Atsuo Takanishi Laboratory in the School of Science and Engineering at the Asahi University School of Dentistry at Waseda University unveiled a robot for giving maxillofacial massages, "WAO-1," Oct. 9, 2007.
The device, which duplicates maxillofacial massages given by doctors, is intended for relieving the symptoms of disorders such as xerostomia, jaw arthritis and swallowing disorder. Treatments that apply "just the right amount of pressure" without excessive force have been realized by using existing technologies developed for robots.
It is estimated that more than 10 million people, including potential patients, are suffering from the disorders mentioned above, and half of them need to be treated. These disorders are likely to become chronic and require continued treatments and rehabilitation.
Massage is an effective treatment method, according to them. In the maxillofacial massage, mastication muscles, parotid glands, parotid ducts and mylohyoid muscles are stimulated by a practitioner by pressing or rubbing lightly. This treatment relieves the symptoms by promoting the flow of saliva and relaxing the muscles.
However, the practice is limited to doctors, dentists and physical therapists and the number of medical institutions offering this treatment is also limited. Therefore, many of the patients had to carry out massage at home.
The massage robot was developed because of this background. WAO-1 consists of two robotic arms, a base on which the arms are installed and a headrest. The massage is facilitated by plungers at the end of the robot arms.
The arms, which move in 6 directions (using 2 prismatic joints, 4 rotational joints), activate the plungers. Depending on the symptom, there are roller plungers, rotary-ball plungers, hemisphere plungers and omnidirectional rotation plungers.
WAO-1 is equipped with algorithm that automatically forms a massage track based on the data on the location and conditions of maxillofacial tissues and the maxillofacial transformation model acquired from the images of CT and MRI. If the portion to be massaged and the strength to be applied are selected, a massage track is formed automatically by the algorithm.
Currently, it is based on average human data, but there are plans to improve it based on the individual data of each patient in the future. For adjustment of each joint, general DC motors are used. It incorporates a DC servo driver (manufactured by Tokushu Denso Co., Ltd., headquartered in Tokyo) that was developed for two-way robots and a motor manufactured by Maxon Motor of Switzerland.
A "Virtual Compliance Control" is mounted on the robot to replicate the maxillofacial shape of each patient. A 6-axis force sensor (manufactured by Nitta Corporation) that measures the force applied from the maxillofacial area is installed between the robot arm and the plunger. The data is set as a constant of spring to implement virtual spring and damper forces.
This technology was adopted by a maxillofacial treatment robot that was developed jointly by Waseda University and Yamanashi University more than 10 years ago. By adopting this technology, massaging without unnatural force is made possible, even if there are changes in the position or the shape of a patient's face.
As safety measures, four systems are installed: (1) Software, (2) Electrical circuit, (3) Mechanical part and (4) Stop switch. (1) is for controlling speed and position. (2) is for blowing a fuse at current surge and controlling the current, equipped with a limit sensor. (3) is a torque limiter that releases the arms when the force exceeding 2 kg is applied. (4) is a switch held by an operator or a patient.
The experiment of massaging parotid glands of healthy subjects by WAO-1 for two minutes revealed that the average of saliva production increased by 0.63 g after massaging. It was also confirmed that the temperature of the skin increased and stayed high for some time after application of massage on the masseteric muscle. Because of these results, Asahi University assumed that the massage is effective for treatment.
Asahi Roentgen Industries Co., Ltd. produced two robots responding to the university's request. They are currently preparing to submit the application to the Ethics Committee, targeting the start of clinical testing in November 2007.
I tried the maxillofacial massage robot WAO-1 (1 minute and 42 seconds).
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