Poly(methyl methacralyate) (PMMA) has long been used in dentistry as a base polymer for dentures, and it is recently being used for the 3D printing of dental materials. Despite its many advantages, its susceptibility to microbial colonization remains to be overcome. In this study, the interface between 3D-printed PMMA specimens and oral salivary biofilm was studied following the addition of zwitterionic materials, 2-methacryloyloxyethyl phosphorylcholine (MPC) or sulfobetaine methacrylate (SB). A significant reduction in bacterial and biofilm adhesions was observed following the addition of MPC or SB, owing to their protein-repellent properties, and there were no significant differences between the two test materials. Although the mechanical properties of the tested materials were degraded, the statistical value of the reduction was minimal and all the properties fulfilled the requirements set by the International Standard, ISO 20795-2. Additionally, both the test materials maintained their resistance to biofilm when subjected to hydrothermal fatigue, with no further deterioration of the mechanical properties. Thus, novel 3D-printable PMMA incorporated with MPC or SB shows durable oral salivary biofilm resistance with maintenance of the physical and mechanical properties.

The aim of this study is to investigate the resistance of various fluoride-releasing restorative materials against the demineralization and remineralization of enamel surfaces, including those that have been recently introduced to the market. Three different fluoride-releasing restorative materials were considered: glass ionomer (FI), resin-modified glass ionomer (RL), and an alkasite restorative material (CN). The acid neutralization ability was investigated using pH measurement, and the concentrations of released fluoride and calcium ions were measured. Finally, the demineralization resistance and remineralization effects of enamel were observed using a microhardness tester and SEM. CN showed an initial substantial increase in pH followed by a steady increase, with values higher than those of the other groups (p < 0.05). All three groups released fluoride ions, and the CN group released more calcium ions than the other groups (p < 0.05). In the acid resistance test, from the microhardness and SEM images, the CN group showed effective resistance to demineralization. In the remineralization test, the microhardness results showed that the FI and CN groups recovered the microhardness from the values of the demineralized enamel surface (p < 0.05). This was confirmed by the SEM images from remineralization tests; the CN group showed a recovered demineralized surface when immersed in artificial saliva for 7 days. In conclusion, alkasite restorative material can be an effective material when used in cariogenic environments.

Flowable resins used for dental restoration are subject to biofilm formation. Zinc has antibacterial properties. Thus, we prepared a zinc-doped phosphate-based glass (Zn-PBG) to dope a flowable resin and evaluated the antibacterial activity of the composite against Streptococcus mutans (S. mutans) to extrapolate the preventative effect toward secondary caries. The composites were prepared having 0 (control), 1.9, 3.8, and 5.4 wt.% Zn-PBG. The flexural strength, elastic modulus, microhardness, depth of cure, ion release, inhibition zone size, and number of colony-forming units were evaluated and analyzed using ANOVA. The flexural strength of the control was significantly higher than those of Zn-PBG samples (p < 0.05). However, all samples meet the International Standard, ISO 4049. The microhardness was not significantly different for the control group and 1.9 and 3.8 wt.% groups, but the 5.4 wt.% Zn-PBG group had a significantly lower microhardness (p < 0.05). Further, the composite resins increasingly released P, Ca, Na, and Zn ions with an increase in Zn-PBG content (p < 0.05). The colony-forming unit count revealed a significant reduction in S. mutans viability (p < 0.05) with increase in Zn-PBG content. Therefore, the addition of Zn-PBG to flowable composite resins enhances antibacterial activity and could aid the prevention of secondary caries.

Since pits and fissures are the areas most commonly affected by caries due to their structural irregularity, bioactive resin-based sealant (RBS) may contribute to the prevention of secondary caries. This study aims to investigate the mechanical, physical, ion-release, enamel remineralisation, and antibacterial capabilities of the novel RBS with bioactive glass (BAG) and 2-methacryloyloxyethyl phosphorylcholine (MPC). For the synthesis, 12.5 wt% BAG and 3 wt% MPC were incorporated into RBS. The contact angle, flexural strength, water sorption, solubility, and viscosity were investigated. The release of multiple ions relating to enamel remineralisation was investigated. Further, the attachments of bovine serum albumin, brain heart infusion broth, and Streptococcus mutans on RBS were studied. Finally, the thickness and biomass of a human saliva-derived microsm biofilm model were analysed before aging, with static immersion aging and with thermocycling aging. In comparison to commercial RBS, BAG+MPC increased the wettability, water sorption, solubility, viscosity, and release of multiple ions, while the flexural strength did not significantly differ. Furthermore, RBS with MPC and BAG+MPC significantly reduced protein and bacteria adhesion and suppressed multi-species biofilm attachment regardless of the existence of aging and its type. The novel RBS has great potential to facilitate enamel remineralisation and suppress biofilm adhesion, which could prevent secondary dental caries.

We aimed to evaluate the antimicrobial effects of Glycyrrhiza uralensis extract on Streptococcus mutans and Candida albicans and its biocompatibility for dental applications. The antimicrobial activity of the G. uralensis extracts at concentrations of 50, 100, 150, and 200 µg/mL was assessed using agar disk diffusion tests, counting the total number of colony-forming units (CFUs), spectrophotometric growth inhibitory assays, and microbial morphology observations using scanning electron microscopy (SEM; Merin, Carl Zeiss, Oberkochen, Germany). We measured the polyphenol and flavonoid contents of G. uralensis extracts using ultraviolet–visible spectrometry and the cytotoxicity of these extracts using an MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. We identified that G. uralensis extracts had significant antimicrobial effects against S. mutans and C. albicans. The optical density of the experimental groups significantly decreased compared with that of the control group. SEM images revealed that the G. uralensis extract affected the morphology and density of S. mutans and C. albicans. The extract concentration of flavonoids, but not polyphenols, increased with increasing concentrations of the G. uralensis extract. Furthermore, cell viabilities were more than 70% for G. uralensis extracts with concentrations of 50 and 100 μg/mL. Naturally derived G. uralensis is biocompatible and exhibits an excellent antimicrobial effect against oral pathogens such as S. mutans and C. albicans. Thus, G. uralensis extracts can be used for the development of oral products that treat and prevent oral diseases.

Gelatin, a natural polymer, provides excellent tissue compatibility for use in tissue rehabilitation. Bioactive glasses (BAG) offer superior capacity in stimulating a bioactive response but show high variability in uptake and solubility. To tackle these drawbacks, a combination of gelatin with BAG is proposed to form composites, which then offer a synergistic response. The cross-linked gelatin structure’s mechanical properties are enhanced by the incorporation of the inorganic BAG, and the rate of BAG ionic supplementation responsible for bioactivity and regenerative potential is better controlled by a protective gelatin layer. Several studies have demonstrated the cellular benefits of these composites in different forms of functional modification such as doping with zinc or incorporation of zinc such as ions directly into the BAG matrix. This review presents a comprehensive perspective on the individual characteristics of BAG and gelatin, including the synthesis and mechanism of action. Further, adaptation of the composite into various applications for bone tissue engineering is discussed and future challenges are highlighted.