Biological Evaluation Of Native Carbon Fiber-reinforced Post Materials

Objective More and more residual roots and crowns are preserved following the enhancement of people's self awareness of teeth and the development of root canal treatment, so the restoration of pulpless teeth defected seriously has been the important task of prosthetic clinicians. In the recent ten years, metal free restoration-prefabricated carbon fiber post-core system is widely used in Europe and America and recognized gradually as a valid alternative to conventional metallic posts for reconstruction of residual roots and crowns . The carbon fiber posts have provided promising clinical results due to similar elastic modulus to that of dentin, matching mechanical properties to tooth structure, virtually no predisposition to root fracture, high biocompatibility and so on. But this method is not popular in our country. The present study aims to primarily screen four types of carbon fiber-reiforced polyimide resin post materials (PI1-4) produced by Institute of chemistry, Chinese Academy of Sciences beginning with bilolgical properties. The qualified samples can be expected to enter the next stage of tests for the earlier clinical application. Materials and methods The first stage: In vitro preliminary screening tests Materials: Four types of native carbon fiber-reinforced composite PI1-4, C-POST(produced by Bisco Company) as homogeneous control material of cytotoxicity test. Methods: 1. cytotoxicity test: L-929 mouse fibroblasts were cultured in the medium of extraction of materials. Cell viability and proliferation were tested by dimethylthiazol diphenyltetrazolium (MTT) assay through values of OD at 2,4 and 7 days respectively after innoculation. The cell relative growth rate(RGR) was calculated and the cytotoxicity was graded by generally accepted standard. 2. hemolysis test: Hemolysis percentage measurement was used to assay the hemolytic properties of four types of materials through direct contact with rabbit blood. From above tests, one or two material with high biocompatibility was permitted to go into the next tests. The second stage: In vivo Animal tests Materials: The carbon fiber post which had been screened through MTT assay and hemolysis test. C-POST as control. Methods: Subcutaneous implant test and bone implant test were involved in the study. Materials were implanted into subdermal tissues and tibias of two hindlegs respectively in rabbits, and animals were sacrificed after 2, 4and 8 weeks. Macroscopic inspection and histological assessment of the implantation site were required.Results The first stage 1.The cytotoxicity of PI1-4 was grade 1, up to standard. 2.The hemolysis rates of PI1-4 were less than 5%, up to standard. 3. Through comprehensive analysis and assessment, PI4 was recognized as the screening to the next tests with the best nature relatively. The second stage 1. Subcutaneous implant test and bone implant test both indicated that PI4 had not caused marked pathological inflammatory responses, which was similar to the C-POST. Conclusion In vitro and in vivo Studies had shown: native carbon fiber–reiforced composite PI4 had good biocompatibility and the further steps could be taken to study deeply and comprehensively for the earilier clinical application.