I want to thank Dr Mew for his interest in one of my favorite clinical and research topics—assessment of the swallowing pattern. His comments are welcome, and I am happy to clarify them briefly.
I strongly agree with Dr Mew that there has been little evidence in the literature about the maturation of the swallowing pattern in young children. The lack of scientific evidence can be explainedd with limited possibilities of clinical examinations because of the anatomic structures of the orofacial region, especially in small children.
In my recent article, “Incorrect orofacial functions until 5 years of age and their association with posterior crossbite” (Am J Orthod Dentofacial Orthop 2009;136:375-81), I reported that the swallowing pattern, as cited in the book by Graber et al, matures from the ages of 2 to 4 years. This statement seemed to be the only standing evidence in the literature about maturation of the swallowing pattern. However, according to the evidence from Ovsenik et al, in a study of children from 3 to 12 years of age, it was clearly concluded that atypical swallowing was present in more than half of the examined children at 3 years of age. It changed dramatically at 6 years of age, but remained present in 25% of the children at 12 years of age. According to that study, the swallowing pattern matures much later during the growth and development period, unlike the results of Graber et al, who found that maturation occurred from 2 to 4 years. The evidence from our research showed that the swallowing pattern is mature in most children no earlier than at the ages 7 to 9 years. Swallowing pattern maturation develops slowly toward the end of the mixed dentition period at the age of 12 years; this agrees with the study by Melsen et al (their study was cross-sectional, whereas ours was longitudinal).
As reported by several authors, especially Graber et al, various factors account for persistence of an atypical swallowing pattern; finger or dummy sucking, bottle feeding, mouth breathing, and tongue sucking can all contribute so that the swallowing pattern matures much more slowly. This agrees with studies by Melsen et al and Ovsenik et al that sucking habits have a direct influence on the developing occlusion, as well as an indirect one through changing the swallowing pattern. Furthermore, nonnutritive sucking habits are reported to be the reason for a retained visceral or atypical swallowing pattern, described by forward tongue posture and tongue thrusting during swallowing, contraction of the perioral muscles, excessive buccinator hyperactivity, and swallowing without tooth contact. Because of the dummy, the tongue changes into a lower position on the mouth floor and thus changes the equilibrium in the oral cavity. According to Proffit, it is questionable whether an atypical swallowing pattern is strong enough to result in a malocclusion (the active act of swallowing lasts only 16 minutes per day). According to his statement, pressure on the teeth should last for at least 6 hours per day to produce tooth movement. Rather than the swallowing pattern, the main causative factor for posterior crossbite development could be the irregular tongue posture on the mouth floor.
What would be the “ideal” swallowing pattern? There is, in general, no ideal swallowing pattern that would suit everyone, but “ideal” is determined at each developmental stage of the dentition. During the years of growth and development, from birth to adulthood, 2 swallowing patterns can be registered. The infantile or visceral type of swallowing is significant in neonates from the age of 6 months. Proprioception causes tongue postural and functional changes; a transitional period follows, and finally an adult or somatic swallowing pattern is established as a result of the normal developmental pattern. We could then state that the “ideal swallowing pattern” is established.
The influence of nutritive and nonnutritive sucking behaviors on the development of malocclusion has been studied by many experts. It was shown also in a study by Melink et al that the positive effects of breast-feeding are difficult to assess because pacifier sucking usually intertwines with breast-feeding. We also confirmed that breast-feeding seemed to be important in preventing pacifier sucking habits, and the correlation analysis confirmed that breast-feeding duration had a reverse relationship with pacifier habit duration.
The longitudinal study that I began during my postgraduate training has inspired me to continue my research in orofacial functions, associated with tongue function and posture. There is no doubt that the tongue has a major role in the etiology of malocclusion. To evaluate its influence on the growth and development of the dentition, noninvasive, objective, and reliable diagnostic techniques are necessary. The use of 2- and 3-dimensional ultrasonography will be an important part of functional diagnostics of tongue function and posture in everyday clinical work.