Mechanical and antibacterial properties of benzothiazole-based dental resin materials

Evaluation of photopolymer resins for dental prosthetics fabricated via the stereolithography process at different polymerization temperatures-Part I: Conversion rate and mechanical properties

STATEMENT OF PROBLEM

Improvement in the mechanical properties of 3-dimensional (3D) printed dental prostheses is necessary to prevent wear caused by an antagonist or fracture. However, how different printing temperatures affect their mechanical properties is unclear.

PURPOSE

The purpose of this in vitro study was to evaluate the mechanical properties of 3D printed parts fabricated at different printing temperatures.

MATERIAL AND METHODS

Photopolymer specimens were fabricated at 3 different temperatures (room temperature, 50 °C, and 70 °C) using a stereolithography 3D printer. After rinsing to remove the residual monomer, the specimens were divided into 2 groups: with or without postprocessing. The viscosity of the photopolymerization resin was measured while the temperature was increased. Furthermore, the double-bond conversion (DBC) of the printed part was evaluated (n=3). Mechanical properties were investigated via dynamic mechanical analysis (n=1) and tensile testing (n=5). Statistical comparisons were performed via 1-way analysis of variance, followed by the Tukey honestly significant difference test (α=.05).

RESULTS

The DBC rates of the green condition group increased from 66.67% to 86.33% with increasing temperature. In addition, these specimens exhibited improved mechanical properties and reduced residual monomer levels.

CONCLUSIONS

Specimens fabricated at a temperature of 70 °C exhibited mechanical properties suitable for clinical application.

Tailoring the monomers to overcome the shortcomings of current dental resin composites - review

Dental resin composites (DRCs) have become the first choice among different restorative materials for direct anterior and posterior restorations in the clinic. Though the properties of DRCs have been improved greatly in recent years, they still have several shortcomings, such as volumetric shrinkage and shrinkage stress, biofilm development, lack of radio-opacity for some specific DRCs, and estrogenicity, which need to be overcome. The resin matrix, composed of different monomers, constitutes the continuous phase and determine the performance of DRCs. Thus, the chemical structure of the monomers plays an important role in modifying the properties of DRCs. Numerous researchers have taken to design and develop novel monomers with specific functions for the purpose of fulfilling the needs in dentistry. In this review, the development of monomers in DRCs were highlighted, especially focusing on strategies aimed at reducing volumetric shrinkage and shrinkage stress, endowing bacteriocidal and antibacterial adhesion activities as well as protein-repelling activity, increasing radio-opacity, and replacing Bis-GMA. The influences of these novel monomers on the properties of DRCs were also discussed.

Antibacterial dental resin composites (DRCs) with synthesized bis-quaternary ammonium monomethacrylates as antibacterial agents

Three bi-quaternary ammonium methacrylates (biQAMA-12, biQAMA-14, and biQAMA-16) with different alkyl chain length were synthesized with the purpose of endowing dental resin composites (DRCs) with antibacterial activity without sacrificing physicochemical properties of DRCs. All of biQAMAs were confirmed by ¹H-NMR spectra and incorporated into Bis-GMA/TEGDMA (60 wt/40 wt) resin matrix with a mass fraction of 5 wt% as antibacterial agent. The obtained resin matrixes were mixed with commercial silaned glass fillers at a mass ratio of 30 wt/70 wt to prepare antibacterial DRCs. The double bond conversion (DC), antibacterial activity against S. mutans., surface charge density, water contact angle, water sorption (WS) and solubility (SL), mechanical properties, and cytotoxicity of biQAMAs containing DRCs were investigated. The DRC without biQAMAs was used as control. The results showed that all biQAMAs containing DRCs had antibacterial rate higher than 90%, and DRC with biQAMA-12 had the highest antibacterial rate due to its highest surface charge density. Adding 5 wt% of biQAMAs would not bring out negative effect on physicochemical properties of DRCs, except for increasing WS, but the resultant WS still met the ISO requirement on WS of restorative materials. Both biQAMA-14 and biQAMA-16 containing DRCs showed higher cytotoxicity than control, thus biQAMA-12 was considered as the optimal antibacterial agent in this research.

Preparation of antibacterial acrylic bone cement with methacrylate derived from benzothiazole

Methacrylate derived from benzothiazole (BTTMA) was incorporated into acrylic bone cement with a series of mass ratio (5 wt%, 10 wt%, and 15 wt%) with the aim to endow antibacterial activity. Properties such as dough time (t_dough), setting time (t_set), maximum temperature (T_peak), fluid uptake, water solubility, mechanical properties, and biocompatibility of BTTMA containing bone cements were all investigated. Bone cement without BTTMA was used as control and named as plain cement. The results showed that, after incorporating BTTMA, t_dough, flexural modulus, compressive strength of bone cements could be increased, while t_set, T_peak, fluid uptake, water solubility, and flexural strength would be reduced. All of BTTMA containing bone cements did not show hemolytic activity and cell toxicity, but only bone cement with 15 wt% of BTTMA showed antibacterial activity against Staphylococcus aureus (S. aureus).

The Azoles in Pharmacochemistry: Perspectives on the Synthesis of New Compounds and Chemoinformatic Contributions

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Due to their versatile biological activity, Azoles are widely studied in pharmacochemistry. It is possible to use them in many applications and in studies aimed at discovering antiparasitic, antineoplastic, antiviral, antimicrobial compounds; and in the production of materials for treatment of varied pathologies. Based on their biological activity, our review presents several studies that involve this class of organic compounds. A bibliographic survey of this type can effectively contribute to pharmaceutical sciences, stimulating the discovery of new compounds, and structural improvements to biological profiles of interest. In this review, articles are discussed involving the synthesis of new compounds and chemoinformatic contributions. Current applications of azoles in both the pharmaceutical and agri-business sectors are well known, yet as this research highlights, azole compounds can also bring important contributions to the fight against many diseases. Among the heterocyclics, azoles are increasingly studied by research groups around the world for application against tuberculosis, HIV, fungal and bacterial infections; and against parasites such as leishmaniasis and trypanosomiasis. Our hope is that this work will help arouse the interest of research groups planning to develop new bioactives to fight against these and other diseases.

Antibacterial and thermomechanical properties of experimental dental resins containing quaternary ammonium monomers with two or four methacrylate groups

Resins with strong antibacterial and thermomechanical properties are critical for application in oral cavities. In this study, we first evaluated the antibacterial effect of an unfilled resin incorporating 1, 4, and 7 mass% of quaternary ammonium salt (QAS) monomers containing two methacrylate groups (MAE-DB) and four methacrylate groups (TMH-DB) against Streptococcus mutans, and tested the cytotoxicity and thermomechanical properties of the 4 mass% MAE-DB and TMH-DB modified resin materials. A neat resin without a QAS monomer served as the control. As the concentration of both QAS monomers increases, the formation of a Streptococcus mutans biofilm on the experimental material is increasingly inhibited. The results of colony forming unit counts and the metabolic activity showed that both the MAE-DB and TMH-DB modified resins have a strong bactericidal effect on the bacteria in a biofilm, but no bactericidal effect on the bacteria in a solution. The viability-staining and morphology results also demonstrate that the bacteria deform, lyse, shrink, and die on the surface of the two QAS-modified resins. Cytotoxicity results show that the addition of TMH-DB can reduce the cytotoxicity of the resin, while the addition of MAE-DB increases the cytotoxicity of the resin. DMA results show that a TMH-DB modified resin has a higher storage modulus than a MAE-DB modified resin owing to its better crosslink density. The two groups of experimental resins showed a similar glass transition temperature. These data indicate that the two QAS monomers can impart similar antibacterial properties upon contact with a dental resin, whereas TMH-DB can endow the resin with a higher crosslink density and storage modulus than MAE-DB because it has more polymerizable groups.

Resins with strong antibacterial and thermomechanical properties are critical for application in oral cavities.

Synthesis of antibacterial dimethacrylate derived from niacin and its application in preparing antibacterial dental resin system

In this research, a bio-based monomer 1,3-bis(methacryloyloxy)propyl-carbonyl- hexylpyridinium bromide (QANMA) that derived from niacin was synthesized and incorporated into Bisphenol A glycidyl methacrylate (Bis-GMA)/triethylene glycol dimethacrylate (TEGDMA) (50 wt/50 wt) with a series of mass fraction as antibacterial agent. The double bond conversion (DC), volumetric shrinkage (VS), mechanical properties, water sorption (WS) and solubility (SL) were investigated among groups with different QANMA concentrations. Antibacterial activity against S. mutans were conducted by bacteria colony counting and bacteria LIVE/DEAD staining. The results showed that QANMA had no influence on DC of dental resin (p > 0.05), but would lead to lower volumetric shrinkage (p < 0.05). Only dental resin with 10 wt% and 20 wt% of QANMA showed obviously antibacterial activity. Mechanical properties, WS and SL of dental resin could be impaired by incorporation QANMA, flexural strength and modulus were decreased with the increasing of QANMA concentration (p < 0.05), while WS and SL were increased with the increasing of QANMA concentration (p < 0.05). Dental resin with 10 wt% of QANMA seemed to be the optimal resin system in this research, for it showed significant antibacterial activity and its flexural strength was still met the requirement of ISO standard. This work suggested that bio-based monomer QANMA could be used as antibacterial agent in dental materials, but further optimization experiment and biocompatibility evaluation should be taken in future.