Measuring Maxillary Posterior Tooth Movement: A Model Assessment using Palatal and Dental Superimposition

Dental movement assessment is important when evaluating orthodontic treatment outcomes. We are going to be demonstrating a method to evaluate three-dimensional movement of maxillary posterior teeth when they have undergone clear aligner treatment. This protocol offers a combination of several software tools as well as palatal rugae and dentition as stable references.

This combination allows for the superimposition and segmentation of individual teeth for the purpose of analyzing their movements and orientations. This protocol demonstrate a novel method to analyze the differences between software predict models and the actual treatment outcomes. By understanding the efficacy and the accuracy of software predicted treatment, clinicians will have a better judgment planning the tooth movement.

To begin, launch the CloudCompare software on a computer. Select the posttreatment digital maxillary model and click the translate rotate icon. Drag the model so they are side by side and click the green check mark.

Choose the pretreatment digital model and click the segment icon. Choose four points on the palatal rugae and right-click to deselect. Then click on segment in and press the green check mark.

Hide the posttreat model remaining and pretreat model remaining models. Then select the posttreat model part and pretreat model part models. Press the rough registration alignment icon and place at least three landmarks on each side of the midline for both pallets.

Click Align, then the green check mark to confirm the landmark placement. Next, unhide the meshes for both models. Then copy the unformed posttreat model remaining model.

Click on Edit, followed by Apply Transformation and paste the transformation matrix. Hide the dot remaining models and select both the posttreat model part and pretreat model part models. Now press the fine registration alignment icon and choose the pretreat model part model as the reference, then click OK.Unhide the meshes for both models, then move the untransformed post treat model remaining model as done earlier.

Click on Edit and Apply Transformation and paste the transformation matrix. To begin, launch the Rhinoceros Software on a computer system. After importing the relevant STL files, select the simulated gingiva and press Delete to remove it.

Click on Mesh Tools and select Mesh Plane. Draw a plane around the teeth and move it to the occlusal 1/3 third of the tooth crowns. Double click the right button to expand the right view.

Next, enter the command MeshBooleanSplit. Select the plane and all the teeth, and then press Enter. Delete the plane and cervical portions, leaving 1/3 of the occlusal tooth crowns.

To begin, launch the CloudCompare Software. After importing the relevant superimposed files, uncheck the corresponding boxes to hide the split predicted model and the posttreatment digital model. Then select the split pretreatment model and pretreatment digital model.

Now click the rough registration alignment icon and place corresponding landmarks on the crowns'cusps for both models. Press Align, followed by the green check mark to confirm landmark placement. Unhide the split predicted and posttreatment models.

Copy the transformation matrix, then click Edit followed by Apply Transformation. Paste the matrix to move the model. Now hide the posttreatment and split predicted models, then select the pretreatment and split pretreatment models.

Press the fine registration alignment icon, unhide the meshes, and move the transformation matrix as before. Finally, unhide the split predicted and posttreatment digital models, then hide the pretreatment split and digital models to show the superimposition. To begin, launch the Meshmixer Software on the computer.

After importing the split predicted and posttreatment models, click on the icon to hide the split predicted model, keeping the posttreatment digital model visible. On the posttreatment model, click select and adjust the brush size. Drag the brush tool on the occlusal surface of the selected tooth to segment the crown.

Now, click Modify, followed by Invert and Edit, then discard to delete the rest of the model, leaving only the segmented crown. Click on the icon again to unhide the split predicted model and hide the posttreatment model. To begin, launch the CloudCompare Software on the computer.

After importing the segmented crown files, hide the posttreatment tooth. Then select both the hidden posttreatment tooth and the visible predicted tooth. Now choose the bottom view and click the translate rotate icon.

Use the X, Y, and Z planes to rotate the tooth so the buccal cusp aligns with the vertical line. Select the left side view and click the translate rotate icon, then line up the buccal and lingual cusps with the horizontal line. Similarly, choose the back view and line up the buccal and lingual cusps with the horizontal line.

Once all cusps are aligned, click the translate rotate icon and center the tooth on the grid in all views. Now unhide the posttreatment tooth and select both the predicted tooth and the posttreatment tooth. Press the fine registration alignment icon to register the posttreatment tooth over the predicted tooth, then click OK.Then choose the posttreatment tooth, copy the transformation matrix and press Edit, followed by Apply Transformation to paste the transformation matrix.

Finally, select the Euler angles icon to display the rotational and linear movements between the predicted and posttreatment teeth. The angular measures for rotation, torque, and tip varied more than the distance measures for buccal-lingual mesial-distal, and occlusal-gingival translations. The mean rotation differences for first premolars and second premolars were greater than two degrees.

Torque for all tooth types substantially deviated from zero, while the mean difference for second premolars and first molars was less than minus two degrees. Minor differences were observed across all attachments.