Bone tissue microstructure and function. Part II: Immediate loading and biomaterials | [Microstruttura e funzione del tessuto osseo. Parte II: carico immediato e biomateriali]

Objectives: Aim of the paper was to make a revision on the bone microstructure adaptive mechanisms and function around dental implants and biomaterials. Materials and methods: The bone architecture was compared on the basis of ten years of histological evaluations made in both human and animal models. The following were treated in detail: immediate loading effect on bone collagen fiber orientation; osseointegration of dental implants in presence of biomaterials simultaneously placed with implants; bone microstructure differences between humans and animal models usually used in dental research. Results: Immediate loading procedure improves the peri-implant bone matrix organization. Likewise, the prevalent transverse collagen fibers orientation increases bone strength to compressive loads. Moreover, under an adequate mechanical stimulus the peri-implant bone became compact. A prevalent de novo bone formation around biomaterial's particles and a peri-implant "focal" osseintegration could be seen in the case of simultaneous placement of biomaterial and implants. Compared to humans, the bone microstructure and physiology of the most used animal models for in vivo studies appear to be significantly different. Conclusions: In implants with an adequate primary stability, immediate loading procedure improves the quality of osseointegration. Progressive loading procedure should be used after the second stage surgery in implants simultaneously inserted with a biomaterial. In in vivo animal research, both objectives of the studies and ethical considerations should be considered to choose the animal model