[Number of severely curved root canals preparation leading to either defect or fracture using three rotary systems]

Statement of Problem: There are many controversies regarding the usable number of rotary files in the literature

Purpose: The aim of this study was to compare three Rotary Systems in Terms of Number of Severely Curved Root Canals Preparation, Till Either Defect or Fracture

Material and methods: In this in vitro study, 60 mandibular or maxillary molar mesial roots with a mature apex and a curvature of 35-80[degree sign] were evenly divided into three groups according to their radius and curvature angle. The Pruett method was used to define the curvature degree. In all the three groups, cleaning and shaping were accomplished with a working length of 16mm.Then, the number of the prepared canals until any defect or fracture [using a 8x magnifier] was recorded and canal preparation was done with the same devices in the remaining canals. Chi-square test was applied for inters categorical variables comparisons. Kaplan-Meier curves were used to display the number of prepared canals till any defect or fracture with further comparison by a log-rank test. To compare the curve angle and radius, Kruskal-Wallis test was used. p.value of less than 0.05 was considered as statistically significant

Results: The average number [+/-SD] of the prepared canals leading to defect or fracture in flexmaster, Hero and Race systems was 11.87 [+/-2.07], 13.28 [+/-2.46], and 9.66 [+/-1.92], respectively [p <0.05]. Overall, 20 devices were found to be fractured or defective, among which 7 had defects and 13 had fractures. The rates of defects in Hero, Race and Flexmaster were 50%, 33.3% and 28.6% with the fracture rate of 50%, 60% and 71.4%, respectively [p > 0.05]

Conclusion: Hero system showed higher numbers of prepared canals and revealed less fracture rate. Meanwhile, Race system revealed the least number of prepared canals with the highest rate of the fracture. However, there were no statistically significant differences between the systems

[Evaluation and comparison of apical leakage following root canal dressing with different calcium hydroxide preparations]

The use of calcium hydroxide as an intra-canal medication can lead to leakage of permanent obturation of the canal and failure of the treatment. The purpose of this study was to evaluate the rate of the remained calcium hydroxide in radiographic views and their effect on apical leakage. For this study, 75 human extracted premolar teeth were divided into 5 groups randomly. All the teeth were prepared by step back technique and apical foramen enlarged to number 30 file. Aria dent calcium hydroxide was introduced into the canal in group 1. In group 2, Barium sulfate was added to calcium hydroxide powered in 1 to 9 proportion and the methods was gone on the same as in group 1. Dentsply calcium hydroxide was mixed with glycerin-based aqueous and introduced into the canal in group 3. Calcium Hydroxide paste [Pulpdent] was introduced into the canal with its special needle. In group 4 and 5, there was no calcium hydroxide as a control group. The canals were prepared with one sixe larger than master apical file, MAF [35 file size] to remove calcium hydroxide. The remaining of calcium hydroxide was accessed radiographically and compared using Kruskal Wallis test. Dye leakage in the 5 groups was compared, using ANOVA and Tukey tests. There was no significant difference between the five groups when dye leakage was compared, but calcium hydroxide paste [Pulpdent] shows more remained material when evaluated radiographically. The use of calcium hydroxide paste with methyl cellulose base for intra-canal medicament is not recommended

[Comparison of canal transportation after preparation by 3 different rotary systems]

Cleaning and shaping has been recognized as one of the most important steps of root canal treatment. Various Ni-Ti rotary systems have been introduced for reduction of complications and facilitating the root canal shaping process. The purpose of this study was to determine the amount of transportation by using the three rotary systems, Profile, Flex master and Race. This ex-vivo randomized controlled trial was carried out on mesial mandibular root canals [type 3 Weine] with mild curvature [15-35°]. The roots were randomly divided into three groups of 20 canals each. The roots were sectioned horizontally at 3mm, 6mm from the apex and then, reassembled before instrumentation according to the manufacture's guidelines. Photographs were taken from the cross sections before and after instrumentation. Image analyses were performed by Photoshop software, version 8. The ability to preserve canal shape centrally as well as the direction of transportation was determined next. Data was analyzed by ANOVA and Tukey tests. The difference was significant in mid apical parts when comparing the three groups. Most transportation was in the furcation area. Race had the most and profiles showed the least transportation in both parts of the roots [P=0.001]. The profile system was found to be the best for preserving the centering position of the root canal among the three rotary systems

[ in vitro evaluation of antimicrobial activity of NaCIO and chlorhexidine as intracanal irrigants on streptococcus faecalis]

Today most of endodontic treatments are successful and just a low percentage of them may lead to failure. This failure may be due to remaining necrotic and infected agents in root canal system which is because of the complex anatomy of root canal and the rooms not available during mechanical and chemical cleaning. So use of chemical solutions for bacterial disinfection and necrotic agent removal is recommended. The aim of this study was to compare NaCIO Chlorhexidine and normal saline solutions in eradication of S. faecalis as a resistant bacteria in routine endodontic treatments. In this experimental and In vitro study 50 single canal human extracted teeth were selected we made conventional access cavities on all of them. Then, the teeth were divided into five equal groups randomly. Next, they were sterilized in autoclave. After that, we injected S. faecalis in root canals and put them in 37°C incubator for 36 hours. After bacterial growth a culture was prepared from each tooth to determine bacterial growth rate. Finally endodontic treatment was done on the teeth. Duration, method of filling and type of files were the same in groups but the type of chemical solution was different, [group 1: Saline, group 2: Chlorhexidine, group 3: NaCIO 2.5%, group 4: NaCIO 1%, group 5: NaCIO 5.25%]. Another culture was prepared after treatment. At last the number of colony forming units before and after treatment was compared with each other. The data were analyzed by one-way ANOVA. The results showed that there was a significant difference among NaCIO [2.5%, 5.25] and other solutions in decreasing the number of bacteria in root canals after instrumentation. Normal saline, NaCIO 1% and Chlorhexidine solutions developed similar antimicrobial activities. Considering the results of this study, when we have limitations using NaCIO, we Can use Normal Saline as a safe material. In necrotic teeth, use of NaCIO 2.5% for better removal of organisms is recommended

[ comparison of accuracy of determining the root canal working length by different magnifications of digital radiography]

Successful root canal therapy is related to cleaning, shaping and obturation of the root canal system with a proper limited working length. Therefore, these are achieved by knowledge of root canal anatomy and radiograph images. Current radiographic techniques are elementory methods. With the advancement of computer technology, and due to limitations that exist, in this recent decade significant attention has been given to digital radiography. Software programs for digital radiographic systems, such as magnification of different images is a tool assistant for digital systems in increasing precision. The purpose of this study was to compare different magnifications of digital radiography to determining canal length. In this experimental in vitro study, 30 human anterior teeth were selected and cleaned in detergent. The actual working length was measured with a N.15 file. Then the teeth were casted and the files were inserted in canals in 3 different positions, proper, under and over. Ninety images of the teeth in three magnifications were made and working length was evaluated by three endodontists randomly. Then the Friedman test was used for statistical analysis. After statistical analysis, the results showed that there was no significant differences between the groups. But there is significant difference in 2X magnificantion of under working length to real working length. In conclusion, it can be stated that magnification of digital radiography can not be helpful in determination of working length especially in under position

[Comparison of air driven handpiece and electromotor on distortion or fracture rate of nickel titanium rotary instruments]

One of the affecting factors in adverse prognosis of root canal therapy is procedural accidents as broken files, facing with difficulty in removing. Many manufacturers have designed and marketed various electromotors with the ability of controlling rotational speed and torque. On the other hand, these expensive motors have encouraged other manufacturers to marketing different air driven handpieces. Despite of presenting various vast instruments for this purpose, only limited comparative studies have been carried out between electromotor and air driven handpiece. The purpose of this study was to evaluate the effect of air driven handpiece versus electromotor on distortion or fracture rate of NiTi rotary files. This in vitro randomized controlled trial was carried out on 160 canals of human's matured molars with mild curvature [15-33°]. After initial preparation of samples and considering the inclusion criteria, in the first group, preparation was carried out with air driven handpiece and in groups 2 Endo IT [VDW, Germany] was used as electromotor. In both groups M two files with crown down technique were used for canal preparations. Data on file distortion or fracture were collected and analyzed using Mann Whitney, Mantel Cox, Kaplanmeiere and T tests. No significant differences on distortion or fracture rate of files between the two groups were found [p>0.05]. Based on survival analysis safety probability of files after preparation of 9 canals was%64.1 in group 1 and%69.9 in group 2. There was no significant differences between this safety probability in the two groups [P=0.272]. These findings showed that both electromotor and air driven handpiece has nearly similar effect on fracture rate or distortion of NiTi rotatory instruments

[Evaluation of different clearing techniques: an auxiliary method for studying root canal anatomy]

Various techniques for clearing the root canal system have been used in different aspects of dentistry. Poor quality of the final cleared tooth may affect accurate evaluation of the anatomy or other characteristics of the canals. The purpose of this study was to compare a number of currently used clearing methods in order to identify the most effective procedure. Fifty human extracted premolars were included in this experimental study. A routine clearing protocol was employed for all teeth. The specimens were divided into 5 groups of 10, applying different combinations of decalcifying [HCL, HNO3] and clearing agents [eugenol, methyl salicylate]. The samples were examined by two endodontists. Data were subjected to statistical analysis using Chi-square and Kruskal Wallis tests. A significant difference was observed between the study groups. The most effective decalcifying material and clearing agent was%10 HC1 and methyl salicylate, respectively. According to the results of the present investigation, application of%10 HC1 along with methyl salicylate is suggested for the evaluation of the root canal system

[Apical leakage in obturated canals using two different sealers after immediate and delayed post space preparation]

Successful endodontic therapy depends on a well-adapted filling in conjunction with root canal. The proper restoration requires the placement of a post and core. Therefore, the time of post space preparation, and its possible effect on the quality of the apical seal is important. The purpose of this study was to compare the effect of immediate and delayed post space preparations on apical seal using two currently used sealers; AH26 and Apexit sealers. Seventy six extracted anterior teeth were used in this experimental study. Teeth were randomly divided into four groups and all canals were prepared by step back method, and then filled with gutta percha by lateral condensation technique. AH26 was the sealer used in groups 1 and 2, while in groups 3 and 4 Apexit sealer was used. In groups 1 and 3, post spaces were immediately prepared. But in groups 2 and 4 they were prepared after one week. After preparation, the teeth were immersed in India ink for 3 days and finally, were cleaned. The extent of dye penetration was determined by stereomicroscope. The data were obtained and analyzed statistically with ANOVA, Tukey and T.tests. The results showed that the lowest and highest rates of dye penetration were detected in groups 1 and 4 respectively. There was significant difference in apical leakage between the AH26 immediate, and Apexit delayed post space preparation. According to the results of this study, the immediate preparation of post space after obturation and before setting of the sealer is recommended

[ comparison between conventional and digital radiography in estimating the working length of root canal]

The importance of determining working length in root canal therapy is clear for each clinician, and conventional radiography has been the technique of choice so far. But developing computerized technology in radiology and it's show up devices in the market, having several advantages, makes the tendency to use such technology more and more. Despite the many studies in this field, the accuracy of these devices is still unclear. The purpose of this study was to compare the accuracy of conventional radiography and digital radiography in order to estimate the working length of root canal. For this in experimental vitro study 17 root canals of maxillary and mandibular molar teeth on human skulls were selected. Size #15 files were placed in canals in order to assess working length. Then two radiography were taken from each canal: one using conventional and the other one using digital technique, through parallel method of radiation accomplished by special positioning devices. Next the teeth were extracted and real working length was determined. After that two independent observers estimated working length in both conventional and digital radiographs. Finally the mean working lengths of each group were compared with the real amounts using paired t-test analysis. In all tests a significance level of 0.05 was determined. Statistical analysis revealed that digital radiography was more accurate than conventional radiography in determining the working length [P=0.019]. Due to the greater accuracy and other advantages of digital radiography, this method is strongly recommended, regarding the similarities between the study and clinical situation for working length determination

[Stereomicroscopic evaluation of calcified canals for determining open spaces]

One reason for endodontic failure is calcified canals. Canals may be calcified radiographically or clinically but are not often completely obliterated. The purpose of this study was to determine the microscopic size of open spaces in clinically and radiographically calcified canals. In this in-vitro descriptive study 18 human extracted teeth including 21 calcified canals were selected and transverse sections were prepared in 0.8-0.9mm thickness and studied using a stereomicroscope. After taking digital photographs of these sections, open spaces dimensions were measured in each section using Auto Cad 14 program. Computerized evaluation of samples revealed varying dimensions of open spaces. Open spaces were observed in most of the canals, specially those with closed orifices. According to varying dimensions of open spaces in calcified canals, practitioners are recommended to be more persistent when negotiating canals with calcified appearances

[ comparative study of sealing ability of Roth Sealer with ZOE, Tubli-Seal and AH26]

Introduction: apical seal is an important factor in successful root canal therapy. Still there are controversies about sealing ability of various sealers materials. Recently Roth-Sealer which is very popular in Europe and U.S.A has been produced by an Iranian company. The purpose of this study was to compare sealing ability of Iranian Roth Sealer with ZOE, Tubli-Seal and AH26

Materials and Methods: in this study, we used 100 fresh extracted single root teeth of human. After cutting the crown from CEJ and determination of working length, canal preparation was done with passive step back technique using patency file. The teeth randomly were divided into 6 groups. Four groups with 20 teeth for experimental groups and two groups with 10 teeth as positive and negative control groups. Obturation was done with lateral condensation in four groups with Roth Sealer, ZOE, tubli-Seal and AH26. The coronal seal was achieved with amalgam. In positive control group, we did not use sealer after preparation all teeth were incubated at 37 OC temperature and 100% humidity for 72 hours. All teeth were covered with two coats of nail polish and sticky wax except 2mm of apical part. In the group of negative control, all of the tooth surface were covered. Dye penetration was measured using Indian ink [PH=6.2]. After splitting the teeth longitudinally, dye penetration was measured by stereomicroscope. Data were analyzed with ANOVA and DUNCAN tests

Results: showed that dye penetration in positive control group was complete and significantly more than other groups while in negative control group, no dye penetration was observed and in Roth Sealer group, it was significantly less than other groups[P<0.05]. There was no significant difference between ZOE, Tubli Seal and AH26

Conclusion: Iranian Roth sealer proved to be appropriate for root canal therapy compared to other 3 sealers. So, this can be considered as a substitute for foreign Roth sealer which is very expensive. Performing histologic studies on it for confirmation is recommended