Development of novel self-healing and antibacterial dental composite containing calcium phosphate nanoparticles

A Historical Perspective on Dental Composite Restorative Materials

This review article will discuss the origin of resin-based dental composite materials and their adoption as potentially useful adjuncts to the primary material used by most dentists for direct restorations. The evolution of the materials, largely driven by the industry's response to the needs of dentists, has produced materials that are esthetic, strong, and versatile enough to be used in most areas of the oral cavity to replace or restore missing tooth structures. Significant advancements, such as the transition from chemical to light-curing materials, refinements in reinforcing particles to produce optimum polishing and wear resistance, formulating pastes with altered viscosities to create highly flowable and highly stiff materials, and creating materials with enhanced depth of cure to facilitate placement, will be highlighted. Future advancements will likely reflect the movement away from simply being a biocompatible material to one that is designed to produce some type of beneficial effect upon interaction within the oral environment. These new materials have been called "bioactive" by virtue of their potential effects on bacterial biofilms and their ability to promote mineralization of adjacent tooth structures.

A Review on the Current State of Microcapsule-Based Self-Healing Dental Composites

Resin-based dental composites, commonly used in dentistry, offer several advantages including minimally invasive application, esthetically pleasing appearance, and good physical and mechanical properties. However, these dental composites can be susceptible to microcracks due to various factors in the complex oral environment. These microcracks can potentially lead to clinical restoration failure. Conventional materials and methods are inadequate for detecting and repairing these microcracks in situ. Consequently, incorporating self-healing properties into dental composites has become a necessity. Recent years have witnessed rapid advancements in self-healing polymer materials, drawing inspiration from biological bionics. Microcapsule-based self-healing dental composites (SHDCs) represent some of the most prevalent types of self-healing materials utilized in this domain. In this article, we undertake a comprehensive review of the most recent literature, highlighting key insights and findings related to microcapsule-based SHDCs. Our discussion centers particularly on the preparation techniques, application methods, and the promising future of self-healing microcapsules in the field of dentistry.

Effects of chitosan and TiO2 nanoparticles on the antibacterial property and ability to self-healing of cracks and retrieve mechanical characteristics of dental composites

The aim of this study was to improve the self-healing properties of dental nanocomposite using nanoparticles of TiO2 and chitosan. We evaluated flexural and compressive strength, crack-healing, and self-healing lifespan after 3 months of water aging. The effect of the developed composite on cell viability and toxicity was assessed by an MTT assay on human alveolar basal epithelial cells (A549 cell line). The nanocomposite included 7.5 wt% polyurea-formaldehyde (PUF) and 0, 0.5, and 1 wt% n-TiO2 and chitosan. After the fracture, the samples were put in a mold for 1-90 days to enable healing. Then, the fracture toughness of the healed nanocomposites and the healing yield were measured. The flexural strength of the nanocomposite improved by adding 0.5 wt% n-TiO2, while the compressive strength increased after adding 0.5 wt% chitosan (p > 0.1). When these two materials were used simultaneously, the flexural strength was improved by around 2%; however, the compressive strength was unaffected. Compared to the other sample, the nanocomposite with 0.5 wt% n-TiO2 and chitosan had higher KIC-healing and self-healing efficiency. Self-healing efficacy had no significant effect of water aging over 90 days compared to one day (p > 0.1), demonstrating that the PUF nanocapsules were not damaged.

Effect of silanization of poly (urea-formaldehyde) microcapsules on the flexural strength and self-healing efficiency of an experimental self-healing dental resin composite (An in-vitro study)

OBJECTIVES

This study investigated the impact of using γ-methacryloxypropyl trimethoxy silane (MPS) for surface silanization of poly (urea-formaldehyde) (PUF) microcapsules which enclose a healing liquid of "triethylene glycol dimethacrylate (TEGDMA) and N,N dihydroxyethyl-p-toluidine (DHEPT)" on some mechanical properties of an experimental dental composite as well as its self-healing efficiency.

METHODS

Synthesis of PUF microcapsules was done via in situ polymerization, followed by silanization with MPS silane. Silanized and non-silanized microcapsules were incorporated into a composite containing 30% polymer matrix and 70% fillers at different weight percentages (0%, 5%, 7.5% and 10%). The composite strength and elastic modulus were evaluated by Flexural testing. Fracture toughness KIc and self-healing efficiency were assessed by utilizing the "single edge notched beam" method.

RESULTS

Flexural strength of all groups containing silanized microcapsules was non-significantly different from control group without microcapsules. However, in contrast to control group, all groups containing non-silanized microcapsules displayed considerably decreased flexural strength. Adding silanized and non-silanized microcapsules didn't show a significant change in the KIc-virgin. The silanized microcapsules' groups achieved a self-healing efficiency of about 49-77% recovery in KIc-virgin compared to 38-69% for their non-silanized counterparts.

SIGNIFICANCE

In order to increase the interfacial adhesion with the polymer matrix, improve the mechanical properties, and increase the efficiency of self-healing of dental resin composite, PUF microcapsules were silanized for the first time in the dental field using MPS silane. This innovative silanized microcapsule-containing self-healing composite may hold promise for repairing the damage caused by restorative cracks and extending their service life.

Nanotechnology in toothpaste: Fundamentals, trends, and safety

Several studies have revealed that healthcare nanomaterials are widely used in numerous areas of dentistry, including prevention, diagnosis, treatment, and repair. Nanomaterials in dental cosmetics are utilized to enhance the efficacy of toothpaste and other mouthwashes. Nanoparticles are added to toothpastes for a variety of reasons, including dental decay prevention, remineralization, hypersensitivity reduction, brightening, and antibacterial qualities. In this review, the benefits and uses of many common nanomaterials found in toothpaste are outlined. Additionally, the capacity and clinical applications of nanoparticles as anti-bacterial, whitening, hypersensitivity, and remineralizing agents in the treatment of dental problems and periodontitis are discussed.

Synthesis and characterisation of microcapsules for self-healing dental resin composites

AIM

The purpose of this study was to i) synthesise TEGDMA-DHEPT microcapsules in a laboratory setting; ii) characterise the resultant microcapsules for quality measures.

MATERIALS & METHODS

Microcapsules were prepared by in situ polymerization of PUF shells. Microcapsules characterisation include size analysis, optical and SEM microscopy to measure the diameter and analyse the morphology of PUF microcapsules. FT-IR spectrometer evaluated microcapsules and benzyl peroxide catalyst polymerization independently.

RESULT

Average diameter of TEGDMA-DHEPT microcapsules was 120 ± 45 μm (n: 100). SEM imaging of the capsular shell revealed a smooth outer surface with deposits of PUF nanoparticles that facilitate resin matrix retention to the microcapsules upon composite fracture. FT-IR spectra showed that microcapsules crushed with BPO catalyst had degree of conversion reached to 60.3%.

CONCLUSION

TEGDMA-DHEPT microcapsules were synthesised according to the selected parameters. The synthesised microcapsules have a self-healing potential when embedded into dental resin composite as will be demonstrated in our future work.

Novel antimicrobial and self-healing dental resin to combat secondary caries and restoration fracture

OBJECTIVE

Dental resin composites have been the most popular materials for repairing tooth decay in recent years. However, secondary caries and bulk fracture are the major hurdles that affect the lifetime of dental resin composites. This current study synthesized a novel antimicrobial and self-healing dental resin containing nanoparticle-modified self-healing microcapsules to combat secondary caries and restoration fracture.

METHODS

Multifunctional dental resins containing 0-20% nanoparticle-modified self-healing microcapsules were prepared. The water contact angle, antimicrobial properties, mechanical properties, cell toxicity, and self-healing capability of the dental resins were tested.

RESULTS

A novel multifunctional dental resin was synthesized. When the microcapsule mass fraction was 10%, the resin presented a strong bacteriostasis rate (80.3%) and excellent self-healing efficiency (66.1%), while the hydrophilicity, mechanical properties, and cell toxicity were not affected.

SIGNIFICANCE

The novel antimicrobial self-healing dental resin is a promising candidate for use in clinical practice, which provides a simple and highly efficient strategy to combat secondary caries and restoration fracture. This novel dental resin also gives the inspiration to prolong the service life of dental restorations.

Explore the most recent advancements in the domain of self-healing intelligent composites specifically designed for use in dentistry

Dental composites are commonly utilized in dental treatments because they have the ability to preserve the natural appearance of teeth, are minimally invasive and conservative, and enhance the overall physical and mechanical attributes. Dental composites can experience damage, like small cracks, due to factors like temperature changes and physical strain, which can reduce their effectiveness. Detecting these tiny cracks in dental composites can be quite challenging, and in certain situations, it may even be impossible. In addition, it is not possible to repair these damages in situ by using conventional materials and methods. Therefore, the self-healing ability in dental composites is necessary. In recent years, the spontaneous repair of damages such as micro-cracking in dental composite materials has been developed without any type of human intervention and the replacement of new components. The most widely used approach to create self-healing dental composites involves encapsulating a healing agent within polymer shells and dispersing these microcapsules within the acrylate matrix of the dental composite. To assess the self-healing abilities of these composites, researchers can examine changes in their fracture toughness before and after the healing process using a test called the Single Edge V-notch beam test. In the present article we reviewed the latest findings in the field of self-healing intelligent composites for application in dentistry, and also in the present study, the studies on self-healing smart dental composites will be reviewed.

Mechanical properties and sustainable bacterial resistance effect of strontium-modified phosphate-based glass microfiller in dental composite resins

Dental composite resins are widely used in dental restorations. However, their clinical application is limited by the occurrence of secondary caries. Strontium-modified phosphate-based glass (Sr-PBG) is a material known to have a sustainable bacterial resistance effect. The mechanical properties (in particular, flexural strength, modulus of elasticity, and hardness) of dental materials determine their function. Therefore, this study aimed to investigate the mechanical and ion-releasing properties as well as the sustainable bacterial resistance effect of bioactive resin composites containing Sr-PBG. The data were analyzed by ANOVA and Tuckey's tests (p < 0.05). We incorporated a Sr-PBG microfiller at 3, 6, and 9 wt.% concentrations into a commercially available composite resin and investigated the mechanical properties (flexural strength, elastic modulus, and micro hardness), ion release characteristics, and color of the resultant resins. In addition, we examined the antibacterial effects of the composite resins against Streptococcus mutans (S. mutans). The mechanical properties of the Sr-PBG groups differed only slightly from those of the control group (p > 0.05). However, the optical density at 600 nm of S. mutans incubated on the experimental group was significantly lower compared to that observed with the control (p < 0.05) both before and after thermocycling between 5 and 55 ℃ for 850 cycles (dwell time: 45 s). Therefore, strontium-modified resin materials exhibited a sustainable bacterial resistance effect in vitro while maintaining some of the mechanical properties of ordinary acrylic resins.

Fatigue behaviour of a self-healing dental composite

OBJECTIVE

Novel self-healing resin-based composites containing microcapsules have been developed to improve the mechanical performance of dental restorations. However, the long-term fatigue behaviour of these self-healing composites has still been hardly investigated. Therefore, this manuscript studied the fatigue behaviour of self-healing composites containing microcapsules by subjecting the specimens to traditional staircase tests and ageing in a custom-designed chewing simulator (Rub&Roll) to simulate oral ageing physiologically relevant conditions.

METHODS

To prepare self-healing composite, poly(urea-formaldehyde) microcapsules containing acrylic self-healing liquids were synthesized. Subsequently, these microcapsules (10 wt%) and initiator (benzoyl peroxide, BPO, 2 wt%) were incorporated into a commercial flowable resin-based composite. Microcapsule-free resin-based composites with and without BPO were also prepared as control specimens. A three-point flexural test was used to measure the initial flexural strength (Sinitial). Subsequently, half of the specimens were used for fatigue testing using a common staircase approach to measure the fatigue strengths (FS). In addition, the other specimens were aged in the Rub&Roll machine for four weeks where after the final flexural strength (Sfinal) was measured.

RESULTS

Compared to Sinitial, FS of all tested specimens significantly decreased as measured through staircase testing. After 4 weeks of ageing in the Rub&Roll machine, Sfinal was significantly reduced compared to Sinitial for microcapsule-free resin-based composites, but not for the self-healing composites (p = 0.3658). However, the self-healing composites are still in the experimental phase characterized by a low mechanical strength, which still impedes further clinical translation.

SIGNIFICANCE

Self-healing composites containing microcapsules exhibit improved fatigue resistance compared to microcapsule-free non-self-healing composites.

Supramolecular Self-Healing Antifouling Coating for Dental Materials

In orthodontic treatment, orthodontic appliances are prone to bacterial infections, which pose a risk to oral health. Surface modification of orthodontic appliances has been explored to improve their antifouling properties and impart antibacterial capabilities, inhibiting initial bacterial adhesion and biofilm formation. However, coatings are susceptible to damage in the complex oral environment, leading to a loss of functionality. Here, we have prepared an antifouling self-healing coating based on supramolecular bonding by employing a simple spin coating method. The presence of the hydrophilic zwitterionic trimethylamine N-oxide (TMAO) and the hydrophobic antimicrobial moieties triclosan acrylate (TCSA) imparts to the polymers an amphiphilic structure and enhances the interaction with bacteria, resulting in excellent antimicrobial activity and surface antifouling properties. The multiple hydrogen bonds of ureido-pyrimidinone methacrylate (UPyMA) and ionic interactions contained in the polymers not only increased the adhesion of the coating to the material substrate (approximately 3 times) but also endowed the coating with the intrinsic self-healing ability to restore the antibiofouling properties at oral temperature and humidity. Finally, the polymer coating is biologically safe both in vitro and in vivo, showing no cytotoxic effects on cells and tissues. This research offers a promising avenue for improving the performance of orthodontic appliances and contributes to the maintenance and treatment of oral health.

Effect of monodisperse mesoporous bioactive glass spheres (MBGs) on the mechanical properties and bioactivity of dental composites

Secondary caries is one of the main reasons for the failure of dental resin composites, and adding bioactive fillers such as bioactive glass and amorphous calcium phosphate to the resin composites has been proved to be an effective solution for this problem. In the present study, we investigated the effect of monodisperse mesoporous bioactive glass spheres (MBGs) we prepared on the mechanical properties and bioactivity of dental resins. The results revealed that compared with traditional bioactive glass (BG), MBGs fillers significantly enhanced the mechanical properties of the dental resin composites, whether they were added alone or as functional fillers together with nonporous silica particles. The dental resins filled with bimodal fillers (mass ratio of MBGs: nonporous silica = 10:50, total filler loading 60 wt%) exhibited the best mechanical performance. Their flexural strength was 37.66% higher than the samples with BG at the same filling proportion. Furthermore, the prepared MBGs possessed excellent monodispersity and sufficient apatite formation performance, and the biocompatibility of the composites were also improved by MBGs fillers. These suggest the potential use of the prepared MBGs as multifunctional fillers for the improvement of the performance of dental resins.

Ceramic Nanomaterials in Caries Prevention: A Narrative Review

Ceramic nanomaterials are nanoscale inorganic metalloid solids that can be synthesised by heating at high temperatures followed by rapid cooling. Since the first nanoceramics were developed in the 1980s, ceramic nanomaterials have rapidly become one of the core nanomaterials for research because of their versatility in application and use in technology. Researchers are developing ceramic nanomaterials for dental use because ceramic nanoparticles are more stable and cheaper in production than metallic nanoparticles. Ceramic nanomaterials can be used to prevent dental caries because some of them have mineralising properties to promote the remineralisation of tooth tissue. Ceramic minerals facilitate the remineralisation process and maintain an equilibrium in pH levels to maintain tooth integrity. In addition, ceramic nanomaterials have antibacterial properties to inhibit the growth of cariogenic biofilm. Researchers have developed antimicrobial nanoparticles, conjugated ceramic minerals with antibacterial and mineralising properties, to prevent the formation and progression of caries. Common ceramic nanomaterials developed for caries prevention include calcium-based (including hydroxyapatite-based), bioactive glass-based, and silica-based nanoparticles. Calcium-based ceramic nanomaterials can substitute for the lost hydroxyapatite by depositing calcium ions. Bioactive glass-based nanoparticles contain surface-reactive glass that can form apatite crystals resembling bone and tooth tissue and exhibit chemical bonding to the bone and tooth tissue. Silica-based nanoparticles contain silica for collagen infiltration and enhancing heterogeneous mineralisation of the dentin collagen matrix. In summary, ceramic nanomaterials can be used for caries prevention because of their antibacterial and mineralising properties. This study gives an overview of ceramic nanomaterials for the prevention of dental caries.

Development of functional fillers as a self-healing system for dental resin composite

OBJECTIVES

To evaluate the incorporation of repairing capsules containing different monomers and polymerization modulators on the self-healing efficiency of an experimental photopolymerizable resin-based composite.

METHODS

Self-healing capsules containing different monomers and polymerization modulators were prepared by emulsion polymerization: TC_DHEPT (TEGDMA and DHEPT), BTC_DHEPT (Bis-GMA, TEGDMA, and DHEPT), and BTC_BPO (Bis-GMA, TEGDMA, and BPO). The capsules were analyzed through Fourier transform infrared spectroscopy and scanning electron microscopy. The capsules were added into experimental photopolymerizable resin composites establishing the following groups: ER (Control without capsules), ER+BPO, ER+BPO+TC_DHEPT, and ER+BTC_BPO+BTC_DHEPT. Filtek Z350 resin composite (3 M ESPE) was used as a commercial reference. The materials were tested for degree of conversion (DC), flexural strength (σf), elastic modulus (Ef), fracture toughness (virgin K_IC), self-healing efficiency (healed K_IC), and roughness. For statistical analysis, the significance value was established at an a = 0.05 level.

RESULTS

When compared to the control material, the incorporation of repairing capsules did not affect DC, σf, and Ef. Fracture toughness was statistically similar between the experimental groups (p ≤ 0.05). Healed K_IC was statistically different between the groups ER+TC_DHEP and ER+BTC_BPO+BTC_DHEPT; the self-healing efficiency was higher for ER+TC_DHEPT. Surface roughness was statistically similar among all groups.

CONCLUSIONS

The use of self-healing capsules promoted repair of the material. Studies with material aging after the self-healing process are necessary to better demonstrate the effectiveness of this system.

CLINICAL SIGNIFICANCE

The self-healing system seemed to be a promising technology to be used in self-repaired restorative materials, which may prevent restoration fractures.

Current Strategies to Control Recurrent and Residual Caries with Resin Composite Restorations: Operator- and Material-Related Factors

This review addresses the rationale of recurrent and/or residual caries associated with resin composite restorations alongside current strategies and evidence-based recommendations to arrest residual caries and restrain recurrent caries. The PubMed and MEDLINE databases were searched for composite-associated recurrent/residual caries focusing on predisposing factors related to materials and operator’s skills; patient-related factors were out of scope. Recurrent caries and fractures are the main reasons for the failure of resin composites. Recurrent and residual caries are evaluated differently with no exact distinguishment, especially for wall lesions. Recurrent caries correlates to patient factors, the operator’s skills of cavity preparation, and material selection and insertion. Material-related factors are significant. Strong evidence validates the minimally invasive management of deep caries, with concerns regarding residual infected dentin. Promising technologies promote resin composites with antibacterial and remineralizing potentials. Insertion techniques influence adaptation, marginal seal, and proximal contact tightness. A reliable diagnostic method for recurrent or residual caries is urgently required. Ongoing endeavors cannot eliminate recurrent caries or precisely validate residual caries. The operator’s responsibility to precisely diagnose original caries and remaining tooth structure, consider oral environmental conditions, accurately prepare cavities, and select and apply restorative materials are integral aspects. Recurrent caries around composites requires a triad of attention where the operator’s skills are cornerstones.

"Fatigue-Crack Propagation Behavior in Microcapsule-Containing Self-Healing Polymeric Networks"

Over the last years, research on the design of dental self-healing polymers has grown dramatically. It is related to the promising potential of maximizing the clinical lifespan of dental restorations that this strategy holds. In this manuscript, the microcapsule-based strategy is innovated by incorporating the high toughness component N,N-Dimethylacrylamide (DMAM) into the healing agent systems and analyzing in-depth the change in crack propagation behavior induced by the addition of microcapsules into the highly crosslinked polymeric network. In general, the addition of the hydrophilic and high vapor pressure DMAM into the healing agent systems imposed a challenge for the microencapsulation, which highlighted the importance of tailoring the properties of the capsules' shells according to the core composition. The addition of DMAM as cushioning agent proved to be a successful strategy since it resulted in increased G'/G" crossover time from 0.06 (control) to 0.57 s and decreased storage modulus from 8.0 (control) to 0.5GPa. In addition, the incorporation of microcapsules within the polymerized networks provided obstacles to crack propagation, which translated to an overall reinforcement of the polymeric network, as evidenced by the increase in toughness up to 50 % and energy required to propagate cracks up to 100 % in systems containing DMAM at 20 wt%.

Novel nanoparticle-modified multifunctional microcapsules with self-healing and antibacterial activities for dental applications

OBJECTIVE

Although microcapsules (MCs) have been used for dental resins to achieve self-healing capabilities, the fragile organic shell and single healing event functions during the service period limit their use. Herein, a novel nanoparticle-modified MC with a nano-antibacterial inorganic filler (NIF) containing a quaternary ammonium salt was synthesized to address these issues.

METHODS

MCs with 0 %-30 % NIFs were prepared via an in situ polymerization method and characterized their morphology, chemical composition, thermal stability, roughness, mechanical properties, and antibacterial effect. Subsequently, M-10 MCs were mixed into the resin matrix at a mass fraction of 7.5 %. The self-healing capability and cytotoxicity were evaluated.

RESULTS

The introduction of nanomaterials enhances the shell of the MCs and endows them with an antibacterial effect. With the addition of NIFs, the roughness, modulus, and hardness values of MCs all increased (p < 0.05). The presence of M-10 MCs reduced the CFU by 2-3 orders of magnitude compared to the control group. The dental resin containing 7.5 % M-10 MCs obtained almost 69 % self-healing efficiency, without significantly compromising cell viability (p < 0.05).

SIGNIFICANCE

Self-healing MCs with NIFs were prepared for the first time with strong antibacterial properties, a substantial self-healing capability, and low toxicity. This multifunctional MC is a promising candidate for use in dental resins to extend the service life and resolve the problem of bulk fracture and secondary caries.

Properties of A Model Self-Healing Microcapsule-Based Dental Composite Reinforced with Silica Nanoparticles

Aim: The purpose of this study was to evaluate the mechanical properties of an experimental self-healing dental composite model (SHDC) composed of SiO₂ nanoparticles with varying percentages of triethylene glycol dimethacrylate (TEGDMA) monomer and N,N-dihydroxyethyl-p-toluidine (DHEPT) amine microcapsules. Materials and methods: Microcapsules were prepared by in-situ polymerisation of PUF shells, as explained in our previous work. The model SHDC included bisphenol A glycidyl dimethacrylate (Bis-GMA:TEGDMA) (1:1), 1 wt% phenyl bis(2,4,6-trimethylbenzoyl) phosphine oxide (BAPO), 0.5 wt% benzoyl peroxide (BPO) catalyst, 20 wt% silanised silica dioxide (SiO₂) (15 nm) and (0, 2.5, 5, 7.5, 10 wt%) of microcapsules (120 ± 45 μm). Light transmission, hardness, degree of conversion (DC), flexural strength and elastic modulus of the SHDC model were measured. Results: The degree of conversion of the SHDC ranged from 73 to 76% 24 h after polymerisation. Hardness measurements ranged from 22 to 26 VHN (p > 0.05); however, the flexural strength was adversely affected from 80 to 55 MPa with increasing microcapsules of up to 10 wt% in the composites (p < 0.05). Conclusion: Only flexural strength decreased drastically ~30% with increasing microcapsules (>10 wt%) in the composites. All other measured properties were not significantly affected. Accordingly, we recommend a stronger composite material that could be created by increasing the filler content distribution in order to achieve a hybrid self-healing composite with enhanced mechanical properties.

Mechanism of Thermochromic and Self-Repairing of Waterborne Wood Coatings by Synergistic Action of Waterborne Acrylic Microcapsules and Fluorane Microcapsules

The fluorane thermochromic microcapsules and waterborne acrylic resin microcapsules were added into waterborne coatings at the same time to prepare intelligent waterborne coating film with dual functions of color change and self-repairing. The coating film prepared by adding 15.0% fluorane microcapsules and 5.0% waterborne acrylic resin microcapsules to the primer at the same time had better comprehensive properties. At this time, the coating film changed from yellow to colorless. The repair rate of the coating film was 58.4%. When the temperature was lower than 32 °C, waterborne acrylic resin microcapsules can improve the thermochromic performance of the coating film with fluorane microcapsules. Waterborne acrylic resin microcapsules can alleviate the color change of coating film with fluorane microcapsules. The fluorane microcapsules can improve the self-repairing performance of coating film with waterborne acrylic resin microcapsules. The results lay a theoretical and technical foundation for multifunctional coating film.

Metal and Metal Oxide Nanoparticles in Caries Prevention: A Review

Nanoparticles based on metal and metallic oxide have become a novel trend for dental use as they interfere with bacterial metabolism and prevent biofilm formation. Metal and metal oxide nanoparticles demonstrate significant antimicrobial activity by metal ion release, oxidative stress induction and non-oxidative mechanisms. Silver, zinc, titanium, copper, and magnesium ions have been used to develop metal and metal oxide nanoparticles. In addition, fluoride has been used to functionalise the metal and metal oxide nanoparticles. The fluoride-functionalised nanoparticles show fluoride-releasing properties that enhance apatite formation, promote remineralisation, and inhibit demineralisation of enamel and dentine. The particles' nanoscopic size increases their surface-to-volume ratio and bioavailability. The increased surface area facilitates their mechanical bond with tooth tissue. Therefore, metal and metal oxide nanoparticles have been incorporated in dental materials to strengthen the mechanical properties of the materials and to prevent caries development. Another advantage of metal and metal oxide nanoparticles is their easily scalable production. The aim of this study is to provide an overview of the use of metal and metal oxide nanoparticles in caries prevention. The study reviews their effects on dental materials regarding antibacterial, remineralising, aesthetic, and mechanical properties.

Biocompatible and Biomaterials Application in Drug Delivery System in Oral Cavity

Biomaterials applications have rapidly expanded into different fields of sciences. One of the important fields of using biomaterials is dentistry, which can facilitate implantation, surgery, and treatment of oral diseases such as peri-implantitis, periodontitis, and other dental problems. Drug delivery systems based on biocompatible materials play a vital role in the release of drugs into aim tissues of the oral cavity with minimum side effects. Therefore, scientists have studied various delivery systems to improve the efficacy and acceptability of therapeutic approaches in dental problems and oral diseases. Also, biomaterials could be utilized as carriers in biocompatible drug delivery systems. For instance, natural polymeric substances, such as gelatin, chitosan, calcium phosphate, alginate, and xanthan gum are used to prepare different forms of delivery systems. In addition, some alloys are conducted in drug complexes for the better in transportation. Delivery systems based on biomaterials are provided with different strategies, although individual biomaterial has advantages and disadvantages which have a significant influence on transportation of complex such as solubility in physiological environments or distribution in tissues. Biomaterials have antibacterial and anti-inflammatory effects and prolonged time contact and even enhance antibiotic activities in oral infections. Moreover, these biomaterials are commonly prepared in some forms such as particulate complex, fibers, microspheres, gels, hydrogels, and injectable systems. In this review, we examined the application of biocompatible materials in drug delivery systems of oral and dental diseases or problems.

A comprehensive review of the antibacterial activity of dimethylaminohexadecyl methacrylate (DMAHDM) and its influence on mechanical properties of resin-based dental materials

The repetitive restorative cycle should be avoided, aiming at the smallest number of restorations' replacements to ensure greater tooth longevity. Antibacterial materials associated with the control of caries etiological factors can help improve restoration's durability. This review aimed to analyze the results of in vitro studies that added Dimethylaminohexadecyl methacrylate (DMAHDM), an antibacterial monomer, to restorative materials. The PubMed, SCOPUS, Web of Science, and Biblioteca Virtual em Saúde databases were screened for studies published between 2015 and 2020. After full-text reading, 24 articles were included in the final sample. DMAHDM has demonstrated antibacterial efficacy against several bacteria related to dental caries and periodontal diseases, causing a transition in the biofilm balance without inducing resistance. When DMAHDM was included in acrylic resin, the material cytotoxicity increased, and changes in mechanical properties were observed. In contrast, resin composites had their mechanical properties maintained in most studies; however, toxicity was not examined. The association between DMAHDM and 2-methacryloyloxyethyl phosphorylcholine or silver nanoparticles improved the antibacterial effect. Besides, the association with nanoparticles of amorphous calcium phosphate or nanoparticles of calcium fluoride can provide remineralization capacity. There is a lack of information on the cytotoxicity and bacteria resistance induction, and further studies are needed to address this.

Novel Nano Calcium Fluoride Remineralizing and Antibacterial Dental Composites

OBJECTIVE

Composites with remineralizing and antibacterial properties are favorable for caries inhibition. The objectives of this study were to develop a new bioactive nanocomposite with remineralizing and antibiofilm properties by incorporating dimethylaminohexadecyl methacrylate (DMAHDM) and nano-calcium fluoride (nCaF₂).

METHODS

nCaF₂ was produced via a spray-drying method and integrated at 15% mass fraction into composite. DMAHDM was added at 3% mass fraction. Mechanical properties and F and Ca ion releases were assessed. Colony-forming units (CFU), lactic acid and metabolic activity of biofilms on composites were performed.

RESULTS

The new composites had flexural strengths of (95.28±6.32) MPa and (125.93±7.49) MPa, which were within the ISO recommendations. Biofilm CFU were reduced by 3-4 log (p<0.05). The composites achieved high F releases of (0.89±0.01) mmol/L and (0.44±0.01) mmol/L, and Ca releases of (1.46±0.05) mmol/L and (0.54±0.005) mmol/L.

CONCLUSIONS

New nanocomposites were developed with good mechanical properties, potent antibacterial activity against salivary biofilms, and high F and Ca ion releases with potential for remineralization.

CLINICAL SIGNIFICANCE

Novel nanocomposites using nCaF₂ and DMAHDM were developed with potent antibacterial and remineralizing effects and high F and Ca ion releases. They are promising to inhibit recurrent caries, promote remineralization, and possess long-term sustainability.

The Antibacterial and Remineralizing Effects of Biomaterials Combined with DMAHDM Nanocomposite: A Systematic Review

Researchers have developed novel nanocomposites that incorporate additional biomaterials with dimethylaminohexadecyl methacrylate (DMAHDM) in order to reduce secondary caries. The aim of this review was to summarize the current literature and assess the synergistic antibacterial and remineralizing effects that may contribute to the prevention of secondary caries. An electronic search was undertaken in MEDLINE using PubMed, Embase, Scopus, Web of Science and Cochrane databases. The initial search identified 954 papers. After the removal of duplicates and screening the titles and abstracts, 15 articles were eligible for this review. The amalgamation of 2-methacryloyloxyethyl phosphorylcholine (MPC) and silver nanoparticles (AgNPs) with DMAHDM resulted in increased antibacterial potency. The addition of nanoparticles of amorphous calcium phosphate (NACP) and polyamidoamine dendrimers (PAMAM) resulted in improved remineralization potential. Further clinical studies need to be planned to explore the antibacterial and remineralizing properties of these novel composites for clinical success.

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.

Influence of microcapsule parameters and initiator concentration on the self-healing capacity of resin-based dental composites

OBJECTIVE

Fracture is one of the main causes for failure of resin-based composite restorations. To overcome this drawback, self-healing resin-based composites have been designed by incorporation of microcapsules. However, the relationship between their self-healing capacity and microcapsule and resin parameters is still poorly understood. Therefore, the objective of this study was to systematically investigate the effect of initiator concentration (in the resin) and microcapsule size and concentration on the self-healing performance of commercially available flowable resin-based composites.

METHODS

Poly(urea-formaldehyde) (PUF) microcapsules containing acrylic healing liquid were synthesized in small (33±8μm), medium (68±21μm) and large sizes (198±43μm) and characterized. Subsequently, these microcapsules were incorporated into a conventional flowable resin-based composite (Majesty Flow ES2, Kuraray) at different contents (5-15wt%) and benzoyl peroxide (BPO) initiator concentrations (0.5-2.0wt%). Fracture toughness (K_IC) of test specimens was tested using a single edge V-notched beam method. Immediately after complete fracture (K_IC-initial), the two fractured parts were held together for 72h to allow for healing. Subsequently, fracture toughness of the healed resin-based composites (K_IC-healed) was tested as well.

RESULTS

The fracture toughness of healed dental composites significantly increased with increasing microcapsule size and concentration (2wt% BPO, p<0.05). The highest self-healing efficiencies (up to 76%) were obtained with microcapsules sized 198±43 um.

SIGNIFICANCE

commercially available resin-based composites can be rendered self-healing most efficiently by incorporation of large microcapsules (198±43μm). However, long-term tests on fatigue and wear behavior are needed to confirm the clinical efficacy.

Advances of Anti-Caries Nanomaterials

Caries is the most common and extensive oral chronic disease. Due to the lack of anti-caries properties, traditional caries filling materials can easily cause secondary caries and lead to treatment failure. Nanomaterials can interfere with the bacteria metabolism, inhibit the formation of biofilm, reduce demineralization, and promote remineralization, which is expected to be an effective strategy for caries management. The nanotechnology in anti-caries materials, especially nano-adhesive and nano-composite resin, has developed fast in recent years. In this review, the antibacterial nanomaterials, remineralization nanomaterials, and nano-drug delivery systems are reviewed. We are aimed to provide a theoretical basis for the future development of anti-caries nanomaterials.

Novel antibacterial calcium phosphate nanocomposite with long-term ion recharge and re-release to inhibit caries

Short-term studies on calcium-phosphate (CaP) ion-rechargeable composites were reported. The long-term rechargeability is important but unknown. The objectives of this study were to investigate nanocomposite with strong antibacterial and ion-recharge capabilities containing dimethylaminododecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP), and evaluate long-term ion-recharge by testing for 12 cycles (taking 6 months to complete) for the first time. Three groups were tested: (1) Heliomolar control; (2) Resin+20%NACP+50%glass; (3) Resin+3%DMAHDM+20%NACP+50%glass. Biofilm acid and colony-forming units (CFU) were measured. Ion-recharge was tested for 12 cycles. NACP-DMAHDM composite reduced biofilm acid, and reduced CFU by 4 logs. High levels of ion releases were maintained throughout 12 cycles of recharge, maintaining steady-state releases without reduction in 6 months (p>0.1), representing long-term remineralization potential. Bioactive nanocomposite demonstrated long-term ion-rechargeability for the first time, showed remineralization and potent anti-biofilm functions, with promise for tooth restorations to combat caries.

Novel Bioactive and Therapeutic Root Canal Sealers with Antibacterial and Remineralization Properties

According to the American Dental Association Survey of Dental Services Rendered (published in 2007), 15 million root canal treatment procedures are performed annually. Endodontic therapy relies mainly on biomechanical preparation, chemical irrigation and intracanal medicaments which play an important role in eliminating bacteria in the root canal. Furthermore, adequate obturation is essential to confine any residual bacteria within the root canal and deprive them of nutrients. However, numerous studies have shown that complete elimination of bacteria is not achieved due to the complex anatomy of the root canal system. There are several conventional antibiotic materials available in the market for endodontic use. However, the majority of these antibiotics and antiseptics provide short-term antibacterial effects, and they impose a risk of developing antibacterial resistance. The root canal is a dynamic environment, and antibacterial and antibiofilm materials with long-term effects and nonspecific mechanisms of action are highly desirable in such environments. In addition, the application of acidic solutions to the root canal wall can alter the dentin structure, resulting in a weaker and more brittle dentin. Root canal sealers with bioactive properties come in direct contact with the dentin wall and can play a positive role in bacterial elimination and strengthening of the root structure. The new generation of nanostructured, bioactive, antibacterial and remineralizing additives into polymeric resin-based root canal sealers are discussed in this review. The effects of these novel bioactive additives on the physical and sealing properties, as well as their biocompatibility, are all important factors that are presented in this article.

[Application and potential future directions of self-healing polymers in dentistry]

Self-healing materials have rapidly developed in recent years to overcome the micro-cracks occurring in the polymer matrix. Self-healing ability offers autonomous crack repairs to prolong the service lives of polymers or polymer composites. As a main approach, extrinsic self-healing materials based on microcapsules have been applied in dentistry recently. This paper comprehensively presented and reviewed the definition and classification of self-healing materials, the synthesis of microcapsules, the calculation of self-healing efficiency, and the application of self-healing materials in dentistry. The future directions of self-healing polymers are also discussed.

Antibacterial Properties of Nanoparticles in Dental Restorative Materials. A Systematic Review and Meta-Analysis

Background and Objectives: Nanotechnology has become a significant area of research focused mainly on increasing the antibacterial and mechanical properties of dental materials. The aim of the present systematic review and meta-analysis was to examine and quantitatively analyze the current evidence for the addition of different nanoparticles into dental restorative materials, to determine whether their incorporation increases the antibacterial/antimicrobial properties of the materials. Materials and Methods: A literature search was performed in the Pubmed, Scopus, and Embase databases, up to December 2018, following PRISMA (Preferred Reporting Items for Systematic Review and Meta-Analysis) guidelines for systematic reviews and meta-analyses. Results: A total of 624 papers were identified in the initial search. After screening the texts and applying inclusion criteria, only 11 of these were selected for quantitative analysis. The incorporation of nanoparticles led to a significant increase (p-value <0.01) in the antibacterial capacity of all the dental materials synthesized in comparison with control materials. Conclusions: The incorporation of nanoparticles into dental restorative materials was a favorable option; the antibacterial activity of nanoparticle-modified dental materials was significantly higher compared with the original unmodified materials, TiO₂ nanoparticles providing the greatest benefits. However, the high heterogeneity among the articles reviewed points to the need for further research and the application of standardized research protocols.

The importance of being amorphous: calcium and magnesium phosphates in the human body

This article focuses on the relevance of amorphous calcium (and magnesium) phosphates in living organisms. Although crystalline calcium phosphate (CaP)-based materials are known to constitute the major inorganic constituents of human hard tissues, amorphous CaP-based structures, often in combination with magnesium, are frequently employed by Nature to build up components of our body and guarantee their proper functioning. After a brief description of amorphous calcium phosphate (ACP) formation mechanism and structure, this paper is focused on the stabilization strategies that can be used to enhance the lifetime of the poorly stable amorphous phase. The various locations of our body in which ACP (pure or in combination with Mg²⁺) can be found (i.e. bone, enamel, small intestine, calciprotein particles and casein micelles) are highlighted, showing how the amorphous nature of ACP is often of paramount importance for the achievement of a specific physiological function. The last section is devoted to ACP-based biomaterials, focusing on how these materials differ from their crystalline counterparts in terms of biological response.

Application of Antimicrobial Nanoparticles in Dentistry

Oral cavity incessantly encounters a plethora of microorganisms. Plaque biofilm-a major cause of caries, periodontitis and other dental diseases-is a complex community of bacteria or fungi that causes infection by protecting pathogenic microorganisms from external drug agents and escaping the host defense mechanisms. Antimicrobial nanoparticles are promising because of several advantages such as ultra-small sizes, large surface-area-to-mass ratio and special physical and chemical properties. To better summarize explorations of antimicrobial nanoparticles and provide directions for future studies, we present the following critical review. The keywords "nanoparticle," "anti-infective or antibacterial or antimicrobial" and "dentistry" were retrieved from Pubmed, Scopus, Embase and Web of Science databases in the last five years. A total of 172 articles met the requirements were included and discussed in this review. The results show that superior antibacterial properties of nanoparticle biomaterials bring broad prospects in the oral field. This review presents the development, applications and underneath mechanisms of antibacterial nanoparticles in dentistry including restorative dentistry, endodontics, implantology, orthodontics, dental prostheses and periodontal field.

Effects of S. mutans gene-modification and antibacterial calcium phosphate nanocomposite on secondary caries and marginal enamel hardness

Secondary caries at the restoration-tooth margins is a main reason for dental restoration failures. Gene-modification for Streptococcus mutans (S. mutans) and composites containing dimethylaminohexadecyl methacrylate (DMAHDMA) and nanoparticles of amorphous calcium phosphate (NACP) all have the potential to suppress bacterial acids and promote remineralization. However, there has been no report of their effects on marginal caries-inhibition and enamel hardness. The objective of this study was to investigate the effects of gene-modification and DMAHDM–NACP composite restoration on enamel demineralization and hardness at the margins under biofilm acids for the first time. Parent S. mutans and rnc gene-deleted S. mutans were tested side by side. The bioactive composite contained 3% DMAHDM and 30% NACP. Mechanical properties and calcium (Ca) and phosphate (P) ion releases were measured. Colony-forming units (CFU), MTT, lactic acid and polysaccharide of biofilms were evaluated. Demineralization of bovine enamel with composite restorations was induced via biofilms, then enamel hardness was measured. The dual strategy of combining rnc-deletion with DMAHDM+30NACP: (1) achieved the strongest biofilm-inhibition, with the greatest reduction in biofilm CFU by 6 logs; (2) decreased biofilm lactic acid and polysaccharide production by more than 80%; (3) achieved enamel hardness that was 140% higher than that of a commercial fluoride-releasing composite under 30 days of biofilm acids. Therefore, the novel dual approach of rnc gene-deletion and DMAHDM+NACP nanocomposite is promising to inhibit secondary caries at the margins and increase the longevity of tooth restorations.

Secondary caries at the restoration-tooth margins is a main reason for dental restoration failures.

In vitro antibacterial activity of self-etch bio-active dental adhesives after artificial aging

Purpose:

The aims to evaluate the antibacterial effect of different bioactive component containing dental adhesives before and after artificial aging.

Materials and methods:

Two bio-active adhesives; Clearfil Protect Bond and FL Bond II, two non-bioactive adhesives, Clearfil SE Bond and Clearfil S3 Bond were used for this study. Antibacterial activities of the fresh and aged samples against Streptococcus mutans were investigated with Direct Contact Test. Data were analyzed with Kruskal Wallis and Mann Whitney U multiple comparison tests.

Results:

For fresh samples FL Bond II and Clearfil Protect Bond exhibit similar antibacterial effect but Clearfil Protect Bond showed significantly higher antibacterial effect after aging the samples (p<0.05).

Conclusion:

The incorporation of bio-active antibacterial components into adhesive systems may be considered as a fundamental component in inhibiting residual Streptococcus mutans when considering the antibacterial effect of fresh samples of bio-active adhesives.

A review of bioceramics-based dental restorative materials

Currently, much has been published related to conventional resin-based composites and adhesives; however, little information is available about bioceramics-based restorative materials. The aim was to structure this topic into its component parts and to highlight the translational research that has been conducted up to the present time. A literature search was done from indexed journals up to September 2017. The main search terms used were based on dental resin-based composites, dental adhesives along with bioactive glass and the calcium phosphate family. The results showed that in 123 articles, amorphous calcium phosphate (39.83%), hydroxyapatite (23.5%), bioactive glass (16.2%), dicalcium phosphate (5.69%), monocalcium phosphate monohydrate (3.25%), and tricalcium phosphate (2.43%) have been used in restorative materials. Moreover, seven studies were found related to a newly developed commercial bioactive composite. The utilization of bioactive materials for tooth restorations can promote remineralization and a durable seal of the tooth-material interface.

Protein-repellent nanocomposite with rechargeable calcium and phosphate for long-term ion release

OBJECTIVE

There has been no report on the effect of incorporating protein repellent 2-methacryloyloxyethyl phosphorylcholine (MPC) into a composite containing nanoparticles of amorphous calcium phosphate (NACP) on calcium (Ca) and phosphate (P) ion rechargeability. The objectives of this study were to develop a Ca and P ion-rechargeable and protein-repellent composite for the first time, and investigate the effects of MPC and NACP on mechanical properties, protein-repellency, anti-biofilm effects, and Ca and P ion recharge and re-release.

METHODS

NACP were synthesized using a spray-drying technique. The resin contained ethoxylated bisphenol A dimethacrylate (EBPADMA) and pyromellitic glycerol dimethacrylate (PMGDM). Three NACP composites were made with 0 (control), 1.5%, and 3% of MPC. NACP (20%) and glass particles (50%) were also added into the resin. Protein adsorption was measured using a micro-bicinchoninic acid (BCA) method. A human saliva microcosm biofilm model was used to determine biofilm metabolic activity, lactic acid, and colony-forming units (CFU). Ca and P ion recharge and re-release were measured using a spectrophotometric method.

RESULTS

Flexural strengths and moduli of CaP-rechargeable composites matched those of a commercial composite without CaP rechargeability (p>0.1). Adding 1.5% and 3% MPC reduced protein adsorption to 1/3 and 1/5, respectively, that of commercial composite (p<0.05). Adding 3% MPC suppressed biofilm metabolic activity and lactic acid production, and reduced biofilm CFU by nearly 2 logs. All three NACP composites had excellent ion rechargeability and higher levels of ion re-releases. One recharge yielded continuous ion release for 21 days. The release was maintained at the same level with increasing number of recharge cycles, indicating long-term ion release. Incorporation of MPC did not compromise the CaP ion rechargeability.

SIGNIFICANCE

Incorporating 3% MPC into NACP nanocomposite greatly reduced protein adsorption, biofilm growth and lactic acid, decreasing biofilm CFU by nearly 2 logs, without compromising Ca and P recharge. This protein-repellent NACP-MPC rechargeable composite with long-term remineralization is promising for tooth restorations to inhibit secondary caries.

Biological evaluation of subgingivally placed direct resin composite materials

Placement of composite resin restorations in deep subgingival cavities can damage surrounding soft tissues. In addition, commonly used resin-based composites (RBCs) might interfere with wound healing and periodontal health. To clarify cellular interactions with RBCs, we used an MTT assay to investigate adhesion of primary human gingival fibroblasts and human osteoblasts (hFOB 1.19) on five RBC materials with and without surface modifications (alumina blasting with 50- or 110-μm Al₂O₃). In addition, high-performance liquid chromatography (HPLC) was used to determine release of resin monomers from RBCs after 1 h, 1 day, and 7 days. As compared with tissue culture plastics (the control), cellular adhesion was significantly lower (P < 0.001) for human gingival fibroblasts and osteoblasts. Only minor, nonsignificant differences between individual RBCs were identified. HPLC analyses identified the release of three bifunctional methacrylates bisphenol A glycerolate dimethacrylate, triethylene glycol dimethacrylate, and diurethane dimethacrylate from RBCs and showed that monomer release increased between 1 h and 1 day but remained low. The present findings suggest that surface adhesion in the subgingival area is limited for the tested RBCs. Although residual monomer release was low for all tested RBCs, it might be sufficient to adversely affect cell adhesion.