Clear Aligners with Hydroxyapatite Coating: Enamel Remineralization under Demineralizing Conditions – An In Vitro Study

Prasad Konda; Farheen Rafik Patel; M. Arshad Hussain; Laeque Bangi; Md Nasiruddin; Revati Patil

doi:10.36948/ijfmr.2025.v07i05.58586

Clear Aligners with Hydroxyapatite Coating: Enamel Remineralization under Demineralizing Conditions – An In Vitro Study

Author(s)	Dr. Prasad Konda, Dr. Farheen Rafik Patel, Dr. M. Arshad Hussain, Dr. Laeque Bangi, Dr. Md Nasiruddin, Dr. Revati Patil
Country	India
Abstract	Introduction: Enamel demineralization and white spot lesions (WSLs) remain concerns during orthodontic treatment, including with clear aligners (CAs). Although CAs are considered hygienic, reduced salivary flow and acidic microenvironments can promote mineral loss. Hydroxyapatite nanoparticles (HANPs), known for their biocompatibility and enamel-regenerating properties, may offer a preventive solution. Objective: To evaluate whether HANP-coated clear aligners can prevent enamel demineralization and promote remineralization under simulated cariogenic conditions. Materials and Methods: In this in vitro study, 90 extracted premolars were divided into two groups: Group 1 (HANP-coated aligners) and Group 2 (uncoated aligners). Custom aligners were fabricated and coated using RF magnetron sputtering. Enamel samples were immersed in a pH 4.5 demineralizing solution for 1 and 2 weeks. Evaluations included Ca/P ratio (EDS), surface microhardness (VHN), enamel thickness (SEM), and surface morphology (SEM scoring). Data were statistically analyzed using SPSS (p < 0.05). Results: Group 1 showed only a 4% loss in Ca/P ratio versus 18.3% in Group 2. Microhardness decreased by just 1.4% in Group 1, compared to 18.5% in controls. Enamel thickness loss was 8.2% in the coated group versus 19% in the control. SEM analysis revealed 33% of coated samples returned to pristine surfaces (Score 0), while 53% of control samples showed severe damage (Score 3). The HANP coating (~36.7 nm particles, 0.12–0.15 μm thickness) maintained >92% light transmittance. Conclusion: HANP-coated aligners significantly preserved enamel mineral content, microhardness, and thickness while enhancing surface morphology, offering a promising preventive strategy against demineralization during clear aligner therapy.
Keywords	Tooth Demineralization, Orthodontic Appliances, White Spot Lesions, Thermoplastic Aligners, Hydroxyapatite Nanoparticles, Remineralization, Surface Properties, Scanning Electron Microscopy, Enamel mineral content, microhardness, surface morphology and surface thickness.
Field	Medical / Pharmacy
Published In	Volume 7, Issue 5, September-October 2025
Published On	2025-10-22
DOI	https://doi.org/10.36948/ijfmr.2025.v07i05.58586

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Clear Aligners with Hydroxyapatite Coating: Enamel Remineralization under Demineralizing Conditions – An In Vitro Study

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