Individual bone pattern and peri-implant bone loss in patients treated by implants with platform switching concept: clinical and histological multicenter RCT

This RCT aims to evaluate bone responses to different diameter implants restored with platform switching, testing whether individual local bone quality could be related to postimplant resorption. 80 implants (Global®, Sweden & Martina, Italy), were divided according to platform diameter in 4 groups: 3.8 (ControlGroup), 4.3 (TestGroup1), 4.8 (TestGroup2) and 5.5mm (TestGroup3), 20 implants each group. They were randomly placed in the posterior maxilla of 42 patients. Implant osteotomy was performed using a trephine and obtained bone specimens were harvested for each patient. Bone structure and quality was analyzed by histology and immunohistochemical detection of anabolic (collagen type I, OPG, runx2, osteocalcin, osteopontin, BSP), catabolic (RANKL, TRAP, ED1, cathepsin K, TNF-α) markers and growth factors (BMP-2, VEGF, PDGF). Immunostaining was semi-quantitatively.evaluated Two months later, all implants were connected to a 3.8mm diameter abutment and definitive rehabilitation was performed. Radiographic bone loss were measured by two independent trained observers when implant was placed (baseline), definitive prosthesis inserted and every six months thereafter using an image analysis software. Mean follow-up was 20 months. All 80 implants were clinically osseointegrated. Radiographic analysis showed a bone resorption of 0.896mm (SD=0.456mm) for testGroup1, 0.770mm (SD=0.505mm) for testGroup2, 0.388mm (SD=0.315mm) for testGroup3. Each test group mean values were statistically significant (p≤ 0.005) compared to control group mean values (1.548mm, SD=0.684mm). Furthermore, the individual local bone structure and quality could be in all likelihood correlated to peri-implant bone resorption. This study suggests that bone loss could be related to the implant /abutment mismatching and individual bone pattern.