Growth of the hard palate in infants with Down syndrome compared with healthy infants-A retrospective case control study

Abstract

Objective: To investigate morphological differences of the hard palate in infants with Down syndrome (DS) compared with a volumetric-matched control group (CG).

Methods: Trial design: retrospective case control study. Based on inclusion and exclusion criteria, plaster casts of edentulous maxillae of 40 DS infants (20 females and 20 males, aged 221.3 ± 132.4 days) and 40 CG infants (20 females and 20 males, aged 53.9 ± 87.2 days) were digitized and converted into 3-dimensional stereolithography data. An automated landmark- and investigator-independent method for assessing two-dimensional measurements such as width, depth, and length of palate, as well as palatal index and the 3-dimensional volume, were used.

Results: Matching DS and healthy CG infants by age, we found reduced sizes in all linear and volumetric measurements in the DS group. Matching both groups by palatal volume, we found no differences between the groups according to palatal width (p = .93), palatal depth (p = .32), and palatal index (p = .31). Control infants with the same palatal volume compared with the DS infants were about 151 days younger, 95%-CI = [102, 200] (Hodges-Lehmann estimator). Except for palatal length and palatal volume, the growth pattern of DS palates decreased irregularly at age 6 to 9 months.

Conclusions: The palate of DS infants in the first 6 to 9 month of life is of normal shape but considerably smaller compared with healthy normals. From 6 to 9 months onward, the growth pattern of the hard palate in DS infants decreases irregularly. High-arch-constricted palates could, therefore, be interpreted as secondarily acquired in later life. We therefore speculate that it could be advantageous to begin oral muscular stimulating therapy between 6 and 9 months of age which may prevent palatal shape alterations and enhance oral function which also contributes to maxillary development.

Fig 1. Measurements obtained from digitized plaster casts.

Left: Digital plaster cast of a newborn’s palate. Right: Segmented cast. All areas of the cast that were not covered by impression material were digitally removed. The segmented casts were then 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 highest points (z-plane, view direction) of the alveolar bone constitute the alveolar ridge (black line). Point p is the deepest point of the digital cast in the z-plane. A transverse (black) section line passing through point p represents the distal border of the palate for volume calculations. Palatal length (pl) is the longest distance parallel to the y-plane between the most anterior and the most posterior point. Palatal width (pw) is the longest distance parallel to the x-plane and perpendicular to the y-plane between 2 surface points on the right and left side of the alveolar ridge. Palatal depth (pd) is the longest distance parallel to the z-plane between the highest and the deepest point of the cast. The calculated palatal volume is the volume enclosed by the maximum contour line of the alveolar ridge and the dorsal border line determined by the deepest point p.

Fig 2. Results of matching DS patients with healthy controls according to the parameter palatal volume [mm³].

Fig 3. Measurements in relation to age at the time of plaster cast fabrication.

Age aggregated into quarters (Q1: ≥1 day <92 days; Q2: ≥92 days <183 days; Q3: ≥183 days <274 days; Q4: ≥274 days <365 days). Represented are the median values per quarter. Q1 (n = 37), Q2 (n = 20), Q3 (n = 7), Q4 (n = 9); Q5 and Q6 are not displayed because of missing controls.