Dynamic Navigation in Endodontics: Guided Access Cavity Preparation by Means of a Miniaturized Navigation System

Root canal treatment of teeth with advanced pulp canal calcification is a challenge. Dynamic navigation systems are able to facilitate minimally invasive endodontic axis cavities. The main advantage of this technique is the minimal invasive detection of calcified root canals, which ensures tooth preservation.

This is also valid for inexperienced operators. The planning procedure can be easily completed following the presented protocol. However, the preparation with the help of the DNS needs practice in order to avoid iatrogenic errors, harming the patient.

To begin, open the planning software and reinsure that the newest version is installed. Click on Expert"to switch the work mode from easy to expert. Click on New"on the right sidebar to start a new case planning.

Choose the image source by selecting the folder with the pre-operative DICOM CBCT data. Select Create data set"to continue with the planning. Choose the type of planning.

Select Edit segmentations"to start segmentation of the dental arch. Switch to axial view on the left sidebar. Select Density measurement"to perform this measurement for the higher radiopaque tooth structure and the surrounding less radiopaque states.

Average the values. Return to 3D reconstruction on the left sidebar. Adjust the lower thresholds to the calculated average value.

Segment by using the flood fill tool. Give a name to the segmentation. Finish segmentation of the dental arch by selecting Close module"Left click on Object"then click Add"followed by Model scan"Select Load model scan"Select Align to other object"Select three different matching points in the registration object and model scan respectively.

Check registration in all the planes by manually scrolling through the planes and finish the registration. Plan axis cavity by adding an implant. Place the burr to the targeted position and check in all the planes by left clicking and moving.

Select object then click Add"followed by 3D model"to add the STL file of the marker tray. Place the tray close to the planned axis cavity preparation. Make sure there will be no interference during the actual procedure.

Add a surgical guide and design the marker tray according to the DNS manufacturer's instruction guide. Export the marker tray as an STL file and manufacture it with a 3D printer. Export the entire planning by selecting Object"then click Virtual planning export"followed by Generic planning objects container"format according to the DNS manufacturer's instruction guide.

Import the planning data to the DNS via the USB. Select the case that is being treated. Insert the marker into the 3D printed marker tray.

Check the fit of the marker in the marker tray. Check the fit of the marker tray on the dental arch. Insert the burr into the handpiece that was used for the planning.

Register the burr in the burr registration tool, according to the DNS manufacturer's instruction. Check the correct registration by moving the burr to a prominent location. The DNS should show the tip of the instrument at the exact same position.

Move the burr to the tooth that will be treated. Perform the axis cavity preparation with DNS guidance. Open Pre-operative planning"in the software.

Select edit segmentations. Adjust the lower threshold to the calculated average value. Segment the treated tooth by using the flood fill tool and give a name to the segmentation.

Finish segmentation by selecting the Close module"option. Right click on the overview column on the left on the segmented tooth and select Convert into 3D model"Right click on the 3D model of the segmented preoperative tooth and then click on Visualization"then click Properties"The volume of the tooth will be displayed in millimeters. Open a new case.

Import DICOM image data of the post-operative cone beam computed tomography scan. Select Edit segmentations"Adjust the lower threshold to the same value that was calculated for the pre-operative data. Segment the treated tooth by using the flood fill tool and give a name to the segmentation.

Finish segmentation by selecting the Close module"option. Right click on the segmented tooth and convert it into a 3D model. Open the Pre-operative planning"import a model scan, then click Import segmentation"and choose the post-operative tooth segmentation.

Align with pre-operative tooth segmentation using landmark registration. The cone beam computed tomography scan of a prepared endodontic cavity is presented in sagittal view. The post-operative segmentation is matched with the pre-operative cone beam computed tomography data.

Pre and post-operative 3D models are matched and the volumes are calculated by planning software automatically. For the accuracy of the entire approach, a precise alignment of CBCT and surface data is necessary. Be critical in the matching process to achieve the best possible accuracy.

DNS were first described and investigated for navigation in implant surgery. Furthermore, they can also be used in dentistry for endodontic surgery.