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Range of Motion Scale: What Is It and Why Do You Need It?

Range of Motion ScaleA key element of the Complete Exam and Treatment Planning process is determining the health of the TM Joint. The components of the TMJ-Occlusal exam are:

  • History
  • Range of Motion Test
  • Muscle Palpation
  • Centric Relation Load Test
  • Doppler Auscultation
  • Determining signs of occlusal instability
  • Imaging, if indicated

Range of Motion Testing is accomplished by using a simple, but very effective tool, the Therabite Range of Motion Scale by Great Lakes. It is used to measure vertical opening and lateral movement of the mandible.

Measuring Vertical Opening

For measuring vertical opening, the scale is self-explanatory. The notch is placed on the lower incisor midline (or substitute) and you ask the patient to open wide. It is important to measure the amount of overbite and add/subtract to amount of opening. The normal amount of vertical opening is 40-55 mm. Also observe how the mandible tracks during opening and closing. Is there deviation or deflection? Is there pain? Are there noises?

Measuring Lateral Movements

When measuring lateral movements, you place the arrow on the scale on the upper midline pointing towards the lower incisors. Notice the relationship to the lower midline, have the patient open slightly and move laterally. The normal lateral measurement is 8-12 mm. Again, any pain or noise?

The range of motion test has important information that needs to be correlated with the other components of the TMJ-Occlusal exam. The starting point for any treatment plan is assessing the health of the joint.  If the Range of Motion is limited, what does it indicate? Is it a muscle issue or a joint issue or both?

Stay tuned for the next Blog on Limited Range of Motion.

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Picture of Dr. Stephen Miller

Dr. Steve Miller graduated from The Ohio State University College of Dentistry in 1980. Following graduation, he opened his practice in Asheville, North Carolina. He has served as President of the American Academy of Dental Practice Administration, as well as the Buncombe County Dental Society.