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Background/purpose: The impact of temporomandibular joint (TMJ) osseous destruction on bone mineral density (BMD) remains unclear due to controversial findings. Besides, no previous study has explored the relationship between idiopathic condylar resorption (ICR) and body composition. This study aimed to investigate the relationship between ICR and BMD or body composition. Materials and methods: Between July 2018 and August 2022, patients evaluated by an experienced dentist and diagnosed with temporomandibular disorders (TMDs) were referred to our center. They were recruited while they received the magnetic resonance image (MRI) examination, BMD and body composition completely. Patients were further categorized into TMDs with or without ICR groups according to MRI findings. One-way analysis of variance was used to compare the variables of BMD and body composition in the two groups. Results: In total, 67 patients were included in the analysis, with 42 categorized as TMDs with ICR and 25 as TMDs without ICR. Patients with ICR had a significantly higher lean mass percentage and lower fat mass percentage; lower android/gynoid fat ratio, and visceral adipose tissue area than those without ICR (P

Background/Purpose: Newly developed temporary anchorage devices (TADs) serve a strong orthodontic anchorage to intrude molars for correction of anterior open bite (AOB). We measured cephalometric changes in skeletal open bite patients which developed subsequently to temporomandibular joint disorders with bilateral point contacts at terminal molars. Methods: We retrospectively recruited 32 patients who had been treated their TMD before orthodontic correction (overbite: −3.14 ± 1.86 mm). Partial orthodontic appliances were used to intrude posterior teeth using TADs until positive OB obtained (T1). Full fixed appliances were then used to achieve proper overjet and overbite (T2). We collected lateral cephalograms before (T0), during (T1) and after (T2) treatment, and at follow-ups (T3). Using ANOVA, we analyzed the differences among these time points to determine treatment changes and stability of orthodontic results. Results: In this group predominantly comprising young adult women, orthodontic treatment with TADs significantly reduced upper posterior dental heights (T2-T0:-1.84 ± 0.66 mm) and facilitated the retraction and uprighting upper incisors (T2-T0: −9.92 ± 1.72°), to achieve appropriate OJ (T2-T0: −3.21 ± 0.49 mm) and OB (T2-T0: 4.10 ± 0.28 mm) with p

Purpose: To explore the mandibular condylar movements in patients with temporomandibular joint (TMJ) disorders using kinematic magnetic resonance imaging (MRI). Methods: We retrospectively recruited patients who were clinically diagnosed with internal derangement of the TMJ and referred to our center for MRI examination. The TMJ discs were categorized into normal disc (ND), anteriorly displaced disc (ADD), and disc with destruction (DD) groups using static images obtained in the closed-mouth view. The difference between the “open-mouth” and “closed-mouth” views on kinematic MRI was used to calculate the condylar translation and rotation. Two radiologists consensually performed the image readings and measurements. One-way analysis of variance and chi-squared test were used to compare the variables in the three groups. Pearson's correlation and general linear models were used to evaluate the correlation and differences between condylar translation and rotation in the three groups. Results: This study included 98 TMJs from 54 patients. Twenty-six, 49, and 23 TMJs were classified as ND, ADD, and DD, respectively. Condylar rotation and translation demonstrated a significant correlation in all TMJs examined (r = 0.635, p

AbstractIntroduction Sonoelastography has been increasingly used for non-invasive evaluation of the mechanical features of human tissues. The interplay between orofacial pain and regional muscle activity appears clinically paramount, although only few imaging studies have investigated this association. Using shear wave sonoelastography (SWS), this study ascertained whether orofacial pain induced alterations in the stiffness of superficial and deep masticatory muscles.Methods All participants were systematically evaluated for oral/facial-related conditions, including the area and intensity of pain. SWS was applied to measure the stiffness of the bilateral masseter, temporalis, and lateral pterygoid muscles. The association between orofacial pain and muscle stiffness/thickness was investigated using a generalized estimating equation for adjusting the influence of age, sex, laterality, and body mass index on muscle thickness/stiffness.Results A total of 98 participants were included in the present study: 48 asymptomatic controls, 13 patients with unilateral pain, and 37 patients with bilateral orofacial pain. The reliability, quantified by the intraclass correlation coefficient for muscle stiffness measurement, ranged from 0.745 to 0.893. Orofacial pain at the individual muscle level was significantly associated with masseter muscle stiffness. A trend of increased stiffness (p = 0.06) was also observed in relation to the painful side of the temporalis muscle. No significant correlation was identified between the numeric rating scales for pain and stiffness measurements.Conclusions SWS provides reliable stiffness measurements for the superficial and deep masticatory muscles. The ipsilateral masseter and temporalis muscles might be stiffer than those on the side without orofacial pain. Future studies using the present sonoelasotography protocol can be designed to investigate the stiffness changes in the target muscles after interventions.

Background/purpose: The nature of susceptibility to condylar resorption after orthognathic surgery can be different between skeletal Class II and Class III populations, which was addressed by few in the past. The aim of the present study was to use cone-beam computed tomographic (CBCT) images to investigate the displacement and morphological changes of temporomandibular joints (TMJs) in patients received orthodontic treatment combined with orthognathic surgery. Methods: Both Class III (n = 34) and Class II (n = 17) patients were compared through overall and regional superimpositions of the initial and posttreatment CBCTs. Two-sample t-test was used to identify significance between group differences. Pearson's correlation coefficient was used to address changes of TMJ and the amount of setback or advancement. Results: The axial ramal angle increased significantly in Class III group and decreased in Class II groups after orthognathic surgery (p

Knowledge of mandibular growth and development is essential for diagnosis of malformation and early interception. A previous method of quantifying mandibular growth using the distances between selected anatomical landmarks over the growth period does not provide a complete, quantitative description of the continuous growth patterns. The current study aimed to bridge the gap by measuring the 3D continuous growth of the mandible in miniature pigs using cone-beam computerized tomography (CBCT). The mandibles of the pigs were CBCT-scanned monthly over 12 months, and the 3D mandibular models were reconstructed. A new non-linear, time-dependent osteometric modeling approach was developed to register two consecutive mandible models by searching for the corresponding points with the highest likelihood of matching the anatomical and morphological features so that the morphological changes patterns for each month could be described using color maps on the models. The morphological changes of the mandible were found to decrease anteriorly, with the condyle region and the posterior part of the ramus growing faster than the rest of the mandible. The condyle region showed the fastest growth rate and the posterior ramus the second during the growth period, while the middle and anterior corpus regions showed the slowest growth rates. In conclusion, the current results revealed the non-linear patterns and rates of morphological changes in different growth regions and the whole mandible. The new approach may also be useful for future studies on the growth of the mandible in other animals.

Few studies have explored the feasibility of shear-wave ultrasound elastography (SWUE) for evaluating the upper airways of patients with obstructive sleep apnea (OSA). This study aimed to establish a reliable SWUE protocol for evaluating tongue muscle elasticity and its feasibility and utility in differentiating patients with OSA. Inter-rater and intra-rater reliability of SWUE measurements were tested using the intraclass correlation coefficients. Submental ultrasound was used to measure tongue thickness and stiffness. Association between the ultrasound measurements and presence of OSA was analyzed using multivariate logistic regression. One-way analysis of variance was used to examine if the values of the ultrasound parameters varied among patients with different severities of OSA. Overall, 37 healthy subjects and 32 patients with OSA were recruited. The intraclass correlation coefficients of intra‐ and inter-rater reliability for SWUE for tongue stiffness ranged from 0.84 to 0.90. After adjusting for age, sex, neck circumference, and body mass index, the risk for OSA was positively associated with tongue thickness [odds ratio 1.16 (95% confidence interval 1.01–1.32)] and negatively associated with coronal imaging of tongue muscle stiffness [odds ratio 0.72 (95% confidence interval 0.54–0.95)]. There were no significant differences in tongue stiffness among OSA patients with varying disease severity. SWUE provided a reliable evaluation of tongue muscle stiffness, which appeared to be softer in patients with OSA. Future longitudinal studies are necessary to investigate the relationship between tongue softening and OSA, as well as response to treatment.

High-resolution ultrasound is preferred as the first-line imaging modality for evaluation of superficial soft tissues, such as the facial muscles. In contrast to magnetic resonance imaging and computed tomography, which require specifically designated planes (axial, coronal and sagittal) for imaging, the ultrasound transducer can be navigated based on the alignment of facial muscles. Botulinum toxin injections are widely used in facial cosmetic procedures in recent times. Ultrasonography is recognized as a useful tool for pre-procedure localization of target muscles. In this pictorial review, we discuss the detailed sonoanatomy of facial muscles and their clinical relevance, particularly with regard to botulinum toxin injections. Furthermore, we have summarized the findings of clinical studies that report ultrasonographic imaging of facial muscles.

Abstract Background Cephalometric radiography has been used for orthodontic and surgical treatment planning and assessment, and for quantifying mandibular growth. However, it remains unclear how head positioning errors and the level of examiner experience affect the reliability of such morphometric measurements. The current study aimed to bridge the gap by determining the intra-, inter-rater, and inter-session reliability of measurements of mandibular morphology with random head positioning errors as measured by a junior and a senior dentist. Methods Cone-beam computed tomography data of twelve mandibles were obtained with each rotated randomly away from the neutral position within the range of +3 and −3° along each of the anatomical axes to simulate six imaging trials. A synthetic cephalogram for each trial was obtained via a digitally reconstructed radiography (DRR) technique and eleven landmarks for twelve morphological parameters on the cephalogram were identified manually six times by a junior and a senior dentist. The procedure was repeated on another day within 5 days. Test–retest reliability was assessed in terms of an intra-class correlation coefficient (ICC) using a two-way mixed-effects model. Results Good to very good intra-rater (senior: ICC > 0.92; junior: ICC > 0.78), inter-rater (ICC > 0.70 for most parameters) and inter-session reliability (senior: ICC > 0.84; junior: ICC > 0.62) were found. Bland & Altman plots of inter-rater comparisons show that there were systematical biases between the examiners on most parameters, except for the distance between Gonion and Pogonion. Conclusions The current results suggest that good to very good intra-rater, inter-rater and inter-session reliability can be achieved for most parameters with randomized head positioning errors; higher inter-session reliability can be achieved by more experienced examiners; and that long-term monitoring of mandibular growth based on cephalographic measurements should be made by the same more experienced examiner. The current DRR-based approach can be used to evaluate individual factors that affect the morphological measurements.

[This corrects the article DOI: 10.1371/journal.pone.0187032.].

Cone-beam computed tomography (CBCT) can provide valuable data for root canal systems of human teeth in vivo. This study used CBCT to evaluate the number of roots and canals of 300 mandibular first premolars in 150 northern Taiwanese patients. Methods: The root canal systems of 300 mandibular first premolars in 150 northern Taiwanese patients with bilateral premolars were analyzed by CBCT. Results: Of the 300 mandibular first premolars, 197 (65.7%) had one root with one canal (1R1C), 49 (16.3%) had one root with two canals (1R2C), 51 (17.0%) had two roots with one canal in each root (2R2C), and three (1.0%) had three roots with one canal in each root (3R3C). Statistical analyses showed that women had a significantly higher incidence of 1R1C mandibular first premolars (71.4%) than men (58.8%, p = 0.031), and men had a significantly higher incidence of 2R2C mandibular first premolars (27.2%) than women (8.5%, p

Background/purpose: The current study aimed to determine the intra- and inter-rater, and intersession reliability of the determination of the morphological parameters of the human mandible using cone-beam computed tomography (CBCT)-synthesized cephalometric radiographs. Materials and methods: CBCT data of 12 mandibles were obtained and used to generate synthetic cephalograms via a digitally reconstructed radiography (DRR) technique. Eleven landmarks describing the key morphological features of the mandible on each DRR-synthesized cephalogram were identified manually six times by one senior and one junior dentist. The operation was repeated 5 days later. Twelve parameters based on interlandmark line segments and their angles were calculated. Test–retest reliability was assessed in terms of intraclass correlation coefficient (ICC) and coefficient of variation (CV) using a two-way mixed-effects model. The paired-sample t-test was used to compare differences between examiners and sessions. A one-sample t-test was employed to assess whether the difference between the examiners was significantly different from zero. Results: Very good intrarater (senior: ICC > 0.93; junior: ICC = 0.78 for CdP-GoP, ICC > 0.91 for other parameters), inter-rater (ICC = 0.62 for CdP-GoP, ICC > 0.84 for other parameters) and intersession reliability (ICC > 0.84 for all parameters and examiners; ICC = 0.74 for CdP-GoP for junior examiner) in measuring mandibular morphological parameters were found. Conclusion: These results suggest that very good reliability could be achieved via manual identification of the anatomical landmarks without the effects of factors such as malpositioning of the head during imaging. Further investigations using the current DRR-based approach will be needed to evaluate the individual effects of these other factors on the morphological measurements.

This study aimed to determine the effect of combining positive airway pressure (PAP) therapy and mandibular advancement device (MAD) in patients with severe obstructive sleep apnea (OSA) who were pressure intolerant for PAP and were unresponsive to MAD.This retrospective study reviewed the medical records of severe OSA patients with apnea-hypopnea index (AHI) ≥ 30/hr who were diagnosed between October 1, 2008 and June 30, 2014. Patients were initially treated with 2 weeks of PAP, and those who were intolerant to high-pressure PAP (≥15 cm H2O) were switched to 12 weeks of MAD, which is a monobloc designed at 75% of maximum protrusion. Patients who had high residual AHI (≥15/hr) on MAD underwent 12 weeks of combination therapy (CT) with MAD and CPAP and were enrolled in the present study. Enrolled subjects who completed the 12-week CT were followed-up until June 30, 2016.A total of 14 male patients were included. All three treatments effectively reduced AHI, oxygen desaturation index (ODI), and total sleep time with SpO2

Background/purpose: To identify how dentoalveolar changes compensate for proper overbite in extreme vertical facial patterns. Materials and methods: Lateral cephalometric roentgenograms of preorthodontic adult patients with hyperdivergent (n = 49; SN-mandibular plane (MP) angle greater than 38 degrees) and hypodivergent (n = 38; SN-MP angle less than 28 degrees) skeletal patterns were selected. Skeletal-vertical (SV) variables were selected and summarized via stepwise regression methods and principal component analysis (PCA) in these two groups. Multiple regression analyses were performed to determine the relationship between overbite (OB) as the dependent variable and the PCA-derived SV, dental height (DH), and dental inclination (DI) as the independent variables. Results: Hyperdivergent patients have the tendency of anterior open bite. The natural dentoalveolar compensatory mechanism is manifested in shorter upper molar height and larger lower incisor height. Hypodivergent patients have no tendency of anterior deep bite. The shorter upper and lower incisor DHs and larger incisal inclination achieved dentoalveolar compensatory mechanism in these patients. Conclusion: For orthodontically closing the open bite, intruding upper posteriors and extruding lower anteriors are appropriate ways to simulate the natural occurring compensation. To eliminate deep bite in a low mandibular plane patient, intruding upper and lower anteriors and proclining anteriors will achieve good overbite. Imitating the natural dentoalveolar compensation by using temporary anchorage devices at appropriate sites for intruding teeth helps to resolve orthodontic vertical problems.

Background/purpose: The measurement of mandibular kinematics is critical for studying the function of the temporomandibular joint (TMJ) and for relevant clinical applications. However, none of the existing methods allows the measurement of three-dimensional (3D) in vivo motion of the joint during dynamic functional movements without artifactual interference. The purpose of this study was to demonstrate the feasibility of a newly developed cone-beam computed tomography (CBCT)-based 3D fluoroscopic method in differentiating rigid-body kinematics of the TMJ during various functional activities. Materials and methods: One healthy individual was asked to undergo a CBCT scan and fluoroscopic imaging of her mandible and maxilla during various functional activities. CBCT-based 3D fluoroscopy was used to measure the 3D kinematics of the TMJ. Results: The 3D rigid-body kinematics of the mandible, movement trajectories of the centers of the TMJ and the midpoint of the interincisal edge were measured during functional activities. Conclusion: A new CBCT-based 3D fluoroscopic method was proposed and shown to be capable of quantitatively differentiating TMJ movement patterns among complicated functional activities. It also enabled a complete description of the rigid-body mandibular motion and descriptions of as many reference points as needed for future clinical applications. It will be helpful for dental practice and for a better understanding of the functions of the TMJ.

Background/purpose: Nowadays, mini-implant anchorage is incorporated for achieving a variety of orthodontic treatment goals. However, when a miniscrew is located in the interdental area, potential root contact may lead to miniscrew mobility or even failure. Therefore, miniscrew/root contact and possible tissue responses, including root repair, were histologically investigated in the current study. Materials and methods: Eight miniscrews were surgically placed in a single dog mandible. Among these, four miniscrews (experimental group) were intentionally placed in contact with a root and then retained for different time durations, three (control group) were also intentionally placed in contact with a root but were immediately removed after insertion, and one was placed without root contact and was retained for 24 weeks. The animal was sacrificed after 24 weeks. Results and conclusions: (1) Tissue surrounding roots damaged by a miniscrew showed a significant inflammatory response. (2) Root resorption was occasionally observed after 3 weeks following insertion of a miniscrew even if the miniscrew was not in direct contact with the root. (3) Root repair was noted with a cementoblast lining along the resorption surface at as early as 3 weeks after miniscrew insertion. Alveolar bone filled in the lesion when the root damage was large so that the contour of the alveolar bone followed that of the damaged root, with the width of the periodontal ligament space being maintained. (4) Stable miniscrews were mainly those which did not contact adjacent roots, and for which the surrounding tissue showed only a small inflammatory response with some extent of direct bone contact around the miniscrew. On the contrary, most of the failed miniscrews were those which had direct contact with adjacent roots, and which exhibited severe tissue inflammation and were covered by thick layers of soft tissue. Failure was detected 3 weeks after insertion. Surprisingly, the epithelial lining surrounding the miniscrews might not have spontaneously resolved 6 weeks after screw removal. Persistent infection in the sinus tract was noted, and this would require attention.

Background/purpose: Skin marker-based systems are used to accurately measure the three-dimensional motion of the temporomandibular joint. Since skin markers move relative to the underlying bone during jaw movements, the measured temporomandibular joint kinematics is subject to soft-tissue artifacts. A complete evaluation of soft-tissue artifacts for markers on the facial anatomical landmarks and on an optical frame during jaw opening/closing movements is not available. The purpose of this study was to further our knowledge using a commercial opto-electronic movement tracking system to measure marker movements, that were then compared to true values defined by a transoral rigid device attached to the incisors. Materials and methods: Twenty healthy subjects performed jaw opening/closing movements at a self-selected pace while the 3D trajectories of 17 facial skin markers, three markers on an optical frame, and 4 markers on a transoral device were measured using a six-camera opto-electronic motion tracking system. Movements of the skin and optical frame markers relative to the head coordinate system defined by the transoral device (gold standard) were calculated. The movements of the head coordinate systems defined using different groups of skin markers relative to the gold standard were also analyzed. Results: The results showed that nose-bridge markers had minimal displacements but the middle- and side-face markers had large displacements. Conclusions: It appears that markers on the frontal nose bridge are good alternatives to transoral rigid devices for measuring mandibular motion, compared to optical frame markers and other skin markers on the face. The results of the current study will be helpful for establishing guidelines for marker placement when measuring mandibular movements in patients with potential temporomandibular disorders.

Obstructive sleep apnea (OSA), which is caused by obstructions of the upper airway, is a syndrome with rising prevalence. Mandibular advancement splints (MAS) are oral appliances for potential treatment of OSA. This work proposes a highly-sensitive pressure sensing array integrated with a system-on-chip (SoC) embedded in a MAS. The device aims to measure tongue pressure distribution in order to determine the efficacy of the MAS for treating OSA. The flexible sensing array consists of an interdigital electrode pair array assembled with conductive polymer films and an SoC capable of retrieving/storing data during sleep, and transmitting data for analysis after sleep monitoring. The surfaces of the conductive polymer films were patterned with microdomed structures, which effectively increased the sensitivity and reduced the pressure sensing response time. The measured results also show that the crosstalk effect between the sensing elements of the array was negligible. The sensitivity of the sensing array changed minimally after the device was submerged in water for up to 100 h.

Sleep apnea is a serious sleep disorder, and the most common type is obstructive sleep apnea (OSA). Untreated OSA will cause lots of potential health problems. Oral appliance therapy is an effective and popular approach for OSA treatment, but making a perfect fit for each patient is time-consuming and decreases its efficiency considerably. This paper proposes a System-on-a-Chip (SoC) enabled sleep monitoring system in a smart oral appliance, which is capable of intelligently collecting the physiological data about tongue movement through the whole therapy. A tunneling sensor array with an ultra-high sensitivity is incorporated to accurately detect the subtle pressure from the tongue. When the device is placed on the wireless platform, the temporary stored data will be retrieved and wirelessly transmitted to personal computers and cloud storages. The battery will be recharged by harvesting external RF power from the platform. A compact prototype module, whose size is 4.5 × 2.5 × 0.9 cm3, is implemented and embedded inside the oral appliance to demonstrate the tongue movement detection in continuous time frames. The functions of this design are verified by the presented measurement results. This design aims to increase efficiency and make it a total solution for OSA treatment.

The purpose of this study was to measure the long-term growth of the mandible in miniature pigs using 3D Cone-Beam Computerized Tomography (CBCT). The mandibles of the pigs were scanned monthly over 12 months using CBCT and the 3D mandibular models were reconstructed from the data. Seventeen anatomical landmarks were identified and classified into four groups of line segments, namely anteroposterior, superoinferior, mediolateral and anteroinferior. The inter-marker distances, inter-segmental angles, volume, monthly distance changes and percentage of changes were calculated to describe mandibular growth. The total changes of inter-marker distances were normalized to the initial values. All inter-marker distances increased over time, with the greatest mean normalized total changes in the superoinferior and anteroposterior groups (p

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]