Heritability of the pharyngeal airway volume and dimensions as assessed from siblings with overt malocclusions

Comparative Analysis of Pharyngeal Airway Changes Following All Four Versus All Five Premolar Extractions in Orthodontic Treatments: A Cephalometric Study

BACKGROUND

Orthodontic treatment, particularly involving premolar extractions, has been a subject of ongoing debate within the orthodontic community. The impact of such interventions on the pharyngeal airway, a critical component of the respiratory system, remains a topic of exploration.

OBJECTIVE

This retrospective cephalometric study aims to investigate changes in pharyngeal airway dimensions following orthodontic treatment involving either all four or all five premolar extractions.

METHODS

A sample of 68 participants, extracted from orthodontic records, underwent cephalometric analysis to quantify changes in pharyngeal airway dimensions. The study compared two groups: those treated with all four premolar extractions (n=34) and those treated with all five premolar extractions (n=34). Cephalometric radiographs taken before and after treatment were analyzed, focusing on airway width, length, and volume.

RESULTS

Preliminary findings indicate significant changes in airway dimensions within each group. In the all four premolar extraction group, there was a statistically significant decrease in airway width (p=0.02) and volume (p=0.04). Similarly, the all five premolar extraction group exhibited significant reductions in airway width (p=0.03) and volume (p=0.02). However, the between-group comparisons revealed no significant differences in changes between the two groups.

CONCLUSION

This study sheds light on the intricate relationship between orthodontic interventions, specifically premolar extractions, and changes in pharyngeal airway dimensions. While significant changes were observed within each group, the lack of significant differences between the all four and all five premolar extraction groups raises intriguing questions about the specific impact of premolar extraction patterns on the upper airway.

Heritability Analysis in Twins Indicates a Genetic Basis for Velopharyngeal Morphology

The velopharyngeal mechanism is comprised of several muscular components that act in a coordinated manner to control airflow through the nose and mouth. Proper velopharyngeal function is essential for normal speech, swallowing, and breathing. The genetic basis of normal-range velopharyngeal morphology is poorly understood. The purpose of this study was to estimate the heritability of velopharyngeal dimensions.

We measured five velopharyngeal variables (velar length, velar thickness, effective velar length, levator muscle length and pharyngeal depth) from MRIs of 155 monozygotic and 208 dizygotic twin pairs and then calculated heritability for these traits using a structural equation modeling approach.

The heritability estimates were statistically significant (95% confidence intervals excluded zero) and ranged from 0.19 to 0.46. There was also evidence of significant genetic correlations between pairs of traits, pointing to the influence of common genetic effects.

These results indicate that genetic factors influence variation in clinically relevant velopharyngeal structures.