Force System with Vertical V-Bends: A 3D In Vitro Assessment of Elastic and Rigid Rectangular Archwires

The apparatus described reduces a normal clinical set of 12 brackets to only two. Now this greatly simplifies our understanding of how an appliance works. It also provides a blueprint for testing and making modifications on similar appliances.

This experiment answers some key questions related to the variation and force system created by V-bends. When placing those bands at different locations along the incisor molar arch span. The implications of this major apparatus is tend toward creating orthodontic appliances with a more predictable force system, which, at a clinical level would imply more predictable outcomes.

To begin this procedure, insert a 0.021 by 0.025 inch SS ovoid maxillary archwire into the bracket slots. Then, place the testing apparatus in the glass chamber. Check for any unintended archwire activation.

Any activation of the archwire will automatically create a force system, which will be displayed on the computer screen. If any archwire activation is observed, reposition the brackets, and check again. To fabricate a template archwire, place an archwire in the testing apparatus.

Then, use a permanent marker to indicate the midline, a point immediately distal to the incisor bracket, and a point immediately mesial to the molar tube. Do the same for the contralateral side of the archwire. Next, transfer the archwire with the marked points to graph paper.

Make a precise replica of the archwire on it, which can be used to determine the position of the V-bend for all archwires of the sample. Then, calculate the perimeter of the archwire segment L from I to M.Now, mark 11 points from I to M.Each point is a future V-bend position. Label each point from a0 to a10.

Make sure that each bend position is separated from the other by an equal amount. Obtain a unique number for each bend position by calculating the a/L for each position. To place the V-bends, take a new archwire from the sample and place it on the template graph paper.

Then, transfer one of the 11 bend positions bilaterally to the archwire. Use a rectangular archwire plier, or a light wire plier, to make symmetrical V-bends at both sides. Place the archwire on a flat platform and check the angle made by the two ends of the archwire with a protractor.

Adjust the ends if necessary, so that an angle of 150 degrees is created. Subsequently, repeat the procedures for all archwires of the sample. To measure the force system, open the software program for data recording.

Create a new folder for the data to be saved. Then, click Run to start the software. The program will display each of the three forces and three moment values at each sensor in real time.

Wait for approximately 10 to 15 seconds for the fluctuations in data recording software to stop. Ensure that the graph lines for all the components of the force system show a flat line. Note that all six measurements at each sensor will show negligible values.

Gently remove the testing apparatus from the platform. Use a Weingart plier to insert an archwire into the molar tubes. Next, open the door of the incisor bracket with a periodontal scaler.

Lift the anterior portion of the archwire and insert it into the bracket slots. Make sure that the midline of the archwire coincides with the midline of the testing apparatus. After placing the archwire in the bracket slots, if the archwire has to be taken off for some adjustments, then the same archwire cannot be used and a new archwire will have to be inserted.

Afterward, return the testing apparatus to the platform and close the door of the glass chamber. Set the temperature at thirty-seven degrees Celsius, and wait one minute for the temperature of the glass chamber to adjust. Click the Start Saving button on the software and allow the software to save and transfer data for at least 10 seconds.

Click the Start Saving button again to end data transfer, then click STOP. Note that each measurement cycle generates 100 readings over the 10-second period for each component. Repeat the procedures for the 10 archwires of that specific bend position, and for all bend positions and types of archwires.

To evaluate the error, open the software program for data recording. Create a new folder for the data to be saved. Then, click Run to start the software.

The program will display each of the three forces, and three moment values at each sensor, in real time. Wait for approximately 10-15 seconds for the fluctuations in data recording software to stop. Ensure that the graph lines on the software for all the components of the force system show a flat line.

Remove the testing apparatus from the platform. Using a light wire plier, bend one end of a straight length of a 0.021 x 0.025 in SS wire into a small hook. Insert the free end of the archwire into the molar tube from the distal side.

Next, place the testing apparatus back on the platform. Attach a known weight to the hook and let it hang freely in the vertical plane by removing any type of interference. Close the door of the glass chamber.

Click the Start Saving button on the software and allow the software to save and transfer data for at least 10 seconds. Click the Start Saving button again to end data transfer, then click STOP. Go to the document containing the saved data, export the data set to a custom designed data analysis spreadsheet, and repeat the error evaluation procedures for the incisor bracket.

The vertical forces show symmetric and linear pattern for each of the six wire types. As the V-bend gets closer to either bracket, the vertical forces get higher. As the bend is moved farther beyond this point, the vertical force progressively increases.

However, the directions of the individual vertical forces are reversed. Stainless steel archwires create a significantly greater force system than beta titanium archwires. Surprisingly, the relative force system created at the two brackets by the archwires, both in terms of size and type of archwire, is quite similar.

In contrast, the moments show a nonlinear and asymmetric pattern. The flattening of Mxi, when V-bends are placed close to the molar tube, as well as the reversal of the moment direction in the molar tube from ax/L of 0.0 to 0.2 was similar for all archwires, and perhaps, represents a more fundamental nature of archwire bracket interaction and bracket orientation. The ratio of the moment of the two brackets shows some specific patterns observed across all archwires tested, and can be grouped into three distinct patterns.

This approach can be utilized in numerous other clinical scenarios besides just V-bends. We have already begun testing some of those, and in the near future, we are looking at integrating this data directly with FEM simulations for similar setups. This approach will help in understanding and predicting clinical outcomes in patients.

This will be a huge step in customizing treatment according to patient needs.