The "5Ts" screening tool: Enhancements and threshold values for effective TMD identification

OBJECTIVE

This study aimed to enhance the quintessential "five temporomandibular disorder (TMD) symptoms" (5Ts) screener by incorporating frequency options and distinguishing between TMJ and muscle pain. The diagnostic accuracy along with cut-off points for the effective identification of TMDs was also established.

METHODS

Participants, aged ≥18 years, were recruited from a university-based hospital. After completing surveys encompassing demographic data and the enhanced 5Ts (with frequency options [5Ts-F] and differentiation of TMJ/muscle pain [6Ts-F]), protocolized interviews and clinical examinations were performed following DC/TMD. The diagnostic accuracy and best cut-off points were determined with the area under the receiver operating characteristic curves (AUCs).

RESULTS

324 participants were recruited (mean age 30.0 ± 11.4 years). Among these, 86.4% had TMDs. 5Ts exhibited high diagnostic accuracy for detecting all TMDs (AUC = 0.92) with sensitivity/specificity values of 83.9%/88.6%. Both 5Ts-F and 6Ts-F had slightly better accuracy (AUCs = 0.95/0.96), comparable sensitivity, and superior specificity (97.7%) compared to 5Ts. The best cut-off points were 1.5 for 5Ts and 2.5 for 5Ts-F/6Ts-F.

CONCLUSIONS

Although all three TMD screeners presented high diagnostic accuracy, 5Ts-F/6Ts-F had notably improved specificity. 5Ts scores of >1.5 and 5Ts-F/6Ts-F scores of >2.5 are to be applied for screening the presence of TMDs.

[Research status and outlook of deep learning in oral and maxillofacial medical imaging]

Artificial intelligence, represented by deep learning, has received increasing attention in the field of oral and maxillofacial medical imaging, which has been widely studied in image analysis and image quality improvement. This narrative review provides an insight into the following applications of deep learning in oral and maxillofacial imaging: detection, recognition and segmentation of teeth and other anatomical structures, detection and diagnosis of oral and maxillofacial diseases, and forensic personal identification. In addition, the limitations of the studies and the directions for future development are summarized.

[Research status and outlook of deep learning in oral and maxillofacial medical imaging]

Artificial intelligence, represented by deep learning, has received increasing attention in the field of oral and maxillofacial medical imaging, which has been widely studied in image analysis and image quality improvement. This narrative review provides an insight into the following applications of deep learning in oral and maxillofacial imaging: detection, recognition and segmentation of teeth and other anatomical structures, detection and diagnosis of oral and maxillofacial diseases, and forensic personal identification. In addition, the limitations of the studies and the directions for future development are summarized.

[Three-dimensional quantitative evaluation of condylar bone remodeling of temporomandibular joint based on cone-beam CT imaging]

Objective: To establish a three-dimensional （3D） quantitative measurement and evaluate the condylar bone remodeling of temporomandibular joint (TMJ). Methods: Pre-and post-treatment cone-beam CT (CBCT) data were obtained from 41 patients ［10 males, 31 females, mean age of (19.7±4.4) years (12-30 years old)］, who visited the Center for TMD and Orofacial Pain, Peking University School and Hospital of Stomatology from November 2014 to August 2019, and diagnosed with acute disc displacement without reduction or disc displacement with reduction, with intermittent locking and treated by manual disc reduction followed by anterior repositioning splint. First, condylar bone remodeling was evaluated according to the number of "double contour image" and qualitatively classified as no remodeling (no double contour image), partial remodeling (1-4 double contour images) and remarkable remodeling (5-6 double contour images). Then, condylar bone remodeling was quantitatively evaluated by CBCT based 3D measurement: segmenting condylar images using a semi-automatic method of the manually preliminary mark combined with watershed algorithm, reconstructing the surface models, superimposing the pre-and post-treatment condylar images and finally calculating the volumetric differences of condyle and condylar head, respectively. Results: The Kappa values of two-dimensional (2D) qualitative evaluation were 0.66-0.87, and 3D quantitative measurements of condyle and condylar head volume were also reliable, with the intraclass correlation coefficient (ICC) values of intra-observer 0.998/0.941 and inter-observer 0.999/0.942 respectively. The volumetric increment of the condyle and condylar head after treatment was (41.7±90.2) mm³ and (62.8±70.9) mm³, respectively. Eighty-two condyles were divided into three sub-groups: no remodeling (21), partial remodeling (20) and remarkable remodeling (41). Ranking of the volumetric increment of the condyle and condylar head after treatment was as follows: remarkable remodeling group>partial remodeling group>no remodeling group (P<0.05). Conclusions: The 3D quantitative measurement for evaluating condylar bone remodeling had excellent consistency and reliability, which was consistent with the qualitative classification for condylar bone remodeling. The condylar head as a region of interest was more sensitive to the volumetric changes.

[Experts consensus on MRI examination specification and diagnostic criteria of temporomandibular joint disc displacement]

The document represented the consensus amongst the professionals from the Society of TMD & Occlusion, Chinese Stomatological Association and provided guidelines with the MRI examination specification and diagnostic criteria of temporomandibular joint disc displacement.

[Association between tooth missing and non-alcoholic fatty liver disease]

Objective: To evaluate the association between the number of teeth missed and the prevalence of non-alcoholic fatty liver disease (NAFLD) in adults. Methods: A cross-sectional study was carried out in 26 983 adults from Tianjin Chronic Low-grade Systemic Inflammation and Health Cohort Study. The number of teeth missed (excluding third molars) was recorded and classified into four categories: 0, 1-, 3- and ≥6. NAFLD was diagnosed by at least two liver ultrasonography examinations. Adjusted multivariable logistic regression analysis was used to access the association between the number of missed teeth and NAFLD in adults. Results: The overall prevalence of NAFLD was 7 270 and the number of the subjects with at least one tooth missed was 9 667. The multivariable-adjusted ORs (95%CI) of NAFLD across the categories of tooth missing (0, 1-, 3- and ≥6) were as follows: 1.00, 1.04 (0.93-1.15), 1.08 (0.93-1.26) and 1.38 (1.09-1.76) (trend test P=0.030) in males; 1.00, 0.96 (0.82-1.12), 1.11 (0.91-1.35) and 1.22 (0.90-1.64) (trend test P=0.450) in females. Conclusion: The number of missed teeth was positively associated with a higher prevalence rate of NAFLD in males with over 6 teeth missed, but not in females.

[Necessity and normalization of imaging examination on temporomandibular disorders]

Diagnosis and treatment of temporomandibular disorders (TMD) have been paid attention greatly by dentists in clinic. Imaging is the most important method for dentists to diagnose TMD correctly. Cone-beam CT (CBCT) and MRI have been demonstrated superiority and necessity that contribute to correctly diagnosis, early diagnosis and follow-up patients. However, there are several significant problems required for professional agreement: the procedures for CBCT and MRI examination need to be standardized; dentists have to be trained regularly for the knowledge of the imaging diagnosis of TMD; it should be emphasized that patient history and clinical examination are much more important for diagnosis, imaging is only a supplement and should not be over used.

[Characteristics of MRI and associated pathological features of the condylar cyst like lesions in temporomandibular joint]

Objective: To analyze the MRI characteristics and pathological features of the condylar cyst like lesions in temporomandibular joint (TMJ). Methods: The study was conducted retrospectively on TMJ images from 14 patients (2 males, 12 females, aged 10-71) who underwent MRI examinations, from January 2015 to December 2017 at Center for TMD and Orofacial Pain, Peking University School and Hospital of Stomatology including 2 patients with pathological results. The signals of the lesion, condylar bone and disc-condyle relationship were evaluated. Results: Cyst like lesions of 15 condyles from 14 patients were analyzed. All of the lesions showed hypersignal on T2WI (12/12), while most of them showed hypersignal on T1WI (8/11) and PDWI (11/12). Mostly the lesions were surrounded by hyposignal linear margin (12/15), with normal condylar bone signal (13/15). Disk displacement with reduction was discovered in 3 joints, while disk displacement without reduction was discovered in 8 joints and 4 joints had normal disk-condyle relationships. The pathological components of cyst like lesions included cartilage, loose connective tissue, hemorrhage and bone tissue. Conclusions: Differed from those of large joints like hips or knees, MRI characteristics of cyst like lesions of condyle in TMJ exhibited hypersignal imaging in both T1WI and T2WI, indicating that the components of cyst like lesions included granulation tissue, not fluid.

Comprehensive human cell-type methylation atlas reveals origins of circulating cell-free DNA in health and disease

Methylation patterns of circulating cell-free DNA (cfDNA) contain rich information about recent cell death events in the body. Here, we present an approach for unbiased determination of the tissue origins of cfDNA, using a reference methylation atlas of 25 human tissues and cell types. The method is validated using in silico simulations as well as in vitro mixes of DNA from different tissue sources at known proportions. We show that plasma cfDNA of healthy donors originates from white blood cells (55%), erythrocyte progenitors (30%), vascular endothelial cells (10%) and hepatocytes (1%). Deconvolution of cfDNA from patients reveals tissue contributions that agree with clinical findings in sepsis, islet transplantation, cancer of the colon, lung, breast and prostate, and cancer of unknown primary. We propose a procedure which can be easily adapted to study the cellular contributors to cfDNA in many settings, opening a broad window into healthy and pathologic human tissue dynamics.

The methylation status of circulating cell-free DNA (cfDNA) can be informative about recent cell death events. Here the authors present an approach to determine the tissue origins of cfDNA, using a reference methylation atlas of 25 human tissues and cell types, and find that cfDNA from patients reveals tissue contributions that agree with clinical findings.

[The images of osteoarthrosis associated with anterior disc displacement without reduction detected by cone-beam CT]

Objective: To analyze the radiological characteristics of the condylar bone in patients with anterior disc displacement without reduction of temporomandibular joint using cone-beam CT (CBCT), and to further investigate the clinical factors possibly associated with the early-stage osteoarthritic changes. Methods: Two hundred and four individuals (≤30 years old) diagnosed as unilateral anterior disc displacement without reduction (disease duration≤1 year) were recruited. CBCT images of bilateral condyles were independently evaluated by two assessors and documented. Correlation between the early-stage osteoarthritic (OA) changes and gender, age, disease duration and mouth opening were analyzed using SPSS 21.0 software. Results: About sixty percent were presented with OA changes in the symptomatic joints, and most of them (47.1%) (96/204) were early-stage OA changes characterized by loss of continuity of articular cortex (Ⅰ) and/or surface erosion (Ⅱ). Logistics regression analyses indicated that disease duration (P =0.000) and mouth opening (P =0.002) were correlated significantly with early-stage OA changes. Conclusions: Disc displacement without reduction was closely related to OA occurrence. OA changes occurred in more than half of the patients after one month of the joint locked and more possibly in patients with increased mouth opening.

Impact of fat mass and distribution on lipid turnover in human adipose tissue

Differences in white adipose tissue (WAT) lipid turnover between the visceral (vWAT) and subcutaneous (sWAT) depots may cause metabolic complications in obesity. Here we compare triglyceride age and, thereby, triglyceride turnover in vWAT and sWAT biopsies from 346 individuals and find that subcutaneous triglyceride age and storage capacity are increased in overweight or obese individuals. Visceral triglyceride age is only increased in excessively obese individuals and associated with a lower lipid removal capacity. Thus, although triglyceride storage capacity in sWAT is higher than in vWAT, the former plateaus at substantially lower levels of excess WAT mass than vWAT. In individuals with central or visceral obesity, lipid turnover is selectively increased in vWAT. Obese individuals classified as ‘metabolically unhealthy' (according to ATPIII criteria) who have small subcutaneous adipocytes exhibit reduced triglyceride turnover. We conclude that excess WAT results in depot-specific differences in lipid turnover and increased turnover in vWAT and/or decreased turnover in sWAT may result in metabolic complications of overweight or obesity.

Lipid turnover in tissues can be calculated from ratios of different carbon isotopes. Here the authors use this approach to study lipid turnover in two distinct adipose tissue depots and find that, in obese individuals, visceral fat is more lipolytic than subcutaneous fat.

[Changes of productions of energy metabolism in masseter of rats induced by occlusal interference]

OBJECTIVE

To investigate the effect of occlusal interference on the energy metabolism of masticatory muscle by studying the changes of adenosine triphosphate (ATP), adenosine diphosphate (ADP), inosine monophosphate (IMP), phosphocreatine, creatine, lactate and pH level in masseter muscles of rats after occlusal interference.

METHODS

Fifty male Sprague-Dawley rats were randomly assigned into experimental group (n=40) and control group (n=10). In experimental group, 0.4 mm thick metal crown was cemented to the upper right first molar of the rat, and maintained for 3, 7, 10, 14 d separately (n=10 for each time point). No occlusal interference was applied for control group. Bilateral masseter muscles of all the rats were acquired under general anesthesia. The samples of 5 rats in each group were fully homogenized with 0.4 mol/L perchlorate (10 mL/g). The homogenates were centrifuged, filtered and analyzed for ATP, ADP, IMP, phosphocreatine, creatine and lactate content by high performance liquid chromatography. The other samples in each group were mixed with homogenates containing 5 mmol/L sodium iodoacetate (10 mL/g), then homogenized and measured for pH value by pH meter in thermostatic water bathunder 37 degrees centigrade.

RESULTS

Compared with control group, ATP content in bilateral masseter of the rats increased 3 d after occlusal interference [right side:(5.36±0.13) μmol/g,left side:(5.77±0.25) μmol/g] (P<0.05), and back to normal on 7, 10 and 14 d. There was an increase in IMP [right side:(0.21±0.03) μmol/g,left side:(0.19±0.03) μmol/g]and creatine content [right side:(24.76±2.94) μmol/g,left side:(27.75±2.23) μmol/g]in bilateral masseter of the rats 7 d after occlusal interference (P<0.05) and no difference was detected on 3, 10, and 14. Phosphocreatine content in bilateral masseter started to decline 7 d after occlusal interference and maintained the low level on 10 and 14 d [right side:(10.70±0.71) μmol/g, (11.57±0.52) μmol/g, (10.74±1.39) μmol/g, left side:(10.05±0.57) μmol/g, (10.75±1.12)μmol/g, (10.61±1.15) μmol/g](P<0.05). No change of ADP, lactate or pH level in bilateral muscles of the rats after occlusal interference was observed (P>0.05).

CONCLUSION

Occlusal interference influences the content of energy metabolites in masticatory muscle of rats, which may be related to the pathological process of masticatory muscles induced by occlusal interference, such as muscle pain, dysfunction and altered fiber architecture.

[The prevalence of temporomandibular disorder symptoms in 898 university students and its relationship with psychological distress and sleep quality]

OBJECTIVE

To investigate the prevalence of temporomandibular disorders(TMD) symptoms, psychological distress and sleep quality in a population of Chinese university students, and discuss the relationship between psychological distress, sleep quality and TMD symptoms.

METHODS

A total of 898 stomatological university students from 5 Chinese universities(342 males and 556 females with a mean age of 20.5 years) were included in the study. Self-reported TMD symptoms using diagnostic criteria for temporomandibular disorders symptom questionnaire were collected. Depression, anxiety and stress scales-21(DASS-21) and Pittsburgh sleep quality index(PSQI) were used to measure psychological distress and sleep quality.

RESULTS

61.9% (556/898) of the students had TMD symptoms. The most common symptoms were pain and clicking of joint, with a prevalence of 42.3% (380/898) and 34.2% (307/898), respectively. The prevalence of depression, anxiety, stress and sleep quality among the students who had TMD symptoms was 33.5%(186/556), 63.1%(351/556), 29.5%(164/556) and 30.2%(243/556), respectively, which was significantly higher than those who had no TMD symptoms(24.3% [83/342], 48.5% [166/342], 21.6%[74/342] and 21.9%[75/342])(P<0.05). Stepwise logistic regression analysis demonstrated that anxiety (OR 1.57, 95%CI 1.14-2.15) and female(OR 1.57, 95%CI 1.19-2.08) were possible risk indicators for TMD symptoms(P<0.05).

CONCLUSIONS

Chinese university students reported a high prevalence of TMD symptoms, which may have a correlation with psychological distress symptoms such as anxiety.

[Disturbed sleep, anxiety and stress are possible risk indicators for temporomandibular disorders with myofascialpain]

OBJECTIVE

To explore the relationship betweensleep/psychological distress and temporomandibular disorders (TMD) and to discuss the possibility of disturbed sleep and psychological distress as risk indicators in relation to TMD in a Chinese population.

METHODS

The standardized and validated self-reported Chinese version questionnaires including Pittsburgh sleep quality index (PSQI) and depression, anxietyandstress scales-21 (DASS-21) were used to measure sleep quality and psychological distress. A total of 755 TMD patients (172 males and 583 females)with a mean age (29.99 ± 13.60) years were included in the study. The patients were divided into 7 diagnostic groups based on the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD), including Group I(exclusively myofascial pain), Group II(exclusively disc displacement), Group III (exclusively arthralgia or degenerative joint disease), Group IV (myofascial pain plus disc displacement), Group V (myofascial pain plus arthralgia or degenerative joint disease), Group VI (disc displacement plus arthralgia or degenerative joint disease) and Group VII (myofascial pain plus disc displacement plus arthralgia or degenerative joint disease). For statistical analysis, the patients were subsequently grouped into those with (181 patients) and without (574 patients) myofascial pain. Chi-square tests, independent-samples t test, partial correlation as well as stepwise Logistic regression analysis were used to analyze the data, using software SPSS 20.0 and P<0.05 was of significance.

RESULTS

The prevalence of moderate to (extremely) severe disturbed sleep and psychological distress was significantly higher in the myofascial pain group (27.1%, 28.7%, 60.8% and 32.0%) than in the non-myofascial pain group (disc displacement and arthralgia or degenerative joint disease, 11.1%, 10.1%, 27.4% and 11.0%, P<0.05).The comorbidity of self-reported disturbed sleep and psychological distress was significantly higher in the myofascial pain patients than those without myofascial pain (P<0.05). Stepwise logistic regression analysis demonstrated that disturbed sleep (OR=1.74), more specifically, subjective sleep quality (OR=1.69) and sleep disturbance (OR=1.63) respectively, anxiety (OR=3.14) and stress (OR=2.15) were possible risk indicators for myofascial pain, and the results were still significant even after controlling for age, sex, educational level, disease duration, sleep quality, depression, anxiety and stress respectively (P<0.05).

CONCLUSION

Disturbed sleep and psychological distress symptoms are common in TMD patients. Disturbed sleep, anxiety and stress are possible risk indicators for myofascial pain, compared with disc displacement and arthralgia or degenerative joint diseases.

[Disturbed sleep, anxiety and stress are possible risk indicators for temporomandibular disorders with myofascialpain]

OBJECTIVE

To explore the relationship betweensleep/psychological distress and temporomandibular disorders (TMD) and to discuss the possibility of disturbed sleep and psychological distress as risk indicators in relation to TMD in a Chinese population.

METHODS

The standardized and validated self-reported Chinese version questionnaires including Pittsburgh sleep quality index (PSQI) and depression, anxietyandstress scales-21 (DASS-21) were used to measure sleep quality and psychological distress. A total of 755 TMD patients (172 males and 583 females)with a mean age (29.99 ± 13.60) years were included in the study. The patients were divided into 7 diagnostic groups based on the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD), including Group I(exclusively myofascial pain), Group II(exclusively disc displacement), Group III (exclusively arthralgia or degenerative joint disease), Group IV (myofascial pain plus disc displacement), Group V (myofascial pain plus arthralgia or degenerative joint disease), Group VI (disc displacement plus arthralgia or degenerative joint disease) and Group VII (myofascial pain plus disc displacement plus arthralgia or degenerative joint disease). For statistical analysis, the patients were subsequently grouped into those with (181 patients) and without (574 patients) myofascial pain. Chi-square tests, independent-samples t test, partial correlation as well as stepwise Logistic regression analysis were used to analyze the data, using software SPSS 20.0 and P<0.05 was of significance.

RESULTS

The prevalence of moderate to (extremely) severe disturbed sleep and psychological distress was significantly higher in the myofascial pain group (27.1%, 28.7%, 60.8% and 32.0%) than in the non-myofascial pain group (disc displacement and arthralgia or degenerative joint disease, 11.1%, 10.1%, 27.4% and 11.0%, P<0.05).The comorbidity of self-reported disturbed sleep and psychological distress was significantly higher in the myofascial pain patients than those without myofascial pain (P<0.05). Stepwise logistic regression analysis demonstrated that disturbed sleep (OR=1.74), more specifically, subjective sleep quality (OR=1.69) and sleep disturbance (OR=1.63) respectively, anxiety (OR=3.14) and stress (OR=2.15) were possible risk indicators for myofascial pain, and the results were still significant even after controlling for age, sex, educational level, disease duration, sleep quality, depression, anxiety and stress respectively (P<0.05).

CONCLUSION

Disturbed sleep and psychological distress symptoms are common in TMD patients. Disturbed sleep, anxiety and stress are possible risk indicators for myofascial pain, compared with disc displacement and arthralgia or degenerative joint diseases.

Role of TRPV1 and ASIC3 channels in experimental occlusal interference-induced hyperalgesia in rat masseter muscle

BACKGROUND

Masticatory muscle pain may occur following immediate occlusal alteration by dental treatment. The underlying mechanisms are poorly understood. Transient receptor potential vanilloid-1 (TRPV1) and acid-sensing ion channel-3 (ASIC3) mediate muscle hyperalgesia under various pathologic conditions. We have developed a rat model of experimental occlusal interference (EOI) that consistently induces mechanical hyperalgesia in jaw muscles. Whether TRPV1 and ASIC3 mediate this EOI-induced hyperalgesia is unknown.

METHODS

Rat model of EOI-induced masseter hyperalgesia was established. Real-time polymerase chain reaction, Western blot and retrograde labelling combined with immunofluorescence were performed to evaluate the modulation of TRPV1 and ASIC3 expression in trigeminal ganglia (TGs) and masseter afferents of rats after EOI. The effects of intramuscular administration of TRPV1 and ASIC3 antagonists on the EOI-induced hyperalgesia in masseter muscle were examined.

RESULTS

After EOI, gene expressions and protein levels of TRPV1 and ASIC3 in bilateral TGs were up-regulated. The percentage of ASIC3- (but not TRPV1-) positive neurons in masseter afferents increased after EOI. More small-sized and small to medium-sized masseter afferents expressed TRPV1 and ASIC3 separately following EOI. These changes peaked at day 7 and then returned to original status within 10 days after EOI. Intramuscular administration of the TRPV1 antagonist AMG-9810 partially reversed this mechanical hyperalgesia in masseter muscle. No improvement was exhibited after administration of the ASIC3 antagonist APETx2. Co-injection of AMG-9810 and APETx2 enhanced the effect of AMG-9810 administration alone.

CONCLUSIONS

Peripheral TRPV1 and ASIC3 contribute to the development of the EOI-induced mechanical hyperalgesia in masseter muscle.

Long-lasting inflammation and long-term hyperalgesia after subcutaneous formalin injection into the rat hindpaw

Subcutaneous formalin injection is widely used as a nociceptive stimulus in the rat. This procedure evokes overt behaviors that last about 90 minutes. However, little is known about the duration of paw inflammation and alterations in pain sensitivity to noxious stimuli after 2 hours. We studied the nociceptive responses to thermal and mechanical stimuli 2 hours to 4 weeks after formalin injection into the dorsal or plantar side of the hindpaw. Thirty-two adult male Sprague-Dawley rats were divided into 3 groups: In group I, 50 microL of 5% formalin was injected into the plantar side (n = 12); in group II, 50 microL of 5% formalin was injected into the dorsal side (n = 12); in group III, 50 microL saline was injected into the dorsal or plantar side of the hindpaw (n = 8). Nociceptive responses to thermal and mechanical stimuli applied to the dorsal or plantar surfaces of the injected and the contralateral hindpaws were recorded. The injection of formalin into the rat's hindpaw produced a hypoalgesic region around the injection site. In contrast, hyperalgesic responses to thermal and mechanical stimulation were induced on the opposite surface of the injected hindpaw as well as in the contralateral noninjected hindpaw. The hyperalgesic responses, which were observed 2 hours after formalin administration, were enhanced 1 to 3 days after injection and lasted 3 to 4 weeks. These results suggest that peripheral inflammation after subcutaneous formalin injection produces a long-lasting sensitization. Possible mechanisms for these changes in nociception are discussed.

Relationship between nociceptor activity, peripheral edema, spinal microglial activation and long-term hyperalgesia induced by formalin

To determine whether initial nociceptive inputs caused by subcutaneous injection of formalin into the hindpaw are necessary and/or sufficient for allodynic behavior and microglial activation observed at one week following behavior, we examined Sprague-Dawley rats under five test conditions. Test condition 1. Formalin alone group (six rats), 5% formalin was injected subcutaneously into the dorsal side of the right hind paw. Test condition 2. Bupivacaine/Formalin group (six rats), bupivacaine was injected into the ankle area and into the site of formalin injection 10 min before formalin injection. Test condition 3. Saline/Formalin group (six rats), saline was injected 10min before formalin in the same manner as bupivacaine. Test condition 4. Formalin/Bupivacaine group 1 (six rats), bupivacaine was injected 10 min after formalin. Test condition 5. Formalin/Bupivacaine group 2 (six rats), bupivacaine was injected similarly 1h after formalin. The magnitude of paw edema and paw withdrawal thresholds to mechanical stimuli applied to the plantar surface of the injected paw and on the dorsal surface of the contralateral side were evaluated prior to and one week after formalin injection. The lumbar spinal cord was immunohistochemically processed at one week to assess the expression of a marker for activated microglia. The results showed: (i) pre-treatment with bupivacaine blocked both phases of formalin-evoked pain behaviors and the mechanical allodynia that developed one week post-formalin injection, but did not block microglial activation; (ii) treatment with bupivacaine 1h after formalin injection reduced paw edema and prevented skin ulceration, but one week allodynia and microglial activation were still present; and (iii) prolonged spinal microglial activation was not dependent on acute formalin-induced nociceptor activity, but was strongly associated with the amount of tissue destruction. Our studies suggest that: (i) the central sensitization associated with the phase II of formalin-evoked behaviors and spinal microglial activation are both necessary to permit the development of the long-term hyperalgesia produced by the subcutaneous administration of formalin into the rat's hindpaw; and (ii) acute nociceptive inputs following formalin injection are not necessary for central microglial activation that may be triggered by nerve damage or prolonged signals from peripherally inflamed tissue

Studies on contributing factors in temporomandibular disorders

OBJECTIVE

To better understand the pathogenesis of TMD by studying microtrauma of the temporomandibular joint (TMJ), immune responses within TMJ, and psychosocial factors of the past ten years.

METHODS

Condyle and disc movements from 38 patients with temporomandibular disorders (TMD) were observed with the use of videotape recording and soundtape recording techniques after TMJ arthrography. Pathological changes following occlusal trauma were examined using an animal model. Immune complexes in condyle cartilage; antibody to collagen II; and cytokines such as interleukin 1, tumor necrosis factor, and interleukin 6 were detected in synovial fluid of TMD. Psychosocial characteristics were analyzed with the Minnesota Multiphasic Personality Inventory (MMPI) of 80 TMD patients and the Life Events Experience Survey (LEES) of 42 TMD patients.

RESULTS

Persistent and recurrent microtrauma did exist within joints of TMD patients, caused by occlusal trauma and occlusal interference. Occlusal trauma in animals could induce condyle and disc degenerative changes that are similar to the findings in TMJ osteoarthrosis patients. Sequestered antigens within cartilage could be exposed to the immune system after joint degeneration. Humoral and cellular immune responses did exist within TMJ and played an important role in the pathogenesis of TMD. Forty percent of TMD patients suffered from psychosomatic disorders, significantly more than in the healthy control.

CONCLUSION

Microtrauma of TMJ, immune responses within TMJ, psychosocial factors, and anatomical structures of the TMJ itself are the four main contributing factors of TMD. Possible mechanisms of the interactions of the four factors are presented, and principles of preventing and treating TMD are also suggested.

Determination of interleukin-1 receptor antagonist, interleukin-10, and transforming growth factor-beta1 in synovial fluid aspirates of patients with temporomandibular disorders

PURPOSE

This study was undertaken to examine the presence of interleukin-1 receptor antagonist (IL-1ra), IL-10, and transforming growth factor-beta1 (TGF-beta1) in the synovial fluid (SF) lavage specimens of patients with temporomandibular disorders (TMDs).

PATIENTS AND METHODS

Synovial fluid lavage specimens were obtained from 14 temporomandibular joints (TMJs) of 12 patients with TMJ internal derangement (ID) and 17 TMJs of 15 patients with TMJ osteoarthritis (OA). Seven synovial fluid lavage samples of TMJs of four asymptomatic donors served as normal controls. The concentrations of IL-1ra, IL-10, and TGF-beta1 were detected with sensitive and specific sandwich enzyme-linked immunosorbent assay (sandwich-ELISA).

RESULTS

IL-1ra, IL-10, and TGF-beta1 in all the normal controls were undetectable. IL-1ra concentrations were 175.78 +/- 52.43 pg/mL in the patients with TMJ ID and 187.85 +/- 59.51 pg/mL in those with TMJ OA. IL-10 was undetectable in all the TMJ ID and OA samples. The concentration of TGF-beta1 in TMJ ID patients (47.93 +/- 88.25 pg/mL) was significantly less than in patients with TMJ OA (143.61 +/- 108.00 pg/mL) (P < .01).

CONCLUSION

The results suggest that deficiencies of IL-1ra, IL-10, and TGF-beta1 probably play an important role in the cause and pathogenesis of TMJ ID and OA.

Microglial reactions after subcutaneous formalin injection into the rat hind paw

Microglia in primary afferent projection territories are activated and proliferate after peripheral nerve injury. However, it is not known whether stimulation of peripheral nerves by noxious stimuli applied to their receptive fields activates microglial cells in the spinal cord. This study was designed to investigate the response of microglia in the lumbar spinal cord and in the brainstem to a tonic noxious stimulus. Thirty-two male Sprague-Dawley rats received subcutaneous injections of 5% formalin (50 microliter) into the plantar surface of the right hind paw, and 24 rats were injected with 50 microliter saline as a control. The lumbar spinal cord and brainstem were evaluated for immunoreactivity (IR) to complement receptor C3bi (monoclonal antibody OX-42) and major histocompatibility complex class II (monoclonal antibody OX-6) on postinjection hours 0, 2, 4 and 8 and days 1, 3, 7, 14 and 28. A qualitative and quantitative increase of OX-42-IR microglial cells were observed in the medial portion of the dorsal horn and in the gracile nucleus of the brainstem on the side ipsilateral to the formalin injection, starting on days 1-3 and peaking on day 7 postinjection. OX-6-positive cells were scattered both in gray and white matter, but no difference was detected between the two sides of the spinal cord or between formalin-injected and control animals. This is the first study that reports that subcutaneous injection of formalin into the rat's hind paw induces microglial activation in the spinal cord as well as in the brainstem. Although we have not determined whether these responses result from nociceptor activity, peripheral inflammation, or degeneration of primary afferents and/or central neurons, this method provides a simple, effective and stable animal model that will permit the future study of the mechanisms that contribute to microglial activation and its pathophysiological consequences.

[Tumor necrosis factor in synovial fluids of temporomandibular joint dysfunction syndrome]

With the MTT tetrazolium WEHI 164 clone 13 cell cytotoxicity assay, we measured TNF alpha (tumor necrosis factor) activity in synovial fluids of TMJDS (Temporomandibular joint dysfunction syndrome). We found no detected TNF alpha level from 5 patients with muscle dysfunction, raised TNF alpha levels from 5 of 11 patients with internal derangement and from 9 of 11 patients with organic destruction (osteoarthritis). The findings of biologically active TNF alpha in synovial fluids of TMJDS suggest that TNF alpha may play a role in the pathogenesis of TMJDS.

[Clinical application of sialography with the time-pressure curve monitored]

Sialography with the time-pressure curve monitored in 66 abnormal parotids was compared with the manual injection technique. The results are: 1. The new procedure makes sialogram image superior, avoids gland parenchymal overfilling, finds the causes of failure promptly, and eliminates the pain and other side effects. 2. Shape of the time-pressure curve and the value of the injection may act as an indicator in differential diagnosis. The curve in Sjögren's syndrome is specific and the injection pressure is obviously higher than that in normal (P < 0.01). In Sialosis the injection pressure is much lower than in normal (P < 0.01).

[Sialography with the time-pressure curve monitors]

A new procedure was established for sialography that it is monitored by the time-pressure curve during automatically continuous infusion of Urografin 76%. Shape of the curves in 10 normal parotid glands shows firstly the injection pressure rises to the highest peak rapidly, then falls slowly. Eventually the pressure remains constant despite continued infusion. At that time, mean pressure is 7.3kPa (range is 5.3-9.3 kPa). 3 radiographs are taken at 1 minute intervals from the time of the injection pressure beginning to keep constant. The result is that the second sialogram image is the most satisfied.