Night-time autonomic nervous system ultradian cycling and masticatory muscle activity.

OBJECTIVES: To test if there was a correlation between night-time masticatory muscle activity, as measured by duty factors, and ultradian cycling of autonomic nervous system (ANS) spectral powers in subjects without temporomandibular disorder (TMD)-related pain. SETTING AND SAMPLE POPULATION: The University of Missouri-Kansas City School of Dentistry. Three women and four men of average ages 38 ±8 and 56 ± 17 years, respectively, gave informed consent to participate. MATERIAL AND METHODS: Investigators taught subjects to record heart (electrocardiography, ECG) and masticatory muscle activities (electromyography, EMG). ECG recordings were analysed for ANS ultradian cycling by a polynomial fit to the ratio of sympathetic and parasympathetic spectral powers (ms2 ). Masseter and temporalis EMG recordings were analysed over 20-minute epochs around peaks and valleys in the ANS ultradian cycles. Duty factors (% time of masticatory muscle activity/20-minute epoch) were determined relative to average threshold EMG (TEMG ) required to produce a given bite force (N). Regression analyses quantified relationships between normalized muscle duty factors and ANS spectral powers. RESULTS: Subjects made a total of 27 sets of night-time ECG and EMG recordings that averaged 6.6 ± 1.1 hours per recording. Highest average duty factors were associated with TEMG of 1-2 N and showed cumulative masseter and temporalis activities of 9.2 and 8.8 seconds/20-minute epoch, respectively. Normalized masticatory muscle duty factors showed non-linear relationships with normalized sympathetic (R2  = +0.82), parasympathetic (R2  = -0.70) and sympathetic/parasympathetic spectral powers (R2  = +0.75). CONCLUSIONS: Night-time ANS spectral powers showed ultradian cycling and were correlated with masseter and temporalis muscle activities in adult subjects without TMD.

MR imaging of the temporomandibular joint: comparison between acquisitions at 7.0 T using dielectric pads and 3.0 T.

OBJECTIVES: To qualitatively and quantitatively compare MRI of the temporomandibular joint (TMJ) at 7.0 T using high-permittivity dielectric pads and 3.0 T using a clinical high-resolution protocol. METHODS: Institutional review board-approved study with written informed consent. 12 asymptomatic volunteers were imaged at 7.0 and 3.0 T using 32-channel head coils. High-permittivity dielectric pads consisting of barium titanate in deuterated suspension were used for imaging at 7.0 T. Imaging protocol consisted of oblique sagittal proton density weighted turbo spin echo sequences. For quantitative analysis, pixelwise signal-to-noise ratio maps of the TMJ were calculated. For qualitative analysis, images were evaluated by two independent readers using 5-point Likert scales. Quantitative and qualitative results were compared using t-tests and Wilcoxon signed-rank tests, respectively. RESULTS: TMJ imaging at 7.0 T using high-permittivity dielectric pads was feasible in all volunteers. Quantitative analysis showed similar signal-to-noise ratio for both field strengths (mean ± SD; 7.0 T, 13.02 ± 3.92; 3.0 T, 14.02 ± 3.41; two-sample t-tests, p = 0.188). At 7.0 T, qualitative analysis yielded better visibility of all anatomical subregions of the temporomandibular disc (anterior band, intermediate zone and posterior band) than 3.0 T (Wilcoxon signed-rank tests, p < 0.05, corrected for multiple comparisons). CONCLUSIONS: MRI of the TMJ at 7.0 T using high-permittivity dielectric pads yields superior visibility of the temporomandibular disc compared with 3.0 T.

Comparison of a 32-channel head coil and a 2-channel surface coil for MR imaging of the temporomandibular joint at 3.0 T.

OBJECTIVE: To quantitatively and qualitatively compare MRI of the temporomandibular joint (TMJ) using a standard TMJ surface coil and a head coil at 3.0 T. METHODS: 22 asymptomatic volunteers were MR imaged using a 2-channel surface coil (standard TMJ coil) and a 32-channel head coil at 3.0 T (Philips Ingenia; Philips Healthcare, Netherlands). Imaging protocol consisted of an oblique sagittal proton density weighted turbo spin echo sequence (repetition time/echo time, 2700/26 ms). For quantitative assessment, a spherical phantom was imaged using the same sequence including a noise scan and a B1+ scan. Signal-to-noise ratio (SNR) maps and B1+ maps were calculated on a voxelwise basis. For qualitative evaluation, all volunteers underwent MRI of both TMJs with the jaw in the closed position. Two independent blinded readers assessed accuracy of TMJ anatomical representation and overall image quality on a 5-point scale. Quantitative and qualitative measurements were compared between coils using t-tests and Wilcoxon signed-rank test, respectively. RESULTS: Quantitative analysis showed similar B1+ and significantly higher SNR for the head coil than the TMJ surface coil. Qualitative analysis showed significantly better visibility and delineation of clinically relevant anatomical structures of the TMJ, including the articular disc, bilaminar zone and lateral pterygoid muscle. Furthermore, better overall image quality was observed for the head coil than for the TMJ surface coil. CONCLUSIONS: A 32-channel head coil is preferable to a standard 2-channel TMJ surface coil when imaging the TMJ at 3.0 T, because it yields higher SNR, thus increasing accuracy of the anatomical representation of the TMJ.

Quantitative and qualitative comparison of MR imaging of the temporomandibular joint at 1.5 and 3.0 T using an optimized high-resolution protocol.

OBJECTIVES: To quantitatively and qualitatively compare MRI of the temporomandibular joint (TMJ) using an optimized high-resolution protocol at 3.0 T and a clinical standard protocol at 1.5 T. METHODS: A phantom and 12 asymptomatic volunteers were MR imaged using a 2-channel surface coil (standard TMJ coil) at 1.5 and 3.0 T (Philips Achieva and Philips Ingenia, respectively; Philips Healthcare, Best, Netherlands). Imaging protocol consisted of coronal and oblique sagittal proton density-weighted turbo spin echo sequences. For quantitative evaluation, a spherical phantom was imaged. Signal-to-noise ratio (SNR) maps were calculated on a voxelwise basis. For qualitative evaluation, all volunteers underwent MRI of the TMJ with the jaw in closed position. Two readers independently assessed visibility and delineation of anatomical structures of the TMJ and overall image quality on a 5-point Likert scale. Quantitative and qualitative measurements were compared between field strengths. RESULTS: The quantitative analysis showed similar SNR for the high-resolution protocol at 3.0 T compared with the clinical protocol at 1.5 T. The qualitative analysis showed significantly better visibility and delineation of clinically relevant anatomical structures of the TMJ, including the TMJ disc and pterygoid muscle as well as better overall image quality at 3.0 T than at 1.5 T. CONCLUSIONS: The presented results indicate that expected gains in SNR at 3.0 T can be used to increase the spatial resolution when imaging the TMJ, which translates into increased visibility and delineation of anatomical structures of the TMJ. Therefore, imaging at 3.0 T should be preferred over 1.5 T for imaging the TMJ.

Macroscopic analysis of human masseter compartments assessed by magnetic resonance imaging.

The human masseter is divided into compartments by aponeuroses. So far, the qualitative and quantitative features of these compartments and their aponeuroses have been scarcely investigated. This study investigated the three-dimensional compartmentalization of the masseter muscle and tested the hypothesis that aponeurosis content varies systematically across different masseter subportions as well as between genders. The right masseter of 14 healthy participants was scanned by magnetic resonance, and the outlines of muscle and aponeuroses were segmented and rendered in three dimensions by AMIRA software. The internal architecture of the masseter muscle varied markedly across individuals, with respect to the number, shape and location of the compartments delimited by aponeuroses. Aponeuroses were widely represented inside the masseter, amounting to 7.1 ± 2.1% of its volume. The aponeurosis content varied systematically across masseter subvolumes and did not differ between genders after adjusting for body height and weight.

Nonfunctional tooth contact in healthy controls and patients with myogenous facial pain.

AIMS: To investigate how often healthy controls and patients with myogenous masticatory pain have wake-time nonfunctional tooth contact, whether the frequency of nonfunctional tooth contact differs between genders or between weekdays and weekends, and whether it is influenced by stress levels. METHODS: The study was performed on 24 subjects: 15 controls and 9 patients with myogenous facial pain. Before data collection the subjects were trained to ascertain their ability to feel correctly whether their teeth were in contact or apart. Subsequently, for 10 days the subjects were alerted by means of a radio wave-activated wrist vibrator approximately every 20 minutes (8:00 AM to 10:00 PM) in order to report whether the teeth were in contact. Subjects also completed 2 stress assessment questionnaires, the Perceived Stress Scale (PSS) and the short version of the Trier Inventory for Assessment of Chronic Stress (TICS-S). RESULTS: There was a significantly higher frequency of wake-time nonfunctional tooth contact in myogenous pain patients than in controls (median of 34.9% and range of 26.5% to 41.3% for patients; median of 8.9% and range of 2.3% to 14.3% for controls; P < .001). In both groups the frequency of nonfunctional tooth contact did not significantly differ among the various days or between the genders. The patients had significantly higher PSS scores and reported having experienced more stressful situations in the dimensions "social overload" and "overextended at work" than the controls. However, PSS and TICS-S scores were not correlated with the frequency of nonfunctional tooth contact for either group. CONCLUSIONS: Myogenous pain patients had nearly 4 times more nonfunctional tooth contact during wake time than controls.