Comparison of three-dimensional digital analyses and two-dimensional histomorphometric analyses of the bone-implant interface.

Histological analysis is considered to be the gold standard method of evaluating osseointegration around a bone-implant. However, this method requires invasive specimen preparation and is capable of representing only one plane. By comparison, micro-computed tomography (µCT) is a fast and convenient method that offers three-dimensional information but is hampered by problems related to resolution and artifacts, making it a supplementary method for osseointegration analysis. To verify the reliability of µCT for osseointegration evaluation, this animal model study compared bone-to-implant contact (BIC) ratios obtained by the gold standard histomorphometric method with those obtained by the µCT method, using a rabbit tibia implant model. A sandblasted, large-grit, acid-etched (SLA) implant and a machined surface implant were inserted into each tibia of two rabbits (giving eight implants in total). Bone-implant specimens were analyzed using µCT with a spiral scan technique (SkyScan 1275) and histological sections were prepared thereafter. Three-dimensional (3D) reconstructed µCT data and four two-dimensional (2D) µCT sections, including one section corresponding to the histologic section and three additional sections rotated 45°, 90°, and 135°, were used to calculate the BIC ratio. The Pearson's test was used for correlation analysis at a significance level of 0.05. The histomorphometric BIC and the 2D-µCT BIC showed strong correlation (r = 0.762, P = 0.046), whereas the histomorphometric BIC and 3D-µCT BIC did not (r = -0.375, P = 0.385). However, the mean BIC value of three or four 2D-µCT sections showed a strong correlation with the 3D-µCT BIC (three sections: r = 0.781, P = 0.038; four sections: r = 0.804, P = 0.029). The results of this animal model study indicate that µCT can be used to complement the histomorphometric method in bone-implant interface analyses. With the limitations of this study, 3D-µCT analysis may even have a superior aspect in that it eliminates random variables that arise as a consequence of the selected cutting direction.

Platelet-rich plasma alone is unable to trigger contact osteogenesis on titanium implant surfaces.

PURPOSE: Osseointegration consists of bidirectional bone formation around modified implant surfaces by contact osteogenesis and distance osteogenesis. This study tested whether contact osteogenesis on the surface of a modified titanium (Ti) implant is stimulated by cytokines in the blood. METHODS: In the first two types of experiments, sandblasted, large-grit, acid-etched Ti implants and turned Ti tubes were inserted into rabbit tibiae. To exclude the influence of distance osteogenesis, the tubes were inserted into the tibiae, and implants were placed inside the tubes. In a third type of experiment, the implants and tubes were inserted into the rabbit tibiae, and platelet-rich plasma (PRP) or recombinant human bone morphogenetic protein-2 (rhBMP-2) was applied topically. Four weeks after implantation, undecalcified specimens were prepared for histomorphometry. Bone-to-implant contact (BIC) and bone area per tissue (BA) were measured, and the data were analysed using one-way ANOVA at a significance level of 0.05. RESULTS: When the response of bone to Ti tubes with implants was compared to that without implants (first experiment), little bone formation was found inside the tubes. The mean BIC of implant specimens inside the tubes was 21.41 ± 13.81% in a second experiment that evaluated bone responses to implants with or without Ti tubes. This mean BIC value was significantly lower than that in the implant-only group (without tubes) (47.32 ± 12.09%, P = 0.030). The third experiment showed that rhBMP-2 significantly increased contact osteogenesis on the implant surface, whereas PRP had no effect (mean BIC: 66.53 ± 14.06% vs. 16.34 ± 15.98%, P = 0.004). CONCLUSIONS: Platelet-rich plasma alone is unable to trigger contact osteogenesis on the modified titanium implant surface.