Bone-Forming Capabilities of a Newly Developed NanoHA Composite Alloplast Infused with Collagen: A Pilot Study in the Sheep Mandible

Abstract

Lateral or vertical bone augmentation has always been a challenge, since the site is exposed to constant pressure from the soft tissue, and blood supply only exists from the donor site. Although, for such clinical cases, onlay grafting with autogenous bone is commonly selected, the invasiveness of the secondary surgical site and the relatively fast resorption rate have been reported as a drawback, which motivated the investigation of alternative approaches. This study evaluated the bone-forming capability of a novel nanoHA alloplast infused with collagen graft material made from biodegradable polylactic acid/polyglycolic acid versus a control graft material with the same synthesized alloplast without the nanoHA component and collagen infiltration. The status of newly formed bone and the resorption of the graft material were evaluated at 6 weeks in vivo histologically and three dimensionally by means of 3D microcomputed tomography. The histologic observation showed that newly formed bone ingrowth and internal resorption of the block were observed for the experimental blocks, whereas for the control blocks less bone ingrowth occurred along with lower resorption rate of the block material. The three-dimensional observation indicated that the experimental block maintained the external geometry, but at the same time successfully altered the graft material into bone. It is suggested that the combination of numerous factors contributed to the bone ingrowth and the novel development could be an alternative bone grafting choice.

Figure 1

While the macrogeometric structure of both bone blocks were similar. At low magnification, scanning electron micrographs of the difference in HA particle size was easily depicted between (a) control and (b) experimental blocks. Field-emission scanning electron micrographs of the experimental group depicted the (c) nanoHA particles within the biopolymeric matrix (arrowheads) and that (d) collagen infusion took place at the nanometer scale (arrows).

Figure 2

Clinical aspect of extraoral access utilized for the placement of control and experimental blocks. Blood wetting was observed throughout the volume of the experimental block material, whereas blood wetting was lower for the control block.

Figure 3

Three-dimensional reconstruction of the mandibular segment containing both experimental and control blocks. (a) Lateral view of the onlays depicted bone ongrowth on the lateral aspects of both blocks. (b) The cross-sectional reconstruction showed the perforations performed in the mandibular lateral aspect cortical (arrows). Bone ingrowth was observed at the region in immediate contact with the mandibular bone for both blocks; bone ingrowth throughout the volume of the block was only observed for the experimental group, which also presented lower amounts of synthetic material compared to the control group.

Figure 4

Histologic sections for the (a) control and (b) experimental block materials placed on the lateral aspect of the mandible. The histologic sections revealed the perforations performed in the mandibular lateral aspect cortical (arrows). Higher magnification of the (c) control and (d) experimental blocks showed that bone ingrowth occurred throughout the volume of the experimental block material, and little ingrowth occurred for the control block material. Smaller amounts of synthetic material were also observed for the experimental block relative to the control block material.