Determination of root canal curvatures before and after canal preparation (part II): A method based on numeric calculus

Digital Determination of Curvature of Root Canals of Extracted Teeth

Introduction: Determination of the curvature of root canals at present is accomplished by complicated or expensive methods. Therefore, there is a need to develop a new digital method by which this curvature can be determined quickly, easily and accurately.

The aim of this in-vitro study is to determine the angles of curvature of the root canals of extracted teeth by comparing a new digital method of measurement with an established digital method.

Material and Methods: Forty-eight (48) root canals of extracted teeth were studied to achieve the goal. In all roots, curvature is measured by three methods: Method 1 – new digital photographic method and special Software (Screen Protractor); Method 2 – a new digital radiography method and special software (Screen Protractor); Method 3 – approved method, digital by X-ray and special Software (Durr dental).

Results: The mean degrees of the measured curvature of the root canals in all three groups are similar and are about 22°. There are no statistically significant differences between them (p > 0.05).

Conclusion: This shows that the new digital photographic and x-ray methods for measuring root curvature can accurately determine the curve angle for extracted teeth.

Continuous Measurement of Three-Dimensional Root Canal Curvature Using Cone-Beam Computed and Micro-Computed Tomography: A Comparative Study

The knowledge of root canal curvature is crucial regarding the prevention of ledge formation, root perforation and the possibility of endodontic instruments’ fracture during endodontic treatments. Therefore, a quantification method of the root canal curvature as well as the applicability of diagnostically relevant tomographic three-dimensional (3D) imaging data is necessary. Hereby, cone-beam computed tomography (CBCT) images and micro-computed tomography (µCT) data of distal root canals were analysed concerning the continuous three-dimensional curvature of human mandibular molars (n = 50). The curvature of the canal’s three-dimensional centre line was determined by evaluating the tomographic images. The centroids of each root canal slice were identified and approximated by spline curves to obtain the centre line and therefore, its curvature. Comparing the results evaluated from CBCT and µCT images, minimum radii of curvature of 2.6 mm and 2.1 mm were determined, respectively. The observation of the centre line demonstrated the requirement of the three-dimensional imaging data from CBCT and µCT for a reliable curvature analysis. Conclusively, the evaluation of CBCT and µCT images results in comparable radii of curvature. Thus, the application of the introduced method in combination with CBCT applied to patient cases could offer an important preliminary diagnostical step to prevent endodontic treatment complications.

Canal shaping with a reciprocating system is easy to learn

AIM

To assess progressive learning of root canal shaping in order to define the number of simulated canals in resin blocks needed to reach a level of learning beyond which no further improvement in performance is observed.

METHODOLOGY

A total of 216 simulated canals in resin blocks were instrumented by 18 operators without experience in Endodontics and by 18 Endodontists. The R25 file of the Reciproc system (VDW, Munich, Germany) was used to prepare the canals. The blocks were photographed before and after instrumentation. An analysis was made of the variations in the dimensions of the canals at 6 locations and of the instrumentation time. A Student's t-test was used to analyse the data (P < 0.05).

RESULTS

The group without experience were associated with significant differences in instrumentation time between the first canal and the subsequent canals (P < 0.05) but differences in canal dimensions were not significant (P > 0.05). In the group with experience, the instrumentation time did not differ significantly after the fifth canal, and no significant variations in canal dimensions were observed (P > 0.05).

CONCLUSIONS

When conducting studies on root canal shaping or educating students with new instruments, a simulated canal sample size of 6 was appropriate to achieve competence.

Methods for measurement of root canal curvature: a systematic and critical review

The assessment of root canal curvature is essential for clinical and research purposes. This systematic review presents an overview of the published techniques for the measurement of root canal curvature features using imaging and to provide a critique of their clinical application. A database search in PubMed, PubMed Central, Embase, Scopus, EBSCO Dentistry & Oral Sciences Source and Virtual Health Library was conducted, using appropriate key words to identify measurement methods for root canal curvatures. The search strategy retrieved 10594 records in total, and 31 records fulfilled the inclusion criteria. From 2D image acquisitions, eleven studies measured exclusively the angle of curvature, an additional thirteen measured other curvature features (level, height, radius, length and shape). Seven reports described methods from 3D imaging (CBCT, μCT). Root canal curvatures should be measured, for clinical proposes, to facilitate endodontic treatment planning, and in research, to reduce the risk of selection bias. This review has revealed that there are many methods described in the literature; however, no consensus exists on which method should be used. Some of the methodologies have potential clinical translation, whereas others are suitable for research purpose only, as they require a specific software or radiographic exposure in the mesiodistal direction.

Influence of operator's experience on root canal shaping ability with a rotary nickel-titanium single-file reciprocating motion system

INTRODUCTION

The aim of this study was to evaluate the influence of the operator's experience on the shaping of double-curvature simulated root canals with a nickel-titanium single-file reciprocating motion system.

METHODS

Sixty double-curvature root canals simulated in methacrylate blocks were prepared by 10 students without any experience in endodontics and by 10 professionals who had studied endodontics at the postgraduate level. The Reciproc-VDW system's R25 file was used in the root canal preparation. The blocks were photographed before and after the instrumentation, and the time of instrumentation was also evaluated. Changes in root canal dimensions were analyzed in 6 positions.

RESULTS

Significant differences (P < .05) were found in the apical transport of the first root canal curvature, with a larger percentage of increase of the root canal occurring in the novice group than in the expert one, as well as in the canal deviation at the beginning of the curvatures, whereas no significant results were obtained in the growth rate of the canal area. There was difference in the time of instrumentation, with 3.76 minutes observed in the novice group, as opposed to 2.05 minutes in the expert group.

CONCLUSIONS

The use of the single-file reciprocating motion system Reciproc is not seen to be influenced by the operator's experience regarding the increase of the canal area. Previous training and the need to acquire experience are important in the use of this system, in spite of its apparent simplicity.

The determination of the initial straight length in root canals of mandibular premolars--an in vitro study

The aim of the present roentgenographic in vitro study was to determine the initial straight length from the cemento-enamel junction (CEJ) to the appearance of a root canal curvature in human mandibular premolars. A total number of 282 mandibular premolars were examined. Exclusion criteria comprised root caries, extensive restorations and endodontically treated teeth. The teeth were fixed and digitally radiographed by means of a specially developed fixation device with standardized and reproducible distances with the parallel technique (Heliodent MD; Merlin 2.1). The distances from the CEJ to the first curvature (> 5°) (distance I), from the first curvature to a second curvature (distance II), and from the first or second curvature to the radiological apex (distance III) were recorded. The lengths of the initial straight distance and the appearance of a curvature were statistically analyzed and related to each other. In first mandibular premolars, the mean value for distance I was 10.9 mm, for distance II 3.7 mm and for distance III 3.04 mm. The mean values for the second mandibular premolars were 1.1 mm in distance I, 4.3 mm in distance II and 3.1 mm in distance III. No statistically significant differences between left and right mandibular premolars could be observed regarding the canal curvature location and the angle values. The results of this investigation show that curvatures are increasingly observed 9 to 12 mm from the original path in mandibular premolars.

Wear promoted in the apical third of simulated canals after instrumentation with ProTaper universal system

OBJECTIVE

This study evaluated the wear in the apical third of simulate canals after preparation with ProTaper Universal Rotary System.

MATERIAL AND METHODS

24 sets of instruments were used in 24 simulated canals in transparent epoxy resin blocks with degree of curvature of either 20 degrees or 40 degrees. The canals were photographed preoperatively and after preparation of the apical stop with ProTaper F3, F4 and F5 instruments. The initial and final images were exported to Adobe Photoshop software and superimposed to detect the root canal wall differences (in mm) between them, in two points located 1 (A) and 5 (B) mm from the point where the working length was established. Data were subjected to analysis of variance to verify the existence of interaction among the factors: canal curvature, instrument size and curve location. Significant level was set at 5%.

RESULTS

Regardless of the location and the canal curvature, F4 and F5 instruments produced the greatest wear (p<0.05).

CONCLUSIONS

There was a deviation from the original pathway towards the outside of the root curvature in both analyzed points. All instruments produced canal transportation, but the F4 and F5 instruments produced more than the other instruments, and should thus be used with care in curved canals.

In vitro incidence of root canal bifurcation in mandibular incisors by radiovisiography

OBJECTIVE

The aim of this study was to verify, in vivo and in vitro, the prevalence of root canal bifurcation in mandibular incisors by digital radiography.

MATERIAL AND METHODS

Four hundred teeth were analyzed for the in vivo study. Digital radiographs were taken in an orthoradial direction from the mandibular incisor and canine regions. The digital radiographs of the canine region allowed visualizing the incisors in a distoradial direction using 20 masculine deviation. All individuals agreed to participate by signing an informed consent form. The in vitro study was conducted on 200 mandibular incisors positioned on a model, simulating the mandibular dental arch. Digital radiographs were taken from the mandibular incisors in both buccolingual and mesiodistal directions.

RESULTS

The digital radiography showed presence of bifurcation in 20% of teeth evaluated in vitro in the mesiodistal direction. In the buccolingual direction, 17.5% of teeth evaluated in vivo and 15% evaluated in vitro presented bifurcation or characteristics indicating bifurcation.

CONCLUSIONS

Digital radiography associated with X-ray beam distally allowed detection of a larger number of cases of bifurcated root canals or characteristics of bifurcation.