Original Article Proc IMechE Part H: J Engineering in Medicine 1–8 Ó IMechE 2018 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/0954411918796048 journals.sagepub.com/home/pih Evaluation of setting time and compressive strength of a new bone cement precursor powder containing Mg–Na–Ca Mohammad Hossein Esnaashary, Hamid Reza Rezaie, Alireza Khavandi and Jafar Javadpour Abstract Taking the advantage of a novel magnesium phosphate precursor containing Na and Ca, the cementation rate of the cement, including only Mg/Mg–Na–Ca, was studied. Besides, two effective parameters, that is, calcination temperature, 650 °C and 800 °C, and powder-to-cement liquid ratio, 1 and 1.5g/mL, were assessed. X-ray diffraction, scanning elec- tron microscopy, ion chromatography, particle size analyser, Vicat needle and compression test were used to character- ize the powders and obtained cements. The sample containing Mg–Na–Ca, calcined at 800 °C with powder-to-cement liquid ratio of 1.5, obtained the highest compressive strength, 20MPa, but set fast. To control the kinetics of cementa- tion, the powder containing Mg–Na–Ca calcined at 950 °C with powder-to-cement liquid ratio of 1.5 and 2g/mL was assessed and the one with 2 g/mL set in 9 min possessing 22MPa compressive strength was selected as optimal condition to be used as a candidate, injectable bone cement. Keywords Biomaterial, magnesium, bone cement, magnesium phosphate cement, compressive strength, setting time Date received: 27 November 2017; accepted: 27 July 2018 Introduction Minimally invasive surgery is a method in which a patient is treated with the least amount of injury and consequently healed in a short time. 1 The method requires injectable biomaterials that can fill a complex defect after injection and set at biological condition, at 37 °C, 98% humidity and in contact with body fluids. 2 The setting time must be controlled. If it is too short, a surgeon does not have enough time to homogeneously mix precursor substances and inject the mixture. 3 On the other hand, if it lasts too long, maybe the injected cement washes out with biological fluids and cannot obtain required initial mechanical strength. 3,4 Usually, in bone treatment, the setting time should be in the range of 10–15 min and the mechanical strength must be around the natural bone’s mechanical strength, about 0.14–13.54 MPa for compressive strength of human cancellous bone. 3,5 Apatite (Ca 10 (PO 4 ) 6 (OH) 2 ) and brushite (CaHPO 4 2H 2 O) cements are common ceramic bone cements used in bone treatment. Apatite is produced from the reaction of a-tricalcium phosphate (a- Ca 3 (PO 4 ) 2 ) or tetracalcium phosphate (Ca 4 (PO 4 ) 2 O) with dicalcium phosphate (dihydrate) (CaHPO 4 ) and water at pH higher than 5. 6–8 And brushite is formed from the reaction of b-tricalcium phosphate (b- Ca 3 (PO 4 ) 2 ) and monocalcium phosphate monohydrate at pH lower than 4.2. 7,9,10 A cementing reaction occurs in two steps: in the first step, a precursor substance dis- solves the other one and creates a supersaturated solu- tion of released ions. 11 In the second step, neutral complexes form from the interaction of these ions, increasing the amount of the complexes that leads to gelation of the solution and an entangled network is created from the solids precipitated in the solution. 11 School of Metallurgy and Materials Engineering, Iran University of Science and Technology, Tehran, Iran Corresponding author: Hamid Reza Rezaie, School of Metallurgy and Materials Engineering, Iran University of Science and Technology, Narmak, Tehran 16844, Iran. Email: hrezaie@iust.ac.ir