Palatal development of preterm and low birthweight infants compared to term infants - What do we know? Part 1: The palate of the term newborn

Abstract

Background: The evidence on prematurity as 'a priori' a risk for palatal disturbances that increase the need for orthodontic or orthognathic treatment is still weak. Further well-designed clinical studies are needed. The objective of this review is to provide a fundamental analysis of methodologies, confounding factors, and outcomes of studies on palatal development. One focus of this review is the analysis of studies on the palate of the term newborn, since knowing what is 'normal' is a precondition of being able to assess abnormalities.

Methods: A search profile based on Cochrane search strategies applied to 10 medical databases was used to identify existing studies. Articles, mainly those published before 1960, were identified from hand searches in textbooks, encyclopedias, reference lists and bibliographies. Sources in English, German, and French of more than a century were included. Data for term infants were recalculated if particular information about weight, length, or maturity was given. The extracted values, especially those from non-English paper sources, were provided unfiltered for comparison.

Results: The search strategy yielded 182 articles, of which 155 articles remained for final analysis. Morphology of the term newborn's palate was of great interest in the first half of the last century. Two general methodologies were used to assess palatal morphology: visual and metrical descriptions. Most of the studies on term infants suffer from lack of reliability tests. The groove system was recognized as the distinctive feature of the infant palate. The shape of the palate of the term infant may vary considerably, both visually and metrically. Gender, race, mode of delivery, and nasal deformities were identified as causes contributing to altered palatal morphology. Until today, anatomical features of the newborn's palate are subject to a non-uniform nomenclature.

Conclusion: Today's knowledge of a newborn's 'normal' palatal morphology is based on non-standardized and limited methodologies for measuring a three-dimensional shape. This shortcoming increases bias and is the reason for contradictory research results, especially if pathologic conditions like syndromes or prematurity are involved. Adequate measurement techniques are needed and the 'normal palatal morphology' should be defined prior to new clinical studies on palatal development.

Figure 1

a-e Facial appearance (a, b), circular open bite (c) and palatal aspect (d) of a postnatally orotracheally intubated preterm infant in the initial phase of the dentition. Notice that the teeth of the child are 'in occlusion' on Figures a-c. The food intake – limited to soft or mashed foods due to the extreme dysgnathia – leads to marked frustration. The infant is teased because of its eating problems and the shape of its jaw and head. Radiography revealed premature ossification of the median suture (e).

Figure 2

The alveolar portion of the upper gum pad is separated from the palate by a groove. The alveolar portion itself is again divided into buccal and lingual portions which are also separated by grooves. The former is the larger, participates in the formation of the sheath and socket of the teeth, and is further divided by transverse grooves or sulci into segments corresponding to the developing tooth germs. For nomenclature of palatal structures, see Table 2 (Additional file 2). Interestingly, the 'Terminologia Anatomica' contains for discription of palatal structures only the following terms: Frenulum labii superioris (Frenulum of upper lip); Palatum (Palate); Palatum durum (Hard palate); Palatum molle, Velum palatinum (Soft palate); Raphe palati (Palatine raphe); Plicae palatinae transversae, Rugae palatinae (Transverse palatine folds; Palatine rugae); Papilla incisiva (Incisive papilla).