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Objectives: The aim of this study was to assess whether magnetic resonance imaging (MRI) texture features of the lateral pterygoid muscle can distinguish between rheumatoid arthritis (RA) and osteoarthritis (OA) of the temporomandibular joint (TMJ)., Methods: The authors extracted 279 texture features from 36 patients with RA and OA from the region of interest set for the lateral pterygoid muscle on short tau inversion recovery (STIR) images using MaZda Ver.3.3. A total of 10 texture features were selected using Fisher's coefficients, as well as probability of error and average correlation coefficients. Data observed to have a non-normal distribution using the Kolmogorov-Smirnov test were compared using the Mann-Whitney U-test. Receiver operating characteristic (ROC) curves were used to assess the ability of the 10 texture features to distinguish RA and OA of the TMJ., Results: A total of 10 features (5 Correlation, 3 Run Length Nonuniformity, 1 Sigma, and 1 Teta) were selected from 279 texture features. These texture features revealed significant differences between the RA and OA groups ( p < 0.01). The sensitivity, specificity, accuracy, and area under the ROC curve of the texture features for distinguishing RA from OA were 0.78-0.94, 0.89-1.0, 0.86-0.92, and 0.89-0.95, respectively., Conclusion: MRI texture analysis of the lateral pterygoid muscle may be useful for distinguishing between RA and OA of the TMJ.

Objective: Occlusal alteration due to tooth loss may cause overload of masticatory muscle and promote muscle dysfunction. This study explored the feasibility of using functional magnetic resonance imaging (fMRI) to evaluate muscle dysfunction in an established unilateral exodontia animal model., Methods: 6 rabbits were extracted right maxillary molars. T2 mapping, T2* mapping and Iterative Decomposition of water and fat with Echo Asymmetry and Least Square Estimation (IDEAL-IQ) were performed one day before extraction and every 2 weeks (2th~12th week) after extraction. The T2 and T2* values and fat fraction (FF) of bilateral temporal muscle (TM), masseter muscle (MM) and medial pterygoid muscle (MPM) were measured and compared between the extraction side and the contralateral side. Parameters of three monitoring time points (0th, 6th, 12th week) were also analyzed., Results: T2 values of MM on extraction side were significantly higher than those of contralateral side-from fourth week to 12th week after extraction ( p < 0.05). T2 values of MM and MPM on extraction side and TM on contralateral side were significantly higher in 12th week than those in 0th week ( p < 0.05). And FF of bilateral MM was significantly higher in 12th week than those in 0th week ( p < 0.05). T2* value showed no significant difference between extraction side and contralateral side and also at above three time points., Conclusion: T2 and T2* value and FF can be used as indicators of masticatory muscle dysfunction. fMRI is expected to be a non-invasive method for in vivo and real-time evaluation of masticatory muscle functional abnormality.

Objective: The aim of the present study was to evaluate the accuracy of an extraoral CBCT-planned 3D-printed surgical guide aimed to percutaneous injection of substances into the temporomandibular joint (TMJ) and the lateral pterygoid muscle (LPM)., Methods: Nine human cadaver heads were used. Pre-planning CBCT and facial scans were obtained and three percutaneous injection sites were planned: one for the lower compartment of the TMJ and two for the LPM. A digital surgical guide was then designed with small titanium sleeves and printed by a 3D printer. After the injections, new CBCT scans with the needles in place were obtained in order to assess the accuracy of the procedure in relation to the virtual planning., Results: The mean values for angle deviation were very low (range 1.13 o -4.08 o ), the same happening for the mean difference in the length reached (range 1.82-2.64 mm), as well as for the mean difference in the needle tip dislocation (range 0.94-2.03 mm)., Conclusion: The guide seems to be a reliable tool for accurate percutaneous injection of drugs into the inferior compartment of the TMJ and the LPM. Further studies are necessary to test the efficacy and validate the method in an in vivo study.

Objectives: To evaluate non-invasively the morphological features of both lateral pterygoid muscle (LPM) and masseter muscle by using diffusion tensor Imaging on two patients affected by mandibular asymmetry., Methods: Two female patients with mandibular excess and asymmetry who underwent Le Fort I osteotomy and bilateral sagittal split osteotomy were recruited for this study. Morphological (T 1 weighted) and diffusion weighted images were acquired with a 3T scanner 1 week before (T0) and 1 month after the surgery (T1). Probabilistic tensor-based tractography reconstruction of bilateral masseters and LPMs was performed and mean fractional anisotropy (FA) values for both muscles were extracted., Results: Diffusion tensor imaging was able to identify the muscle geometrical morphology and diffusion microstructural changes. Both at T0 and T1, mean FA values had no significant differences between the right and left side of masseter (at T0: p = 0.91; at T1: p = 0.54) and LPM (at T0: p = 0.92; at T1: p = 0.43), respectively. Both patients reported a significant improvement in FA mean values of the left LPM (p = 0.03) between T0 and T1, whereas no diffusion parameters' changes were observed for the bilateral masseter muscles and right LPM., Conclusions: We found that after the surgery the LPM ipsilateral to the deviation side showed a significant increase of FA compared to the baseline. Although preliminary, our findings suggest that diffusion tensor imaging may represent a promising tool to investigate non-invasively the masticatory muscles in temporomandibular joint disorders.

Objectives: To quantitatively evaluate diffusion and perfusion status of lateral pterygoid muscle (LPM) in patients with temporomandibular joint disorder (TMD) by intravoxel incoherent motion (IVIM) imaging and to correlate with findings on temporomandibular joints (TMJs) by conventional MRI., Methods: 42 patients with TMD underwent MRI. To assess IVIM parameters, diffusion-weighted imaging was obtained by spin-echo-based single-shot echoplanar imaging. Regions of interest were created on all diffusion-weighted images of the superior belly of the lateral pterygoid (SLP) and inferior belly of the lateral pterygoid (ILP) at b-values 0-500 s mm -2 . Then, IVIM parameters, diffusion (D) and perfusion (f) were calculated using biexponential fittings. The correlation of these values with conventional MRI findings on TMJs was investigated., Results: For SLP, the f parameter in TMJs with anterior disc displacement without reduction was significantly higher than that in normal ones (p = 0.015). It was also significantly higher in TMJs with joint effusion than in those without (p = 0.016). On the other hand, for both SLP and ILP, the D parameter significantly increased in TMJs with osteoarthritis compared with those without (p = 0.015 and p = 0.022, respectively)., Conclusions: Pathological changes of LPM in patients with TMD may be quantitatively evaluated by IVIM parameters.

Objectives: The aim of this study was to investigate the correlation between the lateral pterygoid muscle (LPM) attachment type and temporomandibular joint (TMJ) disc position on sagittal and coronal MR scans., Methods: 191 patients (148 females, 43 males), aged 14-60 years, underwent MR investigations of the TMJs in the intercuspal position (IP) and open-mouth position (OMP). The disc position was evaluated on oblique sagittal and coronal images in the IP and OMP on many MRI sections showing all portions of the joint. Relationships between the LPM attachment patterns and articular disc positions were evaluated by z and χ 2 tests., Results: Three types of the LPM attachment were found. There was a statistically significant correlation between the LPM attachment type and the disc position in IP (χ 2  = 24.29; p < 0.01). The type of muscle attachment did not determine the prevalence of normal, lateral and medial disc positions. There were differences between the muscle attachment types in the anterior, anteromedial and anterolateral disc positions. There was a statistically significant association between TMJ disc position in OMP and particular attachment types in the sagittal plane (χ 2  = 9.702; p < 0.01)., Conclusions: Certain types of the LPM insertion are correlated with TMJ disc position.

Objectives: To evaluate the reliability of cone beam CT (CBCT) values and dimensional measurements of oropharyngeal air spaces as compared with those of multidetector row CT (MDCT)., Methods: A soft tissue equivalent phantom with different sized holes was used. The phantom was scanned using CBCT and MDCT. In addition, a volunteer was examined using both methods for clinical comparison. The CT data were retrieved to a personal computer and treated using image processing software for three-dimensional rendering and dimensional measurements. The CT values of air, water and soft tissues were measured experimentally and the CT values of air, fat and muscle were measured in a clinical case. The diameter of each hole drilled in the phantom was measured on CBCT and MDCT images using the software tool and digimatic callipers., Results: The CBCT values were quite different from the Hounsfield units obtained with a typical MDCT system. The standard deviations were almost ten times larger with CBCT. In vivo assessment showed that the CBCT values for fat had a wide range that partially overlapped the values for muscle. The measurement of distances greater than 4 mm was consistent for all methods. The difference for holes was less than 0.2 mm., Conclusions: The phantom study showed that CBCT provides limited quantitative CT values for each pixel on sliced images for differentiating air, water and soft tissues. However, the measurement of air spaces with CBCT was quite accurate.

Objective: To investigate the aetiology of Stafne's bone defects by analysing the CT findings of two types of defects, which appeared differently on panoramic radiographs., Methods: 32 lesions with suspicion of the Stafne's bone defect on a panoramic radiograph were categorised into two groups: typical "Stafne type", which showed the connection to the base of the mandible, and non-typical "Cyst type", which showed no connection. Age, sex, the existence of hypertension and the following CT findings: location, size and inner content of the defect, existence of expansion of the buccal cortical bone, and location of submandibular glands, were analysed., Results: There were 14 "Stafne type" and 17 "Cyst type" on the panoramic radiographs. One lesion in the "Cyst type" was a true cystic lesion and was excluded from further review. The "Stafne type" was seen primarily in the posterior and inferior locations, while the "Cyst type" was seen in the anterior and superior locations on the CT. The size of the defect was significantly larger in the "Stafne type". Buccal cortical expansion was observed only in three lesions in the "Stafne type". While the "Cyst type" contained mainly fatty tissue, the "Stafne type" contained other soft tissues. Though the submandibular glands on the defect side were located anteriorly in both types compared with those on the contralateral side and on the control patients, they spread mainly outwards in the "Stafne type"., Conclusion: The Stafne's bone defects are thought to be caused by the dislocated submandibular gland. The differences between the two types might occur as a result of a different location of the submandibular gland.

Objective: The objective of this study was to quantitatively assess masticatory muscle volumes in patients with hemifacial microsomia. Until recently, this congenital malformation was only studied in terms of restoring bony and skin morphologies. Study of the masticatory muscles, however, adds a new dimension., Materials and Methods: Contiguous 1.5 mm CT scans were made using a Philips Tomoscan 350 in six patients with hemifacial microsomia and in one patient without asymmetry. These CT scans were processed by a Cemax 1500X 3D workstation. The volume of the masseter, temporal, and medial and lateral pterygoid muscles was measured from CT scans using three-dimensional (3D) segmentation followed by 3D imaging. The precision and accuracy of measurements of masticatory muscle volumes were investigated. The precision of 3D imaging was assessed by carrying out repeated measurements by two observers. The accuracy of the volume determination technique was assessed by scanning a piece of porcine muscle tissue with a known volume., Results: Intraobserver repeatability was near perfect, with the lowest alpha being 0.96 (for the medial pterygoid muscle). All interobserver correlations were high (>0.99). The accuracy of the method of measurement demonstrated differences ranging from 2.3% to 4.4%., Conclusion: Craniofacial soft tissue measurements obtained from CT scans in patients with hemifacial microsomia were accurate and reproducible but time consuming.

A rare case of tumoral calcinosis, discovered in the medial pterygoid muscle and around the temporomandibular joint on a routine panoramic radiograph is presented. CT was found to be ideal for the determination of the exact location of the calcifications. The differential diagnosis of tumoral calcinosis is discussed.

Quantitative information on the normal size range of the masticatory muscles needed for successful treatment of facial asymmetry is sparse. Our purpose in this study was to define morphological indicators for the volume of the masticatory muscles on CT. Cross-sectional areas and volumes of the masseter and medial pterygoid muscles were measured from CT scans of 65 patients. The muscles were scanned from origin to insertion and the maximum cross-sectional area (MCSA) and its location together with the total volume were determined. The mandibular foramen was used as a landmark to determine the location of MCSA. The location of MCSA of masseter muscle was centred 8 mm above the mandibular foramen, and that of medial pterygoid muscle at the foramen. The MCSA of both muscles was highly correlated with volume suggesting that this parameter might serve as an indicator of their volume. Knowledge of the location of the MCSA would facilitate its measurement and so reduce radiation exposure. There was a positive correlation between the two muscles for both volume and MCSA. This finding could be relevant for future studies of the relationship between the morphology, biomechanics and pathology of the masticatory muscles.