Development of a bioactive resin composite incorporating nanohydroxyapatite for remineralization in minimally invasive dentistry

Project Abstract

This study presents the development and evaluation of a bioactive resin composite enhanced with nanohydroxyapatite (n-HA) designed for remineralization in minimally invasive dentistry. The resin matrix was formulated using a Bis-GMA/TEGDMA base with a silanized nano-fillers system to optimize mechanical properties, wear resistance, and optical aesthetics while incorporating varying concentrations (0.5, 1.0, 2.0 wt%) of n-HA to promote remineralization at the tooth–restoration interface. Surface modification of n-HA with silane coupling agents aimed to improve filler–matrix bonding, dispersion, and ion release kinetics. Comprehensive physicochemical characterization included Fourier-transform infrared spectroscopy (FTIR) to confirm functional groups, differential scanning calorimetry (DSC) for polymerization behavior, and thermogravimetric analysis (TGA) to assess thermal stability. Morphological analysis via scanning electron microscopy (SEM) and transmission electron microscopy (TEM) evaluated filler distribution and interaction with the resin matrix, while X-ray diffraction (XRD) assessed the crystalline phases of n-HA within the composite. Mechanical testing encompassed flexural strength, fracture toughness, and wear resistance under simulated masticatory cycles, comparing the n-HA-enhanced formulations with a conventional control resin. In vitro bioactivity was investigated using simulated body fluid (SBF) immersion and lactic acid challenge to simulate acidic demineralization, with ion release profiles (Ca2+, PO4 3?, and OH?) monitored by inductively coupled plasma optical emission spectrometry (ICP-OES). Remineralization potential was evaluated using an artificial caries model on human dentin and enamel lesions, employing microhardness mapping (Knoop hardness) and transverse microradiography (TMR) to quantify mineral gain and lesion depth reduction over 28 days. Cytocompatibility was assessed using human dental pulp stem cells (hDPSCs) to determine cell viability, proliferation, and alkaline phosphatase activity in the presence of eluates from each composite formulation. The results demonstrated that 1.0 wt% n-HA achieved the optimal balance between mechanical integrity and bioactivity, with enhanced flexural strength and wear resistance comparable to the control while exhibiting a sustained release of calcium and phosphate ions that promoted nucleation and crystal growth at demineralized substrates. In vitro remineralization showed a significant increase in surface microhardness and mineral density, with TMR revealing reduced lesion depth and accelerated remineralization front progression in the n-HA groups, particularly under cyclic acid challenges. SEM/TEM analysis confirmed homogeneous filler dispersion and robust interfacial bonding, mitigating crack propagation under simulated mastication. Ionic release remained within physiological ranges, and cytocompatibility assays indicated no adverse effects on hDPSCs, suggesting favorable biocompatibility. The study discusses the influence of n-HA content on polymerization kinetics, the trade-off between remineralization potential and polymer/ion leakage, and the implications for clinical translation in minimally invasive dentistry. Limitations include the in vitro nature of the assays and the need for long-term in vivo studies to evaluate wear behavior, aging effects, and real-time remineralization under dynamic oral conditions. Overall, the bioactive resin composite with optimally dispersed nanohydroxyapatite presents a promising material for minimally invasive restorations that actively participate in dentin and enamel remineralization while maintaining structural integrity and clinical handling suitable for adhesive dentistry workflows.

Project Overview

What This Project Is About

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The project looks at a new resin-based dental material that contains tiny particles of nanohydroxyapatite to help teeth remineralize. It explores whether this bioactive material can repair early decay and support healthy tooth surfaces when used in minimally invasive dental treatments.

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The Problem It Addresses

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Early tooth decay is common and often treated with drilling or removing decayed tissue. A material that releases minerals to repair the tooth and strengthens it could reduce invasiveness, protect healthy tissue, and improve long-term tooth survival.

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Objectives of the Project

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1. Understand how adding nanohydroxyapatite affects remineralization in the resin.
2. Evaluate the material’s biocompatibility with oral tissues.
3. Test mechanical properties to ensure it withstands biting forces.
4. Assess bonding to enamel and dentin under realistic use conditions.
5. Compare remineralization potential with conventional restoratives.

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What You Will Do Step by Step

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1) Review basic literature on remineralization and bioactive composites. 2) Formulate resin with nanohydroxyapatite and prepare test samples. 3) Conduct lab tests for mineral release and remineralization potential. 4) Perform mechanical tests (strength, wear resistance). 5) Test bonding to tooth surfaces in simulated conditions. 6) Analyze data to identify improvements over standard materials. 7) Discuss clinical implications and limitations.

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Expected Outcome

Expected to yield a resin composite that releases minerals to support remineralization while maintaining adequate strength and bonding. The study should show potential for reducing invasive procedures and improving longevity of restorations in early decay cases.