Age-dependent effects on palate volume and morphology during orthodontic RME treatment

Abstract

Objectives: Rapid maxillary expansion (RME) shows different age-dependent effects. It has been shown that RME leads to a parallel expansion prior to the age of 10, while later and especially from the age of 12, a V-shaped expansion happens (transverse, anterior > posterior; horizontal, inferior > superior). However, it is not clear to what extent these effects influence palatal volume and morphology and eventually maxillary functional space. The aim of the present study was to examine possible age-related effects of treatment with a dental anchored RME appliance upon volume and width/height ratio of the anterior and posterior palate.

Materials and methods: Sixty children and adolescents with documented treatment histories after RME were divided into three equal groups according to age at treatment begin (PG 1, < 10 years, n=20; PG 2, 10 ≤ 12 years, n=20; PG 3, > 12 years, n=20). Maxillary dental casts before and after therapy were digitised. Changes in palatal volume were determined using 3D analyses.

Results: In all patients, the palatal volume increases significantly after RME. Older patients experienced smaller increases in total and posterior volume in absolute and percentage terms. The anterior palate volume increases are almost equal in all patients. Since palatal width increases more markedly than palatal height, the width/height ratio always increases. Except for the posterior region in PG 3, its increase is significant in all groups, both anteriorly and posteriorly. After successful RME, the palatal morphology appears normal anteriorly in PG 1, PG 2 and PG 3 and rather steep posteriorly in PG 3.

Conclusions: RME treatment with identical force application causes different, age-dependent effects upon palate volume and morphology. Width changes have a greater influence on palate volume than height changes.

Clinical relevance: It is preferable to use an RME prior to the age of 10 if homogeneous changes of the anterior and posterior palate regarding maxillary symmetry and functional space are desired.

Keywords: Cast analysis; Palate morphology; Palate ratio; Palate volume; Rapid maxillary expansion (RME).

Fig. 1

a–c (left to right) Treatment examples from PG 1 (a), PG 2 (b) and PG 3 (c): model superimposition at T₁ (grey) before and T₂ (green) after palatal expansion

Fig. 2

a and b (left to right) Patient example with RME before (a) and after hyrax screw activation (b). The appliance is anchored anteriorly with temporary attachment including two occlusal rests on the first deciduous molars and posteriorly with two conventional bands on the first permanent molars

Fig. 3

a–c (left to right) Perpendicular to the raphe median line, a division into an anterior and posterior palatal region is created by a division at the level of the third pair of palatal rugae (a). Crosshatched areas: determination of total (b) and anterior palatal volume (c). The posterior palatal volume was calculated by subtracting the anterior volume from the total volume

Fig. 4

a and b (left to right) Calculation of anterior and posterior palatal quotients: the gingival width was measured at the level of the landmarks according to Pont [28] anteriorly at the first deciduous molars or premolars (a) and posteriorly at the first permanent molars (b). The median height was measured perpendicularly between the connecting line and the raphe median line anteriorly (a) and posteriorly (b)

Fig. 5

Graphical representation of the a/p ratio T₂–T₁ for palatal volume (RV, grey), palatal width (RW, orange) and palatal height (RH, blue) changes