This report presents three dimensional (3D) orthodontic force systems of three commercial closing T-loop archwires. An orthodontic force tester (OFT) was developed to measure the force systems simultaneously, simulating the clinical environment for space closure. The archwires were installed and activated following a standard clinical procedure. The resulting force system was measured using the OFT. The force systems of the T-loops on the teeth were 3D. Activation in one-direction resulted in force and moment components in other directions (side-effects). The six force and moment components as well as the moment-to-force ratios in the clinically defined coordinate system were quantified. This method can be used to quantify the 3D orthodontic force system. The commercial archwires do not provide force systems for pure translation. Quantification of the force system is critical for the selection and design of optimal orthodontic appliances.