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Human Jaw Motion Simulator - TMJ Disorder Analysis & Treatment

A research project aiming to develop a physical model of the human skull and simulate jaw motions for analyzing and treating TMJ disorders. The project includes stages for jaw closing, jaw opening, jaw clenching and disc adaptation, and lateral jaw motion/chewing.

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Human Jaw Motion Simulator - TMJ Disorder Analysis & Treatment

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  1. Human Jaw Motion SimulatorDepartment of Mechanical & Industrial EngineeringNortheastern UniversityBoston, MA 02115April 17, 2007 By: B. Galer N. Hockenberry J. Maloof M. Monte-Lowrey K. O’Donnell Advisor and Sponsor: Prof. Sinan Muftu

  2. Outline Motivation and Goals Project Stages Important Skull Components Muscles System Analysis and Control Development Design Details Results and Conclusions

  3. Motivation Motivation Over 10 million Americans are affected by TMJ disorders 2 times as many woman as men suffer from TMJ disorders Symptoms range from jaw click to limited movement, lock jaw, and pain Purpose Provide resource for analyzing the TMJ to allow for treatment of TMJ disorders To test prosthetics

  4. Overall Project Goals • Create physical model of a skull • Simulate jaw motions • LabVIEW interface • Virtual Matlab analysis

  5. Stage Goals Stage I Initial Setup and Jaw Closing Stage II Jaw Opening (including opening to closing transition) Stage III Jaw Clenching and Disc Adaptation (disc must be capable of multiple forms of motion) Stage IV Lateral Jaw Motion/ Chewing (realistic disc simulation must be accomplished by this stage).

  6. Background

  7. Important Components of the Skull Maxilla Mandible Muscles Ligaments Temporomandibular Joint Articular disc

  8. Muscles of Closing and Max Forces Temporal 120 lbs • Lateral pterygoid • 34 lbs • Masseter • 93 lbs

  9. Muscle Assumptions and Constraints Muscles Can only contract Are symmetrical for either side of jaw Act in a single plane Will be simulated as acting as a single vector through the center of the muscle.

  10. Muscle attachments Koolstra Study 1992 Attachment points: On Jaw Anchor points: On Skull Zero point based on contact point

  11. System Analysis and Control Development

  12. Motion of the Human Jaw • What motions are involved in closing the jaw? • What assumptions must be made? • How can the motion be controlled?

  13. Assumptions • Compressive Force on disc is constant • Disc moves with mandible • Mandible Contact Point • Taken while in fully closed position • Always perpendicular to articulating surface • Results of Assumptions • The Disc will be Left out of Model • The Normal Force from the Articulating Surface Acts Directly on Contact Point

  14. Physical Constraints of Mandible • Constrained to single path of travel • Mapped profile of the articulating surface • Orientation of lower jaw found at predefined target positions

  15. System Control Force Statically Indeterminate Controllable with Tension or Slack Method Definitive Research not Available Control System Requires More Research Physiologically Accurate Position Anatomically Constrained Controllable with Length Adjustments Information is Readily Available Control System is Common and Simple Not Physiologically Accurate

  16. Positional Control Anchor Points • Motion Tracking • Constrained Orientations • Varying Muscle lengths • Matlab Program • Variable surface profiles • Variable tracking locations • Creates positional output • Control Method • Control Muscle Lengths Articulating Surface Attachments and Predicted Paths Mandible

  17. Design Details

  18. The Design

  19. Frame

  20. Muscle Decision Matrix

  21. Brushless Servo Motors • High precision and accuracy • Position control requires feedback • AKM33E- Danaher Motion • 2.2NM torque • Built in encoder

  22. Controlling the Motors • NI PCI-7344 four axis servo/step motion controller • MDM-2100 integrated three axis servo drive with power supply

  23. LabVIEW Interface • Can be run by any user • Allow easy future changes to project • Feedback loop built into program

  24. Pulley System • Pulleys used to increase torque • Keeps motor cost low • Allows for project expansion

  25. Wire Attachments and Guides • Can only pull like muscles • Adjustable tension

  26. Skull and Lubrication Mimics Program Convert CT scan to 3-D model SLA model to rubber-molded model Attachment points tested for bending Lubrication on joint

  27. Results and Conclusion

  28. Virtual Analysis

  29. Physical Analysis

  30. Results • Virtual • Jaw Appeared to Open Improperly • Negative Force Values • Physical • Separation at joint

  31. Conclusions Initial Assumptions Were Incorrect • Mandible Does Not Stay Perpendicular to the Articulating Surface • Muscles Can Only Contract, Whereas Results Suggested Expansion • Muscle Choices May be Incorrect or Over Simplified

  32. Updated Assumptions

  33. Running the System

  34. Special Thanks To • Prof. Sinan Muftu • Prof. Greg Kowalski • Prof. Rifat Sipahi • Jeff Doughty • Jon Doughty • US Surgical • Brian Weinberg & Prof. Constantinos Mavroidis’ lab

  35. Questions?

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