Osteoconductivity of Bovine Xenograft Granules of Different Sizes in Sinus Lift: A Histomorphometric Study in Rabbits

Abstract

Background: Due to the lack of data on bone-to-graft contact (BGC) over time in the various regions within the subantral space of the augmented sinus floor, the present study aimed to evaluate the osteoconductivity of deproteinized bovine bone mineral (DBBM) with granules of different sizes applied in maxillary sinus floor elevation.

Methods: A maxillary sinus augmentation was performed bilaterally in 18 rabbits using DBBM with particle dimensions of either 0.125-1.0 mm or 1-2 mm. The antrostomy was covered using a collagen barrier. The animals were euthanized in groups of six after 2, 4, and 8 weeks of healing. MicroCT and histological analyses were performed.

Results: After 2 weeks of healing, BGC was 10.9% and 11.9% for the small and large granule sites, respectively. After 8 weeks of healing, the BGC increased to 65% and 62% at the small and large granule sites, respectively. The highest values were located close to the bony walls and the bony window. New bone content developed between 2 and 8 weeks from 7.0% to 27.6% and from 6.1% to 27.6% at the small and large granule sites, respectively.

Conclusions: Similar outcomes in osteoconductivity and bone formation were found at both small and large DBBM granule sites.

Keywords: animal study; bone healing; collagen membrane; histology; morphometry; osteoconductivity; sinus floor elevation; xenograft.

Figure 1

View of the clinical procedures in the experimental region. (A) A 3.5–4 mm antrostomy was prepared on both sides, laterally to the nasal-incisal suture, and anteriorly to the nasal-frontal suture. (B) Deproteinized bovine bone mineral granules either 0.250–1.0 mm or 1.0–2.0 mm were randomly allocated and grafted within the elevated space in similar quantity. (C) The antrostomies were subsequently covered with collagen barriers.

Figure 2

The various regions analyzed in the augmented sinus (BW = bone walls; M = middle; SM = sub-mucosa; CtW = close-to-window) and the antrostomy region (AL = lateral; AM = medial margin; AC = center of the antrostomy).

Figure 3

MicroCT 3D images representing the augmented sinus at the 0.125–1 mm and 1–2 mm size granules after 2 (A), 4 (B), and 8 (C) weeks of healing.

Figure 4

Ground sections representing the augmented sinus at the 0.125–1 mm and 1–2 mm size granules after 2 (A), 4 (B), and 8 (C) weeks of healing. Images originally taken with objective ×10. Stevenel’s blue and alizarin red stain.

Figure 5

Photomicrographs of ground sections representing the healing after 2 weeks at small granules sites. (A) Newly formed bone was found close to the bone walls and lining on the surface of the DBBM. (B) A dense tissue rich in fibroblast-like cell was seen surrounding the DBBM particles. A loose tissue rich in vessels was interposed among particles. Some multicellular cells were visible (e.g., *). Original magnification ×200. Stevenel’s blue and alizarin red stain.

Figure 6

Photomicrographs of ground sections representing the healing after 4 weeks at large granules sites. (A) Bone walls region. Higher content of new bone was found compared with the previous period analyzed. Some multicellular cells were still visible (e.g., *). (B) New bone reached over time the most central regions, growing from the lateral (L) and mesial (M) bone walls of the sinus. The granule in the center presents a higher peripheral chromaticity compared with that seen in the previous period of healing. Moreover, some of the dense tissue surrounding the granule appeared to have a higher content of active cells, especially in zones where the new bone was formed between the graft surface and the cellular cluster (yellow arrows). Note a front of new bone formation and osteoid tissue (red arrows). Original magnification ×200. Stevenel’s blue and alizarin red stain.

Figure 7

Photomicrographs of ground sections representing the healing after 8 weeks at small granule sites. (A) Marrow spaces were seen at this stage of healing (yellow asterisks). (B) A particle with augmented chromaticity, not yet reached by newly formed bone. Original magnification ×200. Stevenel’s blue and alizarin red stain.

Figure 8

Graphs representing the percentages of BGC and dense tissue in contact with the graft surface in the various regions and periods evaluated. Stars indicate the intersection point between new bone and dense tissue.