Histomorphometric evaluation of implant design as a key factor in peri-implant bone response: a preliminary study in...

Primary implant stability as the establishment of a direct bone-to-implant contact (BIC) plays a major role in long-term successful implant osseointegration. Numerous factors influencing this initial stability have been studied. This preliminary in vivo study on a dog lower jaw aimed to investigate the hypothesis that primary implant stability in low density bone may be influenced by implant design.

The authors compared two different implant designs with regard to their immediate quantitative relation to host bone (BIC% and gap area, GA%). The screw-shaped implants, manufactured by Or-Vit (Castelmaggiore-Bologna, Italy), exhibited similar microroughness surface and two different thread pitches: ''narrow-pitch'' implants (NP) and ''wide-pitch'' implants (WP) with a 0.5 mm and 1.5 mm thread pitch respectively. Implants were placed in dog jaw after complete osseous healing of the extractive sockets, according to a delayed implantation procedure. Five hours after surgery the animal was sacrificed. Radiographic, histological, morphometric and ultrastructural analysis were performed.

An inverse relation existed among the two parameters BIC and GA: GA, as a region with high osteogenetic potentiality, appeared wider in WP implants; BIC, as the expression of primary mechanical stability, was higher in NP implants.

Based on this results, we could assume that NP implants might be the clinical choice in case of immediate loading.This single case study might be considered a starting point for further long term in vivo investigations aiming to establish the implant design that best favours osseointegration at different bone quality sites.