Thumb sucking

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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 mental and physical tension. [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 suggest that positive reinforcements or calendar rewards 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] Psychological interventions such as habit reversal training and decoupling have also proven useful in body focused repetitive behaviors. [15]

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. [16] 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] [17] However, more studies are required to prove the effectiveness of external devices on thumb sucking.

See also

Related Research Articles


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


A pacifier is a rubber, plastic, or silicone nipple substitute given to an infant to suckle upon between feedings to quiet its distress by satisfying the need to suck when it does not need to eat. Pacifiers normally have three parts, an elongated teat, a mouth shield, and a handle. The mouth shield is large enough to prevent the child from attempting to take the pacifier into its mouth, and so forecloses the danger that the child will swallow then choke on it.

Hypodontia Developmental absence of one or more teeth excluding the third molars

Hypodontia is defined as the developmental absence of one or more teeth excluding the third molars. It is one of the most common dental anomalies and has a negative impact on both looks and function. It rarely occurs in primary teeth and the most commonly affected are the adult second premolars and the upper lateral incisors. It usually occurs as part of a syndrome that involves other abnormalities and requires multidisciplinary treatment.

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.


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

Tongue thrust is a pseudo-pathological name of what is either considered a normal adaptive lip seal mechanism, whereby normal nasal breathing or normal swallowing can occur. Or, it is seen as an oral myofunctional disorder - a tongue muscle pattern that is perceived as clinically abnormal and in which the tongue protrudes anteriorly to seal otherwise incompetent lips.

Palatal expansion

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.

Maxillary central incisor

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.

Dilaceration is a developmental disturbance in shape of teeth. It refers to an angulation, or a sharp bend or curve, in the root or crown of a formed tooth. This disturbance is more likely to affect the maxillary incisors and occurs in permanent dentition. Although this may seem more of an aesthetics issue, an impacted maxillary incisor will cause issues related to occlusion, phonetics, mastication, and psychology on young patients.

Tooth gemination is a dental phenomenon that appears to be two teeth developed from one. There is one main crown with a cleft in it that, within the incisal third of the crown, looks like two teeth, though it is not two teeth. The number of the teeth in the arch will be normal.

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.

Dental pertains to the teeth, including dentistry. Topics related to the dentistry, the human mouth and teeth include:

Pediatric dentistry

Pediatric dentistry is the branch of dentistry dealing with children from birth through adolescence. The specialty of pediatric dentistry is recognized by the American Dental Association, Royal College of Dentists of Canada, and Royal Australasian College of Dental Surgeons.

Pre-eruption guidance is an orthodontic treatment method that allows for expansion of existing erupting teeth long before they appear in the mouth. The use off pre-eruption guidance appliances and the timing of extractions of certain deciduous teeth aligns the teeth naturally as opposed to orthodontic mechanical movement of permanent teeth into alignment after they have erupted. Research shows that pre-eruption guidance produces far more stable tooth alignment than alternative treatments.

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.

Tooth ankylosis is the pathological fusion between alveolar bone and the cementum of teeth, which is a rare phenomenon in the deciduous dentition and even more uncommon in permanent teeth. Ankylosis occurs when partial root resorption is followed by repair with either cementum or dentine that unites the tooth root with the alveolar bone, usually after trauma. However, root resorption does not necessarily lead to tooth ankylosis and the causes of tooth ankylosis remain uncertain to a large extent. However, it is evident that the incident rate of ankylosis in deciduous teeth is much higher than that of permanent teeth.

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.

Orthodontic indices are one of the tools that are available for orthodontists to grade and assess malocclusion. Orthodontic indices can be useful for an epidemiologist to analyse prevalence and severity of malocclusion in any population.


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Further reading