Immediate functional loading of single-tooth TiO2 grit-blasted implant restoration.: A controlled prospective study in a porcine model.: Part II:: Histology and histomorphometry

Background: Evidently, there is a fast-moving shift from delayed to immediate implant loading. The hypothesis to be tested was that bone reactions adjacent to single TiO(2)-microthreaded implants exposed to immediate masticatory loading for 10 weeks after placement would modulate osseointegration. Materials and Methods: Cylindrical- and tapered-designed implants (Astra Tech AB, Molndal, Sweden) replaced first and third mandibular premolars respectively in 12 pigs. The animals were allocated into two groups based on soft and hard diet feeding. Each animal received, at random positions, four different masticatory loading conditions: implant with either (1) a cover screw only, (2) a healing abutment, (3) an implant with a crown without occlusal contact, or (4) an implant with a crown in contact with the antagonistic teeth. Results: Histomorphometry showed that there were no statistically significant differences in bone-implant contact (BIC), bone mass inside/outside of the threads and soft tissue ingrowth ratio for all the implants at 10 weeks after placement irrespective of masticatory loading condition. Bone loss showed a trend of progressive increase for implants with a healing abutment toward implants with occlusal contact. Conclusions: The results of this study rejected the hypothesis and could be explained by the fact that grit-blasted acid-etched implants were already placed in dense bone.