What is the normal range for maximal mouth opening in TMJ examination?

• A. 20-30 mm
• B. 35-55 mm
• C. 60-70 mm
• D. 10-15 mm

Answer: (B)

Maximal mouth opening is the interincisal distance measured when the mouth is opened as wide as possible. In healthy adults this distance typically falls in the vicinity of about 35 to 55 millimeters, reflecting natural variation in jaw size, dentition, and soft tissue flexibility. Measuring this helps identify restrictors of movement, such as trismus or TMJ disc and muscle problems; values well below 35 mm suggest limited opening, while values above 55 mm may indicate hypermobility or measurement variability. When you measure, place the ruler between the incisal edges of the upper and lower front teeth and record the maximum distance reached.