The habit of inserting a thumb or fingers into the mouth between the maxillary and mandibular teeth, most commonly practised by babies and infants. It may result in a localized malocclusion of either the primary or permanent dentition, usually resulting in an anterior open bite, and in severe cases changes to the roof of the mouth. The malocclusion can also lead to a speech impediment. The habit is associated with comfort and relaxation and may be adopted to induce sleep. Digit sucking usually ceases naturally without external intervention prior to the eruption of the permanent dentition (between the ages of 2 and 4), but it can persist into adult life.
Warren J. J., Slayton R. L., Bishara S. E., Levy S. M., Yonezu T., Kanellis M. J. Effects of non-nutritive sucking habits on occlusal characteristics in the mixed dentition. Pediatr Dent 2005;27(6):445–50.