What type of kinematic chain is involved in the action brushing teeth?

The kinematic chain involved in the action of brushing teeth is the type IV kinematic chain, also known as a closed kinetic chain. Type IV kinematic chains are characterized by the fact that the distal end of the chain (in this case, the toothbrush) is fixed in place, while the proximal end (the elbow) is free to move. This type of chain is commonly found in everyday activities, such as grasping a tool, and in various types of sports, such as throwing and swinging.