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Table of Contents
Year : 2021  |  Volume : 9  |  Issue : 4  |  Page : 107-110

The accuracy and efficiency of a dynamic 3D navigation system for negotiating calcified canals

1 Department of Conservative Dentistry and Endodontics, Hazaribag College of Dental Sciences and Hospital, Jharkhand, India
2 Department of Conservative Dentistry and Endodontics, Jaipur Dental College, Jaipur, Rajasthan, India
3 Department of Orthodontics and Dento Facial Orthopedics, New Horizon Dental College, Chhattisgarh, India
4 Department of Oral Medicine and Radiology, Hazaribag College of Dental Sciences and Hospital, Jharkhand, India

Date of Submission13-Aug-2021
Date of Acceptance21-Aug-2021
Date of Web Publication27-Dec-2021

Correspondence Address:
Dr. Deepyanti Dubey
Department of Conservative Dentistry and Endodontics, Hazaribag College of Dental Sciences and Hospital, Jharkhand.
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/INJO.INJO_32_21

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Background: Calcified canals present a challenge during endodontic treatments. The purpose of this study was to compare the accuracy and efficiency of a dynamic navigation system (DNS) to the freehand (FH) method for locating calcified canals in human teeth. Materials and Methods: Sixty human single-rooted teeth with canal obliteration were selected and mounted on dry cadaver jaws. Based on cone-beam computed tomographic scans of the jaws, the drilling path and depth were virtually planned to use X-Guide software. The time for locating the canal, the number of mishaps, and the unsuccessful attempts were determined and analyzed. Results: The mean linear and angular deviations, reduced dentin thickness (at both levels), the time for access cavity preparation, and the number of mishaps in the DNS group were significantly less than those in the FH group (P ≤ 0.05). The time for access preparation was significantly shorter for the board-certified endodontist in the FH group (P ≤ 0.05). Conclusion: The DNS was more accurate and more efficient than the FH technique in locating calcified canals in human teeth. This novel DNS can help clinicians avoid catastrophic mishaps during access preparation in calcified teeth.

Keywords: Dynamic navigation, endodontics, guided endodontics, root canal treatment

How to cite this article:
Dubey D, Mandal TK, Verma K, Mitra R, Raj M, Gosh M. The accuracy and efficiency of a dynamic 3D navigation system for negotiating calcified canals. Int J Oral Care Res 2021;9:107-10

How to cite this URL:
Dubey D, Mandal TK, Verma K, Mitra R, Raj M, Gosh M. The accuracy and efficiency of a dynamic 3D navigation system for negotiating calcified canals. Int J Oral Care Res [serial online] 2021 [cited 2022 Jan 19];9:107-10. Available from: https://www.ijocr.org/text.asp?2021/9/4/107/333813

  Introduction Top

Calcified canals present a significant challenge to clinicians during root canal therapy. Healthy, diseased, and even unerupted teeth have pulpal calcifications. Calcification is a process involving reduction in the size of the intradental cavities as a result of hard-tissue formation by the cells of the vital pulp.[1] It may end in complete calcification as a result of constant dentinogenesis. Their prevalence varies widely. The etiological factors for the formation of pulpal calcifications are not well understood; trauma, aging, and various systemic diseases such as cardiovascular diseases could be causes of calcifications.[2] Long-term irritation such as deep caries and restorations with proximity to the pulp has been proposed as possible implicated factors in the development of pulpal calcifications. Pulp canal obliteration (PCO) is mostly associated with dental trauma and occurs in 15–40% of patients after luxation injuries.[1],[2],[3] It may also occur as a pulpal response to caries and restorations[4],[5] and after vital pulp therapy procedures.[6] Furthermore, in the elderly patients, severe progressive calcification of root canal space can be observed due to apposition of secondary and tertiary dentin over time.[7],[8] As Dr John Ingle stated, endodontic access in the elderly becomes less about locating the pulp chamber and more about locating canal orifices.[9] Additionally, calcification of root canal systems may cause an adverse effect of orthodontic forces due to interference with pulpal blood supply.[10],[11]

Aims and objectives

This study is the first to investigate the accuracy and efficiency of a dynamic navigation system (DNS) (X-guide, X-Nav Technologies, LLC, Lansdale, PA, USA) for finding calcified root canals in single-rooted human teeth in an ex-vivo model. The primary goal of this study was to compare the accuracy and efficiency of a DNS to those of a freehand (FH) method for locating calcified canals in human single-rooted teeth using an ex-vivo model. In this research, the following specific aims were pursued in both groups:

Aim 1: Evaluate accuracy (linear and angular deviations) of the drill path in different planes from the planned position.

Aim 2: Compare the time (efficiency) necessary for canal localization.

Aim 3: Compare the reduced dentin thickness at the cemento-enamel junction (CEJ) and at an identified canal level.

Aim 4: Compare the frequency of perforations and unsuccessful attempts in canal identification.

  Materials and Methods Top

This study was an ex-vivo study on a natural tooth model. Sixty (60) de-identified human single-rooted teeth (extracted in the prior 6 months for periodontal reasons) with narrow, partial, or complete canal obliterations (identified by radiographic evaluation) were autoclaved and kept hydrated in distilled water prior to the procedure. Maxillary and mandibular incisors and canines and mandibular premolars were used as test teeth. They were paired according to the calcification status and then each pair was randomly assigned to one of the two main experimental groups and then in each group, samples were randomly divided into two subgroups for two operators. Teeth in each group were mounted with polyvinylsiloxane (PVS) impression material in dried maxilla and mandibles according to their anatomic positions to simulate partially dentate maxilla and mandibles. They were also splinted to each other with composite resin at the incisal third of their proximal surfaces to reduce any subtle movement during the experiment. An extra 40 single-rooted non-calcified teeth were selected and used to calibrate the operators in the use of the x-guide system. Two additional maxillary and mandibular molars were placed on each side of the models to serve as recipients for X-clip fiducials as required by the DNS and also for superimposition purposes.

There were two experimental groups in this study:

  • (1) DNS,

  • (2) FH method.

Two operators [one endodontic resident (OD) and one board-certified endodontist (AN)] planned the access cavity on preoperative cone-beam computed tomographic (CBCT) scans of jaws on their randomly assigned teeth and performed FH or DNS methods based on the randomization process. Each operator performed both methods (DNS and FH) on 30 randomly selected previously matched teeth (n = 15/group).

Scanning protocol for both groups

Before acquisition of the CBCT, a small thermoplastic device (X-clip, X-Nav Technologies, LLC) with three radiopaque markers was molded to molars on one side of the arch (left side for right-handed operator and right side for left-handed operator). This clip held the dynamic reference frames (DRFs) on the model during access cavity preparation in the DNS group. In the FH group, an X-clip was placed on each model similar to the placement in the DNS group to facilitate preoperative and postoperative CBCT superimpositions. To measure the accuracy parameters, a CBCT scan (CS 9300, Care stream LLC, Atlanta, GA, USA) was taken for both groups after the X-clip placement at a 0.090 voxel resolution by school radiology technicians.

Access cavity planning for both groups

The DICOM dataset from the CBCT of both groups was uploaded to X-guide Software and entered into the DNS planning system. However, for endodontic purposes, a 0.5 mm drill template served as the guiding path for the drill during the procedure.

Access cavity preparation for both groups

In the DNS group, access cavities were made under full guidance of the X-guide system. For initial set up, both handpiece and dental models required DRF systems (tracking arrays) and calibration to be identified.

Orientation of the handpiece and head position

The dental model DRF included the X-clip, which was connected to the “patient-tracking cylinder.” The X-clip was placed on the molars in the same position, as it was when the CBCT image was taken. The tracking software algorithm triangulated the two arrays continuously, and live video allowed the operators to get virtual feedback from the navigation system to visualize site preparation. In the FH group, preoperative CBCTs were reviewed and an access cavity was made FH under a dental operating microscope following the virtual planned path using the same type of drill as in the DNS group. The access cavity process was finalized when the final bur reached the end of the planned drill path in the DNS group and when the canal was located and confirmed in the FH group by each operator with a periapical radiograph with a #10 or #15 K-file to an estimated working length. The burs were replaced after each access preparation. Following access preparation in both groups, a second postoperative CBCT scan was taken by one of the dental school radiology technicians with similar exposure parameters as the preoperative CBCTs.

  Results Top

In this ex-vivo natural tooth model study, 30 calcified single-rooted teeth were included in each group. The mean required drilling depth in DNS and FH groups was 12.59 ± 1.93 and 11.75 ± 1.65 mm, respectively, with no statistically significant difference (P > 0.5). The mean linear deviation for both operators using the DNS approach was 0.19±0.21 and 0.12±0.14 mm in the BL and MD directions, respectively, and for the FH technique it was 0.81±0.74 mm in the BL direction and 0.31±0.35 mm in the MD direction. In the BL direction, the DNS group showed significantly less deviation than the FH group (P ≤ 0.001) [Table 1]. [Table 2] presents details of deviation in BL and MD directions divided by operators and in total for both techniques.
Table 1: Linear deviation of two experimental groups in buccolingual and mesiodistal directions

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Table 2: Linear deviation of two experimental groups completed by two operators in buccolingual (BL) and mediodistal (ML) directions

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The mean angular deflection was 2.39±0.85° in the DNS group, whereas it was 7.25±4.2° in the FH group. One-way analysis of variance showed a statistically significant difference between two experimental groups (P ≤ 0.0001). In [Table 3], the measurements of four subgroups can be found.
Table 3: Time required for access cavity preparation, successful attempts frequency, and mishaps in two experimental groups and four subgroups

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  Discussion Top

Accuracy and precision in access cavity preparation and successful localization of canals in endodontic cases with calcified root canal systems are very important especially when we are treating teeth having minimum dentin structure such as mandibular incisors. This appears to be the first study comparing both the accuracy and efficiency of a DNS with a conventional FH method for negotiating calcified canals in a natural tooth model. In this ex-vivo experimental study, we included 30 calcified single-rooted teeth with a drilling depth of more than 9 mm in each group. The mean required drilling depths were 12.59±1.93 and 11.75±1.65 in the DNS and FH groups, respectively. Therefore, all cases were categorized as moderate or high difficulty based on AAE difficulty assessment.[5],[6],[7],[8],[9],[10] The results obtained in the present study reject the null hypothesis (Ho) and show that the X-guide approximated approach using DOM and CBCT-approximated methods in terms of both accuracy and efficiency. This system has the potential to reduce linear and angular deviations of the drill during access preparation, dentin removal both at the CEJ level and inside the canal, intra-operative time as well as complications such as perforation and transportation. The results showed improved performance in angular deflection and linear deviation, especially in the BL direction, but also in the MD direction. The dentin reduction was 1.18±0.17 and 1.47±0.49 mm in the DNS and FH groups, respectively, at the end of the drill (P ≤ 0.05). A success rate of 96.6% was found in the DNS group, whereas the FH group was 83.3% successful. In addition, drilling resulted in five perforations and three large transportations in the FH group and no perforations or transportation in the DNS group. Although the successful attempts did not show any statistical difference between the two groups, they are clinically important. However, the number of procedural errors between the two groups showed a significant difference. Therefore, this tested DNS can assist the clinician in locating the canals safer and in a shorter period of time. Therefore, it is more efficient. However, it must be mentioned that the time needed for virtual planning, machine set-up as well as calibration was not calculated and recorded in this study. Also, it should be mentioned that both operators in this study were experienced in the FH method, which might have biased the results in the FH group. In addition, teeth used in this study were single-rooted teeth with an intact crown or minimal restorations and therefore the required time needed to locate the canal in this study does not reflect the actual time that might be needed in a conventional clinical setting. Further studies using clinicians with more diverse skills and experience levels and more difficult cases (access through the crown and calcified molars) should be explored. In the current study of accuracy measurements, CBCT technology was used, and preoperative and postoperative scans were analyzed.[9],[10],[11],[12],[13] Micro-CT scans provide more precise and accurate data analysis of accuracy but taking micro-CT scans of a full jaw was not practical in this study because of the machine limitation on sample dimensions. Furthermore, for both the DNS and FH groups, CBCT scans were still needed. Application of augmented reality devices and head-mounted displays in addition to DNS can be helpful in transferring and overlaying the virtual plan on the patient jaw and teeth. This can provide the benefit of not losing the track of operation/treatment field and also possibility of using a 3D microscope for magnification. Another limitation is the presence of a bulky handpiece attachment which makes it uncomfortable for routine use.

  Conclusion Top

In conclusion, within the limitations of this ex-vivo study, guided endodontics using the DNS resulted in more accurate and efficient localization of calcified root canals with significantly less reduced dentin structure compared with conventional endodontic access using DOM and CBCTs. Dynamic navigation seems to be a safer and faster technique even for an experienced endodontist than conventional access cavity preparation. However, addressing the system limitations and clinical trials are warranted before its widespread clinical application.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Moss-Salentijn L, Hendricks-Klyvert M. Calcified structures in human dental pulps. J Endod 1988;14:184-9.  Back to cited text no. 1
Oginni AO, Adekoya-Sofowora CA, Kolawole KA. Evaluation of radiographs, clinical signs and symptoms associated with pulp canal obliteration: An aid to treatment decision. Dent Traumatol 2009;25:620-5.  Back to cited text no. 2
Sayegh FS, Reed AJ. Calcification in the dental pulp. Oral Surg Oral Med Oral Pathol 1968;25:873-82.  Back to cited text no. 3
Fleig S, Attin T, Jungbluth H. Narrowing of the radicular pulp space in coronally restored teeth. Clin Oral Investig 2017;21:1251-7.  Back to cited text no. 4
Johnstone M, Parashos P. Endodontics and the ageing patient. Aust Dent J 2015;60(Suppl. 1):20-7.  Back to cited text no. 5
Holcomb JB, Gregory WB Jr. Calcific metamorphosis of the pulp: Its incidence and treatment. Oral Surg Oral Med Oral Pathol 1967;24:825-30.  Back to cited text no. 6
McCabe PS, Dummer PM. Pulp canal obliteration: An endodontic diagnosis and treatment challenge. Int Endod J 2012;45:177-97.  Back to cited text no. 7
Cohenca N, Shemesh H. Clinical applications of cone beam computed tomography in endodontics: A comprehensive review. Quintessence Int 2015;46:465-80.  Back to cited text no. 8
Lang H, Korkmaz Y, Schneider K, Raab WH. Impact of endodontic treatments on the rigidity of the root. J Dent Res 2006;85:364-8.  Back to cited text no. 9
Krastl G, Zehnder MS, Connert T, Weiger R, Kühl S. Guided endodontics: A novel treatment approach for teeth with pulp canal calcification and apical pathology. Dent Traumatol 2016;32:240-6.  Back to cited text no. 10
Zehnder MS, Connert T, Weiger R, Krastl G, Kühl S. Guided endodontics: Accuracy of a novel method for guided access cavity preparation and root canal location. Int Endod J 2016;49:966-72.  Back to cited text no. 11
Connert T, Zehnder MS, Weiger R, Kühl S, Krastl G. Microguided endodontics: Accuracy of a miniaturized technique for apically extended access cavity preparation in anterior teeth. J Endod 2017;43:787-90.  Back to cited text no. 12
Connert T, Zehnder MS, Amato M, Weiger R, Kühl S, Krastl G. Microguided endodontics: A method to achieve minimally invasive access cavity preparation and root canal location in mandibular incisors using a novel computer-guided technique. Int Endod J 2018;51:247-55.  Back to cited text no. 13


  [Table 1], [Table 2], [Table 3]


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