Dentinal tubules occlusion after application of experimental toothpastes containing bioactive glasses: a magical angle spinning-nuclear magnetic resonance (MAS-NMR) analysis

• Grant number: 21/07513-0
• Support type: Scholarships abroad - Research Internship - Doctorate
• Effective date (Start): December 01, 2021
• Effective date (End): November 30, 2022
• Field of knowledge: Health Sciences - Dentistry - Dental Materials
• Principal researcher: Linda Wang
• Grantee: Victor Mosquim
• Supervisor abroad: Robert Hill
• Home Institution: Faculdade de Odontologia de Bauru (FOB). Universidade de São Paulo (USP). Bauru , SP, Brazil
• Research place: Queen Mary University of London, England
• Associated to the scholarship: 19/21128-1 - The role of bioactive, resinous and fluoridated agents in the treatment of dentin hypersensitivity and their interaction with sound and eroded dentin: in vitro and clinical studies, BP.DR

Abstract

Soluble bioactive glasses (BG) have been developed to be used in dental products such as toothpastes with a promising effect on dentine hypersensitivity (DH) management. This occurs because, after dissolution and hydrolysis, minerals are deposited on the dentine surface and reduce the lumen of dentinal tubules, reducing their permeability. Therefore, given that BGs in toothpastes formulations can control DH, the aim of this in vitro study is to develop a new bioactive glass-based toothpaste, to evaluate its effectiveness in occluding the dentinal tubules, and to analyse the resulting compound formed after tooth brushing. Two BG will be prepared using SiO2, P2O5, CaCO3, SrCO3, Na2CO3, CaF2 and SrF2, and 1 g will be added to the formulation of the toothpaste (F17 BG and F32 BG) to be compared to 4 main commercial formulations with different mechanisms. Then, specimens of human dentine will be cut into 0.6-mm-thick discs and equally distributed into six groups (n=13/group): F17 BG, F32 BG, BioMin F, Elmex Protection Erosion, Sensodyne Repair & Protect, or Crest Cavity Protection. For each toothpaste, the dentine discs will be cut into four equal parts, where the first will be set as the negative control part (without brushing), and the other parts will be submitted to brushing with 50mg of toothpaste for 30 s. After brushing, the second part will be rinsed with deionized water; the third will be immersed in artificial saliva for 8 h; and the fourth will be immersed in 6% citric acid for 2 minutes. The specimens will be analysed under Laser Scanning Confocal Microscope, Scanning Electron Microscope and Energy-dispersive X-ray spectroscopy to evaluate the presence of mineral deposits onto the dentine surface and at the aperture of dentinal tubules, their chemical composition and to quantify the number of open, partially occluded and fully occluded tubules. Also, 19F magic angle spinning-nuclear magnetic resonance will be used to confirm the presence of fluorapatite on the dentine surface after tooth brushing and after rinsing with water, immerging in artificial saliva or after citric acid. The toothpastes will be assessed regarding their total fluoride concentration and pH (n=3). If the data present normal distribution and homogeneity, 2-way ANOVA and post-hoc Tukey will be applied. If not, Kruskal-Wallis and post-hoc Dunn tests will be used to compare the percentages of open, partially occluded and occluded tubules between toothpastes and for comparisons between dentine parts after treatment with the same toothpaste. The significance level will be set at 5%.