Enamel Mineral Content Changes After Bleaching With High and Low Hydrogen Peroxide Concentrations: Colorimetric Spectrophotometry and Total Reflection X-ray Fluorescence Analyses

Abstract

The purpose of this study was to evaluate the calcium (Ca) and phosphorous (P) content in enamel bleached with high and low concentrations of hydrogen peroxide (HP) using Total Reflection X-Ray Fluorescence (TXRF) and colorimetric spectrophotometry (SPEC). Forty-eight sound human third molars were used. Their roots were embedded in polystyrene resin and immersed for seven days in an artificial saliva solution. Then they were distributed into six groups to receive the bleaching treatments. The agents of high HP concentration (for in-office use) evaluated were Whiteness HP Maxx/FGM (35% HP), Whiteness HP Blue/FGM (35% HP, 2% calcium gluconate), Pola Office+/SDI (37.5% HP, 5% potassium nitrate), and Opalescence Boost/Ultradent (38% HP, 1.1% ion fluoride, 3% potassium nitrate); these agents were applied to enamel in three sessions. The agents of low HP concentration (for home use) evaluated were Pola Day/SDI (9.5% HP) and White Class 10%/FGM (10% HP, potassium nitrate, calcium, fluoride), and these agents were applied for 14 days. Enamel microbiopsies were evaluated by TXRF and SPEC analysis before the bleaching treatment (baseline), during the treatment, and 14 days after the end of the treatment. For TXRF, the Kruskal-Wallis test showed that Ca and P were not influenced by agent (p>0.05). For SPEC, Pola Office+, Opalescence Boost, Pola Day, and White Class 10% caused a decrease of Ca over time; there was a significant decrease of P over time to Pola Office+ and White Class 10%. The Spearman test showed no correlation between the Ca (p=0.987; r=-0.020) and P (p=0.728, r=0.038) obtained by SPEC and TXRF. For TXRF and SPEC, changes in Ca and P during bleaching occurred independently of the HP concentration used.

Effect of in-office bleaching gels with calcium or fluoride on color, roughness, and enamel microhardness

“…The reaction products are lower in molecular weight when compared to the original stain molecule, and these properties make the products easier to remove from the dental structure (7). Regardless of the technique and bleaching agent employed, adverse effects have been reported, to include: tooth sensitivity (8); changes in surface morphology; and changes to the physical-chemical properties of the dental hard tissues such as an increase in enamel roughness, a decrease in surface microhardness, and an alteration in mineral content (9)(10)(11)(12)(13). Some remineralizing compounds, such as fluoride, calcium, bioactive glass, arginine/calcium carbonate, and nanohydroxyapatite; have been investigated to minimize these adverse effects (10,12,(14)(15)(16).…”

"Efficacy and Adverse Effects of Dental Bleaching in the Office: Literature Review"

“…Although there are protocols that reduce the contact time between the bleaching agent and the tooth structure, there are several adverse effects found in the literature, the most common being tooth sensitivity [4,9,11,12,, which is generally associated with the ability of hydrogen peroxide to diffuse rapidly through enamel and dentin and penetrate the pulp, causing intense damage [3,9,17,19,20], as pulp inflammatory reactions [11,19,21], reduced cell proliferation and reduced pulp repairing capacity, which can lead to reversible pulpitis or even tissue necrosis [3,14,22]. Morphological changes in enamel and dentin and changes in mineral content can also occur resulting in the presence of erosions, porosities (which can lead to possible bacterial colonization), 23 decreased microhardness and nano hardness, increased surface roughness and dental demineralization, as well as fracture toughness [4,5,12,[15][16][17]21,23].…”

“…The side effects of office bleaching may be associated with the composition of bleaching agents, concentration, since the higher the concentration, the greater the probability of hydrogen molecules reaching the dentinal tubules, the pH values (the lower pH may be the main reason for the negative effects) the treatment time, the increase in the temperature of the pulp with the use of light and the different application techniques [5,11,[14][15][16][19][20][21]23]. Thus, it is necessary to take measures to minimize the possible adverse effects during the bleaching treatment [15].…”

“…Thus, it is necessary to take measures to minimize the possible adverse effects during the bleaching treatment [15]. The use of laser therapy can minimize tooth hypersensitivity by stimulating cell differentiation, increasing tissue repair and reducing inflammation.3 Calcium and / or fluoride can also be added to the composition of bleaching gels and the application of fluoride after treatment to reduce the risk of demineralization or loss of mineral enamel content [16,17,202].…”

Lesões Endodôntico-Periodontais: Conhecimento Dos Dentistas Da Rede Pública De Arcoverde

“…Pinto et al, (2017) investigaram os efeitos do peróxido de hidrogênio 30% em relação à microdureza da superfície do esmalte bovino e constataram que, após o tratamento clareador, o esmalte apresentou degradação e amolecimento, além de perda do conteúdo mineral. No presente estudo, o polimento realizado imediatamente ao final da sessão clareadora foi mais eficaz em remover a camada amolecida.…”