Development of Biphasic Nano-Calcium Sulfate/Hydroxyapatite Biomaterial as TGF-β1/VEGF Carrier for Vital Pulp Therapy-Material Property, Biocompatibility and Animal Study

Autor: Ching-Ching Wong, 黃菁菁
Rok vydání: 2014
Druh dokumentu: 學位論文 ; thesis
Popis: 102
To treat the reversible pulpal injury, vital pulp therapy aims to preserve pulp vitality as well as to induce dentin-pulp repair/regeneration by direct applying a bioactive material. However, after years of research and development of the capping agents, there is still a shortage of the ideal capping material for vital pulp therapy. Current pulp capping materials present several limitations, such as poor handling properties, prolonged setting time, insufficient mechanical properties, or difficulty to induce dentin-pulp complex regeneration, which in turn influences the prognosis of vital pulp therapy. Hence, the innovation of vital pulp therapy is important to overcome the limitations of current materials. The purpose of this study is to develop a biphasic biomaterial with inorganic materials, nano-calcium sulfate (nCS) and hydroxyapatite (HAp) as a bioactive pulp capping agent which is able to carry dual growth factors (TGF-β1/VEGF) for the induction of dentin-pulp complex regeneration. This study carried out in four parts-Part I: By using cryo–vacuum method, calcium sulfate dihydrate (CSD) was modified to nano-calcium sulfate hemihydrate. Hydroxyapatite was synthesized via chemical co-precipitation. We characterized crystalline phase via X-ray diffraction, and observed the microstructure by scanning electron microscope. The physical properties such as the setting time, compressive strength, in vitro degradation rate and the releasing profile of growth factors were determined while the ratio of nCS/HAp/CS was optimized. Part II: The cell-material interaction study, WST-1 and LDH assay was performed to evaluate the biocompatibility and cell cytotoxicity of nCS/HAp/CS/TGF-β1/VEGF cement. Part III: Evaluation of the cell mineralization ability of human dental pulp cell in response to the biomaterials so as to assess their roles in the pulp capping material in term of the induction of dentin-pulp complex regeneration. Part IV: An animal model of rat was established. In vivo evaluation was performed by non-destructive micro-CT determination and histological analysis. The results revealed that the initial setting time of the nCS/HAp/CS biphasic cement was 15 minutes, which exhibits substantial improvement compared with the commercial product. The compressive strength of the biphasic cement after immersion in phosphate buffered saline solution in 1 day was 7.0 MPa, and decreased after 1 week. Sustained release of TGF-β1/VEGF was achieved up to 60~70% through the biomaterial within 2 weeks. The excellent biocompatibility of the biphasic cement was also confirmed by WST-1 and LDH test, which indicates no significant difference between control group (DMEM) and experimental group (nCS/HAp/CS/TGF-β1/VEGF). Pulp cells treated with nCS/HAp/CS carrying 6 ng/mL TGF-β1 and 0.5 ng/mL VEGF showed increased level of ALP activity and formation of calcified nodules in vitro. In the animal study, the non-destructive determination with micro-CT evaluation showed hard tissue formation during 4-week measurements. Histological analysis demonstrated a prominent formation of reparative dentin bridge with nCS/HAp/CS/TGF-β1/VEGF cement after 4 weeks. Based on the present findings, in view of the advantages of the nCS/HAp/CS/TGF-β1/VEGF cement as the bioactive dressing material for vital pulp therapy, such novel compound is as competitive as the commercial products in minimally invasive treatment of dental pulp therapy and has promising prospects. We concluded that the developed nCS/HAp/CS cement could act as a potent carrier for sustained release of growth factors, and the nCS/HAp/CS/TGF-β1/VEGF cement is of great potential to promote dentin-pulp complex regeneration.
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