A comparative study of mesoporous nanohydroxyapatite bionanocomposite from eggshells and fish scales through a mechanochemical method
Authors:   , Mkhize Sandile Cromwell 
Published: November 2024

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.