Expression of MMP-2, 9 and 13 in newly formed bone after sinus augmentation using inorganic bovine bone in human

The aim of the present study was to analyse the expression of MMP-2, MMP-9 and MMP-13 in newly formed bone following maxillary sinus augmentation using inorganic bovine bone substitute, because these MMPs play a major role in bone remodeling and bone resorption.

Deproteinized bovine bone (Bio-Oss(®)) was used to fill cavities after elevating the sinus mucosa. Twenty patients with edentulous posterior maxilla were treated with 20 sinus-augmentation procedures using a two-stage technique. Forty-nine Straumann(®) endosseous implants were used to complete the implant-prosthetic rehabilitation. One cylinder-shaped bone biopsy from each patient was taken from the augmented maxillary region using trephine burs at the second stage of surgery, 8 months after grafting. A biopsy was also taken as a control from the upper molar region from six different patients who did not undergo the sinus procedure. All biopsies were subjected to biochemical analysis and staining for TRAP.

No implant losses or failures occurred. The large number of TRAP-positive multinucleated osteoclasts in resorption lacunae indicated that the resorption was very active in all grafts, in contrast with the control group. Zymography and western blot analysis demonstrated a significantly increased expression of MMP-2, MMP-9 and MMP-13 in the newly formed bone compared with controls (p < 0.05).

The quantity of osteoclastic cells and the increased expression of proteolytic enzymes suggest that 8 months after grafting, inorganic bovine bone is slowly resorbing and is the site of important remodeling of the newly formed bone by means of resorption and synthesis.