Hydrophilicity, Viscoelastic, and Physicochemical Properties Variations in Dental Bone Grafting Substitutes

Abstract

The indication-oriented Dental Bone Graft Substitutes (DBGS) selection, the correct bone defects classification, and appropriate treatment planning are very crucial for obtaining successful clinical results. However, hydrophilic, viscoelastic, and physicochemical properties' influence on the DBGS regenerative potential has poorly been studied. For that reason, we investigated the dimensional changes and molecular mobility by Dynamic Mechanical Analysis (DMA) of xenograft (cerabone®), synthetic (maxresorb®), and allograft (maxgraft®, Puros®) blocks in a wet and dry state. While no significant differences could be seen in dry state, cerabone® and maxresorb® blocks showed a slight height decrease in wet state, whereas both maxgraft® and Puros® had an almost identical height increase. In addition, cerabone® and maxresorb® blocks remained highly rigid and their damping behaviour was not influenced by the water. On the other hand, both maxgraft® and Puros® had a strong increase in their molecular mobility with different damping behaviour profiles during the wet state. A high-speed microscopical imaging system was used to analyze the hydrophilicity in several naturally derived (cerabone®, Bio-Oss®, NuOss®, SIC® nature graft) and synthetic DBGS granules (maxresorb®, BoneCeramic®, NanoBone®, Ceros®). The highest level of hydrophilicity was detected in cerabone® and maxresorb®, while Bio-Oss® and BoneCeramic® had the lowest level of hydrophilicity among both naturally derived and synthetic DBGS groups. Deviations among the DBGS were also addressed via physicochemical differences recorded by Micro Computed Tomography, Scanning Electron Microscopy, Fourier Transform Infrared Spectroscopy, X-ray powder Diffractometry, and Thermogravimetric Analysis. Such DBGS variations could influence the volume stability at the grafting site, handling as well as the speed of vascularization and bone regeneration. Therefore, this study initiates a new insight into the DBGS differences and their importance for successful clinical results.

Keywords: biomaterials; bone grafting; bone substitutes; hydrophilicity; mechanical analysis.

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1

Schematic description of the method for Dynamic Mechanical Analysis (DMA).

Figure 2

Schematic description of the method for hydrophilicity analysis.

Figure 3

Dynamic Mechanical Analysis (DMA): (a) Dimensional changes; (b) molecular mobility changes.

Figure 4

Hydrophilicity analysis: (a) cerabone® 0.5–1 mm (fast blood uptake driven by capillary forces); (b) Bio-Oss® 0.25–1 mm (blood adjustment over the surface followed by delayed leaking due to heavier drop formation).

Figure 4

Hydrophilicity analysis: (a) cerabone® 0.5–1 mm (fast blood uptake driven by capillary forces); (b) Bio-Oss® 0.25–1 mm (blood adjustment over the surface followed by delayed leaking due to heavier drop formation).

Figure 5

Hydrophilicity analysis: (a) NuOss® 0.25–1 mm; (b) SIC® nature graft 0.3–1 mm (blood adjustment over the surface of both materials followed by leaking).

Figure 6

Hydrophilicity analysis: (a) maxresorb® 0.5–1 mm (fast uptake of blood once in contact with the surface); (b) NanoBone® 0.6 mm (blood adjustment over the surface followed by leaking).

Figure 7

Hydrophilicity analysis: (a) Straumann® BoneCeramic 0.5–1 mm (blood adjustment over the surface without any leaking during the tested period); (b) Ceros® 0.7–1.4 mm (blood adjustment over the surface followed by delayed leaking after the sixth drop due to heavier drop formation).

Figure 7

Hydrophilicity analysis: (a) Straumann® BoneCeramic 0.5–1 mm (blood adjustment over the surface without any leaking during the tested period); (b) Ceros® 0.7–1.4 mm (blood adjustment over the surface followed by delayed leaking after the sixth drop due to heavier drop formation).

Figure 8

µCT analysis: (a) cerabone® and (b) maxgraft® have “labyrinth-like” cancellous bone structure; (c) maxresorb® has “foam-like” structure with highly interconnected regular-circular pores. 1 mm ruler in every figure.

Figure 9

Particle distribution size analysis by Scanning Electron Microscopy SEM: Particles bigger than 1 mm were found in all samples and particles smaller than 0.25 mm were found in Bio-Oss®.

Figure 10

Particle surface analysis by Scanning Electron Microscopy SEM: cerabone® shows rougher wave-like surface roughness when compared to Bio-Oss®; maxresorb® has even rougher foam-like surface structure, and maxgraft® has fiber-like surface structure due to presence of organic material. 20 µm ruler in every figure.

Figure 11

Chemical differences analyzed by FTIR: P-O bonds at 570–605 cm−1 and 970–1100 cm−1 as well as O-H bonds at ~3500 cm−1 and 1650 cm−1 were observed in all samples. cerabone® and maxresorb® showed additional hydroxyapatite O-H band around 3575 cm−1. 1460 cm−1, 1420 cm−1, and 880 cm−1 bands were observed for Bio-Oss® and maxgraft® due to presence of CO32− that were not present in cerabone® and maxresorb®. maxgraft® also had absorption bands at 1550 cm−1 and 1245 cm−1 corresponding to C-H and N-H bonds.

Figure 12

Crystallinity differences analyzed by XRD: Hydroxyapatite peaks were seen in all samples, and only maxresorb® has additional reflexes due presence of β-tricalcium phosphate (Ca3(PO4)2). The narrow peaks and a low baseline indicate the high crystallinity of cerabone® and maxresorb®. Bio-Oss® shows broader peaks due lower crystallinity level. maxgraft® also has broad peaks and a high baseline due low crystallinity and amorphous structure.