Bone reactions at implants with different surface topography and static load. Experimental studies in rabbits and dogs

Abstract

The aims of the present experiments were to study bone reactions at implants (i) with different surface topography, and (ii) subjected to static lateral loads of different magnitude, duration and with ligature-induced peri-implantitis. In study I, 120 implants were inserted in the tibia of 12 rabbits. Removal torque tests (RMT) were performed after 4, 6, 9 and 12 weeks. Ground sections of the "bone bed" were prepared for histological analysis. In studies II-V a dog model was used. Three months after extraction of mandibular premolars, implants with different surface topography were inserted in the bone. Crowns connected in pairs with orthodontic expansion screws, were fitted 12 weeks later to the implants. A static lateral load was induced by expansion screws. In study II, 4 different degrees of expansion were examined, while in study III the bone reactions to load at implants with turned and titanium-plasma-sprayed (TPS) surfaces were evaluated. In study IV the influence of duration of the lateral static load was analyzed and in study V peri-implantitis with or without static load, was investigated.It was found that an increased surface roughness resulted in an increased implant anchorage assessed by RMT (Study I). Laterally loaded implants exhibited a higher peri-implant bone density and a larger fraction of mineralized bone-to-implant contact than implants not exposed to lateral load (Study II). The values describing (i) marginal bone level, (ii) amount of bone-to-implant contact at the bone/implant interface and (iii) peri-implant bone density following 24 weeks of static lateral load were larger at implant sites with a TPS surface than at sites with a turned surface (Study III). It was also demonstrated that sites subjected to 10 or 46 weeks of lateral load had similar (i) distribution of bone labels, (ii) peri-implant bone density and (iii) amount of bone-to-implant contact (Study IV). The peri-implant bone density and the amount of mineralized bone-to-implant contact fraction were larger in the interface zone than in zones 1 to 2 mm lateral of the implant surface (Study II-V). The lateral static load failed to enhance bone loss at implants with experimental peri-implantitis.