A retrospective cephalometric study on pharyngeal airway space changes after rapid palatal expansion and Herbst appliance with or without skeletal anchorage

Background

The aim of this study is to investigate the pharyngeal airway space changes in patients treated with rapid palatal expansion (RPE) and Herbst appliance with or without skeletal anchorage.

Methods

A 40-patient study group treated with the Herbst RME combination was included; moreover, a comparison between two subgroups based on whether miniscrews were used was evaluated. A subgroup 1 included 20 patients who were treated with RPE and an acrylic splint Herbst with miniscrews, and subgroup 2 included 20 patients who were treated with RPE and an acrylic splint Herbst. A cephalometric analysis was performed before (T1) and after (T2) treatment. The skeletal parameters of the sagittal occlusion analysis of Pancherz were utilized together with some extra measurements to evaluate the airways.

Results

An increased nasopharyngeal airway space was observed in group 1 (p < 0.05) from T1 to T2. Furthermore, the increase in nasopharyngeal airway space was significantly higher in subgroup 1 (p < 0.05) in comparison to the subgroup 2. Oropharyngeal (OA) and laryngopharyngeal (LA) dimensions were significantly increased in the subgroup 1 at the end of the treatment. In the subgroup 1, a significant decrease in SNA, a significant increase in SNB, and a significant decrease in ANB were observed from T1 to T2. In the subgroup 2, the treatment resulted in a significant decrease in ANB. In both groups, Pogonion increased significantly from T1 to T2.

Conclusions

The results suggest that the RPE and the Herbst appliance allow a slight improvement of the sagittal dimensions of the airways. The oropharyngeal dimension increased significantly more in the skeletal anchorage group.

A novel protocol for three-dimensional reconstruction of pharyngeal airway on computed tomography

Three-dimensional measurement of the pharyngeal airway has been widely used, but the three-dimensional reconstruction of pharyngeal airway has been performed in various ways, especially during the anterior boundary demarcation of the nasopharyngeal airway and oropharyngeal airway. This would inevitably affect the measurement and lead to noncomparison between different studies. Our study provided a novel method for anterior boundary demarcation of pharyngeal airway that defined the anterior boundary of nasopharyngeal airway as the "choana" according to the anatomical definition and defined the anterior boundary of oropharyngeal airway as a plane perpendicular to the long axis of soft palate and through the intersections of the lateral space and inferior space to soft palate according to the physiologic characteristics of soft palate. By 2-step segmentation, a three-dimensional image of pharyngeal airway was eventually reconstructed.Ten computed tomographic scans of pharyngeal airway were included for the anterior boundary demarcation and three-dimensional reconstruction by a medical imaging software (Surgicase 5.0; Materialise Interactive Medical Image Control System, Leuven, Belgium), with the volume and surface area being calculated. By using intraclass correlation coefficient, the reliability between intra- and interobservers of this method was well tested.The method established in this study for anterior boundary demarcation and three-dimensional reconstruction of pharyngeal airway is highly reliable and could more veritably reflect the intrinsic anatomical characteristics of the pharyngeal airway.

A comparative study of the pharyngeal airway space, measured with cone beam computed tomography, between patients with different craniofacial morphologies

PURPOSE

The present study aims to determine any existing association between airway dimensions, measured with cone beam computed tomography (CBCT), and the different patient craniofacial morphologies.

MATERIAL AND METHODS

Sixty CBCT (Dental Picasso Master 3D) images, from patients treated at the Orthodontics Master at Valencia University were selected. The program InVivoDental 5.1 was used to visualize sections, analyze three-dimensional images, and perform airway measurements in the three planes of the space. Intra- and interobserver error methods were recorded. After that, measurements at three different levels of the airway (upper, medium, lower) were taken, in both the anteroposterior and transversal directions of the airway space. The area (mm(2)) of the airway space at the three levels was also measured.

RESULTS

In the anteroposterior airway measurements, there were differences between the measurements by level. The magnitude of these differences depended on the skeletal pattern of the individual. In the transversal airway measurements and in the area airway measurements, there were no differences according to the skeletal pattern. However, in the transversal direction, measurements in the lower level were significantly higher than in the superior level in all cases. When measuring the area, significantly higher measurements in the upper level were recorded. The homogeneity between medium and lower levels decreased gradually from class I to class III subjects.

CONCLUSIONS

No statistically significant results were observed that related the anteroposterior and vertical skeletal craniofacial morphology with airway dimensions, although some specific associations have been detected for certain airway levels or for pattern combinations.

Three-dimensional analysis of pharyngeal airway in preadolescent children with different anteroposterior skeletal patterns

INTRODUCTION

In growing patients with skeletal discrepancies, early diagnosis, evidence-based explanations of etiology, and assessment of functional factors can be vital for the restoration of normal craniofacial growth and the stability of the treatment results. The aims of our study were to compare the 3-dimensional pharyngeal airway volumes in healthy children with a retrognathic mandible and those with normal craniofacial growth, and to investigate possible significant relationships and correlations among the studied cephalometric variables and the airway morphology in these children.

METHODS

Three-dimensional airway volume and cross-sectional areas of 27 healthy children (12 boys, 15 girls; mean age, 11 years) were measured by using cone-beam computed tomography volume scans, and 2-dimensional lateral cephalograms were created and analyzed. The subjects were divided into 2 groups based on their ANB angles (group I: 2 degrees < or = ANB < or = 5 degrees ; group II: ANB >5 degrees ), and cephalometric variables, airway volumes, and cross-sectional measurements were compared.

RESULTS

There were statistically significant differences in the following parameters: height of the posterior nasal plane (P <0.05), pogonion to nasion perpendicular distance (P <0.01), ANB angle (P <0.01), mandibular body length (P <0.01), facial convexity (P <0.01), and total airway volume (P <0.05). No statistically significant differences between the 2 groups were found in the cross-sectional area and the volumetric measurements of the various sections of the airway except for total airway volume, which had larger values in group I (P <0.05).

CONCLUSIONS

The mean total airway volume, extending from the anterior nasal cavity and the nasopharynx to the epiglottis, in retrognathic patients was significantly smaller than that of patients with a normal anteroposterior skeletal relationship. On the other hand, differences in volume measurements of the 4 subregions of the airway were not statistically significant between the 2 groups.

Is the tongue position influenced by the palatal vault dimensions?

The influence of the palatal vault dimensions on tongue position is here studied through evaluation of the in-mouth air cavity (IMAC) volume when the mandible is in maximal intercuspal position. A sample of 35 women (mean age 21.2 +/- 1.0) and 15 men (mean age 22.1 +/- 0.9) was selected. The sagittal cross-section area of the IMAC, which is modulated by the tongue position, was measured on lateral cephalograms. Dental casts were used to measure the palatal vault volume, which was defined by the occlusal plane, the hard palate and the posterior face of the second molars. Palatal vault volume allowed deduction of the IMAC volume through a rule of three procedure relating volume to area ratios. No IMAC could be calculated from cephalograms of 10 subjects who had the tongue stuck to the palate. For the 40 other subjects, the IMAC volume was 8.9 +/- 4.8 mL. It was 2 mL larger in men (n = 14) than in women (n = 26) and was the largest in skeletal Class III and the smallest in skeletal Class II (P > 0.05). IMAC volume was strongly correlated with palatal vault height but neither with palatal width nor length. It was thus assumed that the height of the palatal vault could influence the most observed position of the tongue but this does not exclude a possible growth influence of the tongue on its surrounding skeletal structures.