The differences between activated (p = 0.044) and total gelatinase B (p = 0.026) levels were significant in the three BL groups. Furthermore, gelatinase B levels were increased in Group 3 compared to Groups 2 and 3. Activation of gelatinase B together with elevated mGI eventually reflects active phases of peri-implantitis and may prove to be diagnostically useful. The gene discussed is MMP9; the disease is Peri-Implantitis.