Sequential morphometric evaluation at UnicCa^® and SLActive^® implant surfaces. An experimental study in the dog

To study sequential osseointegration around implants with nano-technologically modified surfaces at different periods of healing.

After 3 months, two different implant systems with different nano-technologically modified surfaces were randomly installed in the edentulous molar regions of the mandible of 12 dogs. One surface was acid-etched surface, and subsequently modified with calcium ions (UnicCa^® ), while the other was a hydrophilic sandblasted with large grit and acid-etched (SLActive^® ) surface. The implants were fully submerged, and biopsies were obtained representing the healing after 1, 2, 4 and 8 weeks (n = 6 per period). A morphometric evaluation of densities of new soft tissues (provisional matrix and immature bone marrow), new and old bone, mature bone marrow, vessels and other tissues (bone debris/particles and clot) was performed in the spongiosa compartment of the sites of implantation.

After 1 week of healing, the soft tissues, mainly composed of provisional matrix, were present at 41.5 ± 23.9% and 30.1 ± 20.0% at the UnicCa^® and SLActive surfaces, respectively. These percentages were >40% at both surfaces after 2 weeks of healing, presenting greater amount of immature bone marrow. Subsequently, these percentages decreased up to disappear after 8 weeks of healing. New bone increased progressively between 1 and 8 weeks of healing from 8.2 ± 3.0% to 77.1 ± 6.4% and from 6.8 ± 2.8% to 67.9 ± 6.8% at the UnicCa^® and SLActive^® , respectively. Old bone decreased progressively over time.

The patterns of healing at highly hydrophilic surfaces occurred through the early formation of a provisional matrix followed by the formation of new bone and marrow at various stages of maturation. The healing was similar to those described in different animal models, anatomical sites and surgical procedures.