MR imaging in evaluation of the temporomandibular lateral disc displacement in patients with posterior occlusion

Background: The aim of this work was to assess the usefulness of MR imaging in the evaluation of temporomandibular lateral disc displacement in patients with posterior occlusion and the significance of the results of MRI in the diagnosis and treatment of posterior occlusion. Material/Methods: Imaging evaluation was performed to 80 temporomandibular joints in 40 patients with posterior occlusion, of both sexes, at the age of 16-35, prior to orthodontic treatment. The imaging technique used for the evaluation of temporomandibular joints was magnetic resonance using the Signa Horizon 1.5 T System (GEMS) during rest occlusion. The evaluation was focused on bony structures of the joint and its posterior ligament. The type of joint was defined as intermediate in case of the articular tuberculum of a semicircular shape, shallow - in case of horizontally elongated ellipse, and deep - in case of vertically elongated ellipse. The symmetry of the articular space as well as the alignment of the articular disc in the frontal plane was also evaluated. The obtained data were presented in form of figures and graphs and analysed using the statistics software - BMDP New System 2.0. Results: In patients with posterior occlusion, the so-called intermediate type of temporomandibular joint was found to be the most common, whereas the symmetrical articular space occurred in 33.7% of cases. The rate of narrowed retrodiscal region was 61.2%, which was a statistically significant difference in comparison with the control group. The assessment of position of the disc in the frontal plane during occlusion revealed 12.6% of medial displacement and 6.2% of lateral displacement. Statistically significant differences between the study group and the control group were found concerning the disc position during occlusion assessed in the frontal plane (χ2=9.564; p=0.008). Statistically significant differences were confirmed concerning the width and symmetry of the articular space between the two groups - the persons with posterior occlusion and the control group (χ2=24.174; p=0.0001). In persons with posterior occlusion no significant correlation was found between the type of the joint and the position of the articular disc during occlusion in the frontal plane, that is the lateral and medial displacement (χ2=2.529; p=0.640). Correlation was found between the type of the joint and its symmetry, narrowed or widened articular space in the retrodiscal region (χ2=15.54; p<0.004). Conclusions: Diagnostic efficacy of the magnetic resonance imaging was found in the evaluation of temporomandibular joints in case of posterior occlusion. Based on the obtained results we believe that in MR of occlusion defects T2-weighted sequences can be excluded, as the application of only T1- and PD-weighted sequences is sufficient

Zastosowanie spiralnej tomografii komputerowej w ocenie relacji zatrzymanych kłów górnych z korzeniami sąsiadujących zębów siecznych

Background: The relations of the crowns of impacted maxillary canines and the roots of adjacent incisors are difficult to evaluate on conventional radiographs due to superimposition of shadows of these structures. The aim of this study was to analyse the relations between the crowns of impacted canines and the roots of adjacent incisors with the use of computed tomography. Material/Methods: The study involved a group of 65 patients suspicious for an impacted maxillary permanent canine. All the patients underwent pantomography. In 44 individuals in the age of 13-31 years (mean age 17.1±4.5) the examination revealed shadows of the impacted crowns superimposed on the roots of incisors. These patients were subjected to CT. On the basis of those CT examinations (including multiplanar and three-dimensional reconstructions) we defined the location of the impacted canines as buccal, palatal and horizontal. Likewise, the relations between the crowns of impacted canines and the roots of lateral or/and central incisors were studied. Results: From among 54 impacted maxillary canines, 41 (75.9%) were located palatally, 10 (18.5%) buccally, and 3 (5.6%) horizontally. In 14 cases (29.5%), the impacted canine remained in various kind of contact with both adjacent incisors. In addition to those aforementioned 14 cases, the impacted maxillary canine remained in contact with adjacent root of the lateral incisor in 34 cases (in total: 48 cases of contact). We found 17 cases (35.4%) of adherence without features of root resorption and 31 cases (64.4%) of resorption. Among the cases of resorption, there were 18 instances of deep resorption (58.1%) and 13 instances of light resorption (41.9%). There were also 18 cases (33.3%) of contact between the impacted canine and the root of the central incisor, including 10 instances (55.6%) of adjacency without root resorption and 8 cases (44.4%) of resorption. Conclusions: Computed tomography allows for a precise localisation of the impacted teeth and evaluation of their influence on the adjacent anatomical structures