How is mobility measured in the exam procedure?

• A. Miller's classification
• B. World Health Organization mobility scale
• C. Siekman mobility index
• D. Smith's mobility system

Answer: (A)

Mobility in a periodontal exam is graded to quantify how much a tooth can move when you apply gentle forces. The standard way this is done is Miller’s classification, which provides a simple, practical scale for recording mobility during the exam.

To measure it, you apply light horizontal pressure to the crown of the tooth with a probe or the handle of a mirror and observe how much movement occurs relative to adjacent teeth. The grading goes as follows: no detectable movement is recorded as the first level, indicating stability. Slight horizontal movement up to about 1 mm is the next level. Movement of about 1–2 mm is the next grade. If the tooth can move more than 2 mm horizontally, and vertical or angular mobility is present, that is the highest grade.

This system is favored because it directly reflects the periodontal support status and is simple to reproduce across exams and clinics. Other named scales aren’t typically used for measuring tooth mobility in standard periodontal probing, so Miller’s classification remains the best choice for this purpose.