[Systemic lupus erythematosus associated macrophage activation syndrome with neuropsychiatric symptoms: A report of 2 cases].

Systemic lupus erythematosus (SLE) associated macrophage activation syndrome (MAS) is clinically severe, with a high mortality rate and rare neuropsychiatric symptoms. In the course of diagnosis and treatment, it is necessary to actively determine whether the neuropsychiatric symptoms in patients are caused by neuropsychiatric systemic lupus erythematosus (NPSLE) or macrophage activation syndrome. This paper retrospectively analyzed the clinical data of 2 cases of SLE associated MAS with neuropsychiatric lesions, Case 1: A 30-year-old female had obvious alopecia in 2019, accompanied by emaciation, fatigue and dry mouth. In March 2021, she felt weak legs and fell down, followed by fever and chills without obvious causes. After completing relevant examinations, she was diagnosed with SLE and given symptomatic treatments such as hormones and anti-infection, but the patient still had fever. The relevant examinations showed moderate anemia, elevated ferritin, elevated triglycerides, decreased NK cell activity, and a perforin positivity rate of 4.27%, which led to the diagnosis of "pre-hemophagocytic syndrome (HPS)". In May 2021, the patient showed mental trance and babble, and was diagnosed with "SLE-associated MAS"after completing relevant examinations. After treatment with methylprednisolone, anti-infection and psychotropic drugs, the patient's temperature was normal and mental symptoms improved. Case 2: A 30-year-old female patient developed butterfly erythema on both sides of the nose on her face and several erythema on her neck in June 2019, accompanied by alopecia, oral ulcers, and fever. She was diagnosed with "SLE" after completing relevant examinations, and her condition was relieved after treatment with methylprednisolone and human immunoglobulin. In October 2019, the patient showed apathy, no lethargy, and fever again, accompanied by dizziness and vomiting. The relevant examination indicated moderate anemia, decreased NK cell activity, elevated triglycerides, and elevated ferritin. The patient was considered to be diagnosed with "SLE, NPSLE, and SLE-associated MAS". After treatment with hormones, human immunoglobulin, anti-infection, rituximab (Mabthera), the patient's condition improved and was discharged from the hospital. After discharge, the patient regularly took methylprednisolone tablets (Medrol), and her psychiatric symptoms were still intermittent. In November 2019, she developed symptoms of fever, mania, and delirium, and later turned to an apathetic state, and was given methylprednisolone intravenous drip and olanzapine tablets (Zyprexa) orally. After the mental symptoms improved, she was treated with rituximab (Mabthera). Later, due to repeated infections, she was replaced with Belizumab (Benlysta), and she was recovered from her psychiatric anomalies in March 2021. Through the analysis of clinical symptoms, imaging examination, laboratory examination, treatment course and effect, it is speculated that the neuropsychiatric symptoms of case 1 are more likely to be caused by MAS, and that of case 2 is more likely to be caused by SLE. At present, there is no direct laboratory basis for the identification of the two neuropsychiatric symptoms. The etiology of neuropsychiatric symptoms can be determined by clinical manifestations, imaging manifestations, cerebrospinal fluid detection, and the patient's response to treatment. Early diagnosis is of great significance for guiding clinical treatment, monitoring the condition and judging the prognosis. The good prognosis of the two cases in this paper is closely related to the early diagnosis, treatment and intervention of the disease.

[Applications of Chest Wall Reconstructive Materials].

Chest wall reconstruction is a key approach to restoring the structure and function of the defective chest wall after tumor excision. While autologous flaps have been ideal materials for soft tissue reconstruction,the optimal skeletal reconstructive material still remains controversial. Currently,besides autologous bones,non-biodegradable materials have been used widely,which offer sufficient strength and stability but with some inevitable complications. Many studies have explored the clinical applications of biodegradable materials and the improvements in their characteristics,and some of these materials may be clinically feasible. This article reviews the recent advances in the applications of reconstructive materials.

Various Surface Treatments to Implant Provisional Restorations and Their Effect on Epithelial Cell Adhesion: A Comparative In Vitro Study.

PURPOSE AND OBJECTIVE: The aim of this in vitro study was to investigate the ability of epithelial cells to attach to or proliferate on various mechanical or chemical surface treatments of an implant provisional material. MATERIALS AND METHODS: Polyethyl methacrylate discs 10 mm in diameter and ∼0.2 to 0.75 mm in width were used in the study. Experimental discs were treated with either a mechanical (pumice, varnish for shine, or high polishing) or a chemical agent (alcohol, chlorhexidine, or steam) to provide cleaning and/or polishing. Using primary human epidermal keratinocytes, experiments were performed to test the adhesion or proliferation of cells on the discs with various surface treatments. RESULTS: Scanning electron microscope analysis, rhodamine staining, and cell counting using a hemocytometer corroborated all findings and illustrated that the highest cell adhesion was found to be in the smooth surface treatment groups and the poorest adhesion was found to be in the rough surface groups and chemical treatment group. CONCLUSION: Within the limitations of this study, the following clinical protocol is recommended for finishing, polishing, and disinfecting implant provisional restorations: coarse, medium, fine pumice → high polishing (if desired) → steam. It is recommended to avoid applying varnish in the perimucosal area near the epithelium. This study could establish the most appropriate way to handle provisional restorations in the peri-implant sulcus for improved soft tissue health, esthetics, and long-term stability.

Deferoxamine enhances the migration of dental pulp cells via hypoxia-inducible factor 1α.

In previous studies, we found that deferoxamine (DFO) improved the migration of dental pulp cells (DPCs). The present study aimed to determine whether the effects of DFO on the migration of DPCs were regulated via hypoxia-inducible factor 1α (HIF-1α). Recombinant adenovirus vectors carrying short hairpin RNA (shRNA) targeting the human HIF-1α gene (pAd-GFP-shRNA-HIF-1α) and green fluorescent protein (GFP) were constructed. The expression of HIF-1α was inhibited by pAd-GFP-shRNA-HIF-1α at messenger RNA and protein levels. The secretion of stromal cell-derived factor 1α (SDF-1α) or vascular endothelial growth factor (VEGF) in DPCs treated with 10 µM DFO was higher than that in the control condition. The migration of DPCs was enhanced by 10 µM DFO. However, the effects of DFO on DPCs were partially reversed by silencing the HIF-1α gene in enzyme-linked immunosorbent assay or migration assay. Cumulatively, we conclude that DFO upregulated the secretion of SDF-1α or VEGF in DPCs and improved the migration of DPCs through HIF-1α.

[Effect of recombinant connective tissue growth factor on proliferation and odontogenic differentiation of dental pulp cells].

PURPOSE: To analyze the effect of recombinant connective tissue growth factor(rCTGF) on proliferation and differentiation of human dental pulp cells(hDPCs). METHODS: Human dental pulp cells were cultured in vitro and treated with rCTGF at different concentrations (0, 1, 10, 100 ng/mL). The proliferation of dental pulp cells was detected by CCK8 assay. The formation of mineralized nodules was determined by alizarin red staining and half-quantitative alizarin Red S assay. qRT-PCR was utilized to detect the expression of odontogenic differentiation related genes DMP-1, DSPP and OC, and the phosphorylation level of ERK1/2 signaling pathway was detected by Western blot. The data were analyzed with SAS 9.3 software package. RESULTS: High concentration of rCTGF(100 ng/mL) could promote proliferation of dental pulp cells. After mineralization induction, 10 g/mL rCTGF had the best effect on promoting the formation of mineralized nodules in dental pulp cells, and calcium ion deposition was the most obvious(P<0.05). The expression of odontogenic differentiation related genes DMP-1 and DSPP was significantly up-regulated(P<0.05). Western blot results showed that hDPCs stimulated by 10 ng/mL rCTGF could increase the expression of p-ERK1/2. CONCLUSIONS: rCTGF may promote the proliferation and differentiation of human dental pulp cells through activating ERK1/2 signaling pathway.

Effects of silicate-based composite material on the proliferation and mineralization behaviors of human dental pulp cells: An in vitro assessment.

The objective of this study was to investigate the effects of a silicate-based composite material on proliferation and mineralization of human dental pulp cells (hDPCs), which was compared with those of calcium hydroxide (Ca(OH)2, CH) and tricalcium silicate (Ca3SiO5, C3S). HDPCs were cultured with CH, C3S and tricalcium silicate/dicalcium silicate (Ca3SiO5/Ca2SiO4, C3S/C2S) composites extract. The CCK-8 assay showed that the composite material stimulated the proliferation of hDPCs. The odontogenic marker genes and DSPP protein expression were more significantly up-regulated by the C3S/C2S composite material compared with pure CH and C3S. HDPCs cultured with composite material extract exert stronger ALP activity and alizarin red S staining. C3S/C2S composite material was advantageous over pure C3S by showing enhanced ability to stimulate the proliferation and odontogenic differentiation of hDPCs, suggesting that the C3S/C2S composite materials possess desirable biocompatibility and bioactivity, and might be a new type of pulp-capping agent and dentin alternative materials.

[The effect of dental health instruction before treatment on anxiety of patients with acute pulpitis].

PURPOSE: To evaluate the effect of dental health instruction before treatment on dental anxiety of patients with acute pulpitis. METHODS: One hundred and fifty-four patients with acute pulpitis treated in our department from July 2011 to June 2013, and aged from 19 years to 64 years, were selected. They were randomly divided into experimental group and control group. Seventy-eight patients of the experimental group accepted dental health instruction before treatment, while 76 cases in the control group received regular treatment. Two questionaires of dental anxiety were proceeded to both groups respectively before treatment. The data was analyzed for Student's t test and Chi-square test using SPSS12.0 software package. RESULTS: Dental anxiety (DA) points of the experimental group after dental health instruction were significantly lower than that before treatment (t=4.1346, P<0.01). DA points of the experimental group after dental health instruction were significantly lower than that of the control group (t=6.2784, P<0.01). The acceptability of the experimental group towards the first treatment was significantly higher than of the control group. The completion rate of the following treatment of the experimental group was also significantly higher than that of the control group. CONCLUSIONS: Dental health instruction to patients with acute pulpitis before treatment are helpful to reduce the pressure and relieve the anxiety during the treatment, so that the patients will complete the first and the following treatment successfully.

Effects of deferoxamine on the repair ability of dental pulp cells in vitro.

INTRODUCTION: In previous studies, we found that hypoxia promoted the mineralization of dental pulp cells (DPCs). However, the clinical application of hypoxia as a therapy is questionable or unfeasible. Deferoxamine (DFO), a medication for iron overload, has also been shown to induce hypoxia. The purpose of this study was to investigate the effects of DFO on the repair ability of DPCs. METHODS: DPCs were obtained by using a tissue explant technique in vitro and were treated with different concentrations of DFO or hypoxia culture for 2 days. The viability, proliferation, migration, and odontogenic differentiation of DPCs were assayed and analyzed. The expression of hypoxia-inducible factor 1-alpha (HIF-1α) was assessed through Western blotting. RESULTS: Ten micromolars of DFO enhanced the expression of HIF-1α similarly to hypoxia and did not affect the viability of DPCs for 2 days. Furthermore, the proliferation, migration, and odontogenic differentiation of DPCs were promoted by DFO. CONCLUSIONS: These results suggest that DFO might improve the repair ability of DPCs by HIF-1α.

Hydrogen peroxide induces apoptosis in human dental pulp cells via caspase-9 dependent pathway.

INTRODUCTION: Reactive oxygen species are a group of metabolic intermediates produced during oxidative metabolism in eukaryotic cells. They include superoxide anion (O2(-)), hydrogen peroxide (H2O2), hydroxyl radical (·OH), and (1)O2. Of these intermediates, H2O2 is the most stable. Dental pulp cells can be invaded by tooth bleaching, laser radiation, and dental materials. This can influence the intracellular level of reactive oxygen species. Apoptosis, which is the best-known form of programmed cell death, is pivotal to tissue development and regeneration. Little information is available regarding the relationship between H2O2 and apoptosis of human dental pulp cells (hDPCs). The purpose of this study was to investigate whether H2O2 can induce apoptosis in hDPCs and its signaling way. METHODS: HDPCs were obtained by using a modified tissue explant technique in vitro and cultured at 37°C, 20% O2 (5% CO2, 95% air) in Dulbecco modified Eagle medium. Cell viability was investigated by methyl-thiazol-tetrazolium assay. Cell apoptosis was detected by using the annexin V-fluorescein isothiocyanate/propidium iodide apoptosis assay and flow cytometry. Expression of activated caspase-3, cleaved caspase-9, and ß-actin was analyzed by using Western blot. RESULTS: Cell viability of hDPCs decreased more in treated groups than in the control group from days 1 to 7. The relative number of apoptotic cells and the expression of activated caspase-3 and cleaved caspase-9 were much higher in groups exposed to 20 and 50 µmol/L H2O2. CONCLUSIONS: These results imply that low concentrations of H2O2 are cytotoxic to hDPCs and induce apoptosis in hDPCs in a caspase-9-dependent way.

Role of the extracellular signal-regulated kinase 1/2 pathway in driving tricalcium silicate-induced proliferation and biomineralization of human dental pulp cells in vitro.

INTRODUCTION: The aim of this study was to investigate the role of the extracellular signal-regulated kinase 1/2 (ERK1/2) pathway in regulating tricalcium silicate (C3S)-driven proliferation and biomineralization of human dental pulp cells (hDPCs) in vitro. METHODS: Human DPCs were cultured in C3S-containing medium and compared with untreated controls. Cell viability was measured by the methyl-thiazol-tetrazolium assay. Biomineralization was assessed by staining calcium deposits on the extracellular matrix with von Kossa and alizarin red S stains. Phosphorylated ERK1/2 was evaluated by immunoblotting. The ERK1/2 inhibitor U0126 was used to assess the role of this pathway on stage of the cell cycle and mineralization-dependent gene expressions of hDPCs by using flow cytometry and real-time polymerase chain reaction, respectively. Data were analyzed by analysis of variance followed by the Student-Newman-Keuls post hoc test, with significance set at P < .05. RESULTS: The viability and biomineralization of hDPCs were promoted by C3S extracts (P < .05). Phosphorylated ERK1/2 strongly appeared after hDPCs were cultured in the C3S extracts for 30 minutes. Moreover, inhibition of the ERK1/2 pathway in C3S-treated hDPCs decreased proliferation and the expression of mineralization-dependent genes, including collagen type I, dentin sialophosphoprotein, osteopontin, and osteocalcin (P < .05). CONCLUSIONS: C3S stimulated the proliferation and biomineralization of hDPCs in vitro, with the ERK1/2 pathway playing a key role in the regulation of these effects.

[Detection of reactive oxygen species of human dental pulp cells by flow cytometry].

PURPOSE: To establish a method for detection of reactive oxygen species(ROS) of human dental pulp cells(HDPCs) by flow cytometry. METHODS: HDPCs were obtained using tissue explant technique in vitro. The subcultured cells were exposed to peroxide oxygen(H2O2) of different concentrations from 50 µmol/L to 400 µmol/L for 30 minutes, then incubated with two different concentrations of 2',7'-dichlorofluorescein diacetate (DCFH-DA), which were 10 µmol/L and 20 µmol/L for 20 minutes at 37 degrees centigrade in dark. The fluorescence intensities of intracellular dichlorofluorescein(DCF) were detected by flow cytometry. Statistical analysis was carried out by SPSS 13.0 software software. RESULTS: The positive rate varied with different concentrations of detectors. The fluorescence intensities remained insignificant difference among samples incubated with the same concentration of detector and H(2)O(2),and increased by rising of the incubating concentration of H(2)O(2). CONCLUSIONS: The detector with concentration of 20 µmol/L shows higher detector loading rate(positive rate). The intracellular ROS level changes as the H(2)O(2) treatment concentration rising from 50 to 400 µmol/L. The application of flow cytometry to measure the ROS in HDPCs is simple, reliable and stable.

[Effects of polyethylene oxide at different concentrations on abdominal aortic blood flow and vascular resistance in rats].

OBJECTIVE: To observe the effect of polyethylene oxide (PEO) solution at different concentrations on abdominal aortic blood flow and vascular resistance in rats and evaluate the safety and drag-reducing effect of PEO solution. METHODS: Thirty-two rats were anesthetized and randomly divided into 4 groups. An ultrasonic flow probe was deployed on the abdominal aorta (5 mm above the common iliac artery) to measure the blood flow. The carotid artery pressure, iliac artery pressure, iliac vein pressure, central venous pressure (CVP) and ECG were also monitored. Saline or different concentrations of PEO [(1x10(-6)(low), 1x10(-5)(middle) and 5x10(-5)(high) g/ml)] were injected in the 4 groups of rats through the caudal vein at a constant rate of 5 ml/h for 20 min, and the changes of the vascular resistance was observed. RESULTS After injections of 1x10(-6) and 1x10(-5) g/ml PEO, the abdominal aortic flow increased significantly (P<0.05) while the vascular resistance was reduced (P(low)=0.052, P(middle)<0.001) as compared to those in the saline control group. Following the injection with 5x10(-5) g/ml PEO, the abdominal aortic flow increased to a threshold in the initial 4 min, after which it rapidly decreased to approach the baseline levels despite continuous infusion. Blood pressure remained stable after the injections except for 5x10(-5) g/mlPEO injection, which resulted in a reduction of the blood pressure by about 10 mmHg (P=0.014). The heart rate and CVP both underwent no significant changes following the injections. CONCLUSION: The drag-reducing effect of PEO is closely related to its concentration, and compared with 1x10(-6) g/ml, 1x10(-5) g/ml PEO more effectively increases the blood flow and decreases the resistance. The effectiveness and safety of EPO are attenuated at a concentration higher than 5x10(-5) g/ml.

[Effect of polyethylene oxide on red blood cell velocity in rat cremaster microcirculation].

OBJECTIVE: To investigate the drag-reducing effect of polyethylene oxide (PEO) on the velocity of red blood cells in rat cremaster microcirculation. METHODS: Blood samples were collected from 6 Wistar male rats (100-110 g) via the post-orbital venous plexus. The red blood cells were separated by centrifugation and labeled by fluorescinisothiocyate (FITC). After successful establishment of cremaster model, the labeled red blood cells were injected into the jugular vein, and the microcirculation was observed and recorded under fluorescence microscope. The hemodynamic parameters and microcirculation video was recorded every 4 min since 4 min before PEO or normal saline injection. Both PEO (10 ppm) and normal saline was injected into the same rat in random sequence at a constant rate of 3.5 ml/h for 20 min followed by observation for another 20 min. The velocity of the labeled-red blood cells was determined by IPP 6.0 software. RESULTS: Compared with normal saline, PEO significantly increased the velocity of the red blood cells in the rat cremaster microcirculation (498.7-/+182.89 microm/s vs 773.54-/+308.27 microm/s, P=0.012). No significant changes in the heart rate and arterial blood pressure were observed during the experiment (P=0.836, P=0.420). CONCLUSION: PEO at an extremely low concentration can significantly increase the velocity of the red blood cells in rat cremaster microcirculation and produces no significant impact on heart rate and arterial blood pressure.

[A comparative study of three different rotary nickel titanium systems in the preparation of curved molar canals].

PURPOSE: To analyze the shaping ability of three different rotary nickel-titanium instruments in curved molar canals. METHODS: Three groups of extracted molars that were balanced in terms of curvature were instrumented by M(two), rotary ProTaper and Hero642 nickel-titanium systems, respectively. The standard digital radiographs were taken to record the profiles of root canals and the positions of the tips of the instruments. At last, the curvature degrees and the apical transportation indexes (ATI) pre- and post instrumentation were compared. All the data were analyzed with SAS6.12 software package. RESULTS: Two Hero642 instruments fractured during preparation and none of the M(two) or rotary ProTaper instruments separated. The mean working time with Hero642 files was significantly longer than that with M(two) or ProTaper instruments (P<0.01).The change of curvature degree before and after instrumentation for three systems was statistically significant (P<0.05). And the difference of ATI for three systems was not significant (P>0.05). CONCLUSION: M(two) and ProTaper systems tested in this study are effective in shaping curved molar canals in extracted teeth.

The expression and role of stromal cell-derived factor-1alpha-CXCR4 axis in human dental pulp.

Recent reports have suggested that the stromal cell-derived factor (SDF)-1alpha-CXCR4 axis has a direct effect on stem and progenitor cell recruitment in muscle and neural tissue repair after injury. No information is available about SDF-1alpha or CXC chemokine receptor 4 (CXCR4) in dental tissues. The aim of this study was to assess the expression of SDF-1alpha and its receptor, CXCR4, in healthy or inflamed human dental pulp and to evaluate the effects of SDF-1alpha on dental pulp cells (DPCs) in both proliferation and migration in vitro. Immunohistochemical staining and reverse-transcription polymerase chain reaction detected weak expression of SDF-1alpha and CXCR4 in healthy dental pulp and strong expression of SDF-1alpha and CXCR4 in inflamed dental pulp. A methylthiazol tetrazolium assay showed that SDF-1alpha could not promote DPCs proliferation. A transmigration assay, however, indicated that SDF-1alpha enhanced DPCs migration, which could be abolished by anti-CXCR4 antibodies. Taken together, these results imply that the SDF-1alpha-CXCR4 axis may play a role in the recruitment of CXCR4-positive DPCs toward the damaged sites.

[Effect of quality of root canal obturation on the long-term results of root canal therapy].

PURPOSE: The purpose of this study was to analyze the quality of obturation affecting the long-term results of root canal therapy (RCT) by radiographic evaluation. METHODS: Teeth of RCT for 2 or more than 2 years were chosen, and periapical radiographs were taken with paralleling technique. The patients' age, gender, etiology, the time of therapy were recorded. The current apical periodontal status of these endodontically treated teeth were examined and recorded. The data were subjected to univariate and multivariate analysis with SPSS13.0 software package. RESULTS: This study investigated 215 cases with 376 endodontically treated teeth. The success rate was 54.79%. If counted by root canal, there were 513 root canals, the success rate was 61.4%. The quality of obturation including obturation position and obturation density affected significantly the results of root canal therapy (P<0.01). The ideal obturation position for successful treated canals was 0.5-2mm from the radiographic apex. The success rate was higher for a good obturation density, especially in the apical third. No statistically significant differences were found based on gender, age and obturation time. CONCLUSION: The quality of root canal obturation significantly affected the long-term results of root canal therapy.

In situ measurement of Cl- concentrations and pH at the reinforcing steel/concrete interface by combination sensors.

This paper presents an in situ, nondestructive method of monitoring Cl- concentrations and pH values at the steel/concrete interface. The Ag/AgCl electrodes prepared by the electrochemical anodization and the Ir/IrO2 electrodes prepared by thermal oxidation in carbonate served as Cl- concentration and pH sensors, respectively. The potentiometric response of the Ag/AgCl electrode to the logarithm of Cl- concentrations ranging from 1 x 10(-4) to 2 M in saturated Ca(OH)2 solution simulating the inner electrolytic medium of concrete shows good linearity. The Ir/IrO2 electrode also exhibits an ideal Nernstian response in the range of pH 1-14. The Ag/AgCl and Ir/IrO2 electrodes were combined into a multiplex Cl-/pH sensor, and the sensor was embedded in concrete close to the steel/concrete interface to realize an in situ and long-term measurement of Cl- concentrations and pH values. The results indicate that the combined sensor is robust and sensitive enough to in situ measure Cl- concentrations and pH quantitatively at the steel/concrete interface, which is of indispensable importance to the study of corrosion and protection of the steel in concrete.

[The influence of smear layer and different sealers on apical microleakage of root canals obturated with Ultrafil-3D system].

PURPOSE: To evaluate the sealing properties of Ultrafil-3D system with three different root canal sealers in absence or presence of smear layer. METHODS: 64 straight single-root anterior teeth were selected and root canals were instrumented. 60 teeth were divided into two groups with or without smear layer. Each group was then divided into three subgroups, three different sealers (AH-plus, Roekoseal, CRCS) were applied in each subgroup when the root canals were obturated with Ultrafil-3D system (using Firm set gutta-percha). Other 4 teeth were used as control. After dyed in 2% methyl blue for 5 days, all teeth were longitudinally split from mesiodistal surface into two parts. The linear length of dye was measured for apical microleakage. SAS6.04 software was used for statistical analysis. RESULTS: (1) The linear dye penetration was significantly higher in group A (CRCS) compared with that in group B (AH-plus) and in group C (Roekoseal) (P<0.05). (2) Whether the smear layer was absent or present, the apical microleakage had no significant difference when using gutta-percha of Ultrafil-3D system with the same sealer (P>0.05). CONCLUSION: Root-canal obturation with Ultrafil-3D gutta-percha can obtain better sealing ability when AH-plus or Roekoseal is applied as sealer. Removing the smear layer can not significantly reduce the apical microleakage.

[Comparison on the shaping ability of three different instruments in preparing curved molar canals].

OBJECTIVE: To study the changes of root canal curvatures and apical transportation index when the curved root canals were prepared by hand-use ProTaper, stainless steel K-files or nickel-titanium K-files. METHODS: Forty-five extracted molars, with the degree of root canal curvature from twenty to forty, were divided into fifteen sections in curvature sequence. After that, three canals of each section were randomly distributed to three different instrumentation groups. One group of them was prepared by hand-use ProTaper with crown-down technique. The other two groups were instrumented by stainless steel or nickel titanium K-files with modified step-back technique to working length. The standard digital radiographs were taken to record the profiles of root canals and the positions of the tips of the instruments. The change of curvature degree between pre- and post-instrumentation and the apical transportation indexes (ATI) among three groups were analyzed respectively using SAS statistical software. RESULTS: The change of curvature degree between pre- and post-instumentation for stainless steel K-files group was largest, and the ATI of stainless steel K-files group was significantly greater than that for nickel titanium K-files group (P < 0.05). The canals prepared by hand-use ProTaper was smallest in the change of curvature and ATI among the three groups (P < 0.01). CONCLUSION: When preparing curved molar canals, hand-use ProTaper with crown down technique can obtain better shaping effect and higher efficiency.

[Comparison of the effects of 5 irragant combinations on cleaning of anterior straight root canal walls].

PURPOSE: To evaluate the effect of 5 kinds of irrigant combinations on cleaning of anterior straight root canal walls. METHODS: 25 extracted human maxillary anterior teeth, with a single straight root were randomly divided into 5 groups. They were instrumented with K-files and conventional preparation technique. The irrigations were as follow: in group 1,the canals were irrigated with 1% NaOCl and 3% H2O2 in sequence during and after instrumentation.In group 2,the canals were irrigated with 1% NaOCl during instrumentation and after instrumentation being irrigated with 17% EDTA. In group 3,irrigation during and after instrumentation was accomplished using 17% EDTA and 1% NaOCl in sequence. In group 4,irrigation during instrumentation was accomplished using 17% EDTA and 1% NaOCl in sequence, and after instrumentation being irrigated with 17% EDTA.In group 5,the canals were irrigated with 17% EDTA, 1% Triton X-100 and 1% NaOCl in sequence during instrumentation and irrigated with 17% EDTA after instrumentation. The total amount of irrigant was 22ml and the irrigation time was 7 minutes in each root canal. The root was split longitudinally and 3 specimens in each group were evaluated regarding to the smear layer, debris and erosion of dentinal tubules with SEM at the coronal, middle and apical thirds. RESULTS: In group 1, typical amorphous smear layer and abundance of debris were seen on the wall of canals. In group 2, the smear layer was removed partly in coronal and middle thirds, but the apical surface of the canal walls were covered with a typical amorphous smear layer. Although irrigants of group 3 could remove smear layer effectively, it resulted in moderate erosion of dentinal tubules. In group 5, part of the smear layer was removed on the surface of coronal and middle thirds but abundance of debris were present on the surface at the apical levels. Severe erosion was noted on the root canal surfaces in this group. Irrigation of group 4 had the best result: it not only removed smear layer effectively ,but also had no erosion on dentinal tubules. CONCLUSION: Using the combination of 17% EDTA and 1% NaOCl can remove smear layer effectively and has no erosion on the dentinal tubules under the condition of strict time control and irrigation sequence. Supported by Phosphor Plan (No.01QB14025) of Science and Technology of Shanghai Municipality.