Thumbs sucking or the use of pacifier is one of the most common kinds of oral habits. If this habit is carried on beyond age four, it can lead to an open bite, crooked permanent teeth and problems with the normal jaw development. Therefore, it would be the most ideal to wean off thumb sucking by age four or five. Thumb sucking tends to be harder to wean off in girls. The effect of thumb sucking is worse than the use of a pacifier.