Dental resin composites with improved antibacterial and mineralization properties via incorporating zinc/strontium-doped hydroxyapatite as functional fillers

Abstract

This study intends to improve the antibacterial and mineralization performance of photocurable dental resin composites (DRCs) to reduce the possibility of repair failure caused by secondary caries. To the end, functionalized hydroxyapatite (HAp), including Zn-doped (Zn/HAp) and Sr-doped HAp (Sr/HAp), were added into the bisphenol A glycidyl methacrylate and triethylene glycol dimethacrylate mixture, providing the DRCs with antibacterial and mineralization capacity, respectively. By controlling the total amount of inorganic filler at 70 wt%, these HAp powders were introduced into the resin matrix with barium glass powder (BaGP), while the ratios of HAp to aGP varied from 0:70 to 8:62. And the 8 wt% of HAp could be pure HAp, Zn/HAp, Sr/HAp, or Zn/HAp +Sr/HAp in different ratios (i.e. 2:6, 4:4, 6:2). Though the fillers varied, the obtained DRCs displayed similar micro-morphology, flexural strength (∼110 MPa) and modulus (∼7 GPa), and Vickers hardness (∼65). When the doping amounts of Sr2+/Zn2+ reached 15 mol% of Ca2+ in the Sr/HAp and Zn/HAp, the DRCs displayed a high antibacterial activity by killing ∼95% Staphylococcus aureus, and induced rich mineral deposition on surface in simulated body fluid. The incorporation of the Zn/HAp and Sr/HAp into the DRCs did not cause significant cytotoxicity, with L929 fibroblasts remaining >99% viability as cultured in extracts made from the DRCs. Therein, the DRC preparations containing both Zn/HAp and Sr/HAp have achieved improvements in both the biomineralization and antibacterial performance, as well as, having sufficient mechanical properties and excellent biocompatibility for dental restoration.

A Multifunctional Dental Resin Composite with Sr-N-Doped TiO2 and n-HA Fillers for Antibacterial and Mineralization Effects

“…Hydroxyapatite (HA) has been noted as a suitable inorganic filler for bionic dental restoration materials. HA is a critical constituent of bone and dental tissues in the human body [ 32 ], which can release calcium and phosphorus ions to promote remineralization and repair the demineralized areas [ 33 , 34 ]. Par et al proved that DRC containing HA could form a precipitate layer on the surface after being immersed in artificial saliva (SBF) [ 35 ].…”

Construction of Mineralization Nanostructures in Polymers for Mechanical Enhancement and Functionalization

“…[17,37,38] The other is to utilize merits of the mineralization itself to functionalize, strengthen, and toughen different matrices (e.g., polymers, metals, ceramics). [39][40][41][42] While eyes are focused on the mineralization-modified polymer composites, endeavors to efficiently combine mineralization with matrix have resulted in the emergence of a diversity of novel multifunctional materials. For instance, hydrogels for cranial in situ regeneration, [43] high-strength polyimide vitrimers, [22] mineralized nanofiltration membranes with ultra-high separation efficiency, [44] and injectable mineralized hydrogels for tumor therapies.…”

Tackling current production of HAp and HAp-driven biomaterials

“…91,92 Many times, the ions chosen for calcium substitution led to both these characteristics (enhancement of biological response and antimicrobial properties). 72,93,94…”

“…91,92 Many times, the ions chosen for calcium substitution led to both these characteristics (enhancement of biological response and antimicrobial properties). 72,93,94 The ions that exhibit enhanced osteogenic activity are widely acknowledged in the literature, among which strontium (Sr 2+ ) and zinc (Zn 2+ ) are the most frequently mentioned, and often combined. [93][94][95] Strontium alone is said to improve the mechanical properties of HAp scaffolds, and its release into cell medium can activate transduction pathways that lead to osteogenesis.…”

“…103 Despite the numerous advantages of single ion substitutions, recent advancements have shifted towards the implementation of co-substitutions, where two ions are incorporated into the crystalline structure of HAp. 4,93,95,98,104,105 Another approach involves the fusion of two single substituted HAp into a single three-dimensional material. Silver is widely used as an antibacterial/antifungal substance and is present in many Al 3+ 90 commercially available products, such as wound dressings.…”