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Health Matters

Thumb and Digit Sucking in Children - What You Didn’t Know

October 31st, 2013

By Dr. Kelly Brooke

Sucking is a normal, instinctive behaviour that is essential to survival.  The habit is derived from a physiological need for nutrients, and is one of the first neurological reflexes to develop in humans.  Generally, sucking habits during the first five years of a child’s life; where the primary teeth are present, have little or no long term effects.  If the habit persists beyond the time the adult teeth begin to grow in, numerous abnormalities in a child’s occlusion (bite) may start to develop.  These aberrations in a child’s occlusion cover a wide spectrum of severity, both in terms of tooth position and jaw development.  For this reason, it is recommended that parents have their children examined by an orthodontist around age seven.

Sucking provides peripheral stimulation which is necessary for normal development of an infant’s central nervous system.  Sucking has also been implicated in the neurological development of cognitive learning, emotional wellness; and the sensations of temperature, texture, size and proximity.  An infant’s first association with pleasure is related to sucking and eating.  Breast milk or formula contains Tryptophan which is converted into Serotonin by the brain.  In turn, Serotonin induces a calming effect on the central nervous system by causing an increase in endorphin production.  Endorphins are “natural painkillers” released by the brain, most often during vigorous physical exertion. Many athletes often experience a euphoric feeling or “runners high” during marathons or sporting events due to such stimulation of endorphin production.   It is therefore, easy to understand why digit or pacifier sucking becomes a source of pleasure, self-gratification and comfort to the infant.  Children who neither receive unrestricted breast feeding nor have the access to a pacifier may opt to satisfy their needs with alternatives such as blankets or toys.

Fetuses are routinely observed via ultrasound to be sucking their digits in utero and may continue the activity after birth.  There is no gender predilection for digit sucking, and approximately 50 per cent of infants at one year of age practice the habit.  In most children after the first year of life, digit sucking rapidly diminishes; with an average age of four years wherein the habit is completely eliminated.  It is no longer considered normal if the habit persist beyond the age of six-years.

Typical digit sucking habits exert anterior protrusive forces on the upper front teeth, while simultaneously placing posterior retrusive forces on the lower front teeth.  Likewise, during sucking activities, the muscles of the lips and cheeks place significant contractile forces upon the upper back teeth, directed inward and toward the tongue.

The degree of severity of bite abnormalities which these forces can elicit is dependent upon the intensity, duration and frequency of the habit.  Any activity that is minimally practiced once (frequency) per day, for six hours (duration) or more, with enough force (intensity) to draw milk or formula is enough to create significant aberrations in a child’s occlusion if left untreated.

Classical presentations of habit induced bite abnormalities include anterior open bites; caused by an impediment or inhibition of the eruption of both upper and lower front teeth. This form of dental pattern may be accompanied by a secondary tongue thrust habit; where the tongue becomes wedged between the upper and lower teeth during swallowing, in an effort to create an adequate anterior seal.  An excessive overjet; more commonly referred to as overbite; from flared upper front teeth, and inwardly tipped lower teeth, may also develop as a result of sucking habits.  Similar to anterior open bites, excessive overjets may be accompanied by secondary tongue thrust habits.

These abnormalities are dental changes, but they can be accompanied by significant distortions in the tooth bearing (alveolar) and basal jaw bone where the affected teeth are located.  Upper teeth and upper jaw constriction may occur from a change in the balance between the musculature of the cheeks and tongue.  The resting posture of these muscles is altered when the digit displaces the tongue downward and away from the roof of the mouth, no longer permitting the tongue to counterbalance the inherent forces from the cheeks.  Pressures from the cheeks are increased from the activity; compounding the deleterious effects to the teeth and upper jaw.  Classical presentation of these effects include cross bites of the back teeth; where the upper teeth are incorrectly positioned inside the lower teeth.  This form of bite aberration is most often accompanied by a high vaulted V-shaped upper jaw that displaces the tongue; self-perpetuating the effects even when the habit is not being undertaken.

All of these dental and skeletal presentations exemplify the necessity that digit sucking habits should not be permitted after the permanent (adult) teeth start to grow in.  In rare instances where these habits are left uncorrected and are allowed to progress into adolescence or adulthood; significant orthodontic correction is often required, most often with surgical correction of any jaw abnormalities.

Since digit habits spontaneously cease in most children, intervention is usually indicated only if the habit continues past age six or after the permanent teeth appear.  Treatment can consist of several modes; either behaviour modification, mechanical or orthodontic.

 Using a “reminder” makes a child aware of the habit. One modality is to place a waterproof bandage, glove or sock over the fingers or hand. When the child instinctively tries to suck the digit, the physical barrier serves to remind the child of the habit.  This technique produces mixed results; often adamant digit suckers will remove the object covering the digits, thus ignoring the reminder.  Another approach is to place a bitter solution on the child’s finger as a reminder.  Solutions that do not wash off at first are ideal, but availability at drugstore pharmacies may be limited.

 Using a “reward system”, is a technique based upon the concept that if a desired behaviour is rewarded, then the undesirable behaviour will be ignored and eventually ceased.  These can be implemented with verbal contracts or promises, for a specified number of hours or days the undesirable habit is not undertaken.  When using this form of behaviour modification, it is important to choose realistic goals, and use some form of reward that is of value to the child.

 Using an AceTM bandage is a mechanical technique which can be used to aid in the elimination of nocturnal digit sucking habits It consists of a tensor bandage wrapped around a child’s elbow; tight enough for retention, and to allow the child to flex their elbow(s).  Once in bed, the child will find that the digit can be placed in the mouth, but as they fall asleep, the elasticity of the bandage will straighten out and bring the arm (hand) away from the mouth.  This technique has marginal success since it only affects the habit during sleeping hours.

Orthodontic intervention is often used as a last recourse to eliminated digit sucking habits when reminders, rewards and bandage modalities have failed.  Orthodontic habit breaking appliances work by making the child conscious of the sucking habit and by diminishing the pleasurable sensations associated with digit sucking.  These appliances primarily interfere with the child’s placement of the digit into the mouth; and may secondarily act to restrain the tongue during anterior thrusting motions when swallowing. Older children sometimes stop the habit because they dislike the appearance of the appliance; requesting its removal as soon as possible.  Any appliance should remain in place for at least three months after the habit is eliminated.  Premature removal of an appliance may result in the child regressing back the digit sucking habit.

            Commonly used orthodontic appliances used for habit breaking are the Bluegrass Appliance and the Palatal Crib. Both of these appliances are cemented to the teeth; therefore do not rely on child compliance for their usage.  The Bluegrass Appliance consists of a small plastic bead suspended onto a metal wire fitted to the roof of the mouth. This bead interferes with the placement of the digit into the mouth, permitting the tongue to assume it proper position; contacting the roof of the mouth.  The Bluegrass Appliance does not offer any significant restraint against tongue thrust activities.  In severe situations of combined digit sucking and tongue thrusting habits; the Palatal Crib is the appliance of choice.  This appliance is similar in design to its Bluegrass counterpart, but differs to the extent that the plastic bead is replaced by a soldered metal “fence” .The Palatal Crib interferes with digit placement and completely eliminates tongue thrusting by trapping the tongue behind its downward directed fence.  It is important to instil within the child that these appliances are not to act as punishments; but as reminders to stop the deleterious habit.

            Prolonged digit sucking habits can have a negative impact on dental, skeletal, speech and emotional development.  Children can be helped to eliminate their sucking habits effectively, without coercion, and in a positive way if their treatment is initiated at the correct time.  It is therefore paramount, that children be seen by an orthodontist around the age of seven years.

Dr. Kelly Brooke is a certified specialist in orthodontics and dentofacial orthopaedics; he maintains an orthodontic clinic in Fort McMurray. Questions regarding the subject of digit sucking, can be directed towards Dr. Brooke: #212, 9914 Morrison Street, Fort McMurray, AB T9H 4A4, phone: 791-9663.



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