Platelet-rich plasma injections for the treatment of temporomandibular joint disorders: A systematic review

OBJECTIVE

This systematic review aimed to investigate and examine whether intra-articular injections of platelet-rich plasma (PRP) after arthrocentesis are beneficial for the treatment of temporomandibular disorders, when compared to other treatments, such as injections of hyaluronic acid (HA) or saline after arthrocentesis.

METHODS

An electronic search on PubMed was performed using combinations of the terms 'temporomandibular' and 'platelet rich plasma', to identify studies reported in English and published up until 2017. The initial screening identified 222 records, of which only seven fulfilled the inclusion criteria and were included in this review. Of these studies, three compared injection of PRP after arthrocentesis with the injection of HA after arthrocentesis, while two compared injection of PRP after arthrocentesis with Ringer's lactate after arthrocentesis and one compared injection of PRP after arthrocentesis to sodium chloride.

RESULTS

Five of the studies found that PRP injections have led to significant improvements in mandibular range of motion and pain intensity up to 12 months after treatment, while the remaining two studies found similar results for the different treatments.

CONCLUSION

However, a standardized protocol for PRP preparation and application needs to be established.

Effectiveness of exercise therapy on pain relief and jaw mobility in patients with pain-related temporomandibular disorders: a systematic review

Background

Orofacial pain conditions are complex disorders that involve biological, social, and psychological factors. Temporomandibular Disorders (TMDs) are one of the most common orofacial pain conditions, and our previous literature review indicated that exercise therapy has shown promise in reducing TMD-related pain. However, more evidence is needed to firmly establish its effectiveness.

Objectives

This systematic review aims to investigate the effectiveness of exercise therapy on pain relief and jaw mobility in patients with pain-related TMDs.

Methods

To include randomized controlled trials (RCTs) written in English, a literature search was performed using PubMed, Scopus, Web of Science, Cochrane Library, Ovid, EBM reviews, and Academic Search Complete initially from 4th November 2020 until March 2022. A PICOS for this review was as follows; P: Patients with TMD myalgia or arthralgia, I: Excursion exercise, Stretch exercises, Resistance exercise, or Coordination exercise, C: No treatment or education only. O: Pain intensity and Range of Motion (ROM), S: RCTs. After title screening, a full-text assessment was done to extract data. According to Risk of Bias (RoB) 2.0, risk of bias was assessed in each included paper by 2 reviewers independently.

Results

A total of 3,388 titles were identified from the electronic database search. After the screening and full-text evaluation, only 5 studies (145 participants) were eligible to be included. Among the exercise modalities, coordination exercise showed a significant effect on pain relief and improvement of joint mobility.

Discussion

Due to the heterogeneity and small sample size of the included studies, a meta-analysis was not feasible. However, this systematic review suggested that exercise therapy, especially coordinate exercise, can be effective in managing painful TMD conditions. Further research is needed to establish optimal parameters for this patient population, as well as standardization and consistency in terminology and treatment structure.

Common therapeutic approaches in sleep and awake bruxism - an overview

Bruxism, a common medical condition characterised by clenching or grinding of the teeth and/or by bracing or thrusting of the mandible, can occur during sleep, when it is known as sleep bruxism (SB), or during wakefulness, when it is known as awake bruxism (AB). Although bruxism often causes headaches, temporomandibular joint pain, masticatory muscle pain, mechanical tooth wear, prosthodontic complications and cracked teeth, there is still not enough data to define and support a standardised approach to its treatment. The aim of this review was to present the pathophysiology, consequences, types and treatment methods of bruxism in order to increase readers' knowledge of this topic. Differences between awake and nocturnal bruxism are included, as well as risk factors and indicators visible during the clinical examination of affected patients. Among the causes we consider are genetics, stress, oral parafunctions and changes in the Central Nervous System (CNS). Potential and common methods of treatment are presented, along with suggested guidelines that should be followed when determining an appropriate treatment method. We draw attention to the notably dynamic development of bruxism in today's society and the importance of informational and preventive projects, especially those targeted at high-risk patients as well as those targeted at specialists, in order to better tackle the bruxism 'epidemic'.

Topology of pain networks in patients with temporomandibular disorder and pain-free controls with and without concurrent experimental pain: A pilot study

Temporomandibular disorders (TMD) involve chronic pain in the masticatory muscles and jaw joints, but the mechanisms underlying the pain are heterogenous and vary across individuals. In some cases, structural, functional, and metabolic changes in the brain may underlie the condition. In the present study, we evaluated the functional connectivity between 86 regions of interest (ROIs), which were chosen based on previously reported neuroimaging studies of pain and differences in brain morphology identified in an initial surface-based morphometry analysis. Our main objectives were to investigate the topology of the network formed by these ROIs and how it differs between individuals with TMD and chronic pain (n = 16) and pain-free control participants (n = 12). In addition to a true resting state functional connectivity scan, we also measured functional connectivity during a 6-min application of a noxious cuff stimulus applied to the left leg. Our principal finding is individuals with TMD exhibit more suprathreshold correlations (higher nodal degree) among all ROIs but fewer "hub" nodes (i.e., decreased betweenness centrality) across conditions and across all pain pathways. These results suggest is this pain-related network of nodes may be "over-wired" in individuals with TMD and chronic pain compared to controls, both at rest and during experimental pain.

Pediatric Chronic Orofacial Pain: A Narrative Review of Biopsychosocial Associations and Treatment Approaches

Pediatric chronic orofacial pain (OFP) is an umbrella term which refers to pain associated with the hard and soft tissues of the head, face, and neck lasting >3 months in patients younger than 18 years of age. Common chronic pediatric OFP diagnoses include temporomandibular disorder, headaches, and neuropathic pain. Chronic OFP can adversely affect youth's daily functioning and development in many areas of well-being, and may be associated with emotional stress, depression, functional avoidance, and poor sleep, among other negative outcomes. In this mini-review, we will discuss common psychological comorbidities and familial factors that often accompany chronic pediatric OFP conditions. We will also discuss traditional management approaches for pediatric orofacial pain including education, occlusal appliances, and psychological treatments such as relaxation, mindfulness-based interventions, and cognitive-behavioral treatments. Finally, we highlight avenues for future research, as a better understanding of chronic OFP comorbidities in childhood has the potential to prevent long-term pain-related disability in adulthood.

The Role of TNF-α in the Pathogenesis of Temporomandibular Disorders

Temporomandibular disorder (TMD) is an oral dentofacial disease that is related to multiple factors such as disordered dental occlusion, emotional stress, and immune responses. In the past decades, tumor necrosis factor-alpha (TNF-α), a pleiotropic cytokine, has provided valuable insight into the pathogenesis of TMD, particularly in settings associated with inflammation. It is thought that TNF-α participates in the pathogenesis of TMD by triggering immune responses, deteriorating bone and cartilage, and mediating pain in the temporomandibular joint (TMJ). Initially, TNF-α plays the role of "master regulator" in the complex immune network by increasing or decreasing the production of other inflammatory cytokines. Then, the effects of TNF-α on cells, particularly on chondrocytes and synovial fibroblasts, result in pathologic cartilage degradation in TMD. Additionally, multiple downstream cytokines induced by TNF-α and neuropeptides can regulate central sensitization and inflammatory pain in TMD. Previous studies have also found some therapies target TMD by reducing the production of TNF-α or blocking TNF-α-induced pathways. All this evidence highlights the numerous associations between TNF-α and TMD; however, they are currently not fully understood and further investigations are still required for specific mechanisms and treatments targeting specific pathways. Therefore, in this review, we explored general mechanisms of TNF-α, with a focus on molecules in TNF-α-mediated pathways and their potential roles in TMD treatment. In view of the high clinical prevalence rate of TMD and damage to patients' QOL, this review provides adequate evidence for studying links between inflammation and TMD in further research and investigation.

Adaptive Stress Coping in Awake Bruxism

Numerous studies have analyzed the relationship between psychological factors and bruxism. However, the data are often obscured by the lack of precise diagnostic criteria and the variety of the psychological questionnaires used. The purpose of this study is to determine the association between awake bruxism and psychological factors (anxiety, depression, sociability, stress coping, and personality traits). With this aim, 68 participants (13 males) completed a battery of psychological questionnaires, a self-reported bruxism questionnaire, and a clinical examination. Based on their scores on the bruxism questionnaire and the clinical examination, subjects were divided into two groups. Subjects who met the criteria for “probable awake bruxism” were assigned to the case group (n = 29, five males). The control group (n = 39, nine males) was composed of subjects who showed no signs or symptoms of bruxism in the examination nor in the questionnaire. The probable awake bruxism group presented significantly higher levels of trait and state anxiety, symptoms of somatization, and neuroticism than the control group. Despite this, and when their problem coping strategies were considered, awake bruxers showed higher levels in Positive Reappraisal (p < 0.05), a strategy generally considered as adaptive. In conclusion, although awake bruxers in our study showed larger levels of anxiety, somatization, and neuroticism, they also displayed more adapted coping strategies, while according to previous data TMD patients (which generally also present high levels of anxiety, somatization and neuroticism) might tend to present less adaptive coping styles. Thus, awake bruxism may play a positive role in stress coping, which would be compatible with the hypothesis of mastication as a means of relieving psychological tension. This finding should be further confirmed by future research comparing TMD patients with definitive awake bruxers and controls and using larger and more representative samples.

Manifestation of stress and anxiety in the stomatognathic system of undergraduate dentistry students

Objective

To assess the relationship between psychoemotional state and signs of oral cavity occlusal and nonocclusal parafunctions, together with masseter muscle tone, in undergraduate dentistry students.

Methods

The study population comprised first and fifth grade dentistry students who were investigated using psychological and health questionnaires, and stomatological examination with electromyography of the masseter muscles. Differences in variables between first and fifth grade students were analysed using Student’s t-test or χ²-test and Pearson’s correlation coefficient was used to analyse associations between variables.

Results

A total of 113 students (52 first-grade, mean age 20 years; and 61 fifth-grade, mean age 23.6 years) were included. Older age was associated with lower level of perceived stress and anxiety. Moreover, a significant positive relationship was observed between level of perceived stress and anxiety and tone of both masseter muscles.

Conclusions

Increased psychoemotional burden and increased rates of experienced anxiety were associated with growth of masseter muscle tone in this study population.

Biomechanical behaviour of temporomandibular joints during opening and closing of the mouth: A 3D finite element analysis

Temporomandibular joints (TMJs) constitute a pair of joints that connect the jawbone to the skull. TMJs are bilateral joints which work as one unit in conducting daily functions such as speaking, mastication, and other activities associated with the movement of the jaw. Issues associated with the TMJs may arise due to various factors-one such factor being the internal load on the TMJ. These issues may contribute to temporomandibular disorders (TMD). This study aims to evaluate the mandibular trajectories and the associated stress changes during the process of opening the mouth on the TMJs of an asymptomatic subject. The mouth opening motion was recorded by a motion capturing system using models of the mandible and maxilla constructed based on the computed tomography (CT). Two discs constructed based on magnetic resonance imaging (MRI). Finite element analysis was performed on the relative motion of the mandible to the maxilla and validated. The process modelled by these displacements provided less than 10% error in terms of deformation. The simulation results indicate that the lateral intermediate zone-the head and neck of the mandible-and the articular eminence sustained the most significant stresses during the mouth opening motion. The results also suggested that the stresses increase as the range of opening increases with the greatest von Mises stress, tensile, and compressive stress found at the position of maximal opening.

Effect of sagittal split ramus osteotomy on stress distribution of temporomandibular joints in patients with mandibular prognathism under symmetric occlusions

Sagittal split ramus osteotomy (SSRO) is the representative orthognathic surgery for the patients with mandibular prognathism. It is essential to understand the biomechanical environment of temporomandibular joint (TMJ) to analyse the effects of SSRO. This study aimed to investigate the influence of SSRO on the stress distributions in the TMJs of the patients with mandibular prognathism under symmetric occlusions. Thirteen patients with mandibular prognathism and ten asymptomatic volunteers were recruited. Finite element models of the asymptomatic, preoperative, and postoperative subjects were established, based on the CT of the asymptomatic volunteers and preoperative and postoperative scans of patients with mandibular prognathism. Contact was used to simulate the interactions between discs and articular surfaces, and between the upper and lower dentition. Muscle forces and boundary conditions corresponding to the centric and anterior occlusions were applied on the models. Under both occlusions, the maximum and minimum principal stresses of the articular disc and condyle in the preoperative group were significantly greater than those in the control group. After SSRO, the maximum and minimum principal stresses of the articular disc and condyle of the patients under both occlusions were greatly reduced, but the principal stresses of the articular disc were not significantly higher than those in the control group. Mandibular prognathism led to excessive stress on the TMJ. Severe asymmetric compression between the TMJs on both sides might cause temporomandibular disorder (TMD) symptoms. SSRO could improve the stress distribution of the TMJ and partially relieve the symptoms of TMD.

Prediction of painful temporomandibular joint osteoarthritis in juvenile patients using bone scintigraphy

The study aims to evaluate whether bone scintigraphy is effective in diagnosing temporomandibular joint (TMJ) osteoarthritis (OA) in juvenile patients. A retrospective study was conducted with 356 consecutive patients with TMJ-OA who were clinically assessed according to the Research Diagnostic Criteria for Temporomandibular Disorders. Patients were assigned to three groups based on their ages: Group 1: aged 12-16 years; Group 2: aged 17-19 years; and Group 3: aged 20 years. Additionally, we performed qualitative and quantitative analyses of bone scintigraphy images for the TMJ uptake ratio of the involved joint. The diagnostic rate of TMJ-OA (n = 356, 100%), and the overall presence of subjective pain (n = 282, 77.3%) was closest to the results of bone scintigraphy (n = 333, 91.2%). In addition, reported TMJ pain was significantly associated only with the results of bone scintigraphy and not with the results of panoramic radiography or cone beam computed tomography (CBCT) in all age groups. With CBCT as the reference standard, the optimal cutoff values of the uptake ratio for the diagnosis of TMJ-OA were 2.171 and 2.017 in Groups 1 and 2, respectively (P value < 0.05). Our results suggest that bone scintigraphy can be considered a useful modality for diagnosing TMJ-OA in juvenile patients.

Norepinephrine Regulates Condylar Bone Loss via Comorbid Factors

Degenerative changes of condylar subchondral bone occur frequently in temporomandibular disorders. Although psychologic stresses and occlusal abnormalities have been implicated in temporomandibular disorder, it is not known if these risks represent synergistic comorbid factors that are involved in condylar subchondral bone degradation that is regulated by the sympathetic nervous system. In the present study, chronic immobilization stress (CIS), chemical sympathectomy, and unilateral anterior crossbite (UAC) were sequentially applied in a murine model. Norepinephrine contents in the subjects' serum and condylar subchondral bone were detected by ELISA; bone and cartilage remodeling parameters and related gene expression in the subchondral bone were examined. Subchondral bone loss and increased subchondral bone norepinephrine level were observed in the CIS and UAC groups. These groups exhibited decreased bone mineral density, volume fraction, and bone formation rate; decreased expressions of osterix, collagen I, and osteocalcin; but increased trabecular separation, osteoclast number and surface, and RANKL expression. Combined CIS + UAC produced more severe subchondral bone loss, higher bone norepinephrine level, and decreased chondrocyte density and cartilage thickness when compared to CIS or UAC alone. Sympathectomy simultaneously prevented subchondral bone loss and decreased bone norepinephrine level in all experimental subgroups when compared to the vehicle-treated counterparts. Norepinephrine also decreased mRNA expression of osterix, collagen I, and osteocalcin by mesenchymal stem cells at 7 and 14 d of stimulation and increased the expression of RANKL and RANKL/OPG ratio by mesenchymal stem cells at 2 h. In conclusion, CIS and UAC synergistically promote condylar subchondral bone loss and cartilage degradation; such processes are partially regulated by norepinephrine within subchondral bone.