Survival and Radiographic Evaluation of Root-Analogue Versus Root-Form Zirconia Implants: 18 months Follow-up Study

This comparative cohort study evaluated the survival rate and the marginal bone loss of rootanalogue compared to root-form zirconia dental implants. 28 patients, 35-45 years old, with a free medical history and presenting with a non-restorable mandibular premolar, were selected in this research. Atraumatic tooth extraction and immediate placement of zirconia one-piece implants were performed. The total number of patients were divided according to the type of implants into the zirconia Root-Analogue group (RA, n=14), which was customized to the exact shape of the extracted root. Retentive features were added to the implant surface with the aid of CAD/CAM on Yttria tetragonal zirconia polycrystal blocks (Y-TZP) (Ceramill Zi, Amann Girrbach, Austeria) and prefabricated Root Form group (RF, n=14)(WhiteSky, Bredent, Germany). After 3-5 months of placement, the two groups were then subdivided according to the type of implant supported restorations (n=7) into zirconia crowns (RAZ and RFZ) and PEEK crowns (BioHPP, Bredent, Germany) (RAP and RFP). Clinical survival rates were evaluated in addition to radiographic measuring of marginal bone loss (MBL) in each group at baseline, 3, 6, 12, and 18 months. Early loss of three RA implants before loading resulted in a cumulative survival rate of 79.5%. However, the RF group showed a survival rate of 100% at all follow-up periods of 18 months. The surviving implants showed mean MBL, 1.7mm(1.5-1.8), 1.35mm(1.2-1.5), 1.2mm(1.0-1.2), and 1.0mm(0.9-1.5) for RAZ, RAP, RFZ, and RFP, respectively at 18 months of follow up. Clinical examination during the follow-up periods did not reveal any parameter influencing MBL. RA implants should not be recommended as a substitute for prefabricated RF implants due to the increased incidence of premature failure, however using PEEK crowns as supra structure restorations may influence the outcomes related with marginal bone loss.