SA Bender (BA), Dental student, University of Texas Health Science Center at San Antonio, School of Dentistry, San Antonio, TX, USA.
JP Schmitz (DDS, PhD), Associate Professor, Department of Oral and Maxillofacial Surgery, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.
JL Ong (PhD), Associate Professor, Department of Restorative Dentistry, Division of Biomaterials, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA.

Calcium phosphate (CaP) cements are used as implant materials for facial bone augmentation as well as cranioplasty and skeletal augmentation. They are used to improve alignment, fixation, and stabilization of healing fractured bones. Other uses of CaP bone cements have included their potential in delivering high concentrations of antibiotics and hormones to fractured bone sites. Success of CaP cement relies on the osteoconductive effect it has on adjacent bone by its inherent degradative property and its eventual replacement by normal bone. The setting reaction involving equimolar quantities of tetracalcium phosphate (Ca4(PO4)2) and dicalcium phosphate anhydrous (CaHPO4) with water proceeds by hydrolysis, dissolution, and precipitation of hydroxyapatite [Ca10(PO4)6(OH)2] from supersaturated solution. Acidified (H3PO4) and basic (CaOH2) byproducts are neutralized so that the setting reaction occurs close to a pH of 7 and is complete at 37°C in four hours. Because the reaction occurs at a nearconstant rate as determined by titration, inference is that zero-order reaction kinetics prevail.

Like the hydroxyapatite and CaP coatings on dental and orthopedic implants, it is also known that the initial cellular response to bone cement is partly dependent on the proteins adsorbed onto the surfaces. It has been hypothesized that as proteins from the biological fluids come in contact with synthetic surfaces, cellular adhesion, differentiation, and the production of the extracellular matrix production will be affected. Previous studies suggested that the CaP bone cement implant replacement by bone was postulated to occur through a combination of implant resorption coupled with osteoconduction. In other studies, no resorption of the CaP cement implant was reported regardless of the occurrence of fibrous union. Because dissolution of CaP from the surface of the implant in the human body contributes to the bioactivity of the CaP surface, the dissolution property of CaP bone cement may be critical to implant success. Therefore, the objective of this study was to simulate clinical conditions by evaluating the dissolution of CaP bone cement in different biofluids. The effect of dissolution on the CaP bone cement’s flexural strength was also investigated.