Condylar movements of temporomandibular disorder patients with intermittent lock: a pilot study.

The purpose of this study was to clarify which direction of the condylar path is advantageous for releasing TMJ intermittent lock. The subjects were ten patients with temporomandibular disorders (TMD) and intermittent lock caused by anterior displacement of disks without obvious medial or lateral displacement. The patients could not open their mouths fully in habitual opening but could open fully in an intentional winding opening with reduction of the anteriorly displaced disks (winding opening). The two kinds of movement at the kinematic condylar point were measured in each subject and compared. The length of the condylar path in winding opening was significantly larger than that in habitual opening. The affected side condyle of winding opening traced medio-inferior paths in the early part of the condylar translation in comparison with habitual opening. From the viewpoint of the condylar path, the medio-inferior direction of condylar translation is thought to be advantageous for releasing intermittent lock.

The advantageous direction of jaw movement for releasing TMJ intermittent lock.

The purpose of this study was to clarify which direction of jaw movement is advantageous for releasing TMJ intermittent lock. The subjects included ten patients with TMJ intermittent lock who could not open their mouths fully in habitual opening paths (habitual opening), but could open fully in intentionally winding opening paths (winding opening). The following movements were analyzed: habitual opening, winding opening, lateral border opening to the contralateral side (contralateral opening), lateral border opening to the affected side and anterior border opening. The incisal points in winding opening tended to trace antero-lateral paths that were shifted toward the side opposite the affected joints in comparison with habitual opening. In addition to winding opening, the success rate in releasing locking of contralateral opening was significantly greater than that of habitual opening. The findings demonstrated that contralateral movements directed toward the nonaffected side are advantageous for releasing the intermittent lock. The patients will have a better chance of releasing the intermittent lock by themselves, when opening path shifted to the nonaffected side is recommended as the first choice.

The influence of tissue blood flow volume on energy metabolism in masseter muscles.

This study investigated the energy metabolism of masseter muscles by 31P-Magnetic Resonance Spectroscopy (MRS) during increased blood flow induced by hot pack application to clarify the influence of changes in blood flow on muscle fatigue. Twelve healthy subjects with no history of muscle pain in the masticatory system participated in this study. The 31P-MRS measurements were performed before and after hot pack application and the ratio of phosphocreatine (PCr) acting as the energy source to reproduce ATP to beta-ATP, the PCr/beta-ATP ratio, was analyzed. Results showed that PCr/beta-ATP ratios increased significantly by an average of 22.4% after the hot pack application. The results suggest that changes in blood flow volume influence the energy metabolism in masseter muscles and that blood flow increases due to the hot pack cause higher energy levels in masseter muscles and offer an advantageous condition for preventing and relieving muscle fatigue.

A new training device for rehabilitation of lateral mandibular movements: a pilot study.

Laterotrusive training is often used together with mouth-opening training in order to achieve adequate translation of the affected condyle in treatment of TMJ closed lock. This training is usually performed by voluntary laterotrusive movement (VLM) or by laterotrusive movement using only the fingers (FLM). However, satisfactory results are often not obtained by using these methods. To resolve this problem, we devised a new laterotrusive training device (LT device). In this paper, we describe the method of the training of laterotrusive movement using the LT device (LLM) and present a comparison of the results obtained by using LLM with those obtained by using VLM and FLM. The subjects were ten patients with TMJ closed lock. The following results were obtained: 1. the range of LLM was significantly larger than those of VLM and FLM; and 2. all of the patients reported that LLM could be performed more easily than VLM and FLM. In conclusion, the LT device is thought to be useful for laterotrusive training in TMJ closed lock.

Electromyographic activity of the jaw-closing muscles during jaw opening in patients with masseter muscle contracture.

Contracture of the jaw-closing muscles is one of the causes of limitation of jaw opening. This study examined whether there is any difference between the EMG activities of jaw-closing muscles during jaw opening in healthy people and in patients with masseter muscle contracture (MMC), who do not have a history of trauma or infection. The patient group consisted of eleven females, 18 to 62 years old with no history of trauma or infections, with limited mouth opening due to MMC. The control group included eleven healthy females, 23 to 50 years old. The EMG activity was recorded bilaterally in the central portion of masseter muscles (Mm), the anterior portion of temporal muscles (Tm), and the anterior belly of digastric muscles (Dm). Nine out of the patient group showed obvious EMG activity in Mm during jaw opening which was different from typical EMG patterns during jaw opening of up to 40 mm in the control group. Among the nine patients, eight showed antagonistic contraction in Tm as well as Mm. The mean integral value of Mm and Tm during jaw opening in the patient group was significantly higher than in the control group (P<0.01). These results suggest that EMG activity during jaw opening in MMC patients with no history of trauma or infections is different from that in healthy people.