BackgroundEstablishing the working length at the apical constriction is considered ideal for root canal therapy. Because of the limitations of radiography and complicacy of the apex of the root, electronic measurement of canal length has become valuable for endodontic treatment. This study was designed to evaluation of the accuracy of the Root zx electronic apex locator in the presence of NaOCl 2.5% and chlorhexidine 0.2%.Material and MethodsThirty extracted human premolars with complete root formation were enrolled. The actual length (AL) was assessed visually (under stereo microscope) and teeth mounted in the saline model. The electronic length (EL) measurements were recorded in the presence of NaOCl 2.5% and chlorhexidine 0.2% and the differences between the EL and AL were compared.ResultsBy accepting the error of 0.5 and 1 mm, the accuracy of Root zx was 76.7% and 96.7% in the presence of chlorhexidine 0.2% and 90% and 100% in the presence of NaOCl 2.5%, respectively. No statistical differences was found between the measured groups (P=0.223).ConclusionsOur results confirmed that Root zx can accurately determine the apical constriction in presence of both NaOCl 2.5% and chlorhexidine 0.2%. Key words:Chlorhexidine, Sodium Hypochlorite, Root ZX.

Background and Aim: Evaluation of root and canal morphology and anatomy of the teeth is essential for successful root treatment. This study aimed to evaluate the morphology and anatomy of the root canal of maxillary second premolars using the cone-beam computed tomography (CBCT) technique in a radiology center. Material and Methods: We used CBCT images of a specialized radiology center archived in 2014 in Qazvin and evaluated them by use of Remexis software. Evaluation of the images was carried out by a radiologist and an endodontist. The number of roots and their morphology, number of canals, the direction of root curvature, and canals in buccolingual and mesiodistal directions were assessed using the chi-square test in two genders. The significance level was considered 5%. Results: A total number of 106 CBCT involving 117-second premolar teeth were evaluated. 93.2 % of the teeth had one root and 6.8 % had two roots. There was no significant difference in the number of roots between the two sexes (Pv=0.164). According to Vertucci classification for single-rooted teeth, 59.6 % were of type I, 20.2 % of type II, 9.2 % of type III, 0.9 % of type IV, 6.4 % of type V, 1.8 % of type VI, and 1.8 % of type VII. Among two rooted second premolar teeth, 87.5 % were of type I and 12.5 % of type III. Conclusion:In maxillary second premolars, the majority of teeth had one root with type I and type II canals. During root treatment, these anatomical variations should be considered.

Background and Aim: Common causes of dental discoloration include trauma, drugs, genetic defects, decay, and age. In order to correct discoloration of pulpless teeth, internal bleaching is recommended. The aim of this study was to compare microleakage of resin modified glass ionomer and OrthoMTA used as an intraorifice barrier in non-vital bleaching. Materials and Methods: In this experimental study, 36 extracted mandibular premolars were selected and randomly divided into two experimental (n = 16) and two control groups (n = 2). 2mm of OrthoMTA and RMGI cements were placed as intraorifice barriers in the experimental groups. Subsequently, we placed a mixture of sodium perborate and 30% hydrogen peroxide as internal bleaching material into the canal and replaced it every three days. Leakage was measured using pH diffusion method by a digital PH meter. Data were statistically analyzed by using T-independent test and repeated measures and variance analysis (P<0.05). Results: The pH value of the negative control group was as same as the PH of normal saline while the PH value of positive control group was significantly higher than those of other groups. PH values of Ortho MTA and RMGI at the baseline and on the first, sixth and ninth day did not show significant differences with one another, while microleakage of OrthoMTA group was significantly lower on the third day. Conclusion: In general, OrthoMTA had less leakage than RMGI but both materials can be used as suitable barriers for internal tooth bleaching.

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BACKGROUND: Test anxiety is a major educational problem among students all around the world. The purpose of this study was to investigate the relationship between academic procrastination and test anxiety among the dental students of Qazvin University of Medical Sciences. MATERIALS AND METHODS: The present study was a descriptive–analytical study. The study sample consisted of 152 dental students; Solomon and Rothblum's procrastination scale and Friedman's test anxiety questionnaire were used to collect data. To analyze the data, descriptive and analytical statistics (analysis of variance, independent t -test, and Pearson's correlation) were used at a significance level of P < 0.05. RESULTS: The results of the present study showed that there is a significant relationship between procrastination and test anxiety and its components. The relationship between academic procrastination and gender was not significant, but a significant relationship was found between test anxiety and its dimensions with gender in terms of cognitive error and total test anxiety. No significant relationship was found between academic procrastination and test anxiety and their components with marital status, age, and grade point average. CONCLUSION: According to the findings of the present study, people with academic procrastination have more test anxiety and fear of humiliation, irrational and negative thoughts, and more stress.

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This study aimed to compare the accuracy of three types of apex locators versus digital radiography for working length (WL) determination. This experimental study was conducted on 58 extracted maxillary premolars. The teeth were decoronated, the access cavity was prepared, and WL was determined using a #15 K-file to serve as reference. The WL was then measured by Woodpex V, Woodpex III, and Root ZX apex locators in the presence of 0.9% saline, and also on a photostimulable phosphor plate (PSP) digital radiograph taken by the parallel technique. The values were compared with the actual WL using the paired t-test (alpha = 0.05). Digital radiography, Root ZX, Woodpex V, and Woodpex III determined the WL within ±0.5 mm from the actual value in 84.48%, 100%, 89.66%, and 87.93% of the cases, respectively. Woodpex V (p = 0.039), Woodpex III (p = 0.001), and Root ZX (p = 0.001) significantly over-estimated the WL. The WL measured on digital radiographs was not significantly different from the actual WL (p = 0.213). The position of the apical foramen (central/lateral) had no significant effect on the accuracy of WL determination by different techniques (p >0.05). Within the limitations of this in vitro study, all the tested modalities showed acceptable accuracy for WL determination in maxillary premolars.

Background: Mandibular first molars appear to be the most commonly tooth subjected to a root canal treatment, therefore a better understanding of the anatomy critical zones for resistance of this teeth may decrease the treatment's failure rate. So, this study was conducted to evaluate the dentin thickness of the danger zone in mesial roots of mandibular first molars using cone beam computed tomography in an Iranian population. Methods: In this cross-sectional study, 210 Cone Beam Computed Tomography acquisition of the mandibular first molars were collected from a radiology center in Qazvin. The dentin thickness of the mesial roots (mesiobuccal and mesiolingual canals) was measured from the furcation to 5 mm below. The relationship between the dentin thickness in the danger zone and parameters, like age, gender, placement side, root length, the curvature of the canal, canal type, presence of middle mesial canal, and distance between the orifices of the mesial canals was investigated. Frequency, mean and standard deviation for variables were calculated, and data analysis was done by SPSS using simple and multiple linear regression and Pearson correlation coefficient. Also, two-sample t-test was used to compare mesiobuccal and mesiolingual on two sides. The significant level was also considered at (p < 0.05). Results: The average minimum thickness of danger zone dentin was found to be 0.885 ± 0.259 mm in the mesiobuccal canal and 0.906 ± 0.206 mm in the mesiolingualcanal. Also, the minimum thickness of dentin in the mesiobuccal and mesiolingual canals in the range of 0 to 1 mm from the furcation was more than in other areas. There was no significant relationship between the minimum dentin thickness of the danger zone with gender, placement side, root length, canal type, and mesial canal entrance distance. But with increasing age, the thickness of dentin in the danger zone in the mesiolingualcanal increased significantly (p = 0.008). It was also observed that with the increase in the curvature of the canal, the thickness of the dentin in the danger zone in the mesiobuccal canal decreased (moderately curved (p = 0.008), severely curved (p = 0.046)). In addition, the thickness of the dentin in the mesiobuccal and mesiolingual canal was less in the samples with the middle mesial canal (p = 0.047, 0.044). Conclusions: Less dentin thickness in the danger zone in the mesial roots of mesiolingual mandibular first molars was seen in younger patients in mesiolingual canal, with a greater degree of canal curvature in the mesiobuccal canal and teeth with a middle mesial canal. Therefore, it is suggested that large taper instruments should be used with more precision to prevent complications.