 Nitric oxide NO metabolism is associated with the clinical inflammatory state of peri-implant tissues and also affected by the mechanic stimulus. Therefore, The NO content of PISF reflects two different measures and can serve as an indicator of peri-implant soft tissue inflammation andor bone response to force application and loading Arginase may reduce NO production by depleting the common substrate. Thus, increased salivary arginase activities detected in periodontitis patients may cause decreased NO synthesis and lead to a decrease in the antibacterial property of saliva. 