3-Dimensional Laser Surface Scanner study in patients ...



3D Measure of the Airway Space in Patients with Skeletal Malocclusion.

Patricia V. M. Alves, DDS, MS, Ana Maria Bolognese, DDS, MS, Linping Zhao, PhD, Pravin K. Patel, MD

INTRODUCTION: The posterior airway space (PAS) is delimited by hard and soft tissues. In patients with severe hypoplasia of the middle and lower third of the face, a decrease in volume of the PAS may be present, producing a polysyndromic condition that ranges from snoring to obstructive sleep apnea syndrome (OSAS). Technological progress, as three-dimensional cephalometry using standardized CT scanning protocols with the advantage that all measurements are life-sized scale (1:1), makes possible to produce accurate 3D anatomical virtual model. The aim of this study is to define PAS morphology and variations by 3D computerized tomography cephalometric study in patients affected by skeletal malocclusion.

METHOD: Thirty patients affected by skeletal Class II or Class III malocclusion underwent orthodontic and orthognathic surgery treatment were analyzed. To evaluate posterior airway space morphology and it relation with surrounding tissues, 3D cephalometric analyses were performed by computerized tomography. The data format of the CT scan was standardized as a Digital Imaging and Communications in Medicine (DICOM) file. The next step is the segmentation of anatomical structures, which is the process of outlining the shape of structures visible in the cross-sections of a volumetric data set. Based upon the Hounsfield scale, hard and soft tissue can be separated, and the airway can be defined and calculated (Figures 1-2).

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Figure 1. Presurgical three-dimensional CT scan demonstrates hard tissues and airway space in patient with skeletal Class II.

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Figure 2. Presurgical three-dimensional CT scan demonstrates hard tissues and airway space in patient with skeletal Class III.

RESULTS: This study showed significant differences in tongue and soft palate position, vertical length of oropharynx, anteroposterior dimensions of the upper airway, nasopharynx and oropharynx cross-sectional area between groups (Figures 3-4).

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Figure 3. Airway space of the skeletal pattern of Class II. The retropalatal (RP) area is short comparing with the retroglossal (RG) area, which is narrow and long.

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Figure43. Airway space of the skeletal pattern of Class III. The retropalatal (RP) area is longer than the retroglossal (RG) area.

CONCLUSION: 3D cephalometric studies of hard tissue and posterior airway space should be performed in all patients affected by maxillomandibular malformation. This approach may provide data for the diagnosis of respiratory pathologies that vary from snoring to obstructive sleep apnea syndrome.

REFERENCES

1. Hajeer MJ, Ayoub AF, Millett DT, Bock M, Siebert, JP. Three-dimensional imaging in orthodonthic surgery: the clinical application of a new method. Int J Adult Orthod Surg. 2002; 17:318-30.

2. Ferrario VF, Sforza C, Schmitz JH, Santoro F. Three-dimensional facial morphometric assessment of soft-tissue changes after orthognathic surgery. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 1999;88:549-556.

3. Chen F, Terada K, Hua Y, Saito I. Effects of bimaxillary surgery and mandibular setback surgery on pharyngeal airway measurements in patients with Class III skeletal deformities. Am J Orthod Dentofacial Orthop. 2007;131:372-7.

4. de Freitas MR, Alcazar NM, Janson G, de Freitas KM, Henriques JF.Upper and lower pharyngeal airways in subjects with Class I and Class II malocclusions and different growth patterns. Am J Orthod Dentofacial Orthop. 2006;130:742-5.

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