Characteristics of painful temporomandibular disorders and their influence on jaw functional limitation and oral health-related quality of life.

BACKGROUND: There is limited knowledge about the impact of painful temporomandibular disorders (TMDs) and pain characteristics on jaw functional limitation and oral health-related quality of life (OHRQoL) in TMD patients. OBJECTIVES: The influence of painful TMDs and pain characteristics on jaw functional limitation and OHRQoL was investigated. Inter-relationships between limitation in jaw function and various OHRQoL domains, along with facial pain attributes predicting impaired jaw function and diminished OHRQoL were also examined. METHODS: TMD patients were recruited from a university-based hospital. A comprehensive questionnaire comprising demographic variables, the DC/TMD Symptom Questionnaire, Graded Chronic Pain Scale, Jaw Functional Limitation Scale-8 (JFLS-8) and Oral Health Impact Profile-TMD (OHIP-TMD) was administered. Participants underwent a protocolized physical examination, and TMD diagnoses were determined utilising the DC/TMD algorithms. Participants were subsequently stratified into intra-articular/pain-related/combined TMD groups, as well as no TMD pain, acute/chronic pain and low/high-intensity pain groups. Data were assessed using non-parametric and hierarchical linear regression analyses (α = .05). RESULTS: The final sample consisted of 280 participants (mean age 31.2 (SD 11.8) years; 79.3% women). Significant differences in pain characteristics, JFLS-8, and global OHIP scores were observed across the various TMD subtypes, pain chronicity and pain intensity categories. Pain intensity and pain-related interference exhibited moderate correlations with JFLS-8 and global OHIP scores (rs = 0.53-0.60). Moderate associations were also noted between JFLS-8 and global OHIP, as well as most OHIP domains (rs = 0.42-0.64). Both jaw functional limitation and OHRQoL were predicted by sex, pain intensity and pain-related interference. CONCLUSIONS: Sex, pain intensity and pain-related interference are key determinants for both impaired jaw function and diminished OHRQoL, with pain-related interference exerting a more pronounced effect.

Descending serotonergic modulation from rostral ventromedial medulla to spinal trigeminal nucleus is involved in experimental occlusal interference-induced chronic orofacial hyperalgesia.

BACKGROUND: Dental treatment associated with unadaptable occlusal alteration can cause chronic primary myofascial orofacial pain. The serotonin (5-HT) pathway from the rostral ventromedial medulla (RVM) exerts descending modulation on nociceptive transmission in the spinal trigeminal nucleus (Sp5) and facilitates chronic pain. The aim of this study was to investigate whether descending 5-HT modulation from the RVM to the Sp5 is involved in the maintenance of primary myofascial orofacial hyperalgesia after persistent experimental occlusal interference (PEOI) or after delayed removal of experimental occlusal interference (REOI). METHODS: Expressions of 5-HT3A and 5-HT3B receptor subtypes in the Sp5 were assessed by immunofluorescence staining and Western blotting. The release and metabolism of 5-HT in the Sp5 were measured by high-performance liquid chromatography. Changes in the pain behavior of these rats were examined after specific pharmacologic antagonism of the 5-HT3 receptor, chemogenetic manipulation of the RVM 5-HT neurons, or selective down-regulation of 5-HT synthesis in the RVM. RESULTS: Upregulation of the 5-HT3B receptor subtype in the Sp5 was found in REOI and PEOI rats. The concentration of 5-HT in Sp5 increased significantly only in REOI rats. Intrathecal administration of Y-25130 (a selective 5-HT3 receptor antagonist) dose-dependently reversed the hyperalgesia in REOI rats but only transiently reversed the hyperalgesia in PEOI rats. Chemogenetic inhibition of the RVM 5-HT neurons reversed the hyperalgesia in REOI rats; selective down-regulation of 5-HT in advance also prevented the development of hyperalgesia in REOI rats; the above two manipulations did not affect the hyperalgesia in PEOI rats. However, chemogenetic activation of the RVM 5-HT neurons exacerbated the hyperalgesia both in REOI and PEOI rats. CONCLUSIONS: These results provide several lines of evidence that the descending pathway from 5-HT neurons in the RVM to 5-HT3 receptors in the Sp5, plays an important role in facilitating the maintained orofacial hyperalgesia after delayed EOI removal, but has a limited role in that after persistent EOI.

Deep learning-based evaluation of the relationship between mandibular third molar and mandibular canal on CBCT.

OBJECTIVES: The objective of our study was to develop and validate a deep learning approach based on convolutional neural networks (CNNs) for automatic detection of the mandibular third molar (M3) and the mandibular canal (MC) and evaluation of the relationship between them on CBCT. MATERIALS AND METHODS: A dataset of 254 CBCT scans with annotations by radiologists was used for the training, the validation, and the test. The proposed approach consisted of two modules: (1) detection and pixel-wise segmentation of M3 and MC based on U-Nets; (2) M3-MC relation classification based on ResNet-34. The performances were evaluated with the test set. The classification performance of our approach was compared with two residents in oral and maxillofacial radiology. RESULTS: For segmentation performance, the M3 had a mean Dice similarity coefficient (mDSC) of 0.9730 and a mean intersection over union (mIoU) of 0.9606; the MC had a mDSC of 0.9248 and a mIoU of 0.9003. The classification models achieved a mean sensitivity of 90.2%, a mean specificity of 95.0%, and a mean accuracy of 93.3%, which was on par with the residents. CONCLUSIONS: Our approach based on CNNs demonstrated an encouraging performance for the automatic detection and evaluation of the M3 and MC on CBCT. Clinical relevance An automated approach based on CNNs for detection and evaluation of M3 and MC on CBCT has been established, which can be utilized to improve diagnostic efficiency and facilitate the precision diagnosis and treatment of M3.

Comparison of psychological states and oral health-related quality of life of patients with differing severity of temporomandibular disorders.

BACKGROUND: Studies on temporomandibular disorder (TMD) severity in patient populations are scarce. OBJECTIVES: This study sought to compare the psychological states and oral health-related quality of life (OHRQoL) among patients with differing TMD severity. METHODS: Adult patients (≥18 years old) with and without (controls) TMDs were recruited from the TMD/oro-facial pain centre and prosthodontics department, respectively. The presence and severity of TMDs were established with the Fonseca Anamnestic Index (FAI), and TMD diagnoses were confirmed with the Diagnostic Criteria for TMDs (DC/TMD). Psychological states and OHRQoL were examined with the Depression, Anxiety, Stress Scales-21 (DASS-21) and Oral Health Impact Profile for TMDs (OHIP-TMD). Data were subjected to chi-square, Kruskal-Wallis/Mann-Whitney U tests and Spearman's correlation (α = .05). RESULTS: A total of 961 participants with a mean age of 32.99 ± 13.14 years (71.19% women) were assessed. Frequencies of the various TMD categories were as follows: no TMD/controls (12.07%), mild TMD (24.56%), moderate TMD (40.37%) and severe TMD (23.00%). The three most common TMD-related symptoms were TMJ noises, mouth opening difficulty and muscle pain. Participants with moderate/severe TMD presented a higher proportion of intra-articular and/or combined disorders. They reported significantly higher levels of depression, anxiety, stress and poorer OHRQoL than their counterparts with no/mild TMD (p < .001). Moderate-to-strong correlations were observed between FAI and DASS-21/OHIP-TMD scores (rs = 0.42-0.72). CONCLUSIONS: Patients with moderate/severe TMD had significantly higher levels of psychological disturbance and poorer OHRQoL. As OHRQoL and psychological states are correlated, psychological well-being must be considered when managing patients with moderate/severe TMDs.

Astrocytes in the rostral ventromedial medulla contribute to the maintenance of oro-facial hyperalgesia induced by late removal of dental occlusal interference.

BACKGROUND: Astrocytes in the rostral ventromedial medulla (RVM) contribute to descending pain modulation, but their role in oro-facial pain induced by persistent experimental dental occlusal interference (PEOI) or following EOI removal (REOI) is unknown. OBJECTIVE: To explore the involvement of RVM astrocytes in PEOI-induced oro-facial hyperalgesia or its maintenance following REOI. METHODS: Male rats were randomly assigned into five groups: sham-EOI, postoperative day 6 and 14 of PEOI (PEOI 6 d and PEOI 14 d), postoperative day 6 following REOI on day 3 (REOI 3 d) and postoperative day 14 following REOI on day 8 (REOI 8 d). The nociceptive head withdrawal threshold (HWT) and activities of RVM ON- or OFF-cells were recorded before and after intra-RVM astrocyte gap junction blocker carbenoxolone (CBX) microinjection. RVM astrocytes were labelled immunohistochemically with glial fibrillary acidic protein (GFAP) and analysed semi-quantitatively. RESULTS: Persistent experimental dental occlusal interference-induced oro-facial hyperalgesia, as reflected in decreased HWTs, was partially inhibited by REOI at day 3 but not at day 8 after EOI placement. Increased GFAP-staining area occurred only in REOI 8 d group in which CBX could inhibit the maintained hyperalgesia; CBX was ineffective in inhibiting hyperalgesia in PEOI 14 d group. OFF-cell activities showed no change, but the spontaneous activity and responses of ON-cells were significantly enhanced that could be suppressed by CBX in REOI 8 d group. CONCLUSION: Rostral ventromedial medulla astrocytes may not participate in PEOI-induced oro-facial hyperalgesia or hyperalgesia inhibition by early REOI but are involved in the maintenance of oro-facial hyperalgesia by late REOI.

Condylar repair and regeneration in adolescents/young adults with early-stage degenerative temporomandibular joint disease: A randomised controlled study.

BACKGROUND: Anterior repositioning splint (ARS) can facilitate regenerative condylar remodelling. OBJECTIVE: To determine the effect of ARS on osseous condylar changes in adolescents/young adults with early-stage degenerative joint disease (DJD). METHODS: Sixty-nine patients with early-stage temporomandibular joint (TMJ) DJD based on the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) and cone beam computed tomography (CBCT) imaging were recruited and randomly allocated to two treatment groups: (a) conservative therapy with ARS and (b) conservative therapy without ARS. Subjects with acute TMJ closed-lock had their displaced discs physically reduced by mandibular manipulation prior to ARS therapy. Clinical and CBCT data of 59 patients (86.4% females, mean age 17.95 ± 4.53 years, 67 joints) were attained pre- and at 6 or 12 months post-treatment. Osseous changes after treatment were categorised into (a) progressed, (b) unchanged, (c) repaired (remodelled without new bone formation) and (d) regenerated (remodelled with new bone formation). Statistical analysis including chi-square test, independent samples t test or Mann-Whitney U test was conducted. RESULTS: About 85.5% of patients (59/69) completed the study, with 28 subjects (32 joints) in the splint group and 31 (35 joints) in the control group. The occurrence of condylar repair and regeneration was significantly higher with ARS (78.1%/[25/32] of joints) when compared to control group (48.6%/[17/35]) (P < 0.05). Moreover, condylar regeneration was exclusively observed in 50%/(16/32) of joints with ARS. For the 14 joints in splint group that received physical TMJ closed-lock reduction, 85.7%/(12/14) exhibited condylar regeneration. The splint group (3.1%/[1/32]) also had significantly lower incidence of progressive TMJ degeneration than the control (37.1%/[13/35]) (P < 0.001). CONCLUSION: Condylar repair and regeneration in early-stage TMJ DJD are possible, and ideal spatial disc-condyle relationship appears important. The possibility of restoring TMJ form/structure by ARS therapy presents an attractive area of new basic science and clinical research (Bone defect repair in early osteoarthrosis of temporomandibular joint by joint distraction therapy: A randomized controlled trial/ChiCTR-TRC-14005172).

[Three-dimensional evaluation of condylar morphology remodeling after orthognathic surgery in mandibular retrognathism by cone-beam computed tomography].

OBJECTIVE: To evaluate the effect of orthognathic surgery on condylar morphology changes by comparing three-dimension surface reconstructions of condyles using cone-beam computed tomography (CBCT) data. METHODS: In the study, 18 patients with mandible retrognathism deformities were included and CBCT data of 36 temporomandibular joints were collected before surgery and 12 months after surgery. Condyles were reconstructed and superimposed pre- and post-operatively to compare the changes of condylar surfaces. One-sample t test and χ2 test were performed for the analysis of three-dimension metric measurement and condylar head remodeling signs. P<0.05 was considered significant. RESULTS: The root-mean-square (RMS) of condylar surface changes before and after the surgery was (0.37±0.11) mm, which was significant statistically (P<0.05). The distribution of condylar remodeling signs showed significant difference (P<0.05). Bone resorption occurred predominantly in the posterior area of condylar head and bone formation occurred mainly in the anterior area. CONCLUSION: Three-dimension superimposition method based on CBCT data showed that condylar morphology had undergone remodeling after mandibular advancement.

[Effect of segmental Le Fort I osteotomy and bilateral sagittal split ramus osteotomy on the condyle position in skeletal class III malocclusion patients].

OBJECTIVE: To investigate the effect of segmental Le Fort I osteotomy and bilateral sagittal split ramus osteotomy (BSSRO) on the condyle position in skeletal class III malocclusion patients. METHODS: In this retrospective study, 19 patients with skeletal class III malocclusion who met the inclusion criteria were enrolled. All the patients underwent the segmental Le Fort I osteotomy and BSSRO. Cone beam computed tomography (CBCT) scans were performed in the following phases: T1: within one week before the surgeries; T2: within one week post-surgery;T3:three months post-surgery; T4: 6 to 14 months post-surgery. The posterior spaces, anterior spaces and the superior spaces of the bilateral temporomandibular joints were measured according to the Kamelchuk method respectively. The fossa ratios of the condyle and the distribution of the condyle positions related to the glenoid fossa (anterior, concentric and posterior position)were calculated. The results were analyzed statistically. RESULTS: The posterior space, the anterior space and the superior space of bilateral temporomandibular joints in T2 phase[right: (2.78±1.23) mm, (2.47±0.89) mm, (3.07±0.85) mm; left: (2.93±0.83) mm, (2.69±1.14) mm, (3.44±1.16) mm] showed significantly larger spaces than those in T1 phase [right: (1.81±0.95) mm, (1.65±0.55) mm, (2.13±0.52) mm; left: (2.12± 1.05) mm, (1.79±0.59) mm, (2.15±0.93) mm],in T3 phase [right: (2.08±1.25) mm, (1.79±0.68) mm, (1.80±0.76) mm; left: (2.05±0.75) mm, (1.99±0.94) mm, (2.14±0.71) mm] and in T4 phase [right: (1.94±0.77) mm, (1.81±0.69) mm, (2.05±0.69) mm; left: (1.89±0.69) mm, (1.80±0.61) mm, (2.19±0.75) mm], P<0.05. No significant differences were observed among T1,T3 and T4 phases in the terms of the joint spaces of both sides(P>0.05).The fossa ratio and the condyle position related to the glenoid fossa had no significant difference in all the four phases (P>0.05).The results suggested that the condyle moved downward in T2 phase and changed to the original pre-surgery position in T3 phase, then keot stable in T4 phase. CONCLUSION: Segmental Le Fort I osteotomy and BSSRO caused significant and transient changes of the condyle position in skeletal class III malocclusion patients. However, the condyle tended to move back to the original pre-surgery position and might keep stable.

[Cone-beam computed tomography analysis of root canal configuration of 4 674 mandibular anterior teeth].

OBJECTIVE: To investigate the root canal configuration of mandibular anterior teeth with cone-beam computed tomography (CBCT). METHODS: The CBCT imaging data of 866 patients who visited Peking University School of Stomatology from October 2012 to July 2013 were inspected by an endodontist anda radiologists together. A total of 4 674 mandibular anterior teeth were involved. The number of root, root canals and root canal configuration were observed and analyzed statistically (Chi-squared test). RESULTS: All the mandibular central incisors and lateral incisors were single root, and 0.7% (11/1 542) of canines were double roots. 6.7% (105/1 566) of central incisors, 17.4% (273/1 566) of lateral incisors and 3.0% (46/1 542) of canines had double root canals. The frequency of symmetry of double root canal was 58.7% (37/63) in central incisors, 76.1% (108/142) in lateral incisors and 29.6% (8/27) in canines. The highest frequency of double root canals in different ages was 9.8% (28/287, 31-40 years) in central incisors, 21.5% (61/284, 31-40 years) in lateral incisors and 9.2% (19/207, ≥51 years) in canines. Vertucci type III canal configurations were the most prevalent in mandibular anterior teeth. CONCLUSION: The double root canals are most common in mandibular lateral incisors. The highest incidence of symmetry of double root canal is also observed in mandibular lateral incisors. Vertucci type III canal configurations are the most frequent type in mandibular anterior teeth.

Towards clinically applicable automated mandibular canal segmentation on CBCT.

OBJECTIVES: To develop a deep learning-based system for precise, robust, and fully automated segmentation of the mandibular canal on cone beam computed tomography (CBCT) images. METHODS: The system was developed on 536 CBCT scans (training set: 376, validation set: 80, testing set: 80) from one center and validated on an external dataset of 89 CBCT scans from 3 centers. Each scan was annotated using a multi-stage annotation method and refined by oral and maxillofacial radiologists. We proposed a three-step strategy for the mandibular canal segmentation: extraction of the region of interest based on 2D U-Net, global segmentation of the mandibular canal, and segmentation refinement based on 3D U-Net. RESULTS: The system consistently achieved accurate mandibular canal segmentation in the internal set (Dice similarity coefficient [DSC], 0.952; intersection over union [IoU], 0.912; average symmetric surface distance [ASSD], 0.046 mm; 95% Hausdorff distance [HD95], 0.325 mm) and the external set (DSC, 0.960; IoU, 0.924; ASSD, 0.040 mm; HD95, 0.288 mm). CONCLUSIONS: These results demonstrated the potential clinical application of this AI system in facilitating clinical workflows related to mandibular canal localization. CLINICAL SIGNIFICANCE: Accurate delineation of the mandibular canal on CBCT images is critical for implant placement, mandibular third molar extraction, and orthognathic surgery. This AI system enables accurate segmentation across different models, which could contribute to more efficient and precise dental automation systems.

Short- and long-term changes of condylar position after bilateral sagittal split ramus osteotomy for mandibular advancement in combination with Le Fort I osteotomy evaluated by cone-beam computed tomography.

PURPOSE: Bilateral sagittal split ramus osteotomy (BSSO) may change condylar position, which can be one of the factors contributing to skeletal relapse. This study evaluated short- and long-term changes in condylar position using cone-beam computed tomography (CBCT) and investigated changes in temporomandibular joint (TMJ) signs after BSSO for mandibular advancement in combination with Le Fort I osteotomy. MATERIALS AND METHODS: Thirty-one patients were included, and CBCT data of 62 TMJs were collected before surgery (T0), immediately after surgery (T1), 3 months after surgery (T2), and at the last follow-up at 12.1 ± 3.0 months after surgery (T3). The relation of the condyle to the fossa was evaluated by the method of Pullinger and Hollender (Oral Surg Oral Med Oral Pathol 62:719, 1986). Clinical examination, with a special focus on signs of temporomandibular disorder (TMD), was documented at T0, T2, and T3. Repeated-measures analysis of variance (P = .05) and χ2 test (P = .05) were performed. RESULTS: Data of 27 patients were used for statistical analysis. Values from the formula of Pullinger and Hollender changed significantly with time, but there was no significant difference between the right and left condyles. Condyles moved inferoposteriorly immediately after surgery (T0 to T1) followed by anterosuperior movement 3 months after surgery (T1 to T2). The superimposed effect showed posterosuperior movement compared with the initial position before surgery (T0 to T2) and this position remained stable at 1-year follow-up (T2 to T3). A decrease of TMD signs over time, from 22.6% (T0) to 12.9% (T2) and 9.7% (T3), was observed, which showed no statistical significance. CONCLUSIONS: There were obvious changes in condylar position after BSSO in combination with Le Fort I osteotomy. Condyles tended to be located in a concentric position in relation to the glenoid fossa 3 months after surgery and remained stable during the 1-year follow-up. These changes did not cause an increase of TMD signs.

Viability of the quintessential 5 temporomandibular disorder symptoms as a TMD screener.

OBJECTIVE: This study explored the viability of using the 5 temporomandibular disorder (TMD) symptoms (5Ts) of the Diagnostic Criteria for TMDs (DC/TMD) as a TMD screener. STUDY DESIGN: A total of 1039 adults (≥18 years old) with a mean age of 32.65 ± 12.95 years (77.4% women) from a tertiary dental hospital were enrolled. The 5Ts questionnaire (involving items on TMD/facial pain, headaches, temporomandibular joint noises, and closed- and open-locking) was administered, and TMD diagnoses were derived through clinical interviews and examinations, radiographic investigations, and the DC/TMD diagnostic algorithms and diagnostic tree. Diagnostic accuracy of the 5Ts was assessed using the area under the receiver operating characteristics curve and various measures, including sensitivity, specificity, predictive values, and likelihood ratios. RESULTS: Among the participants, 80.2% (n = 833) were 5Ts-positive, and 19.8% (n = 206) were 5Ts-negative, whereas 51.3% and 85.7% received at least 1 pain-related and intra-articular DC/TMD diagnosis, respectively. The 5Ts showed high accuracy for detecting all TMDs, pain-related and intra-articular, with area under the receiver operating characteristics curves of 0.98, 1.00, and 0.98, respectively. Sensitivity ranged from 96.1% to 99.2%, whereas specificity was 100.0%. CONCLUSIONS: The 5Ts demonstrated high diagnostic accuracy for identifying pain-related and/or intra-articular disorders.

Lateral Lingual Foramina and Canals in the Mandible: CBCT Evaluation of 506 Patients in North China.

OBJECTIVE: To assess the prevalence, location, diameter, course and anastomosis of the lateral lingual foramina (LLF) and canals (LLCs) in a northern Chinese population using CBCT. METHODS: CBCT images of 506 patients (181 male and 325 female, mean age 21.03 ± 8.11 years) were collected. The prevalence, location, diameter, length, angle and anastomosis of the LLF and LLCs were assessed. The measurement variables were analysed by sex and age. Statistical analysis was performed using SPSS (v. 25, IBM, Armonk, NY, USA). RESULTS: A total of 461 LLF were detected in 307 (60.7%) subjects, 175 (57.0%) of whom had unilateral LLF and 132 (43.0%) of whom had bilateral LLF, with each lateral having one to four LLF. The majority of LLF (375/461, 81.3%) were located below the premolars, particularly the first premolar. The mean diameter of the LLF was 0.58 ± 0.20 mm. The mean vertical distance from the LLF to the inferior border and the alveolar crest was 6.68 ± 1.43 mm and 23.65 ± 2.89 mm, respectively. In total, 197 LLCs were visible in the cancellous bone and evaluated. The mean length of LLCs was 6.26 ± 1.29 mm, and the mean angle of LLCs was 140.64° ± 17.29°. The overwhelming majority (93.4%) of LLCs communicated with the mandibular incisive canal and the rest connected with the mandibular canal. CONCLUSION: The prevalence of LLCs was high in the northern Chinese population. The presence of LLCs is a significant predictor of communication with the mandibular incisive canal.

Temporomandibular disorder severity and diagnostic groups: Their associations with sleep quality and impairments.

OBJECTIVES: This study evaluated the impact of TMD severity on sleep quality and established the associations between TMD diagnostic groups/pain subtypes and sleep impairments. METHODS: A total of 1151 patients from a tertiary Dental Hospital were screened for eligibility. Consenting subjects who met the inclusion criteria were directed to complete a general/health questionnaire, the Fonseca Anamnestic Index (FAI), Diagnostic Criteria for Temporomandibular disorders (DC/TMD) Symptom Questionnaire, and Pittsburgh Sleep Quality Index (PSQI) at their intake visit. Patients who screened positive for TMDs with the FAI were subjected to a protocolized physical examination and TMD diagnostic groups/subtypes were subsequently derived based on the DC/TMD "diagnostic tree" and algorithms. Statistical analyses were conducted using non-parametric methods and logistic regression (α = 0.05). RESULTS: The final sample consisted of 845 subjects with TMDs and 116 TMD-free controls. The mean age of the TMD and TMD-free subjects were 33.17 ± 13.55 and 31.66 ± 9.50 years. Subjects with severe and moderate TMDs had significantly greater global PSQI scores than those with mild and no TMDs (p < 0.001). Those with pain-related, intra-articular, and combined TMDs reported significantly poorer sleep quality than those with no TMDs (p < 0.001). Moreover, subjects with myalgia and myalgia plus arthralgia presented significantly greater sleep impairments than their counterparts with intra-articular disorders (p < 0.001). Multivariate logistic regression indicated that pain-related (OR = 3.23; CI = 1.69-6.14) and intra-articular TMDs (OR = 1.91; CI = 1.15-3.16) were most related to poor sleep. CONCLUSIONS: Sleep quality worsened with increasing TMD severity and the presence of painful and intra-articular TMDs increased the likelihood of poor sleep.

[Experimental occlusal interference induces the expression of protein gene products and substance P in masseter muscles of rats].

OBJECTIVE: To investigate the peripheral mechanism by studying the histological changes of masseter muscles using HE stains and substance P (SP) and protein gene product 9.5 (PGP9.5) immunohistochemical stains. METHODS: Fifteen male Sprague-Dawley were randomly assigned into occlusal interference group (n=12) and control group (n=3). In occlusal interference group, 0.4 mm thick crowns were bonded to the rats' first molar of the maxillary. In the control group, rats were anesthetized and mouths were forced open for about 5 min but restorations were not applied. 1, 5, 10, and 21 d after 0.4 mm occlusal alteration treatment, mechanical pain thresholds of bilateral masseter muscles were quantitatively measured by modified electronic anesthesiometer in control group and occlusal interference group. The rats were euthanized by transcardiac perfusion after deep anesthetization at different time points. The paraffin sections of masseter muscles were made and processed for HE, SP, and PGP9.5 immunohistochemical staining. RESULTS: Decreased head withdrawal threshold to mechanical pressure was detected in masseter muscles on both sides following occlusal interference. Histological stains of masseter muscles presented intact following occlusal interference, and no inflammatory cells were observed in both sides. Intensely stained PGP9.5 was observed at 1 d in occlusal interference groups and maintained until the end of the experiment. SP expression was the most obviously increased at 5 d in both sides and gradually decreased to the level of control. CONCLUSION: Experimental occlusal interference-induced masticatory muscle pain is associated with peripheral sensitization of nociceptive neurons rather than muscle damage and inflammation.

[Radiological characteristics of the cyst-like lesion of condyle in temporomandibular joint by cone beam computed tomography].

OBJECTIVE: To analyze the radiological characteristics and classifications of the cyst-like lesion of condyle in temporomandibular joint (TMJ) by cone beam computed tomography (CBCT). METHODS: The study was conducted retrospectively on TMJ images from 194 patients who underwent CBCT examinations. Location, size, amount, surrounding bone trabecula, cortical bone white line of cyst-like lesion, and the overall condition of the condylar bone were evaluated. According to the overall condition of the condylar bone, the cyst-like lesion of condyle were divided into typesⅠand Ⅱ. The location, size, amount, surrounding bone trabecula, and cortical bone white line of the two types of cyst-like lesions were compared. RESULTS: In 198 condylars of 194 patients, cyst-like lesions were detected in the left side of 94 patients, in the right of 96 patients, and in both sides of 4 patients. The size of lesions ranged from 1.2 mm to 13.5 mm, with an average size of (3.4±1.5) mm. Half of the cyst-like lesions were located underneath the anterior lateral cortical bony layer (99 condylars, 50.0%). Most cyst-like lesions were solitary (149 condylars, 75.3%), while 62.6% (124 condylars) were surrounded by continuous bony white lines. Bone sclerosis could be observed in 160 condylars (80.8%). A total of 132 condyles (66.7%) were accompanied by changes in late-stage osteoarthrosis, while the others were only accompanied by early-stage osteoarthrosis (10 osteoarthrosis, 5.1%) or showed no evidence of osteoarthrosis (56 osteoarthrosis, 28.3%). Statistical difference were observed in the location, amount, and surrounding bone trabecula of the two types of cyst-like lesions. TypeⅠcyst-like lesions had more frequent and bone sclerosis than type Ⅱ, whereas type Ⅱ cyst-like lesions occurred more on condylar internal or condyle neck than typeⅠ. CONCLUSIONS: The pathogenesis and mechanism of the two types of cyst-like lesions may be different from each other.

[CT imaging features of diffuse tenosynovial giant cell tumor of temporomandibular joint].

OBJECTIVE: This study aimed to investigate the characteristic features of CT images of diffuse tenosynovial giant cell tumor (D-TSGCT) from the temporomandibular joint (TMJ) to understand CT imaging diagnosis of the disease. METHODS: CT images and clinical information from 10 patients with D-TSGCT of TMJ were recruited for retrospective analysis from March 2013 to March 2017 in Peking University Hospital of Stomatology. All cases were treated by surgery and confirmed by pathology. RESULTS: CT scan demonstrated hyperdense soft-tissue masses and various kinds of calcification in all of the 10 subjects. Contrast-enhanced scan exhibited obvious enhancement in six patients. Bone destruction of the mandibular condyles and skull base was found in seven and six subjects, respectively. CONCLUSIONS: CT appearance of D-TSGCT of the TMJ is characterized by hyperdense soft tissue with calcification, further enhancement in contrast-enhanced scan, and bone destruction in the mandibular condyles and skull base in some cases.

Unilateral complete articulated ossification and aberrant thickening of the stylohyoid chain.

Eagle's syndrome is a rare clinical entity associated with craniofacial and cervical pain. It is caused by an elongated or deviated styloid process and/or calcification/ossification of the stylohyoid ligament. Complete ossification and aberrant thickening of the stylohyoid chain is the most unusual manifestation. We report a patient who presented with complaints of foreign body sensation, dysphagia and moderate submandibular pain caused by unilateral complete ossification, abnormal thickening and hypertrophy of the stylohyoid chain. This case was also unique in that histopathological investigation demonstrated mature bone with both compact and cancellous bone as well as bone marrow.

Metrical analysis of disc-condyle relation with different splint treatment positions in patients with TMJ disc displacement.

OBJECTIVE: To evaluate the effect of bite positions characterizing different splint treatments (anterior repositioning and stabilization splints) on the disc-condyle relation in patients with TMJ disc displacement with reduction (DDwR), using magnetic resonance imaging (MRI). MATERIAL AND METHODS: 37 patients, with a mean age of 18.8±4.3 years (7 male and 30 females) and diagnosed with DDwR based on the RDC/TMD, were recruited. MRI metrical analysis of the spatial changes of the disc/condyle, as well as their relationships, was done in three positions: maximum intercuspation (Position 1), anterior repositioning splint position (Position 2), and stabilization splint position (Position 3). Disc/condyle coordinate measurements and disc condyle angles were determined and compared. RESULTS: In Position 1, the average disc-condyle angle was 53.4° in the 60 joints with DDwR, while it was -13.3° with Position 2 and 30.1° with Position 3. The frequency of successful "disc recapture" with Position 2 was significantly higher (58/60, 96.7%) than Position 3 (20/60, 33.3%). In Positions 2 and 3, the condyle moved forward and downward while the disc moved backward. The movements were, however, more remarkable with Position 2. CONCLUSIONS: Anterior repositioning of the mandible improves the spatial relationship between the disc and condyle in patients with DDwR. In addition to anterior and inferior movement of the condyle, transitory posterior movement of the disc also occurred.

Degenerative temporomandibular joint changes associated with recent-onset disc displacement without reduction in adolescents and young adults.

This study evaluated the occurrence of degenerative temporomandibular joint (TMJ) changes in adolescents and young adults with recent on-set disc displacement without reduction (DDw/oR) using high-resolution cone beam computed tomography (CBCT). The associations between types of osteoarthrosis (OA) changes and clinical factors including disease duration were also examined. CBCT and clinical data of 300 patients (84.70% females, mean age 20.93 ± 4.77 years) diagnosed with unilateral DDw/oR (≤12 months) based on RDC/TMD were acquired. CBCT images of both symptomatic and contralateral asymptomatic TMJs were independently evaluated and scored by two radiologists. Associations between OA changes and gender, age, mouth opening and duration of DDw/oR were analyzed statistically. Condylar OA changes were present in 59.30% of the joints with DDw/oR. Early-stage OA changes (loss of continuity of articular cortex and/or surface destruction) constituted most (45.67%) of the alterations. Prevalence of early-stage OA increased from 24% to about 60% one month after TMJ closed-lock occurred. Logistic regression analysis showed the risk of developing early-stage OA changes was 5.33 times higher one month after onset of DDw/oR. A high prevalence of degenerative TMJ changes was observed with recent on-set DDw/oR in adolescents and young adults. Early diagnosis and intervention of DDw/oR is therefore prudent.