What is thumb sucking

Thumb sucking is one of the most common habits of babies and young children. The thumb sucking habit starts early in life. About 90% of newborns show some form of hand sucking by 2 hours after birth. Thumb sucking is one of the earliest reflexes exhibited and is a very strong urge in young babies. Sucking behaviors are very common in babies and young children as they give a feeling of security and many parents introduce the use of pacifiers to babies to help them settle.

Although the incidence of thumb (finger) sucking habits varies considerably between different countries, these comforting habits are common in children in many populations. A Swedish study looked at 60 consecutive births and found the incidence of thumb (finger) sucking to be 82% during the first five months of life ¹ and a USA‐based study reported the incidence as 73% for a group of 130 children between two and five years of age ². The incidence of thumb (finger) sucking reduces with age. Available data has shown that around 48% of four‐year‐olds maintain a digit or pacifier sucking habit ³, 12.1% of children past the age of seven years ⁴, reducing to 1.9% of children by 12 years of age ⁵.

Thumb sucking is normal in infants and young children ⁶. Thumb sucking is a form of non-nutritive sucking occurring as early as the 29th week of gestation and is seen commonly in infants and peaks at 18 to 21 months of age ⁷. Thumb/finger sucking habits, or non-nutritive sucking are considered to be the most prevalent of oral habits, with a reported incidence ranging from 13% to almost 100% at some time during infancy ⁶. Thumb sucking should cause no permanent problems if it stops by age 5. It is also generally harmless for babies to use pacifiers (dummies or soothers). There are other positive effects of pacifiers in young children, which may also contribute to their widespread use. The use of pacifiers has been shown to reduce crying in children during painful experiences such as venepuncture, and has been advocated for use in pediatric emergency departments ⁸. Pacifier placement for babies going to sleep has also been identified as a factor in the reduction of sudden infant death syndrome (SIDS) ⁹, although the mechanism behind this is currently unknown. However, the incidence of SIDS (sudden infant death syndrome) is highest at two to four months and declines towards zero at one year of age and therefore is not a reason for encouraging continuation of pacifier use in children over the age of two and a half years, when primary teeth are all present in the mouth.

Most children stop thumb sucking on their own between the ages of 2 and 4 ¹⁰. Thumb sucking persisting beyond 3 to 4 years of age is usually due to physical and emotional stimuli, such as boredom, hunger, stress, hyperactivity, pleasure, sadness, and various kinds of disabilities ¹⁰. Increase in the child’s level of stress or anxiety can also account for continuation of the thumb sucking habit ¹¹.

Experts believe that pacifier may actually be better than thumb sucking for the following reasons:

• Pacifiers are softer and cause less damage to the teeth.
• The plastic rim on the pacifier eases some of the tension placed on the teeth.
• Pacifiers can be cleaned.

Talk with your child’s healthcare provider or dentist if you are concerned with your child’s thumb sucking.

There is no reason to be concerned until the adult front teeth start erupting or breaking through the surface around the age of six. At this point, some problems may occur, these adult teeth will grow into the wrong position causing them to stick out too far or not meet properly when biting ¹¹. As a result these children often need dental treatment to fix the problems caused by their sucking habit. The intensity of the thumb sucking is a factor in determining if problems might develop. If your child is an aggressive thumb sucker and damage is being done to the baby (primary) teeth, see your child’s dentist. Other problems that may occur with thumb sucking are sore thumbs, infections, and calluses on the thumb.

Reported maxillary changes associated with a prolonged sucking habit are proclination of the maxillary incisors, increased maxillary arch length, anterior placement of the maxillary apical base, increased sella-nasion-point A angle, and decreased palatal arch width ¹², ¹³. Effects on the mandible include proclination of the mandibular incisors, increased intermolar distance and decreased sella-nasion-point B angle ¹². Other dental alterations are increased overjet, decreased overbite and posterior crossbite ¹⁴. The response to the changes in the axial inclination of the incisors is anterior rotation of the occlusal plane. Underlying mechanisms of the mal-occlusion are direct pressure from the digit and reduced intraoral pressure produced by sucking ¹².

Figure 1. Thumb sucking teeth (note the mild open bite between the front teeth)

[Source ¹⁰]

How to stop a child from sucking thumb

Several methods have been described for the treatment of finger-sucking habits in the literature; these methods can be classified as (a) preventive therapy and (b) appliance therapy. Preventive methods include the application of adhesive tape or bitter solution and or wearing a sock, mitten, gloves, thumb guard, long-sleeve gown. Appliance therapy includes the use of fixed or removable habit breakers designed to make the sucking habit difficult or unpleasant ¹⁵. Explanations appropriate to the age of the child and positive reinforcement are other treatment options for digit suckers and are also necessary for the success of clinical management ¹⁶.

A Cochcrane review ¹⁷ found low quality evidence that orthodontic appliances (palatal arch and palatal crib) and psychological interventions (including positive and negative reinforcement) are effective at improving sucking cessation in children. There is very low quality evidence that palatal crib is more effective than palatal arch. There is insufficient evidence to determine the effect of other interventions evaluated for the cessation of digit sucking in children. Clinical experiences have shown that a bitter solution usually has a limited effect ¹⁵. Although it is not possible to draw definitive conclusions from the data, in the case of a digit sucking habit, given that the use of bitter solution requires no clinical input, is a non‐invasive, low risk procedure, is cheap and can be carried out by parents in the home setting, it is likely to continue as first line of treatment despite little evidence to support it.

Figure 2. Orthodontic deterrent appliance for thumb (finger) sucking in young children

Some of the methods discussed above have certain disadvantages. Adhesive tapes may cause infection, sweating and may also reduce the blood circulation ¹⁸, while the stuff worn on the hand can easily be removed involuntarily during sleep. Use of altered child’s pajamas to prevent the movement of hand to mouth usually increases the child’s frustration and wakefulness ¹⁹; also, the pajamas method can be used only if the habit is performed during sleep. Fixed orthodontic habit breaking appliance can cause decalcification of enamel surfaces making them more susceptible to caries and gingival inflammation may also occur; additionally removable appliances need patient cooperation. Intraoral habit breaking appliances can also cause deviation in speech and pronunciation ¹⁵. Fixed intraoral appliance may create difficulties while eating and mentally disabled children may try to remove their appliance and may frequently break it. On the other hand, removable appliances require patient compliance, making it impossible for children with mental retardation ²⁰.

The ‘three-alarm’ system introduced by Norton and Gellin ²¹ by applying an appliance on the patient’s elbow is often effective in stopping the thumb sucking habit in the mature child and has some advantages over orthodontic habit breakers as it does not create difficulties during speech and chewing. Above all, general anesthesia is not required to make the impression of the elbow.

Figure 3. Modified elbow guard for thumb sucking treatment

[Source ¹⁰]

Figure 4. Modified elbow guard for thumb sucking treatment (acrylic elbow guard with switch button on the inner surface of the acrylic elbow guard)

Figure 5. Modified elbow guard for thumb sucking treatment (acrylic elbow guard with musical chip and speaker on the outer surface of acrylic elbow guard)

The ‘three-alarm’ system elbow guard appliance has a microchip that may be incorporated with the favorite music such that the child may indulge in hearing the music and stop the thumb/digit sucking habit. However, at school the music may be a disturbance, so the vibration chip used in mobile phones can be used so that vibrations in the elbow guard can remind the child not to suck the thumb/digit. A siren which a child is scared off also can be incorporated to remind or alarm the child to stop the habit.

Clinical observations revealed that the patient accepted the elbow guard appliance easily. They found it fashionable like a sports wear, so they did not try to remove it. The elbow guard was firm enough to prevent the child from removing the appliance and was also loose enough to allow limited movement and did not interfere with the blood flow and also the finger was protected from the harmful effects of biting. The child abandoned the habit in a short time since the appliance prevented the pleasure of sucking and, interestingly, the music reminded him to stop the habit and was distracted from sucking pleasure.

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