REFERENCES

INTRODUCTIONThe temporomandibular disorders (TMD) are characterized by a painful musculoskeletal disorder that effects the masticatory muscles, temporomandibular joints (TMJ) and anatomical structures of the stomatognathic system (1). The cone beam computed tomography (CBCT) allows visualization of bone structures in three dimensions, enabling accurate evaluation of bone changes in temporomandibular joint (TMJ) and joint dynamics (2.3). This study aims to describe the use of post-processing tomographic image software for assessment of temporomandibular joint.

TECHNICAL DESCRIPTIONA female patient was referred to a private radiology clinic to perform a CBCT in order to assess the TMJ. The ICat Classic system (International Imaging Sciences, Hatfield, PA, USA) was used at 120 kV, 3 mA and a scan time of 20 seconds. The slice thickness was 0.3 mm (isometric voxel). The field of view was 6 cm. In the CBCT images it is possible to visualize the joint space narrowing on the left TMJ and the hipermobility of the mandibular condyle. In addition, it is possible to view the flattening of the mandibular condyles and osteophyte on right mandibular condyle (figure 1).

USE OF POST-PROCESSING TOMOGRAPHIC IMAGE SOFTWARE FOR ASSESSMENT OF TEMPOROMANDIBULAR

JOINT: A TECHNICAL DESCRIPTION

Eduardo Murad Villoria, Kyria Spyro Spyrides, Aurelino Machado Lima Guedes, Felipe de Assis Ribeiro Carvalho, Alexandre Perez Marques

Figure 1. Parasagital views of TMJ (closed mouth – A and D / open mouth – B and C). Coronal (E) and sagittal (F) views demonstrating the osteophyte on right mandibular condyle (arrow).

To allow the assessment of the temporomandibular joint by means of post-processing tomographic image software, the volume initially acquired and stored in .XSTD (Xoran) format was exported to DICOM (Digital Imaging and Communication in Medicine) format. Then, the DICOM files were imported into ITK-SNAP 3.0 (free and open source software, www.itksnap.org) to segment the TMJ and others anatomic structures, and to construct virtual 3D models (figure 2).

Figure 3. Virtual 3D models aligned and overlapped. Right mandibular condyle (A), left mandibular condyle (B), closed mouth (red) and open mouth (blue). Frontal (C) and upper (D) views of mandibular condyles. Arrow indicating the osteophyte.

Following this, the virtual 3D models were exported to the .STL (STerioLitography) format and imported into the MeshLab 64-Bit v.1.3.3 (free and open source software, www.meshlab.sourceforge.net) to allow the alignment and overlap of these 3D models (figure 3).

The virtual 3D models were then saved in .STL format and imported into the 3DMeshMetric v.1.4.3 (free and open source software, www.nitrc.org) to perform the quantitative assessment of condylar mobility by color maps (figures 4 and 5).

Figure 4. Quantitative assessment by color maps and “Point Value” tool. Upper view of mandibular condyles (A and B). Closed mouth (green) and open mouth (colorful). A greater mobility of left mandibular condyle (10.6 mm) than right condyle (8.1mm).

Figure 5. Quantitative assessment by color maps and “Point Value” tool. Lateral view of righ (A) and left mandibular condyles (B). Closed mouth (green), open mouth (colorful) and articular eminence (purple). Right mandibular condyle is positioned superiorly. A greater distance from left mandibular condyle to articular eminence (5.1 mm) than the right side (4.5 mm).

Figure 2: Segmentation of mandibular condyle and construction of 3D virtual model by means of ITK-SNAP software.

CONCLUSIONThe software described in this work, combined with the detailed study of CBCT images, which presented in a clear and informative way, provides an important information for the assessment of the temporomandibular joint and diagnosis of temporomandibular disorder.

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Diagnosis and Surgery Department - Oral Radiology - School of Dentistry - State University of Rio de Janeiro (UERJ)Dentistry Department - Pontificial Catholic University of Minas Gerais (PUC-MG)

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