exocad Bar Module: designing implant bars step by step
How implant bars are designed in the exocad Bar Module: pillars and segments, bar profiles, planes and insertion axis, attachments and superstructures.
The exocad Bar Module is the DentalCAD add-on for bar-type prostheses, from bars on prepared teeth to implant-supported, screw-retained bars. It supports several bar shapes in one arch, customizable profiles, attachments and retention pillars. This post walks through a bar design as documented in the exocad wiki for current releases, and adds the checks that matter before the bar goes to production. The same kind of case in Blender for Dental is covered in designing Toronto bridges with iBar.
Setting up the case in DentalDB
The bar design depends on a correct order in DentalDB. In the design, bar pillars mark where the abutments or implants are, and bar segments are the connections between the pillars. If a position is set up wrong in the database, the pillars and segments will be wrong too.
Before designing, make sure you have the scans with scan bodies aligned to the correct implant or multi-unit library (see implant abutment types) and a tooth setup or wax-up that shows the final teeth. The bar has to fit inside that volume.
Choosing the bar profile
When the bar design screen opens, a profile window appears. Select the profile from the Type drop-down. By default a new profile applies to the whole bar, and Apply to selection limits it to the selected segment, which is highlighted in purple with yellow outlines.
The Bar Profile Parameters section changes the shape. A color code shows what each profile allows: green profiles have variable sides and bottom, blue only a variable bottom, red only variable sides, and dark red profiles are fixed. A modified profile can be saved under a new name for later cases. Under the center profile curve, Make curve flat straightens the bar, and Reset curve to default restores it.
exocad notes that bar systems known by trade names are integrated by their component suppliers. exocad provides the technology, and the supplier decides which of its components and library names are integrated.
The Bar Design wizard
The wizard has three tabs. In Profile you choose whether changes affect bar and pillars together, the bar only, the pillars only or the borders only. An option adds borders around the implants to leave room for the papilla. The same tab controls the auxiliary planes and the insertion axis.
In Advanced you switch between a round and an edgy design and set the distance to the gingiva. Auto Level keeps the bar height constant after it has adapted to the gingiva, avoiding dips along the top of the bar, and Min. Pillar Angle sets a minimum angle for the pillars (see the pillar section below).
The Att. tab places attachments. There are four types. An attachment is a mesh added to the construction, a bolted part is a mesh subtracted from it (for example a hole for a prefabricated attachment), a visualizer is shown for reference only, and a retention is added to create retention elements. Attachments can be rotated freely, on top of the bar or according to the current view, and Snap to Gingiva adapts them to the tissue surface. When the bar has to extend beyond the last pillar, the A-P spread shown in the wizard helps judge the extension, and the values change from case to case.
Planes and insertion axis
Two planes guide the design. The green reference plane usually defines the top of the bar. The yellow auxiliary plane runs parallel to it at the height of the selected control point, which shows the height difference at a glance. Drag the green ball to tilt the planes, or double-click a control point to move the reference plane to its height. A plane can also be defined by three points and a height offset.
exocad advises against confusing the reference plane with the occlusal plane. The reference plane is usually parallel to the occlusal plane but much lower.
By default the insertion axis of the bar is perpendicular to the reference plane, so tilting the plane also tilts the axis. To set it independently, uncheck Use plane, look at the design from the desired direction and click Set from view. Other options set the axis from the average insertion direction of the implants or of the teeth. With several bars in one case, Set from view or a shared plane defined by three points aligns them to a common axis and height.
Control points
The bar shape follows control points that you drag with the left mouse button, or along one direction by dragging their arrows.
| Action | Result |
|---|---|
| Ctrl+click | Add a control point |
| Drag a point, then right-click | Remove the control point |
| Shift+drag | Move the point and its neighbors |
| Ctrl+drag | Move the point and further neighbors |
| Ctrl+Shift+drag | Move all points using the insertion plane |
Clicking a cyan arrow links the height of a point to its neighbor, so that segment runs parallel to the auxiliary plane. Clicking a green arrow snaps the point to the reference plane when the planes are visible, and Ctrl+Shift on a green arrow snaps all points at once.
Pillar shape and insertion axis
By default pillars are cylindrical and follow the implant axis. Hold Ctrl+Shift and click a pillar to insert an orange separation line at that height. Below the line the pillar follows the implant axis, and above it the pillar is blocked out along the insertion axis of the bar. Min. Pillar Angle applies only above the orange line.
Custom bar profiles
A custom profile starts from an existing one: change the parameters and save it. Saved as a .barProfile file in DentalCADApp/library/bar, it appears in the profile list the next time the software starts.
Profiles can also be extended with STL meshes oriented with the occlusal direction on Y, the bar direction on Z and the lingual direction on X. exocad strongly recommends the supplied bar library, describes this option as intended for operators experienced with industrial CAD, and does not provide support for problems caused by unofficial profiles.
Designing the superstructure
When the bar is finished and produced, create a new case for the restorations on top of it and select Substructure (e.g. bar) under Implant based? in DentalDB. Scan the finished bar and follow the wizard for the superstructure. The Split Denture workflow is the alternative: it designs the superstructure and the bar in one workflow and splits them into two fitting parts.
Checks before sending a bar to production
- Scan bodies and library match the components the clinician will use.
- The bar stays inside the volume of the planned teeth, with enough space for the superstructure.
- Screw channels exit where the tooth setup allows.
- The section meets the requirements of the material and manufacturing method.
- The patient can clean under and around the bar.
Source: exocad wiki, Bar Module.
Frequently asked questions
What can be designed with the exocad Bar Module?
Bar-type prostheses on prepared teeth or implants, including screw-retained designs and custom abutments. The module supports several bar shapes in one arch, custom profiles, attachments and retention elements.
Where are custom bar profiles saved in exocad?
Save them as .barProfile files in DentalCADApp/library/bar. They appear in the profile list the next time the software starts.
How is the superstructure over a finished bar designed?
Create a new case for the restorations on top, select Substructure (e.g. bar) under Implant based in DentalDB, scan the finished bar and follow the wizard. The Split Denture workflow can also design bar and superstructure together and split them.
Can I import my own bar profile shapes?
Profiles can be extended with STL meshes in a specific orientation, but exocad strongly recommends using the supplied bar library and does not support problems caused by unofficial extensions.