Research is continuing on the anatomical elements, tissues and pathophysiological system of myalgia and fascial and myofascial pain. In the early 21st century, many fundamental researches and clinical studies on the trunks and limbs of humans and animals have been carried out and have revealed new findings and understanding about myalgia and myofascial pain. For example, the concept that lactic acid is a fatigue substance has been disproved, and the existence and influence of hypodermis - subcutaneous fascia spread over fascia of muscular system - have been shown. This article introduces the evidence, hypotheses and prospects for understanding and dealing with local myalgia and fascial and myofascial pain for temporomandibular disorders.

Therapeutic exercise increases range of motion, decreases pain, and shortens the duration of symptoms. However, few studies have assessed the effectiveness of therapeutic exercise by using quantitative methods. In this study, we prescribed a range of temporomandibular joint motion exercises involving both passive exercises performed by a dentist and self-traction therapy performed by the patient, and evaluated the short-term effectiveness of the treatment in patients with temporomandibular joint anterior disc displacement without reduction.

We enrolled 45 patients who had moderate or severe TMJ function. We asked them to perform therapeutic exercises and evaluated their clinical symptoms (maximum opening distance, pain at rest, pain on motion, pain on mastication, and degree of difficulty in performing activities of daily living) at the first visit and at the first follow-up visit approximately 2 weeks later.

The results demonstrated statistically significant improvements in maximum opening distance, pain on motion, pain on mastication and degree of difficulty in performing activities of daily living (p<0.001). The positive outcomes were considered the result of improvements in range of joint motion and expansion of the joint cavity, resulting in smoother movement of the condylar translation. The results of this study suggest that our therapeutic exercise program is a potentially beneficial conservative treatment for the short-term reduction of symptoms accompanying temporomandibular joint anterior disc displacement without reduction.

Tooth contacting habit (TCH) has been attracting attention as a contributing factor for temporomandibular disorders. However, only a few randomized controlled studies have analyzed the effectiveness of corrective interventions for TCH, and even fewer studies have reported on such interventions by dental hygienists. This study aimed to examine the effect of behavior modification support by dental hygienists for patients with masticatory myalgia. The patients were randomly assigned to intervention and control groups (n = 14 for each). A single dental hygienist used a behavior modification approach using a "poster method" for all the patients. The effect was considered in terms of pain-free opening, maximum unassisted opening, maximum assisted opening, muscle pain with palpation, current pain, past one-week maximal pain and past one-week average pain. At the second follow-up, the intervention group patients showed significant improvement in pain-free opening, maximum assisted opening, and muscle pain with palpation compared with at the first follow-up; however, only pain-free opening and maximum unassisted opening were significantly improved in the control group patients at the first follow-up. By comparison between the intervention group and control group at the second visit, a significant difference was found in the past one-week maximal pain and in the past one-week average pain (p<0.05).

Behavior modification support by dental hygienists was effective in alleviating the symptoms in patients with masticatory myalgia. Moreover, in a questionnaire survey administered to the patients, most intervention group patients responded that they were able to modify their behavior, suggesting the ease and usefulness of interventions by dental hygienists. Therefore, the results of the present study indicate that behavior modification support by dental hygienists is a useful intervention in patients with masticatory muscle disorders.

A 71-year-old female presented to our hospital with disturbance of mouth opening, pain around the right TMJ region and bilateral posterior open bite. She had been treated for apical periodontitis of the upper second molar on the right side 10 days earlier under local anesthesia. On the first examination the maximum range of mouth opening was 25 mm and there was no TMJ clicking. Although occlusion is notable for bilateral posterior open bite, obvious signs of inflammation such as facial swelling or redness were not observed. Although the tentative diagnosis was temporomandibular joint disease, subsequent MR (T2 weighted) imaging revealed a high-intensity area at the right lateral pterygoid muscle. Furthermore, laboratory analysis revealed an abnormally high WBC count and CRP levels. Accordingly, we made a diagnosis of masticator space abscess and decided to follow up by prescribing antibiotics (CDTR-PI). Due to a complaint of feverishness 3 days later, we added the intravenous administration of CTRX and followed up carefully. However, WBC count and CRP level had increased 2 days later, so the patient was admitted to our ward and was administered intravenous CLDM and PIPC. An intraoral incision was performed 2 days after hospitalization and pus was drained. The postoperative course went well, and the patient was discharged on the 14th day. Although slight jaw opening pain and malocclusion persisted at the time of discharge, the symptoms disappeared completely 4 weeks later.

No recurrence of inflammation has been observed to date.

The patient was a 52-year-old female who consulted our hospital complaining of pain of the right temporomandibular joint (TMJ). The first examination revealed pain and crepitus of the right TMJ and a limited mouth-opening of 21 mm. MRI showed that the right TMJ had irreducible anterior disc displacement and mild osteophyte of the mandibular condyle. We diagnosed osteoarthritis of the right TMJ. Initially, instruction on correction of tooth-contacting habit (TCH), medication and splint therapy were continued and the pain of the TMJ disappeared about 3 months later. After about 1 year, severe pain of the right TMJ occurred again just after bite raising of 5 mm at a certain dental clinic. MRI revealed the right TMJ had erosion and bone marrow edema of the mandibular condyle and joint effusion. Medication and splint therapy were restarted, and the occlusal vertical dimension was returned. Afterwards, arthrocentesis was performed and the pain of the TMJ disappeared. After about 2 years and 4 months, MRI revealed that condylar osteophyte and eminence flattening continued.

Bite raising is a treatment with the risk of causing temporomandibular disorder. With bite raising, temporomandibular disorder progresses rapidly and TMJ morphology may change remarkably. We consider it is necessary to give instruction on the correction of parafunction such as TCH for relieving the load on the TMJ when bite raising is performed.