Root Canal Anatomy Visualization using Three-Dimensional Computed-Tomography and Transparent Preparation

Three-dimensional Computed Tomography (CT) is used to analyze the topography of the root canal anatomy in order to make a decision in choosing root canal preparation method. There is a method that make extracted teeth transparent maintaining its anatomical shape and size. It is important to compare the accuracy of the two visualization methods. Objective: To compare the transmission accuracy of root canals anatomy by two visualization methods, three-dimensional CT and transparent tooth preparation. Methods: Mandibular third molar was used as sample. The three-dimensional CT scan was performed before extracting the teeth. Then teeth were extracted and placed in solutions that made them transparent. Results: Despite the fact that the character of dental origin in terms of the angle of the crown, the curvature of the crown, the deviation of the root showed in three-dimensional CT, other tooth anatomical parameters were equally well detected using a transparent tooth preparation. Overall, the curvature of the root canals is more clearly shown by transparent tooth preparation. Conclusion: Transparent tooth preparation provides superior visualization of real root canal anatomy compared to three-dimensional CT, however the later could give us more information about the relation of the tooth within the jaw.


INTRODUCTION
A detailed understanding of the root canals, their shape and the number is the foundation of endodontics. 1 Features of the structure of the root canal are needed by dental practitioner when performing endodontic treatment.Attempts to gather possible configuration about root canal have been performed, but conflicting information about the structure of the root canal is still present.It is caused by the fact that each tooth might have unique configuration. 2,3The anatomical features of the tooth root canal would influence the type of endodontic instruments used. 4Radiographs, which are more than a century helps physicians in endodontic therapy, are two-dimensional and do not give complete information about the cavity of the tooth. 5In recent years, dental computed tomography is used for the examination of patients with pathology of the teeth and jaws. 6By obtaining three-dimensional digital image of the tooth, it is possible to view the tooth from three projections and significantly enhances diagnosis in endodontics. 7Despite the emergence of new technologies and improvement of facilities, the question of endodontic treatment quality remains important.There is a high risk of instruments breakage in curved root canals.Therefore it is important to find out how exactly 3D KT transmits anatomy, is it possible to use this method to reduce the number of complications in the root canals treatment.
In order to visualize the anatomical features of root canal of a tooth, we have developed a method of transparent tooth preparation on tooth, which allows to get a visual three-dimensional image of the entire root canal system while maintaining the total volume of the dentine of the tooth.This invention is registered for patent No. 2373582 dated November 20, 2009. 8The question of endodontic treatment quality remains important-there is a high risk of instruments breakage in curved root canals.The purpose of the study was to compare the transmission accuracy of root canals anatomy by two visualization methods-threedimensional CT and transparent tooth preparation.

METHODS
A lower right third molar was chosen as one of the teeth being studied.The patient underwent removal of the 48 was asked to participate voluntarily in the study and a written informed consent form was granted.A three-dimensional dental CT was performed using i-Cat Vision (CT Dent Ltd, UK) according to manual instruction.The i-Cat scanner is specially designed for dental use and its technology is known as Cone Beam CT (CBCT).CT scan uses multiple small bursts of radiation, dispersed from various angles toward the target area, rendering detail images from different angles on film.Patients were asked to remove all metallic items before beginning, including eyeglasses.Patients were asked to remove any dentures.Lead aprons were provided to help protect the patient's internal organs from the radiation exposure.
The tooth was then extracted and cleaned.The endodontic access was subsequently created (Figure 1B).The tooth was treated by a procedure which allows to make the extracted tooth transparent.The patent for transparent tooth preparation is No. 2373582 of November 20, 2009. 8The method included tooth storage in sodium hypochlorite solution.This step would cause oxidation and hydrolysis of organic compounds -proteins (including the key enzymes of cells), as well as osmotically draw fluid from the cells, resulted in increased in tooth porosity (Figure 1A). 9,10rthermore, the tooth was placed in an acid solution in order to dissolve enamel and to cause dentin demineralization.This method would process the tooth in its entirety and would maintain dentin, so that minimize changes in the structure of the tooth root canals.After demineralization the tooth was placed in an alcohol solution for the dehydration.
To complete the process necessary to create a transparent tooth preparation was impregnating the sample with a solution, which was an aromatic organic compound derived from benzene.Due to the fact that this solution has a refractive index was close to  Steps of transparent tooth preparation.A: the tooth was treated with a solution for five minutes, after which marked changes in transparency, the outer surface of the root; B: showed a tooth that was in the solution for 30 minutes, an increase in the degree of transparency; C: showed the resulting clear product of the tooth, the pulp inside the tooth was visible.Exposure of a tooth in the solution was one hour; D: showed a clear product of the tooth in the air, which was capable of for a long time to maintain its transparency.the refractive index of the dentin organic matrix, the tooth would become transparent.Figure 2 showed the process of increasing the transparency of the tooth, which began as impregnating tooth solution.To identify the structural features of the root canals of the extracted tooth, together with the methodology of the visualization was made tooth tissues coloring with water-soluble dye.The dye bound to dentin proteins (Figure 3).

RESULTS
The three-dimensional dental CT allowed estimation of the location of the 48 with respect to its bony structures, and other teeth in the lateral projection. 11Figure 4 showed the location of 48 from buccal view.Computer diagnostics revealed intra-osseous location, shape, size and structure of the tooth with a high accuracy, as well as a cross-sectional images of the longitudinal section of the tooth crown and root of 48, which indicates the presence of two root canals in Figure 5C.
On a transparent preparation of the tooth it is clear that pulp cavity has a greater volume than what is seen on CT (Figure 3).Two thin and curved root canals were seen in the 48 using three-dimensional CT and transparent tooth preparation.Application of the developed technique allowing three-dimensional visual imaging of the entire root canal system while maintaining the total volume of the dentine of the tooth.The apical portion of the tooth, through colored dye is clearly visible (Figure 3), the tip of the tooth is not formed, is similar to slit-like structure.

DISCUSSION
Three-dimensional computed tomography allows accurate diagnosis to determine the localization features of the teeth relative to other anatomical structures in the maxillofacial region as well as knowing the presence and severity of inflammation in the periapical region.This visualization would optimize the evaluation of the tooth therefore helps preparation of instruments and as well as reducing the risk for both endodontic and prosthetic treatment failure.
The method of computed tomography can realistically assess the amount of roots, root canals, the degree of curvature of the root, as well as spliced roots.At the same time during the study we found that the degree of curvature of the root canals are not always clearly visible on CT 3D, there is uncertainty due to the large resolution to clarify the course of the root canal.On a transparent remote preparation of the tooth is possible to estimate the true degree of curvature of the root canal because of the visualization.
The results of the two methods are compared visually.Comparison of several criterias of the tooth using images on CT and transparent tooth preparation summarized in Table 1.The criterias include number of roots, number of root canals, the degree of curvature of the root, the degree of curvature of the root canal, finger-joined roots, the outer surface of the relief, the angle of the crown, the curvature of the crown, the deviation of the root, with respect to the localization of anatomical structures.
In Figure 5C on 3D CT, we define the presence of two root canals.However, additional information about the curvature of the root which forming a S-shaped form in the medial root and the presence of another curvature in the two-third of the root was showed in transparent tooth preparation.Transparent preparation of the extracted teeth is indispensable as a visual aid for the high-level training in endodontics section.This method allows students to see the native structure of root canals, with apical Deltas and the isthmuses between the channels, additional channels and the curvature degree.Understanding the anatomy of root canals and optimizing their preparation by selecting the appropriate method of root canal treatment can improve the quality of endodontic treatment. 12e quality of endodontic treatment of root canals remains actual.There are many methods of root canal treatment, the method chosen due to its anatomical features. 12If there is no accurate information about the degree of curvature of the root canal, in a case of complex anatomy the physician cannot be at a preliminary stage to choose a method of processing, which will significantly reduces the degree of complications of root canal preparation.

CONCLUSION
Transparent tooth preparation provides superior visualization of real root canal anatomy compared to three-dimensional CT, however the later could give us more information about the relation of the tooth within the jaw.

Figure 1 .
Figure 1.Initial steps of transparent tooth preparation.A: after the tooth was treated with sodium hypochloride; B: endodontic access was performed.

Figure 2 .
Figure 2.Steps of transparent tooth preparation.A: the tooth was treated with a solution for five minutes, after which marked changes in transparency, the outer surface of the root; B: showed a tooth that was in the solution for 30 minutes, an increase in the degree of transparency; C: showed the resulting clear product of the tooth, the pulp inside the tooth was visible.Exposure of a tooth in the solution was one hour; D: showed a clear product of the tooth in the air, which was capable of for a long time to maintain its transparency.

Figure 3 .
Figure 3. Introduction of dyes after transparent tooth preparation.A: after dye introduction resulting the outer surface of the 48 relief; B: presence of two root canals which were connected with a wide isthmus; C: after further processing of dyes, the tooth cavity and root canals were filled with blue-colored dye, dentin showed a yellowish with large amount of pulp chamber; D: the tip of the tooth has not been formed, showing a slit-like structure.

Table 1 .
Comparison of several tooth anatomical criterias using three-dimensional CT and transparent tooth preparation