Search Results (314)

Radiation-induced trismus (RIT) is a common and function-limiting late complication of radiotherapy for head and neck cancers, particularly when the masticatory muscles and temporomandibular joint receive high doses. Despite advances in intensity-modulated radiotherapy, RIT remains a significant survivorship problem, and robust biological biomarkers capable of predicting individual susceptibility are lacking. Heat shock protein 27 (HSP27; HSPB1) is a small heat shock protein that regulates multiple cellular stress responses, including proteostasis, cytoskeletal dynamics, redox homeostasis, apoptosis, and inflammatory signaling. In head and neck malignancies, HSP27 overexpression has been associated with treatment resistance and fibrosis-prone tissue remodeling. Experimental studies further demonstrate that HSP27 promotes transforming growth factor-β-mediated myofibroblast differentiation and extracellular matrix deposition, whereas pharmacologic or genetic inhibition attenuates radiation- or bleomycin-induced pulmonary fibrosis in vivo. Evidence from skeletal muscle biology also indicates that HSP27 modulates muscle integrity, denervation-associated atrophy, inflammatory signaling, and cytoskeletal stability. Although HSP27 has been widely investigated in radiation responses, fibrosis, and skeletal muscle stress adaptation, its potential involvement in the pathogenesis of RIT has not been systematically examined. This review proposes a conceptual framework in which HSP27 functions as an integrative molecular mediator linking radiation-induced oxidative stress, endothelial injury, and fibro-atrophic remodeling within the masticatory apparatus. By integrating current evidence on the epidemiology, dosimetric determinants, imaging correlates, and pathophysiology of RIT with the structural and functional biology of HSP27, this review provides the first tissue-specific synthesis of molecular stress signaling and clinical mechanisms relevant to RIT susceptibility. We further suggest that HSP27 signaling may influence susceptibility to fibro-neuromuscular injury in irradiated masticatory tissues. Given the absence of direct experimental or clinical evidence in this setting, these considerations are derived from mechanistic convergence across related biological systems and should be interpreted as biologically plausible but unproven, with potential implications for future biomarker development and biologically informed prevention strategies. Full article

The safety of mandibular anesthesia is directly dependent on a precise understanding of the spatial relationships in the pterygomandibular space, particularly the risk of injury to the highly vascularized pterygoid venous plexus (PVP). In vivo studies of PVP displacement during mandibular movements face significant technical challenges. Objective: The study aims to study the spatial displacements of the pterygoid venous plexus during various physiological positions of the mandible using computer modeling with the finite-element method (FEM). Materials and Methods: A three-dimensional finite-element model was developed based on computed tomography data and the BodyParts3D anatomical atlas. The model included the bony structures of the skull, mandible, temporomandibular joint, masticatory muscles, and blood vessels. Simulations were performed for vertical displacements of the jaw at 15, 25, and 35 mm, as well as horizontal displacements of 5 mm to the left and right. Results: It was found that the magnitude of PVP displacement is proportional to the degree of mouth opening. The maximum total displacement (1.24 mm) was recorded at a 35 mm opening along the “posterior–medial–inferior” vector. Lateral excursions revealed asymmetry: displacement to the right caused plexus movement posteriorly, medially, and inferiorly (0.66 mm), while displacement to the left resulted in movement anteriorly, laterally, and superiorly (0.64 mm). Conclusions: This study demonstrates the significant mobility of the pterygoid venous plexus, which depends on the direction and amplitude of mandibular movements. The obtained data have important practical implications for planning regional anesthesia and minimizing the risk of iatrogenic complications. From a biomechanical perspective, maximum mouth opening produces the greatest displacement of the PVP, which may hypothetically reduce the risk of vascular puncture. Clinical studies are required to confirm this. Full article

Background: Myogenous temporomandibular disorders (TMDs) are a common subtype of orofacial pain. Evidence regarding treatment with botulinum toxin type A (BoNT-A) remains heterogeneous, and its use is generally limited to refractory cases. This study evaluated 12-month clinical outcomes following an incobotulinumtoxinA protocol (the Ângelo Botulinum Toxin Protocol^®) in adults with DC/TMD-confirmed myogenous TMD unresponsive to conservative therapy. Methods: This retrospective observational study reviewed records from 98 adults treated with incobotulinumtoxinA following the predefined injection protocol. All patients had failed ≥ 3 months of conservative management and completed ≥ 12 months of follow-up. Outcomes included myalgia severity (0–3), patient-reported orofacial pain intensity (VAS 0–10), and maximum mouth opening (MMO). Favorable outcome criteria required myalgia 0–1 or VAS ≤ 2 and MMO ≥ 35 mm. Results: Myalgia significantly decreased at 12 months (2.69 ± 0.64 to 0.43 ± 0.85; p < 0.001). Patient-reported orofacial pain intensity also improved (2.44 ± 2.54 to 0.37 ± 1.33; p < 0.001). MMO remained stable, indicating preserved mandibular mobility. Overall, 79.6% of patients met the predefined favorable outcome criteria. Reintervention was required in 12 patients; 7 received additional incobotulinumtoxinA injections, and 5 underwent TMJ arthrocentesis. No complications were observed. Conclusion: This protocol was associated with improvements in muscular pain and orofacial discomfort while preserving mandibular mobility. However, given the retrospective design and absence of a control group, these findings should be interpreted as hypothesis generating. Full article

Objectives: This study aimed to analyze longitudinal changes in masticatory muscle volume at pretreatment and after orthognathic surgery in skeletal Class III patients with and without facial asymmetry. Methods: Patients were divided into symmetry and asymmetry groups (n = 30, each; male: female ratio 1: 1, for both groups; age at T1: asymmetry group 25.4 ± 8.1, symmetry group 22.9 ± 7.7). Computed tomography images were obtained at pretreatment (T1), one month after surgery (T2), and at 22 months postoperatively (T3). Three-dimensional reconstruction software was used to measure the volumes of the masseter, temporalis, medial pterygoid, and lateral pterygoid muscles. Results: At T1, the asymmetry group exhibited significantly smaller masseter and temporalis muscle volumes on the deviated side. These differences tended to decrease at T3. No significant bilateral differences were observed in the medial or lateral pterygoid muscles at each point. Longitudinal analyses showed that temporalis and lateral pterygoid muscle volumes decreased from T1 to T2 and increased from T2 to T3, whereas masseter muscle volume did not have a significantly longitudinal difference and the medial pterygoid muscle volume decreased significantly at T3. Conclusions: In Class III patients with facial asymmetry, pretreatment asymmetry of the masseter and temporalis muscle volumes tended to improve postoperatively as bilateral muscle volume increased. Full article

Background: Alterations of the vertical dimension of occlusion may affect masticatory muscle function, which is critical in pre-prosthetic planning, especially in Class II division 2 malocclusions. This study aimed to evaluate the impact of increasing VDO on the myoelectric activity of masticatory muscles using surface electromyography (EMG). The null hypothesis was that a 2–4 mm increase in VDO does not significantly influence muscle activity. Methods: Nine patients with Class II division 2 malocclusion were evaluated. EMG recordings of the masseter and anterior digastric muscles were obtained using the BioEMG II system (BioResearch Asoc., Milwaukee, WI, USA) and Biopak™ software (AcqKnowledge 4.x). VDO was increased using the Dupas universal jig. EMG was recorded for 30 s under six conditions: resting posture, intercuspal position (IM), swallowing, resting posture after VDO increase, IM with increased VDO (IM2), and swallowing with increased VDO (swallowing 2). Results: Most EMG variables showed no statistically significant differences after short-term VDO increase. Significant differences were observed only in the resting activity of both masseter muscles and in the right masseter during maximum intercuspation. No significant changes were identified during swallowing. Conclusions: Within the limitations of this pilot study, a 2–4 mm increase in VDO appears to produce minimal short-term changes in masticatory muscle activity in Class II division 2 patients. These findings should be interpreted with caution due to the small sample size and short observation period, and further studies are required to evaluate long-term neuromuscular adaptation. Full article

Objectives: The aim of this study was to compare the relationship between psychological factors and the thickness of masticatory muscles in patients with temporomandibular disorders (TMD) and healthy controls. Methods: This cross-sectional study included 106 female participants aged 18–35 years, recruited from students of the Medical University of Lublin. The study group consisted of individuals diagnosed with myalgia based on the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD), while the control group included participants without TMD. Psychological factors were assessed using the PHQ-9, GAD-7, and PHQ-15 questionnaires. The thickness of the temporalis and masseter muscles was measured using an M-Turbo (Sonosite) ultrasound device under relaxed and contracted conditions. Results: Participants with TMD-related myalgia scored significantly higher on the PHQ-9 (mean ± SD: 8.82 ± 5.02 vs. 5.00 ± 3.41; p < 0.001), GAD-7 (8.53 ± 4.48 vs. 4.65 ± 3.58; p < 0.001), and PHQ-15 (9.47 ± 4.07 vs. 6.02 ± 3.89; p < 0.001) compared to controls. No statistically significant differences were observed in temporalis or masseter muscle thickness at rest or during contraction between groups (p > 0.05). Significant differences in correlations were found between depression scores and temporalis muscle thickness in the study group compared to the control group (r = 0.32 vs. −0.13, p = 0.011) as well as between anxiety scores and temporalis muscle thickness (r = 0.25 vs. −0.30, p = 0.002) No significant associations were found for the masseter muscle. Conclusions: Individuals with myalgia did not show increased muscle thickness compared to healthy individuals. Psychological distress, particularly depression and anxiety, was differentially related to temporalis muscle morphology in individuals with myalgia compared to healthy controls. Full article

Temporomandibular disorders (TMDs) are the prevalent causes of orofacial pain and dysfunction of the temporomandibular joint (TMJ) and masticatory muscles. Previous studies have revealed that proinflammatory cytokines play a key role in promoting inflammation, pain, and degeneration within the TMJ. In this context, the present systematic review synthesizes current evidence on various cytokines involved in the pathophysiology of TMDs and evaluates their associations with clinical signs and structural TMJ damage. A PRISMA-guided search (PROSPERO: CRD420251163290) was conducted in PubMed/MEDLINE, Embase, Scopus, and the Cochrane Library to identify human-based, in vivo, and in vitro studies (January 2014 to September 2025) that assessed the roles of proinflammatory cytokines in TMDs. The following data were extracted from the identified studies: cytokine profiles, sampling methods, clinical outcomes, and TMJ structural changes. Study quality and risk of bias were systematically evaluated. A total of 15 studies (clinical, animal, and mechanistic) were included in the review. Tumor necrosis factor-alpha (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), and interleukin-17 (IL-17) consistently emerged as the major contributors to synovitis, cartilage degradation, nociceptive sensitization, and bone resorption. Human studies showed that high levels of TNF-α, IL-1β, and IL-6 and chemokines such as C-C motif chemokine ligand 2 (CCL2) and regulated on activation, normal T-cell expressed and secreted (RANTES) were associated with TMJ pain, restricted mandibular motion, crepitus, malocclusion, and erosive changes on imaging. An increased ratio of TNF to soluble TNF receptor in synovial fluid correlated with both pain and condylar damage, suggesting that loss of cytokine control contributes to progressive joint destruction. TMDs, particularly inflammatory and degenerative subtypes, are cytokine-driven pathologies rather than purely mechanical disorders. TNF-α, IL-1β, and IL-6 are the promising candidate biomarkers of local inflammation and structural joint pathology. Standardized longitudinal studies are required to validate cytokine-based diagnostics and develop anti-cytokine therapeutics. Full article

Objectives: To quantitatively assess masticatory function with instrumental measures in a group of patients suffering from temporomandibular joint (TMJ) arthralgia, and to compare the results with symptom-free controls. Methods: Data of bite force, variance-of-hue-based (VOH) chewing efficiency, chewing frequency, the bilateral pressure pain threshold (PPT) of the temporalis and masseter muscles, and mandibular range of motion (RoM) were collected in a sample of TMJ arthralgia patients (n = 14) and controls (n = 19). The diagnosis of arthralgia was obtained following the DC/TMD protocol. Comparison between the groups was conducted using independent samples t-tests (level of significance α = 0.05). Associations within the arthralgia group were assessed using Pearson’s correlation coefficient. Results: In comparison to the controls, arthralgia patients showed significantly restricted pain-free and maximum unassisted mouth opening (p < 0.001, p = 0.022 respectively) as well as a significant decrease in both bite force (p < 0.001) and chewing frequency (p = 0.01). The average chewing efficiency for the arthralgia group was 0.14 ± 0.08 VOH. The PPT for both masseter muscles did not show significant differences in comparison to the control group. Conclusions: In patients with TMJ arthralgia, functional markers such as RoM, bite force, and chewing frequency exhibited significant limitations compared to the control group. The employment of instrumental measurements in the documentation of symptoms in clinical practice provides an objective basis for the assessment of functional limitations. Hence, we recommend integrating them into the longitudinal patients’ observation during therapy. Full article

Background: Oral frailty is an emerging determinant of late-life disability. While objective functional measures have been proposed as key indicators, their combined role in predicting frailty among physically active older adults remains unclear. Therefore, this study aimed to investigate the association between the presence of oral frailty and lip pressure, bite force, and denture use. Methods: This cross-sectional study included 192 participants aged 60 years or older from Brazil (n = 131) and Portugal (n = 61), all physically active and with ≥20 natural or rehabilitated teeth. Data were collected through a questionnaire on sociodemographic data and the Oral Frailty Index-8. The clinical assessment included lip pressure, bite force, and denture use. Multiple logistic regression identified independent predictors; model fit and discrimination were examined using the Hosmer–Lemeshow test and ROC curve. Results: Participants were mainly female (83.3%), mean age ≈72 years; 76% used dentures and frailty prevalence was ≈49%. Higher lip pressure (OR = 0.986, 95% CI = [0.973–0.999]) and higher bite force (OR = 0.925, 95% CI = [0.885–0.967) were independently protective, whereas denture use (OR = 6.898, 95% CI = [2.994–15.895]) markedly increased oral frailty odds. The model showed good discrimination (AUC 0.779). Conclusions: Even small increases in lip pressure and bite force reduced the likelihood of frailty, while denture use identified individuals at substantially higher risk. These findings highlight orofacial muscle strength and masticatory capacity as core components of oral frailty and support incorporating lip pressure and bite force testing into multidimensional frailty assessment and targeted rehabilitation. Full article

Background: Existing evidence suggests an association between temporomandibular disorders (TMDs) and alterations in body posture and balance; however, the mechanism underlying this relationship remains unknown. The present study aimed to investigate the associations between specific TMD subtypes, indices of bioelectrical activity of the masticatory muscles, and parameters of body posture and balance. Methods: The study followed a case–control study design. A total of 81 participants were enrolled, including 33 controls and 48 individuals with TMD, classified into myofascial (n = 14), articular (n = 17), and mixed (n = 17) subtypes. Diagnosis of temporomandibular disorders was carried out by prosthodontic specialists using the Polish adaptation of the Diagnostic Criteria for Temporomandibular Disorders. Masticatory muscle bioelectrical activity was assessed by surface electromyography. For statistical analysis, the Asymmetry Index and Functional Clenching Activity Indices were used. Static balance was evaluated with a pedobarographic platform. The sway area, velocity, and length of the Center of Pressure, as well as the foot contact area, were recorded and automatically calculated by the system. Measurements were performed under different mandibular conditions, with both eyes open and eyes closed. Correlation analyses were performed using Spearman Rank Order Correlation. Pearson’s Chi-squared test was used for the analysis of categorical variables. Results: Weak to moderate negative correlations were primarily observed, indicating that higher indices of masticatory muscle bioelectrical activity were associated with better postural balance, with distinct correlation patterns identified across different TMD subtypes. Conclusions: This exploratory study identified multiple correlations between masticatory muscle activity and postural or balance parameters, suggesting possible subtype-specific patterns in TMDs. However, the evidence remains preliminary and should be interpreted with caution, warranting further confirmatory and longitudinal research. Full article

Background/Objectives: Temporomandibular disorders (TMDs) are a group of multifactorial conditions affecting the temporomandibular joints (TMJs), masticatory muscles, and associated structures. TMDs are identified as the main cause of non-dental orofacial pain in children and adolescents. This scoping review aims to explore recent evidence on prevalence, clinical presentation, associated factors, and treatment approaches of TMDs in children and adolescents. Methods: A systematic search was conducted across PubMed, Scopus and Embase for studies published between 2015 and 2025, following PRISMA-ScR guidelines. Results: Thirty-eight studies were included. TMD prevalence in children and adolescents ranged from 16.9% to 40% through clinical examination, with painful TMD rates ranging from 16.2% to 25.5%, while symptom-based surveys reported prevalences of 9–35.3%. The most frequent diagnoses were myofascial pain, myalgia, arthralgia and disc displacement with reduction. Female sex and increasing age were consistent risk factors. Psychosocial variables, such as anxiety and depression, showed strong associations with pain-related TMDs. Structural and systemic conditions such as musculoskeletal alterations, joint hypermobility, respiratory conditions and headaches/migraines were also frequently reported. Evidence on treatment appears to be limited. In juvenile idiopathic arthritis (JIA), TMJ involvement is prevalent (32.6–64%), particularly in the persistent oligoarticular subtype. Conclusions: TMDs in children and adolescents are prevalent and multifactorial conditions, mainly of muscular origin, presenting more frequently in adolescents and females. Psychosocial factors, functional habits, clenching, mouth breathing and systemic conditions may be associated with TMD presence or severity. Substantial heterogeneity persists in diagnostic criteria, assessment tools and outcome measures. Research on therapeutic interventions is scarce and often limited to small samples. Standardized diagnostic protocols, improvements in research consistency, longitudinal cohorts and RCTs are needed to clarify etiological pathways, validate diagnostic criteria and establish effective, evidence-based strategies for the management of TMDs in children and adolescents. Full article

Introduction: Disc displacement with reduction (DDwR) and myalgia are among the most common temporomandibular disorders, frequently affecting young adults. While conservative therapy is considered the first-line approach, the evidence on long-term outcomes is still limited. Case Presentation: A 22-year-old female had a 7-month history of left-sided TMJ clicking, deviation to the left during opening, and 2 months of bilateral masticatory pain, which was worsened by mastication. During clinical examination, reproducible left TMJ clicking and tenderness of the masseter and temporal muscles were observed. Based on DC/TMD Axis 1, DDwR with myalgia diagnosis was made. Intervention and Results: A full maxillary stabilization splint was constructed and delivered together with patient education, dietary adjustments, and guided mandibular exercises. At baseline, pain intensity was VAS 6/10 with a maximum unassisted mouth opening of 41 mm and reproducible joint clicking. After 2 weeks, the patient reported a decrease in pain, VAS 2/10, mouth opening was 44 mm, and joint sounds were absent. After 1 year, the patient was asymptomatic (VAS 0/10) with stable function, preserved mouth opening, and completion of daily activities without limitations. Clinical Relevance and Conclusions: This case shows that multi-directional non-invasive therapy can result in complete and long-term remission of DDwR with myalgia. It emphasizes the need for careful diagnosis, through standardized instruments such as DC/TMD, and the need for personalized treatment to ensure durable clinical success. Full article

Introduction. Occlusal splints are oral appliances that have been designed to relieve the temporomandibular symptoms. However, the thickness of occlusal splints in order to have optimal efficacy is still controversial. Methods. An electronic search in Medline, Scopus, and Web of Science databases was conducted, using the following keywords up to 2025: (“occlusal splint” OR “stabilization splint” OR “bite splint”) AND (“vertical dimension” OR “thickness” OR “occlusal height”) AND (“temporomandibular disorder” OR “TMD” OR “disc displacement” OR “myofascial pain”). All titles and abstracts were screened. Studies comparing different thicknesses of occlusal splints were included. Results. Eight studies met the inclusion criteria, of which five were randomized controlled trials, one a retrospective study, and two finite element analyses. Mixed quality of the studies was found. Based on current evidence, although limited, the following results could be deduced: Occlusal splints with moderate thickness, 3 mm, are recommended for cases that involve both muscular and joint components, particularly when masticatory muscle pain is the primary complaint. Occlusal splints with minimal thickness, 2 mm, may be appropriate in internal derangements in the early stage, though evidence is low. Thicker splints, ≥4 mm, are for DDwoR and cases with crepitus. Occlusal splints of ≤2 mm and >6 mm were associated with symptoms such as reduced functional outcomes or comfort. Conclusion. In most cases, occlusal splints with thicknesses of 3–5 mm seem to be optimal for most TMD cases; however, personalized treatment based on the respective diagnosis is recommended. The decision on splint thickness should be based on evidence according to the severity of the diagnosis, but also patient-centered, to achieve comfort, compliance of the patient, and oral structure preservation. Further high-quality RCTs are needed to gain evidence-based guidelines and to achieve consistent results. Full article

Dental implantation affects masticatory bite and muscle forces. The temporomandibular joint (TMJ) bears a substantial amount of these masticatory forces. Thus, the objective of the current study was to investigate whether dental implantation alters the human mandibular condyle. Among 556 images, 54 and 22 CBCT scans were successfully identified from 27 patients (10 males and 17 females; 54.93 ± 19.46 years) in the control group and 11 patients (3 males and 8 females; 51.32 ± 13.13 years) in the implant group, respectively. In the control group, CBCT images were obtained longitudinally at the time of implantation and after the post-implantation healing period, both prior to crown placement. In the implant group, CBCT images were obtained at the time of crown placement on a single-tooth implant and after the functional loading period following crown placement. Left and right mandibular condyles were digitally isolated from the images. The bone mineral density (BMD) parameters and morphological changes were assessed using frequency plots of BMD and TMJ osteoarthritis (OA) counts, respectively. In the control group, BMD values were not significantly different between the first and second scans. In contrast, the implant group showed a significant decrease in BMD values, along with a marginal increase in TMJ OA counts after the functional loading period. The TMJ OA counts were highest in the anterior regions, followed by the middle and posterior regions. Most regions showed significantly reduced BMD values, except the antero-lateral and antero-central regions. The current findings give an insight that dental implantation may alter the morphology and BMD of human mandibular condyles. The TMJ OA counts increased, while BMD decreased during the functional loading period of more than 3 months following implantation. Masticatory loading associated with the dental implant likely increases the load on the TMJ, which could stimulate new bone formation to balance the load distribution on the mandibular condyle. Full article

Background/Objectives: Population aging presents new challenges for achieving healthy aging. Edentulism is a condition that diminishes quality of life. Several studies have attempted to analyze the impact of edentulism on masticatory function either by evaluating the final stage of the food bolus or the masticatory process itself. The present study aims to develop a chewing index (Ci) based on chewing time, the number of cycles, and the muscular activity of the masseter and temporal muscles. Methods: Two groups (n = 10 each, 60–80 years old), one with functional dentition (21 or more teeth) (Group F) and one with complete denture wearers (Group D), were used. Participants were asked to chew a total of 36 food samples. The number of chewing cycles (N), chewing time (T), and bilateral activity of the masseter and anterior temporal muscles were recorded and quantified using the root mean square. This activity was normalized with respect to a 5 s maximum voluntary clenching (T_MAV). A chewing index (Ci) was calculated using the equation Ci = N × $\overline{V_{\%}}$ × T/T_MAV, where $\overline{V_{\%}}$ represents the average normalized activity of the four muscles. Results: Ci values ranged from 0 to 62 for Group F and 0 to 262 for Group D. For 15 out of the 36 food samples, Ci was higher in Group D than in Group F. Conclusions: The results of this study are consistent with previous research showing that complete denture wearers must chew for a longer time and perform a greater number of chewing cycles compared with subjects with functional dentition. Full article