Which statement best describes the normal mouth opening?

• A. It is greater than 40 mm, typically 2-3 fingers
• B. It is 60-70 mm
• C. It is 15-20 mm
• D. It is 25-30 mm

Answer: (A)

Normal mouth opening is the maximal distance the jaw can open, measured between the upper and lower front teeth. In healthy adults this distance is about 40–50 mm, which is conveniently estimated as two to three finger widths. So the statement describing opening greater than 40 mm matches this typical, functional range. Opening around 60–70 mm would be larger than usual and not considered the standard normal, while openings of 15–20 mm or 25–30 mm indicate restricted movement and potential dysfunction. Therefore, the best description of normal mouth opening is a distance greater than 40 mm, about two to three finger widths.