Effect of Magnetic Field on Dentin Remineralisation using Magnetic Nanoparticle Incorporated Nanohydroxyapatite and Calcium Phosphate Ion Clusters: An In-vitro Study

Introduction: Dentin caries leads to significant tooth structure loss, especially comma where restorative access is limited. While conventional treatments replace decay mechanically, they often neglect dentin’s biological potential for remineralisation. Agents like nanohydroxyapatite, fluoride, Casein Phosphopeptide - Amorphous Calcium Phosphate (CPP-ACP), and bioactive glass can promote surface-level mineral repair but typically fall short in regenerating deeper intrafibrillar structures vital for functional dentin remineralisation. Aim: To investigate the effect of a magnetic field on dentin remineralisation using Nanohydroxyapatite (NHAP), Magnetic Nanoparticle-Enhanced Nanohydroxyapatite (MNHAP), and its combination with Calcium Phosphate Ion Clusters (CPIC). Materials and Methods: This in-vitro study was conducted at the Department of Conservative Dentistry and Endodontics at Sibar Institute of Dental Sciences in Guntur, Andhra Pradesh, India, from September 2022 to November 2022. Ninety-six dentin blocks were prepared from 48 extracted mandibular molars using a slow-speed water-cooled diamond saw. Samples were divided into four groups: Group A – Control, Group B – NHAP, Group C – MNHAP, and Group D – CPIC + MNHAP. Powder X-ray Diffraction (XRD) analysis was performed for Group D to assess particle structure and phase. Knoop microhardness, High-resolution Transmission Electron Microscopy (HRTEM), and Scanning Electron Microscopy-Energy-Dispersive X-ray Spectroscopy (SEM-EDAX) were used to evaluate dentin hardness, particle morphology, and surface elemental composition, respectively. Overall and within-group comparisons were performed using Analysis of Variance (ANOVA) and repeated-measures ANOVA, respectively, with a significance level set at p-value <0.05. Results: Microhardness varied significantly among the groups, with group D displaying the highest values (61.2067±12.15492) (p-value <0.001*). XRD confirmed the transformation of CPIC into amorphous calcium phosphate, which later converted to nanohydroxyapatite in group D. TEM revealed uniformly distributed, crystalline rod-shaped nanoparticles in MNHAP and CPIC+MNHAP samples, whereas NHAP showed needle-shaped crystals. EDAX analysis indicated the highest Ca/P ratio in group D and confirmed the presence of Fe ions in groups C and D. Conclusion: MNHAP alone and in combination with CPIC, under a magnetic field, enhanced dentin remineralisation, indicating potential applicability of magnetically assisted nanoparticlebased dentin repair.