Steel Files Research Articles

Comparison between Corrosion of Stainless Steel Hand k-file and Nickel-Titanium Rotary Instrument following Immersion in 5.25% NaOCL Irrigation Solution: An In Vitro Study

The study was aimed to compare the corrosion of stainless-steel hand K-file and Nickel-titanium rotary instrument following immersion in 5.25% NaOCL irrigation solution, in vitro. A total of 20 new Nickel-titanium (NiTi) rotary files and 20 stainless steel (K file) was selected and immersed in 5.25% NaOCL irrigation solution. All files were subjected to the corrosion test: Record the open circuit potential (OCP) for 1 h on a strip chart with high impedance. The strip chart recording for each file was classified into a stability score: (i) stable, (ii) unstable, or (iii) erratic. The percentage of OCP was measured by a potentiostat and a standard calomel electrode reference. The frequencies of visually observed corrosion were further investigated by scanning electron microscope (SEM). The results of the present study confirmed that stainless steel file showed greater corrosion rate than that of NiTi files. Additionally, both files had pitting and crevice corrosion, as seen by scanning electron microscopy (SEM) analysis. However, NiTi files demonstrated a lower rate of corrosion than stainless steel files. In conclusion, NiTi files showed greater corrosion resistance than that of stainless-steel files.

Mechanical analysis of concrete with partial replacements of aggregates by steel filings

RESUMO O presente trabalho teve por objetivo apresentar os resultados obtidos para o comportamento mecânico do concreto considerando a substituição parcial dos teores dos agregados por resíduo industrial provenientes da usinagem de aço. Conhecidas as propriedades mecânicas dos metais, considera-se que a substituição parcial dos agregados em concretos por resíduos dessa natureza possa atuar não apenas como um fator de melhora no comportamento do material, mas também como uma maneira de se produzir uma destinação eficiente ao resíduo em questão, além de que, a substituição de agregados por materiais alternativos contribui para mitigar a escassez desses recursos. Dessa forma, o trabalho justifica-se pelas suas potencialidades em relação à engenharia de materiais cimentícios e impactos ligados à sustentabilidade das edificações. Para se investigar o material foram adotados três teores de substituições em relação ao peso de cimento, 5%, 10% e 15%, sendo efetuados ensaios para obtenção da absorção de água e consistência, além das resistências à tração indireta, compressão e módulo de elasticidade estático. A que a substituição dos agregados por resíduo de usinagem leva a maior qualidade do concreto produzido além de acréscimo de resistências, essa melhora se mostrou mais expressiva para a substituição do agregado miúdo, com aumento na resistência média à compressão e tração de até 73,70% e 73,71% respectivamente, obtendo-se através de aproximações não lineares o teor ótimo próximo a 12%, para as substituições de agregado graúdo teores acima dos estudados tendem a ser mais interessantes.

Endodontic file separation and its management among dentists in Punjab, Pakistan

The study aimed to find the incidence and awareness of endodontic instrument separation and its management among dental house officers, postgraduate trainees, demonstrators, consultants, and general dentists. Methods: This online questionnaire-based cross-sectional study was conducted with the approval of the IRB in private and public dental hospitals and dental clinics in Punjab. The authors developed the survey tool, which comprises 24 closed-ended items regarding demographics, the incidence of file separation, and awareness about its management. The data were analyzed using IBM SPSS version 24. The Chi-Square Test was used to compare percentages of categorical variables. Results: Postgraduate trainees experienced the most instrument separations (43.6%), made the most retrieval attempts (49.2%), and experienced the most secondary errors during retrieval (52.1%) (p<0.001). Around four out of ten respondents always informed the patients (39.6%) and department (41.6%) about errors. Manual files (69.8%), stainless steel files (75.8%), and short files (60.4%) were more frequently separated, and the most frequent cause was older fatigue files (57.7%). Manual files were more frequently broken in public dental institutes (p=0.003). Two-thirds of the file separations (72.5%) occurred during cleaning and shaping in the apical third of molars (65.1%), especially in mesiolingual canal (56.4%). Bypass attempt was the most common in symptomatic teeth (47.7%). Conclusions: Preventive approaches such as limiting file reuse and constructing a glide path can reduce the occurrence of file separation. Operators should be familiar with the number of uses of the instrument before fatigue and should be trained through workshops and refresher courses.

Use Of Mining Tailings in The Manufacture of Ecological Bricks to Encourage the Construction of Sustainable Housing

This work aimed to manufacture ecological bricks using mining tailings, by-products of mining activity, to contribute to sustainable housing development. The Peruvian technical standards E.060 and E.070 are used as a reference framework to achieve this. The study focuses on various aspects, such as mineralogical analysis, particle size distribution, plasticization, workability, and rheology. The research methodology adopted is deductive, with an applied and quantitative approach. A retrolective data collection instrument and descriptive, explanatory, correlational, and descriptive level approaches are used. The results obtained from this research reveal significant findings. It was observed that including 20% of an alkaline binder based on calcined clay improves the development of bricks in areas with severe climatic conditions. In addition, incorporating lime fibers reduces thermal conductivity and increases bricks' compressive and bending strength. Blocks containing 30% clay cork reinforce the bricks' bulk density, thermal conductivity, and strength. On the other hand, it was verified that tailings with lead-zinc sulfide, reduced by 47%, comply with the carbonization and contraction coefficient. Shale, fly ash, and cement tailings achieved a compressive strength of 26 MPa and a water absorption rate of 14.32%. The addition of steel filings by 3% improves compressive strength. Likewise, incorporating plastic waste increases the compressive strength to reach 37.5 MPa. As for geopolymers, it was observed that viscosity recovery is in a range between 65% and 82%. Finally, recycled aggregates, with a maximum nominal size of 3/8" and 1/4", meet the standard requirements, providing a compressive strength of up to 8 MPa. Finally, this study demonstrates the potential of using mining tailings and other recycled materials to manufacture ecological bricks for sustainable housing development in mining communities, offering viable solutions from an environmental and construction point of view.

NiTi rotary system in endodontics – An overview

Success of root canal treatment depends on complete removal of microorganisms which is done through chemomechanical instrumentation of root canal system. To achieve this, earlier stainless steel files were used which had inherent disadvantages of excessive tooth cutting as well as straightening of the canal curvature. This Eventually led to introduction of NiTi alloy which has proven to be a valuable adjunct in root canal preparation. These NiTi files are highly flexible and elastic due to their Metallurgical properties like Austenite, Martensite, Intermediate R phase. It has got greater strength and modulus of elasticity making them more beneficial in curved canals. Over the evolution various changes have taken place within the NiTi rotary systems and various generations too. Thus the Objective of this Review article is to completely discuss about Evolution, Metallurgy, Mechanical properties, Generations of NiTi rotary system.

Stabilization of clayey soils using asphalt emulsion and steel filings for subgrades

This research evaluates the changes brought about by the addition of asphalt emulsion and steel filings in clayey soils for subgrade in urban pavements. For this study, different dosages of each additive were established, being 1%, 2%, 4%, 8%, and 15% for the steel filings and 3%, 6%, 9%, 13%, and 18% for the asphalt emulsion, obtaining favorable results in the subgrade in accordance with the CE.010 Urban Pavement standard. With the steel filings the CBR (California Bearing Ratio) had a linear increase whose maximum value was reached with the dosage of 15% increasing the CBR considerably by 189.47% above the CBR of the natural soil; on the other hand, with the asphalt emulsion a maximum increase in CBR was obtained with the dosage of 13% obtaining an increase of 236.84% and after that a decrease is observed with the addition of 18% of asphalt emulsion.

Strength and nuclear shielding performance of heavyweight concrete experimental and theoretical analysis using WinXCom program

This study presents experimental work and theoretical analysis to evaluate the performance of heavyweight concrete for nuclear shielding applications. Heavyweight concrete mixes were prepared using different coarse aggregates including crushed dolomite, magnetite and steel. Also, magnetite and steel filings were used to replace 50% and 100% by volume of the sand. The workability of fresh concrete and the compressive strength at 7 and 28 days were evaluated. The attenuation coefficient for concrete samples was determined using gamma-ray spectrometry and WinXCom software in gamma-energy lines of 0.662–1.332 MeV. The experimental results indicated that the concrete mixes containing steel particles as a coarse and fine aggregates achieved the most desirable performance in terms of density and gamma-attenuation. Concrete densities up to 5.8 ton/m3 were obtained using steel as coarse aggregates. For the examined photon energy lines, the average attenuation coefficient of the concrete mixes incorporating steel was two times that of the control mix. On the other hand, the concrete mixes incorporating magnetite achieved the highest compressive strength value of 68 MPa. The attenuation coefficient could be estimated theoretically using WinXCom with errors in the range of 12% to −15%.

Técnicas endodônticas com instrumentos de Níquel Titânio: análise da qualidade e eficiência da instrumentação em molares decíduos

ABSTRACT Objective: The purpose of the present in vitro study was to evaluate the efficiency of three different instruments in the root canals of artificial primary molars as well as the quality of the fillings. Methods: Sixty artificial primary molars were divided into three groups of 20 teeth. Each group was submitted to a different technique: Group 1 - conventional manual technique using Kerr files; Group 2 - manual technique with nickel-titanium files; Group 3 - NiTi rotary technique. The root canals were filled with calcium hydroxide paste. Aspects such as homogeneity of the fillings, taper and flowability of the preparations were considered comparatively to assess the quality of the instrumentations. The non-parametric Kruskal-Wallis and Mann-Whitney tests were used to compare the efficiency of the preparation of the root canal considering the preparation times of them. Results: All three techniques were equally effective at shaping the root canals of primary teeth. The working time was shorter with the rotary instrument (p=0.000). In the pairwise comparisons, working time was shorter with the rotary instrument compared to the manual techniques with steel files (p=0.000) and NiTi files (p=0.000). Comparing the manual techniques, the working time was shorter with NiTi files compared to steel files (p=0.011). Moreover, less variability in the preparation time was found when the rotary instrument was used. Conclusions: The mechanized rotary method led to a shorter operating time in comparison to the manual techniques and is therefore a preferable option for the preparation of the root canals of primary teeth.

Comparison of postoperative pain using two instrumentation techniques followed by laser irradiation in nonvital teeth with symptomatic apical periodontitis: A double-blind randomized controlled trial

Aim: Postoperative pain can be caused due to apical extrusion of debris following chemomechanical preparation. This study aimed to compare mechanized reciprocating stainless steel files and continuous rotary instrumentation with laser irradiation for postoperative pain in nonvital teeth with symptomatic apical periodontitis. Methods: Ninety (n = 30) subjects were enrolled after obtaining written consent. In Group 1, continuous rotary instrumentation using Endostar E3 Azure files without laser irradiation, in Group 2, continuous rotary instrumentation using Endostar E3 Azure files with laser irradiation, and in Group 3, mechanized reciprocating instrumentation using K-Flex hand files in K-400 Reciprocating handpiece along with laser irradiation was carried out. Postoperative pain was recorded using Visual Analog Scale at baseline, 24, 48, and 72 h. Subjects requiring rescue medications were recorded. Kruskal–Wallis and Post hoc Tukey’s test for intergroup group and pairwise comparison, respectively, and the Chi-square test for comparison of rescue medication were used. Results: The reduction in pain scores was found to be statistically significant (P < 0.05, confidence interval 95%) in all three groups at all-time points. The order of maximum pain reduction was found to be most in Group 2, followed by Group 3 and Group 1. Nine, three, and six subjects required rescue medication in Groups 1, 2, and 3, respectively. Conclusion: Mechanized reciprocating handpiece instrumentation using K-flex files as well as continuous rotary instrumentation using NiTi rotary files along with laser therapy resulted in significantly lesser postoperative pain levels than with continuous rotation alone.

Effect of low-power diode laser on infected root canals.

This study evaluated the effect of photodynamic therapy (PDT) on infected root canals. Twenty-one human teeth were selected, and 18 were infected by E. faecalis for 60 days. The antimicrobial strategies tested were: G1. Root canal preparation (RCP) using Niquel-Titanium (NiTi) rotary instruments, 2.5% NaOCl, and final irrigation with 17% EDTA, followed by PDT with methylene blue photosensitizer and laser diode low power; G2. RCP using stainless steel files and the same irrigation and PDT protocols as G1; G3. Same RCP protocol as G1 without PDT; G4. Only irrigation with 2.5% NaOCl; G5. Same PDT protocol as G1 without RCP; G6. Negative control; G7. Positive control. Samples for microbiological tests were collected initially (S1), after RCP (S2), and after PDT (S3). Subsequently, the roots were sectioned and prepared for Scanning Electron Microscopy (SEM) analysis. Bacterial growth was analyzed according to the turbidity of the culture medium, followed by spectrophotometric optical density (nm). The effect of PDT on the dentinal structure was evaluated at magnifications 1,600X and 5,000X and described qualitatively. The Wilcoxon test was used for the comparisons from the same specimens, and the Mann-Whitney test was used to compare groups ((=5%). Bacteria were found in all experimental groups' microbiological samples (S1, S2 and S3). The optical density of culture media was lower in S2 than in S1 of G1, 2, 3, and 4 (p> 0.05). After PDT (S3) in G1 and 2, there was an additional reduction in optical density of the culture medium, respectively (p>0.05). In Group 5, the analysis of culture media at S2 revealed an increase in optical density compared to S1(p>0.05). In SEM images of G1, 2, and 5, dentin with melting and recrystallization areas were evidenced. After preparation of the root canal with the rotary system or manually associated with 2.5% NaOCl, PDT was not able to completely eliminate E. faecalis present in the root canal.

Fracture Resistance of Heat-Treated Nickel-Titanium Rotary Files After Usage and Autoclave Sterilization: An In Vitro Study

IntroductionThis study aimed to evaluate the dynamic cyclic fatigue resistance of heat-treated nickel-titanium (NiTi) files after usage and autoclaving. MethodsTwo heat-treated NiTi file systems with tip sizes of #25 (ie, ProTaper Gold F2 [Dentsply Sirona, Charlotte, NC] and TruNatomy Prime [Dentsply Sirona]) were selected. Files of each system were divided into 3 experimental subgroups (n = 10). For subgroup 1, new files were tested to establish the baseline number of cycles to failure (NCF). For subgroup 2, files underwent canal instrumentation in a simulated J-shaped canal block with 35° of curvature and a 16.5-mm length. The simulated canals were pre-enlarged using stainless steel files #10K and #15K. After instrumentation, the files were tested. For subgroup 3, files underwent canal instrumentation as in subgroup 2 followed by autoclave sterilization and then were tested for cyclic failure. The cyclic fatigue test was performed in dynamic pecking motion under body temperature. The time to fracture was recorded and calculated into NCF. Fracture fragment lengths were measured using a digital microcaliper. Statistical analysis was conducted using the independent t test and multifactorial analysis of variance with 95% significance. Scanning electron microscopy was used to examine the topographic characteristics after cyclic fatigue tests. ResultsThere were no significant differences between file systems in subgroup 1 using new files (P < .05). Although PG reduced the NCF after use, TN showed a significantly increased NCF (P < .05). However, after sterilization, TN showed a reduced NCF compared with the used one (P < .05). ConclusionsCyclic loading by usage and heat treatment during sterilization may result in different cyclic fatigue resistance according to the geometry and alloy characteristics.

Influence of Steel Fibers Content on Selected Mechanical Properties - Experimental Tests

The continuous development of construction due to the great needs of society and industry, the need to build newer and more durable buildings have meant that scientists all the time look for new opportunities to improve the quality of materials used in this field. Above all, concrete, as material commonly used in construction, has been the subject of research for many years in order to improve the properties. Already in antiquity there were the first attempts to modify the building material with fibers. Initially, they were organic fibers. However, the first patent dates from 1874, when A. Bernard patented the idea of strengthening concrete with steel filings [1]. Then, attempts were made to strengthen the concrete with long steel fibers, which was done by H. Alfsen in 1918. Further researches led N. Zitkiewic to test the strength and impact toughness of concrete with the use of pieces of mild steel wire [2]. Steel fibers in concrete were used for the first time by Romuladi and Baston in 1963. In the paper a comparative analysis of selected mechanical properties for concrete and fiber-reinforced concrete, e.g. compressive strength and Young's modulus, was presented. It was checked how the value of Young's modulus and the compressive strength of concrete change depending on the content of steel fibers. Three types of samples were tested: 1 - concrete, 2 &#8211; fiber-reinforced concrete containing 0.25% of steel fibers, 3 &#8211; fiber-reinforced concrete containing 0.50% of steel fibers. As the analysis has shown, the greater number of steel fibers is not directly proportional to the increase in its compressive strength or the value of Young's modulus.

Effect of Different Preparation Techniques on Root Canal Geometry: An In Vitro Study.

Aim and objectiveTo compare and evaluate canal preparation using hand stainless steel files, hand ProTaper files, and rotary ProTaper files for change in root canal geometry in terms of surface area and volume changes assessed by computed tomography.Materials and methodsThe present study was conducted in Nair Hospital and Dental College, Department of Pediatric and Preventive Dentistry in collaboration with insight CBCT, imaging technologies. A total of 36 extracted human primary mandibular second molars were collected from the Department of Pediatric and Preventive Dentistry. All the teeth were scanned using cone-beam CT (i-CAT CT Scanner Next Generation, Imaging Sciences International) preoperatively and postoperatively to assess the mean absolute change in surface area and mean change in the volume of all the canals at different levels with the use of hand stainless steel files, hand ProTaper and rotary ProTaper files.ResultsProTaper instruments, both hand ProTaper and rotary ProTaper caused significant changes in the surface area in the coronal thirds and middle thirds of the canal when compared to hand stainless steel files. No difference was found in surface area and volume changes between hand ProTaper and rotary ProTaper instrumentation.ConclusionUse of ProTaper instruments for preparation of deciduous teeth can render benefit of an improved canal preparation to facilitate better obturation and successful root canal therapy.How to cite this articleBheda P, Kakade A, Takate V, et al. Effect of Different Preparation Techniques on Root Canal Geometry: An In Vitro Study. Int J Clin Pediatr Dent 2022;15(S-1):S71–S79.

Improved fired clay brick compressive strength by recycling wastes of blacksmiths\u2019 workshops

This study investigates the effect of using steel filings from the waste of blacksmiths workshops on the clay bricks mixture to improve the bricks’ compressive strength. On the other hand, this process can reduce workshops’ waste by recycling it to preserve the resources and achieve sustainability. Adding steel filings to the mixture of red clay bricks was in different proportions by weight (1%, 2%, 3%, and 4%) on prototype bricks produced in a lab. Moreover, it aims to increase the effectiveness of clay bricks used in load-bearing walls, which can be used extensively in economical housing to reduce the cost if its strength increases by utilizing it in the load-bearing walls system instead of skeleton. The experimental approach was adopted to reach conclusions, as it is the appropriate approach suitable for this research. Before and after adding steel filings, many properties were tested, such as dimensions, weight, density, water absorption, and compressive strength. It is observed that on increasing the steel filings ratios by the mixture’s weight, the prototypes’ compressive strength also increases. The highest percentage of increased compressive strength occurred for the specimen with 3% steel filings by the mixture’s weight is (84%).

Durability of concrete made with steel filings as a replacement of fine aggregate

Steel filings are primarily composed of steel. These steel filings are produced by grinding, shaving and cutting the various steel in the mechanical workshop or factories. The steel wastes are disposed into the landfills, rivers and oceans thereby increasing pollution. To reduce these wastes reaching the landfill sites, one solution is to reuse them in construction. There have been some studies on the strength of concrete made with steel filings, however, no study has been reported on the durability. The purpose of this research was to evaluate the durability of concrete made with steel fillings as a replacement of fine aggregate. In the current study, different replacement levels of steel fillings such as 0%, 10%, 20%, 30% and 40% have been used in the making of concrete. Cube samples were tested for durability after normal curing for 28 days. It was found that the cube looses its workability and slump, when the percentage of steel filing were increased beyond 40% as replacement of fine aggregate. The water absorption increased with increasing percentage of steel filing and the sorptivity tests showed that the weight of capillary rise of water increased with the increasing percentage of steel filing due to the increased porosity of the concrete. This type of concrete may be used for the pavement and parking lots, where there is a problem of water logging, as it would allow the water to pass through it and may help in recharge of the ground water.

Endodontic practice amongst Nigerian dentists undergoing postgraduate training

Introductionthis study aimed at finding out current practice of endodontics amongst Nigerian dentists undergoing postgraduate training (also referred to as dental resident doctors) in different institutions across the nation.Methodsa questionnaire-based, cross sectional study was conducted amongst dentists undergoing postgraduate training. Questions were asked on demographics, protocol for root canal treatment (RCT), materials employed in different stages. Opinions were also sought on satisfaction with their practice and training needs in endodontics. Data were analyzed with SPSS version 20.0 and presented as tables and charts. Significance level was set at p≤0.05.Resultsninety dentists undergoing postgraduate training (57 males and 33 females) with mean age of 34.81 ± 5.9 years participated in the study. Root canal treatment was mostly done in multiple visits in both single and multi-rooted teeth (p=0.01), only about 15% performed the procedure on multi rooted teeth. Sixty-five (72.2%) never used Rubber dam, stainless steel files were being used by 69%, step down technique of preparation by 53.9% and Sodium hypochlorite was the major irrigant (80%) used. Obturation was majorly with Cold lateral compaction technique (94%), 57.2% delayed definitive restoration for maximum of 1 week and amalgam was still the major material used for posterior teeth as reported by 62.9% of the participants. The majority (55.6%) were not satisfied with their current knowledge and practice and most were those that did not have good undergraduate training (p = 0.05).Conclusionthe practice of endodontics needs standardization across the nation as it is being advocated in other countries. There is need for hands on-training on endodontics to encourage adoption of new advances in technology, as well as improve the training of postgraduate dentists in endodontics. Also, emphasis should be placed on use of rubber dam in order to minimize the spread of infection and protect the patients from aspiration of small instruments involved in endodontic procedure.

Numerical simulation of thermal insulation and longevity performance in new lightweight ladle

SummaryFor meeting the comprehensive requirements of “super insulation,” “lightweight,” and “longevity” of the contemporary ladle, this article designs a new kind of lightweight ladle with heat preservation and longevity performance, and based on steady‐state analysis method and numerical simulation technology, the comparison of temperature distribution between new lightweight and traditional ladle under typical operating modes is made and analyzed. The simulation results of temperature field prove that the performance of heat preservation in new kind of lightweight ladle has been improved obviously from the two aspects of ladle shell temperature and molten steel file rate. At the same time, the simulation results of stress field indicate that the stress of designed lightweight ladle reduced and distributed more evenly, which is conducive to prolonging the work time in‐service of the ladle. Finally, based on the field test, the simulation is proved to be effective, and the designed ladle structure achieves the expected purpose.

Evaluation of apical debris extrusion during endodontic retreatment by different systems

Abstract Aim: This study sought to evaluate the amount of apical debris extrusion during the removal of filling material (RFM) performed by the ProTaper-Retreatment (ProTaper-R), Mtwo-Retreatment (Mtwo-R), Reciproc, and hand files. Materials and Methods: Sixty lower premolars were prepared using the ProTaper Universal system and filled with thermoplastic technique. Subsequently, the samples were randomly divided into four groups (n = 15) according to the system used for the removal of the filling material: Mtwo-R (R25/.05); ProTaper-R (D1, D2, and D3); Reciproc (R25); and hand file (type K and Hedstroem stainless steel files). The apical debris extrusion was evaluated before and after the RFM from the root canal by weighing Eppendorf tubes on a high-precision balance. Statistical analysis was performed using the ANOVA test followed by the Tukey's test (P &lt; 0.05). Results: All of the systems produced apical debris extrusion; however, the Mtwo-R group demonstrated significantly more extrusion as compared with the ProTaper-R and Reciproc groups (P &lt; 0.05). There was no statistically significant difference between the Reciproc, ProTaper-R, and hand file groups (P &gt; 0.05). Conclusions: The Mtwo-R group produced significantly more extrusion than did the ProTaper-R and Reciproc groups. There was no difference between the Reciproc, ProTaper-R, and hand file groups.

Agreement Between Working Length Measurements in Primary Teeth Obtained by Radiographs or Apical Locators

Objective: To perform an in vivo evaluation on the agreement between measurements of working length obtained by conventional radiographic examinations and an apex locator in deciduous teeth with or without root resorption. Material and Methods: Nine canals of teeth from children ranging from 3 to 5 years old were selected. Endodontic access was performed with a spherical diamond tip, the pulp was removed with Kerr-type steel files, and the canal was irrigated with 1% sodium hypochlorite. A file, compatible with the channel gauge, was then used to measure the length of the root canal with the apex locator. Conventional radiographs were also performed and, using a millimeter endodontic ruler, the length of the canal was determined. The differences between the measurements obtained between the two methods were analyzed using the Student's t-test. Results: The mean canal length for conventional radiography was 9.83 mm and 9.67 mm for the apex locator. The results of this study did not show significant differences (p=0.641), independent of the presence or absence of physiological root resorption. Conclusion: The similarity in measurements obtained with X-ray or an apex locator indicates that it is not necessary to use X-rays as a complement to obtain the working length. The use of the apex locator can provide a quicker treatment, reducing the clinical time and stress of the child.

Residual root dentin thickness for three different rotary systems: A comparative cone beam computed tomography in vitro study.

Residual root dentin thickness (RDT) in endodontically treated teeth is a major factor that is responsible for longevity of treated tooth. To evaluate and compare the amount of RDT during endodontic treatment using manual K-files and rotary Mtwo, ProTaper Next, and Hero shaper instruments. Anin vitro study was carried out on a sample of 100 freshly extracted human single straight rooted mandibular first premolar teeth. The teeth were divided into five groups of twenty each and mounted on wax rims for a preoperative cone beam computed tomography scan to calculate the dentin thickness 3 and 6 mm from the apex. All the teeth were treated according to their groups. The observations were then statistically analyzed using one-way ANOVA to evaluate the difference among four groups followed by post hoc test for pairwise comparison. Maximum preservation of dentin was seen in Group V (cleaning and shaping done with rotary Hero shaper files) at 3 and 6 mm from the apex, whereas minimum preservation of dentin was seen in Group IV at 3 mm (cleaning and shaping done with rotary ProTaper Next files) and Group II at 6 mm (cleaning and shaping done with hand K-stainless steel files) from the apex. Overall there was a statistically significant difference in RDT values between Group V and Groups I, II, III, IV both at 3 and 6 mm from the apex. Cleaning and shaping with rotary Hero shaper files preserved more amount of dentin when compared to hand K-files, rotary Mtwo, ProTaper Next.