Midpalatal suture maturation: classification method for individual assessment before rapid maxillary expansion

Abstract

Introduction: In this study, we present a novel classification method for individual assessment of midpalatal suture morphology.

Methods: Cone-beam computed tomography images from 140 subjects (ages, 5.6-58.4 years) were examined to define the radiographic stages of midpalatal suture maturation. Five stages of maturation of the midpalatal suture were identified and defined: stage A, straight high-density sutural line, with no or little interdigitation; stage B, scalloped appearance of the high-density sutural line; stage C, 2 parallel, scalloped, high-density lines that were close to each other, separated in some areas by small low-density spaces; stage D, fusion completed in the palatine bone, with no evidence of a suture; and stage E, fusion anteriorly in the maxilla. Intraexaminer and interexaminer agreements were evaluated by weighted kappa tests.

Results: Stages A and B typically were observed up to 13 years of age, whereas stage C was noted primarily from 11 to 17 years but occasionally in younger and older age groups. Fusion of the palatine (stage D) and maxillary (stage E) regions of the midpalatal suture was completed after 11 years only in girls. From 14 to 17 years, 3 of 13 (23%) boys showed fusion only in the palatine bone (stage D).

Conclusions: This new classification method has the potential to avoid the side effects of rapid maxillary expansion failure or unnecessary surgically assisted rapid maxillary expansion for late adolescents and young adults.

Fig 1

Standardization of head position in the A, axial; B, sagittal, and C, coronal planes to allow consistent assessments of the midpalatal suture. Note that in B, the sagittal view, the orange line that indicates the position of the axial plane view is positioned through the center of the superoinferior dimension of the hard palate (Invivo5).

Fig 2

For subjects with a curved palate, 2 axial plane images through the posterior and anterior regions were used. The central cross-sectional slices along the axis of the palate in the anterior and posterior regions were evaluated.

Fig 3

For patients with a thick palate, the 2 most central axial slices were analyzed.

Fig 4

A, Schematic drawing of the maturation stages observed in the midpalatal suture. It is a simplification of the sutural morphology and should not be used for diagnosis. Sutural morphology can vary between stages, and diagnostic criteria are based on the decision tree in B and the definitions of the 5 stages. B, Decision tree for classification of the maturation stages of the midpalatal suture.

Fig 5

Stage A of maturation of the midpalatal suture is seen in this patient as a relatively straight high-density line at the midline.

Fig 6

A, Stage B is observed as 1 scalloped, high-density line at the midline. B, Stage B in another subject is characterized by a scalloped high-density line in some areas and, in other areas, as 2 parallel, scalloped, high-density lines close to each other and separated by small low-density spaces.

Fig 7

Stage C is visualized as 2 parallel, scalloped, high-density lines that are close to each other and separated in some areas by small low-density spaces. The suture can be arranged in either A, a straight or B, an irregular pattern.

Fig 8

Stage D is visualized as 2 scalloped, high-density lines at the midline on the maxillary portion of the palate. The midpalatal suture cannot be visualized in palatine bone, and the density of the parasutural palatine bone is higher compared with the parasutural maxillary bone.

Fig 9

At stage E, sutural fusion has occurred in the maxilla. The midpalatal suture cannot be identified, and the parasutural bone density is the same as in other regions of the palate.

Fig 10

At the axial cross-sectional slice closer to the oral cavity indicated by the orange horizontal line in the sagittal view (A), the midpalatal suture may appear to have a low-density space at the midline (B). However, at the central axial cross-sectional slice indicated by the orange horizontal line in the sagittal view (C), it can be observed that the midpalatal suture is fused (D).

Fig 11

A patient whose palate was thinner (superoinferiorly) in the maxillary region, where the midpalatal suture was fused earlier.