The effect of collagenated space filling materials in sinus bone augmentation: a study in rabbits

The inclusion of biomaterial particles used for alveolar bone regeneration in a carrier or in binding agents such as collagen gel or fibers is of interest as a means to help with surgical handling. However, the possible influence of collagen on bone tissue response to biomaterials is poorly studied. The objective of the present study was to investigate, in a sub-sinus bone augmentation model in rabbits, the effect of collagen at different stages of the osteogenesis process. Histologic, histomorphometric and volumetric analyses were performed.

Rabbits underwent a double sinus lift procedure using bovine hydroxyapatite (BHA), collagenated bovine hydroxyapatite (BHAColl), and prehydrated and collagenated porcine hydroxyapatite (PHAColl). Animals were sacrificed at 1 week, 5 weeks or 6 months. Samples were subjected to X-ray micro-tomography and histology. Qualitative analysis was performed on the non-decalcified sections and quantitative histomorphometric analyses were conducted using scanning electron microscopy (SEM). Volume variations of bone augmentations were calculated at different time points.

The three biomaterials allowed an optimal bone formation and were able to equally withstand sinusal reexpansion. A comparable percentage of new bone, as well as 3D volume stability, was found between the groups at each time point. However, the PHAColl resorption rate was significantly higher than the rates in other groups (P = 0.0003), with only 3.6% of the particles remaining at 6 months. At 1 week, both collagenated groups displayed the presence of inflammatory cells although BHA did not show any sign of inflammation. At 5 weeks and 6 months, the inflammatory process had disappeared completely in the BHAColl groups, whereas some inflammatory-like cells could still be observed around the remaining particles of PHAColl.

Within the limitations of this study in rabbits, the findings showed the presence of inflammatory-like cells at the early stage of bone regeneration when collagenated xenogenic biomaterials were used compared to xenogenic granules alone. Nevertheless, similar bone formation occurred and comparable 3D volumes were found at 6 months in the different groups.