Immediate implantation in fresh extraction sockets. A controlled clinical and histological study in man

Background: Early implantation may preserve the alveolar anatomy, and the p lacement of a fixture in a fresh extraction socket helps to maintain the bo ny crest. Although a number of clinical studies exist, no histological repo rts show the outcome of implantation in fresh extraction sockets without th e use of membranes in humans compared to implants placed in mature bone. Methods: Forty-eight healthy patients, receiving at least 4 fixtures in eac h of 2 symmetrical quadrants, underwent placement of 1 experimental fixture placed in a fresh extraction socket (TI) and 1 contralateral fixture in ma ture bone (Cl). TI were placed after atraumatical tooth extraction, with a surgical site at the apex of the socket and a tight contact between the fix ture and the socket's walls, but without the use of filling materials or me mbranes. The flap was coronally repositioned to obtain primary wound closur e. Immediately after surgical intervention, a standardized periapical radio graph was taken. Second-stage surgery was done after 6 months. Six months a fter the second surgery, a second standardized periapical radiograph was ta ken and clinical parameters (bleeding and plaque index) recorded. Marginal bone loss (MBL) from the time of implant placement to the time of fixture r emoval was calculated by comparing periapical radiographs. TI and Cl were t hen removed by a hollow drill to obtain histological specimens. Non-deminer alized sections were stained by acid fuchsin and toluidine blue, and by von Kossa to evaluate the degree of bone mineralization. The percentage of dir ect implant-bone contact (DBC) was calculated by a computerized microscopic digitizer. Results: No significant differences in the clinical and radiographic parame ters were observed between the 2 experimental categories. There was no stat istically significant difference between TI and Cl for DBC either in the ma xilla or in the mandible. No connective or fibrous tissues were present aro und TI or Cl. Bone resorption was not present in any of the histological se ctions. Conclusions: The present study shows that when a screw-type dental implant is placed without the use of barrier membranes or other regenerative materi als into a fresh extraction socket with a bone-to-implant gap of 2 mm or le ss, the clinical outcome and degree of osteointegration does not differ fro m implants placed in healed, mature bone.