Socket Preservation Using Xenograft Does Not Impair Implant Primary Stability in Sheep: Clinical, Histological, and Histomorphometric Study
Implant primary stability, which depends mainly on the amount and quality of bone, is important for implant survival. Socket preservation aims to reduce bone volumetric changes after tooth extraction. This animal study aims to examine whether preserving a ridge by using xenograft impairs the primary stability of the implant. Eighteen artificial bone defects were prepared in 4 sheep (5- and 8-mm length). Defects were randomly grafted with xenografts: Bio-Oss (BO), Bio-Active bone (BB), or left for natural healing (control). After 8 weeks, bone biopsy was harvested and dental implants installed. During installation, peak insertion torque (IT) was measured by hand ratchet, and primary stability by the Osstell method. Histomorphometric analysis showed a higher percentage of new bone formation in the naturally healed defects compared to sites with xenograft (control: 68.66 ± 4.5%, BB: 48.75 ± 4.34%, BO: 50.33 ± 4.0%). Connective tissue portion was higher in the BO and BB groups compared to control (44.25 ± 2.98%, 41 ± 6%, and 31.33 ± 4.5%, P < .05, respectively). Residual grafting material was similar in BO and BB (7 ± 2.44%, 8.66 ± 2.1%, respectively). Mean IT and implant stability quotient (ISQ) values were not statistically different among the groups. A positive correlation was found between IT and ISQ (r = 0.65, P = 0). In conclusion, previously grafted defects with xenograft did not influence primary stability and implant insertion torque in delayed implant placement. These results may be attributed to a relatively high bone fill of the defect (∼50%) 2 months after grafting.

Figure 1. First surgical intervention. (a) After incision and reflection of the flaps, alveolar ridge before defect preparation. (b) Creating the defect using a drill diameter of Ø5 mm and 8 mm in depth (c) 4 wall defects, where distal is grafted and mesial left for spontaneous healing. Figure 2. Second surgical intervention after 8 weeks. (a) Bone core biopsies were taken using trephine (Ø1.7 mm). (b) After implant placement. (c) Stability measurement using the Osstell system.

Correlation between insertion torque (N/cm) and implant stability quotient values. Pearson correlation coefficient test.

Histologic figure of each group (hematoxylin & eosin staining). (a) Bio-Active bone. (b) Bio-Oss. (c) Control Group. Bone substitutes particles were surrounded by newly formed bone.
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