Accuracy of Working Length Determination of Curved Canal Using Digital and Film-Based Radiography

Introduction: Digital and film-based radiography are the most common methods of working length determination. The objective of this study was to compare the accuracy of working length determination of curved canals using digital and film-based radiography. Materials & Methods: This experimental and interventional study, included forty teeth with curved canals conducted at the Dentistry Faculty of Isfahan University of Medical Sciences, in 2018. After access cavity preparation, the direct observation method of the apical tip of the file in the root apex determined the actual working length. Teeth were mounted in acrylic blocks. Canal curvature was calculated based on Schneider’s method using software of indirect digital radiography. Images gathered by E-speed film and digital sensors. A pre-curved file was used to measure the working length of film-based images. In digital radiography, a digital caliper was used to measure the working length with three and six clicks. Data were analyzed by repeated measure analysis, paired t-test, and Intraclass Correlation Coefficient. The Level of significance was set at 0.001. Results: All groups overestimated the actual length although there weren’t any significant differences (p value > 0.05). Paired t-test didn’t show any significant differences between digital and film-based groups (p value > 0.05). Conclusion: Considering several advantages of digital radiography over the film-based method, it is the preferred method for working length determination of curved canals.

Comparison of the accuracy of different electronic apex locators used in working length determination via changing of initial cleaning solutions

Aim: The aim of this study is to compare the accuracy of the Root ZX Mini, Raypex 6, E-Pex Pro, and Propex Pixi electronic apex locators by changing the initial cleaning solutions (NaOCl vs. EDTA). Methodology: Eighty mandibular premolar teeth were used. Radiographs were obtained from the mesio-distal and bucco-lingual angles for all teeth, and teeth with suspected external or internal root resorption and/or calcified canals were not included in the study. The true canal lengths of the teeth were determined with a precision of 0.01 mm with a stereomicroscope at x5 magnification by placing a #20 K-type canal file into the root canal. The samples were then embedded in freshly mixed alginate blocks up to the cemento-enamel junction. The coronal 1/3 was pre-enlarged with a Protaper SX instrument. Electronic apex finders (Root ZX Mini, Raypex 6, E-Pex Pro, Propex Pixi) specified on each tooth were used, and measurements were made by changing the initial solutions (NaOCl vs. EDTA). Distilled water was used between application of 5.25% NaOCl and 17% EDTA to prevent chemical interactions. Three measurements were taken for each tooth, and the average of these 3 measurements was taken as reference. The data obtained in this study were analyzed. Results: There were no statistically significant differences between the solutions in terms of the measurement values and actual length values found by each device (p>0.05). Although there were no statistically significant differences, the deviation from the actual measurement was greater when EDTA solution was used than when NaOCl solution was used. In addition, although the difference was not found to be statistically significant, the deviation from the actual measurement was found to be highest when the Root ZX mini device was used with NaOCl and EDTA solution. Conclusion: The results of this study showed that the difference in the initial washing solutions did not affect the EAL devices in making measurements close to the true length. How to cite this article: Tellioğlu Avcı GR, Kaya S Comparison of the accuracy of different electronic apex locators used in working length determination via changing of initial cleaning solutions. Int Dent Res 2021;11(Suppl.1):56-62. https://doi.org/10.5577/intdentres.2021.vol11.suppl1.9 Linguistic Revision: The English in this manuscript has been checked by at least two professional editors, both native speakers of English.

Measuring the Canal Length - A Review

The objectives of root canal treatment are elimination of microorganisms, removal of pulpal remnants, removal of debris, and shaping of the root canal system so that it may be obturated. The most important step in endodontic therapy is canal preparation which can be achieved by accurate working length determination. Working length determines the extent of placing the instruments into the canal, it affects the degree of pain and discomfort which the patient will experience post treatment and it plays an important role in the success of the treatment if placed within correct limits. The cementodentinal junction, where the pulp tissue changes into the apical tissue, is the ideal physiologic apical limit of WL because at this point healing is supposed to be optimal, and the wound to the periapical tissues is minimal.The apical constriction is however, histological and is impossible to locate clinically or radiographically. There are several methods of determining working length which include radiographical methods, digital tactile sense, apical periodontal sensitivity, paper point method and electronic apex locators. The requirements of an ideal method for determining working length include rapid location of the apical constriction in all pulpal conditions, easy measurement, rapid periodic monitoring and confirmation, patient and clinician comfort, minimal radiation to the patient; ease of use in special patients; and cost effectiveness. To achieve the highest degree of accuracy in working length determination, a combination of several methods should be used. This article reviews the different methods to determine WL and their clinical implications. KEY WORDS Working Length, Apex Locator, Radiographic Method.

Contract Length Determination in the B2B Service Industry: Role of Economic Factors, Business Relationship, and Learning

In B2B markets, when firms sign contracts for transactions pertaining to the exchange of services that are delivered over a period of time, one critical decision they make is the length (or duration) of the contract. If the services are hired for a long project, companies often sign multiple, successively run contracts with the same vendor. This is prevalent in projects such as when multinational companies hire consulting firms like Accenture to streamline and digitize their business processes, when big banks in developing countries hire firms like Tata Consultancy Services to extend banking facilities into rural markets, and when oil companies hire rig firms to drill oil wells. From a traditional economic perspective, companies would decide on an optimal contract length that is not too long or too short; the former disables the firms from reacting to market changes while the latter makes negotiation costs expensive. However, when a company signs a series of successive contracts with a service-firm, both companies get to learn about the other company’s goals and operations dynamically, which might influence the length of each contract in the series. Thus, determining the contract length in a series of successive contracts is more challenging. In this study, we build a contract length determination model that considers both the economic factors and the dynamic learning. The model provides managers with a theoretical yet practical tool to make optimal decisions on contract length. We use data from the oil-drilling industry to empirically test the proposed model.

Homologous Over-Expression of Chain Length Determination Protein EpsC Increases the Molecular Weight of Exopolysaccharide in Streptococcus thermophilus 05-34

In Streptococcus thermophilus, EpsC is a polysaccharide co-polymerase which is involved in determining the chain length of EPS synthesized by the Wzx/Wzy-dependent pathway. Our previous study found that there was a positive correlation between transcription level of epsC and molecular weight of EPS in S. thermophilus 05-34. To further investigate the effects of EpsC on EPS biosynthesis, this gene was over-expressed in S. thermophilus 05-34 in this study. Reverse transcription qPCR and Western blotting confirmed the successful transcription and translation of epsC in 05-34, respectively. The yield of EPS was not affected by the over-expression of EpsC. Gas chromatography-mass spectrometry (GC-MS) showed that the monosaccharide composition was still composed of galactose and glucose in a molar ratio of 1.0:0.8, whereas high performance gel permeation chromatography (HPGPC) indicated that the molecular weight of EPS was increased from 4.62 × 105 Da to 9.17 × 105 Da by the over-expression of EpsC. In addition, S. thermophilus 05epsC which could produce higher molecular weight EPS improved the viscoelasticity and water-holding capacity of yogurt, but significantly reduced the level of syneresis in yogurt. In summary, these results indicated that homologous over-expression of EpsC in S. thermophilus could increase the molecular weight of EPS and improve the microrheological or physical properties of yogurt.