was prepared with Reciproc (Group 1), WaveOne (Group 2), Mtwo (Group 3), and ProTaper (Group 4). The preparation time and reduction in working length after preparation were measured. Pre- and post-operative images were obtained with a scanner and superimposed through Photoshop. The changes in canal curvature and material removal from the inner and outer canal walls at 10 points beginning at 1 mm from the end point of the canal were measured with Image J. Centering capability was determined accordingly. Data were analyzed through one-way ANOVA, SNK, and Kruskal-Wallis at a significance level of P < 0.05.</p><p><b>RESULTS</b>The preparation time of Group 2 was (53.7 ± 6.7) s, whereas those of Groups 1, 3, and 4 were (86.9 ± 8.1) s, (112.2 ± 8.2) s, and (177.9 ± 11.2) s, respectively; the difference was found to be significant (P < 0.05). The reductions in working length among the four groups after preparation were not significantly different (P > 0.05). The canal curvature for Groups 1 to 4 were 2.671° ± 0.637°, 2.667° ± 0.450°, 3.664° ± 0.870°, and 3.797° ± 0.601°, respectively. The changes for Groups 1 and 2 were significantly smaller than those for Groups 3 and 4. At the 3 mm point, the transportation of Group 1 was (-0.016 ± 0.094) mm, which was significantly less than that of the other instruments (P<0.05). At the 4 mm and 5 mm points, the trans- portation values of Group 2 were (-0.080 ± 0.104) mm and (-0.312 ± 0.088) mm, which were significantly less than that of Group 1 [(-0.243 ± 0.099) mm, (-0.404 ± 0.064) mm, P < 0.05].</p><p><b>CONCLUSION</b>Reciproc and WaveOne can complete preparation faster and can maintain the original canal curvature better than Mtwo and ProTaper. Reciproc exhibits superior centering capability in the apical part of the canal, whereas WaveOne exhibits superior centering capability in the middle part of the canal.</p>
Subject(s)
Humans , Dental Pulp Cavity , In Vitro Techniques , Nickel , Root Canal Preparation , TitaniumABSTRACT
<p><b>OBJECTIVE</b>To investigate the microbial composition and differences in dental plaque of caries and caries-free adults.</p><p><b>METHODS</b>Caries-active (n = 16) was defined as an individual who had at least three untreated decayed tooth and decayed-missing-filled-tooth (DMFT) score greater than 6. Caries-free (n = 16) was defined as an individual who had a DMFT score equal to zero. The patients were 18-35 years old. Samples from supra-gingival plaque were obtained and PCR-denaturing gel electrophoresis cloning and sequencing of caries pathogens were used to catch the core microbial of dental caries.</p><p><b>RESULTS</b>Six phylum, 28 genus and 88 species were detected. In caries group, Prevotella, Capnocytophaga, Actinomyces, Veillonella and Corynebacterium were predominant, accounting for 56.2% (334/594) of the total cloning number of caries group. Caries-free group contained more predonminant genus than caries group. Prevotella, Veillonella, Capnocytophaga, Corynebacterium, Streptococcus, Actinomyces, Aggregatibacter and Neisseria were predominant, accounting for 65.2% (354/543) of the total cloning number of caries-free group. Caries group had less diversity than the caries-free group. The difference was statistically significant (P < 0.05).</p><p><b>CONCLUSIONS</b>Caries might be caused by potentially pathogenic microbial communities rather than a single pathogen. In the progress of dental caries, the microbial diversity decreased.</p>
Subject(s)
Adult , Humans , DMF Index , Dental Caries , Microbiology , Dental Plaque , Microbiology , Gingiva , MicrobiologyABSTRACT
Objective: To evaluate effect of the morphology of simulated S-shaped root canals with Reciproc or Mtwo instruments on root canal irrigation. Methods: A total of 40 simulated S-shaped resin blocks were randomly divided into 2 groups (n=20), which was prepared by Reciproc or Mtwo. Blue ink was injected with constant speed and volume into the canals using 30G lateral opening syringe. hTe distance from needle tip to apex and vapor lock length were measured. A type of 25# 0.04 gutta-percha point was used to stir and remove the vapor lock. hTe time for removal of the vapor lock was recorded. Another syringe was used to inject saline into the canals and to measure the length of stagnant water. Results: hTe distance from needle tip to apex in the Reciproc group was signiifcantly longer than that in the Mtwo group [(4.276 ± 0.221) mm vs (3.459 ± 0.205) mm,P<0.05]. The vapor lock length in the Reciproc group was signiifcantly longer than that in the Mtwo group [(4.472 ± 0.230) mm vs (3.668±0.217) mm,P<0.05]. hTe time to remove vapor lock was signiifcantly shorter in the Reciproc group than that in the Mtwo group [(10.13 ± 1.79) s vs (15.29 ± 2.15) s,P<0.05]. The length of stagnant water was also shorter in the Reciproc group than that in the Mtwo group[(1.351 ± 0.142) mm vs (2.245 ± 0.206) mm,P<0.05]. Conclusion: hTe morphology of S-shaped root canal affects the root canal irrigation. hTe effect of root canal irrigated by Reciproc is better than that by Mtwo.
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Objective To investigate the influence of ultrasonic cleaning time and disinfecting frequency on physical property of Ni-Ti root canal files in order to understand the safety and feasibility of ultrasonic cleaning and high temperature and high pressure disinfection for Ni-Ti root canal files.Methods The Ni-Ti root canal files used in this study were ProTaper,Mtwo and Hero642,5 files were selected from each kind.After the ultrasonic cleaning and high temperature high pressure disinfection the files underwent breaking test,the breaking time was recorded.Unclean and non-sterile Ni-Ti root canal files were set as control.Results After different time of ultrasonic cleaning,ProTaper and Mtwo showed no difference in breaking time,but the result was opposite in Hero642.After different times of disinfection,Mtwo showed no difference in breaking time,but significant difference was seen in the other two kinds.Conclusions Ultrasonic cleaning time has no significant influence on physical property of ProTaper and Mtwo Ni- Ti root canal files,but the influence was significant for Hero642.Disinfection frequency had no significant influence on physical property of ProTaper and Hero642 Ni-Ti root canal files,but the influence was significant for Mtwo Ni-Ti root canal files.
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Objective:To evaluate the prevalence of Pe in clinical samples of chronic periapical periodontitis.Methods:A total of 100 clinical samples of chronic periapical periodontitis were collected and Pe 16S rDNA was detected by using 16S rDNA gene-directed PCR.The detection rate of Pe were calculated.Results:The detection rate of Pe was 50% in the 100 clinical samples.Conclusion:The results indicate that Pe is closely associated with endodontic infections.
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Objective:To observe the effect of soluble CD14 (sCD14) on the inducing activity of lipopolysaccharide(LPS) on human gingival fibroblasts(HGFs). Methods:In vitro cultured HGFs were stimulated by FITC labeled LPS at the concentration of 0 (control), 100 ng/ml, 100 ng/ml LPS+100 ?g/ml sCD14 and 100 ng/ml LPS+100 ?g/ml ENP respectively for 24 h. The binding activity of LPS to HGFs was measured in the level of mean fluorescence intensity of FITC-LPS.TNF-? and IL-6 in the culture supernatant were measured by ELISA. Results:The binding activity of FITC-LPS to HGFs and the level of TNF-? and IL-6 in culture supernatant were significantly decreased in sCD14 and ENP group(P