主催: The Japanese Society for Dental Materials and Devices
Introduction: Calcium phosphate cements (CPC) are used as in surgery or dentistry for bone filling materials. In this study, brushite cement was selected because they are resorbable in physiological conditions. Although brushite cement which was one of CPC is viewed as a promising bone substitute material, their setting time and mechanical resistance is too fast and weak to allow their application. It has been demonstrated that mechanical properties of CPC can be modulated through variation in powder composition, liquid phase, liquid-to-powder (L/P) ratio, ageing condition, and many organic or polymeric additives. More recently, a series of studies showed that the incorporation of water-soluble fiber into CPC substantially increased strength and fracture resistance. Therefore, the aim of this study was investigated the effect of addition of dextrin dispersion on the physical and mechanical properties of brushite cement as a function of L/P ratios. Materials and Methods: Brushite cement was formulated with an equimolar powder mixture of b-tricalcium phosphate (b-TCP) and monocalcium phosphate monohydrate (MCPM) and liquid phase with 0.5M citric acid (CA). Brushite-dextrin composite cements were prepared with 40wt% dextrin dispersion in 0.5M CA aqueous solution. The composite cements were prepared by as a function of three different L/P ratios (0.4, 0.45, and 0.5). The initial and final setting times of cements were determined using the Gilmore needle technique (1/4 lb and 1 lb). Samples for compression testing were prepared by placing manipulated cement slurry into a PTFE mold of diameter 6mm and height 12 mm. Once set, dry compressive strength of samples was measured after the set at room temperature in the air for 24h. On the other hand, wet compressive strength samples were measured after the storage at 37 C and 100% relative humidity in water bath for a period of 24 h. Compressive strength was tested by UTM. Results and Discussion: The setting time of brushite cement without dextrin was about 10min at 0.3 of L/P ratio. The setting time of brushite-dextrin composite cement was increased from 7 to 12min when three different L/P ratios (0.4, 0.45, and 0.5). The L/P ratio of 0.45 was chosen for comparison of mechanical properties in this study. Dry and wet compressive strengths of brushite-dextrin composite cements (13 MPa and 4 MPa) were higher than those of brushite cement without dextrin (7 MPa and 1 MPa). Also, the work-of-fracture of composite cement (208 J and 20 J) was more significantly improved than that of brushite cement without dextrin(106 J and 6 J). Conclusions: Although L/P ratio was increased, the mechanical strength of brushite-dextrin composite cement was more improved than brushite cement without dextrin in both dry and wet condition. This study demonstrated that brushite-dextrin composite cement had acceptable mechanical strengths for clinical applications under an appropriate setting time.
