Guided Endodontics: Three-Dimensional Planning and Template-Aided Preparation of Endodontic Access Cavities

Guided endodontics describes a template-aided approach for access cavity preparation. The procedure requires cone-beam computed tomography and a surface scan to produce a template. An incorporated sleeve guides the drill to the target point. This allows the preparation of minimally invasive endodontic access cavities in calcified teeth.

Teeth with severe pop canal calcification and apical pathosis can be very challenging to treat conventionally. Template guided access preparation is a reliable technique that enables tooth preservation. Excess cavity preparation using a template-based approach is minimally invasive, and the access can be accomplished by a less experienced operator.

To begin, start the digital planning program. Right click on Expert to choose the advanced mode. Right click on New to open a new case.

Select the folder with DICOM image data to import the image data to the software. Adjust the Hounsfield unit thresholds if necessary for optimal visualization. Click on Create Dataset to complete the data import.

Choose the type of planning by left clicking on Maxilla or Mandible and name the planning. Click on Edit Segmentations to start the image segmentation process. Choose the axial view by left clicking on Axial in the upper left box.

Click on Density Measurement to measure the high radio pack tooth surface in the surrounding non-radio-pack states. Calculate the mean values between both densities. Set the lower threshold to the determined mean value.

Click on 3D Reconstruction. Segment the dentition with the flood fill tool and name the segmentation as desired. Complete the segmentation by clicking on Close Module.

Add a model scan by selecting Add, then click Object, followed by Model Scan. Import the STL file from the digital surface scan. Choose Align to Other Object.

Select the performed segmentation. Choose three different matching points for landmark registration in the 3D view in both data sets, the segmentation, and the surface scan. Verify correct registration in all planes and complete registration.

Import the endodontic bur into the implant's database. Add an implant to plan the access to the root canal. Position the bur and the desired angulation into the required depth and verify in all planes.

Add the corresponding sleeve to the bur. Select Object, then click Add, followed by Surgical Guide to design the template as preferred. Export the template as a STL file and manufacture it with a 3D printer.

Check the fit of the template on the dentition. Check the fit of the sleeve in the template. Mark the enamel at the access cavity site.

Dye may be used at the bur's tip. Remove the enamel at the access cavity site without using the template or endodontic bur. Use a diamond bur instead until dentin is exposed.

Place the sleeve containing template on the dental arch. Insert the bur into the handpiece that was used for the planning. Perform the access cavity preparation with template guidance.

Use the pre-operative cone beam computed tomography settings to create post-operative image data. Start a new case planning. Import the image data analog to the pre-operative planning.

Click on Edit Segmentations. Set the lower threshold to the determined mean value which was calculated for the pre-operative data. Use the Flood Fill tool to segment the dentition.

Complete the segmentation by clicking on Close Module. Open the pre-operative planning. Select Plan, then click Treatment Evaluation.

Select Post-operative volume data set. Load the correct postoperative data set and choose the generated segmentation. Align pre and postoperative cone beam computed tomography data by choosing three different regions for landmark registration.

Verify correct registration in all plains and complete registration. Place the virtual endodontic bur in the direction of performed access cavity preparation and check in all the planes. The occlusal view of a prepared endodontic access cavity in a first maxillary molar after templated access cavity preparation of the mesiobuccal canal insertion of three endodontic hand files confirmed successful root canal detection after preparation of the palatal and distobuccal access cavities.

After matching the post-operative cone beam computed tomography data to the pre-operative planning data, virtual bur placement generated information about the deviation. Here the angular deviation is 0.7 degrees, 0.74 millimeters 3D deviation at the base of the bur and 0.87 millimeters 3D deviation at the tip of the bur. Following this procedure, endodontic treatment of a invaginatus, removal of manual tri exit aggregate or fiber posts may be enabled.