Multifunctional Dental Adhesives Formulated with Silane-Coated Magnetic Fe₃O₄@m-SiO₂ Core–Shell Particles to Counteract Adhesive Interfacial Breakdown

Abstract

The process of bonding to dentin is complex and dynamic, greatly impacting the longevity of dental restorations. The tooth/dental material interface is degraded by bacterial acids, matrix metalloproteinases (MMPs), and hydrolysis. As a result, bonded dental restorations face reduced longevity due to adhesive interfacial breakdown, leading to leakage, tooth pain, recurrent caries, and costly restoration replacements. To address this issue, we synthesized and characterized a multifunctional magnetic platform, CHX@SiQuac@Fe 3 O 4 @m-SiO 2 , to provide several beneficial functions. The platform comprises Fe 3 O 4 microparticles and chlorhexidine (CHX) encapsulated within mesoporous silica, which was silanized by an antibacterial quaternary ammonium silane (SiQuac). This platform simultaneously targets bacterial inhibition, stability of the hybrid layer, and enhanced filler infiltration by magnetic motion. Comprehensive experiments include X-ray diffraction, FT-IR, VSM, EDS, N 2 adsorption−desorption (BET), transmission electron microscopy, scanning electron microscopy, thermogravimetric analysis, and UV−vis spectroscopy. Then, CHX@SiQuac@Fe 3 O 4 @m-SiO 2 was incorporated into an experimental adhesive resin for dental bonding restorations, followed by immediate and long-term antibacterial assessment, cytotoxicity evaluation, and mechanical and bonding performance. The results confirmed the multifunctional nature of CHX@SiQuac@Fe 3 O 4 @m-SiO 2 . This work outlined a roadmap for (1) designing and tuning an adhesive formulation containing the new platform CHX@SiQuac@Fe 3 O 4 @m-SiO 2 ; (2) assessing microtensile bond strength to dentin using a clinically relevant model of simulated hydrostatic pulpal pressure; and (3) investigating the antibacterial outcome performance of the particles when embedded into the formulated adhesives over time. The results showed that at 4 wt % of CHX@SiQuac@Fe 3 O 4 @m-SiO 2 -doped adhesive under the guided magnetic field, the bond strength increased by 28%. CHX@SiQuac@Fe 3 O 4 @m-SiO 2 enhanced dentin adhesion in the magnetic guide bonding process without altering adhesive properties or causing cytotoxicity. This finding presents a promising method for strengthening the tooth/dental material interface's stability and extending the bonded restorations' lifespan.

Antimicrobial properties and bonding durability of pH-responsive dentin adhesives with chlorhexidine-load mesoporous silica nanoparticles

“…In this study, two types of artificial saliva with different pH levels (7.4 and 5.0) were utilized to simulate the in vitro drug release behavior. The selection of these two pH values was based on the fact that pH 7.4 represents the normal physiological conditions of saliva, while pH 5.0 mimics the acidic microenvironment caused by caries bacteria within teeth (Mokeem et al, 2024). These two pH levels simulated both healthy oral conditions and caries-induced oral conditions respectively.…”

Promotion of Dentin Biomimetic Mineralization and Bonding Efficacy by Interfacial Control of an Experimental Citric Acid Dental Etching Agent

“…Dentin bonding failure leads to microleakage, staining, secondary caries, and postoperative sensitivity . Despite the excellent immediate bond strength, the durability of dentin bonding is still limited.…”