Functional changes of the lateral pterygoid muscle in patients with temporomandibular disorders: a pilot magnetic resonance images texture study.

BACKGROUND: Texture features were the intrinsic properties of the human tissues and could efficiently detect the subtle functional changes of involved tissue. The pathologic changes of the lateral pterygoid muscle (LPM) were significantly correlated with the temporomandibular disc displacement. However, the occult functional changes of LPM could not be detected by the naked eye on the medical images. The current study was aimed to evaluate the functional changes of the LPM in the patients with temporomandibular disorders (TMDs) using texture analysis. METHODS: Twenty-nine patients with TMD were performed with magnetic resonance (MR) imaging on a 3.0T MR scanner, who were consecutively recruited from the TMD clinic of Hainan Hospital of Chinese People's Liberation Army General Hospital from February 2019 to September 2019. The patients were classified into three groups according to the disc displacement: disc without displacement (DWoD), disc displacement with reduction (DDWR) and disc displacement without reduction (DDWoR). The gray-level co-occurrence matrix method was applied with the texture analysis of LPM on the axial T2-weighted imaging. The texture features included angular second moment, contrast, correlation, inverse different moment, and entropy. One-way analysis of variance was used for grouped comparisons and receiver operating characteristics (ROC) curve analysis was applied to evaluate the diagnostic efficacy of the texture parameters. RESULTS: Texture contrast of LPM presented significantly lower in DDWoR (46.30 [35.03, 94.48]) than that in DWoD (123.85 [105.06, 143.23]; test statistic = 23.05; P < 0.001). Texture entropy of LPM showed significant differences among DWoD (7.62 ±â€Š0.33), DDWR (6.76 ±â€Š0.35), and DDWoR (6.46 ±â€Š0.39) (PDWoD-DDWR < 0.001, PDWoD-DDWoR < 0.001, and PDDWR-DDWoR = 0.014). Area under the ROC curve (AUC) demonstrated that texture entropy had an excellent diagnostic accuracy for DWoD-DDWR (AUC = 0.96) and DWoD-DDWoR (AUC = 0.98). CONCLUSION: The texture contrast and entropy could identify the altered functional status of LPM in patients with TMD and could be considered as the effective imaging biomarker to evaluate the functional changes of LPM in TMD.

Injury responses of Sprague-Dawley rat jaw muscles to an experimental unilateral anterior crossbite prosthesis.

OBJECTIVE: Dental occlusion are frequently changed in clinic. Molecular responses in jaw muscles to aberrant dental occlusion are changes are attractive, yet remain are obscure. DESIGN: Unilateral anterior crossbite (UAC) prostheses were applied to Sprague-Dawley rats and then ceased after two weeks to detect the reactions of the masseter, a representative jaw elevator, and the lateral pterygoid muscle (LPM), a representative jaw depressor. RESULTS: Two weeks of UAC elicited mild injury of the two muscles. Myogenesis and protective reactions were detected as increases in αB-crystallin expression in the masseter after 3 days and in the LPM after 2 weeks, and increases in desmin expression in both muscles after 2 weeks. A switch in fibre types from IIb to IIx occurred in the LPM but not in the masseter. Inflammatory responses, shown by the infiltration of inflammatory cells and increases in TNF-α mRNA expression, and fibrosis responses, shown by increased mRNA expression of Type I and III collagens, appeared very mild in the two muscles. These responses were partially recovered by the cessation of UAC. During the whole process, no obvious changes were observed in mitochondrial function, as indicated by the levels of proliferator-activated receptor γ coactivator 1α, mitofusin-2 and voltage-dependent anion channel. CONCLUSIONS: UAC causes injury and very limited inflammatory and fibrosis adaption in the masseter and LPM. Both muscles respond with myogenesis and protective activity. The LPM responds also with muscle fibre isoform alternations. These alterations were partially recovered by the cessation of dental stimulation at an early stage.

Pathoanatomical characteristics of temporomandibular dysfunction: Where do we stand? (Narrative review part 1).

Temporomandibular dysfunction (TMD) is a complicated and multifactorial condition that affects the temporomandibular joint (TMJ) and muscles of mastication, resulting in pain and disability in 5-12% of the population. The condition involves genetic, anatomic and hormonal factors and is propagated, in part, by trauma, habitual activity, psychosocial components and occlusal variation. Yet, the exact etiology of TMD is still unknown and the most strategic conservative management of the condition is still a topic of debate. The purpose of this paper, the first of a two part series, is to provide greater insight into the pathoanatomical factors associated with TMD. Consistent with Scully (2008, 2013), degenerative changes seem to disrupt the relationship between the TMJ capsule, articular disc and muscles of mastication. The resulting position of the articular disc coincides with three primary classifications of TMD: Type 1 (muscle disorders), Type 2a/b (disc displacement with and without reduction), and Type 3 (any joint pain). Given the association of the lateral pterygoid with both the joint capsule and articular disc, the superior and inferior head seem to play a key role in TMD. Both heads undergo biological changes associated with the vicious cycle, pain adaptation and integrated pain adaptation, making the muscle a key pain generator associated with TMD. Clinicians must understand the pathoanatomic features associated with TMD so as to choose appropriate treatment strategies, leading to optimal short and long-term outcomes. While the former is discussed in part 1 of this narrative review, the latter will be considered in part 2.

Conservative management of temporomandibular dysfunction: A literature review with implications for clinical practice guidelines (Narrative review part 2).

The effective management of temporomandibular dysfunction (TMD) requires a thorough understanding of the pathoanatomic factors that drive the underlying condition. After reviewing the etiology associated with TMD in Part 1 of this narrative review, the temporomandibular joint capsule, articular disc and muscles of mastication emerged as key players. (http://dx.doi.org/10.​1016/​j.​jbmt.​2017.​05.​017) Part 2 focuses on conservative treatment strategies best able to reduce the pain and disability associated with TMD. A review of the literature revealed limited support of strengthening exercises targeting the muscles of mastication. There was also limited evidence for manual soft tissue work targeting muscles of mastication, which may be specifically related to the limited accessibility of the pterygoid muscles to palpation. For the reduction of pain, there was little to no evidence supporting splint therapy and electrophysical modalities, including laser therapy, ultrasound, TENs and iontophoresis. However, for the reduction of pain and disability, non-thrust mobilization and high-velocity, low amplitude thrust manipulation techniques to the TMJ and/or upper cervical articulations that directly and indirectly target the TMJ joint capsule were generally supported in the literature. Studies that used dry needling or acupuncture of the lateral pterygoid and posterior, peri-articular connective tissue also led to significant improvements in pain and disability in patients with TMD. Thus, the most effective conservative management of TMD seems to be techniques best able to impact anatomic structures directly related to the etiology of TMD, to include the joint capsule, articular disc and muscles of mastication, specifically the superior and inferior head of the lateral pterygoid.

Restricted Mandibular Movement Attributed to Ossification of Mandibular Depressors and Medial Pterygoid Muscles in Patients With Fibrodysplasia Ossificans Progressiva: A Report of 3 Cases.

Fibrodysplasia ossificans progressiva (FOP) is an extremely rare genetic condition characterized by congenital malformation and progressive heterotopic ossification (HO) caused by a recurrent single nucleotide substitution at position 617 in the ACVR1 gene. As the condition progresses, HO leads to joint ankylosis, breathing difficulties, and mouth-opening restriction, and it can shorten the patient's lifespan. This report describes 3 cases of FOP confirmed by genetic testing in patients with restricted mouth opening. Each patient presented a different onset and degree of jaw movement restriction. The anatomic ossification site of the mandibular joint was examined in each patient using reconstructed computed tomographic (CT) images and 3-dimensional reconstructed CT (3D-CT) images. A 29-year-old woman complained of jaw movement restriction since 13 years of age. 3D-CT image of the mandibular joint showed an osseous bridge, formed by the mandibular depressors that open the mouth, between the hyoid bone and the mentum of the mandible. A 39-year-old man presented with jaw movement restriction that developed at 3 years of age after a mouth injury. 3D-CT image of the jaw showed ankylosis of the jaw from ossification of the mandibular depressors that was worse than in patient 1. CT images showed no HO findings of the masticatory muscles. To the authors' knowledge, these are the first 2 case descriptions of the anatomic site of ankylosis involving HO of the mandibular depressors in the jaw resulting from FOP. In contrast, a 62-year-old bedridden woman with an interincisal distance longer than 10 mm (onset, 39 years of age) had no HO of the mandibular depressors and slight HO of the medial pterygoid muscle on the right and left sides. These findings suggest that restricted mouth opening varies according to the presence or absence of HO of the mandibular depressors.

Postero-inferior condylar movement induced by artificial occlusal interference on the balancing side during fictive mastication in rabbits.

OBJECTIVE: Tooth contact does not occur on the balancing side during mastication. Hence, it is possible that the presence of occlusal interference on the balancing side causes mandibular rotation followed by atypical condylar movement because the jaw-closing muscle activity on the working side is greater than on the balancing side. The aim of the present study was to investigate the relationship between occlusal contact on the balancing side and condylar movement during mastication. METHODS: EMG activity of the masseter (MS), lateral pterygoid (LP) and digastric (DG) muscles and jaw movements were recorded. Condylar movements in the sagittal plane were recorded using a high speed charge-coupled device (CCD) camera. Incisal point movements were recorded using a magnet on the mentum and a magnetometric sensor on the nasal bone. A removable biting plate was used to introduce an artificial occlusal interference on the balancing side. RESULTS: Nine of the 10 rabbits showed large postero-inferior condylar movement (Pi-Cm) when a biting plate was applied on the balancing side. Five rabbits showed very small Pi-Cm when a biting plate was applied on the balancing side. In the small Pi-Cm group, MS activity decreased markedly and LP and DG transient activity appeared in the early occlusal phase in the presence of the biting plate. CONCLUSION: Interference on the balancing side always caused Pi-Cm on the ipsilateral side during mastication. However, the degree of Pi-Cm was often decreased by a jaw opening reflex response.

Modeling of muscle forces in humans with and without temporomandibular joint disorders.

OBJECTIVES: Subjects with/without temporomandibular joint disorders (TMJD) were tested for differences in muscle forces. SETTING AND SAMPLE POPULATION: School of Dental Medicine, University at Buffalo. Ninety-one subjects were classified in four groups based on the presence/absence (±) of chronic myofascial and/or TMJ pain (P) and bilateral disc displacement (DD). MATERIAL AND METHODS: Validated numerical models employed an organizational objective and subjects' anatomy to calculate masticatory muscle forces during static biting. anova and Holm's step-down procedure post hoc tests assessed group differences. Theoretical geometries, representing the range of subjects' muscle orientations, were surveyed via numerical models to identify key combinations resulting in high muscle forces. Effect size (Cohen's d) and anova/post hoc tests assessed group differences in key muscle orientations. RESULTS: +P-DD subjects had significantly higher muscle forces, especially for lateral pterygoid muscles, compared to the other groups (p<0.01) for bite forces that were directed posteromedially or posterolaterally on mandibular molars and posteriorly and slightly medially on mandibular incisors. Key muscle orientations for peak lateral pterygoid muscle forces were identified, and group comparisons showed mean orientation in +P-DD compared to other diagnostic groups was ≥5° more upright for masseter and ≥3° more posteriorly directed for temporalis muscles (all Cohen's d≥0.8). CONCLUSION: Predicted lateral pterygoid muscle forces were significantly higher in +P-DD compared to other groups for specific biting conditions and were attributable, in part, to differences in masseter and temporalis muscle orientations.

Treatment of mandibular symphyseal fracture combined with dislocated intracapsular condylar fractures.

OBJECTIVES: To evaluate the treatment methods of mandibular symphyseal fracture combined with dislocated intracapsular condylar fractures (MSF&DICF) and to compare the effect of different treatment methods of condylar fractures. METHODS: Twenty-eight patients with MSF&DICF were included in this study. Twenty-two sites were treated by open reduction, and all the medial condylar fragments were fixed with titanium screws; whereas the other 22 sites underwent close treatment. The surgical effect between these 2 groups was compared based on clinical examination and radiographic examination results. RESULTS: Seventeen of 22 condyle fractures were repositioned in the surgery group, whereas 4 of 22 condyle fractures were repositioned in the close treatment group. Statistical difference was observed between these 2 groups (P < 0.01). Functional outcomes of the patients treated in the surgical treatment group also were better than those in the close treatment group. CONCLUSIONS: The dislocated intracapsular condyle fractures should be treated by surgical reduction with the maintenance of the attachment of lateral pterygoid muscle, which is beneficial to repositioning the dislocated condyle to its original physiological position, to closure of the mandibular lingual gap, to restore the mandibular width.

Evaluation of stress changes in the mandible with a fixed functional appliance: a finite element study.

INTRODUCTION: The aim of this study was to evaluate the effects of a fixed functional appliance (Forsus Fatigue Resistant Device; 3M Unitek, Monrovia, Calif) on the mandible with 3-dimensional finite element stress analysis. METHODS: A 3-dimensional finite element model of the mandible was constructed from the images generated by cone-beam computed tomography of a patient undergoing fixed orthodontic treatment. The changes were studied with the finite element method, in the form of highest von Mises stress and maximum principal stress regions. RESULTS: More areas of stress were seen in the model of the mandible with the Forsus compared with the model of the mandible in the resting stage. CONCLUSIONS: This fixed functional appliance studied by finite element model analysis caused increases in the maximum principal stress and the von Mises stress in both the cortical bone and the condylar region of the mandible by more than 2 times.

Is the incidence of temporomandibular disorder increased in polycystic ovary syndrome?

The prevalence of temporomandibular disorders is higher among women than men (ratio 3:1 -9:1). Polycystic ovary syndrome(PCOS) is the most common endocrine disorder in women, which is characterised by chronic low-grade inflammation and excess of androgenic hormones that lead to metabolic aberrations and ovarian dysfunction. Increased activities of various matrix metalloproteinases (particularly MMP-2 and 9) in the serum of these patients has been reported, and it has been hypothesised that high activities of MMP may contribute to loss of matrix and chronic inflammation of the fibrocartilage in temporomandibular disorders. Our aim was to evaluate the incidence of temopormandibular dysfunction in women with PCOS compared with an age-matched, disease-free, control group. We studied 50 patients with previously diagnosed PCOS and 50 volunteers who had normal menstrual cycles. We made a comprehensive clinical examination of the temporomandibular joint (TMJ) and muscles of mastication in both groups and recorded the Visual Analogue Scores (VAS) for pain. There were significant differences (p<0.001) in the incidence of temporomandibular disorders (n=43 (86%) in the PCOS group compared with n=12 24% in the control group), muscle tenderness(n=32 (64%) in the PCOS group compared with n=14 (28%) in the control group) and pain in the TMJ (mean (SD) VAS 2.9 (2.61) compared with 0.3 (1.56). We confirm the higher incidence and severity of disorders of the TMJ in patients with PCOS and suspect that chronic low-grade inflammation may play a part in the aetiology of the disease.

Biomechanical analysis of fractures in the mandibular neck (collum mandibulae).

After treatment of fractures in the neck of the mandible by means of immobilization of the dentition, often more or less severe manifestations of malocclusion remain. It was hypothesized that this is caused by an altered articulation in the jaw joint on the affected side. Furthermore, it was hypothesized that an anteriorly displaced condyle, as observed frequently as a side effect of the treatment, is caused by pull of the lateral pterygoid muscle, despite maxillomandibular fixation. Intervention experiments were performed in silico to test these hypotheses. With a biomechanical model of the human masticatory system alterations were applied mimicking a fractured mandibular neck and configurations that had been observed after healing. It was predicted that the altered articulation in the jaw joint caused asymmetrical jaw movements despite symmetrical muscle activation. The jaw was predicted to close with an open bite similar to clinical observations. The predicted laterodeviations, however, were not in accordance with clinical observations. Despite maxillo-mandibular fixation the lateral pterygoid muscle was able to pull the mandibular condyle out of its fossa in anterior direction. Consequently, despite some methodological limitations, in general the predictions corroborated the hypotheses.

A rare isolated unilateral myositis ossificans traumatica of the lateral pterygoid muscle: a case report.

INTRODUCTION: Myositis ossificans traumatica is a pathological condition characterized by the extraskeletal formation of bony tissue, induced by violent or repeated trauma. CASE PRESENTATION: A 30-year-old Italian man, after surgical treatment for multiple facial fractures, presented with a progressive limitation of mouth opening. A computed tomography scan showed a significant calcification of the fibers of the left lateral pterygoid muscle. The working diagnosis was myositis ossificans traumatica of the left lateral pterygoid muscle. Surgical excision was suggested but not performed. Our patient underwent physiotherapy treatment resulting not in a complete restoration of mandibular movements but in an acceptable recovery of mouth opening. CONCLUSIONS: Myositis ossificans is a rare complication that can be caused by muscle trauma. Therefore, special attention should be paid to surgical trauma. In the present case, surgical excision was considered, in accordance with the literature, and suggested to our patient, but he declined due to the absence of any pain or any significant limitation to his daily life activities. He therefore underwent physiotherapy treatment, in line with our unit's guidelines, resulting not in a complete restoration of mandibular movements but in an acceptable recovery of mouth opening.

Tooth displacement in shortened dental arches: a three-dimensional finite element study.

STATEMENT OF PROBLEM: Some patients may opt for a prosthetic rehabilitation without replacing all missing teeth, finishing treatment with a reduced dental arch. This choice may be due to biologic reasons or financial restrictions. It is unclear if a reduced dental arch functions as well as a complete dental arch. PURPOSE: The purpose of this study was to analyze whether shortened dental arches could result in tooth displacement. MATERIAL AND METHODS: Four different 3-dimensional maxillary and mandibular arches with different levels of arch length reduction were created. In all models, anatomic structures that represent the temporomandibular joint, cortical and cancellous bone, enamel, dentin, and periodontal ligament were modeled. Mechanical properties were attributed to each anatomic component, and a total occlusal load of 100 N on masseter, temporal, and medial pterygoid muscles was simulated for each model. The MSC. Patran software was used for the preprocessing and postprocessing of the biomechanical analysis of the models. One complete dental arch was used as the control. RESULTS: The simulations showed that shortened dental arches presented greater tooth displacements than those found in a complete dental arch. The changes in mandibular tooth position were greater than those observed in the maxillary arches. In finite element models 1 and 2, the largest maxillary displacements were found for posterior teeth. CONCLUSIONS: Decreasing numbers of occlusal units resulted in increasing amounts of displacements of the remaining teeth, which may compromise dental stability in patients with shortened dental arches.

Clinical study on the comparison of masticatory efficiency and jaw movement before and after temporomandibular disorder treatment.

In this clinical study, pre- and post-rehabilitation changes in intraborder mandible movements, chewing cycles, masticatory efficiencies, and borders of the chewing area of patients with unilateral muscular disorders (MD) (n = 20) or unilateral disc derangement disorders (DDD) (n = 20) of temporomandibular disorder (TMD) were observed and compared with healthy individuals with full dentition (n = 20) (48 female, 12 male; mean age: 28). The MD patients received stabilization splints and the DDD patients, anterior positioning splints for six weeks. Symptoms, such as muscle pain, TMJ pain, headache, chewing difficulty, and maximum mouth opening, showed significant improvements after splint therapy for both MD (p = 0.000) and DDD (p = 0.000) patients, but lateral excursion and protrusion were not significantly changed (p > 0.05). Chewing efficacy and chewing cycles improved significantly (p < 0.05) in both the MD (p < 0.05) and DDD (p < 0.05) groups, but only the MD group was comparable to the control group after treatment. Pre- and post-rehabilitation chewing cycles along the frontal plane on both sides in the MD group were similar to the control group. Considering the majority of the improvements in the diagnostic measures, patients with MD and DDD may benefit from occlusal splint therapy.

Síndrome del Hamulus Pterigoideo / Pterygoid Hamulus Syndrome

El síndrome del Hamulus Pterigoideo se produce por una bursitis en el tendón del músculo tensor del velo del paladar. Presenta una patología dolorosa y muy variada dada la complejidad de la región y muchas veces este dolor puede enmascarar diferentes patologías que hay que diagnosticar y diferenciar. El tratamiento es multidisciplinario en muchos de los casos (AU)

The Pterygoid Hamulus Syndrome is produced by bursitis in the tendon of the tensormuscle of the soft palate. It presents a painful and varied pathology given the complexity of the region and many times this pain can mask different pathologies that must be diagnosed and differentiated. The treatment is multidisciplinary in many of the cases (AU)

Long-term outcome assessment of closed treatment of mandibular fractures.

Mandibular fractures are among the most common trauma injuries of the craniomaxillofacial region. This study evaluated the late results of mandibles fractures treated with arch bar. Forty-nine patients were examined clinically and by questionnaires for late results of arch bar treatment. Demographic data (age, sex, etc), trigeminal nerve sensation (Weber test), temporomandibular joint evaluation, masticatory muscle function, and occlusion were recorded. The data were analyzed by χ test using Sigma Stat 2.0 software. Fifty-one percent of the patients with angular fractures complained of sensory disturbances. Condylar and angular fractures demonstrated higher levels of pain. According to Pearson χ test, a statistically significant relation between angular fracture and tenderness of the internal pterygoid muscles (P = 0.047), angular fracture and cross-bite (P = 0.021), parasymphysial fracture and pain upon wind blowing (P = 0.026), and body fracture and mastication discomfort (P = 0.038) was found. In closed reduction therapy, fracture location of the mandible seems to be more likely correlated in producing particular long-term complications. Regular follow-ups for functional treatments and physiotherapy of chewing muscles and temporomandibular joint, along with removal of occlusal abnormalities, should be considered following arch bar reduction of mandibular fractures.

[The theoretical substantiation of myofunctional correction of sagittal occlusion abnormalities and temporomandibular joint dysfunction].

Simulation in 3D-model of skeletal forms of sagittal malocclusion revealed tendency in tonus' modification of muscles of mastication in formation of distal and mesial occlusion. It's shown that distal occlusion is characterized by hypotonic condition of muscles of mastication, except posterior fibers of temporal muscle. Mesial occlusion is characterized by complex combination of muscle tone with prevalence of hypotonic condition of anterior fibers of temporal muscle, superficial portion of masseter muscle and medial pterygoid muscle. We have detected that using of myofunctional devices in treatment of sagittal malocclusion, temporomandibular joint dysfunction promotes of tone increasing of muscles of mastication.

[Classification and clinical characteristics of masticatory myospasm].

OBJECTIVE: To determine the classification of masticatory myospasm by analyzing characteristics of clinical appearances. METHODS: Thirty-six cases of masticatory myospasm from 2000 to 2010 were included. The clinical data of these patients were analyzed, including patient information, patient history, clinical characteristics, severity and the frequency of myospasmodic movement, electromyogram (EMG), and the efficacy of botulinum toxin injection treatment. RESULTS: There were 11 males and 25 females, aged from 15 to 71. According to the clinical manifestation and EMG findings, patients could be divided into two groups: 18 cases were classified as jaw closing type which involved masseter and/or temporalis muscles presenting as trismus and acute pain, the other 18 cases were jaw opening type which involved lateral pterygoid muscles complaining difficulty in jaw closing and teeth clenching. The jaw closing type was often seen in patients of 20 to 50 years old, the jaw opening was frequently seen in patients over 50 years old. Jaw closing type was attacked intermittently and unilaterally, but jaw opening was often attacked continually and bilaterally. The rating scale of the severity of spasmodic movement was not different between the two types, but the frequency of spasmodic attack was much higher for jaw opening type (P < 0.05). The EMG of jaw closing type was classified into persistent, rhythmic and irregular type. The EMG of jaw opening type was classified into spontaneous and exercise-induced type. Twelve cases were treated by botulinum toxin injection that could significantly relieve symptoms. CONCLUSIONS: Masticatory myospasm can be classified into jaw closing and jaw opening types. Jaw closing type involves masseter and/or temporalis muscles and jaw opening type involves lateral pterygoid muscles. Botulinum toxin injection was the most effective therapy for the masticatory myospasm.