Thumb sucking

Last updated
Infants may use pacifier or thumb or fingers to soothe themselves BabySuckingFingers.jpg
Infants may use pacifier or thumb or fingers to soothe themselves
Newborn baby thumb sucking
A bonnet macaque thumb sucking Bonnet Macaque Western Ghats.jpg
A bonnet macaque thumb sucking

Thumb sucking is a behavior found in humans, chimpanzees, captive ring-tailed lemurs, [1] and other primates. [2] It usually involves placing the thumb into the mouth and rhythmically repeating sucking contact for a prolonged duration. It can also be accomplished with any organ within reach (such as other fingers and toes) and is considered to be soothing and therapeutic for the person. As a child develops the habit, it will usually develop a "favorite" finger to suck on.


At birth, a baby will reflexively suck any object placed in its mouth; this is the sucking reflex responsible for breastfeeding. From the very first time they engage in nutritive feeding, infants learn that the habit can not only provide valuable nourishment, but also a great deal of pleasure, comfort, and warmth. Whether from a mother, bottle, or pacifier, this behavior, over time, begins to become associated with a very strong, self-soothing, and pleasurable oral sensation. As the child grows older, and is eventually weaned off the nutritional sucking, they can either develop alternative means for receiving those same feelings of physical and emotional fulfillment, or they can continue experiencing those pleasantly soothing experiences by beginning to suck their thumbs or fingers. [3] This reflex disappears at about 4 months of age; thumb sucking is not purely an instinctive behavior and therefore can last much longer. [4] Moreover, ultrasound scans have revealed that thumb sucking can start before birth, as early as 15 weeks from conception; whether this behavior is voluntary or due to random movements of the fetus in the womb is not conclusively known.

Thumb sucking generally stops by the age of 4 years. Some older children will retain the habit, which can cause severe dental problems. [5] While most dentists would recommend breaking the habit as early as possible, it has been shown that as long as the habit is broken before the onset of permanent teeth, at around 5 years old, the damage is reversible. [6] Thumb sucking is sometimes retained into adulthood and may be due to simply habit continuation. Using anatomical and neurophysiological data a study has found that sucking the thumb is said to stimulate receptors within the brain which cause the release of tension, mentally and physically which shows a scientific standpoint regarding the psychological basis of thumb sucking. [7]

Dental problems and prevention

Alveolar prognathism, caused by thumb sucking and tongue thrusting in a 7-year-old girl. Alveolprog.jpg
Alveolar prognathism, caused by thumb sucking and tongue thrusting in a 7-year-old girl.

Percentage of children who suck their thumbs (data from two researchers)

AgeKantorowicz [4] Brückl [8]


Over 69%

Most children stop sucking on thumbs, pacifiers or other objects on their own between 2 and 4 years of age. No harm is done to their teeth or jaws until permanent teeth start to erupt. The only time it might cause concern is if it goes on beyond 6 to 8 years of age. At this time, it may affect the shape of the oral cavity or dentition. [9] During thumbsucking the tongue sits in a lowered position and so no longer balances the forces from the buccal group of musculature. This results in narrowing of the upper arch and a posterior crossbite. Thumbsucking can also cause the maxillary central incisors to tip labially and the mandibular incisors to tip lingually, resulting in an increased overjet and anterior open bite malocclusion, as the thumb rests on them during the course of sucking. In addition to proclination of the maxillary incisors, mandibular incisors retrusion will also happen. Transverse maxillary deficiency gives rise to posterior crossbite, ultimately leading to a Class II malocclusion. [10]

Children may experience difficulty in swallowing and speech patterns due to the adverse changes. Aside from the damaging physical aspects of thumb sucking, there are also additional risks, which unfortunately, are present at all ages. These include increased risk of infection from communicable diseases, due to the simple fact that non-sterile thumbs are covered with infectious agents, as well as many social implications. Some children experience social difficulties, as often children are taunted by their peers for engaging in what they can consider to be an “immature” habit. This taunting often results the child being rejected by the group or being subjected to ridicule by their peers, which can cause understandable psychological stress. [11]

Methods to stop sucking habits are divided into 2 categories: Preventive Therapy and Appliance Therapy. [10]

Examples to prevent their children from sucking their thumbs include the use of bitterants or piquant substances on their child's hands—although this is not a procedure encouraged by the American Dental Association [9] or the Association of Pediatric Dentists. Some suggests positive reinforcements or calendar rewards to be given to encourage the child to stop sucking their thumb.

The American Dental Association recommends:

The British Orthodontic Society recommends the same advice as ADA. [13]

A Cochrane review was conducted to review the effectiveness of a variety of clinical interventions for stopping thumb-sucking. The study showed that orthodontic appliances and psychological interventions (positive and negative reinforcement) were successful at preventing thumb sucking in both the short and long term, compared to no treatment. [14]

Clinical studies have shown that appliances such as TGuards can be 90% effective in breaking the thumb or finger sucking habit. Rather than use bitterants or piquants, which are not endorsed by the ADA due to their causing of discomfort or pain, TGuards break the habit simply by removing the suction responsible for generating the feelings of comfort and nurture. [15] Other appliances are available, such as fabric thumb guards, each having their own benefits and features depending on the child's age, willpower and motivation. Fixed intraoral appliances have been known to create problems during eating as children when removing their appliances may have a risk of breaking them. Children with mental illness may have reduced compliance. [10]

Some studies mention the use of extra-oral habit reminder appliance to treat thumb sucking. An alarm is triggered when the child tries to suck the thumb to stop the child from this habit. [10] [16] However, more studies are required to prove the effectiveness of external devices on thumb sucking.

See also

Related Research Articles

Orthodontics field of dentistry dealing with irregularities in the teeth

Orthodontics is a specialty of dentistry that deals with the diagnosis, prevention and correction of malpositioned teeth and jaws. It can also focus on modifying facial growth, known as dentofacial orthopedics.

Hyperdontia An extra tooth, erupted or unerupted, resembling or unlike the other teeth in the group to which it belongs. Its presence may cause malposition of adjacent teeth or prevent their eruption.

Hyperdontia is the condition of having supernumerary teeth, or teeth that appear in addition to the regular number of teeth. They can appear in any area of the dental arch and can affect any dental organ. The opposite of hyperdontia is hypodontia, where there is a congenital lack of teeth, which is a condition seen more commonly than hyperdontia. The scientific definition of hyperdontia is "any tooth or odontogenic structure that is formed from tooth germ in excess of usual number for any given region of the dental arch." The additional teeth, which may be few or many, can occur on any place in the dental arch. Their arrangement may be symmetrical or non-symmetrical.

Pacifier rubber, plastic or silicone nipple for infants to suck upon

A pacifier or dummy, also known as a binky, soother, teether or Dodie is a rubber, plastic or silicone nipple given to an infant to suck upon. In its standard appearance it has a teat, mouth shield, and handle. The mouth shield and/or the handle is large enough to avoid the danger of the child choking on it or swallowing it.

Mouthguard protective device for the mouth

A mouthguard is a protective device for the mouth that covers the teeth and gums to prevent and reduce injury to the teeth, arches, lips and gums. A mouthguard is most often used to prevent injury in contact sports, as a treatment for bruxism or TMD, or as part of certain dental procedures, such as tooth bleaching or sleep apnea. Depending on application, it may also be called a mouth protector, mouth piece, gumshield, gumguard, nightguard, occlusal splint, bite splint, or bite plane. According to a study by Dr. Tonkly you are 22% less likely to be concussed if you are wearing a mouth guard.

Prognathism Protrusion of the upper or lower human jaw

Prognathism is a positional relationship of the mandible or maxilla to the skeletal base where either of the jaws protrudes beyond a predetermined imaginary line in the coronal plane of the skull. In general dentistry, oral and maxillofacial surgery, and orthodontics, this is assessed clinically or radiographically (cephalometrics). The word prognathism derives from Greek πρό and γνάθος. One or more types of prognathism can result in the common condition of malocclusion, in which an individual's top teeth and lower teeth do not align properly.

Malocclusion misalignment or incorrect relation between the teeth of the two dental arches when they approach each other as the jaws close

A malocclusion is a misalignment or incorrect relation between the teeth of the two dental arches when they approach each other as the jaws close. The term was coined by Edward Angle, the "father of modern orthodontics", as a derivative of occlusion. This refers to the manner in which opposing teeth meet.

Tongue thrust is the common name of an oral myofunctional disorder, a dysfunctional muscle pattern in which the tongue protrudes anteriorly or laterally during swallowing, during speech, and while the tongue is at rest. Nearly all infants exhibit a swallowing pattern involving tongue protrusion, but by six months of age most lose this reflex allowing for the ingestion of solid foods.

Palatal expansion Orthodontics

A palatal expander is a device in the field of orthodontics which is used to widen the upper jaw (maxilla) so that the bottom and upper teeth will fit together better. This is a common orthodontic procedure. Although the use of an expander is most common in children and adolescents 8-18 years of age, it can also be used in adults, although expansion is slightly more uncomfortable and takes longer. A patient who would rather not wait several months for the end result by a palatal expander may be able to opt for a surgical separation of the maxilla. Use of a palatal expander is most often followed by braces to then straighten the teeth.

Mouth breathing is breathing through the mouth rather than the nose. Human infants are sometimes considered obligate nasal breathers, but generally speaking healthy humans may breathe through their nose, their mouth, or both.

Maxillary central incisor tooth

The maxillary central incisor is a human tooth in the front upper jaw, or maxilla, and is usually the most visible of all teeth in the mouth. It is located mesial to the maxillary lateral incisor. As with all incisors, their function is for shearing or cutting food during mastication (chewing). There is typically a single cusp on each tooth, called an incisal ridge or incisal edge. Formation of these teeth begins at 14 weeks in utero for the deciduous (baby) set and 3–4 months of age for the permanent set.

Orthodontic technology is a specialty of dental technology that is concerned with the design and fabrication of dental appliances for the treatment of malocclusions, which may be a result of tooth irregularity, disproportionate jaw relationships, or both.

Occlusion, in a dental context, means simply the contact between teeth. More technically, it is the relationship between the maxillary (upper) and mandibular (lower) teeth when they approach each other, as occurs during chewing or at rest.


Overjet is the extent of horizontal (anterior-posterior) overlap of the maxillary central incisors over the mandibular central incisors. In class II malocclusion the overjet is increased as the maxillary central incisors are protruded.


Crossbite is a form of malocclusion where a tooth has a more buccal or lingual position than its corresponding antagonist tooth in the upper or lower dental arch. In other words, crossbite is a lateral misalignment of the dental arches.

Orofacial myofunctional disorders (OMD) are muscle disorders of the face, mouth, lips, or jaw.

The Dahl effect or Dahl concept is used in dentistry where a localized appliance or localized restoration is used to increase the available interocclusal space available for restorations.

Serial extraction is the planned extraction of certain deciduous teeth and specific permanent teeth in an orderly sequence and predetermined pattern to guide the erupting permanent teeth into a more favorable position.

Human mouth mouth of a human being

In human anatomy, the mouth is the first portion of the alimentary canal that receives food and produces saliva. The oral mucosa is the mucous membrane epithelium lining the inside of the mouth.

TGuard is the brand name for a medical device used to stop chronic thumb sucking among children and young adults. It is manufactured in the USA by MED et al., Inc. Referred to commonly by dentists as a ThumbGuard, the company claims that it is the most effective removable appliance therapy used to stop and prevent thumb sucking.

Open bite is a type of orthodontic malocclusion which has been estimated to occur in 0.6% of the people in the United States. This type of malocclusion has no vertical overlap or contact between the anterior incisors. The prevalence varies between different populations, for instance, occurring with 16% in black people and 4% in white people. The term "open bite" was coined by Carevelli in 1842.


  1. Jolly, A. (1966). Lemur Behavior . Chicago: University of Chicago Press. p.  65. ISBN   978-0-226-40552-0.
  2. Benjamin, Lorna S.: "The Beginning of Thumbsucking." Child Development, Vol. 38, No. 4 (Dec., 1967), pp. 1065–1078.
  3. "About the Thumb Sucking Habit".
  4. 1 2 A. Kantorowicz: "Die Bedeutung des Lutschens für die Entstehung erworbener Fehlbildungen." In: Fortschritte der Kieferorthopädie. Bd. 16, Nr. 2, 1955, S. 109–121.
  5. O'Connor, Anahad (27 September 2005). "The Claim: Thumb Sucking Can Lead to Buck Teeth". The New York Times. Retrieved 1 August 2012.
  6. “Influence of thumb sucking on peer social acceptance in first-grade children” In: Pediatrics. April, 1994
  7. “Finger or thumb sucking. New interpretations and therapeutic implications” In: Pediatrics. August, 2015
  8. Erwin Reichenbach, Hans Brückl: Kieferorthopädische Klinik und Therapie. J. A. Barth, Leipzig 1962
  9. 1 2 "Thumbsucking - American Dental Association". Archived from the original on 2010-06-19. Retrieved 2010-05-19.
  10. 1 2 3 4 Shetty, Raghavendra M; Shetty, Manoj; Shetty, N Shridhar; Deoghare, Anushka (2015). "Three-Alarm System: Revisited to treat Thumb-sucking Habit". International Journal of Clinical Pediatric Dentistry. 8 (1): 82–86. doi:10.5005/jp-journals-10005-1289. ISSN   0974-7052. PMC   4472878 . PMID   26124588.
  11. "Damage to the primary dentition resulting from thumb and finger (digit) sucking” In: Journal of Dentistry for Children. Nov-Dec 1996
  12. "Stop Thumb Sucking".
  14. Borrie, Felicity RP; Bearn, David R.; Innes, Nicola PT; Iheozor-Ejiofor, Zipporah (2015). "Interventions for the cessation of non-nutritive sucking habits in children". Cochrane Database of Systematic Reviews (3): CD008694. doi:10.1002/14651858.CD008694.pub2. PMID   25825863.
  15. "Unique Thumb with Lock Band to Deter Child from ThumbSucking” In: Clinical Research Associates Newsletter.Volume 19, Issue 6, June 1995
  16. Krishnappa S, Rani M S, Aariz S. New electronic habit reminder for the management of thumb-sucking habit. J Indian Soc Pedod Prev Dent 2016;34:294-7