LIMITATIONS AND MANAGEMENT OF DYNAMIC NAVIGATION SYSTEM FOR LOCATING CALCIFIED CANALS

LIMITATIONS AND MANAGEMENT OF DYNAMIC NAVIGATION SYSTEM FOR LOCATING CALCIFIED CANAL FAILURES: A CASE REPORT

1. Limitations and Management of Dynamic Navigation System for Locating Calcified Canals Failure: A case Report Xiaoxia Yang, MDS, Yinchun Zhang, MDS, Xuan Chen, MDS, Lei Huang, MDS, and Xiaoling Qiu, DDS, Phd JOURNAL CLUB PRESENTATION BY DR. ABDUL KADIR MDS 3 RD YEAR DEPARTMENT OF CONSERVATIVE DENTISTRY AND ENDODONTICS

2. CONTENTS INTRODUCTION AIMS AND OBJECTIVES MATERIALS AND METHODS CASE REPORTS DISCUSSION CONCLUSION REFERRENCES

3. INTRODUCTION Pulp canal obliteration (PCO), also called pulp canal calcification or calcific metamorphosis, is the progressive narrowing or complete blockage of the pulp canal space. This process involves secondary dentin or tube-like calcified structure deposits within the canal walls, associated with dental trauma, vital pulp therapy, revascularization, caries and restorations, physiological changes in elderly patients, genetic factors and systemic factors. Teeth with PCO that require root canal treatment (RCT) pose a challenge in locating the canal, which causes iatrogenic complications including perforation, separated instruments, and increased risk of endodontic treatment failure. Based on the Endodontic Complexity Assessment Tool, teeth with PCO are considered at high risk of complexity for RCT.

4. The use of advanced equipment like the cone-beam computed tomographic (CBCT) scanner and dental operating microscope, the ultrasonic instrument for removal of obstructions, and emerging technology-guided endodontics like the lab-fabricated template and dynamic navigation system, has increased the accuracy in planning and treatment of calcified canals, and has allowed operators to overcome these challenges. DNS is an alternative intervention for teeth with calcified canals. DNS combines 3-dimensional (3D) CBCT imaging reconstruction and spatial location registration technology using an optical tracking system controlled by a dedicated computerized interface to provide real-time navigation, guiding the operator to drill following preoperative planning.

5. AIM AND OBJECTIVE Nonsurgical endodontic teeth treatment with severe pulp canal obliteration poses challenges, primarily locating canals . By combining 3-dimensional reconstruction and spatial location registration, the dynamic navigation technique uses an optical tracking system to guide the clinician to drill in real time according to the predesigned path until access to the canal is established. This work presents the manipulation process and clinical outcomes of a dynamic navigation system that helps in calcified canal location.

6. MATERIALS AND METHODS CLINICAL PROCEDURES OF THE DYNAMIC NAVIGATION TECHNIQUE: Preoperative CBCT Scanning : The patient was impressed with a U-shape registration device (DCARER, Suzhou, China) containing 9 radiopaque fiducial markers. The target teeth and 1 or more adjacent teeth were covered with silicone impression material (Silagum Putty, DMG, Hamburg, Germany). The patient the registration device on the target teeth area and underwent CBCT scanning ( i -CAT, Imaging Sciences International, Hatfield, PA) with the following parameters: 120 kVp, 5.0 mA, 160 x 60 mm field-of-view, and 0.25 mm voxel size.

7. Preoperative Drill Path Designing : The CBCT data were uploaded to the endodontic navigation system software (DHC-ENDO1; DCARER, Suzhou, China) in Digital Imaging and Communications in Medicine format. According to the laws of centrality, concentricity, and cementoenamel junction (CEJ)21, the drill path was designed to pass through the CEJ center in the coronal, sagittal, and horizontal views of CBCT imaging Calibration and Registration: The principle of calibration and registration was based on an optical tracking system that emits infrared light. The handpiece and the reference devices were calibrated, collecting information on the different planes of the handpiece wings using long and short round bur, respectively. The reference device was fixed with bis-acrylic resin (Luxatemp, DMG, Hamburg, Germany) onto the contralateral side of the identical dentition to be relatively stationary with the targeted tooth . Therefore, DNS can track the dynamic position of the handpiece concerning the targeted tooth using the reference device.

8. At least 7 fiducial markers in the CBCT imaging were selected in the software for registration, and the short round bur with the handpiece was intraorally moved to contact registration points one by one. Virtual and intraoral conditions were registered with the pairing between the fiducial markers in CBCT imaging and their actual positions. After calibration and registration, the DNS computed the space position between the target tooth and handpiece to guide treatment in real time. Real-Time Dynamic Navigation: The pulp chamber opening and canal locating were performed under the DNS. Before tooth drilling, the short round bur was placed in the mesial, distal, and central positions of the target tooth at different angles to confirm the correct tooth position, calibration, and registration. Without disrupting the reference device, the rubber dam was placed in the targeted tooth. DNS constantly tracked the handpiece wings and reference device, providing visual feedback to the operator.

9. The dynamic movement of the actual drill path was presented as images on a screen, including the location, angle, and depth, with CBCT imaging and predesigned drill path. The location and angle windows displaying "green" revealed that the actual drill path was clinically within an acceptable range. depth window displayed "green" to indicate that the bur was within the predesigned depth. Once the bur reached or exceeded the predesigned depth, the depth window showed a "red" warning.

10. CASE REPORTS: CASE 1: A 27-year-old woman visited the Department of Endodontics on 31 March 2022, complaining about a pustule of her maxillary right anterior tooth for 2 months. She underwent orthodontic treatment for 14 months and had suffered dental trauma 10 years earlier. Clinical examination revealed that teeth #7 and #8 presented physiologic mobility and no percussion tenderness. However, teeth #7 and #8 did not respond to thermal (cold and heat) and electrical pulp tests, and a sinus tract was present on tooth #8 mucosa (Fig. 2A–C). Periapical radiography revealed that teeth #7 and #8 had calcified pulp chambers and canals, discontinuity lamina dura of tooth #7 apex, and apical radiolucency of tooth #8 (Fig. 2D). Tooth #7 was diagnosed with pulp necrosis and PCO, and tooth #8 was diagnosed with pulp necrosis, chronic apical abscess, and PCO. RCT was performed on teeth #7 and #8. The canal location procedure for teeth #7 and #8 was performed with the help of DNS (Fig. 2E–H).

11. Because the handpieces were not adapted, the low-speed handpiece and high-speed handpiece were used alternately to access the cavity (Fig. 2G). The low-speed handpiece with small round bur was used for location, including establishing position and direction. A high-speed handpiece with a small round bur was used for drilling, with a depth of 1 mm to 2 mm at one time. Drilling and locating procedures were repeated several times until the canals were determined successfully (Fig. 2H). However, tooth #7 lost excessive tooth structure in the mesial to the canal orifice, probably because tooth #7 was microdontia. 98 Yang et al. RCT was performed as previously described (Fig. 2I–K). The initial apical file (IAF) of teeth #7 and #8 was 6# file. The WL of tooth #7 was 18 mm, and tooth #8 was 21 mm. Both master apical files (MAFs) were 25#. The sinus tract on the buccal side had healed (Fig. 2L–N). One year later, the patient underwent CBCT scanning for orthognathic surgery, which confirmed the healing of teeth #7 and #8, with apical radiolucency disappearance (Fig. 2 O and P)

12. CASE 2: A 59-year-old man was referred from the Department of Periodontology for endodontic treatment on 24 June 2022, resulting from periapical radiolucency of tooth #9. The patient complained of abnormal left upper front teeth mobility for several months. Clinical examination revealed deep overbite (Fig. 3A). A premature contact of tooth #9 was noted in protrusive movement. Tooth #9 had discoloration (Fig. 3B) with grade 1 mobility. Tooth #9 experienced pain to vertical percussion but no response to thermal (cold and heat) and electrical pulp tests. The periodontal pocket of tooth #9 was 5 mm to 7 mm in probing depth, with gingival bleeding upon probing and discharge of pus (Fig. 3C). Periapical radiography revealed calcified pulp chambers and narrowing in the canal; tooth #9 had apical radiolucency and half of the alveolar bone loss (Fig. 3D). CBCT images showed that alveolar bone loss and apical bone defects were not through-and-through (Fig. 3E). Tooth #9 was diagnosed with symptomatic apical periodontitis (SAP), PCO, and chronic periodontitis. The therapeutic schedule was RCT combined with periodontal treatment. The drilling equipment was adapted as a high-speed handpiece (Fig. 3F).

13. A round bur was used to drill the enamel, and a long-shank fissure bur was used to drill the dentin (Fig. 3G). The canal was located without excessive loss of tooth structure (Fig. 3H). RCT was performed as previously described (Fig. 3I and J). The IAF was8#and prepared to MAF of 35# with a WL of 23 mm. After RCT, the patient accepted periodontal treatment at the periodontology department. After 3 months, the patient was asymptomatic, and the tooth mobility had normalized. However, periapical radiography revealed overfilled sealer movements (Fig. 3K). Oral examination and radiographic monitoring were recommended. After 1 year, the periapical radiography revealed that apical radiolucency and sealer extrusion decreased in size (Fig. 3L). The periodontal condition of the patient improved (Fig. 3M–O)

14. CASE 3: A 29-year-old man was referred from the Department of Orthodontics on 27 June 2022; he was diagnosed with apical radiolucency in the mandibular anterior teeth. The patient had received adequate endodontic treatment for tooth #25 3 months earlier. Clinical examination showed that the mandibular anterior teeth were abraded (Fig. 4A–C). Mobility of teeth #23, #24, and #26 was within normal limits. Tooth #23 had percussion and cold pulp test pain without response to heat and electric pulp tests. Teeth #24 and #26 had no percussion pain or sinus tract, whereas they did not respond to the thermal (cold and heat) and electric pulp tests. Periapical radiography revealed an apical radiolucency in teeth #24 and #26, and calcified pulp chamber and narrowed canal in teeth #23, #24, and #26 (Fig. 4D). Tooth #23 was diagnosed with symptomatic irreversible pulpitis and PCO; teeth #24 and #26 were diagnosed with pulp necrosis, asymptomatic apical periodontitis, and PCO. RCT with the assistance of DNS was performed on teeth #23, #24, and #26. The drill paths of teeth #23, #24, and #26 were designed (Fig. 4E–G).

15. The radiographic imaging features of the periapical radiography revealed that tooth #23 might present 2 canals. However, this could not be confirmed by CBCT imaging because the canal space was completely calcified obliterative, hence it was difficult to design the drill path. Therefore, the endpoint of the drilling path of tooth #23 was designed at the CEJ level (Fig. 4E). Canals of teeth #23 and #24 were finally located under DNS, and tooth #23 single canal was confirmed. However, the direction of tooth #26 distally deviated at the cervical one-third, and failed to locate the canal with DNS (Fig. 4H). CBCT imaging confirmed that the drilled path distally deviated in the coronal plane (Fig. 4I). Endodontist 1 revised the drill direction and located the canal under the DOM. RCT was performed as previously described (Fig. 4J). The IAF of teeth #23, #24, and #26 was 8# file, with WL of 21.5 mm, 20 mm, and 21.5 mm, respectively. After preparation, the FWW was 0.25 mm, and tooth #26 canal geometry altered mildly. After 6 months and 1 year of follow-up, the apical radiolucency had resolved, with periapical bone healing (Fig. 4K and L). The treated teeth and mucosa were normal (Fig. 4M–O)

16. CASE 4: A 45-year-old man visited the Department of Endodontics on 27 June 2022, complaining of discomfort in his upper left front teeth while chewing for the previous 2 weeks. The patient had suffered dental trauma for more than 20 years. Tooth #9 mobility and probing depths were within normal limits (Fig. 5A–C); however, it had percussion tenderness and did not respond to thermal (cold and heat) and electrical pulp tests. Periapical radiography revealed an apical radiolucency with a calcified pulp chamber and narrowed canal (Fig. 5D). Tooth #9 was diagnosed with SAP and PCO, hence RCT with the assistance of DNS was performed. In the first time of drilling tooth #9, the endpoint of the drill path was designed at the CEJ level (Fig. 5E); however, the operator did not locate the canal when the bur reached the predesigned depth. After redesigning the path (Fig. 5F), the operator drilled the tooth again without a fresh calibration and registration; the location and angle window displayed "green," which seemed to be the “correct path.

17. However, the canal could still not be located (Fig. 5G). The drill path deviated severely mesialy from the cervical one-third to the middle one-third of the root canal (Fig. 5H). CBCT scanning was performed to establish the deviation. We observed that the drill path deviated similarly to the designed path during the initial attempt (Fig. 5I). Endodontist 1 revised the drilling direction and located the canal at the CEJ level, with the direction of distal and labial sides from wrong access, under the DOM (Fig. 5J). RCT was performed as previously described (Fig. 5K). The IAF was an 8# file and prepared to 0.45 mm of FWW, with a WL of 21 mm. With a 1-year follow-up (Fig. 5L–O), periapical radiography revealed that periapical bone had healed around the overfilled sealer (Fig. 5L).

18. DISCUSSION Guided endodontics using a prefabricated guide template or dynamic navigation is a safe and minimally invasive method for calcified canal location. However, existing studies and our unpublished case series indicate that a prefabricated guide template has limitations. First, the low-speed handpiece is used for drilling dentin structure, which is inefficient. Second, template insertion increases the difficulty of placing the rubber dam, rinsing dentin debris in the cavity, and lack of vision. Third, patients with restricted mouth opening associated with treating posterior teeth might exert this technique as a counter indication. Importantly, the drill path was predetermined and guided by a template, which could not be changed during operation. DNS resolves these challenges. Unlike prefabricated guide templates, DNS has operational benefits in calcified canal location, including rubber dam placement, cavity rinse, operating space, and vision. Without template manufacturing, the process can be completed chair-side in a single visit, including canal locating and preparatory work, suited for patients with acute pain.

19. Although several case reports and in vitro studies have shown comprehensive operating procedures and success with DNS there are disadvantages, including an unaffordable navigation system also, a learning curve and training are required for operators, including operating by looking at a monitor and not the patient. Moreover, information regarding safety and adverse events is lacking. Operators should be cautious about possible failures and observe preventive measures to prevent iatrogenic complications. Based on DNS workflow, calibration and registration were performed after path design. If the path is redesigned during operation, it must be re-calibrated and re-registered for the DNS to update the spatial position of the actual drill and designed paths .

20. CONCLUSION This case series presents some limitations of DNS for locating calcified canals and the need for more technology research could improve endodontic procedures in the future.

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