[Analysis of a change in the position of the hyoid bone when displacing the lower jaw in patients with dentofacial malformations].

OBJECTIVE: To estimate the magnitude of a change in the position of the hyoid bone when displacing the lower jaw during surgical treatment in patients with dentofacial abnormalities. MATERIAL AND METHODS: Fifty patients with dentofacial abnormalities (25 and 25 patients with distal and mesial occlusion, respectively) were examined and treated. All the patients underwent multislice spiral computed tomography before and 6 months after surgery. The authors developed linear quantities to analyze the position of the hyoid bone with respect to the skull base and cervical spine. The paired Wilcoxon signed-rank test was used. RESULTS: None of the examined groups was noted to have a statistically significant change in the distance between the basihyoid and the vertebral column, suggesting that the datum was moderately changed. No case of worse respiratory function was found. CONCLUSION: Our investigation has revealed that mandible displacement during orthognathic surgery causes no critcal change in the position of the hyoid bone and hence it has no significant impact on upper airway patency in this area.

[Role of multislice spiral computed tomography in the evaluation of changes in upper airway volume during surgical treatment in patients with dentomaxillary abnormalities].

OBJECTIVE: To assess the role of multislice spiral computed tomography in the calculation of upper airway volume and its change in patients with different types of dentomaxillary abnormalities after orthognathic surgery. MATERIAL AND METHODS: Twenty-five patients with dentomaxillary abnormalities (19 and 6 patients with Classes III and II dentomaxillary abnormalities, respectively) were examined. All the patients underwent two-jaw operations. Facial skeleton computed tomography was performed before treatment initiation and 6 months after surgery. The DICOM data were loaded in Dolphin Imaging 11.5 and a special program package was applied to calculate the volume of air space in the upper airway. The hard tissue and soft tissue points used to construct the planes setting the detection limits of air space in the upper airway were determined. RESULTS: After surgery, the patients with Class II dentomaxillary abnormalities display unilateral changes in our measured upper airway values (by increasing or reducing the air space); the majority of cases exhibiting higher values. Half of the patients with Class III had unilateral hanges, the increase or reduction in air space values varying in approximately equal proportions. CONCLUSION: Computed tomography permits the calculation of upper airway volumes before and after orthognathic treatment in patients with dentomaxillary abnormalities, which is in its turn of significant scientific and practical interest.