Study Extraction location Preservation method Difference
(initial vs follow-up) 		Control group Period observation
Iasella et al. [21] 1, 2, 3, 4, 5, 6 Group A - EXT Alveolar ridge width:
Group A:
17.28 (SD 1.2)/15.68 (SD 1.13)
vs
Group B:
16.91 (SD 1.34)/15.44 (SD 1.33) 		12 patients,
12 sockets 		6 months
Group B: RP with a mineralized freeze-dried bone allograft, 500 to 1,000 μm particle size, and a collagen membrane
Meloni et al. [45] Not specified Socket grafting with deproteinized bovine bone and sealed with epithelial connective tissue graft or porcine collagen matrix Horizontal bone volume
(with collagen vs control):
Level A
(1 mm below the most coronal aspect of the bone crest):
8.24/7.7 vs 8.39/7.72.
Level B
(3 mm below the most coronal aspect of the bone crest)
8.18/7.35 vs 8.53/7.62.
Level C
(5 mm below the most coronal aspect of the bone crest)
8.21/7.99 vs 8.27/7.96 		15 patients,
15 sockets 		17 months
Vertical bone volume
(with collagen vs control):
Level D
17.28/16.58 vs 16.91/15.44
Barone et al. [48] Not specified Group A - EXT Group RP:
10.6 (SD 1)/8.1 (SD 1.4)
vs
Group EXT:
10.8 (SD 0.8)/6.3 (SD 0.8) 		20 patients,
20 sockets 		7 to 9 months
Group B: preservation procedure with corticocancellous porcine bone
(MP3, Osteobiol®) and collagen membrane (Evolution, Osteobiol®)

EXT = extraction alone; RP = ridge preservation.