MMP9 and periodontitis: TIMP-1, in particular, is barely expressed in periodontitis in comparison with healthy subjects; on the other hand, its overproduction contributes to inhibiting the inflammation and tissue damage, due to the hyperactivation of MMP-9 [16], in the wound area after healing abutment implantation, suggesting that it exerts a pivotal role in controlling peri-implant disease progression [14,17].