Evaluation of the incorporation of calcium polyphosphate sub-microparticles into high-concentration hydrogen peroxide-based bleaching gels and analysis of their effects on the dental enamel physicochemical properties

Author(s)

Mariangela Ivette Guanipa Ortiz

• Document type: Doctoral Thesis
• Press: Piracicaba, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Odontologia de Piracicaba (FOP)
• Defense date: 2023-10-20

Examining board members

Débora Alves Nunes Leite Lima; Flavio Henrique Baggio Aguiar; Rafael Leonardo Xediek Consani; Fabiana Mantovani Gomes França; Cecy Martins Silva

• Advisor: Klaus Heinz Rischka; Débora Alves Nunes Leite Lima

Abstract

The present study characterized an experimental bleaching gel based on hydrogen peroxide (HP) at high concentration (35%) containing sub-microparticles of calcium polyphosphate (CaPP) associated or not with a phosphatase enzyme (ALP), and evaluated in vitro its effect on the physicochemical properties of dental enamel. For the first phase of the study, CaPP sub-microparticles were synthesized by co-precipitation. The morphology, size, and chemical characteristics and the CaPP phase were characterized by scanning and transmission electron microscopy, energy dispersive X-ray spectroscopy (EDX), and X-ray diffraction, respectively. The bleaching gels evaluated were: Commercial (Whiteness HP Maxx, FGM); Experimental (without CaPP); 0.5%-CaPP; 1.5%- CaPP. The pH values of the gels and HP concentration (titration) were determined. The viability of odontoblast-like cells (MDPC-23) after gel exposure was assessed by MTT assay. For the second phase of the study enamel/dentin specimens were prepared and randomized into: Control (No treatment); Commercial; Experimental; 0.5%-CaPP; 1.5%-CaPP. The bleached groups received three bleaching sessions. Before, during, and after bleaching the specimens had their physical, mechanical, and chemical properties evaluated by reflectance spectrophotometry (?E, ?E00, ?WID), roughness (Ra), surface microhardness (SMH), and EDX and Raman spectroscopy (FT-Raman), respectively. For the third phase of the study, ALP activity and chemical properties (PO43? concentration) of gels containing or not containing ALP were evaluated by colorimetric assays in water-based or tris-based thickeners. Also enamel/dentin specimens were allocated to receive three bleaching sessions in: Control (No treatment); Commercial; Exp-H (Experimental in H2O); CaPP-H (0.5 wt%); CaPP-H+ALP (ALP); Exp-T (Experimental in Tris); CaPP-T (0.5 wt%); CaPP-T+ALP (ALP). Before, during, and after bleaching the specimens had their physical and mechanical properties evaluated by reflectance spectrophotometry (?E, ?E00, ?WID), SMH, and cross-sectional microhardness (CSMH). After statistical analysis of each phase of the study, it was determined that the: CaPP particles were spherical, with Ca and P, a diameter of 135.7 ± 80.95 nm, and amorphous. The HP concentration decreased in all groups after mixing. The 0.5%-CaPP group showed more stable pH levels and higher viability than the Experimental. PO43? levels were higher in the thickeners containing ALP. After bleaching, the groups treated with CaPP-containing gels showed similar bleaching efficacy (?E, ?E00, ?WID) to the Commercial. There was no significant change in the specimens’ Ra. The Experimental group showed a change in its carbonate content and lower Ca:P values. While SMH and CSMH values were higher for the groups containing CaPP, especially when associated with ALP. Thus, it is possible to establish that the synthesis, characterization, incorporation, and analysis of the physical and chemical properties of the enamel bleached with experimental bleaching gels containing CaPP and especially associated with ALP presents a good potential to reduce the alterations associated with the bleaching procedures with HP in high concentration in a biologically inspired way (AU)

• FAPESP's process: 19/20272-1 - Development of a hydrogen peroxide bleaching agent with the addition of calcium polyphosphate nanoparticles and its effect on the whitening and mineralization of dental enamel
• Grantee: Mariangela Ivette Guanipa Ortiz
• Support Opportunities: Scholarships in Brazil - Doctorate