Using the FA Point when Placing Brackets

When designing IDB trays using the IDB Tray Simulation, you have a tooth feature point – the facial axis (FA) Point. The system draws vertical and horizontal lines based on the axes to provide a reference for bracket placement.

The intersection of the lines is initially set to the FA Point of the tooth. The FA Point is the point on the facial axis that separates the gingival half of the clinical crown from the occlusal half. You can fine-tune the position of the lines as needed and the position of the bracket will adjust automatically if the bracket height set you select is based on FA points instead of bracket heights.

Use the Facial Axis System icon in the guide tools to toggle the FA Point on or off.

Note: If you apply a bracket height set based on FA points, when you open the Bracket Placement tab, instead of seeing only zero in the Occlusal/Gingival row, you may occasionally see some small values instead. These small values each represent a deviation from the absolute value of zero for the FA point. The system creates these deviations as it seeks a secure 3-point contact for each bracket. Slight deviations may be caused if the curvature in the labial surface changes the distance of the bracket from the FA point for the tooth.

Similarly, when relying on FA points to place brackets, results may be unsatisfactory if:

·  the FA Point is manually moved from its ideal position, or

· the tooth surface is not smooth.

How to use the FA Points

Here is a typical use case for using this new feature during an IDB tray simulation

1. Go to the Confirm Bracket Placement step in the IDB checklist.
2. Click the Guide Tools menu and click the FA System tool to display the FA Points on the teeth in the 3D window.
3. In the 3D window, click and drag the FA points/orientation lines as needed. After you move the FA point, the bracket automatically snaps to the new FA point position.
4. Make minor adjustments to fine-tune  the bracket positions as needed