Analysis of Tooth-Brushing Motion with High Precision Motion Capture

Third Report : Analysis and Comparison of Arm Movement between Pen Grip and Palm Grip

Abstract

Both the pen grip and palm grip are recommended techniques for holding a toothbrush during brushing. We evaluated the motion of the toothbrush as well as the shoulder, elbow, and wrist during brushing performed by dental hygienists using the pen grip. Each hygienist had a distinct individual rhythm and all arm joints moved in a synchronous manner during brushing. Our findings indicate that the pen grip may be difficult for children with immature motor function, because stable and cooperative movements are necessary with its use during tooth brushing. Conversely, because the toothbrush can be more easily held with the palm grip, that technique is sometimes recommended for patients with muscle weakness in their hands or fingers caused by aging and disease.The dental hygienists brushed the buccal and palatal sides of the right and left upper molars using both pen and palm grips, and the frequency of toothbrush motion as well as joint angles of the shoulder, elbow, and wrist were calculated. The motions of the toothbrush and arm during brushing were also evaluated and compared between the two grips.Study conclusions :1)Each dental hygienist had a distinct individual rhythm for reciprocal motion of the toothbrush during brushing with both grips.2)The arm joints showed mostly synchronous motion during brushing on the right side with the pen grip and on the left side with the palm grip when brushing buccal and palatal teeth.3)The motion stability of each arm joint was reflected in coordinated movements of all joints in subjects using the pen grip. However, coordinated joint movement was not necessary to ensure joint stability during motion when using the palm grip.