Biochemical analysis of the articular disc of the temporomandibular joint with magnetic resonance T2 mapping: a feasibility study.

OBJECTIVES: Symptoms of temporomandibular joint (TMJ) dysfunction can seriously compromise patients' quality of life. The aim of our study was to use magnetic resonance imaging (MRI) T2 mapping of the articular disc to determine whether T2 mapping of the TMJ disc is feasible in routine clinical imaging and to assess the normal T2 relaxation time distribution within the TMJ. METHODS: Included were ten asymptomatic volunteers without pain, any mouth-opening limitations, or any clicking phenomena. MR imaging was performed on a 3-T MR scanner using a flexible, dedicated, eight-channel multielement coil. T2 mapping was performed in the oblique sagittal plane. The regions of interest (ROIs) for the T2 relaxation time maps of the disc were selected manually. RESULTS: The mean values for ROIs ranged between 22.4 and 28.8 ms, and the mean for all ROIs was 26.0 ± 5.0 ms. Intraclass correlation (ICC) for interobserver variability was 0.698, and ICC for intraobserver variability was 0.861. There was no statistically significant difference between raters (p = 0.091) or sides (p = 0.810). CONCLUSION: The T2 mapping technique enables ultrastructural analysis of the composition of TMJ disc. This biochemical technique is feasible in vivo, as shown in our study, when a high-field (3 T) MR and a dedicated TMJ coil are used. CLINICAL RELEVANCE: T2 mapping as a biochemical technique, together with morphological MRI, may help to gain more insights into the physiology and into the pathophysiology of the articular disc in the TMJ noninvasively and in vivo.

Early diagnosis of degenerative changes in the articular/fibrocartilaginous disc of the temporomandibular joint in patients with temporomandibular disorders using delayed gadolinium-enhanced MRI at 3 Tesla - preliminary results.

BACKGROUND: Delayed gadolinium enhanced MRI of cartilage (dGEMRIC) is a quantitative method for assessment of glycosaminoglycan content in connective tissues. We hypothesize that the early diagnosis of degenerative changes in the temporomandibular joint could be diagnosed using dGEMRIC technique. PURPOSE: To test the compositional MRI technique, dGEMRIC, at 3 Tesla to diagnosis early the degenerative changes in the fibrocartilaginous disc of the temporomandibular joint (TMJ) in patients with temporomandibular disorders (TMD) and to compare the dGEMRIC index of patients to the healthy volunteers. METHODS: Six volunteers (two men, four women; 20.8÷28.1 years) and eleven patients (22 TMJs, seven women, four men; 24÷54 years) were recruited for this prospective trial. Only patients with no morphological abnormality on MRI and without disc dislocations were included. Volunteers were used as a control group. The PD-weighted FSE sequence and the 3D GRE (DESS) sequence protocols were performed for morphological assessment. The Inversion recovery (IR) sequence was performed for T1 relaxation time measurements and intra-venous (IV) contrast agent administration was used according to the dGEMRIC protocol. T1 maps were calculated offline and ROIs were drawn on TMJ discs by a specialist trained in TMD disorders. Statistical evaluation was performed by ANOVA and correlations were calculated. RESULTS: The difference between the dGEMRIC values in the TMJ articular discs of the patients and the volunteers was statistically significant (P = .019). After contrast agent administration the T1 values dropped in both groups. In patient group was the T1 drop stronger (-54% from initial pre-contrast value), while in control group was the T1 drop less pronounced (-46% from initial pre-contrast value). CONCLUSIONS: dGEMRIC seems to be a useful, compositional, quantitative method, suitable also for small joints, such as the articular disc of the TMJ. The results of the dGEMRIC index in the articular disc of the TMJ imply a lower GAG content in patients with TMJ disorders.

T2 mapping with 3.0 T MRI of the temporomandibular joint disc of patients with disc dislocation.

INTRODUCTION: T2 mapping, as a quantitative biochemical MRI-technique that provides information on water and collagen fiber content and composition, was shown to be clinically feasible for the evaluation of healthy temporomandibular joints. OBJECTIVES: The aim of our study was to compare the T2 values of whole discs in patients with and without disc dislocation, to evaluate the possible influence of morphological findings on T2 values and to assess the interrater agreement. METHODS: Sixty-six patients were included in the study. Three experienced examiners assessed the perceptibility of the morphological parameters and the position of the articular disc on the morphological MR images. On the T2 maps, the T2 values of the region-of-interest (ROI) were assessed. RESULTS: The ICC (Intraclass Correlation Coefficient) for the reproducibility of the T2 values was 0.717. The assessment of the morphologic parameters was excellent or good in most of the discs. There was no significant difference in the T2 values based on disc position or signal intensity. But, a statistically significant moderation effect (p = .014) could be identified, indicating that the effect of disc position differs for different signal intensities. Condyle position, effusion, and degenerative changes showed pronounced moderation effects on the T2 values. CONCLUSION: Due to the high sensitivity to effusion, T2 mapping currently seems to be unsuitable as a diagnostic tool for routine use in the temporomandibular joint. The moderation effect clearly shows the influence of factors such as signal intensity, effusion, arthrosis, and condyle position. Perhaps a solution for these problems could be the development of dedicated TMJ coils for higher field strengths at 7.0 T.

Regional Collagen Fiber Network in the Articular Disc of the Human Temporomandibular Joint: Biochemical 3-Tesla Quantitative Magnetic Resonance Imaging Compared to Quantitative Histologic Analysis of Fiber Arrangement.

AIMS: To evaluate the regional collagen fiber network in the human temporomandibular joint (TMJ) disc by using biochemical magnetic resonance imaging (MRI) and quantitative histology. METHODS: MRI of 5 heads (10 TMJ discs) obtained from partially dentate or edentulous cadavers was performed at 3-Tesla MRI by using a flexible, 8-channel transmit-receive coil. After MRI, all 10 discs were processed histologically. Percentages of coronal, sagittal, and transverse collagen fibers were assessed stereologically for the anterior, central, and posterior parts of the disc. An anisotropy index was calculated for collagen fiber arrangement in all three regions of interest. RESULTS: In the central part of the TMJ disc, collagen fibers were arranged anisotropically with a preferentially sagittal direction. In the anterior and posterior parts, evidence for fibers being arranged isotropically (randomly) without preferred direction was found. Mean MRI T2 values appeared to be correlated with the anisotropy index of collagen fibers (r = -0.45; P < .05). When tested individually, T2 values of the isotropic anterior and posterior disc regions showed a partial but significant correlation with the anisotropy index of collagen fibers (r = -0.54; P < .05), whereas the anisotropic central part did not (P > .05). CONCLUSION: This study has provided the first systematic comparison of quantitative data on collagen fiber isotropy and anisotropy assessed in histologic sections with biochemical quantitative MRI for human TMJ fibrous cartilage.

Cytotoxicity of resin composites as a function of interface area.

OBJECTIVES: The standardization protocols for biomaterial cytotoxicity testing require fine tuning for oral biomaterials to obtain international comparability as the basis for risk assessment. The principal aims were specifically to evaluate the effect of (i) relative interface area (ratio of specimen surface to cell layer surface) and (ii) volume of cell culture medium on cytotoxicity as a potential modification of ISO 10993-5. METHODS: ISO 10993-5 was followed with an interface area of 12.5%, as recommended, using primary human gingival fibroblasts and L-929 mouse fibroblasts. In another series of experiments (using L-929 cells) the interface area was varied between 12.5% and 0.71%. For each relative interface area, three conditions for affecting the cure of the resin composite were investigated by using three mould materials: white, transparent and black moulds. In addition, the volume of cell culture medium was varied. Composite specimens (Herculite XRV) were added to the cultures immediately after production or preincubation for 1, 2, 7 days or 6 weeks under cell culture conditions. Specimens were incubated with fibroblasts for 72 h and cell numbers determined by flow cytometry. Glass specimens resembling composite specimens in diameter and height were used as negative controls. RESULTS: Cytotoxicity results with primary gingival fibroblasts were comparable to results with the cell line L-929. An effect from the color/material of the specimen moulds was found. Different ratios of specimen sizes to cell culture parameters (cell layer surface, volume of cell culture medium) produced different results. Three out of four differently designed specimens showed the same behavior in cell culture. SIGNIFICANCE: Cytotoxicity tests should be further standardized in line with existing standards with regard to specimen production protocols to ensure results are internationally comparable to validate these tests as tools for risk assessment.

The treatment experience questionnaire: development and validation of a questionnaire assessing the individual's emotional, perceptual, and cognitive reactions to alternative, physical, and dental treatments.

BACKGROUND: The aim of this study was to develop and validate a questionnaire designed to assess the patient's affective, cognitive, and perceptual state during treatment administration. METHODS: 362 individuals (214 females, 148 males, mean age 54.6 years) with predominantly musculoskeletal or dental problems participated in the study. Patients responded to the questionnaire immediately following a treatment. The questionnaire included items of 9 proposed scales devised to assess mood, psychological tension, sleepiness, mental absorption, treatment appraisal, perceived cooperation during treatment administration, perceived somatosensory intensity of treatment as well as negative and positive bodily sensations during treatment. Treatments were administered in 2 spa centers, a clinic for physical medicine and rehabilitation and a clinic for dentistry. Treatments investigated were among others dental treatment, massage, packs, baths, relaxation training, exercise, and acupuncture. RESULTS: The proposed scales were confirmed. Scales had adequate to good reliability and validity. All scales significantly distinguished between treatments. CONCLUSION: The devised questionnaire has adequate properties to assess patients' experiences during treatment administration.

Testing for aerobic heterotrophic bacteria allows no prediction of contamination with potentially pathogenic bacteria in the output water of dental chair units.

BACKGROUND: Currently, to our knowledge, quality of output water of dental chair units is not covered by specific regulations in the European Union, and national recommendations are heterogeneous. In Germany, water used in dental chair units must follow drinking water quality. In the United States of America, testing for aerobic heterotrophic bacteria is recommended. The present study was performed to evaluate whether the counts of aerobic heterotrophic bacteria correlate with the presence of potentially pathogenic bacteria such as Legionella spp. or Pseudomonas aeruginosa. METHODS: 71 samples were collected from 26 dental chair units with integrated disinfection device and 31 samples from 15 outlets of the water distribution pipework within the department were examined. Samples were tested for aerobic heterotrophic bacteria at 35°C and 22°C using different culture media and for Legionella spp. and for Pseudomonas aeruginosa. Additionally, strains of Legionella pneumophila serogroup 1 were typed with monoclonal antibodies and representative samples of Legionella pneumophila serogroup 1 were typed by sequence based typing. RESULTS: Our results showed a correlation between different agars for aerobic heterotrophic bacteria but no correlation for the count of aerobic heterotrophic bacteria and the presence of Legionella spp. or Pseudomonas aeruginosa. CONCLUSION: Testing for aerobic heterotrophic bacteria in output water or water distribution pipework within the departments alone is without any value for predicting whether the water is contaminated with potentially pathogenic bacteria like Legionella spp. or Pseudomonas aeruginosa.