Nonnutritive sucking behavior

Nonnutritive sucking behaviors are recognized to affect dental occlusion and some dental arch characteristics. A longitudinal study convened by the University of Iowa including 122 children from 18 to 36 months of age shows that there are no significant differences in dental arch dimensions among 6 groups of children having various feeding behaviors (breastfeeding, bottlefeeding) and sucking behaviors (finger, pacifier).

Among the different studies about nutritive and nonnutritive sucking behaviors, the best is, in my opinion, the one convened by Warren and Bishara (AJODO 2002, 121:347-56) (Duration of nutritive and nonnutritive sucking behaviors and their effects on the dental arches in the primary dentition). It’s a longitudinal and prospective study (from 1992 to 1995) including 372 children observed from birth until 4 or 5 years of age to evaluate the presence of posterior crossbite, anterior open bite and increased (greater than normal) overjet. Note that the initial cohort included 700 children. The 372 observed individuals who could be included in the study were grouped based on the type of nonnutritive sucking behavior (thumb or pacifier) and the duration of the behavior (less than 12 months, 12 to 24, 24 to 36, 36 to 48 and more than 48 months). Children with a nonnutritive sucking behavior of less than 12 months were further grouped according to the duration of breastfeeding and bottlefeeding.

Results

Effect of breastfeeding

It is difficult to assess the effects of breastfeeding on the dental arch (occlusion) development because it is not easy to separate these effects from those of nonnutritive sucking behaviors. Indeed, most breastfed children (even those who are not breastfed) also engage in nonnutritive sucking behaviors. The creation of a subgroup based on the criteria of a nonnutritive sucking behavior of less than 12 months allows the investigation of the effect of the length of breastfeeding on dental characteristics. The subgroups thus created are:

•No breastfeeding (bottlefeeding): n= 48 individuals

•Breastfeeding less than 6 months: n= 25 individuals

•Breastfeeding 6 to 12 months: n= 33 individuals

•Breastfeeding longer than 12 months: n= 13 individuals

Thus, the prevalence of occlusal characteristics listed below is compared with the duration of breastfeeding as listed in the previous list.

1- Anterior open bite

2- Posterior crossbite

3- Excessive overjet (≥ 4 mm)

4- One or more of the above characteristics

5- Any Class II canine relationship

There were no statistically significant differences between the breastfeeding duration subgroups in any of the occlusal characteristics compared. The authors conclude that prolonged breastfeeding does not show benefits on the prevention of malocclusions compared to a shorter duration of breastfeeding or no breastfeeding at all. Therefore, breastfeeding seems to have little effect on occlusal characteristics of the dentition.

Back to top.

Prolonged pacifier use (> 24 months)

Prolonged pacifier use results in significant changes to the following occlusal characteristics:

1- An increased mandibular arch width.

2- A greater prevalence of posterior crossbites.

3- A greater prevalence of anterior open bites.

The left picture shows that at 24 months of age, undesirable effects caused by a pacifier habit are already present. There is a crossbite (blue arrow) and an anterior open bite (green bar).

She is the little girl of a young mother who underwent an orthodontic treatment at our clinic. It is without saying that I recommended to the mother to cease, on the same night, the pacifier habit during the child’s sleep time immediately and forever…

The increase in the prevalence of posterior crossbites is the result of the combination of an increase in mandibular arch width and a tendency for a decrease in maxillary arch width. Prolonged pacifier habits do not cause excessive overjet (≥ 4 mm) and are not related to a greater prevalence of Class II canine relationship.

Some of these changes to occlusal characteristics persist well beyond the stopping or cessation of the pacifier habit, as you can see on the series of pictures below which show a young boy of 6 years and 8 months of age and who had a pacifier habit that persisted until he was at least 3 years old, as reported by the mother. He shows both of the main side effects of a pacifier habit, namely a posterior crossbite and an anterior open bite.

Back to top.

Finger (thumb) sucking habit

Prolonged finger sucking habit is also associated with significant changes to occlusal characteristics and these changes persist well beyond the cessation of the sucking habit.

These changes are:

1- An increased overjet, which means that the upper teeth are positioned more anteriorly than the lower teeth (green arrow).

2- A greater prevalence of anterior open bite (black arrow).

3- A greater arch depth (red arrow). The arch depth is defined by the distance from the midpoint between the 2 central incisors to the posterior cusp tip of the molars.

4- A narrower maxilla without necessarily the presence of a crossbite.

As for prolonged pacifier habit, modifications to occlusal characteristics persist well beyond the cessation of the thumb sucking habit.

It is not uncommon to observe cutaneous changes on the thumb that is continually in the mouth. The skin becomes thicker, which is easily observable and is caused by the teeth rubbing against the skin. The nail is often chipped and “very clean”. The skin on the ventral surface and at the extremity of the finger will be wrinkled, because it is maintained in the humidity of the mouth. The child or the parent is often surprised when I guess which thumb the child sucks just by looking at and comparing both thumbs.

Back to top.

Conclusion

What needs to be remembered from this study is that a prolonged pacifier habit beyond 24 to 36 months results in a greater prevalence of posterior crossbite at 5 years of age compared to a child who would have ceased the pacifier habit before the age of 24 months or a child who did not have any nonnutritive sucking behaviors. In the same way, children with a thumb sucking habit who cease between 36 and 48 months of age present a greater prevalence of anterior open bite and an increased overjet at 5 years of age compared to children who had shorter thumb sucking habits or had no thumb sucking habits at all.

Thus, short nonnutritive sucking behaviors (less than 24 months) have little impact on the dentition. But if these behaviors persist beyond 2 or 3 years of age, there is a significant increase of the probability of developing undesirable dental arch and occlusal characteristics at the end of the primary dentition stage.

A good trick to break the thumb sucking habit is not to authorize the young child, starting at 12-18 months of age, to have his pacifier available outside his bed. Parents who bring their 24-month-old child outside the house, to the grocery store or to the shopping mall, with the pacifier hooked to the child’s clothes contribute to maintaining the habit.

The opposite picture is from a girl who is about 18-20 months old and who is the daughter of a patient who underwent a major ortho surgery treatment to close an anterior open bite. He was worried about his girl who had the same problem. The picture shows the anterior open bite, the left posterior crossbite and the mismatch of the arch midlines (deviation on the side of the crossbite, blue arrows).

He told me that his daughter has her pacifier very often in the mouth during the day and that she always has her pacifier when falling asleep. I recommended to him that he cut the tip of the pacifier to make it less interesting for a child and not to authorize the pacifier outside the bed. In less than one week, the habit was broken and his daughter does not even think about asking where her pacifier is.

It is more delicate and difficult to break the thumb sucking habit, but it is rather unlikely to see these children with a finger in their mouth in a public place. The sucking habit often satisfies a security need in the child and I have seen thumb sucking habits persist until they are teenagers. Damages to the dentition are then often significant.

Back to top.