Overview

Thumb sucking and pacifier use are common, innocent habits among young children up to a certain age. Children tend to stop these habits as they get older, by themselves, or with the help of parents and caregivers. If they continue, with increasing age, the act can become a point of concern. 

Beneath their seemingly harmless facade, thumb sucking and pacifier use hold important implications for both dental health and a child's emotional well-being. The crucial question is: when does this habit of comfort-seeking cross the line into something to worry about? For parents, it's of paramount importance to identify when the habit becomes problematic and seek guidance on it. 

When does it start?

Thumb sucking 

Thumb (digit) sucking is one of the initial manifestations of coordinated muscular activity that a child develops during their early months and is regarded as a physiological phenomenon.¹ It serves as an initial step in a child's development of self-regulation and emotional control, often associated with pleasure. 

This behaviour is grouped under ‘non-nutritive sucking habits’, or when a baby sucks without any nutritional value.² It can even manifest in the uterus, around the 29th week of gestation. It is commonly observed in infants, reaching its peak between 18 to 21 months of age. During this habit, the thumb is typically positioned against the palate, with adjacent fingers curling over the nose or forming a closed fist.³ 

Thumb sucking can be classified into two types:

• Active: There is considerable force exerted by the muscles during sucking 
• Passive: The child places their finger in the mouth without exerting significant force on the teeth and mandible 

Pacifier use

Children also suck on other objects like pacifiers (dummies) or blankets to self-soothe. A pacifier resembles a teat in material (rubber, plastic, or silicone) and shape which is inserted into the mouth of the infant. It features a broad, flat plastic disk that covers the child's mouth to prevent ingestion, distinguishing it from a teat. 

A parent or caregiver usually introduces the pacifier to the child due to personal choice or external advice for various reasons.⁴ The choice of whether to use pacifiers for infants and children is still a matter of debate and a personal decision for modern-day parents. A baby who feeds well and is content may not require a pacifier and shouldn't be encouraged to use one.⁵ 

How does it start?

Thumb sucking 

The development of sucking is a natural reflex that appears early in infants and occurs spontaneously. Several theories are associated with the cause of thumb sucking habit, such as:

• Psychoanalytic theory (Freud, 1905): Digit sucking is viewed as an autoerotic behaviour or pleasure-seeking act linked to underlying emotional issues
• Learning theory (Palermo, 1956): Non-nutritive sucking is seen as an adaptive response, offering satisfaction and anxiety reduction without a necessary psychological cause
• Oral drive theory (Sears and Wise, 1982): Thumb sucking may stem from the prolongation of nursing, reinforcing the oral drive in children
• Oral gratification theory (Sheldon, 1932): Unsatisfied sucking needs that occur during breastfeeding may lead infants to use digit sucking as a substitute³

Pacifier use

In contrast to thumb sucking, the introduction of pacifiers to infants is due to their parents or advice from relatives and midwives. The primary reasons cited for pacifier use included soothing the infant, aiding in sleep, and providing comfort and quiet.⁶ 

What are the prevalence rates?

The scientific studies regarding the prevalence of non-nutritive sucking and the influence of factors like gender, geographical status, socioeconomic status, maternal education level, and cultural norms vary.⁸ According to a study in Nigeria, the prevalence of non-nutritive sucking was 45.2%, with no significant difference between males and females.⁹ The data from an epidemiological study on digit habits in the UK, conducted in Kettering in 2008, 12.1% of children continued to have a prolonged digit habit beyond the age of 7 years.¹⁸ 

While some studies show that mothers with higher levels of education and income are more likely to breastfeed their children naturally and avoid harmful habits, others reveal a high prevalence of prolonged non-nutritive sucking habits, particularly in more developed regions. A shorter duration of breastfeeding and prolonged use of a bottle were consistently linked to a higher prevalence of prolonged non-nutritive sucking habits.^6,9 Conversely, early pacifier use leads to early weaning in breastfeeding.⁷ Exclusive breastfeeding can discourage pacifier use.

When should you worry?

Thumb sucking 

The urge to suck their thumb decreases in children as they get older. It also becomes more socially unacceptable. For some, it continues beyond toddler years and becomes a habit. Various physical and emotional stimuli, including but not limited to boredom, hunger, stress, 

hyperactivity, pleasure, sadness, and different types of disabilities, can contribute to this behaviour. 

However, most children naturally cease thumb or finger-sucking between the ages of 2 and 4 years without any external intervention. During this developmental stage, the behaviour tends to diminish gradually as children become more engaged in exploring their environment. Peer influence often motivates school-aged children to discontinue the habit of placing their fingers in their mouths.¹⁰  By the time the permanent teeth erupt, these habits become a concern and intervention is required.

Pacifier use

According to NHS recommendations, it is advised to phase out the use of a pacifier between 6-12 months.⁵ Parents should be concerned if pacifier use begins to interfere with breastfeeding. 

The use of a pacifier beyond 3 years of age can adversely impact dental development, with even more pronounced effects if its use persists beyond 5 years old. It is recommended to replace pacifiers in children who also have a habit of finger sucking, as the detrimental effects of pacifier use are considered to be less severe than those of finger sucking.¹

What are the effects?

Thumb sucking 

Habits that occur frequently, last for extended periods, and are carried out with significant intensity may be linked to dental or skeletal deformities. The duration of sucking holds more significance than how forceful the child sucks their thumb. Consistent pressure exerted by the lips, cheeks, and tongue during rest periods has the most significant impact on tooth position, as these forces are sustained for the majority of the time. The force disrupts the growth and typical development of the jaw, leading to the emergence of malocclusion.¹¹ It interferes with the process of tooth eruption leading to delayed eruption and malformations.¹ 

The connection between oral habits and unfavourable dental and facial development is more associative than causal. Some of the common malocclusions secondary to thumb-sucking are:

• Anterior open bite (AOB) 
• Protruded upper incisors
• Retruded lower incisors
• Spaced upper dentition
• Increased overjet 
• Posterior crossbite 
• Diastema
• Narrowing of the upper arch
• Retrognathic mandible
• Temporomandibular joint disorders¹
  

Other complications include alterations in regular swallowing and speech patterns. Still, they are less common.¹ Excessive thumb sucking can cause skin irritation, blisters, or calluses on the thumb, leading to discomfort or pain.

Pacifier use

For pacifier use, there is moderate evidence indicating that it is linked to the development of an anterior open bite and posterior crossbite, thereby impacting the balanced development of orofacial structures.¹²  

Introducing a pacifier when a baby displays hunger cues may mask their need for feeding, potentially leading to reduced feedings and weight loss.⁵ Several observational studies show a strong association between pacifier use and early weaning. Certain studies have found a correlation between pacifier usage and increased occurrences of yeast infections, as well as elevated levels of these microorganisms in the oral cavity. Pacifiers can be considered a fomite, but their ability to cause clinically significant infections is still questionable. 

Pacifier sucking may impair the functioning of the eustachian tube and the pressure balance between the nasopharynx and the middle ear.¹³ Pacifier use is considered to be one of the risk factors for the occurrence of otitis media. Using a pacifier at the beginning of sleep may potentially decrease the risk of sudden infant death syndrome (SIDS). However, the evidence supporting this claim is inconclusive and NHS does not recommend pacifiers for this purpose.^5,14

Management and intervention strategies

Thumb sucking

Treatment of thumb-sucking habits must take into account the child's developmental stage, understanding, and willingness to cooperate. Approaches to addressing these habits may involve counselling sessions for both the patient and parent, behaviour modification techniques, myofunctional therapy, appliance therapy, or referral to various specialists such as orthodontists, myofunctional therapists, or psychologists.¹⁵ 

Some of these interventions are easier to apply, less disturbing for the child and their parent, and some are more applicable to a particular type of habit.¹⁶ The motivation to stop the digit-sucking habit should come from the patient, particularly before the use of any external interventions, like appliances. It's crucial to recognise and address the underlying triggers that lead to the habit in the first place.¹⁶

Parental intervention

Addressing the digit-sucking habit in a child requires the cooperation of both the child and their parents.¹⁶ Some suggestions are:

• Talk to the child about the ill effects of thumb sucking
• Offer praise when the child refrains from thumb sucking 
• Use fabric sticking plasters on the thumb
• Apply bitter-tasting nail varnish to the thumbnail
• A glove on their hand to prevent access to their fingers
• Use thumb guards
• Recognise and focus on addressing the root cause of the child's anxiety, providing comfort and reassurance

Professional intervention

Non-orthodontic intervention

The dentist can counsel the child to stop sucking their thumb by explaining what could happen to their teeth if it continues. 

Before initiating intervention, a 1-month period of parental attention is advised. Treatment involves a mix of monitoring through charts, rewarding successful days, and employing external cues to remind the child. 

Orthodontic intervention

According to the British Orthodontic Society, if a sucking habit ceases by age 7, natural growth can often lead to self-correction. 

The use of orthodontic appliances, whether removable or fixed, to address oral habits is recommended only when the child desires to quit the habit. The child should be assured that the appliance is a reminder and not a punishment. Appliances act as a mechanical barrier as well as a physical reminder. In instances of prolonged habits or with patients who are resistant to change, a fixed intraoral appliance proves to be the most effective deterrent.¹⁷

The orthodontic appliance, used long or short-term, or with psychological intervention, showed a greater likelihood of halting digit sucking compared to no treatment.¹⁵ The most commonly used orthodontic appliances are: 

• Palatal crib 
• Palatal arch 
• Palatal bars 
• Hay rakes 
• Bluegrass appliances² 

Following the active phase of treatment, the appliance should be retained for an additional 3 to 6 months to reduce the risk of relapse.¹⁷

Pacifier use

When providing an infant with a pacifier, it should be clean and without any sweeteners.¹⁰ The Canadian Dental Association advocates for pacifiers over thumb sucking as they are easier for parents to manage in terms of the sucking habit. They discourage the use of sugar, honey, or corn syrup on pacifiers due to the potential risk of promoting cavities.¹³ 

Summary

Thumb sucking and pacifier use is typical in young children, aiding in self-regulation and comfort. While generally innocent, prolonged habits can affect dental health and emotional well-being. Children typically stop thumb-sucking by age 4. However, interventions may be necessary if it persists. Both habits can lead to dental malocclusions and speech issues. Management strategies include parental interventions, such as positive reinforcement, and professional treatments, like orthodontic appliances. It's crucial to address underlying triggers and educate parents on proper usage to mitigate potential risks and ensure children's oral and emotional development.

FAQs

1. When should thumb-sucking stop?

According to most experts, children under the age of 5 who suck their thumbs shouldn't be pressured to quit. Typically, children will naturally cease the habit before starting school.

• Does thumb sucking affect teeth?

Prolonged and forceful thumb-sucking may occasionally result in misalignment of permanent teeth or impact the jaw and mouth structure. 

• Does thumb-sucking increase immunity?

Research showed that people who had a habit of thumb-sucking as children developed fewer allergies, suggesting that they were developing immunity to different bacteria by directly placing the thumb in their mouths.

• When should a pacifier be avoided?

Pacifiers should be avoided when they affect your baby's feeding patterns in frequency or duration. or struggles with weight gain. It should also be avoided when the child has repeated ear and tummy infections.

• Why is a pacifier better than a thumb for a child to suck?

Using a pacifier offers the benefit of controlling when your child can use it and the ability to remove it when necessary. It is relatively easy to break the habit of pacifier use.