How can we diagnose Thumb Sucking ? Any child above the age of 4 with protruding anterior teeth may be affected by thumb sucking. A detailed history about the habit is very helpful. The frequency and duration of this habit can help in evaluating the extent of the habit. The thumb used by the child normally appears to be very clean compared to the other finger. Published on Apr 05, 2014Last Updated on Apr 05, 2014