The focus of our project was to solve a key challenge in restorative dentistry: achieving precise alignment of dental restorations like crowns, veneers, and dentures. Accurate determination of the midline and horizontal planes of the face is essential in fitting such dental prosthetics. It ensures a natural and symmetrical appearance by aligning restorations with the patient’s facial structure, contributing to aesthetic harmony. Functionally, it helps maintain a proper bite, preventing issues like discomfort, uneven wear, or difficulty chewing and speaking. Additionally, precise alignment is crucial for the longevity and success of dental restorations, reducing the risk of premature failure or complications (it takes, on average, three attempts before a successful denture fit is achieved). Our design aimed to provide a reliable solution to this problem: giving dentists precise, digital measurements of the midline and horizontal facial planes, helping them achieve better outcomes for both the aesthetics and functionality of their patient’s smiles.

Most of the current solutions for determining midline and horizontal alignment in dental procedures are archaic, cage-like devices. While these methods can be effective, they often come with limitations in precision, ease of use, or adaptability. Here's a summary of some of the current solutions on the market:

• HodentalCompany Harmony Anterior Dual Arch Tray: This disposable tray simplifies the dental impression process by capturing prepared teeth, the opposing arch, bite registration, and the facial midline. It uses an inter-occlusal mesh to enhance accuracy but remains an analog solution.

• OneBite: This adaptable tool works with any articulator to verify midline and horizontal angles. Using a facebow, it mounts the maxillary arch and allows for post-bite adjustments. It accommodates both symmetrical and asymmetrical faces with features like locked bars or independently moving bars for precise alignment.

• OneBite Evolution: This tool streamlines the maxillary arch transfer process, replacing traditional facebow workflows in both analog and digital methods.

• HodentalCompany Facial Plane Relator Bite Registration Tool: Designed to capture and communicate the patient’s midlines accurately, this tool guides lab technicians in setting the angles for teeth and the occlusal plane. It features a horizontal bar with 25 stabilizing fingers and a snap-on vertical bar, simplifying alignment and reducing guesswork for technicians.

While these tools address some aspects of alignment, they often rely on manual techniques, require complex workflows, or leave room for human error, highlighting the need for a more integrated and precise solution.

To enhance existing solutions on the market, our device takes a novel approach to determining facial horizontal and midline planes. Instead of relying on a structural device placed in front of the face, it uses lasers to project lines directly onto the face. These lines can be adjusted by the dentist to align with the patient’s facial planes. Additionally, the device captures precise angle measurements, providing the dentist with accurate information to guide the fitting of dental prosthetics. 

As the project progressed and we received more feedback from our sponsor, both our customer and engineering specifications evolved. Initially, the goal of the project was to provide a novel means of displaying (but not providing angle measurements for) the facial planes via laser lines. Therefore, the following requirements and specifications shaped our initial, but not final, designs:

This concept contains two, independent laser lines, one for horizontal- and one for vertical-plane projection. Additionally, it contains a remote-controlled laser adjustment system to adjust both the tilt and rotation of both lasers. It features a button and slider mechanism with notches to adjust the distance of the laser projection from the mouthpiece and a flexible device stabilizer headpiece that attaches to the patient’s temple area. A more detailed concept of the mechanism by which the lasers would articulate can be seen below:

A final concept model was created in Solidworks, showcasing how the two lasers, and their articulating motors, would fit on a frame. Ultimately, our sponsor changed the scope of the device, meaning our customer requirements and design changed.

After showing our sponsor the final design concept seen above, he decided to change the scope of the device. Our customer requirements shifted and the next design iteration would not need independent, articulating lasers. Rather, the device would focus on aligning a laser crosshair (facial planes would be orthogonal), with the planes of the face and reading the corresponding pitch (horizontal plane angle) and roll (vertical plane angle) measurements. These measurements would be relative to the mouth, not the ground, ensuring accuracy regardless of the position of the patient's body and face.

The workflow for this concept is as follows: The dentist places the device in the patient’s mouth and adjusts the laser crosshairs (shown in the black box above) to align with the facial planes. A ball-and-socket joint enables adjustments in tilt, roll, and yaw, ensuring precise alignment. Parallel linkages allow the dentist to confirm the horizontal plane by swinging the laser to the side and referencing anatomical landmarks, such as the ears—an essential feature requested by our sponsor. Lastly, sensors on the device capture and provide accurate angle measurements. 

After performing a number of design iterations, modifying the above concept model to include actual dimensions of our electrical components, while simultaneously designing and testing the electrical assembly (sensors, Arduino, and laser crosshairs), a final 3D model was developed:

This design fulfills all required elements by our sponsor, including some additional features:

• Female Ball joint (yellow component):

  • Houses an accelerometer sensor, which is used to calculate the angles of the mouth.

  • Contains a threaded insert, where a hand-threaded set screw can lock the ball-and-socket. 

• Parallel Linkages (green components):

  • Contains a slot for a magnet to be press-fit. A corresponding magnet on the laser base allows for the device to remain in the "straight" configuration when a dentist is not checking the horizontal plane against the ears.

• Laser base (red component):

  • Houses a second accelerometer internally. This calculates the pitch and roll angles, subtracting them against the first sensor to get measurements relative to the mouth.

  • Houses the laser crosshairs.

The "housing box" contains the electrical control center for the device. Housed within the box is the Arduino microcontroller and a breadboard containing all wiring. Additionally, an OLED display on the lid of the box displays the pitch and roll measurements. Lastly, a power switch turns the device on and off.

All components of the final design were either sourced or manufactured via FDM and SLS 3D printing. All electrical components were soldered to ensure a reliable connection. 

We successfully developed a working prototype that met or exceeded our sponsor's requirements. However, with wires sticking out and components printed in different colored filaments, this device was most definitely a proof-of-concept prototype. Had our project lasted longer, I would have liked to develop a second, "market-ready" prototype. Here are some things I would incorporate in such a device:

• Manufacture all mechanical components using a durable thermoset plastic rather than the current 3D printed PLA.

• Develop custom printed circuit boards (PCBs). This would drastically reduce the amount of space needed to house sensors. 

• Power all components via a rechargeable battery and add a wireless, Bluetooth functionality. This, in conjunction with the previous bullet, would eliminate the need for external wiring.

•  Integrate the laser into the device.

• Develop an app or web interface, where the angle measurements from the device can be displayed, eliminating the current OLED display, which is small and difficult to read. This would also eliminate the need for an external electrical housing box.

As the lead technical engineer for my group, I was responsible for designing 95% of the device, including both mechanical and electrical components. This project was a major milestone for me, as it was the first time I independently built a device that integrated mechanical and electrical systems—an accomplishment I’m incredibly proud of. I gained a wealth of knowledge during this process, especially in coding microcontrollers. Before this project, I had little experience with microcontrollers, but now I can confidently program an Arduino to power and control a wide range of devices. While the project was both challenging and stressful at times, it was an amazing learning experience. I’m deeply grateful for my teammates, Iris Zhang and Sydney Sherman, who handled most of the report writing and documentation, which allowed me to focus on what I love most: design.