Calcium-Polyphosphate Submicroparticles (CaPP) Improvement Effect of the Experimental Bleaching Gels' Chemical and Cellular-Viability Properties

Abstract

The aim of this research was to develop and characterize the chemical and cellular-viability properties of an experimental high-concentration bleaching gel (35 wt%-H2O2) containing calcium-polyphosphate particles (CaPP) at two concentrations (0.5 wt% and 1.5 wt%). The CaPP submicroparticles were synthesized by coprecipitation, keeping a Ca:P ratio of 2:1. The CaPP morphology, size, and chemical and crystal profiles were characterized through scanning and transmission electron microscopy, energy-dispersive X-ray analysis, and X-ray diffraction, respectively. The assessed bleaching gels were experimental (without CaPP); 0.5% CaPP; 1.5% CaPP; and commercial. The gels’ pH values and H2O2 concentrations (iodometric titration) were determined. The odontoblast-like cell viability after a gel’s exposure was assessed by the MTT assay. The pH and H2O2 concentration were compared through a repeated-measures analysis of variance (ANOVA) and a Tukey’s test and the cell viability through a one-way ANOVA and a Tukey’s test using a GraphPad Prism (α < 0.05). The CaPP particles were spherical (with Ca and P, 135.7 ± 80.95 nm size) and amorphous. The H2O2 concentration decreased in all groups after mixing (p < 0.001). The 0.5% CaPP resulted in more-stable pH levels and higher viability levels than the experimental one (p < 0.05). The successful incorporation of CaPP had a positive impact on the bleaching gel’s chemical and cellular-viability properties when compared to the experimental gel without these particles.

Keywords: bleaching; cell survival; hydrogen peroxide; pH; polyphosphates; submicroparticles.

Figure 1

Morphological and chemical characterization of the synthesized calcium-polyphosphate particles: (a) scanning electron microscopy (SEM) images (×5000); (b) energy-dispersive X-ray analysis (EDX).

Figure 2

Sized and size distribution of the synthesized calcium-polyphosphate particles: (a) transmission electron microscopy (TEM); (b) dynamic light scattering (DLS).

Figure 3

Results of X-ray diffraction analysis (XRD) of the calcium-polyphosphate particles.

Figure 4

The pH mean values of the used bleaching gels in the different periods of assessment. Different letters in the bars indicate statistically significant differences among the groups (p ≤ 0.05). The results were obtained through triplicate analyses.

Figure 5

Cell viability (%) of the MDPC-23 cells after exposure to different concentrations of the bleaching gels (10, 50, and 100 µg/mL). * Statistically different from the rest of the groups (p < 0.05).

Figure 6

Graphical summary of the synthesis procedure of calcium-polyphosphate (CaPP) particles employing the coprecipitation method: (a) flow pump; (b) controlled addition of CaCl₂⋅2H₂O solution (1 mL/min; pH = 10) into the NaPP solution; (c) After 4 h of stirring, distribution of the crude product in falcon tubes; (d) washing of CaPP (twice with water and twice with ethanol); (e) Centrifugation after every wash; (f) CaPP slurry obtained; (g) CaPP dried fine powder.