Human In Situ Study of the effect of Bis(2-Methacryloyloxyethyl) Dimethylammonium Bromide Immobilized in Dental Composite on Controlling Mature Cariogenic Biofilm

The germicidal effect, biosafety and mechanical properties of antibacterial resin composite in cavity filling

In recent years, dental resin materials have become increasingly popular for cavity filling. However, these materials can shrink during polymerization, leading to microleakages that enable bacteria to erode tooth tissue and cause secondary caries. As a result, there is great clinical demand for the development of antibacterial resins. The principle of antibacterial resin includes contact killing and filler-release killing of bacteria. For contact killing, quaternary ammonium salts (QACs) and antibacterial peptides (AMPs) can be added. For filler-release killing, chlorhexidine (CHX) and nanoparticles are used. These antibacterial agents are effective against gram-positive bacteria, gram-negative bacteria, fungi, and more. Among them, QACs has a lasting antibacterial effect, and silver nanoparticles even have a certain ability to kill viruses. Biocompatibility-wise, QACs, AMPs, and CHX have low cytotoxicity to cells when added into the resin. However, nanoparticles with smaller particle sizes have higher cytotoxicity. In terms of mechanical properties, QACs, AMPs, and CHX do not negatively affect the resin. However, the addition of magnesium oxide can have a negative impact. This paper reviews the types and antibacterial principles of commonly used antibacterial resins in recent years, evaluates their antibacterial effect, biological safety, and mechanical properties, and provides references for selecting clinical filling materials.

Novel Rechargeable Nanostructured Calcium Phosphate Crown Cement with Long-Term Ion Release and Antibacterial Activity to Suppress Saliva Microcosm Biofilms

OBJECTIVE

Resin cements with remineralizing and antibacterial properties are favorable for inhibition of caries. The objectives of this study were: (1) to investigate the capability of the novel dimethylaminohexadecyl-methacrylate (DMAHDM) and nano-sized amorphous calcium phosphate (NACP) containing cement to reduce saliva microcosm biofilm, and (2) to investigate the long-term ion release, recharge, and re-release of DMAHDM-NACP cement.

METHODS

Pyromellitic glycerol dimethacrylate (PMGDM) and ethoxylated bisphenol-A-dimethacrylate (EBPADMA) were used to make PEHB monomer. Five cements were fabricated: (1) PEHB+0%NACP+0%DMAHDM (experimental control); (2) PEHB+25%NACP+0%DMAHDM, (3) PEHB+25%NACP+0%DMAHDM; (4) PEHB+25%NACP+3%DMAHDM; (5) PEHB+25%NACP+5%DMAHDM. RelyX luting cement was used as commercial control. Colony-forming units (CFU), lactic acid production, metabolic activities, and minimum inhibitory concentration (MIC) were performed. Long-term Calcium (Ca) and phosphate (P) ion release, recharge, and re-release were assessed.

RESULTS

Compared to experimental and commercial controls, the NACP-DMAHDM cement significantly reduced CFU biofilm by 2-3 orders of magnitude, metabolic activities from 0.24±0.06 A₅₄₀/cm² to 0.03±0.01 A₅₄₀/cm², and lactic acid production from 27.7±2.5 mmol/L to 5.4±2.1 mmol/L (n=6) (p<0.05). The DMAHDM showed an MIC value of 0.03 mg/L. However, when the DMAHDM was combined with PMGDM monomer, the MIC was greater than DMAHDM alone. The ion concentrations for the experimental groups significantly increased over time (1-84 days), indicating continuous ion release (n=3) (p<0.05). Increasing the DMAHDM mass fraction from 0% to 5% and 3% to 5% significantly enhanced ion recharge and re-release at the third cycle (p<0.05).

CONCLUSIONS

Incorporating DMAHDM and NACP into resin-based crown cement provides strong antibacterial action against saliva microcosm biofilm and presents a high level of Ca and P ion recharge abilities, exhibiting long-term Ca and P ion release and remineralization potential.

CLINICAL SIGNIFICANCE

Resin based cement containing NACP and DMAHDM were developed with remineralizing and potent antibacterial effects. This cement formulation showed ion release and remineralization potential and are promising formulations to inhibit the incidence of recurrent caries and could promote remineralization and be sustainable for the long term.

Strategies toward development of antimicrobial biomaterials for dental healthcare applications

Several approaches for elimination of oral pathogens are being explored at the present time since oral diseases remain prevalent affecting approximately 3.5 billion people worldwide. Need for antimicrobial biomaterials in dental healthcare include but is not restricted to designing resin composites and adhesives for prevention of dental caries. Constant efforts are also being made to develop antimicrobial strategies for clearance of endodontic space prior root canal treatment and for treatment of periimplantitis and periodontitis. This article discusses various conventional and nanotechnology-based strategies to achieve antimicrobial efficacy in dental biomaterials. Recent developments in the design and synthesis of antimicrobial peptides and antifouling zwitterionic polymers to effectively lessen the risks of antimicrobial drug resistance are also outlined in this review. Further, the role of contemporary strategies such as use of smart biomaterials, ionic solvent-based biomaterials and quorum quenchers incorporated biomaterials in the elimination of dental pathogens are described in detail. Lastly, we mentioned the approach of using polymers to print custom-made three-dimensional antibacterial dental products via additive manufacturing technologies. This review provides a critical perspective on the chemical, biomimetic, and engineering strategies intended for developing antimicrobial biomaterials that have the potential to substantially improve the dental health.

A Review of Mechano-Biochemical Models for Testing Composite Restorations

Due to the severe mechano-biochemical conditions in the oral cavity, many dental restorations will degrade and eventually fail. For teeth restored with resin composite, the major modes of failure are secondary caries and fracture of the tooth or restoration. While clinical studies can answer some of the more practical questions, such as the rate of failure, fundamental understanding on the failure mechanism can be obtained from laboratory studies using simplified models more effectively. Reviewed in this article are the 4 main types of models used to study the degradation of resin-composite restorations, namely, animal, human in vivo or in situ, in vitro biofilm, and in vitro chemical models. The characteristics, advantages, and disadvantages of these models are discussed and compared. The tooth-restoration interface is widely considered the weakest link in a resin composite restoration. To account for the different types of degradation that can occur (i.e., demineralization, resin hydrolysis, and collagen degradation), enzymes such as esterase and collagenase found in the oral environment are used, in addition to acids, to form biochemical models to test resin-composite restorations in conjunction with mechanical loading. Furthermore, laboratory tests are usually performed in an accelerated manner to save time. It is argued that, for an accelerated multicomponent model to be representative and predictive in terms of both the mode and the speed of degradation, the individual components must be synchronized in their rates of action and be calibrated with clinical data. The process of calibrating the in vitro models against clinical data is briefly described. To achieve representative and predictive in vitro models, more comparative studies of in vivo and in vitro models are required to calibrate the laboratory studies.

Synthesis of Novel Dental Nanocomposite Resins by Incorporating Polymerizable, Quaternary Ammonium Silane-Modified Silica Nanoparticles

Diverse approaches dealing with the reinforcement of dental composite resins with quaternary ammonium compounds (QAC) have been previously reported. This work aims to investigate the physicochemical and mechanical performance of dental resins containing silica nanofillers with novel QAC. Different types of quaternary ammonium silane compounds (QASiC) were initially synthesized and characterized with proton nuclear magnetic resonance (¹H-NMR) and Fourier transform infrared (FTIR) spectroscopy. Silica nanoparticles were surface modified with the above QASiC and the structure of silanized products (S.QASiC) was confirmed by means of FTIR and thermogravimetric analysis. The obtained S.QASiC were then incorporated into methacrylate based dental resins. Scanning electron microscopy images revealed a satisfactory dispersion of silica nanoclusters for most of the synthesized nanocomposites. Curing kinetics disclosed a rise in both the autoacceleration effect and degree of conversion mainly induced by shorter QASiC molecules. Polymerization shrinkage was found to be influenced by the particular type of S.QASiC. The flexural modulus and strength of composites were increased by 74% and 19%, while their compressive strength enhancement reached up to 19% by adding 22 wt% S.QASiC nanoparticles. These findings might contribute to the proper design of multifunctional dental materials able to meet the contemporary challenges in clinical practice.

Sustained Antibacterial Effect and Wear Behavior of Quaternary Ammonium Contact-Killing Dental Polymers after One-Year of Hydrolytic Degradation

This study intended to investigate the long-term antibacterial effect, mechanical performance, and surface topography of new anticaries dental composites. While most artificial aging studies of dental resins lasted for 30–90 days, this study prolonged the water-aging to one year to be more clinically relevant. The base resin was loaded with dimethylaminohexadecyl methacrylate (DMAHDM) at 3 or 5 wt.% and nano-sized amorphous calcium phosphate (NACP) at 20 wt.%. Composites were subjected to one-year water storage and wear. Following water aging, samples were evaluated for flexural strength, elastic modulus, and microbiological assays. Biofilm plate counting method, metabolic assay, colorimetric quantification of lactic acid, and Baclight bacterial viability assay were measured after one year. Topography changes (ΔRa, ΔRq, ΔRv, ΔRt) were examined after wear and observed by scanning electron microscopy. Biofilm assays and topography changes data were analyzed via one-way ANOVA and Tukey’s tests. Mechanical properties and normalized data were verified using a t-test. The flexural strength values for the formulations that contained 5% DMAHDM-20% NACP, 3% DMAHDM, and 5% DMAHDM were reduced significantly (p < 0.05) in relation to the baseline but the values were still above the ISO standards. No significant differences were observed between the groups concerning the topography changes, except for the ΔRt, where there was a significant increase in the 5% DMAHDM-20% NACP group. All the groups demonstrated robust biofilm-inhibition, with slightly reduced antibacterial properties following water aging. The aged samples reduced the total microorganisms, total streptococci, and mutans streptococci by 1.5 to 3-log, compared to the experimental control. The new formulations containing DMAHDM and NACP were able to sustain the antibacterial performance after one-year of aging. Mechanical properties and surface topography were slightly affected over time.

Bibliometric Analysis of Literature Published on Antibacterial Dental Adhesive from 1996-2020

This study aimed to investigate the current state of research on antibacterial dental adhesives. The interest in this field can be drawn from an increasing number of scholarly works in this area. However, there is still a lack of quantitative measurement of this topic. The main aim of this study was to consolidate the research published on the antibacterial adhesive from 1996 to 2020 in Web of Science indexed journals. The bibliometric method, a quantitative study of investigating publishing trends and patterns, was used for this study. The result has shown that a gradual increase in research was found, whereby a substantial increase was observed from 2013. A total of 248 documents were published in 84 journals with total citations of 5107. The highly cited articles were published mainly in Q1 category journals. Most of the published articles were from the USA, China, and other developed countries; however, some developing countries contributed as well. The authorship pattern showed an interdisciplinary and collaborative approach among researchers. The thematic evaluation of keywords along with a three-factor analysis showed that 'antibacterial adhesives' and 'quaternary ammonium' have been used commonly. This bibliometric analysis can provide direction not only to researchers but also to funding organizations and policymakers.

Emerging Contact-Killing Antibacterial Strategies for Developing Anti-Biofilm Dental Polymeric Restorative Materials

Polymeric materials are the first choice for restoring tooth cavities, bonding tooth-colored fillings, sealing root canal systems, and many other dental restorative applications. However, polymeric materials are highly susceptible to bacterial attachment and colonization, leading to dental diseases. Many approaches have been investigated to minimize the formation of biofilms over polymeric restorative materials and at the tooth/material interfaces. Among them, contact-killing compounds have shown promising results to inhibit dental biofilms. Contact-killing compounds can be immobilized within the polymer structure, delivering a long-lasting effect with no leaching or release, thus providing advantages compared to release-based materials. This review discusses cutting-edge research on the development of contact-killing compounds in dental restorative materials to target oral pathogens. Contact-killing compounds in resin composite restorations, dental adhesives, root canal sealers, denture-based materials, and crown cements have all demonstrated promising antibacterial properties. Contact-killing restorative materials have been found to effectively inhibit the growth and activities of several oral pathogens related to dental caries, periodontal diseases, endodontic, and fungal infections. Further laboratory optimization and clinical trials using translational models are needed to confirm the clinical applicability of this new generation of contact-killing dental restorative materials.

In vivo Microbial Diversity Analysis on Different Surfaces of Dental Restorative Materials via 16S rDNA Sequencing

Background

This study aimed to provide precise material selection guidance for proper clinical restoration and treatment of plaque-related oral diseases, such as dental caries and periodontal diseases.

Material/Methods

Four groups (n=24) of restorative material sheets (n=24) were prepared using 3M Z350 composite resin (ZR), zinc phosphate cement (ZPC), glass-ionomer (GI), and ICON permeable resin (IPR). Six volunteers wore a plaque-collection device equipped with the 4 restorative material sheets for 48 hours. Plaque samples were collected, and Miseq sequencing was applied to obtain template DNA fragments for microbial diversity analysis. The data were analyzed with nonparametric tests.

Results

The microbial diversity on the ZPC surface was significantly lower than that on GI and IPR surfaces. The abundance of Firmicutes and Streptococcus on the ZPC surface was significantly higher than on the surfaces of GI and IPR. In contrast, the abundance of Porphyromonas on the surface of ZPC was significantly lower than that on GI and IPR surfaces. (P<0.05).

Conclusions

The results of the present study might serve as a basis for material selection under different oral microbial conditions to provide more accurate treatments and restorative procedures in the oral cavity.

Nanoparticulate drug-delivery systems for fighting microbial biofilms: from bench to bedside

Biofilms are highly tolerant to antimicrobial agents and adverse environmental conditions being important reservoirs for chronic and hard-to-treat infections. Nanomaterials exhibit microbiostatic/microbicidal/antipathogenic properties and can be also used for the delivery of antibiofilm agents. However, few of the many promising leads offered by nanotechnology reach clinical studies and eventually, become available to clinicians. The aim of this paper was to review the progress and challenges in the development of nanotechnology-based antibiofilm drug-delivery systems. The main identified challenges are: most papers report only in vitro studies of the activity of different nanoformulations; lack of standardization in the methodological approaches; insufficient collaboration between material science specialists and clinicians; paucity of in vivo studies to test efficiency and safety.