Dental Adhesive Resin Research Articles

Optimization of an ultra-bright real-time high-throughput renilla luciferase assay for antibacterial assessment of Streptococcus mutans biofilms

ObjectiveThe present work demonstrates the optimization of a renilla-based real-time, ultra-bright, non-disruptive, high-throughput bioluminescence assay (HTS) to assess the metabolism of intact Streptococcus mutans biofilms and its utility in screening the antibacterial efficacy of experimental nanofilled dental adhesive resins containing varying concentrations of nitrogen-doped titanium dioxide nanoparticles (N_TiO2). Methods. Optimization of the assay was achieved by screening real-time bioluminescence changes in intact Streptococcus mutans biofilms imposed by the various experimental biofilm growth parameters investigated (bacterial strain, growth media, sucrose concentration, dilution factor, and inoculum volume). The optimized assay was then used to characterize the antibacterial efficacy of experimental nanofilled dental adhesive resins. The assay’s ability to discriminate between bacteriostatic and bactericidal approaches was also investigated. Results. Relative Light Units (RLU) values from the HTS optimization were analyzed by multivariate ANOVA (α = 0.05) and coefficients of variation. An optimized HTS bioluminescence assay was developed displaying RLUs values (brightness) that are much more intense when comparing to other previously reported bioluminescence assays, thereby decreasing the error associated with bioluminescence assays and displaying better utility while investigating the functionalities of antimicrobial nanofilled experimental dental adhesive resins with proven long-term properties. Significance. The present study is anticipated to positively impact subsequent research on dental materials and oral microbiology because it serves as a valuable screening tool in metabolic-based assays with increased sensitivity and robustness. The assay reported is anticipated to be further optimized to be used as a co-reporter for other Luc based assays.

Synthesis and characterization of Nb5+ and Sm3+-doped 13–93 bioactive glass particles with improved photon transmission properties for advanced biomedical and dental applications

Bioactive glasses are renowned for their applications in dentistry, serving as restorative materials, dental adhesives, intracanal medicaments, and agents for enamel remineralization. Niobium pentoxide (Nb2O5) is employed in dental adhesive resins and orthodontic adhesives, offering radio-pacifying properties essential for dental materials. Samarium oxide (Sm2O3) emerges as a potential additive in aesthetic restorative dental ceramics and resins, enhancing the natural fluorescence of teeth. In this study Nb2O5 and Sm2O3-doped (1, 3, and 5 wt%) 13–93 bioactive glass particles were synthesized via the sol-gel method, tailored for dental implementations. We conducted a comprehensive analysis of the physical, structural, and optical properties of the resultant glass powders. Additionally, their in vitro bioactivity and ionizing radiation shielding characteristics were rigorously evaluated. The results indicate that Sm3+ ions preserve the amorphous nature of the silicate glasses, while Nb5+ incorporation leads to the crystallization of the T-Nb2O5 phase. Bioactivity assays across three physiological fluids—simulated body fluid, α-minimum essential medium, and phosphate-buffered saline, demonstrated the ability of doped glasses to facilitate hydroxyapatite layer formation, with the most pronounced bioactivity observed in phosphate-buffered saline immersed samples. Furthermore, radiation shielding simulations reveal that the addition of Nb2O5 and Sm2O3 enhances the ionizing radiation attenuation capabilities of the glasses, a property that holds significant promise for protecting against radiation in dental radiology. It can be concluded that the dual functionality of Nb5+ and Sm3+-doped bioactive glasses, which may revolutionize restorative dental practices and offer improved protection in radiological applications.

Antibacterial Properties of an Experimental Dental Resin Loaded with Gold Nanoshells for Photothermal Therapy Applications.

This study explored the chemical and antibacterial properties of a dental resin loaded with gold nanoshells (AuNPs) in conjunction with photothermal therapy (PTT) as a novel method against Streptococcus mutans (S. mutans) to prevent secondary caries. First, a 20-h minimum inhibitory concentration (MIC) assay was performed on solutions of AuNPs with planktonic S. mutans under an LED device and laser at 660 nm. Next, resin blends containing 0, 1 × 1010, or 2 × 1010 AuNPs/mL were fabricated, and the degree of conversion (DC) was measured using an FTIR spectroscopy. Lastly, a colony forming unit (CFU) count was performed following 24 h growth of S. mutans on 6 mm diameter resin disks with different light treatments of an LED device and a laser at 660 nm. The MIC results only showed a reduction in S. mutans at AuNP concentrations less than 3.12 µg/mL under a laser illumination level of 95.5 J/cm2 compared to the dark treatment (p < 0.010 for each). CFU and DC results showed no significant dependence on any light treatment studied. The AuNPs expressed antibacterial effects following PPT against planktonic S. mutans but not in a polymerized dental adhesive resin. Future studies should focus on different shapes, structure, and concentrations of AuNPs loaded in a resin blend.

Shear Bond Strength and Color Stability of Novel Antibacterial Nanofilled Dental Adhesive Resins.

Experimental adhesives containing co-doped metaloxide nanoparticles were demonstrated to display strong and long-term antibacterial properties against Streptococcus mutans biofilms. The present study represents an effort to characterize the shear-bond strength (SBS) and color stability (CS) of these novel biomaterials. Experimental adhesives were obtained by dispersing nitrogen and fluorine co-doped titanium dioxide nanoparticles (NF_TiO2, 10%, 20% or 30%, v/v%) into OptiBond Solo Plus (OPTB). Dentin surfaces were wet-polished (600-Grit). Specimens (n = 5/group) of Tetric EvoCeram were fabricated and bonded using either OPTB or experimental (OPTB + NF_TiO2) adhesives. Specimens were stored in water (37 °C) for twenty-four hours (T1), three months (T2), and six months (T3). At T1, T2, or T3, specimens were removed from water storage and were tested for SBS. Disc-shaped specimens (n = 10/group; d = 6.0 mm, t = 0.5 mm) of adhesives investigated were fabricated and subjected to thermocycling (10,000 cycles, 5−55 °C, 15 s dwell time). Specimens’ colors were determined with a VITA Easyshade® V spectrophotometer (after every 1000 cycles). SBS data was analyzed using two-way ANOVA and post-hoc Tukey tests, while CS data was analyzed using one-way ANOVA and post-hoc Tukey tests (α = 0.05). Mean values of SBS ranged from 16.39 ± 4.20 MPa (OPTB + 30%NF_TiO2) to 19.11 ± 1.11 MPa (OPTB), from 12.99 ± 2.53 MPa (OPTB + 30% NF_TiO2) to 14.87 ± 2.02 (OPTB) and from 11.37 ± 1.89 (OPTB + 20% NF_TiO2) to 14.19 ± 2.24 (OPTB) after twenty-four hours, three months, and six months of water storage, respectively. Experimental materials had SBS values that were comparable (p > 0.05) to those from OPTB independently of nanoparticle concentration or time-point considered. Experimental materials with higher NF_TiO2 concentrations had less intense color variations and were more color stable than OPTB even after 10,000 thermocycles. In combination, the results reported have demonstrated that experimental adhesives can establish strong and durable bonds to human dentin while displaying colors that are more stable, thereby suggesting that the antibacterial nanotechnology investigated can withstand the harsh conditions within the oral cavity without compromising the esthetic component of dental restorations.

Effect of naturally derived antioxidants as polymerization inhibitors on experimental adhesive resins

This study aimed to evaluate the physico-mechanical and biological properties of experimental adhesive resins modified with different antioxidants as radical polymerization inhibitors. The adhesive resins were formulated by mixing BIS-GMA, TEGDMA and HEMA (mass ratio of 50/25/25 wt%) and a tertiary initiation system (CQ + EDAB + DPHIHF –molar concentration of 1 %, 2 % and 1 %, respectively) together. Different antioxidants were added (1 mol%) to aliquots of the experimental resin, as follows: BHT (Butylated hydroxytoluene); HQ (hydroquinone); QC (quercetin); GA (gallic acid); and AA (ascorbic acid). An unmodified resin was used as control. The resin adhesives were tested with regard to sensitivity to ambient light, degree of conversion, cohesive strength, yellowing index, color stability; in addition, translucence and cytotoxicity (MTT assay) were analyzed. The data were analyzed using ANOVA and Tukey post-hoc tests (α = 5 %). The control and AA-based adhesive failed in the sensitivity to ambient light test. Adhesives modified with BHT and AA showed lower DC than the others. Color was considerably changed for the QC-containing adhesive. The presence of QC in the adhesive resulted in a higher yellowing index. When compared with the control, the addition of GA resulted in a reduction of the cohesive strength of the materials. All adhesives demonstrated similar cell viability and translucency. The use of alternative antioxidants as polymerization inhibitors rather than the synthetic types traditionally used showed potential application for the formulation of novel dental adhesive resins without significant impairment of the biological and physico-mechanical performance of the material.

Characterization of Experimental Nanoparticulated Dental Adhesive Resins with Long-Term Antibacterial Properties.

Experimental adhesives with functional nitrogen-doped titanium dioxide nanoparticles (N_TiO2) have been shown to display improved properties. However, these materials have not been characterized regarding their degree of conversion (DC), biaxial flexure strength (BFS), surface roughness (SR), elastic modulus (EM), and long-term antibacterial functionalities. Experimental adhesives were synthesized by dispersing N_TiO2 (10%, 20%, or 30%, v/v%) into OptiBond Solo Plus (OPTB, Kerr Corp., USA). Unpolymerized adhesives (volume = 50 μL/drop, n = 3/group) were individually placed onto a heated (37 °C) attenuated total reflectance (ATR) monolithic diamond crystal (Golden Gate, Specac). The spectra of composites were obtained with a Fourier-transform infrared (FTIR) spectrometer (Nicolet IS50; 500-4500 cm-1; resolution = 4 cm-1, 10 internal scans/spectrum) before and after polymerization. Disk-shaped specimens (diameter = 6.0 mm, thickness = 0.5 mm) for BFS (n = 12/group), SR and EM (n = 3/group), and for antibacterial testing (n = 18/group/time-point) were fabricated and photopolymerized (1 min each; 385-515 nm, 1000 mW/cm2; VALO). DC values (%) were calculated from pre- and post-polymerization spectra using the two-frequency method and tangent-baseline technique. BFS was assessed using a universal testing machine (Instron 68TM-5, crosshead speed = 1.27 mm/min, 25 °C). SR and EM were investigated using an atomic force microscope (Multimode 8) with aluminum-coated silicon probes (8 nm pyramidal tip, spring constant 40 N/m, Bruker). Antibacterial testing was performed by growing Streptococcus mutans biofilms (UA159-ldh, 37 °C, microaerophilic) on the surfaces of specimens for 24 h and then measuring the relative luminescence units (RLU) with a Biotek Synergy HT multi-well plate reader. Results demonstrate that experimental materials containing 10%, 20%, and 30% of N_TiO2 displayed higher levels of DC, had better mechanical properties, and were able to exert strong and durable antibacterial properties without visible light irradiation and after extended periods of simulated shelf-life and aging in PBS. The reported experimental materials are expected to increase the service lives of polymer-based bonded restorations by decreasing the incidence of secondary caries.

Cytotoxicity and Apoptotic Mechanism of 2-Hydroxyethyl Methacrylate via Genotoxicity and the Mitochondrial-Dependent Intrinsic Caspase Pathway and Intracellular Reactive Oxygen Species Accumulation in Macrophages.

Macrophages are mainly active cells of the immune system and play a role in the defense of pathogens. However, the overactivation of macrophages by fatal pathogens can result in toxic responses. 2-hydroxyethyl methacrylate (HEMA), which is a hydrophilic monomer, is used in dental adhesive reagents and composite resins as well as biocompatible hydrogels. The mechanisms underlying the genotoxicity engendered by HEMA-induced apoptosis that leads to cytotoxicity remain unclear. Accordingly, this study was conducted to clarify such mechanisms. The results showed that HEMA induced cell toxicity in RAW264.7 macrophages depending on the concentration. A higher HEMA concentration was associated with a higher level of apoptosis and genotoxicity. Moreover, HEMA induced a concentration-dependent increase in mitochondrial dysfunction and the intrinsic caspase pathway, including the activation of caspase-3 and caspase-9. HEMA was also found to upregulate intracellular reactive oxygen species generation and to decrease the activity of antioxidant enzymes, including superoxide dismutase and catalase. Taken together, the mitochondrial-dependent intrinsic caspase pathway and intracellular reactive oxygen species accumulation were found to mediate HEMA-induced genotoxicity and apoptosis, leading to cytotoxicity in RAW264.7 macrophages.

Nd:YVO4 laser groove treatment can improve the shear bond strength between dental PEEK and adhesive resin cement with an adhesive system.

The purpose of this study was to investigate the effect of various surface treatments on the shear bond strength between dental polyetheretherketone (PEEK) and adhesive resin cement. Two hundred and forty specimens were randomly classified into four groups: no treatment, sandblasted, sulfuric-acid-etched, and laser-grooved treatment. Each group was classified into two adhesive resin cement subgroups. Surface roughness, water contact angle, shear bond strength, and failure mode were measured; SEM and XPS results were obtained. The data were statistically analyzed using one-way or two-way analysis of variance and Tukey's honest significant difference test (α=0.05). Laser-grooved PEEK surface showed regular grooves and carbonization by thermal degradation; the surface roughness as well as water contact angle of were the highest in all groups. Shear bond strength values were significantly higher in the laser-groove-treated and sulfuric-acid-etched groups. Laser-groove-treated specimens showed cohesive failure. Laser-grooved treatment can improve shear bond strength between PEEK and adhesive resin cement.

Exploring the use of a Ruthenium complex incorporated into a methacrylate-based dental material for antimicrobial photodynamic therapy.

To evaluate the effects of a blue light photosensitizer (PS), Ruthenium II complex (Ru), on the chemical, physical, mechanical, and antimicrobial properties of experimental dental resin blends. The experimental resin (BisEMA, TEEGDMA, HPMA, ethanol, and photoinitiator) was loaded with Ru at 0.00%, 0.07%, 0.14%, 0.28%, 0.56%, 1.12%, 1.2%, 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10% w/w. Samples were evaluated for the degree of conversion (DC) after 30 and 60 s curing-time (n = 6). Selected formulations (0.00%, 0.28%, 0.56%, 1.12%) were further tested for shear bond strength (SBS) (n = 15); flexural strength (FS) (n = 12); and antimicrobial properties (CFUs), in dark and light conditions. These latter tests were performed on specimens stored for 24-h or 2-month in 37°C water. Water sorption (WS) and solubility (SL) tests were also performed (n = 12). Data were analyzed either by a one- or two-factor general linear model (α = 0.05). Overall, Ru concentration above 1.2% resulted in reduced DC. In SBS results, only the 1.12%Ru resin blend samples had statistically lower values compared to the 0.00%Ru resin blend at 24-h storage (p = 0.004). In addition, no differences in SBS were detected among the experimental groups after 2-month storage in water. Meanwhile, FS increased for all experimental groups under similar aging conditions (p < 0.001). Antimicrobial properties were improved upon inclusion of Ru and application of light (p < 0.001 for both) at 24-h and 2-month storage. Lastly, no detectable changes in WS or SL were observed for the Ru-added resins compared to the 0.00%Ru resin blend. However, the 0.28% Ru blend presented significantly higher WS compared to the 0.56% Ru blend (p = 0.007). Stable SBS, improved FS, and sustained antimicrobial properties after aging gives significant credence to our approach of adding the Ruthenium II complex into dental adhesive resin blends intended for an aPDT approach.

Application of silver nanoparticles in situ synthesized in dental adhesive resin

The objective was to apply the silver nanoparticles (AgNPs) in situ synthesized in an adhesive resin. Silver 2-ethylhexanoate was added into Clearfil SE Bond (Kuraray Inc.) to form 0.0% Ag, 0.1% Ag, 0.2% Ag groups. The size and distribution of AgNPs formed in light-cured adhesive resin disks were observed by TEM. The degree of conversion was evaluated by FTIR. The cytotoxicity against human periodontal ligament fibroblasts was examined by CCK-8 assay. After each water-storage time (1 week, 4 weeks, 3 months, 12 months), biofilms of Streptococcus mutans on the resin disks were observed by SEM and tested for live/dead staining and colony-forming units. The average particle sizes of evenly dispersed AgNPs in the 0.1% Ag and 0.2% Ag groups were 10.9 ± 3.7 nm and 8.8 ± 4.2 nm, respectively. The incorporation of AgNPs did not compromise the degree of conversion and biocompatibility of the 0.1% Ag and 0.2% Ag groups. After 12 months of water storage, the antibacterial properties of 0.1% Ag and 0.2% Ag groups were much higher than that of 0.0% Ag group. The in situ synthesis of AgNPs might be a promising technique in the antibacterial modification of dental adhesive resin.

Allergic Reaction to Zirconia Ceramic Bridge Cementation Using a Dental Adhesive Resin Cement: a Case Report

Allergic Reaction to Zirconia Ceramic Bridge Cementation Using a Dental Adhesive Resin Cement: a Case Report

Titanium dioxide nanotubes with triazine-methacrylate monomer to improve physicochemical and biological properties of adhesives

ObjectiveFormulate experimental adhesives containing titanium dioxide nanotubes (nt-TiO2) or titanium dioxide nanotubes with a triazine-methacrylate monomer (nt-TiO2:TAT) and evaluate the effect of these fillers on the physical, chemical, and biological properties of the adhesives. MethodsFirst, nt-TiO2 were synthesized via a hydrothermal method. The nt-TiO2 were mixed with a triazine-methacrylate monomer (TAT) to formulate nt-TiO2:TAT, which were characterized by transmission electron microscopy (TEM). The nt-TiO2, TAT, and nt-TiO2:TAT were evaluated via Fourier Transform Infrared, Ultraviolet–visible, and micro-Raman spectroscopies. An experimental adhesive resin was formulated with bisphenol A glycerolate dimethacrylates, 2-hydroxyethyl methacrylate, and photoinitiator/co-initiator system. nt-TiO2 or nt-TiO2:TAT were incorporated at 2.5 wt.% and 5 wt.% in the adhesive. The base resin without nt-TiO2 or nt-TiO2:TAT was used as a control group. The adhesives were evaluated for antibacterial activity, cytotoxicity, polymerization kinetics, degree of conversion (DC), Knoop hardness, softening in solvent (ΔKHN%), ultimate tensile strength (UTS), 24 h- and 1 year- microtensile bond strength (μ-TBS). ResultsTEM confirmed the nanotubular morphology of TiO2. FTIR, UV–vis, and micro-Raman analyses showed the characteristic peaks of each material, indicating the impregnation of TAT in the nt-TiO2. Adhesives with nt-TiO2:TAT showed antimicrobial activity against biofilm formation compared to control (p < 0.05), without differences in the viability of planktonic bacteria (p > 0.05). All groups showed high percentages of pulp cell viability. The polymerization kinetics varied among groups, but all presented DC above 50%. The addition of 5 wt.% of nt-TiO2 and both groups containing nt-TiO2:TAT showed higher values ​​of Knoop hardness compared to the control (p < 0.05). The groups with nt-TiO2:TAT presented lower ΔKHN% (p < 0.05) and higher UTS (p < 0.05) than the control group. After one year, the group with 5 wt.% of nt-TiO2, as well as both groups containing nt-TiO2:TAT, showed higher μ-TBS than the control (p < 0.05). SignificanceThe mixing of a triazine-methacrylate monomer with the nt-TiO2 generated a filler that improved the physicochemical properties of the adhesive resins and provided antibacterial activity, which could assist in preventing carious lesions around tooth-resin interfaces. The set of physical, chemical, and biological properties of the formulated polymer, together with the greater stability of the bond strength over time, make nt-TiO2:TAT a promising filler for dental adhesive resins.

Effect of hydroxyapatite and 45S5 bioactive glass addition on a dental adhesive resin cement

AbstractObjectiveThis study evaluates the mechanical, physical, and biological properties of resin‐based dental cement (RelyX ARC, 3M ESPE) incorporated with hydroxyapatite and 45S5 bioactive glass.MethodsBioactive glass (45S5) and hydroxyapatite (HA) were added to cement in different proportions (10 wt% and 20 wt%). Three‐point flexural strength, microhardness, surface roughness, film thickness, contact angle, and color were evaluated. Cytotoxicity in human osteoblasts culture (MG63) was evaluated. Statistical analysis was performed using one‐way and two‐way ANOVA and Tukey tests (α &lt; 0.05).ResultsThe addition of HA and 45S5 bioactive glass reduced the flexural strength of the composite. However, the resistance value was greater than the minimum values of the ISO standard. Film thickness was below the maximum values, except for the 20% HA. The contact angle was constant at 24 hours and 14 days, except for 10% 45S5 group, which presented a significant decrease in mean contact angle. Cellular viability for all groups increased from the first to the 14th day. Additionally, the cellular viability was above 50%.ConclusionsIn vitro incorporation of 45S5 bioactive glass on resin cement resulted in a promising luting dental material with adequate mechanical properties, thin film thickness, improved wettability, and adequate biocompatibility.

SPLINTING WITH 4 META/MMA-TBB SELF CURE ADHESIVE SYSTEM – A NOVEL APPROACH

A variety of treatment modalities, for mobility of teeth. To treat the mandibular anterior mobile teeth is the most challenging tasks; to splint the mandibular teeth is appreciable approach and is the fastest, simplest and most predictable. This case report presents a successfully accomplished stabilization of mandibular teeth with grade II mobility with resorption of bone seen radiographically, by using 4-META/MMA-TBB self-cure dental adhesive resin (Cand B bond). This present treatment modality offers a conservative, aesthetic and noninvasive treatment which can be considered as a longlasting treatment. The purpose of this report is to present a case of successful stabilization of teeth by using Cand B bond.

Zinc-based particle with ionic liquid as a hybrid filler for dental adhesive resin

ObjectivesThe aim of this study was to evaluate the effect of a zinc-based particle with ionic liquid as filler for an experimental adhesive resin. MethodsThe ionic liquid 1-n-butyl-3-methylimidazolium chloride (BMI.Cl) and zinc chloride (ZnCl2) were used to synthesize 1-n-butyl-3-methylimidazolium trichlorozincate (BMI.ZnCl3), which was hydrolyzed under basic conditions to produce the simonkolleite (SKT) particles. SKT was analyzed by scanning electron microscopy and transmission electron microscopy. An experimental adhesive resin was formulated and SKT was incorporated at 1, 2.5, or 5 wt.% in the adhesive. One group without SKT was a control group. The antibacterial activity against Streptococcus mutans, cytotoxicity, degree of conversion (DC), ultimate tensile strength (UTS), softening in solvent, and microtensile bond strength (μ-TBS) were investigated. ResultsSKT prepared from the ionic liquid BMI.ZnCl3 presented a hexagonal shape in the micrometer scale. SKT addition provided antibacterial activity against biofilm formation of S.mutans and planktonic bacteria (p < 0.05). There were no differences in pulp cells’ viability (p > 0.05). The DC ranged from 62.18 (±0.83)% for control group to 64.44 (±1.55)% for 2.5 wt.% (p > 0.05). There was no statistically significant difference among groups for UTS (p > 0.05), softening in solvent (p > 0.05), and 24 h or 6 months μ-TBS (p > 0.05). ConclusionsThe physicochemical properties of adhesives were not affected by SKT incorporation, and the filler provided antibacterial activity against S. mutans without changes in the pulp cells' viability. This hybrid zinc-based particle with ionic liquid coating may be a promising filler to improve dental restorations. Clinical relevanceA filler based on a zinc-derived material coated with ionic liquid was synthesized and added in dental adhesives, showing antibacterial activity and maintaining the other properties analyzed. SKT may be a promising filler to decrease the biofilm formation around resin-based restorative materials.

Sorption, solubility and cytotoxicity of novel antibacterial nanofilled dental adhesive resins

Dental adhesives hydrolyze in the mouth. This study investigated the water sorption (SOR), solubility (SOL) and cytotoxicity (CYTO) of experimental adhesives containing nitrogen-doped titanium dioxide nanoparticles (N_TiO2). Specimens (n = 15/group [SOR, SOL]; n = 10/group [CYTO]) of unaltered Clearfil SE Protect (CSP), OptiBond Solo Plus (OSP), Adper Scotchbond (ASB) and experimental adhesives (OSP + 25% or 30% of N_TiO2) were fabricated, desiccated (37 °C) and tested for SOR and SOL according to ISO Specification 4049 (2009). CYTO specimens were UV-sterilized (8 J/cm2) and monomer extracted in growth medium (1, 3 or 7 days). Human pulp cells were isolated and seeded (0.5 × 104) for MTT assay. SOR and SOL data was analyzed using GLM and SNK (α = 0.05) and CYTO data was analyzed with Kruskal–Wallis and SNK tests (α = 0.05). SOR and SOL values ranged from 25.80 μg/mm3 (30% N_TiO2) to 28.01 μg/mm3 (OSP) and 23.88 μg/mm3 (30% N_TiO2) to 25.39 μg/mm3 (25% N_TiO2). CYTO results indicated that pulp cells exposed to experimental materials displayed comparable viabilities (p > 0.05) to those of OSP. Experimental materials displayed comparable SOR, SOL and CYTO values (p > 0.05) when compared to unaltered materials. N_TiO2 incorporation have not adversely impacted SOR, SOL and CYTO properties of unaltered adhesives.

Niobium silicate particles promote in vitro mineral deposition on dental adhesive resins

ObjectiveThis study aims to analyze the addition of niobium silicate particles to dental adhesive resins and evaluate its physicomechanical and biological properties. Methods: The SiNb particles were produced by the sol-gel route and presented a mean particle size of 2.1 μm and a specific surface area of 616,96m2/g. An experimental adhesive resin was formulated with 66 wt% Bisphenol A-Glycidyl Methacrylate and 33 wt% Hydroxyethyl methacrylate with diphenyl(2,4,6-trimethyl benzoyl)phosphine oxide as the photoinitiator. The SiNb particles were incorporated into the adhesive resins in 1 wt% (SiNb1%) and 2 wt% (SiNb2%) concentration. A control group (SiNb0%) without the addition of particles was used. The developed adhesives were evaluated by their polymerization kinetics, refractive index, softening in solvent, cytotoxicity, mineral deposition, ultimate tensile strength, and micro shear bond strength. ResultsThe refractive index range was increased by the addition of niobium silicate particles. No statistically significant difference was found between groups in the degree of conversion,.softening in solvent analysis, cytotoxicity and ultimate tensile strength. The deposition of minerals increased after immersion of specimens in SBF after 14 days on the SiNb2%. The SiNb2% group showed high micro shear bond strength values, reaching 33.87 MPa. Conclusion: In the present study, the addition of 2 wt% of niobium silicate into dental adhesive resins promoted the mineral deposition with increased bond strength without affecting other material properties. Clinical significance: Bioactive fillers must maintain the physical-chemical properties of dental adhesives, guaranteeing their clinical performance. Niobium silicate particles could promote the remineralization of dentin hard tissues without compromising the physico-mechanical properties on these materials.

MOF-Based Erodible System for On-Demand Release of Bioactive Flavonoid at the Polymer-Tissue Interface.

Plant-derived compounds incite applications virtually on every biomedical field due to the expedient antioxidant, anti-inflammatory and antimicrobial properties in conjunction with a natural character. Here, quercetin (QCT), a flavonoid with therapeutic potentials relevant to the oral environment, was encapsulated within metal-organic frameworks (MOFs) to address the concept of on-demand release of phytochemicals at the biointerface. We verified the applicability of a microporous MOF (ZIF-8) as a controlled-release system for QCT, as well as investigated the incorporation of QCT@ZIF-8 microparticles into a dental adhesive resin for desirable therapeutic capabilities at the tooth-restoration interface. QCT was encapsulated within the frameworks through a water-based, one-step synthetic process. The resulting QCT@ZIF-8 microparticles were characterized with respect to chemical composition, crystal structure, thermal behavior, micromorphology, and release profile under acidic and physiological conditions. A model dental adhesive formulation was enriched with the bioactive microparticles; both the degree of conversion (DC) of methacrylic double bonds and the polymer thermal behavior were accounted for. The results confirm that crystalline QCT@ZIF-8 microparticles with attractive loading capacities, submicron sizes, high thermal stability and responsiveness to environmental pH change were successfully manufactured. The concentration of QCT@ZIF-8 in the resin system was a key factor to maintain an optimal DC plateau and rate of polymerization. Essentially, one-step encapsulation of QCT in biocompatible ZIF-8 matrices can be easily achieved, and QCT@ZIF-8 microparticles proved as smart platforms to carry bioactive compounds with potential use to prevent microbial and enzymatic degradation of hard tissues and extracellular matrix components.

Advanced characterization of surface-modified nanoparticles and nanofilled antibacterial dental adhesive resins

Nanotechnology can improve the performance of dental polymers. The objective of this study was to modify the surfaces of nanoparticles with silanes and proteins, characterize nanoparticles’ agglomeration levels and interfaces between nanoparticles and the polymeric matrix. Undoped (n-TiO2), nitrogen-doped (N_TiO2) and nitrogen-fluorine co-doped titanium dioxide nanoparticles (NF_TiO2) were synthesized and subjected to surface modification procedures in preparation for Small-Angle X-Ray Scattering (SAXS) and Small-Angle Neutron Scattering (SANS) characterizations. Experimental adhesives were manually synthesized by incorporating 20% (v/v) of n-TiO2, N_TiO2 or NF_TiO2 (as-synthesized or surface-modified) into OptiBond Solo Plus (OPTB). Specimens (n = 15/group; d = 6.0 mm, t = 0.5 mm) of OPTB and experimental adhesives were characterized using Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS), 2-D ToF-SIMS chemical imaging and SANS. SAXS results indicated that surface-modified nanoparticles displayed higher scattering intensities in a particle-size dependent manner. ToF-SIMS results demonstrated that nanoparticles’ incorporation did not adversely impact the parental polymer. 2-D ToF-SIMS chemical imaging demonstrated the distribution of Ti+ and confirmed nitrogen-doping levels. SANS results confirmed nanoparticles’ functionalization and revealed the interfaces between nanoparticles and the polymer matrix. Metaloxide nanoparticles were successfully fabricated, incorporated and covalently functionalized in a commercial dental adhesive resin, thereby supporting the utilization of nanotechnology in dentistry.

Optimization of a real-time high-throughput assay for assessment of Streptococcus mutans metabolism and screening of antibacterial dental adhesives

ObjectiveThe present work shows the optimization of a high-throughput bioluminescence assay to assess the metabolism of intact Streptococcus mutans biofilms and its utility as a screening method for nanofilled antibacterial dental materials. MethodsThe assay was optimized by monitoring changes in bioluminescence mediated by variation of the experimental parameters investigated (growth media and sucrose concentration, inoculum:D-Luciferin ratio, dilution factor, inoculum volume, luminescence wavelength, replicate and luciferase metabolic activity). Confocal microscopy was then used to demonstrate the impact of biofilm growth conditions on the 3-D distribution of extracellular polymeric substance (EPS) within Streptococcus mutans biofilms and its implications as confounding factors in high-throughput studies (HTS). ResultsRelative Luminescence Unit (RLU) values from the HTS optimization were analyzed by multivariate ANOVA (α= 0.05) and coefficients of variation, whereas data from 3-D structural parameters and RLU values of biofilms grown on experimental antibacterial dental adhesive resins were analyzed using General Linear Models and Student–Newman–Keuls post hoc tests (α= 0.05). Confocal microscopy demonstrated that biofilm growth conditions significantly influenced the quantity and distribution of EPS within the 3-D structures of the biofilms. An optimized HTS bioluminescence assay was developed and its applicability as a screening method in dentistry was demonstrated using nanofilled experimental antibacterial dental adhesive resins. SignificanceThe present study is anticipated to positively impact the direction of future biofilm research in dentistry, because it offers fundamental information for the design of metabolic-based assays, increases the current levels of standardization and reproducibility while offering a tool to decrease intra-study variability.