Compromised oral hygiene, a frequent complication with orthodontic treatment, can lead to enamel demineralization and
decay. Therefore, orthodontists commonly prescribe a daily topical fluoride. The purpose of this investigation was to study the effect of two types of fluoride prophylactic gels on: 1. The mechanical properties of nickel titanium (Ni-Ti) and stainless steel (SS) orthodontic wires. 2. Stress relaxation characteristics of conventional, memory elastomeric chains and NiTi closed coil springs. To fulfill this purpose, the studied sample was divided into three equal groups of ten according to the type of test media; acidulated fluoride agent, neutral fluoride agent and artificial saliva (control). The wires were tested in their received condition and after one hour and half immersion in the test media at 37°C. The loading and unloading elastic modulus and yield strength of the  wires were measured with a 3-point bend test on a universal testing machine. The elastomeric chains and the closed coil springs were subjected to stress relaxation test. Force readings were taken at initial activation and then at time intervals 1hour, 24 hours, 1, 2, 3 and 4weeks. The results concluded that 1. Topical fluoride agents decrease the functional unloading mechanical properties of Ni-Ti and SS orthodontic wires which could contribute to prolonged orthodontic treatment. 2. Ni-Ti coil springs and memory elastomeric chains were not significantly affected. So, they are recommended in association with Topical fluoride agents for delivering steady-continuous force for a period up to four weeks.