Evaluation and Comparison of Arm-Joint and Toothbrush Motion Between Pen Grip and Palm Grip During Tooth Brushing

Objective: We aimed to examine the hypothesis that the two different hand-grip techniques (pen grip and palm grip) affect tooth-brushing motion.Methods: Eight dental hygienists participated in this study. Their tooth-brushing motion for 15 seconds was captured using a motion-capture system. The buccal and palatal sides of the right and left upper molars using both the pen and palm grips were brushed, and the frequency of joint angles of the shoulder, elbow, and wrist was calculated during tooth-brushing.Results: Individuals showed smaller intra-individual variations in the peak frequency of the toothbrush and joint angles during the brushing of all sides with both the pen and palm grips. For some arm joints, using the palm grip showed higher intra-individual variations than inter-individual, but the intra-individual variations among all joints using the pen grip were lower in all brushing areas.Conclusion: A distinct individual tooth-brushing rhythm in the reciprocatory motion was established by each dental hygienist using both the pen and palm grips. The coordinated movements of all joints of subjects using pen grips reflected the stability of the tooth-brushing motion of each arm joint. However, when using the palm grip, it is not necessary to ensure joint stability during tooth-brushing motion. Examination by three-dimensional toothbrushing motion analysis revealed that the reciprocatory performance during tooth-brushing was easier with the palm grip than with the pen grip.