Intrinsic biointeractivity-related apatite-forming ability vs. chemi/physisorption-related calcium-phosphate deposition of some current root-end filling materials

Objectives: Different commercial root-end filling materi- als, namely two zinc-oxide based cements (IRM, Superseal), a glass ionomer cement (Vitrebond) and three calcium-silicate cements (ProRoot MTA, MTA Angelus and Tech Biosealer root end), were examined for their ability: (a) to release calcium (Ca) and hydroxyl (OH) mineralizing ions (biointeractivity) and (b) to form apatite (Ap) or different calcium phosphate (CaP) deposits when immersed in simulated body fluid. The corre- lation between the ions-releasing and the apatite formation was analyzed. Materials and methods: Material discs were prepared and immediately immersed in simulated body fluid HBSS (Hank’s Balanced Salt Solution) for 1–28 days. Ca and OH ions release was measured by potentiometric method using ions-selective probes. Ultramorphological and chemical surface modifica- tions and the formation of Ap and CaP was assessed by ESEM/EDX, micro-Raman and FTIR analyses. Results: IRM and Superseal released small quantities of Ca and no OH ions but none was released by Vitrebond. Uneven sparse CaP deposit was observed after long soaking times. ProRoot MTA, MTA Angelus and Tech Biosealer root end released significant amounts of Ca and OH ions throughout the experiment period (two-way Anova with Tukey, p < 0.05). After 1 day of soaking, ESEM/EDX showed the formation of apatite nano-spherulites and the appearance of phosphate peaks, and micro-Raman and FTIR spectra evidenced the formation of amorphous calcium/magnesium phosphates. A porous biocoating of car- bonated apatite was observed after 7–28 days. Conclusions : Current root-end filling materials possess widely different properties of biointeractivity (chemical interplay) and apatite-forming ability (biomineralization prop- erties). Conventional zinc-oxide and glass-ionomer cements had virtually no ability to release the relevant ions: they simply act as substrate for the eventual chemical bonding/adsorption of environmental ions and inhomogeneous precipitation of calcium-phosphate deposits after a long soaking/induction period (extrinsic chemi/physisorption-related CaP deposi- tion). Calcium-silicate MTA cements showed a marked calcium release and basifying effect and rapid apatite formation (fast intrinsic biointeractivity-related Ap-forming ability correlated with their high ions releasing property). These materials may promote bone regeneration and may be recommended as bio- logically active materials in clinical situations where fast bone tissue formation is required such as in the presence of peri- apical bone defects