Management of pulp canal obliteration using a combination of dynamic navigation system and dental operating microscope: Case reports with 2-year follow-up

Abstract

The conventional management of teeth with pulp canal obliteration (PCO) carries several risks such as deviation, perforation, and excess dentin removal. Dynamic navigation system (DNS) has recently emerged as a useful tool to improve the accuracy and efficiency of canal localization in teeth with PCO. This article discusses two cases of partial PCO in maxillary anterior teeth with pulp necrosis and symptomatic apical periodontitis which required endodontic intervention. The initial drill path was prepared using DNS. However, there was a deviation in the mid-root region in both cases, and hence with the aid of the dental operating microscope, troughing with ultrasonics was done for the successful negotiation of the apical one-third of the root canals. Both patients were asymptomatic at the 2-year follow-up, and radiographs showed healing of the periapical lesions.

INTRODUCTION

The management of obliterated root canals remains one of the most challenging treatments in endodontics.[1] Canal calcification often results from trauma, aging, or chronic irritation leading to a significant reduction or complete obliteration of the canal lumen.[2] Conventionally, such root canals are negotiated using smaller-sized drills and their path being assessed using periodic radiographs. However, the chances for perforation, canal deviation, or excessive dentin removal is very high and the procedure is also time-consuming.[2,3] With advancements in digital dentistry, there is a growing interest in the use of technologies that enhance precision and clinical outcomes in these difficult cases.[3,4,5]

Dynamic navigation system (DNS), originally developed for implantology, has recently emerged as a novel tool in guided endodontics. By integrating real-time cone-beam computed tomography (CBCT) data with optical tracking and computer-guided navigation, DNS has enabled the clinicians to follow a preplanned access path with excellent precision.[3,6] Literature evidence suggests that DNS significantly improves the accuracy and efficiency of canal localization in teeth with pulp canal obliteration (PCO), reducing the risk of perforation and excessive dentin removal.[7,8,9] This technology not only reduces procedural time but also enhances safety and conserves tooth structure, both crucial factors in long-term prognosis.[5,10]

The dental operating microscope (DOM) has revolutionized endodontic visualization. The high magnification and coaxial illumination provided by the DOM allow for meticulous identification of canal orifices and detailed intracanal exploration. DOMs have been shown to increase the success rate of locating calcified canals and reduce operator fatigue.[11,12]

This paper elaborates two cases of PCO, managed successfully with the combination of DNS and DOM.

CASE REPORTS

In case 1, a 34-year-old male patient reported to the dental clinic with a chief complaint of pain in his left upper front tooth region for 3 days. The patient gave a history of trauma to his tooth during childhood due to a sports injury, after which the tooth had gradually changed color. Clinical examination revealed the presence of a discolored left maxillary canine, which was tender to percussion with no other signs of mobility or periodontal involvement. Tooth #23 was nonresponsive to both electric pulp testing (EPT) and cold test. Intraoral periapical radiograph (IOPAR) revealed obliteration of the pulp canal space in the coronal and middle third with a faint trace of the canal in the apical one-third. To further evaluate the canal anatomy and extent of calcification, a high-resolution small-volume CBCT scan (field of view 4 cm × 5 cm; voxel size of 75 μm) was taken. CBCT confirmed the presence of PCO until the middle third level, and a periapical radiolucency in relation to #23 was also evident. A diagnosis of pulp necrosis with symptomatic apical periodontitis and partial PCO was made.

In case 2, a 41-year-old female patient presented to the dental clinic with a similar chief complaint of pain in her right upper front tooth for 4 days. The patient provided a vague history of trauma to her tooth 15 years ago, after which she again injured her front tooth with a steel water bottle 4 days ago. On clinical evaluation, the patient had a discolored right maxillary central incisor with tenderness to percussion. Physiologic mobility was noted with mild bleeding on probing, and the tooth did not respond to EPT and cold test. IOPAR revealed a narrow root canal space evident only in the apical third of tooth #11. A limited volume CBCT scan (field of view 4 cm × 5 cm; voxel size of 75 μm) was taken which confirmed the presence of partial PCO, with evident loss of canal space in the coronal and middle third of the root, with the presence of a periapical radiolucency in relation to #11. A diagnosis of pulp necrosis with symptomatic apical periodontitis and partial PCO was made, similar to case 1.

The patients were informed of the different interventions (freehand, static guide, and DNS) and their corresponding advantages and disadvantages. The patients in both case 1 and case 2 chose to undergo nonsurgical root canal treatment with the aid of DNS, and written informed consent was obtained for the same. The treatment modality followed in both the cases was similar, as elaborated below.

The CBCT scans of the patients were used to virtually plan the drill path with the Navident 3.0 DNS software (ClaroNav, Toronto, Canada). The drill diameter was set at 1.0 mm in both cases. A virtual drill path length till the first available evidence of root canal space was made in each case, and it was verified in all the planes to ensure appropriate three-dimensional orientation, both in terms of angulation and depth of drilling. Following the “scan” and “plan” phases, the head tracker of the DNS was attached to the patient, and four intraoral tooth landmarks which were chosen on the CBCT scan were “traced” clinically using the DNS tracer tool, so as to match the patient’s jaw to corresponding areas of his/her concerned CBCT. After this, the high-speed handpiece with the attached tracker was calibrated: first, the axis of the handpiece was calibrated, followed by the drill tip of the bur. This step is essential so as to enable the system to continuously monitor the bur’s position and orientation, displaying it in real time on the Navident screen. An accuracy check was run by placing the bur over different areas of the patient’s teeth and verifying that it was reflected as a pointer over the same corresponding areas on the DNS monitor.

Local anesthesia was administered using 2% lignocaine in 1:80,000 adrenaline (Indoco Remedies Ltd., Chennai, India), and the clinical procedure of drilling was commenced subsequently (“place”). Access cavities were initiated with a high-speed handpiece and no. 1/2 size round diamond bur (Prime Dental, Mumbai, India) positioned at the center of the incisal edge. After penetrating a depth of 3-4 mm, the slow-speed endodontic handpiece (NSK Global, Chennai, India) with tracker attached and corresponding burs were calibrated. Gates Glidden drills #1, #2 (Mani INC., Tochigi, Japan) and long-neck round carbide bur (Dentsply Sirona, NSW, USA) were employed to drill through the coronal and middle third accompanied by intermittent irrigation with saline and 17% EDTA (Prime Dental, Mumbai, India). The treating endodontist visualized the DNS monitor and altered the handpiece-bur orientation as per the color-coded signaling from the crosshair view of the DNS and three-plane views of the CBCT sections while drilling. After the planned path had been drilled clinically, an attempt to locate the canal orifice was made using a DG-16 endodontic explorer (Hu-Friedy, Illinois, USA) and a size #8 K-file (Mani INC., Tochigi, Japan). However, the canal was not negotiable after the planned drill path (2/3^rd of the root canal) had been reached using DNS in both the cases. Hence, it was decided to negotiate the canal further using ultrasonics and a DOM (Labomed Prima DNT, Haryana, India). An IOPAR was taken to confirm the drill path created thus far and its relation to the existing canal. It was observed that in both cases, there was deviation of the prepared drill path in relation to the apical canal. Under × 1.6 magnification (DOM), the canal orifice was then located by troughing of dentin with U-files #20 and #25 (Mani INC., Tochigi, Japan). Passive ultrasonic irrigation with Ultra-X (Eighteeth, Changzhou Sifary Medical Technology Co., Ltd., Changzhou City, China) using 17% EDTA was done intermittently to remove the debris that was accumulated during troughing. The canals were negotiated up to the working length using C+ files, sizes #8 and #10 K-file (Mani INC., Tochigi, Japan). After establishing patency, working length was determined with an apex locator and confirmed radiographically. Cleaning and shaping was done using hand files up to size #40/0.02 (Mani INC., Tochigi, Japan) and copious irrigation with 3% NaOCl (Parcan Septodont, New Delhi, India) and 17% EDTA. The canals were dried with paper points (Dentsply Sirona, NSW, USA) and obturated using gutta-percha (Dentsply Sirona, NSW, USA) and AH plus sealer (Dentsply Sirona, NSW, USA) by warm vertical compaction technique. The access cavity was then restored using Tetric N-Ceram resin composite (Ivoclar Vivadent AG, Schaan, Liechtenstein).

The patients were followed up periodically at the 3-month, 6-month, 1-year, and 2-year recall. At the end of 2 years, both patients were asymptomatic; the tooth was functional with no tenderness on percussion. The clinical procedure has been described in Figures 1 and 2 for both the cases.

Figure 1.

Negotiation of pulp canal obliteration (PCO) in #23 using dynamic navigation system (DNS) and dental operating microscope (DOM): (a and b) Preoperative clinical picture and radiograph, (c) sagittal view cone-beam computed tomography indicating partial PCO with patent canal only in the apical 1/3^rd and presence of periapical lesion in close proximity to the zygoma fixation, (d) planning of virtual drill path using Navident DNS software, (e) calibration of handpiece being done, (f) tracker attached to maxilla and handpiece as the clinical procedure is carried out, (g) IOPAR used to assess the prepared drill path when canal negotiation was not possible using DNS, (h) Obturation done after negotiation of apical 1/3^rd using DOM, (i and j) 2-year follow-up of the tooth showing healing with decrease in periapical lesion size

Figure 2.

Negotiation of pulp canal obliteration (PCO) in #11 using dynamic navigation system (DNS) and dental operating microscope (DOM): (a) Preoperative clinical picture of discolored #11, (b and c) sagittal and axial view cone-beam computed tomography indicating PCO with faint trace of canal in the apical 1/3^rd, (d) planning of virtual drill path using Navident DNS software with entry planned from the previously initiated access opening site, (e) IOPA showing tangentially prepared drill path in middle 1/3^rd region and inability to negotiate apical portion of canal with DNS alone, (f) Obturation done after negotiation of apical 1/3^rd using DOM, (g and h) 2-year follow-up of the tooth showing complete radiographic healing

DISCUSSION

The adoption of advanced technologies such as CBCT, DOM, ultrasonic instruments, and guided endodontic systems such as laboratory-fabricated templates and DNS has greatly improved the precision of planning and treating calcified canals, helping clinicians overcome the associated procedural challenges.[9,12,13] Unlike prefabricated guides, DNS offers practical advantages in locating calcified canals, such as improved operating space for irrigation and enhanced visibility.[5] The entire procedure including canal localization and preparatory steps can be performed chairside in a single visit.[5] In vitro studies have demonstrated that DNS offers greater accuracy and efficiency in locating calcified canals compared to the freehand technique[3] while significantly minimizing tooth structure removal.[4] Notably, it achieved a 93% success rate in identifying canals in resin teeth simulated with severe PCO.[14] Hence, DNS was chosen as the preferred mode of intervention in the aforementioned cases. DNS was particularly chosen for case 1 owing to the proximity of the canine root to the zygoma fixation that was already present, which required additional precision and accuracy.

Extended access cavity preparation in a calcified tooth carries the risk of root perforation and if done improperly can complicate subsequent procedures.[15] In both case reports, DNS was used to negotiate the canal till two-thirds of the root length. Subsequent drilling using the DNS with smaller-sized burs in the narrower apical portion led to deviation, which was evident on multiple angulated radiographs. Hence, the apical portion of the canal had to be negotiated under DOM with the aid of ultrasonic troughing and negotiation with C+ files.

The DNS software offers real-time tracking of the bur tip’s precise position, assisting the operator in accurately reaching the predetermined site to locate canals in PCO cases.[7,16,17] In both the cases, the smallest diameter of 1.0 mm was chosen to plan the virtual drill path. This is the lowest possible in-built allowance in the DNS implant planning software as per the operator manual.[18] However, smaller-sized burs of 0.6 mm were used for the clinical procedure, and so there may have been inaccuracies in the exact bur angulation. This ultimately led to a deviation from the planned path in the mid-root region despite using miniature-sized burs. This shortcoming of the DNS needs to be kept in mind while managing cases that are very narrow and having patency only in the apical 1/3^rd region.

The closer the calcification is to the apex, the more challenging it becomes to negotiate.[11] The apical portion of the canal in both the cases had to be negotiated using ultrasonics and DOM. Troughing under magnification with ultrasonic tips enabled better visibility and controlled removal of dentin, allowing for a more conservative approach in the narrow apical region.[19] The DOM helped in identifying the calcified canal orifice by distinguishing the color and textural differences between the normal and calcified dentin through superior illumination and magnification.[11,20]

Although evidence claims that DNS may be a boon in complex endodontic cases,[3,21] there are several difficulties associated with its use. The system requires considerable user adaptation as the operator needs to perform the clinical procedure while looking at the screen with good hand–eye coordination.[3,7,10] It has a significant learning curve which requires performing a minimum of 18–28 cases using DNS to attain the required technical skill.[22] The procedural accuracy can be affected by factors such as poor quality CBCT images which impedes planning, operator hand tremors, and stability of the trackers.[3,7,23] Errors in calibration of instruments can also hamper accuracy. It is important to keep in mind the high cost of investment in the DNS hardware and software which limits its accessibility to all practitioners.[10] Although claimed to take lesser time, DNS workflow integration can be time-consuming due to the need for a preoperative CBCT, planning time, and system setup before the actual clinical procedure can be commenced. Furthermore, as elaborated in this case report, the system’s inability to detect smaller diameter burs may consequently affect the accuracy of the treatment.

The initial path of negotiation in PCO cases is very important, and this was achieved with minimal deviation using DNS in both the cases. The apical one-third of the root canal was not negotiable after the planned depth of drilling had been reached, and so it was decided to use DOM and ultrasonics for further negotiation. In both the cases, when combined with DNS, the microscope augmented the clinician’s ability to perform minimally invasive and accurate canal negotiation. U-files were used in a low power setting of 4 for controlled removal of dentin. The minimum drill size in the DNS is 1.0 mm; consequently, the accuracy of the DNS while drilling below 0.5 mm size has not yet been established, as this is the smallest possible default setting in the DNS endodontic access planning software.[18] Hence, when the obliteration is not negotiable or if the size of the drill is very small, it will be better to switch over to DOM and ultrasonics for further negotiation. Future studies assessing the accuracy of DNS when using smaller-sized instruments are therefore needed. Furthermore, the integration of artificial intelligence may help automate drill path planning and the associated time taken for the same. Combining augmented reality with DNS could also provide intuitive visual overlays directly in the operator’s field in the future.[24]

CONCLUSION

Endodontic management of maxillary anterior teeth with partial PCO (cervical/middle) can be managed successfully using a combination of DNS and DOM.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.