A comparative study of mesoporous nanohydroxyapatite bionanocomposite from eggshells and fish scales through a mechanochemical method

Abstract

Dental hypersensitivity [DH] is a common pain amongst dental patients with a high negative impact on the quality of life. The onset of DH is attributable to the demineralisation of tooth enamel from excessive consumption of acidic drinks and beverages. While different materials have been reported for DH management, the application of nanoparticles is suggested to be the future of DH management. Particularly, the remarkable properties of mesoporous silica and nanohydroxyapatite have promoted their use for DH management. These materials are often synthesized following the wet-chemical route. However, the use of toxic chemicals and the cost associated made these processes infeasible for DH management. Given the said concern, this study synthesises nanohydroxyapatite (nHAp) from eggshell and fish scale waste and modified it with mesoporous silica to create a bionanocomposite (MSN@nHAp) via the mechanochemical method. Part of the study inquiry was to comparatively assess the remineralisation characteristics of nano-hydroxyapatite (nHAp) extracted from waste eggshells and fish scales. A quantitative approach to experimental research design is adopted in this study which includes three phases. The first looks to develop nanocomposite using nano-sized hydroxyapatite and mesoporous silica, then characterise the nanocomposite formed. Phase identification of the crystals was confirmed by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) applied to determine particle size and morphology. The second assesses the quality of the nanocomposite, its biocompatibility, and its toxicological characteristics. The third evaluates the remineralization capabilities of nHAp in occluding open dentin tubules. The mean values of the occluded area ratio in the SEM study were evaluated with one-way analysis of variance (ANOVA) with statistical software (IBM SPSS Statistics v28; IBM Corp), followed by a multi-comparison test with Bonferroni correction (α = .05). The validity of the study was achieved following SANS 1302 (2008) requirement for preparation, developing, and testing toothpaste. The reliability was determined via the reproducibility and repeatability of tests. Paper 1 investigated the remineralization and acid-resistant characteristics of nanohydroxyapatite produced from eggshell waste via mechanochemistry. Paper 1 established that nHAp was successfully produced from eggshell waste after 5 hr of milling. It was found that the produced nHAp (EnHAp) was effective in neutralizing common dietary acids. the nHAp showed complete occlusion of the dentin tubules. Manuscript 1 was based on the comparative assessment of the remineralization characteristics of Nano-hydroxyapatite extracted from fish scales and eggshells. Manuscript 1 established that nHAp extracted from eggshells (EnHAp) showed superior dentin tubule occluding characteristics than those of fish scales (FnHAp and mFnHAp). It was found that there were slight variations in physicochemical characteristics such as the Ca/P ratio, crystallinity, particle sizes and surface morphology of the nHAp extracted. Paper II reports on the invitro assessment of the acid resistance characteristics of mesoporous silica/nanohydroxyapatite (MSN@nHAp) biocomposite synthesised through the mechanochemical method. Paper II established that the MSN@nHAp exhibits superior acid resistance characteristics. In conclusion, the provided evidence shows that the mechanochemical method is a useful technique in the synthesis and surface modification of valuable biomaterials. The experimental finding provides a benchmark for further advance studies on utilizing natural nHAp in dentistry.