Indiana University-Purdue University Indianapolis (IUPUI) / This investigation compared the spring characteristics of three space closing assemblies; the classic "Bull" loop and two new spring designs currently being used in the Department of Orthodontics at Indiana University. Using interbracket distance and the degree of gable preactivation as variables, a complete laboratory analysis was carried out on each spring design. A total of two hundred springs were tested. A statistical investigation was conducted to determine if the spring designs had significantly different load-deflection rates, moment to force ratios, and range of activation. The range of activation for all three spring designs was large enough to be of some minor importance in determining the difference in efficiency of each design. However, when the load-deflection rates and moment to force ratios of the "Bull" loop and the two new spring designs were compared, the new spring designs invariably proved to be superior. From this laboratory study, it was concluded that the two new spring designs have the potential of providing a more efficient method of orthodontic space closure.