Early tissue healing around unloaded orthodontic mini-screws. A study in the Beagle dog. Part II. Hard tissues.

• DOI: 10.22533/at.ed.4502322127

• Palavras-chave: -

• Keywords: Osseointegration; orthodontics; mini-implants; hard tissues healing; animal study.

• Abstract: Understanding tissue healing around orthodontic mini-screws can provide useful information for their clinical use. Despite some similarities with prosthodontics implants some differences exist in terms of materials, surface texture and load. The purpose of this study was to investigate the early phase of hard tissue healing around unloaded orthodontic mini-implants. Twenty self- tapping mini-screws were inserted in five Beagle dogs at the day 0, 2, 7, 15 and 30. The bony specimens containing the screws were dissected, fixed, embedded in acrylic resin before they were cut. The samples were stained with Stevenel's blue and Goldner and observed under light microscopy. Soon after insertion, primary stability was good for all mini-implants. In some implant areas, direct contact with the parent lamellar bone was observed. In other areas a gap due to the pilot bur drill was present and was initially filled by a coagulum. At day two the blood clot was transformed in granulation tissue and an amorphous protein matrix, containing osteoblasts, was noticed on the parent bone. Some lymphocytes and macrophages could be observed among the red blood cells and the small chips deriving from the bone preparation. At day 7 was evident the osteoid deposition over the pristine lamellar bone. At day 15 woven bone could be seen within the osteoid matrix bridging from the parent bone towards the titanium surface. At day 30, beyond the woven bone, is visible parallel fiber bone deposited directly on the implant surface, indicating osseointegration of the screws.