Our study is also in concordance with the results of a removal torque study by Simon et al. [63] in immediately loaded “transitional endosseous implants” in humans. The percentage BIC for MDIs was similar to standard implants.

The surface topography also affects the BIC, Wennerberg et al. [32] measured and compared removal torque values on screw-shaped titanium implants with three surface types. The results showed that screws sandblasted with 25-μm particles of titanium and 75-μm particles of aluminum oxide exhibited a higher removal torque and interfacial bone contact than the machined titanium implants with smoother surface texture.

The surface of 3M^™ESPE^™ MDI is sandblasted with aluminum oxide and cleaned and passivized with an oxidizing acid (Technical Data Sheet, 3M ESPE) [35]. The surface of Ankylos^® is sandblasted and acid etched [64]. Various authors have reported that surface roughness induces a variety of events in the course of osteoblast differentiation, spreading and proliferation, production of alkaline phosphatase, collagen, proteoglycans, and osteocalcin, and synthesis of cytokines and growth factors [65–67]. Therefore, leading to bone deposition on the surface of these implants, Yan et al. [68] demonstrated that simple surface treatments can turn the titanium surface into a bone-bonding one. With the results of our in vitro study, Marulanda et al. [69] on discs of both types of implants demonstrated that surface chemistry of 3M^™ESPE^™ MDI is conducive to growth of osteoblasts leading to bone apposition.

One of the shortcomings of our study may be the use of rabbit tibia as a model. The tibia of the rabbit is essentially hollow except the upper and lower cortical plates. This may justify lack of bone apposition on the whole implant in both experimental as well as comparator implants. However, it provides a reliable information for human application as the human maxillary bone is also of a softer bone quality [36, 51].