Human Jaw Structure and Function

"Normal" Jaw Opening -

MIO/D:  Maximum Intercisal Opening/Distance or ROM:  Range-of-Motion
Normal MIO:      Men 50-60mm Women 45-55mm
Trismus:    Decreased function of less than 30-35mm MIO.
Basic Diagnostic - The 3-Finger Test:                          
    Insert Tips of index, middle and ring fingers non-dominant hand between front teeth.

Normal MIO
>40 mm
3+ Fingers
Mild Trismus
30-40 mm  
2-3 Fingers
Moderate Trismus
15-30 mm 
1-2 Fingers
Severe Trismus
<15 mm
<1 Finger

There have been a number of studies on the average and maximum jaw openings of different populations. 

Jaw Function


Temporomandibular Joint

Dental Occlusion

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TheraBite Jaw ROM Scale Pack
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