Design and Development of a Novel Bone Graft Carrier to Deliver Particulate Alloplasts for Periodontal Regeneration: An In Vitro study

INTRODUCTION: Periodontal regeneration is defined as the reproduction or reconstruction of lost or injured tissue so that the architecture, form and function of the lost structures are restored. Bone grafting is the most commonly used procedure to rebuild and regenerate lost bone due to periodontal disease. Synthetic alloplasts are most commonly used in recent times but the major drawback of these is that they are in a particulate form which makes transfer and packing into the osseous defect site difficult. AIM OF THE STUDY: To design a bone graft carrier to deliver particulate alloplasts to intraoral defect sites for periodontal regeneration and to modify alloplastic bone grafts by the addition of polymeric additives to transform them into an injectable consistency and analyse its physico-chemical characteristics. MATERIALS AND METHODS: Hydroxyapatite (HA), the base material that was used in this study was modified by the addition of a polymer namely sodium alginate and a cross linking agent calcium chloride, to convert it into an injectable consistency. 2.4 grams of HA was mixed with varying concentrations of sodium alginate (10%, 8%, 6%, 5%) and manually mixed until a homogenous mixture was obtained. Calcium chloride was the cross-linking agent that was added to obtain a moldable form of the HA granules. The crosslinked gel was then vacuum dried for 24 hours to obtain a free flowing powder. This powder can then be converted into an injectable form as and when required by the addition of distilled water. The injectable crosslinked gel can be back filled into syringe-like carrier system for clinical application. In addition, physicochemical characterization of the material was done. RESULTS: Scanning electron microscopy showed that the particles of both the control (hydroxyapatite without sodium alginate) and test group (hydroxyapatite with 10% sodium alginate) appeared as clusters linked in a continuous network. The test group showed more regular appearance of granules with an uneven surface texture which might be due to the coating with sodium alginate. Rheological characterization like injectability was done for hydroxyapatite coated with four varying concentrations of sodium alginate (10%, 8%, 6%, 5%) and it was shown that as the percentage of sodium alginate increased the injectability also increased. Xray diffraction (XRD) analysis showed that there were no significant differences between the test and control groups and both showed characteristic peaks for HA at 2θ = 25.8º (002), 31.7º (211), and 32.9º (300). DISCUSSION: Among the various treatment modailities to manage periodontal diseases, regenerative procedures are the most preferred. Synthetic alloplasts are most commonly used to fill bone cavities due to their availability and biocompatibility. But the granular nature of these grafts make it difficult to use in a clinical setting. In this study we designed a prototype carrier syringe to deliver particulate graft materials. Also we have developed a novel crosslinked hydroxyapatite - sodium alginate gel for which injectability was established through rheological characterization. Physicochemical characterization also showed that the addition of sodium alginate did not alter the hydroxyapatite granules thus being a very cost effective and biocompatible material that can be added to synthetic alloplasts to make them injectable. CONCLUSION: This study has given way to a novel concept of modifying alloplastic bone graft materials into a injectable form. Though in vitro characterization has proved that the material is injectable and that sodium alginate does not modify the base material in a harmful way further in vivo testing is required. Also a cost effective prototype syringe-like carrier system to deliver the graft material to the defect site has also been presented in this study