No abstract

To examine the stiffness of the masseter muscle using sonographic elastography and to investigate its relationship with the most comfortable massage pressure in the healthy volunteers. In 16 healthy volunteers (10 men and 6 women), the Masseter Stiffness Index (MSI) was measured using EUB-7000 real-time tissue elastography. They underwent massages at three kinds of pressures using the Oral Rehabilitation Robot (WAO-1). A subjective evaluation regarding the comfort of each massage was recorded on the visual analogue scale. Elastography was also performed in two patients with temporomandibular joint dysfunction with the myofascial pain. The mean MSI of the right and left muscles in the healthy volunteers were 0.85 +/- 0.44 and 0.74 +/- 0.35 respectively. There was no significant difference between the right and left MSI in the healthy volunteers. The MSI was related to massage pressure at which the healthy men felt most comfortable. The two temporomandibular disorder patients had a large laterality in the MSI. The MSI was related to the most comfortable massage pressure in the healthy men. The MSI can be one index for determining the massage pressure.

The location and configuration of mandibular canal variations are important in surgical procedures involving the mandible, such as extraction of an impacted third molar, dental implant treatment, and sagittal split ramus osteotomy. We report 3 Japanese patients with bifid mandibular canals using panoramic radiograph and multi-slice helical computed tomography (CT) images. In 2 of the 5 sides, the bifid mandibular canal was suggested on panoramic radiograph. The bifid mandibular canal had a short and narrow upper canal toward the distal area of the second molar in 4 sides, and a short and narrow lower canal toward the distal area of second molar in 1 side, as revealed on reconstructed CT images. Since the location and configuration of mandibular canal variations are important in surgical procedures involving the mandible, they should be carefully observed using reconstructed CT images.