Synthesis of Pore-Size-Tunable Porous Silica Particles and Their Effects on Dental Resin Composites

Preparation of Al-doped mesoporous silica spheres (Al-MSSs) for the improvement of mechanical properties and aging resistance of dental resin composites

OBJECTIVE

The purpose of this study was to synthesize Al-doped mesoporous silica spheres (Al-MSSs) and evaluate the effect of them as functional fillers on the mechanical properties and aging resistance of dental resin composites.

METHODS

Al-MSSs were prepared by a two-step method. The effect of Al-MSSs on the performance of the composites was evaluated using neat resin matrix, commercial composites 3M Z350XT and samples containing mesoporous silica spheres (MSSs) and nonporous silica spheres (NSSs) as control. The neat resin matrix consisted of resin monomer (Bisphenol A glycerolate dimethacrylate/triethylene glycol dimethacrylate, 49.5/49.5, wt%) and photoinitiator (camphor quinone/Ethyl-4-dimethylaminobenzoate, 0.2/0.8, wt%). The mechanical properties (flexural strength, flexural modulus, compressive strength and microhardness) of them were evaluated by a universal testing machine and microhardness tester. The mechanical stabilities of the prepared composites in wet environment were evaluated by immersing them in deionized water at 37 °C. In addition, we evaluated the effect of Al-MSSs on other properties of the dental resin composites such as polymerization shrinkage, degree of conversion, curing depth, contact angle, water sorption and solubility according to ISO 4049: 2019.

RESULTS

The synthesized Al-MSSs possessed good dispersibility with an average particle size of about 505 ± 16 nm. The mechanical properties of resin composites gradually increased with the increase of the loading amounts of inorganic fillers. The reinforcing effect of Al-MSSs was similar to that of MSSs and better than that of the NSSs groups at the same filler loading. After aging in deionized water at 37 °C for 30 days, the mechanical properties of all resin composites decreased. However, the decrease percentage of the composites filled with Al-MSSs was significantly lower than the other groups, indicating that the stability of the dental composites in wet environments was significantly improved by the Al-MSSs fillers. Furthermore, Al-MSSs had no obvious influence on the biocompatibility and other properties of dental resins.

SIGNIFICANCE

The prepared Al-MSSs could effectively improve the mechanical properties and aging resistance without sacrificing other physic-chemical properties of dental resin composites.

Urchin-like multiscale structured fluorinated hydroxyapatite as versatile filler for caries restoration dental resin composites

Caries is one of the most prevalent human diseases, resulting from demineralization of tooth hard tissue caused by acids produced from bacteria, and can progress to pulpal inflammation. Filling restoration with dental resin composites (DRCs) is currently the most common treatment for caries. However, existing DRCs suffer from low fracture strength and lack comprehensive anti-caries bioactivity including remineralization, pulp protection, and anti-cariogenic bacteria effects. In this study, inspired by plant roots' ability to stabilize and improve soil, fluorinated urchin-like hydroxyapatite (FUHA) with a three-dimensional whisker structure and bioactive components of calcium, phosphorus, and fluorine was designed and synthesized by a dynamic self-assembly method. Furthermore, versatile FUHA particles with different loading fractions were used as functional fillers to fabricate methacrylate-based DRCs, where the urchin-like hydroxyapatite (UHA) filled DRCs and commercial DRCs (Z350XT and BEAUTIFIL II) served as the control groups. The results demonstrated that FUHA with 50 wt% loading in resin matrix endowed DRC (F5) with excellent physicochemical properties, dentin remineralization property, cell viability, promotion of dental pulp stem cells mineralization, and antibacterial properties. Meanwhile, F5 also presented good clinical handling and aesthetic characteristics. Therefore, structure/functional-integrated FUHA filled DRCs have potential as a promising strategy for tooth restoration and anti-caries bioactivity.