It has recently been reported that controlled chemical oxidation of titanium (Ti) with sulfuric acid (H(2)SO(4))/hydrogen peroxide (H(2)O(2)) significantly influences the early stages of in vitro osteogenesis. The aim of this study was to evaluate whether this chemical treatment can also influence in vivo bone formation. Ti implants (Mk III) were etched with H(2)SO(4)/H(2)O(2) for 4 h at room temperature. Mandibular premolars were extracted in eight dogs and, after 3 months, three treated and three untreated implants were placed in each animal. At 3 and 8 weeks postimplantation, the animals were sacrificed, and the implants with surrounding bone were harvested, fixed with formaldehyde, and processed for embedding in LR White. Sections of bone with the implants were prepared, stained with Stevenel's blue and Alizarin red, and analyzed histomorphometrically for percentage of bone-to-implant contact (BIC), percentage of mineralized bone area between threads (BABT), and percentage of mineralized bone area within the mirror area (BAMA). Data were analyzed statistically using two-way analysis of variance. Treated implants exhibited significantly more (P<0.05) BIC than control, untreated ones both at 3 (68.1% vs. 27.9%) and 8 weeks (73.5% vs. 14.7%) postimplantation. However, there was no difference in the BABT and BAMA. Histological analysis confirmed that, in most cases, new bone in contact with the implant formed in a direction away from it. These data indicate that a controlled chemical oxidation of Ti implants significantly enhances contact osteogenesis and suggest that this treatment may be beneficial for early loading of implants.