METHODSRESULTSCIS II Paper Summary and Analysis: Biocompatible Bone Fillers: PaperSummary and AnalysisFelicia ShayComputer Integrated SurgeryMentors: Drs. Frassica and WenzAdvisor: Dr. TaylorINTRODUCTIONThe filling of the osteolysis site is the second component of the deliverable for the semester project. The material must be biocompatible since the material is implanted at the site. The response of the body on the material is fundamental to the success of the implantation. Consequently, these considerations must be weighed before placing the material in vivo. The constraints in the filling aspect of the project deals with:- Injectibility,- Setting time,- Compression once place in vivo,- Tension, and - Response of the body on the material.Taking these requirements into consideration, selection of the ideal material should be made.Papers were selected for review and presentation for the class. The main hypothesises and themes of these papers evaluated and tested the constraints on a variety of material (polymethylmethacrylate PMMA, PMMA composites, bioglass, PMMA/ Ca/P composites, Ca/P composites, and hydroxyapatite) in consideration for implantation at the osteolytic site.METHODSCompression:Cyclic wear testing (Lloyd's Mechanical Testing machine) was employed which was universally used for all the papers. This method is often employed for material science testing. A cylinder of the material is molded to simulate the material in vivo. The wear is measured by the change in thickness or volume displacement after the cylinders have been worn down. Compression is then measured in MPa.Tension:Tension testing was only employed in the Y. Okada articles that compared a bioactive glass to PMMA bone segment in rabbit tibia. A defect was created within the center of the tibia and then filled the defect with material and set. At 12 and 25 weeks, therabbits were sacrificed. The tibias were removed and Kirschner wires were inserted into the two ends of the tibia. The tension test pulls the two ends of the tibia apart with Kirschner wires and the force was measured.Injectability:Injectability measures the amount of material that arrives at the site in relation to the amount of material that was initially mixed. This is dependent upon the material itself, its viscosity, the amount of material that is trapped within the syringe. In the Dreissen article, injectability is the percentage by weight that the material after injection divided by the weight of the material before injection. This makes the powder liquid ratio irrelevant to the injectability. Only the TCP/CaCO3 , HA, the DCP/CaCO3, and the HA/DCP composite are tested.Setting Time:The setting time is the time it takes from the beginning of mixing to the point where an indentation cannot be made in the material. This criterion is important due the location, shape, and size of the osteolytic site.X-Ray Diffraction and Scanning Electron Microscope:The importance of these two testing mechanisms is the ability to see on a microscopic level what is happening both on the surface of the material and the interface between the material and the body. We can see the morphology as well as the pathology of the material and determine the best in vivo response to the material. For example, soft tissue can be viewed at the interface site, which indicates that the bone to material interface is no very good and immunological and fibrous encapsulation of the material could be occurring. Immunological response is not ideal for long-term biological implanted material. Fibrous encapsulation results in the rejection and weakening of the material. Considerations and Constraints in the Testing Mechanisms:All of the testing mechanisms mentioned above achieve the basic requirements needed to be tested. The testing mechanisms do achieve the sufficient testing of the given hypothesises and the given criterion/constraints. In the end though, in vivo testing in one (Okada) of the five articles sited. Although simulated body fluid (SBF) is an excellent measure of the response of the body, simulation is not quite as accurate or spontaneous as an in vivo testing of the material. In the end, lack of in vivo testing could have greatly affected the results.Another consideration is that although all the testing mechanisms and basic procedures were the same, the actual parameters such as the gage of the syringe were different which often occurs when reviewing several different articles and compiling the information. This lack of consistency could make the results inconclusive in the end. Without the same parameters, there could be some difficulties in accurately compiling the data and drawing conclusions about the most ideal material.RESULTSDreissans:Material selection was HA/CaCO3, HA, HA/DCP, and HA/DCP/CaCO3. Injectability testing, setting time, and compression testing was used on the material as wellas the Ca/P ratio similarity to bone. The setting time was related to the body temperature. The closer the warmer to body temperature 37C the shorter the setting time in relation to at 20C.Injectability % Setting Time 37CCompression Mpa after 1 dayCa/P immersion1 dayAP/CaCO3 83 6.5 33 1.672AP 81 9.5 8 1.616AP/DCP/CaCO3 94 2.75 48 1.481AP/DCP 92 9.0 15 1.344Important to note is that the in vivo Ca/P ratio is 1.67Taking these test results into consideration, the ideal material would be the AP/CaCO3 based on its high compression value, similarity to in vivo Ca/P ratio, and its extended setting time. Although the injectability percentage is not as high, as long as the material fills the area completely and covers all the surfaces of the site, injectability percentage is less of a consideration.Asaoka:Material section in this article was in vivo testing of a TCP composite. Compression, setting time and pH values were all taken into consideration. Compressability MpaSetting time pHTCP composite 65 (3 days) 70 (4 days) (maximum)6 minutes ~7.0This TCP composite has the greatest compressability compared to the Dreissans article.Shibuya:Material selection in this article was comparing PMMA and Ca/P composite that is hydroxyapatite based. The Ca/P based composite material, like PMMA is a resin which is more moldable. PMMA cement clinically has been determined to loosen over time due to fibrous encapsulation and soft tissue ingrowth and degradation. The actual activation of the material is exothermic and damages surrounding tissue. Although the