Conformity between Pacifier Design and Palate Shape in Preterm and Term Infants Considering Age-Specific Palate Size, Facial Profile and Lip Thickness

Abstract

This retrospective case-control study is the first to examine the spatial conformity between pacifiers and palates in 39 preterm infants (12 females, 27 males) and 34 term infants (19 females, 15 males), taking into account the facial-soft-tissue profile and thickness. The shape of 74 available pacifiers was spatially matched to the palate, and conformity was examined using width, height, and length measurements. In summary, the size concept of pacifiers is highly variable and does not follow a growth pattern, like infant palates do. Pacifiers are too undersized in width, length, and height to physiologically fit the palate structures from 0 to 14 months of age. There are two exceptions, but only for premature palates: the palatal depth index at 9−11 months of age, which has no clinical meaning, and the nipple length at <37 weeks of age, which bears a resemblance to the maternal nipple during non-nutritive sucking. It can be concluded that the age-size concept of the studied pacifiers does not correspond to any natural growth pattern. Physiologically aligned, pacifiers do not achieve the age-specific dimensions of the palate. The effects attributed to the products on oral health in term infants cannot be supposed.

Keywords: growth; non-nutritive sucking; pacifier; palates; preterm infants; term infants.

Figure 1

Measurements obtained from digitized plaster casts. (a) Inferosuperior and (b) lateromedial view of a newborn’s palate. All areas of the scanned plaster cast that were not covered by impression material were digitally removed. The segmented casts were oriented in a 3D coordinate system, according to the raphe palatina mediana, and by symmetrical alignment of the alveolar ridge towards a horizontal reference plane. The most inferior points (z-direction) of the alveolar bone constitute the alveolar ridge (black line). Point p is the deepest point of the palatal vault. Palatal width (pw) is the longest distance in the x-direction and perpendicular to the y-axis between two surface points on the right and left side of the alveolar ridge. Palatal depth (pd) is the distance in the z-direction, between the most inferior and most superior point of the palatal shape. Further measurements are the distance in the anteroposterior (y-) direction from the most anterior point of the alveolar process to the point of maximum palatal width (y-pw) and to the maximum palatal depth (y-pd).

Figure 2

Examination of the infants’ profile, according to Camper’s line (cl). Camper’s line in infants is determined by a line running from the lower edge of the tragus of the ear to the inferior border of the ala of the nose. The lip shield covers the upper lip and lower lip of the child. These have different thicknesses depending on age, but orientation is based on the anthropometric landmarks Subnasale (Sn) and Pogonion molle (Po’).

Figure 3

Measurements according to spatial orientation of the pacifier on the infant’s palate. (a) Lateromedial view on a median section through palate and pacifier. The pacifier is angulated according to the angle between the alveolar ridge plane (ARP, a parallel to Camper’s line) and the lip shield plane (lsp). The horizontal orientation is determined by the lip thickness (lt), a distance between the lip shield plane (lsp) and the most anterior point of the palate (a). The vertical position is determined by the first contact to the palatal shape. In this orientation, the nipple’s palatal depth (npd) is the distance between ARP and the most superior point of the nipple. The length y-npd is the distance between point a and the highest point of the nipple (np) in the anteroposterior (y-) direction, parallel to ARP. The nipple length (nl) is the distance between the lip shield plane and the most posterior border of the nipple, parallel to ARP. (b) Inferosuperior view on the palate is according to the left figure. The pacifier is aligned towards the median plane of the palate. The nipple’s palatal width (npw) is the largest width of the pacifier, and y-npw is the distance from npw to lsp.

Figure 4

Midline submental ultrasound image of an infant’s oral cavity during non-nutritive sucking. The tongue is in a superior position and the maternal nipple rests at the deepest curvature of the hard palate (area of palatal depth). When nutritive sucks are performed, the nipple increases in volume and reaches up to 2.7 ± 1.0 mm to the hard-soft palate junction (HSPJ).

Figure 5

(a) Palatal depth (pd) and artificial nipple depth (npd). Distance in vertical (z-) direction between ARP and the deepest point of the palate (preterm, term) as well as the highest point of the artificial nipple. Compared to the infants’ palates, the pacifiers do not show any increase in size, in terms of a growth effect. (b) Location of the deepest point of the palate and the highest point of the artificial nipple. Distance in the horizontal (y-) direction from the anteriormost to the deepest part of the palate (preterm, term) and from the lip shield plane to the highest point of the artificial nipple minus lip thickness (pacifier). (*) extreme outlier.

Figure 6

(a) Palatal width (pw) and artificial nipple width (npw). The artificial nipple widths show no similarities to the palates. Despite a small increase over time, a growth pattern is not visible. Preterm pacifiers are particularly narrow in dimension. (b) Location of the widest part of the infant’s palate and artificial nipples. Distance in the horizontal (y-) direction from the anteriormost to the widest part of the palate (preterm, term) and from the lip shield plane to the widest part of the artificial nipple minus lip thickness (pacifier). Although the width changes somewhat, the distance to the lip shield does not seem to have been considered in the design of the pacifiers. (*) extreme outlier.

Figure 7

(a) Palatal depth index, a dimensionless parameter of the ratio of pd to y-pd, with no meaning for growth. Pacifier scores are significantly smaller than infant scores, except in quarter 3, and are only related to preterm infants. (b) Palatal width index as a ratio of pw to y-pw. Here, the pacifier values are significantly larger, except in quarter −1. (*) extreme outlier.

Figure 8

Pacifier (intraoral) length, in relation to the anteroposterior distance to the deepest point of the palatal vault. The infant palate values correspond to the position of the maternal nipple during NNS. The lengths of pacifiers are, significantly, too short compared to the palates of term infants. This does not apply to the palates of preterm infants in quarter −1 and 0. (*) extreme outlier.

Figure 9

Preterm pacifiers placed into a palate of a female preterm infant of 35 weeks of gestational age. The length of the artificial nipples and the basic design vary considerably. For example, the shortest artificial nipple a is 4.04 mm shorter than the smallest and 7.88 mm shorter than the largest preterm measurement in this group. (a) = nup01; (b) = wt; (c) = bff; (d) = nup00; (e) = jpp; (f) = cus; (g) = ws.