Ridge Preservation with Freeze-Dried Bone Allograft and a Collagen Membrane Compared to Extraction Alone for Implant Site Development: A Clinical and Histologic Study in Humans

Tooth extraction typically leads to loss of ridge width and height. The primary aim of this 6-month randomized, controlled, blinded, clinical study was to determine whether ridge preservation would prevent post-extraction resorptive changes as assessed by clinical and histologic parameters.Twenty-four patients, 10 males and 14 females, aged 28 to 76 (mean 51.5 +/- 13.6), requiring a non-molar extraction and delayed implant placement were randomly selected to receive either extraction alone (EXT) or ridge preservation (RP) using tetracycline hydrated freeze-dried bone allograft (FDBA) and a collagen membrane. A replaced flap, which did not completely cover the sockets, was used. Following extraction, horizontal and vertical ridge dimensions were determined using a modified digital caliper and an acrylic stent, respectively. Prior to implant placement, a 2.7 x 6.0 mm trephine core was obtained and preserved in formalin for histologic analysis.The width of the RP group decreased from 9.2 +/- 1.2 mm to 8.0 +/- 1.4 mm (P<0.05), while the width of the EXT group decreased from 9.1 +/- 1.0 mm to 6.4 +/- 2.2 mm (P<0.05), a difference of 1.6 mm. Both the EXT and RP groups lost ridge width, although an improved result was obtained in the RP group. Most of the resorption occurred from the buccal; maxillary sites lost more width than mandibular sites. The vertical change for the RP group was a gain of 1.3 +/- 2.0 mm versus a loss of 0.9 +/- 1.6 mm for the EXT group (P<0.05), a height difference of 2.2 mm. Histologic analysis revealed more bone in the RP group: about 65 +/- 10% versus 54 +/- 12% in the EXT group. The RP group included both vital bone (28%) and non-vital (37%) FDBA fragments.Ridge preservation using FDBA and a collagen membrane improved ridge height and width dimensions when compared to extraction alone. These dimensions may be more suitable for implant placement, especially in areas where loss of ridge height would compromise the esthetic result. The quantity of bone observed on histologic analysis was slightly greater in preservation sites, although these sites included both vital and non-vital bone. The most predictable maintenance of ridge width, height, and position was achieved when a ridge preservation procedure was employed.