Effectiveness of dental implants indicated for early-loading protocols on peri- implant bone healing: An animal study

Abstract Objective Recent advancements in dental implantology focus on surface treatments that enable early loading protocols, potentially enhancing implant stability and accelerating osseointegration. This study aimed to evaluate the effects of hydrophilic surfaces on implant stability, osseointegration, and peri-implant bone healing. Method The four different types of implants, including the Straumann SLActive® and Thomenn Inicell® designed for early loading protocol, and the Straumann SLA® and Thomenn SPI® normal controls were randomly inserted into the proximal metaphysis of the tibiae of 20 New Zealand rabbits. Two implants were placed in each tibia, yielding 80 total implants. Subsequently, half of the rabbits underwent a healing period of two weeks, while the remaining half underwent a healing period of eight weeks. The implant stability quotient (ISQ) values for all the implants were measured at 0, 2, and 8 weeks to evaluate stability. In each healing period, half of the implants were subjected to removal torque testing to assess the mechanical strength of osseointegration, while the other implants underwent micro-CT, histological, and histomorphometrical assessment to evaluate the osseointegration and peri-implant bone quality and quantity, including the relative gray value (RGV), bone-to-implant contact (BIC), peri-implant bone volume/tissue volume (BV/TV). Statistical analysis was conducted using multiple Mann-Whitney U tests. Results A tendency towards higher ISQ values in the implants indicated for the early loading protocol was observed, whereas there was no significant difference in the ISQ values overall. For Straumann implants, SLActive® demonstrated a marginally higher removal torque value than the SLA® group at 2 weeks (p = 0.068). Micro-CT analysis further showed that the RGV of dental implants in the early loading group (Inicell®) was significantly higher than that in the normal implant group (SPI®) at 2 weeks (p < 0.05). Moreover, histomorphometrical analysis showed a significantly higher value of BV/TV ROI 1 in the early loading group (Inicell®) than the normal control group (SPI®) at 2 weeks (p < 0.05). Conclusion These results, comparing SLActive® with SLA® of Straumann, and Inicell® with SPI® of Thomenn in rabbit tibia, suggest that dental implants indicated for early loading protocol may exhibit superior osseointegration and periosteogenesis, particularly during the initial healing stage.