Bone augmentation using a synthetic hydroxyapatite/silica oxide-based and a xenogenic hydroxyapatite-based bone substitute materials with and without recombinant human bone morphogenetic protein-2.

Abstract

To test whether or not bone regeneration using deproteinized bovine bone mineral (DBBM) is comparable to hydroxyapatite/silica oxide (HA/SiO) and to test the effect of recombinant human bone morphogenetic protein-2 (rhBMP-2) as an adjunct to DBBM for localized bone regeneration. In each of the 10 rabbits, 4 titanium cylinders were placed on the external cortical plates of their calvaria. Four treatment modalities were randomly allocated: (i) empty, (ii) HA/SiO, (iii) DBBM, and (iv) DBBM plus rhBMP-2 (DBBM/BMP). The animals were sacrificed at week 8. Descriptive histology and histomorphometric assessment using a superimposed test grid of points and cycloids were performed. The mean number of points of the test grid coinciding with bone within the cylinder reached 124 ± 35 bone points for empty controls, 92 ± 40 bone points for DBBM, 98 ± 44 bone points for synthetic HA/SiO, and 146 ± 34 bone points DBBM/BMP. The P-value for DBBM with and without BMP reached a borderline statistical significance of 0.051. However, the area of bone regeneration within the cylinders peaked for DBBM/BMP and was statistically significantly higher compared with empty cylinders (P < 0.05). The bone-to-bone substitute contact ranged between 32.9% ± 21.7 for DBBM, 39.6 ± 18.4% for HA/SiO, and 57.8% ± 10.2 for DBBM/BMP. The differences between DBBM/BMP and controls (DBBM, HA/SiO) were statistically significant (P < 0.05). DBBM and HA/SiO rendered comparable amounts of bone regeneration. The addition of rhBMP-2 to DBBM resulted in more favorable outcomes with respect to the area of bone regeneration and to bone-to-implant contact, thereby indicating the potential of this growth factor to enhance bone regeneration within this animal model.