Effect of rhBMP-2 on Bone Properties in Guided Bone Regeneration

Mechanical properties of newly formed bone tissue in guided bone regeneration (GBR) next to a dental implant are important in sustaining high local stress at the marginal bone region. The objective of this study was to examine the effect of human bone morphogenic protein-2 (rhBMP-2) on mechanical properties of bone in GBR during post-implantation healing. 

Method: 

Following IACUC approval, mandibular premolars and first molars of 6 dogs were extracted bilaterally. After 3 months of healing, dehiscence defects (4×4 mm) were created at the marginal bone next to implant. Eighteen titanium implants were assigned to 3 treatment groups including no treatment (control), demineralized bone matrix (DBM) gel only, and DBM gel with rhBMP-2 groups. The animals were sacrificed at 4 and 8 weeks of post-implantation healing and new bone tissue formed in the dehiscence area was dissected with the implant. The dissected specimen surface was polished for nanoindentation. Using the load/displacement curves for a cycle of indentation, hardness (H), viscosity (η), elastic modulus (E), were obtained at peak load, holding, and unloading processes, respectively. Viscoelastic tangent delta (tan δ) was also assessed using an averaged phase angle (δ) between oscillatory force and displacement signals during loading. A total of 271 indentations were successfully performed. Analysis of variance was performed with significance to be p<0.05.

Result: 

None of the nanoindentation parameters of BMP group were significantly different from those of other groups at week 4 (p>0.066). However, E, H, and η of BMP group were significantly higher and tan δ was significantly lower than other groups at week 8 (p<0.003).

Conclusion: 

BMP had an effect on determining mechanical properties of bone tissue in GBR during the maturation process of post-implantation healing. The current results indicated that the BMP treatments likely improve elastic and fracture stability of the dental implant system.