Introduction

Sucking is a reflex action occurring in the oral stage of development and is seen even at 29 weeks of intrauterine life and may disappear during normal growth between the ages of 1 and 3 1/2 years. It is the first coordinated muscular activity of the infant which meets both psychological and nutritive needs during feeding, deprivation of which leads to restless and irritability and this may motivate the infant to suck the thumb or finger for additional gratification. Thumb sucking is placement of the thumb to various depths into the mouth. Reviews from literature have shown a large variation in the incidence of digit sucking according to age. Larsson et al (1985) reported that while up to 50% of children may have had a sucking habit in infancy, by the age of 12 years the habit may remain in as few as 2% of the population.

Thumb sucking can be grouped as

Normal Thumb Sucking:

During first and second year of life thumb sucking is considered normal. Such a habit is usually seen to disappear as the child matures and does not generate any malocclusion.

Abnormal Thumb Sucking:

If habit persists beyond the preschool period (6 years) then it could be considered as an abnormal habit. If not controlled during this stage, it may cause deleterious effects to the dentofacial structures. This can again be divided into :

1. Psychological: There is a deep-rooted emotional factor involved and may be associated with insecurities, neglect or loneliness experienced by the child.
2. Habitual: The habit does not have any Psychological bearing; the child performs the act out of habit and it causes malocclusion.

What are the Causative factors

1. The sucking habit is commonly observed to be present in children with working mother. Such children brought up in the hands of a caretaker may have feelings of insecurity. Therefore, they use their thumb to obtain a secure feeling.
2. The development of the habit can be indirectly related to the number of siblings. As the number increases the attention met out by the parents to the child gets divided. A child neglected by the parents may attempt to compensate his feelings of insecurity by means of this habit.
3. It has been noticed that later the sibling ranks, greater is the chance of having an oral habit as to some extent siblings imitate one another in thumb sucking.
4. Digit sucking is as an emotion based behaviour related to difficulty with social adjustment or with stress. Although sucking for psychological satisfaction as well as for food is considered normal in infancy, digit sucking in older children has been told to be associated with abnormal psychological development. The psychological effects may be compounded by the emotional impact of peer pressure and punitive and scolding parents.
5. Abrupt weaning from the bottle or breast may contribute to oral habit.

Maintenance of the habit

Most children would cease digit sucking early in their developmental process by the age of three to four years. But an acute increase in the child's level of stress or anxiety due to some underlying psychological or emotional disturbances can account for continuation of a digit sucking habit, with conversion of an empty habit into a meaningful stress reduction response.

Age of the child

1. The time of appearance of digit sucking habit has significance.
2. In the neonate: Insecurities are related to primitive demands as hunger.
3. During the first few weeks of life: Related to feeding problems.
4. During the eruption of the primary molar: It may be used as a teething device.
5. Still later: Children use the habit for the releases of emotional tensions with which they are unable to cope, taking refuge in regressing to an infantile behaviour pattern.

How to know about the presence of thumb sucking

History

It determines the psychological component involved:

1. Question regarding the frequency, intensity and duration of the habit.
2. Intensity is how vigorously the habit is pursued. The digit may rest passively in mouth or may be sucked with enthusiasm. Frequency denotes how often the day the habit is practiced - a few minutes while the child is falling asleep or almost never without a digit in the mouth. Duration indicates the number of years the habit is continued.
3. Enquire the feeding patterns, parental care of the child.

Not all habits will result in tooth movement. Studies by Weinstein et al. (1963) suggest that it only takes very light forces to move teeth, if the force is of long enough duration. The threshold is believed to be 6 hours. This means that a thumb lightly resting in the mouth throughout the night may result in significant dental changes, whereas a vigorous but intermittent sucking habit may have minimal effect in moving the teeth.

Extra oral examination

The digits

Digits that are involved in the habit will appear reddened, exceptionally clean, chapped and with a short fingernail i.e. a clean dishpan thumb (Forrester 1981). Fibrous roughened callus may be present on the superior aspect of the finger. The habit may cause deformation of the finger.

Lips

Chronic thumb suckers frequently have short, hypotonic upper lip whereas lower lip is hyperactive.

Intra oral examination

Tongue

Examine the oral cavity for correct tongue size and its position at rest and its action during swallowing.

Dentoalveolar structures

Individuals with severe finger or thumb sucking habits, where the digit applied an anterior superior vector to the upper dentition and palate, will have flared and proclined maxillary anteriors with diastemas and retroclined mandibular anteriors.

Other intraoral symptoms will include a high probability of buccal crossbite, particularly in those children who suck their digits with a pronounced constriction of their buccal musculature and a tendency to narrow palates. Cheek pressures are greatest at the corners of the mouth and this probably explains why the maxillary arch tends to become ‘V’ shaped with more constriction across the canines than the molars.

Asymmetry of incisal position of upper central and lateral incisors indicates that the child sucks the right or left thumb or finger by preference. The anterior open bite may arises by the interference with normal eruption of incisors due to an interposed thumb or excessive eruption of posterior teeth due to separation of the jaws, which alters the vertical equilibrium on the posterior teeth, 1 mm of elongation posteriorly opens the bite by about 2mm anteriorly.

Gingiva

Look for the evidence of mouth breathing, gum line etching; excessive staining on labial surface of upper central and lateral incisors.

Preventive measures to stop thumb sucking

1. Etiology (cause) of thumb sucking focuses on a predominant psychological background which should be removed.
2. Child's engagement in various activities gives little chance for the child to practice the habit. The child can be encouraged to follow his hobbies of interest such as painting or engaging in outdoor activities with his fellow mates.
3. Parents should spend ample time with the child so as to put away his feeling of insecurity.
4. Duration of breastfeeding should be adequate so as to enable the child to exhaust his sucking urge and feel completely satisfied.
5. Bottle-fed babies should be held by the mother and attention should be given as it will promote a close emotional union between the mother and the baby similar to that seen in breast-feeding.
6. Children whose behaviour indicates an urgent desire to suck a digit can be prevented by encouraging the baby to suck a dummy instead. Dummies are easier to dispense with at an earlier age than is digit sucking.

Things to keep in mind before starting treatment

• Psychological status of the child: Diagnosis and management of any psychological problem should be planned before treating habit. The events that precede the habit such as the use of a security blanket, the dependency on a favourite toy, problems with sleep, nightmares, nervousness and anxiousness will yield information concerning the possible psychological stimuli of the habit. If the oral habit was, associated with an emotional problem this would suggest the need for psychological consultation.
• Age factor: If the child desists with the finger sucking habit within the first three years of life, the damage incurred such as open bite will temporarily provide the child occlusion is normal. No treatment is provided in this age. If a malocclusion is caused by digit sucking and the habit is discontinued between the age of 4 and 5 years, self-correction of the habit can be expected. When digit sucking continues after 6 years or into mixed dentition, the malocclusion will not self correct.
• Motivation of the child to stop the habit: The treatment approach for the digit sucking habit should deal directly with the child. The first ingredient needed to stop the habit is the child's desire to stop.
• Parental concern regarding the habit: It is important that the child should not be embarrassed or criticized; rather help should be offered to deal with this difficult habit. Negative reinforcements in the form of threats, nagging and ridicule would only entrench the habit.

Treatment

The treatment plan can be broadly divided into the following:

Psychological therapy

It is wise to begin with the discussion of the problem with the child alone. No threats or shaming should be used; instead a calm and friendly attempt should be made to learn about the child’s attitudes towards the habit. Many children will say that they suck their thumb only when they are asleep and also declare sincerely that they want to be rid of the habit.

1. Thumb sucking children between the ages of 4 and 8 years of age need only reassurance, positive reinforcement and friendly reminders.
2. During the treatment adequate emotional support and concern should be provided to the child by the parents.
3. Destructive approaches in the form of nagging, shaming and belittling ought to be strictly avoided.
4. Constant reassurance and encouragement should be provided to the child to gain his confidence.

Dunlop's beta hypothesis

He believed that if a subject can be forced to concentrate on the performance of the act at the time he practises it, he can learn to stop performing the act. Forced purposeful repetition of a habit eventually associates it with unpleasant reactions and the habit is abandoned. The child should be asked to sit in front of a mirror and asked to suck his thumb, observing himself as he indulges in the habit.

Reminder therapy

This can be divided into the following:

Extra oral approach

It employs hot tasting, bitter flavoured preparations or distasteful agents that are applied to finger or thumb. For example, Cayenne pepper, quinine, asafoetida. Thermoplastic thumb post can be used where a thermoplastic material was placed on the offending digit.

Intraoral approaches

The use of a corrective appliance to manage oral habits is indicated only when the child wants to discontinue the habit and needs only a reminder to accomplish the task.

1. Removable appliances: Palatal crib, Rakes, palatal arch, lingual spurs, Hawley's retainer with or without spurs
2. Fixed appliances: Upper lingual tongue screen

For fixed appliances a time period of 3 months is assigned as a goal. In most of instances the habit disappears after first week of appliance wear.

Mechanotherapy

Fixed intra oral anti thumb sucking appliance

It is the most effective intraoral appliance attached to the upper teeth by means of bands fitted to the primary second molars or first permanent molars is the most effective mechanical deterrent to thumb sucking. A palatal arch with interlacing wires in anterior part of hard palate is recommended. It works by preventing the patient from putting the palmar surface of the thumb in contact with the palatal gingival thereby robbing the pleasure of sucking.

Blue grass appliance

It helps in breaking thumb sucking habit in children which affects mixed and permanent dentition. It consists of a modified six-sided roller machined from teflon to permit purchase of the tongue. This is slipped over wire soldered to molar orthodontic bands. It is placed for 3-6 months. Instructions are given to turn the roller instead of sucking the digit.

Quad helix

It prevents the thumb from being inserted and also corrects the malocclusion by expending the arch.

Home Remedies for Thumb Sucking

Try ordeal therapy. How about trying a little reverse psychology? Point out to a thumb-sucking child that he or she isn't being fair to the other fingers -- so why not suck them, too? Give the child a timer and explain that it's important to suck all fingers for the same duration. Often, the child will grow so tired of the process that they quit thumb sucking altogether. The only problem with this type of approach is that kids are likely to see through it when it comes from a parent (they know the parent really wants them to stop altogether).

Have them hold balls in their hands while they sleep so their hands are busy. Have them wear a large shirt with long sleeves. Button it completely on and tie the arms or rubber band them shut so they cannot suck on their thumb. Ace bandages approach can also be used; it involves nightly use of an elastic bandage wrapped across the elbow. Pressure exerted by the bandage removes the digit from the mouth as the child tires and fall asleep. Start with the easy stuff and then move on. First, you might suggest that the child stop thumb sucking while in public, or some other time when he or she is most likely to comply. Then you can move on to the times when the habit is most ingrained, such as bedtime. You may want to double rewards if the child doesn't suck his or her thumb during the more challenging times.

References

1. Dental clinics of North America, pediatric dentistry. 2000.
2. Larsson E and Dahlin KG. The prevalence and the aetiology of the initial dummy and finger sucking habit. American Journal of Orthodontics 87: 432-435, 1985.
3. McDonald, Avery, Dean. Dentistry for the Child and Adolescent. 8th edition; 2004; Mosby Publications.
4. Pinkham, Casamassimo, Fields, McTigue, Nowak. Pediatric Dentistry. Infancy through Adolescense. 4th edition;2005; Saunders Company.
5. Richard J. Mathewson. Fundamentals of pediatric dentistry. 3rd edition, 1995, Quintessence Publishing Co.
6. Shobha Tandon. Textbook of Pedodontics. 1st edition; 2001; Paras Publications
7. Sidney B. Finn. Clinical Pedodontics. 4th edition; 2004; Saunders Company.
8. Weinstein S, et al. On an equilibrium theory of tooth position. Angle Orthodontist 33: 1-26, 1963.