Safety evaluation of Tibetan medicine Qishiwei Zhenzhu Pills based on serum pharmacochemistry and network pharmacology / 中国中药杂志

To explore the mechanism of the active ingredients of Qishiwei Zhenzhu Pills in inhibiting the hepatorenal toxicity of the zogta component based on serum pharmacochemistry and network pharmacology, thereby providing references for the clinical safety application of Qishiwei Zhenzhu Pills. The small molecular compounds in the serum containing Qishiwei Zhenzhu Pills of mice were identified by high performance liquid chromatography-tandem mass spectrometry(HPLC-MS/MS). Then, by comprehensively using Traditional Chinese Medicines Systems Pharmacology(TCMSP), High-throughput Experiment-and Reference-guided Database(HERB), PubChem, GeneCards, SuperPred, and other databases, the active compounds in the serum containing Qishiwei Zhenzhu Pills were retrieved and their action targets were predicted. The predicted targets were compared with the targets of liver and kidney injury related to mercury toxicity retrieved from the database, and the action targets of Qishiwei Zhenzhu Pills to inhibit the potential mercury toxicity of zogta were screened out. Cytoscape was used to construct the active ingredient in Qishiwei Zhenzhu Pills-containing serum-action target network, and STRING database was used to construct the protein-protein interaction(PPI) network of intersection targets. The Gene Ontology(GO) and Kyoto Encyclopedia of Genes and Genomes(KEGG) enrichment analyses were carried out on the target genes by the DAVID database. The active ingredient-target-pathway network was constructed, and the key ingredients and targets were screened out for molecular docking verification. The results showed that 44 active compounds were identified from the serum containing Qishiwei Zhenzhu Pills, including 13 possible prototype drug ingredients, and 70 potential targets for mercury toxicity in liver and kidney were identified. Through PPI network topology analysis, 12 key target genes(HSP90AA1, MAPK3, STAT3, EGFR, MAPK1, APP, MMP9, NOS3, PRKCA, TLR4, PTGS2, and PARP1) and 6 subnetworks were obtained. Through GO and KEGG analysis of 4 subnetworks containing key target genes, the interaction network diagram of active ingredient-action target-key pathway was constructed and verified by molecular docking. It was found that taurodeoxycholic acid, N-acetyl-L-leucine, D-pantothenic acid hemicalcium, and other active ingredients may regulate biological functions and pathways related to metabolism, immunity, inflammation, and oxidative stress by acting on major targets such as MAPK1, STAT3, and TLR4, so as to inhibit the potential mercury toxicity of zogta in Qishiwei Zhenzhu Pills. In conclusion, the active ingredients of Qishiwei Zhenzhu Pills may have a certain detoxification effect, thus inhibiting the potential mercury toxicity of zogta and playing a role of reducing toxicity and enhancing effect.

Clinical Observation on Orthopedics No.1 Prescription Combined with Celecoxib in Treating Knee Osteoarthritis with Middle Stage of Cold-dampness Syndrome / 中国实验方剂学杂志

Objective:To study the clinical efficacy of orthopedics No.1 prescription combined with celecoxib in the treatment of knee osteoarthritis （KOA） with middle stage of cold-dampness syndrome and investigate its effect on serum cytokines levels. Method:The 72 patients were randomly divided into control group and observation group， with 36 cases each. Patients in both groups were given basic treatment with oral celecoxib capsules （0.2 g/ time， 1 time/day）. On the basis of western medicine treatment， patients in observation group were treated with orthopedics No.1 prescription decoction-free granules by fumigation， 1 bag/time， 1 time/day， 5 times/week. Both groups received treatment for 4 weeks. The visual analog pain score （VAS）， American knee society knee score （KSS）， serum interleukin-1<italic>β </italic>（IL-1<italic>β</italic>）， tumor necrosis factor-<italic>α </italic>（TNF-<italic>α</italic>）， and transforming growth factor-<italic>β</italic>₁（TGF-<italic>β</italic>₁） levels were observed before and after treatment， and their clinical efficacy was evaluated. Result:After treatment， VAS score significantly decreased in both groups （<italic>P</italic><0.01）， and KSS score significantly increased （<italic>P</italic><0.01）， with better clinical effect in observation group. After treatment， serum IL-1<italic>β</italic> and TNF-<italic>α</italic> levels decreased significantly in both groups （<italic>P</italic><0.01）， and the levels in observation group were lower than those in control group after treatment （<italic>P</italic><0.05）. TGF<italic>-β</italic>₁content was significantly higher than that before treatment in two groups （<italic>P</italic><0.01）. Conclusion:Orthopedics No.1 prescription combined with celecoxib for the treatment of KOA with middle stage of cold-dampness syndrome can effectively relieve the clinical symptoms of patients with KOA， improve joint function， improve quality of life， reduce the contents of inflammatory factors IL-1<italic>β</italic> and TNF-<italic>α</italic> in serum， and increase the expression of TGF-<italic>β</italic>₁ level.

Effect of Zishenwan on Pyroptosis and Epithelial-Mesenchymal Transition of Renal Tubular Epithelial Cells in Diabetic Nephropathy Mice / 中国实验方剂学杂志

Objective:To study the efficacy and mechanism of Zishenwan （ZSW） against pyroptosis and epithelial-mesenchymal transition （EMT） of renal tubular epithelial cells in diabetic nephropathy （DN） mice， so as to provide evidence for the treatment of DN with ZSW. Method:The <italic>db/db</italic> mice with spontaneous diabetes were randomly divided into the model group， dapagliflozin （1.0 mg·kg^-1） group， and high-， medium-， and low-dose （6.0， 3.0， 1.5 g·kg^-1） ZSW groups. The non-diabetic <italic>db/m</italic> mice were classified into the normal group. The ones in the model and normal groups were given an equal volume of deionized water by gavage， while those in the other groups were intervened with the corresponding drugs for 12 weeks. The fasting blood glucose （FBG） level was tested at tail vein once every two weeks. The levels of urine albumin-creatinine ratio （ACR）， <italic>β</italic>-N-acetyl-D-glucosaminidase （NAG）， and cystatin C （CysC） were detected once every four weeks. After 12 weeks of administration， the blood sampled from eyeballs was used for measuring the blood urea nitrogen （BUN） and serum creatinine （SCr）. The pathological changes in renal tissues were observed by light microscopy and transmission electron microscopy. The expression of EMT markers in the renal tubular epithelium was analyzed by immunohistochemistry （IHC）. The in situ terminal end-labeling （TUNEL） staining was conducted to analyze the nuclear damage of renal tubular epithelial cells. The protein and mRNA expression levels of EMT markers， nucleotide-binding oligomerization domain-like receptor protein 3 （NLRP3） inflammasome and pyroptosis-related inflammatory cytokines in renal tissues were separately assayed by Western blot and Real-time fluorescence quantitative polymerase chain reaction（Real-time PCR）. Result:Compared with the normal group， the model group displayed significantly increased FBG， BUN， serum SCr， ACR， NAG， and CysC （<italic>P</italic><0.01）， impaired renal tissues， altered EMT marker expression intensities and levels （<italic>P</italic><0.01）， and elevated TUNEL-positive rate and protein and mRNA expression levels of pyroptosis-related inflammatory cytokines and NLRP3 inflammasome （<italic>P</italic><0.01）. Compared with the model group， ZSW and dapagliflozin significantly decreased the levels of FBG， BUN， serum SCr， ACR， NAG， and CysC （<italic>P</italic><0.01）， relieved the pathological injuries in renal tissues， changed the EMT marker expression intensities （<italic>P</italic><0.01） and protein and mRNA expression levels （<italic>P</italic><0.05， <italic>P</italic><0.01）， and down-regulated the TUNEL-positive rate （<italic>P</italic><0.01） of renal tubular epithelial cells as well as the protein and mRNA expression levels of pyroptosis-related inflammatory cytokines （<italic>P</italic><0.01） and NLRP3 inflammasome （<italic>P</italic><0.05， <italic>P</italic><0.01）. Conclusion:ZSW alleviates DN possibly by inhibiting pyroptosis and EMT in renal tubular epithelial cells.

Endodontic bacteria from primary and persistent endodontic lesions in Chinese patients as identified by cloning and 16S ribosomal DNA gene sequencing / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Few literatures pertain to the 16S ribosomal DNA (16S rDNA) analysis of bacteria contributing to primary and persistent endodontic lesions, with no information available for the Chinese population. As such, we investigated endodontic bacteria associated with primary and persistent endodontic lesions in adult Chinese patients living in Beijing, China using 16S rDNA gene sequencing techniques.</p><p><b>METHODS</b>Endodontic microbial samples were obtained from fourteen adult Chinese patients and subjected to DNA extraction. Pllymerase chain reaction (PCR) products were cloned and 100 clones from each generated library were randomly selected. Purified plasmid DNA with 16S rDNA gene inserts was sequenced, and the sequences were searched against GenBank databases using the BLASTN algorithm. Only significant identification with the highest-scored BLAST result and 99% minimum similarity was considered for phylotyping.</p><p><b>RESULTS</b>More than 150 taxa were obtained. Primary endodontic infection was mainly associated with Burkholderia cepacia, Actinomyces, Aranicola spp. and Streptococcus sanguinis, whilst Burkholderia cepacia was predominant in the persistent endodontic infections.</p><p><b>CONCLUSION</b>There is a difference in the species profile associated with endodontic infections of Chinese patients living in Beijing in comparison to other geographical or ethnic reports.</p>

Prevalence of Enterococcus faecalis in saliva and filled root canals of teeth associated with apical periodontitis / 国际口腔科学杂志·英文版

To investigate the prevalence of Enterococcus faecalis in saliva and filled root canals of patients requiring endodontic retreatment for apical periodontitis. Patients with apical periodontitis who were referred for endodontic retreatment were examined. The type and quality of the restoration, symptoms, quality of obturation were recorded. During retreatment, an oral rinse sample and root canal sample were cultured using brain-heart infusion agar and bile esculinazide agar to select for E. faecalis. The 16S rRNA technique was used to identify E. faecalis. A total of 32 women and 22 men (mean age: 38 years; s.d.: 11 years) and 58 teeth were studied. The prevalence of E. faecalis was 19% in the saliva and 38% in the root canals. The odds that root canals harbored E. faecalis were increased if the saliva habored this bacterium (odds ratio=9.7; 95% confidence interval=1.8-51.6; P<0.05). Teeth with unsatisfactory root obturation had more cultivable bacterial species in root canals than teeth with satisfactory root obturation (P<0.05). E. faecalis is more common in root canals of teeth with apical periodontitis than in saliva. The prevalence of E. faecalis in root canals is associated with the presence of E. faecalis in saliva.

Malocclusions in Xia Dynasty in China / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>The prevalence of malocclusion in modern population is higher than that in the excavated samples from the ancient times. Presently, the prevalence of juvenile malocclusion in the early stage of permanent teeth is as high as 72.92% in China. This study aimed to observe and evaluate the prevalence and severity of malocclusions in a sample of Xia Dynasty in China, and to compare these findings with the modern Chinese population.</p><p><b>METHODS</b>The material consisted of 38 male and 18 female protohistoric skulls of Xia Dynasty 4000 years ago. Of 86 dental arches, 29 cases had the jaw relationships. Tooth crowding, diastema, individual tooth malposition and malocclusion were studied.</p><p><b>RESULTS</b>Of the samples, 23.3% showed tooth alignment problems including crowding (8.1%), diastema (9.3%), and individual tooth malposition (5.8%). The prevalence of malocclusion was 27.6%, mainly presented as Angle Class I.</p><p><b>CONCLUSIONS</b>It is indicated that over thousands of years from Neolithic Age (6000 - 7000 years ago) to Xia Dynasty (4000 years ago), the prevalence of malocclusion did not change significantly. The prevalence of malocclusion of Xia Dynasty samples was much lower than that of modern population.</p>

Receptor activator of nuclear factor kappa B ligand and osteoprotegerin expression in chronic apical periodontitis: possible association with inflammatory cells / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Receptor activator of nuclear factor kappa B (NF-κB) ligand (RANKL) and osteoprotegerin (OPG) have been recently shown to play important roles in bone resorption. The aim of this study was to investigate the possible association between the expression of bone resorption regulators (RANKL and OPG) and inflammatory cell infiltration in chronic apical periodontitis.</p><p><b>METHODS</b>The samples of chronic periapical lesions (n = 40) and healthy periapical tissues (n = 10) were examined for immunohistochemical analysis of RANKL and OPG. Lesion samples were further analyzed for the inflammatory infiltration condition. The inflammatory cell infiltration was scored in relation to immunohistochemical reactivity for CD3, CD20 and CD68.</p><p><b>RESULTS</b>The number of RANKL-positive cells and the ratio of RANKL/OPG in chronic apical periodontitis were significantly higher than those in healthy periapical tissues (P < 0.001). The number of RANKL-positive cells was higher in lesions with severe inflammatory infiltration than in those with light inflammatory infiltration (P < 0.05). Significantly increased RANKL expression was found with T lymphocytes (CD3(+)), macrophages (CD68(+)) and B lymphocytes (CD20(+)) infiltration (P < 0.05). No association was found between the ratio of RANKL/OPG and inflammatory cell infiltration.</p><p><b>CONCLUSIONS</b>RANKL expression was increased with T, B lymphocytes and macrophages infiltration, respectively in chronic periapical lesions. RANKL appears to be closely related to periapical inflammatory infiltrates. The relative ratio of RANKL/OPG may be a key determinant of RANKL-mediated bone resorption.</p>

Root resection by Er:YAG laser: a scanning electron microscope study / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To compare the difference of the surface of root resection by Er:YAG laser, ultrasonic or high-speed handpiece with scanning electron microscope (SEM), and to evaluate the possibility of using Er:YAG laser on the root resection in clinical application.</p><p><b>METHODS</b>Thirty maxillary central incisors were divided into three groups (Er:YAG laser group, ultrasonic group, high-speed handpiece group), and the root resection were made at root tip 3 mm with Er:YAG laser, ultrasonic instrument or long needle diamond bur according to grouping. The surface of the root resection by SEM in the aspects of debris, smear layer, opened dentinal tubules, cracks and ablation characteristics were compared.</p><p><b>RESULTS</b>The examination revealed that Er:YAG laser group and ultrasonic group had no or little debris and smear layer and with opened dentinal tubules. High-speed handpiece group had great amount of debris and smear layer and without opened dentinal tubules. Cracks were observed in ultrasonic group and high-speed handpiece group, no in Er:YAG laser group. There were ablation characteristics in ultrasonic group and high-speed handpiece group, but no in Er:YAG laser group.</p><p><b>CONCLUSION</b>From the morphological aspect, Er:YAG laser has much more advantage than ultrasonic instrument and diamond bur for the root resection.</p>

Deformation evaluation of ProTaper nickel-titanium rotary instruments in curved canals instrumentation in vitro / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the deformation of ProTaper rotary instruments using in root canals of different curvature in vitro.</p><p><b>METHODS</b>Extracted first mandibular molars were divided into two experimental groups according to the curvature of mesial buccal canals: group A with moderate curvature and group B with severe curvature. Only the mesial buccal canals of all these teeth were prepared with 6 sets of new ProTaper rotary instruments individually. Additionally, the control group was established with a set of new ProTaper rotary instruments. After finishing each canal preparation, the instruments accompanied by control were examined under the stereomicroscope by an inspector without knowing the group. If distortion, unwinding, abrasion or fracture occurred within one set of instruments, then the whole set was disposed. The sets without problems were in use until 30 times. After 5, 10, 20 times canal preparation, S1, F1 files without deformation under stereomicroscope were examined under scanning electron microscope (SEM).</p><p><b>RESULTS</b>Deformation of ProTaper rotary instruments happened after 12 times in group A and after 7 times in group B. In these two experimental groups, microcracks were found increasing with the times of use under SEM in the instruments without deformation under stereomicroscope. The microcracks on tip of instruments were deep in the early use and became smoother after 10 times. Similar changes happened on knife-edge of instruments, and the microcracks extended over the edge after 20 times use.</p><p><b>CONCLUSION</b>Root canals with severe curvature tend to damage ProTaper rotary instruments more frequently than moderately curved canals. ProTaper rotary instruments are appropriate to treat less than 7 root canals with severe curvature or 12 root canals with moderate curvature. Stereomicroscope is recommended to detect early damages on Ni-Ti rotary instruments, for preventing instruments fracture in clinic.</p>

Comparison of clinical effect of different tapered gutta-percha root filling with warm vertical condensation / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To compare the clinical effect of different tapered gutta-percha root filling by warm vertical condensation with immediate postoperative radiographs and one year follow-up.</p><p><b>METHODS</b>40 maxillary anterior teeth with single, straight canals were divided into two equal groups. The teeth were instrumented with Hero 642 rotary nickel-titanium files to a master file 0.06 taper No. 30. Group 1 was obturated with 0.02 tapered gutta-percha using System B for downpack and Obtura II for backfilling. Group 2 was the same but 0.06 tapered gutta-percha. Every tooth's X-ray radiographs of immediate postoperative and one year follow-up were taken. In order to compare the quality of root canal filling, the rate of filling material extrusion, and the rate of obturation of lateral canals in each group were evaluated by X-ray radiographs. The clinical effect of one year follow-up's radiographs of the two groups was compared too.</p><p><b>RESULTS</b>There was no significant difference in two groups on the quality of the root canal filling, obturation of lateral canals, and filling material extrusion. The success of the therapy was similar. But the 0.06 tapered gutta-percha group showed more quickly healing trend on apical periodontitis.</p><p><b>CONCLUSION</b>When single, straight root canals were obturated using warm vertical condensation, adaptively tapered gutta-percha showed better clinical effect.</p>

Comparative study of shaping efficiency in C-shaped canals of mandibular second molars / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the shaping efficiency of three instrumentation techniques in the C-shaped canals.</p><p><b>METHODS</b>Sixty extracted mandibular second molars with C-shaped canals were selected and cross-sectioned at 2, 5, 8 mm from the apex by using a muffle system as described by Bramante. The teeth containing C-shaped canals were randomly divided into three groups, respectively instrumented using stainless steel K-files in step-back and step-down techniques, and ProTaper series in crown-down technique. The digital images of canal cross-sections pre- and post-instrumentation were photographed to evaluate the proportion and position of uninstrumented area Working length loss and perforation were recorded. Data were analyzed using ANOVA.</p><p><b>RESULTS</b>Step-down technique gained smaller uninstrumented area in the coronal third of the canals, while step-beck technique gained the same results in the apical third (P < 0.05). Uninstrumented proportion in apical part was significantly higher than in the middle and the coronal (P < 0.05). Instrumenting type I canal as 2 or 3 separated canals was likely to reduce the miss. There were three perforations in manual stainless steel K-file groups.</p><p><b>CONCLUSIONS</b>Early opening the coronal part of C-shaped canal, shaping C-shaped canal as two or three separated canals and instrumenting the apical part with step-back technique, seemed to be the effective methods to avoid miss.</p>

Quality of apical seal of differently tapered gutta-percha cone using warm vertical condensation technique / 华西口腔医学杂志

<p><b>OBJECTIVE</b>The purpose of this study was to compare the quality of apical seal of the canals that obturated with differently tapered gutta-percha cone using continuous wave technique.</p><p><b>METHODS</b>62 extracted human mandible incisors were prepared with Gates-Glidden drill and Hero642 to a final file of No. 30 and 0.06 taper. The teeth were randomly separated into 0.02 taper group (30 teeth), 0.06 taper group (30 teeth) and positive control group (2 teeth). The teeth of 0.02 taper group and 0.06 taper group were respectively obturated with a 0.02, or 0.06 tapered gutta-percha cone and Cortisomol sealer using warm vertical condensation technique separately. The teeth of positive control group were not obturated. In 0.02 taper group and 0.06 taper group, 10 teeth were placed in India ink for 24 hours, 10 teeth were placed in India ink for 10 days, 10 teeth were placed in India ink for 90 hours after 67 days storage in Hank's balanced salt solution. The teeth of positive control group were placed in India ink for 24 hours. The apical leakage was evaluated by the linear measurement under the stereomicroscope.</p><p><b>RESULTS</b>The dye penetration of positive control group was along the whole canals. The apical leakage of 0.02 taper group increased along with time, while no difference was found among 0.06 taper group. There was a significant difference in the degree of leakage between 0.02 taper group and 0.06 taper group in 67 days (P = 0.041), but not in 24 hours and 10 days groups (P = 0.601, P = 0.471).</p><p><b>CONCLUSION</b>Better apical seal was obtained when using the same tapered gutta-percha cone with root canal.</p>

Clinical evaluation of the effect of angulation apical X-rays and the X-rays with file in diagnosing multiple canals in mandibular anterior teeth and premolars / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate different angle projection technique for the clinical detection and treatment of multiple canals in mandibular anterior teeth and premolars.</p><p><b>METHODS</b>Two hundred and forty-seven in vivo mandibular anterior teeth and premolars were selected from two hundred and fourteen patients. Four kinds of radiographs were taken for each tooth. The radiograph was taken at a horizontal angles of 0, 20 - 30 degrees from the mesial or distal of the tooth with and without files in canal. If a radiolucent line or files was present mesial or distal to the main canal, an additional canal was suspected. If the tooth appeared to have one large canal in the cervical or middle third of the root which disappeared or constricted as it traveled in an apical direction, an additional canal was suspected. The root canals were instrumented with ProTaper in crown-down mode and filled with laterally condensed gutta-percha and paste, the root canal configurations were classified into Types I - V.</p><p><b>RESULTS</b>60.92% multiple canals and 26.44% long oval canals were detected and treated from suspected multiple canals. The sensitivity of angle projection technique with file in X-ray diagnosing of multiple canals was 93.0%, and second canal was missed in four cases. The multiple canals in the 247 mandibular anterior teeth and premolars were present in central incisors: 9.43% (5 of 53); lateral incisors: 38.33% (23 of 60); canines: 15.90% (7 of 44), first premolar: 40.38% (21 of 52); second premolar: 2.63% (1 of 38).</p><p><b>CONCLUSIONS</b>The different angle projection technique will assist the clinician in the detection and treatment of multiple canals in mandibular anterior teeth and premolar, and angle projection technique with file detected more multiple canals.</p>

Comparative study of resosolv and chloroform in retreatment of canal obturated with resinifying agent / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To evaluate the possibility for removal of resinifying agent, time required for removal and the working length loss by Resosolv or Chloroform.</p><p><b>METHODS</b>40 human teeth (80 root canals) obturated with FR phenolaldehyde agent were divided into four groups, 20 root canals per group. Group A: Resosolv with K file; group B: chloroform with K file; group C: Resosolv with Ultrasonic K file; group D: Chloroform with ultrasonic K file. Calculating the pereentage for removal of resinifying agent, time required for removal and the working length loss.</p><p><b>RESULTS</b>The effectiveness of Resosolv for removing resinifying agent was better than chloroform. 87.5% of canals could be negotiated by Resosolv; 45% of canals be negotiated by chloroform.</p><p><b>CONCLUSION</b>Resosolv is an effective solvent for canals obturated with resinifying agent.</p>

Location and negotiation of second mesiobuccal canals in maxillary molars / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate prevalence, location, negotiation and the effect of operating microscope (OM) in the treatment of the second mesiobuccal canal (MB2) in maxillary molars.</p><p><b>METHODS</b>113 maxillary molars were studied. The crowns of the teeth were removed 1 mm above the chamber bottom for searching MB2 canal. Initially location and negotiation of MB2 canal were attempted without OM. Teeth in which MB2 canal were not located or negotiated were further explored under OM. Canal orifices including MB orifice, MB2 orifice and palatal orifice were filled by red gutta-percha cones, then the teeth were scanned by scanner. The images were analyzed by Image-Proplus 4.0 software to measure the relationship between MB2 canal and other canals.</p><p><b>RESULTS</b>The MB-MB2 distance is (1.47 +/- 0.54) mm, MB-P distance is (5.77 +/- 0.66) mm, the vertical distance from MB2 to MB-P line is (0.53 +/- 0.28) mm, the angle between MB-P line and MB-MB2 line is 23.07 degrees +/- 13.08 degrees. MB2 orifices were located in 70 teeth (61.9%) and negotiated in 53 teeth (46.9%) without OM. With OM, additional MB2 orifices were located in other 6 teeth, 4 were negotiated; and 2 were negotiated in which MB2 canal were not negotiated without OM.</p><p><b>CONCLUSIONS</b>MB2 canal can be located in 67.3% and negotiated in 52.2% of maxillary molars. Ability to locate and negotiate MB2 canal is facilitated by OM. The MB2 canal was located less than 1 mm mesially to the MB-P line and 2 mm palatally from the MB orifice.</p>