P13061 Periodontal Measurement Test System

1. P13061 Periodontal Measurement Test System • Mission/Problem Statement: • To design, develop and build an automated fixture that will repeatedly and accurately measure the sulcus depth. The sulcus is the gap found between the teeth and the gums. A healthy sulcus is approximately 1-3 mm deep. When periodontal disease is present, the depth of the sulcus becomes abnormally deep and increases as the disease progresses. The current method for measuring the sulcus depth utilizes a metal probe which is both tedious and painful as well as inconsistent and unreliable. • Objective/Scope: • Create a test fixture that holds and positions an ultrasonic transducer (probe) accurately and repeatedly • Create a non-biodegradable tooth phantom • Accurately and repeatedly measure the sulcus depth of the tooth phantom and store measurements for post-test analysis • Team Members: • Raymond Boronczyk (ME), Evan Lammertse (ME), Samuel Remp (EE), Yokai Ro (EE), Ryan Shaw (ME), Kristi Weaver (ME) • Faculty Guide & Customer: Neal Eckhaus (secondary customer: Dr. Rosenblum) • Test Fixture Requirements • Test probe must be able to move through five axes • Fixture must be compact and portable • Fixture must allow for maintenance to be performed by untrained personnel • Fixture must allow for position changes to a programmatically specified point to within 0.1 mm for linear movement or 1 degree for angular movement • Fixture must allow for the tooth phantom to be replaced by a biological mandible Figure 1: Team P13061 • Tooth Phantom Requirements • Tooth phantom must be made of non-biological materials that mimic human tissue with respect to ultrasonic properties • Ability to vary sulcus depth with a resolution of 0.1 mm • Tooth phantom must be quickly replaced within the holding fixture • Tooth phantom geometry must allow for quick alterations of the physical relationship between the tooth and the gums • Tooth phantom materials must allow for ultrasonic distinction between materials • Ultrasonic Probe GUI Requirements • Motor Control • Motors must facilitate accurate and repeatable movement of the ultrasonic probe via programmatic controls • Motors must allow for position changes to a programmatically specified point to within 0.1 mm for linear movement or 1 degree for angular movement • Data Acquisition • Program must be able to remotely acquire and interpret data from the ultrasonic probe via oscilloscope outputs • Limit Comparison • Program must be able to log data for post-test analysis • Program must be able to compare data to a standard Figure 2: test fixture System Overview The fixture consists of two major subsystems, the probe holder and the tooth phantom holder. The probe holder allows for movement through the vertical, lateral and pitch axes, while the tooth phantom portion encompasses the yaw and longitudinal axes. Lead screws driven by stepper motors are used for the three linear axes while simple servos and shafts are used for the two angular axes. Four tooth phantoms are fastened to the turn table. The use of multiple tooth phantoms allows for different sulcus depths to be represented without requiring assembly or disassembly of the fixture or alteration of the phantom. The tooth phantoms are fashioned out of a square aluminum tube simulating the bone and concrete was poured into the tubing to represent the dentin. Fabric paint and rubber are attached to the aluminum tube to represent the gum tissue. Per customer needs the system is controlled by Labview programming language in conjunction with an Arduino Uno development board. Through the Arduino, Labview articulates the servo motors and also sends commands to EasyDriver boards to control the stepper motors. Three slide potentiometers are incorporated to provide positional feedback. The GUI (graphic user interface) encompasses an intuitive design to allow for simple operation. Test results are conveniently stored in a file for post-test analysis. Figure 3: oscilloscope output • Results & Future Work • Throughout initial work on the project the team quickly discovered that not all customer needs were attainable. Multiple discussions with the customer and faculty guide led to a redefinition of project scope. The team was able to move the probe in all five axes and detect the interface between differing materials. The output provided by the oscilloscope is shown in Figure 3 above. Each spike represents the voltage seen when passing through a particular material. Each time the ultrasonic signal passes through a new material a spike of varying amplitude is produced. • Most importantly, future work will require an ultrasonic probe with higher capability. The probe used for this testing was not a high enough frequency to detect the minute differences present in the human tissues in and around the sulcus. Throughout the early stages of the project the team discovered a lack of research regarding the behavior of ultrasound within the human mouth. To select materials that closely resemble human tissue, research and testing should be conducted to understand the behavior of ultrasound within human tissue. The team believes the behavior of ultrasound to be based on acoustic impedance, speed of sound and density; however, other properties might be deemed relevant based upon further research and experimentation. The material properties of tissue determined through testing could be compared to those of various materials to conclude which materials are the most representative of human tissue. The team also encountered issues with manipulating some materials, so ease of manipulation is an important consideration during the material selection process. The mechanical interfaces between the servo motors and the turn table and probe holder are prone to angular torque which can cause current spikes and subsequently damage to the servo motors. A redesign of the fixture could improve this interface and reduce the torque on the servo motors, minimizing the possibility of damage to the motors. The stepper motor drivers are rated to 30V but the minimum of 12V was used to power the stepper motors. However, if the voltage was increased the steps could be strengthened to prevent skipping due to friction. Therefore, the fixture design should be optimized to reduce friction and the power supply selection should be reconsidered. • Legend • Team successful • Requires future work Acknowledgements Dr. Caton (U of R), Neal Eckhaus, Dr. Helguera (RIT), Dr. Hopkins (RIT), Professor Landschoot (RIT), Dr. Stephen McAleavey (U of R), Dr. Phillips (RIT), Dr. Rosenblum (Customer), RIT Machine Shop