Morphometric evaluation of the early stages of healing at cortical and marrow compartments at titanium implants: an experimental study in the dog

To study the early sequential stages of tissue composition in the cortical and marrow compartments of the alveolar bone crest at implants with a moderately rough surface.Three month after tooth extraction in 12 Labrador dogs, full-thickness flaps were elevated in the edentulous region of the right side of the mandible and one implant was installed. The flaps were sutured to allow a fully submerged healing. The timing of the installations in the left side of the mandible and of sacrifices were scheduled in such a way to obtained biopsies representing the healing after 5, 10, 20, and 30 days. Ground sections (n = 6 per each healing period) were prepared, and the percentages of osteoid/new bone, old bone, new soft tissues (provisional matrix and primitive marrow), mature bone marrow, vessels, and other tissues (bone debris/particles and clot) were evaluated laterally to the implant surface up to a distance of about 0.4 mm from it.Osteoid/new bone was found after 5 days at percentages of 10.8 ± 4.3% at the marrow and 0.6 ± 0.6% at the cortical compartments. After 30 days, these percentages increased up to 56.4 ± 4.0% and 23.3 ± 6.1%, respectively. Old parent bone was resorbed between 5 and 30 days from 28.7 ± 10.9% to 14.9 ± 3.4% at the marrow (~48% of resorption) and from 81.2 ± 9.4% to 67.6 ± 5.6% at the cortical (~17% of resorption) compartments. All differences were statistically significant.Bone apposition to an implant surface followed a significantly different pattern in the compact and the marrow compartments around the implants. While in the compact compartments, bone apposition had to develop through the BMUs following resorption, it developed in very dense layers through an early apposition in the marrow compartments.