Dynamic navigation system: a revolutionary technology for endodontic microsurgery

Drs. Frederico Martinho and Bruno Giliolli Bisi discuss the use of guided navigation in the endodontic practice

Over the past decade, technology has revolutionized endodontics. The ultimate goal of technology is to improve root canal treatment outcomes and tooth survivability rates.^1,2 Root canal treatment failure is an ongoing issue despite technological advances; therefore, the search for new technology continues.³

Treating persistent apical periodontitis (PAP) is routine for an endodontist,⁴ and non-surgical root canal treatment (NSRCR) is one of the treatments for PAP.⁵ However, NSRCR can be affected by numerous factors.⁵ Endodontic microsurgery (EMS), which has been widely explored lately, is also a treatment option for PAP. The introduction of new technologies, including magnification and ultrasonics, and the development of new endodontic sealers and retro-filling materials have revolutionized EMS.¹

Guided EMS has recently received a lot of attention.⁷ New technologies have enabled surgeons to treat more complex cases with more predictable outcomes. It allows the surgeon to deliver a more accurate and efficient minimally invasive treatment.² Guided EMS requires pre-surgical planning in planning software, and the surgery can be delivered under static or dynamic navigation.

Static navigation requires printing a 3D surgical guide.⁹ Several studies have shown that surgical guides improve EMS accuracy and efficiency when compared to freehand.³ However, surgical guide design and production have a complex workflow with numerous steps that can be time-consuming and require multiple appointments.⁴ Additionally, the software for surgical planning, 3D printing, and other related functions requires some surgical knowledge and training.

The Dynamic Navigation System (DNS) is a new technology in endodontics, and it is like a GPS for the handpiece and the drill.⁵ DNS has a more straightforward workflow (Figure 1) and is less time-consuming than static navigation.⁶ Previous studies revealed DNS’s high accuracy and efficiency for EMS.⁷ DNS enables the surgeon to deliver a minimally invasive EMS. Its high accuracy allows endodontists to conduct EMS in more difficult cases, such as areas with no direct visualization and close to vital anatomical structures. To date, DNS has been explored for different EMS steps, including bone window,⁸ osteotomy, and root-end resection (RER).⁹ DNS can improve the accuracy and efficiency of EMS performed both by novice and experienced endodontists.¹⁰

Dynamic Navigation System

Currently, only a few companies offer DNS. These include the X-Guide^® (X-Nav Technologies, Lansdale, Pennsylvania), the Navident (ClaroNav, Toronto, Canada), the ImplaNav™ (Bres Medical, Ingleburn, Australia), and the Denacam (Liestal, Switzerland). All these DNS systems share a similar navigation concept despite different manufacturers. These DNS software applications are overall very user-friendly with a straightforward workflow.

DNS has numerous components. The main components include a central console, a display for the user interface, a section in the upper part containing motion-tracking cameras, and a lighting system, which varies from manufacturer to manufacturer (Figure 2). The cameras identify the DNS trackers that are attached to the patient’s face and to the handpiece and create a precise 3D model of the surgical site and the handpiece’s relation to the site regarding the angle, spatial position, and drilling depth.⁵

To plan for DNS surgery, the cone beam computed tomography (CBCT) Digital Imaging and Communications in Medicine (DICOM) file is directly uploaded into the DNS software. A key advantage of the DNS is that it does not require separate software to open and visualize the CBCT scan. Once the CBCT scan DICOM file is in the DNS software, the surgeon can plan the EMS procedure. After surgical planning, the DNS software requires a calibration step, in which the software recognizes the trackers attached to the handpiece and the patient’s dentition and memorizes their geometry to ensure that the handpiece and the drill are accurately represented on the planned drilling path. It has been suggested that the pre-surgical steps should not take more than a total of 15 minutes.⁶ After calibration, the DNS software becomes live for navigation, guiding the user to the drill at the correct angle and position. The DNS software guides drilling in real-time, and when the desired depth is reached, the DNS software indicates to stop, and the procedure is completed.

DNS has a learning curve like other technologies. It is crucial to undergo thorough training before treating a patient although the DNS is easy to operate, which makes the DNS learning curve less steep. A relatively low number of trial attempts are sufficient to calibrate the operator on DNS prior to the surgery.¹¹ A previous study showed that after 20 trial attempts, both novice and experienced endodontists delivered EMS more accurately and efficiently than freehand.⁵ Overall, the DNS has a less challenging learning curve and is easy to fit into the surgeon’s existing EMS workflow.

Dynamic Navigation System EMS studies

Early studies evaluated the accuracy and efficiency of DNS for osteotomy and RER.^9,10,12,13 Accuracy is a primary concern when performing EMS (Figure 3), especially in areas close to important anatomical structures, in which small deviations could lead to partial or irreversible damage to local structures. Surgical time is critical for EMS, and cutting down the EMS time is desirable. Optimizing the EMS surgical time with technology could avoid operator and patient fatigue, loss of anesthesia, and excessive bleeding, which can affect visibility and the outcome of the surgery. It is worth highlighting that the longer the surgical time, the higher the risk of technical error. Therefore, keeping the surgical time short using technology could also help to prevent mishaps.

Early studies have compared the accuracy and efficiency of DNS to the freehand method.¹³ Despite no fair comparison, it was still important at that time to prove that the DNS technology could enable the surgeon to conduct a more accurate and efficient EMS than the freehand existing method.

EMS involves many steps, including osteotomy, root-end resection, root-end cavity preparation, and root-end filling.¹⁴ All these steps are crucial for EMS success.¹⁵ Each EMS step can be a source of error, and cumulative errors can ultimately impact the EMS outcome and longevity of the tooth. To date, DNS has been mainly explored for osteotomy, bone-window cut, and root-end resection.^8,9,10,12,13 Previous studies have demonstrated the high accuracy and efficiency of DNS for osteotomy and root-end resection.^9,16 Most of these studies indicated 2D- and 3D-deviation metrics below or close to 2 mm.^10,12 Moreover, these studies also showed a lesser root-end resection angle compared to freehand surgery.⁹

Bone window or “bony lid” surgery was introduced in 1987 for direct surgical access to the apical root of mandibular molars for root-end resection¹⁶ (Figure 4). It is an alternative surgical method to conventional osteotomy using burs or drills. The procedure involves preparing and removing a bone window, which is then reinserted into its original position after the surgery. One advantage of bone window surgery is that it preserves and maintains bone that would have been removed by conventional osteotomy with burs (Figure 4). The bone window works as an autogenous graft without substitute materials for guided tissue regeneration providing essential bone remodeling factors, including osteoinductive molecules, proper scaffolding, and osteogenic cells.^18,19

Recently, DNS was successfully applied for a bone-window surgery⁸ study which was the first to integrate X-Guide software into a piezoelectric device for bone window cutting in EMS (Figure 5). The authors showed that DNS improved the accuracy and efficiency of EMS piezosurgery. Piezosurgery’s many advantages include the ability to perform minimally invasive procedures, preserve neurovasular structures, control bleeding, and reduce thermal damage.^23,24 The piezosurgery preserves more of the cancellous properties and more osteocytes than traditional osteotomy.²² Moreover, piezosurgery offers less edema, less trismus, reduced pain, and improved quality of life after the surgery.²³

The DNS has several applications in endodontics.^24,25 In addition to EMS, DNS has been mainly tested for intraosseous anesthesia, conservative access, locating calcified canals, root post-removal, and root post-preparation.⁵

Future directions

DNS will be updated with new features as the technology evolves. Endodontic techniques and applications are encouraged. Recent studies integrated DNS into augmented reality (AR) headsets for mixed reality.²⁶ AR is one of the biggest technology trends in the medical field. DNS integration into the AR headset allowed the surgeon to overlay the high-definition AR content of the live output display from the navigation system near the surgical site through the Microsoft HoloLens 2 AR headset. AR integration with DNS improved surgeons’ hand-eye coordination and also overcame 3D DNS’s disadvantage, which was the need to simultaneously pay attention to both the surgical site as well as the output of the DNS display. The HoloLens AR headset allowed the operator to remain focused on the surgical site while drilling for RER and osteotomy without having to look away at the DNS monitor.¹⁶ The DNS has attracted attention from both clinicians and researchers lately. As the DNS technology advances, more studies are needed to evaluate the clinical accuracy and efficiency of DNS for EMS.