Tough Porous Bone Plugs for Oral and Maxillofacial Defects

Objectives: Bone loss in the oral and maxillofacial region occurs due to tooth loss, trauma, and disease, presents challenges for surgeons and dentists. The ideal biomaterials that can provide comparable performance to autografts are yet to be achieved. Calcium Phosphate (CaP) porous scaffolds such as hydroxyapatite are extremely brittle in nature, tend to be stable, and do not allow manipulation in surgical theatre. To overcome these limitations, a resorbable calcium metaphosphate (CMP), evaluated in vivo, able to form new bone in a rabbit model within eight weeks with minimal scaffold remaining[1], was used as a filler to create hydrogel composites in water soluble poly(vinyl alcohol) (PVA) as matrix using simple and non-toxic crosslinking method.
Methods: PVA solutions were homogenously mixed with CMP powder with ratio of PVA:CMP=60:40 with the addition of particulate gelatin as the porogen to increase macroporosity. The composite was then subjected to freeze-drying and the resulting scaffold was taken through a series of aqueous washings to leach the porogen. The scaffolds were subsequently characterized using x-ray diffraction, infrared and Raman spectroscopy, water uptake, differential scanning calorimetry, mechanical testing, scanning electron microscopy, µCT, and cytotoxicity evaluation.
Results: An elastomeric composite was obtained that exhibited rigid sponge-like properties yet allowed it to be shaped to enable surgical manipulation. The plug shaped composites showed excellent mechanical strength and controlled swelling and architecture. An intimate interaction of the CMP particles-PVA matrix was obtained with a uniform distribution of the CMP particles in PVA matrix. The FTIR spectra showed evidence of a weak interaction between CMP-PVA, and PVA-gelatin. Cytotoxicity investigations demonstrated that the scaffolds were non-toxic to human osteoblast cells.
Conclusions: A new design of tough and tailorable hydrogel composite made of relatively affordable materials with simple and non-toxic methods has been developed. In addition, the presence of the hydrogel matrix would also facilitate incorporation of orthobiologics and drugs. These scaffolds are suitable as bone plugs for use in oral and maxillofacial bone defects.

Reference
[1] Buranawat B et al., J Periodontology, 85: 298-307, 2014.