Remineralizing potential of dental composites containing silanized silica-hydroxyapatite (Si-HAp) nanoporous particles charged with sodium fluoride (NaF)

A review of new generation of dental restorative resin composites with antibacterial, remineralizing and self-healing capabilities

Dental restorative resin composites are widely used to repair tooth decay owing to attractive esthetics, adequate mechanical properties and minimally invasive tooth structure preparations. Nevertheless, dental restorative resin composites still face challenges because of their relatively high failure rate and short lifespan caused by secondary caries and bulk fracture. Thus, attempts have been carried out to explore a new generation of dental restorative resin composites with antibacterial, remineralizing, and self-healing capabilities to inhibit bacteria and lengthen the lifetime of the restorations. Such novel restorative composites can inhibit bacterial activity, reduce acid production, promote mineral regeneration and present a renewable advantage to achieve a higher performance, which are inspiring and provide support for further basic and clinical research. In this review, antibacterial dental restorative resin composites are first introduced, followed by remineralizing, self-healing, and multifunctional dental resin composites with two or more of the functions mentioned above. Meanwhile, we explain the mechanism of the corresponding dental restorative resin composites and describe their characteristics. Finally, we conclude and put forward prospects. This review will attract both researchers and clinicians in this field and help to provide innovative ideas to design new restorative resin composites for biomedical applications.

Dental Applications of Ion-Substituted Hydroxyapatite: A Review of the Literature

Hydroxyapatite (HA) forms an essential constituent of human teeth and bone. Its distinctive characteristic features, such as bioactivity and osteoconductivity, make it an ideal candidate to be used as an implant coating in restorative dentistry and maxillofacial surgery for bone regeneration. However, low fracture toughness and brittleness are a few of the inherent features of HA, which limit its application in load-bearing areas. The potential of HA to engage its lattice structure with either partial or complete substitution with external ions has become an increasing area of research as this phenomenon has the potential to enhance the biological and functional properties of the material. Consequently, this review aimed to highlight the role of various substituted ions in dental applications. Data indicate that the newly formed HA-substituted biomaterials demonstrate enhanced remineralization and antimicrobial activity along with improved hardness. Ion-substituted HA offers a promising strategy for future clinical research as these materials may be incorporated into various dental products for therapeutic treatments.

Restorative Dental Resin Functionalized with Calcium Methacrylate with a Hydroxyapatite Remineralization Capacity

The ability of dental materials to induce the mineralization of enamel like hydroxyapatite (HA) is of great importance. In this article, a novel kind of dental restorative material characterized by a mineralization ability was fabricated by photopolymerization. Calcium methacrylate (CMA) was introduced into the classical bisphenol A-glycidyl methacrylate (Bis-GMA) and triethylene glycol dimethacrylate (TEGDMA) dental resin formulation. This functional dental resin (BTCM) was calcium-rich and can be prepared simply by one-step photopolymerization. The influence of CMA on the photopolymerization kinetics, the dental resin's mechanical properties, and its capacity to induce dynamic in situ HA mineralization were examined. Real-time FTIR, compression modulus, scanning electron microscopy, X-ray spectroscopy, MTT assay, and cell attachment test were carried out. The obtained data were analyzed for statistical significance using analysis of variance (ANOVA). Double bond conversion could be completed in less than 300 s, while the compression modulus of BTCM decreased with the increase in CMA content (30 wt%, 40 wt%, and 50 wt%). After being soaked in Ca(NO3)2 and Na2HPO4 solutions alternatively, dense HA crystals were found on the surface of the dental resin which contained CMA. The amount of HA increased with the increase in CMA content. The MTT results indicated that BTCM possesses good biocompatibility, while the cell adhesion and proliferation investigation demonstrated that L929 cells can adhere and proliferate well on the surface of BTM. Thus, our approach provides a straightforward, cost-effective, and environmentally friendly solution that has the potential for immediate clinical use.

The effect of calcium phosphate ion clusters in enhancing enamel conditions versus Duraphat and Icon

This study aimed to evaluate and compare the remineralisation, mechanical, anti-aging, acid resistance and antibacterial properties of calcium phosphate ion clusters (CPICs) materials with those of Duraphat and Icon. The remineralisation and mechanical properties were investigated using scanning electron microscopy, Fourier-transform infrared (FTIR) spectroscopy and nanoindentation. CPICs induced epitaxial crystal growth on the enamel surface, where the regrown enamel-like apatite layers had a similar hardness and elastic modulus to natural enamel (p > 0.05). Acid resistance and anti-aging properties were tested based on ion dissolution and surface roughness. CPICs exhibited similar calcium and phosphate ion dissolution to the control (p > 0.05), and its roughness decreased after thermocycling (p < 0.05), thereby decreasing the risk of enamel surface demineralisation. The minimum inhibitory concentration was 0.1 mg/ml, and the minimum bactericidal concentration ranged from 0.05 to 0.1 mg/ml. Overall, this biomimetic CPICs is a promising alternative to dental demineralisation.

Micromechanical interlocking structure at the filler/resin interface for dental composites: a review

Dental resin composites (DRCs) are popular materials for repairing caries or dental defect, requiring excellent properties to cope with the complex oral environment. Filler/resin interface interaction has a significant impact on the physicochemical/biological properties and service life of DRCs. Various chemical and physical modification methods on filler/resin interface have been introduced and studied, and the physical micromechanical interlocking caused by the modification of fillers morphology and structure is a promising method. This paper firstly introduces the composition and development of DRCs, then reviews the chemical and physical modification methods of the filler/resin interface, mainly discusses the interface micromechanical interlocking structures and their enhancement mechanism for DRCs, finally give a summary on the existing problems and development potential.

The power of weak ion-exchange resins assisted by amelogenin for natural remineralization of dental enamel: an in vitro study

This study aims to develop an innovative dental product to remineralize dental enamel by a proper combination of ion-exchange resins as controlled release of mineral ions that form dental enamel, in the presence of amelogenin to guide the appropriate crystal growth. The novel product proposed consists of a combination of ion-exchange resins (weak acid and weak base) individually loaded with the remineralizing ions: Ca²⁺, PO₄^3- and F^-, also including Zn²⁺ in a minor amount as antibacterial, together with the protein amelogenin. Such cocktail provides onsite controlled release of the ions necessary for enamel remineralization due to the weak character of the resins and at the same time, a guiding tool for related crystal growth by the indicated protein. Amelogenin protein is involved in the structural development of natural enamel and takes a key role in controlling the crystal growth morphology and alignment at the enamel surface. Bovine teeth were treated by applying the resins and protein together with artificial saliva. Treated teeth were evaluated with nanoindentation, scanning electron microscopy and energy-dispersive X-ray spectroscopy. The innovative material induces the dental remineralization creating a fluorapatite layer with a hardness equivalent to sound enamel, with the appropriate alignment of corresponding nanocrystals, being the fluorapatite more acid resistant than the original mineral. Our results suggest that the new product shows potential for promoting long-term remineralization leading to the inhibition of caries and protection of dental structures.

Effect of Calcination Temperature on the Phase Composition, Morphology, and Thermal Properties of ZrO2 and Al2O3 Modified with APTES (3-aminopropyltriethoxysilane)

This paper describes the effect of calcination temperature on the phase composition, chemical composition, and morphology of ZrO₂ and Al₂O₃ powders modified with 3-aminopropyltriethoxysilane (APTES). Both ceramic powders were modified by etching in piranha solution, neutralization in ammonia water, reaction with APTES, ultrasonication, and finally calcination at 250, 350, or 450 °C. The obtained modified powders were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, particle size distribution (PSD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDS), and thermogravimetric analysis (TGA).

Fabrication and characterization of low-shrinkage dental composites containing montmorillonite nanoclay

Dental composites are aesthetic materials widely used in Dentistry for replacing hard dental tissues lost due to caries or traumas. The aim of this study was to fabricate low-shrinkage dental composite charged with nanoclay fillers (montmorillonite Cloisite®-MMT) and evaluate their cytotoxicity and physicomechanical properties. Four dental composites were produced from the same organic matrix: Bis-GMA/TEGDMA (30 wt.%). The filler system was constituted of BaSi, SiO₂, and MMT in the following concentrations (wt.%): 93.8/6.2/0, 89.1/5.9/5, 86.7/5.8/7.5, and 84.4/5.6/10 (E₀: 0; E₅: 5%; E_7.5: 7.5%; E₁₀: 10% of MMT nanoclays). The following properties were tested: in vitro cytotoxicity, flexural strength, elastic modulus, volumetric shrinkage, water sorption, water solubility, and hygroscopic expansion. Scanning electron microscopy was used to characterize composites' topography. Data were analyzed by one-way ANOVA and Tukey's HSD post hoc test (p < 0.05). MMT nanoclays did not affect the cytotoxicity. E₅ and E_7.5 groups showed a significant decrease in polymerization shrinkage while maintained the overall physicomechanical properties. The inclusion of 5 and 7.5 wt.% of MMT nanoclays allowed the fabrication of dental composites with low cytotoxicity and low polymerization shrinkage, without jeopardizing the overall behaviour of their physicomechanical properties (flexural strength, elastic modulus, water sorption, water solubility, and hygroscopic expansion). These aspects suggest that the usage of MMT nanoclays could be an effective strategy to formulate new dental composites with clinical applicability.

Fabrication and characterization of remineralizing dental composites containing calcium type pre-reacted glass-ionomer (PRG-Ca) fillers

OBJECTIVE

To fabricate and characterize dental composites with calcium type pre-reacted glass-ionomer (PRG-Ca) fillers.

METHODS

PRG-Ca fillers were prepared by the reaction of calcium fluoroaluminosilicate glass with polyacrylic acid. Seven dental composites were produced from the same organic matrix (70/30wt% Bis-GMA/TEGDMA), with partial replacement of barium borosilicate (BaBSi) fillers (60wt%) by PRG-Ca fillers (wt%): E0 (0) - control, E1 (10), E2 (20), E3 (30), E4 (40), E5 (50) and E6 (60). Enamel remineralization was evaluated in caries-like enamel lesions induced by S. mutans biofilm using micro-CT. The following properties were characterized: degree of conversion (DC%), roughness (Ra), Knoop hardness (KHN), flexural strength (FS), flexural modulus (FM), water sorption (W_sp), water solubility (W_sl), and translucency (TP). Data were analyzed to one-way ANOVA and Tukey's HSD test (α=0.05).

RESULTS

All composites with PRG-Ca induced enamel remineralization. E0 and E1 presented similar and highest DC% than E2=E3=E4=E5=E6. Ra and KHN were not influenced by PRG-Ca fillers (p<0.05). The higher the content of PRG-Ca, the lower FS, FM and TP (p<0.05). W_sp increased linearly with the content of PRG-Ca fillers (p<0.05). E6 presented the highest W_sl (p<0.05), while the W_sl of the other composites were not different from each other (p>0.05).

SIGNIFICANCE

Incorporation of 10-40wt.% of PRG-Ca fillers endowed remineralizing potential to dental composites without jeopardizing the overall behavior of their physicochemical properties. Dental composites with PRG-Ca fillers seems to be a good alternative for reinforcing the enamel against caries development.

Effect of co-precipitation plus spray-drying of nano-CaF2 on mechanical and fluoride properties of nanocomposite

OBJECTIVE

Fluoride (F)-releasing restoratives typically are either weak mechanically or release only low levels of F ions. The objectives of this study were to: (1) develop a novel photo-cured nanocomposite with strong mechanical properties and high levels of sustained F ion release via a two-step "co-precipitation + spray-drying" technique to synthesize CaF₂ nanoparticles (nCaF₂); and (2) investigate the effect of spray-drying treatment after co-precipitation of nCaF₂ on mechanical properties and F ion release of composite.

METHODS

Two types of CaF₂ particles were synthesized: A co-precipitation method yielded CaF₂cp; "co-precipitation + spray-drying" yielded nCaF₂cpsd. Composites were fabricated with fillers of: (1) 0% CaF₂ + 70% glass; (2) 10% CaF₂cp + 60% glass; (3) 15% CaF₂cp + 55% glass; (4) 20% CaF₂cp + 50% glass; (5) 10% nCaF₂cpsd + 60% glass; (6) 15% nCaF₂cpsd + 55% glass; and (7) 20% nCaF₂cpsd + 50% glass. A commercial F-releasing nanocomposite served as control.

RESULTS

The nCaF₂cpsd had much smaller particle size (median = 32 nm) and narrower distribution (22-57 nm) than CaF₂cp (median = 5.25 μm, 162 nm-67 μm). The composite containing nCaF₂cpsd had greater flowability, flexural strength, elastic modulus and hardness than CaF₂cp composite and commercial control composite. At 84-day immersion in water, the nanocomposites containing 20% nCaF₂cpsd had 65 times higher cumulative F release, and 77 times greater long-term F-release rate, than commercial control.

CONCLUSIONS

A novel two-step "co-precipitation + spray-drying" technique of synthesizing nCaF₂ was developed. The photo-cured nanocomposite containing 20% nCaF₂cpsd possessed strong mechanical properties and excellent long-term F-release ability, and hence is promising for dental restoration applications to inhibit secondary caries.

Functional fillers for dental resin composites

Dental resin composites (DRCs) are popular materials to repair caries. Although various types of DRCs with different characteristics have been developed, restoration failures still exist. Bulk fracture and secondary caries have been considered as main causes for the failure of composites restoration. To address these problems, various fillers with specific functions have been introduced and studied. Some fillers with specific morphologies such as whisker, fiber, and nanotube, have been used to increase the mechanical properties of DRCs, and other fillers releasing ions such as Ag⁺, Ca²⁺, and F^-, have been used to inhibit the secondary caries. These functional fillers are helpful to improve the performances and lifespan of DRCs. In this article, we firstly introduce the composition and development of DRCs, then review and discuss the functional fillers classified according to their roles in the DRCs, finally give a summary on the current research and predict the trend of future development.

Fabrication and characterization of remineralizing dental composites containing hydroxyapatite nanoparticles

The aim of this study was to fabricate and characterize dental composites containing hydroxyapatite nanoparticles (HApNPs). Four dental composites were produced from the same organic matrix (70 wt% Bis-GMA and 30 wt% TEGDMA), with partial replacement of BaBSi particles (65 wt%) by HApNPs in the following concentrations (wt%): E0 (0) - control, E10 (10), E20 (20) and E30 (30). Ca²⁺ and PO₄^3- release was evaluated in solutions with different pHs (4, 5.5, and 7) using atomic emission spectroscopy with microwave-induced nitrogen plasma while the enamel remineralization potential was evaluated in caries-like enamel lesions induced by S. mutans biofilm using micro-CT. The following properties were characterized: degree of conversion (DC%), microhardness (KHN), flexural strength (FS), elastic modulus (EM) and translucency (TP). The higher the HApNPs content, the higher the Ca²⁺ and PO₄^3- release. The ions release was influenced by pH (4 > 5.5 > 7) (p < 0.05). All composites loaded with HApNPs were able to remineralize the enamel (E30 = E20 > E10) (p < 0.05). Contrarily, E0 was not able of recovering the enamel mineral loss. E0 and E10 presented highest DC%, while E20 and E30 showed similar and lowest DC%. KHN and FS were decreased with the addition of HApNPs, while EM was not influenced by the incorporation of HApNPs. E10 presented statistically similar TP to E0, while this property decreased for E20 and E30 (p < 0.05). Incorporation of HApNPs into dental composites promoted enamel remineralization, mainly at potentially cariogenic pH (= 4), while maintained their overall performance in terms of physicomechanical properties.