Temporomandibular Disk Dislocation Impacts the Stomatognathic System: Comparative Study Based on Biexponential Quantitative T2 Maps

Abstract

In this study, we aimed to assess the potential impact of temporomandibular disk displacement on anatomical structures of the stomatognathic system using biexponential T2 magnetic resonance imaging (MRI) maps. Fifty separate MRI scans of the temporomandibular joints (TMJ) of 25 patients were acquired with eight echo times. Biexponential T2 maps were created by weighted reconstruction based on Powell's conjugate direction method and divided into two groups: the TMJ without (32 images) and with (18 images) disk displacement. The disk, retrodiscal tissue, condylar bone marrow, masseter muscle, lateral and medial pterygoid muscles and dental pulp of the first and second molars were manually segmented twice. The intrarater reliability was assessed. The averages and standard deviations of the T2 times and fractions of each segmented region for each group were calculated and analysed with multiple Student's t-tests. Significant differences between groups were observed in the retrodiscal tissue, medial pterygoid muscle and bone marrow. The pulp short T2 component showed a trend toward statistical significance. The segmentation reliability was excellent (93.6%). The relationship between disk displacement and quantitative MRI features of stomatognathic structures can be useful in the combined treatment of articular disk displacement, pterygoid muscle tension and occlusive reconstruction.

Keywords: T2 maps; biexponential analysis; quantitative MRI; temporomandibular disk.

Figure 1

Samples of stomatognathic anatomical structure segmentation for the (a) disk; (b) retrodiscal tissue; (c) bone marrow of the condyloid process; (d) pulp; (e) m. masseter; (f) m. pterygoideus lateralis; and (g) m. pterygoideus medialis.

Figure 2

Short T2 maps obtained for the (a) disk; (b) retrodiscal tissue; (c) bone marrow of the condyloid process; (d) pulp; (e) m. masseter; (f) m. pterygoideus lateralis; and (g) m. pterygoideus medialis. (h) Color scale showing the reference T2 times in seconds.

Figure 3

Long T2 maps obtained for the (a) disk; (b) retrodiscal tissue; (c) bone marrow of the condyloid process; (d) pulp; (e) m. masseter; (f) m. pterygoideus lateralis; and (g) m. pterygoideus medialis. (h) Color scale showing the reference T2 times in seconds.

Figure 4

Short fraction components for the (a) disk; (b) retrodiscal tissue; (c) bone marrow of the condyloid process; (d) pulp; (e) m. masseter; (f) m. pterygoideus lateralis; and (g) m. pterygoideus medialis. (h) Color scale showing the reference values.

Figure 5

Long fraction components for the (a) disk; (b) retrodiscal tissue; (c) bone marrow of the condyloid process; (d) pulp; (e) m. masseter; (f) m. pterygoideus lateralis; and (g) m. pterygoideus medialis. (h) Color scale showing the reference values.

Figure 6

Comparison of mono- (dashed line) and bicomponent (solid line) fitting curves for eight exemplary echo time points (squares) showing a higher error for the monoexponential fit.