Figures 12–14. Figure 12. Control (machined) implant harvested from human after 2 months. No bone formation on the implant surface was detected. Goldner trichrome stain ×30. Figure 13. Test (acid-etched) implant. It was possible to observe newly formed bone directly on the implant surface and especially within the concavities. Goldner trichrome stain ×30. Figure 14. Test (acid-etched) implants. Axial section showing new bone formation within the concavities. Osteoid matrix and newly formed small vessels were present. Goldner trichrome stain ×20.