Static vs. dynamic navigation for endodontic microsurgery - A comparative review

Abstract

Digitalization of operative procedures through three-dimensional (3D) navigation is a remarkable advancement in the field of dentistry which allows both precision and accuracy while treating patients. It is an emerging technology with a wide variety of applications in dentistry. In the field of endodontics, these computer-aided 3D systems are being used for accessing and localizing canals in calcified teeth, removal of fiberglass posts, and in peri-apical surgeries etc.

Preservation of important anatomical structures becomes necessary while performing root-end resection or peri-apical surgeries. However, it is clinically difficult to achieve accurate root-end resection due to the limited field of view, inconvenient perspective, and interferential bleeding among other factors. 3D guided endodontics play vital role here. 3D guided endodontics can be achieved in two ways- Static and Dynamic navigation.

Due to availability of limited literature, there is a need to review new evidence comparing the effectiveness of both techniques of 3D guided endodontic navigation systems. This review paper describes the comparative evaluation of the effectiveness of static as well as dynamic navigation in the field of endodontic microsurgery.

Graphical abstract

1. Introduction

Digital systems are becoming ubiquitous in our lives and interconnectivity has drastically increased since the start of this millennium. Digital systems have taken important place in dentistry also. These digital systems include cone-beam computed tomography (CBCT), 3D printed objects, dynamic navigation, haptic simulators, intra oral cameras, cancer detection system etc.

3D printed objects are models and templates produced using a computerized process using CBCT data. They are based on virtually rendered dentition and associated skeletal tissue. The automated process involves devices such as 3D printers, which use different 3D printing techniques to produce objects.¹ Dynamic navigations are computer systems that generate interactive 3D virtual simulations of teeth and skeletal tissues by replicating the likely challenges of various treatment procedures and provide multisensory peri-operative feedback in real time.²

3D imaging and technology are extensively used in the field of oral and maxillofacial surgery and for implant placement in the jaw. Endodontic microsurgery has also started to utilize the wide opportunities of 3D technology, amongst which CBCT has already established its inimitable position. 3D printing as static guidance and dynamic navigation methodologies are gaining popularity in endodontics; for negotiation of calcified canals, peri-apical microsurgeries etc. One of the challenges for practitioners during endodontic surgery is to figure out the exact location of root-end resection.³

In modern endodontic surgery, 3 mm of the root end is generally removed, and the resection plane is made perpendicular to the long axis of the tooth to control infection better, reduce dentinal tubule exposure, minimize the possibility of micro-leakage and conserving the remaining tooth tissues. Operating near important anatomical structures adds to the complexity of the procedure. Precise root-tip resection is difficult to achieve due to limited field of view, awkward perspective and interfering hemorrhage are among other factors. However, with the introduction of CBCT, static and dynamic navigation, the success rate of surgical endodontics has rose from 44.2-53.5% to 90.5–31.1%.⁴

The accuracy and precision offered by static and dynamic navigation might be different. As a result, the challenges that these targeted endodontic treatments would pose would need to be benchmarked. Thus, there is a need to review new evidence comparing the effectiveness of both techniques of 3D guided endodontic navigation systems. This review paper describes the comparative evaluation of the effectiveness of static as well as dynamic navigation in the field of endodontic microsurgery.

2. Static guidance

The 3D endodontic guide or endoguide is a template made to guide drills in predetermined positions for locating and exploring root canal orifices or bone trephination and root end resection.⁵ It is also known as endodontic guide, endoguide, endodontic template, 3D endodontic guide, or surgical guide.

The surgical guides are used mainly for endodontic surgeries, especially for root-end resection procedures. According to the region providing support, endoguides can be tooth, mucosa, or bone supported. The surgical endodontic templates can be used for soft tissue retraction, template for cortical preparation, a template for pilot guide, or a full guide for bone trephination and root end resection.

The major steps of 3D guided planning and designing are; CBCT scan of the involved tooth or teeth along with the adjacent area, the surfaces scan, merging the CBCT scan and surface scan with a software, designing of endodontic guide, and sleeve selection.

3. Dynamic navigation

The 3D guides besides being expensive, must be fabricated in advance and cannot be modified after manufacture. In contrast, however, Dynamic navigation a recent technology uses a stereoscopic monitoring camera to dynamically guide the operator's instruments to the correct location for the implant placement, root canal localization, root-end resection, etc. in real-time.

Dynamic navigation is designed to guide the placement of drills/implants in real-time by a computer. Patient's CBCT data would assist the navigation process. Dynamic navigation is analogous to a global positioning system (GPS) and the basic setup of the system consists of a stereoscopic camera, a computer platform with a screen, and the respective navigation software. The entire procedure for dynamic navigation can be concise under plan, trace, and drill. The plan is: access cavity preparation or creating surgical window and restoration placement using the CBCT image. This plan can be modified at any time. Trace is: registering the CBCT scan to the patient by selecting landmarks on the screen and tracing around those landmarks in the mouth with a tracer tool. Drill is: preparing the tooth or bone under dynamic guidance. The basic components of any dynamic navigation system are handpiece attachment, patient jaw attachment, the system cart consisting of a camera, computer with navigation software, and a natural or fiducial marker that are used during the radiological scan as reference points for instrument registration.

The contribution of dynamic navigation continues to expand in the field of endodontic microsurgery. But the case reports of endodontic microsurgery using dynamic navigation are very much limited. The results of the case reports are satisfying as the dynamic navigation system made exact root apex localization and accurate apicoectomy possible in a minimally invasive manner.⁶

4. Comparison of guided endodontic surgery

Static and dynamic navigation is already well explored in the field of surgery and implant dentistry. But in the field of endodontic microsurgery, these two navigation systems are slowly progressing and the number of case reports for targeted surgical endodontics is scanty till now. The comparison of static and dynamic navigation is tabulated below;(Table 1)

Table 1.

Comparison of static and dynamic navigation.

Property	Static Navigation	Dynamic Navigation
Preoperative imaging/impression	CBCT & Diagnostic impression/Oral scanner	CBCT
Devices required	Surgical guide, Surgical motor, Piezosurgical unit, Dental operating microscope, Periapical instruments, Surgical instruments	Hand piece attachment, patient jaw attachment, the system cart consisting camera, computer with navigation software and natural or fiducial markers
Working protocol	Imaging, Image registration/merging, Surgical plan, Final digital plan, Template fabrication, Try on, Guided surgery	Plan, Trace, Drill
Operator accessibility	Limited and not possible to modify treatment plan once the guide is fabricated	Good and possible to modify procedure plan at any time of treatment
Accuracy	Comparatively less	More
Advantages	•Accurate details and reproduction of scan providing good quality of work and consistent results •It is possible to print complex geometric shapes and interlocking parts that require no assembly •Reduction of production-related material loss •It is possible to produce single objects in small quantities at low cost and fast delivery	•Errorless and superior in accuracy •Reduces potential risk of damaging critical structures •Greater flexibility offered to the operator •Adjustments dictated by clinical situation can be made to the working plan at any time
Disadvantages	•Possibilities of inaccuracy in image registration and 3D printing •Crescent shape of resected root apex •Larger deviations, Over penetration •Trephine fracture •Lack of long term success •3D guides are not re-useable •Resin guides cannot be heat sterilized, Resin used in messy condition can cause inflammation and irritation on contact and inhalation	•Longer surgical time •More steps & Learning curve •Possible inaccuracies during registration •Entire procedure is supervised by computer software; any time lag for processing commands in computer might lead to iatrogenic errors.

5. Discussion

The field of endodontic surgery has extended beyond root-end resection to include other forms of periradicular surgery, fistulative surgery, corrective surgery, and intentional replantation; even though root-end resection is the still most common. But the challenges and intrications of periradicular surgery by magnification-assisted free hand dentistry are still enumerable. The concept of utilizing some form of guidance increased the success and overcame the challenges of periradicular surgery up to an extent. By using the static surgical guide, it is possible to have a consistently accurate and reliable approach to the tip of a root by minimizing the risk of damaging vital structures by giving an accurate replication of the CBCT data-driven software design. So inaccuracy in any one of the steps can lead to errors, which are not being modifiable at the time of surgery. Precision and accuracy are important for static guided endodontics. Operator accessibility with the static guide in posterior region is challenging and the absence of an adequate number of teeth in the arch would reduce the stability of the guide. Modern guides use calibrated trephines so that the penetration depth of the drills can be monitor can avoid iatrogenic errors. Surgical simulation comparison done by T.K Hawkins et al.⁷ showed targeted endodontic microsurgery provided more efficient completion of osteotomy and resection, with a more appropriate root-end resection volume and bevel angle than the traditional microsurgery. Another case report by Shangzhu Ye et al.⁸ concluded that the digitally designed template worked in all aspects to facilitate the periapical surgery as anticipated the root-ends were accurately located, resected and gave simplified, effective treatment with minimized iatrogenic errors. Evidence from three case reports given by C. Michelle Giacomino⁹ showed targeted endodontic microsurgery produced an osteotomy site with predictable angulation, diameter, and depth concerning maxillary second molar palatal root, fused disto-facial palatal root of maxillary first molar, and mandibular second premolar. Thus the conclusion the study was guided endodontics could prove to be an important breakthrough allowing precision-guided surgery in anatomically complex areas for teeth that may have otherwise required extraction. Endo guide assisted root-end resection on maxillary first molar done by Georg D. Strbac¹⁰ concluded the same. On the other hand, the cylindrical shape of the osteotomy design using sleeves would reduce the efficiency of cleaning and debridement of the surgical site. No failures have been reported, however, the resected root apex may remain crescent-shaped or sharp edges may be resorbed. Like guided implantology, the deviation that can happen from the planned surgical pathway is similar in the case of endodontic microsurgery i.e. 3⁰ to 5°. Unexpected trephine fractures are reported in in-vitro studies so there are possibilities of fracture of trephine or guide itself that can happen in real-time because of poor designing or fabrication of stent.

Dynamic navigation is already in use and well evaluated in the field of implantology but for endodontic microsurgery, its efficacy need to be evaluated. Unfortunately the case reports of endodontic surgery using dynamic navigation are very less documented. Except for the huge cost of the machine and operator learning curve, dynamic navigation gives a favorable result. Another limitation that can come across is iatrogenic error that can happen during the procedure because of the time lags for processing commands in the computer. The system allowed the precise localization of the root and accurate apicoectomy with a minimal invasive cavity, avoiding errors. Contemporary systems for dynamic navigation offer one more advantage that the drill automatically stops working when the handpiece moves away from the planned pathway of operation, those iatrogenic errors can be prevented and vital structures can be preserved.

Root end resection of endodontically treated maxillary right lateral incisor done by Gianluca Gambarini ¹¹ concluded that the outcome of treatment was considered a success with less postoperative discomfort because of the minimally invasive technology and the healing was good. As compared to static guided endodontics, dynamic navigation offers immediacy, predictability, safety, and access for the site of operation. Furthermore, it is simpler, more accurate and having flexibility of treatment modification in the process of treatment. Patient radiation exposure can be minimized by taking a single CBCT for the entire procedure.

6. Conclusion

The conclusion derived from the present study is that static and dynamic computer-aided navigation techniques are highly accurate and precise to perform endodontic microsurgeries apart from the initial upfront cons dynamic navigation is simpler, efficient, errorless, and less technique sensitive than static navigation. Further studies will be required in the field of computer-aided navigation to compare the accuracy of such systems in more challenging anatomic conditions.