circUQCRC2 promotes asthma progression in children by activating the VEGFA/NF-κB pathway by targeting miR-381-3p.

This study targeted to explore circUQCRC2's role and mechanism in childhood asthma. A mouse model of ovalbumin-induced asthma was established to evaluate the effects of circUQCRC2 on childhood asthma in terms of oxidative stress, inflammation, and collagen deposition. The effects of circUQCRC2 on platelet-derived growth factor-BB (PDGF-BB)-induced smooth muscle cells (SMCs) were evaluated, the downstream mRNA of miRNA and its associated pathways were predicted and validated, and their effects on asthmatic mice were evaluated. circUQCRC2 levels were upregulated in bronchoalveolar lavage fluid of asthmatic mice and PDGF-BB-treated SMCs. Depleting circUQCRC2 alleviated tissue damage in asthmatic mice, improved inflammatory levels and oxidative stress in asthmatic mice and PDGF-BB-treated SMC, inhibited malignant proliferation and migration of SMCs, and improved airway remodeling. Mechanistically, circUQCRC2 regulated VEGFA expression through miR-381-3p and activated the NF-κB cascade. circUQCRC2 knockdown inactivated the NF-κB cascade by modulating the miR-381-3p/VEGFA axis. Promoting circUQCRC2 stimulates asthma development by activating the miR-381-3p/VEGFA/NF-κB cascade. Therefore, knocking down circUQCRC2 or overexpressing miR-381-3p offers a new approach to treating childhood asthma.

Hypericin nanoparticles for self-illuminated photodynamic cytotoxicity based on bioluminescence resonance energy transfer.

The purpose of this study was to investigate the self-sensitization of photosensitizer without an external light source to produce a photodynamic therapy (PDT) effect based on the principle of bioluminescence resonance energy transfer (PDT-BRET). First, we demonstrated that HeLa cells could efficiently express firefly luciferase (FLase) after the firefly luciferase gene was transfected with the FLase-gene plasmid (FLase-GP), and proved that FLase could act on the substrate firefly D-luciferin (FLuc) to produce photons. The generated photons activate the photosensitizer hypericin (Hyp) and induce cytotoxicity. Then, we successfully prepared carboxymethyl chitosan-modified poly(lactic-co-glycolic acid) nanoparticles (CPNPs) loaded with FLuc (FLuc-CPNPs) and with loaded Hyp (Hyp-CPNPs). Their physicochemical and pharmaceutical characteristics indicated that they were an excellent drug delivery system. Characterization of the biological effects showed that they could be located in the mitochondrial, had higher ROS generation and stronger cytotoxicity. In vivo results also showed that PDT-BRET was as effective as classic PDT. PDT-BRET and the related drug delivery system are expected to become a new platform for anticancer therapy.

Collagenous gastritis in a young Chinese woman: A case report.

BACKGROUND: Collagenous gastritis (CG) is a rare condition whose pathogenesis may be related to immune abnormalities. We report a case of CG from China. CASE SUMMARY: A 24-year-old woman presented with recurrent abdominal distension and discomfort for 3 mo. Upper gastrointestinal endoscopy found diffuse nodular elevation-depression changes in the mucosa of the entire gastric corpus. Endoscopic ultrasound showed predominant involvement of the lamina propria and submucosa, and computed tomography imaging showed mild enhancement of the gastric wall. Pathological histology revealed that the thickness of the subepithelial collagen band was about 40 µm, and the Masson trichrome staining result was positive and the Congo red staining result was negative. This case is consistent with the child-adolescent type of CG. CONCLUSION: Serum pepsinogen I, pepsinogen II, pepsinogen I/II ratio, and gastrin-17 may be potential non-invasive monitoring markers. Currently, treatments for CG vary, and the likely prognosis is unknown. Individual cases of gastric cancer in patients with CG have been reported.

Detection of vertical root fracture using cone beam computed tomography: report of two cases.

Vertical root fractures (VRFs) often occur in endodontically treated teeth and in patients older than 40 years of age. However, VRFs in teeth without endodontic treatment are relatively uncommon. VRFs are difficult to diagnose as the symptoms are non-specific or often delayed. The most common radiographic findings are thickening of the periodontal ligament, deep, localized, vertical bone loss, and localized periradicular bone loss. The explicit feature for detecting VRFs is direct visualization of a radiolucent fracture line on radiographs. However, the fracture line can be difficult to directly visualize in conventional diagnostic methods such as periapical radiographs. If unrecognized, VRFs can lead to frustration and inappropriate endodontic treatment. The two cases reported here demonstrate that the use of cone beam computed tomography (CBCT) successfully diagnoses VRFs on teeth without representative clinical and periapical radiographic findings. The clear fracture line can be discerned from the images of CBCT. Thus, CBCT imaging is useful in rapid diagnosis of VRFs and designing of further treatment.

Domain Adaption via Feature Selection on Explicit Feature Map.

In most domain adaption approaches, all features are used for domain adaption. However, often, not every feature is beneficial for domain adaption. In such cases, incorrectly involving all features might cause the performance to degrade. In other words, to make the model trained on the source domain work well on the target domain, it is desirable to find invariant features for domain adaption rather than using all features. However, invariant features across domains may lie in a higher order space, instead of in the original feature space. Moreover, the discriminative ability of some invariant features such as shared background information is weak, and needs to be further filtered. Therefore, in this paper, we propose a novel domain adaption algorithm based on an explicit feature map and feature selection. The data are first represented by a kernel-induced explicit feature map, such that high-order invariant features can be revealed. Then, by minimizing the marginal distribution difference, conditional distribution difference, and the model error, the invariant discriminative features are effectively selected. This problem is NP-hard to be solved, and we propose to relax it and solve it by a cutting plane algorithm. Experimental results on six real-world benchmarks have demonstrated the effectiveness and efficiency of the proposed algorithm, which outperforms many state-of-the-art domain adaption approaches.

Poly[tetra-aqua-µ(4)-bromido-di-µ(2)-bromido-µ(2)-hydroxido-di-µ(3)-iso-nicotinato-tetra-µ(2)-isonicotinato-tetra-copper(I)dithulium(III)].

A new thulium(III)-copper(I) heterometallic coordination polymer, [Cu(4)Tm(2)Br(3)(C(6)H(4)NO(2))(6)(OH)(H(2)O)(4)](n), has been prepared by a hydro-thermal method. The Tm and both Cu atoms lie on mirror planes. The Tm atom is seven-coordinate with a capped distorted trigonal-prismatic coordination geometry, while the Cu atoms adopt trigonal CuBrN(2) and tetra-hedral CuBr(3)N coordination modes, respectively. The Cu atom in the trigonal coordination environment is disordered over two sites of equal occupancy. The crystal structure is constructed from two distinct units of dimeric [Tm(2)(µ(2)-OH(IN)(6)(H(2)O)(4)] cores (IN = isonicotinate) and one-dimensional inorganic [Cu(4)Br(3)](n) chains, which are linked together, forming heterometallic Cu-halide-lanthanide-organic layers.

Effect of occlusal slope related to uneven attrition on root stress distribution and potential fracture.

BACKGROUND/PURPOSE: Severely uneven occlusal attrition is thought to play an important role in the occurrence of spontaneous vertical root fracture (VRF), a frequent problem among Chinese people. This study evaluated the influence of occlusal slope related to uneven attrition on the root stress condition. MATERIALS AND METHODS: A finite element model of the mandibular first molar was established. Two different occlusal slope patterns were simulated in 5 models: (A) sound tooth, (B) 0.5-1.5 mm and (C) 2-3 mm attrition increased buccally, and (D) 0.5-1.5 mm and (E) 2-3 mm attrition increased distally. A static load of 200 N was applied vertically or angled at 45° to the longitudinal axis. The von Mises stress was evaluated. RESULTS: Under vertical loading, more stress was transferred from the cervical to the middle root with attrition, especially the mesial root, while stress declined with attrition under oblique loading. Stress was mainly distributed in the buccal surface and mesial root with vertical loading, or in the lingual surface and distal root with oblique loading. The maximum von Mises with oblique loading was significantly higher than with vertical loading. CONCLUSION: Uneven occlusal attrition made the middle of the mesial root bear more stress, increasing fracture risk under vertical load. This finding suggests that timely restoration of the sloped occlusal morphology in teeth with severe attrition should be recommended to prevent VRFs. Lateral loading was not a risk factor of typical vertical root fractures, but the high stress could cause distal root cervical fracture.

Poly[aqua(mu3-benzene-1,2-dicarboxylato)bis(mu3-hydroxido)bis(mu2-isonicotinato)dierbium(III) monohydrate] and the thulium analogue.

The two isomorphous lanthanide coordination polymers, {[Ln(2)(C(6)H(4)NO(2))(2)(C(8)H(4)O(4))(OH)(2)(H(2)O)].H(2)O}(n) (Ln = Er and Tm), contain two crystallographically independent Ln ions which are both eight-coordinated by O atoms, but with quite different coordination environments. In both crystal structures, adjacent Ln atoms are bridged by mu(3)-OH groups and carboxylate groups of isonicotinate and benzene-1,2-dicarboxylate ligands, forming infinite chains in which the Er...Er and Tm...Tm distances are in the ranges 3.622 (3)-3.894 (4) and 3.599 (7)-3.873 (1) A, respectively. Adjacent chains are further connected through hydrogen bonds and pi-pi interactions into a three-dimensional supramolecular framework.

Efficacy and safety of puerarin injection in curing acute ischemic stroke: A meta-analysis of randomized controlled trials.

BACKGROUND: Previous studies indicated that the puerarin injection has been widely employed in China for the treatment of acute ischemic stroke. We aim to evaluate the efficacy and safety of the puerarin injection for the treatment of acute ischemic stroke. METHODS: A systematic literature search was performed in PUBMED, EMBASE, SPRINGER LINK, Scopus, Cochrane Library, China National Knowledge Infrastructure (CNKI), VIP Journals Database, Wanfang database and the China Biological Medicine database before November 2016, randomized controlled clinical trials (RCTs) of puerarin injection treating acute ischemic stroke were included. In addition, we searched reference lists of relevant retrieved articles. Two authors extracted data independently. The effective rate, the neurologic deficit score, the blood rheology indexes, and fibrinogen were assessed and analyzed by the Review Manager 5.3 software. The continuous variables were expressed as MD with 95% CI and dichotomous data used RR or ORs. Adverse reactions related to the puerarin injection were also examined. RESULTS: Thirty-five RCTs with a total of 3224 participants were identified in the meta-analysis. The combined results of 32 trials indicated that the puerarin injection was better than control drugs at the clinical effective rate (RR 1.22, 95% CI 1.17 to 1.28, P < 0.001) and 16 studies showed the neurological deficit was significantly improved (MD -3.69, 95% CI -4.67 to -2.71, P < 0.001); the hemorheology index and fibrinogen were much lower with the puerarin injection when compared with western conventional medicines (WCM) or other control drugs (the whole blood viscosity: MD -0.89, 95% CI -1.37 to -0.41, P < 0.001; the HCT: MD -0.04, 95% CI -0.06 to -0.02, P < 0.001; the fibrinogen: MD -0.64, 95% CI -0.96 to -0.31, P < 0.001). Eleven trials reported that the adverse reactions related to the puerarin injection included facial flushing, dizziness, vomiting, nausea, and other mild gastrointestinal discomfort and allergic reaction. No serious adverse drug reactions were reported. CONCLUSIONS: Puerarin injection may be more effective and relatively safe in clinic for treating acute ischemic stroke. However, the current evidence is insufficient due to the poor methodological quality and lack of adequate safety data. Further RCTs are required to examine its efficacy.

A Fast Reduced Kernel Extreme Learning Machine.

In this paper, we present a fast and accurate kernel-based supervised algorithm referred to as the Reduced Kernel Extreme Learning Machine (RKELM). In contrast to the work on Support Vector Machine (SVM) or Least Square SVM (LS-SVM), which identifies the support vectors or weight vectors iteratively, the proposed RKELM randomly selects a subset of the available data samples as support vectors (or mapping samples). By avoiding the iterative steps of SVM, significant cost savings in the training process can be readily attained, especially on Big datasets. RKELM is established based on the rigorous proof of universal learning involving reduced kernel-based SLFN. In particular, we prove that RKELM can approximate any nonlinear functions accurately under the condition of support vectors sufficiency. Experimental results on a wide variety of real world small instance size and large instance size applications in the context of binary classification, multi-class problem and regression are then reported to show that RKELM can perform at competitive level of generalized performance as the SVM/LS-SVM at only a fraction of the computational effort incurred.

A Fast SVD-Hidden-nodes based Extreme Learning Machine for Large-Scale Data Analytics.

Big dimensional data is a growing trend that is emerging in many real world contexts, extending from web mining, gene expression analysis, protein-protein interaction to high-frequency financial data. Nowadays, there is a growing consensus that the increasing dimensionality poses impeding effects on the performances of classifiers, which is termed as the "peaking phenomenon" in the field of machine intelligence. To address the issue, dimensionality reduction is commonly employed as a preprocessing step on the Big dimensional data before building the classifiers. In this paper, we propose an Extreme Learning Machine (ELM) approach for large-scale data analytic. In contrast to existing approaches, we embed hidden nodes that are designed using singular value decomposition (SVD) into the classical ELM. These SVD nodes in the hidden layer are shown to capture the underlying characteristics of the Big dimensional data well, exhibiting excellent generalization performances. The drawback of using SVD on the entire dataset, however, is the high computational complexity involved. To address this, a fast divide and conquer approximation scheme is introduced to maintain computational tractability on high volume data. The resultant algorithm proposed is labeled here as Fast Singular Value Decomposition-Hidden-nodes based Extreme Learning Machine or FSVD-H-ELM in short. In FSVD-H-ELM, instead of identifying the SVD hidden nodes directly from the entire dataset, SVD hidden nodes are derived from multiple random subsets of data sampled from the original dataset. Comprehensive experiments and comparisons are conducted to assess the FSVD-H-ELM against other state-of-the-art algorithms. The results obtained demonstrated the superior generalization performance and efficiency of the FSVD-H-ELM.

Occurrence of Dentinal Microcracks in Severely Curved Root Canals with ProTaper Universal, WaveOne, and ProTaper Next File Systems.

INTRODUCTION: This study aims to compare the incidence of dentinal microcracks produced by the ProTaper Universal (Dentsply Maillefer, Ballaigues, Switzerland), WaveOne (Dentsply Maillefer), and ProTaper Next (Dentsply Maillefer) file systems during root canal procedures in severely curved canals using a dyeing technique. METHODS: Sixty extracted human molars with 25° to 40° root curvatures were divided into 3 groups of 20 canals each. ProTaper Universal, WaveOne, and ProTaper Next file systems were used for root canal procedures. Untreated root canals of 60 molars served as negative controls. After preparation, all roots were stained with 1% methylene blue for 24 hours. Roots were then sectioned at the most curved plane and 2 mm below and above the most curved plane with a low-speed saw under cold water. A stereomicroscope was used to inspect dentinal microcracks at 60× magnification, and differences between these 3 instrument groups were analyzed using the chi-square test. RESULTS: The ProTaper Next system induced less complete and incomplete dentinal microcracks compared with the ProTaper Universal and WaveOne systems (P < .05), and there were no significant differences between the ProTaper Universal and WaveOne systems (P > .05). The ProTaper Universal and WaveOne systems induced significantly more complete cracks in the plane 2 mm above the most curved plane compared with either of the other 2 planes (P = .004). CONCLUSIONS: The ProTaper Next system induces less dentinal microcracks during root canal procedures in severely curved root canals compared with the ProTaper Universal and WaveOne systems.

Cross-person activity recognition using reduced kernel extreme learning machine.

Activity recognition based on mobile embedded accelerometer is very important for developing human-centric pervasive applications such as healthcare, personalized recommendation and so on. However, the distribution of accelerometer data is heavily affected by varying users. The performance will degrade when the model trained on one person is used to others. To solve this problem, we propose a fast and accurate cross-person activity recognition model, known as TransRKELM (Transfer learning Reduced Kernel Extreme Learning Machine) which uses RKELM (Reduced Kernel Extreme Learning Machine) to realize initial activity recognition model. In the online phase OS-RKELM (Online Sequential Reduced Kernel Extreme Learning Machine) is applied to update the initial model and adapt the recognition model to new device users based on recognition results with high confidence level efficiently. Experimental results show that, the proposed model can adapt the classifier to new device users quickly and obtain good recognition performance.

Evaluation of x-ray projection angulation for successful radix entomolaris diagnosis in mandibular first molars in vitro.

INTRODUCTION: The aim of this study was to evaluate the radiographic features of permanent three-rooted mandibular first molars with radix entomolaris (RE), investigate the correlation between anatomical classification and radiographic type of RE, and to determine the most effective horizontal beam angulation for the diagnosis of RE. METHODS: Twenty-five extracted mandibular first permanent molars with RE were selected for taking radiographs in 7 horizontal angulations. By using set criteria, 3 evaluators assessed morphologic and radiographic features of the RE and optimum beam angulation for RE diagnosis. Intraexaminer variability was analyzed with Cohen kappa test. RESULTS: Three types of curvature of RE presented with 3 distinct types of typical radiographic appearance on orthoradial radiographs. We classified the radiographic features of RE into 3 types, as follows: type i, type ii, and type iii. Seven teeth showed type i radiographic features. Zero-degree, 5-degree, 15-degree, and 25-degree radiographs were significantly better than the mesially angulated -15-degree and -25-degree images for detecting the type i RE images (P < .05). Fifteen-degree, 25-degree, and -25-degree horizontal beam angulations showed significantly more accurate diagnoses of RE in 8 type ii images (P < .05). Only 25-degree-angled radiographs were found to have a high diagnostic yield of type iii RE images (P < .05). A significant correlation was found between morphologic and radiographic types of RE (P < .05, contingency coefficient = 0.473). Intraexaminer variability was low, with kappa = 0.68 (P < .05). CONCLUSIONS: RE presents 3 types of typical radiographic features on orthoradial radiographs. Additional 25-degree mesial horizontal-angled radiographs are essential for preoperative identification and evaluation of RE, especially types ii and iii.

[Anatomic study of canal isthmuses of mandibular permanent incisors by micro-CT].

OBJECTIVE: To investigate the anatomic feature of the canal isthmus of mandibular permanent incisors by Micro-CT. METHODS: 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. RESULTS: 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. CONCLUSION: 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.

A cone-beam computed tomography study of maxillary first permanent molar root and canal morphology in a Chinese population.

AIM: This study evaluated root and canal morphology of permanent maxillary first molars in a Chinese population using cone-beam computed tomography scanning. METHODOLOGY: The sample included 775 cone-beam computed tomography images of maxillary first molars; 627 of the subjects had unilateral qualifying molars and 74 had bilateral qualifying molars. The following observations were made: (1) frequency of root and canal numbers, (2) frequency of additional canals in the mesiobuccal root by sex, age, and tooth position, and (3) unilateral and bilateral occurrence of additional canals in the mesiobuccal root. RESULTS: Fused roots were present in 2.71% of unilateral qualifying molars. Multiple canals were present in the following frequencies: two canals in 0.31%, three canals in 47.21%, four canals in 50.40%, five canals in 1.75%, and six canals in 0.31% of teeth. Additional canals were detected in 52.24% of mesiobuccal roots, 1.12% of distobuccal roots, and 1.76% of palatal roots. Patients aged 20 to 30 years showed a higher prevalence of additional mesiobuccal root canals. This prevalence did not differ with sex and tooth position. Most (71.11%) of the additional mesiobuccal root canals in subjects with bilateral qualifying molars were symmetric. CONCLUSION: Cone-beam computed tomography scanning is an effective method for studying external and internal dental morphology. The root and canal configurations of maxillary first molars in this Chinese population were consistent with previously reported data. More attention should be given to the detection of additional canals in patients between 20 and 30 years of age. These data may facilitate successful endodontic treatment.

Evaluation of the root and canal morphology of mandibular first permanent molars in a western Chinese population by cone-beam computed tomography.

INTRODUCTION: The purpose of this study was to evaluate the root and canal morphology of mandibular first permanent molars in a western Chinese population by using cone-beam computed tomography (CBCT). METHODS: In this study, 558 samples were examined by CBCT. Details of sex, tooth position, the number of roots and canals, and the canal configuration were recorded. The root canal configuration was categorized and compared according to Vertucci's criteria. RESULTS: Overall, 51.4% of the mandibular first permanent molars examined had four canals, and 25.8% had a separate distolingual root. In 48.1% of these, the fourth canal was in the separate distolingual root. In the two-rooted mandibular first permanent molars, 93.9% of the mesial root canals were of type IV, and 62.9% of the distal root canals were of type I. In the three-rooted samples, 94.4% of the mesial root canals were of type IV, and 98.6% of the distobuccal and 100% of the distolingual root canals were of type I. In addition, there was a higher incidence of three-rooted mandibular first permanent molars on the left side than on the right, but this relationship was not significantly correlated with sex. CONCLUSIONS: Mandibular first permanent molars commonly have four canals and a higher prevalence for a separated distolingual canal in a western Chinese population.

Distribution of Porphyromonas gingivalis fimA genotypes in chronic apical periodontitis associated with symptoms.

INTRODUCTION: Porphyromonas gingivalis (P. gingivalis) is an anaerobic bacterium involved in root canal infections whose fimbriae are classified into six genotypes (types I-V and Ib) based on nucleotide sequence. Accumulated evidence suggests there is significant association between P. gingivalis and some clinical symptoms of periodontal diseases. The present study aims to determine the prevalence of P. gingivalis fimA genotypes in apical periodontitis and to investigate the correlation between P. gingivalis fimA genotypes and clinical symptoms. METHODS: Samples were obtained from 158 infected root canals with apical periodontitis. DNA was extracted and analyzed with a polymerase chain reaction-based identification assay. Odds ratios, 95% confidence intervals, and contingency coefficient were calculated for associating the fimA-specific genes with clinical symptoms. RESULTS: P. gingivalis was detected in 39.9% of the inflected root canal samples and was found in 44.5% of P. gingivalis-positive specimens with symptoms. Types II (69.4%) were the most frequent in the symptomatic cases followed by type IV (32.7%). The occurrence of type I (64.3%) was significantly higher than any other genotypes in the asymptomatic apical periodontitis, whereas type II and type Ib were not identified. Statistical analysis revealed that the occurrences of types II, IV, and Ib fimA were associated with greater risk of clinical signs (swelling, sinus tract, or intracanal exudates) than type I. CONCLUSIONS: Results from this study reinforce the association between P. gingivalis-specific fimA genotypic clones and apical periodontitis, indicating that fimA genotypes (types II, IV, and Ib) were related to the etiology of symptomatic periradicular diseases.

Radiographic investigation of frequency and degree of canal curvatures in Chinese mandibular permanent incisors.

Accurate knowledge of root canal curvature is a critical factor in successful root canal procedures. The objective of this study was to determine the degree of root canal curvature and the frequency of curvature identified in different radiographic views in permanent incisors from a Chinese population. The curvature of canals from 299 permanent mandibular incisors was investigated by measuring the angle, the radius of curvature, and the length of the curved part of the canals. These measurements were taken by inserting size 10 K-files into the canals and taking radiographs of the tooth-file assembly from both facial and proximal views by using a standardized parallel technique. All radiographs were analyzed with a computerized digital image processing system. Statistical analysis was performed with analysis of variance test at alpha = .05. Of the 299 teeth examined, 252 (84.3%) were curved, and 125 (41.8%) of the teeth had secondary curvature. Curvature was most frequently detected in the proximal views rather than in the facial lingual views (P < .05). The highest curvature among all samples tested was 44 degrees primary curvature and 36 degrees secondary curvature. The maximum and minimum radii of curvature for the sample set were 54.61 and 1.55 mm, respectively. The mean value of the radius of secondary curvature seen in proximal views was significantly less than that of the primary ones (P < .05). The length of the curved parts of canals measured maximum and minimum values of 14 and 0.33 mm, respectively. It is suggested that the canal curvature can start at either the middle third or apical third of the tooth.