by Toru Ogawa, Sheng Zheng, Masayo Nemoto, Xie Ziqi, Hu Longshuang, Kenta Shobara, Hiroki Hihara, Hiroyasu Kanetaka
Recently, clinically used implants have been undergone surface treatment, enabling early loading.. This study aimed to evaluate the efficiency of dental implants indicated for early loading protocols by assessing the implant stability quotient, rigidity of osseointegration, and morphology of peri-implant bone healing.
The four different types of implants, including the Straumann SLActive® and Thomenn Inicell® indicated 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 implants were subjected to removal torque testing to assess the mechanical strength of osseointegration, while the other implants underwent microCT, histological, and histomorphometrical assessment to evaluate the osseointegration and peri-implant bone quality and quantity, which includes the relative gray value (RGV) (water = 0, and implant = 100), bone-to-implant contact (BIC), peri-implant bone volume/tissue volume (BV/TV, ROI 1 and ROI 2 (bone volume fraction; ROI 1: implant surface 0–100 ?m; ROI 2:100–500 ?m)). Statistical analysis was conducted using the Multiple Mann-Whitney U test.
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 showed a marginally higher removal torque value than normal loading (SLA) 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 groups (Inicell) than the normal loading groups (SPI) at 2 weeks (p<0.05).
These results, which compared between SLActive and SLA of Straumann, and Inicell and 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.
