On growth factors and titanium implant integration in bone

Abstract

PurposeThe purpose of the present thesis was to investigate the bone tissue response around titanium implants with one growth factor stimulating hormone and a few different growth factor substances.Material and methodsIn four studies (study I to IV) a rabbit model were used and the growth factors i.e. growth hormone (hGH), enamel matrix derivative (EMD), fibroblast growth factor-4s (FGF-4s) or bone morphogenetic protein-7 (BMP-7) was applied around or inside the titanium implants.In study I, 16 Russian rabbits were used and in study II, III and IV a total number of 22 New Zealand White rabbits were used. The follow-up time was 8 weeks in study I, 6 weeks in study II and III and 4 weeks in study IV. In two studies (study V and VI) a Labrador dog model with partially inserted implants was used. A total number of 10 dogs were used in these two studies. The first dog study evaluated the model with the partially inserted implants and the second dog study evaluated a bone morphogenetic protein S 300 cocktail (BMP S300). In all studies threaded commercially pure titanium implants were used. Evaluation of the osseointegration of the implants was performed by resonance frequency analysis (4 studies), removal torque test (3 studies), dual energy X-ray analysis (one study), histomorphometric analysis on undecalcified ground sections (all studies) and image access analysis on microradiographs (one study).ResultsThe results indicate that systemically delivered human growth hormone may enhance the initial implant integration and that local delivery of FGF-4s may stimulate bone formation around titanium implants. However, it seemed that EMD, BMP-7 and BMP S300 failed to stimulate bone formation around titanium implants in the used models.ConclusionWithin the limits of the studies of the present thesis growth factors locally applied in conjunction with press fit placed titanium implants does not seem to contribute to substantially improved implant integration. Small positive effects were demonstrated after systemically delivered hGH and FGF-4s pre-treated bone. However, the present author has not at all been convinced that external supply by growth factors are effective in experimental press fit models as those used in the present study. It is quite possible that inherent growth factor are sufficient to stimulate bone formation around press fit titanium implants and an external addition of growth factors may not result in substantially reinforced bone volumes. This assumption implies that growth factors may be of little use in the ordinary clinical situation.