Search

Purpose: This study aimed to develop and evaluate experimentally an implant-based registration method for measuring three-dimensional (3D) kinematics of the mandible and dental implants in the mandible based on dental cone beam computed tomography (CBCT), modified to include fluoroscopic function. Materials and Methods: The proposed implant-based registration method was based on the registration of CBCT data of implants/bones with single-plane fluoroscopy images. Seven registration conditions that included one to three implants were evaluated experimentally for their performance in a cadaveric porcine head model. Results: The implant-based registration method was shown to have measurement errors (SD) of less than –0.2 (0.3) mm, 1.1 (2.2) mm, and 0.7 degrees (1.3 degrees) for the in-plane translation, out-of-plane translation, and all angular components, respectively, regardless of the number of implants used. The corresponding errors were reduced to less than –0.1 (0.1) mm, –0.3 (1.7) mm, and 0.5 degree (0.4 degree) when three implants were used. Conclusion: An implant-based registration method was developed to measure the 3D kinematics of the mandible/implants. With its high accuracy and reliability, the new method will be useful for measuring the 3D motion of the bones/implants for relevant applications. [ABSTRACT FROM AUTHOR]

Aim: To explore the relationship between general joint hypermobility (GJH) and displacement of the temporomandibular joint (TMJ) disc as evident from magnetic resonance imaging (MRI). Methods: Fifth finger extension, thumb apposition, elbow extension, knee extension, trunk flexion, and ankle dorsiflexion were measured in 66 young female patients with MRI-evident TMJ internal derangement (ID) and in 30 age-matched female controls. The Beighton score of each subject was measured quantitatively. The possible association between TMJ ID and mobility of a single joint or index of GJH, ie, the Beighton score, were assessed with one-way ANOVA with post-hoc Bonferroni and chi-square test, respectively. Correlations of the mobility of every measured joint were also explored. Results: Very few of the TMJ ID patients and control subjects were diagnosed with GJH according to the Beighton score. The Beighton score did not differentiate between subjects with and without TMJ ID. Subjects with TMJ ID, especially patients with MRI-evident disc displacement without reduction, seemed to have a stiffer trunk than controls, but this may not be of clinical relevance. The mobilities of paired joints were significantly correlated; however, the mobilities of different anatomical joints seemed to be independent. Conclusion: Based on the Beighton score, GJH does not seem to be a reliable indicator of the presence of TMJ ID. [ABSTRACT FROM AUTHOR]

Purpose: This study investigated whether the presence of tooth wear in young adults can help to discriminate patients with sleep bruxism (SB) from control subjects. Materials and Methods: The tooth wear clinical scores and frequency of sleep masseter electromyographic activity of 130 subjects (26.6 ± 0.5 years) were compared in this case-control study. Tooth wear scores (collected during clinical examination) for the incisors, canines, and molars were pooled or analyzed separately for statistics. Sleep bruxers (SBrs) were divided into two subgroups according to moderate to high (M-H-SBr; n = 59) and low (L-SBr; n = 48) frequency of masseter muscle contractions. Control subjects (n = 23) had no history of tooth grinding. The sensitivity and specificity of tooth wear versus SB diagnosis, as well as positive and negative predictive values (PPV and NPV), were calculated. One-way analysis of variance and the Mann-Whitey U test were used to compare groups. Results: Both SBr subgroups showed significantly higher tooth wear scores than the control group for both pooled and separated scores (P < .001). No difference was observed between M-H-SBr and L-SBr frequency groups (P = .14). The pooled sum of tooth wear scores discriminates SBrs from controls (sensitivity = 94%, specificity = 87%). The tooth wear PPV for SB detection was modest (26% to 71%) but the NPV to exclude controls was high (94% to 99%). Conclusions: Although the presence of tooth wear discriminates SBrs with a current history of tooth grinding from nonbruxers in young adults, its diagnostic value is modest. Moreover, tooth wear does not help to discriminate the severity of SB. Caution is therefore mandatory for clinicians using tooth wear as an outcome for SB diagnosis. [ABSTRACT FROM AUTHOR]

Aims: To analyze the bone mineral density (BMD) in a group of young female patients with a disc displacement in at least 1 temporomandibular joint (TMJ) as well as in a group of age-matched young females with a normal condyle-disc relationship. Methods: Fifty-six young female patients with anterior disc displacement based on magnetic resonance imaging (MRI) and 40 age- and gender-matched controls with asymptomatic TMJs were recruited for this study. Subjects between 18 and 30 years were recruited. Based on the MRI findings, 10 of the 40 subjects in the control group also had anterior disc displacement. In all, 16 subjects had an anterior disc displacement with reduction (DDwR), 50 had an anterior disc displacement without reduction (DDw/oR), and 30 had a normal condyle-disc relationship. BMD was measured in the lumbar area by means of dual-energy x-ray absorptiometry. The relationship between the 3 types of condyle-disc relationship and BMD was then analyzed. Results: Patients with a DDw/oR had a significantly lower mean BMD value in the lumbar area than the subjects with a normal condyle-disc relationship (P < .05, analysis of variance, post-hoc with Bonferroni test). Twenty-two (44%) of 50 patients with DDw/oR had osteopenia. Conclusion: Low BMD is often associated with DDw/oR in young Taiwanese female patients. [ABSTRACT FROM AUTHOR]

Aims: To compare the results of 3 methods of recognizing internal derangements with a clicking sound on condylar movement: 2 function-based methods (clinical examination and condylar movement recording) and 1 anatomy-based method (magnetic resonance imaging [MRI]). Methods: For the recognition of an anterior or posterior disc displacement with reduction and of hypermobility within the temporomandibular joint (TMJ), 42 participants underwent a clinical examination, an opto-electronic movement recording, and an MRI scan. The examinations were executed in a single-blind design, with different experienced examiners for each technique. In addition, for 10 randomly chosen participants, the condylar movement recordings and the MRI scans were carried out twice. Without the examiners' knowledge, these second recordings were added to the other data. Results: Intraobserver reliability for the recognition of internal derangements was excellent for condylar movement recording (κ = 0.86) and fair to good for MRI (κ = 0.73). Intermethod agreement was fair to good (κ = 0.59) between the 2 function-based techniques. However, intermethod agreement between the anatomy-based MRI technique and either of the 2 function-based techniques was poor (for condylar movement recording, κ = 0.15; and for clinical examination, κ = 0.12). Conclusion: There is a great discrepancy between the diagnoses for internal derangements based upon anatomical TMJ characteristics and those based on functional TMJ characteristics. For a function-based diagnosis, there is probably no need for the sophisticated technique of condylar movement recording, since that method shows fair to good agreement with a carefully performed clinical examination. [ABSTRACT FROM AUTHOR]

Aims: Temporomandibular joint (TMJ) discs displaced simultaneously, dorsoventrally, and mediolaterally are assumed to be rotated. However, a pilot study performed with individualized oblique-axial scans on supposedly rotated discs did not show disc rotation consistently. The aim of this study was the quantitative evaluation of disc rotation on a larger sample size, assessing the mediolateral disc geometry and position by the use of a reference system determined by the condylar long axis. Methods: Eighty-five TMJs from 50 subjects were analyzed. One series of sagittal and 1 of 14 individualized oblique-axial magnetic resonance (MR) scans were taken for each joint. The dorsoventral disc position was diagnosed by means of the sagittal scans. The mediolateral disc width and position were then measured on every oblique-axial scan. The width and midline was computed for each disc and its deviation from the perpendicular to the condylar long axis was calculated. Finally, a statistical analysis was performed to study whether the disc width and the direction of the disc midline varied between discs normally positioned and anteriorly displaced. Results: The disc width varied significantly more within the anteriorly displaced discs than within the normal ones. The midline of the anteriorly displaced discs deviated more from the perpendicular to the condylar long axis than that of normally positioned discs and was mostly in a lateral direction. The disc midline also deviated more in the ventral than in the dorsal part of the disc. Conclusion: Most anteriorly displaced discs were laterally displaced and showed a larger width variation than normally positioned discs. This fact seems to indicate disc deformation. [ABSTRACT FROM AUTHOR]

Aims: A new individualized oblique-axial orientation of magnetic resonance imaging scans of the temporomandibular joint (TMJ), corrected to be perpendicular to the tangent of the posterior slope of the articular eminence, has been proposed to improve the representation of the disc. The aim of this study was to evaluate the quality of the images obtained with this new type of scanning plane and to assess the factors that can affect the scans. Methods: Twenty-nine TMJs were scanned by the use of sagittal, conventional coronal, and individualized oblique-axial scanning planes. On the sagittal images, the angle α between the tangent of the posterior slope of the articular eminence and the vertical was measured, and the disc position was evaluated. For both imaging planes, 2 examiners, blind to the scanning techniques, counted the number of conventional coronal and oblique-axial scans in which the disc was visible and in which the medial and lateral disc borders were well demarcated and evaluated the mediolateral disc position. Results: The individualized oblique-axial technique was superior to the conventional coronal technique in depicting the disc and its medial and lateral demarcations (paired t test. P < 0.05). The possibility of correct diagnosis of the mediolateral disc position and the agreement between the observers in this evaluation were better with the oblique-axial technique than with the conventional technique (P c 0.05). This was particularly evident when the disc was anteriorly displaced. Conclusion: The individualized oblique-axial scanning planes should be used for a better representation of the discicondyle complex mediotaterally if the disc is anteriorly displaced. [ABSTRACT FROM AUTHOR]