High-Performance Bioinspired Microspheres for Boosting Dental Adhesion.

Dental adhesives are widely used in daily practice for minimally invasive restorative dentistry but suffer from bond degradation and biofilm attack. Bio-inspired by marine mussels having excellent surface-adhesion capability and high chemical affinity of polydopamine (PDA) to metal ions, herein, experimental zinc (Zn)-containing polydopamine-based adhesive formulation, further being referred to as "Zn-PDA@SiO2"-incorporated adhesive is proposed as a novel dental adhesive. Different Zn contents (5 and 10 mm) of Zn-PDA@SiO2 are prepared. Considering the synergistic effect of Zn and PDA, Zn-PDA@SiO2 not only presents excellent antibacterial potential and notably inhibits enzymatic activity (soluble and matrix-bound proteases), but also exhibits superior biocompatibility and biosafety in vitro/vivo. The long-term bond stability is substantially improved by adding 5 wt% 5 mm Zn-PDA@SiO2 to the primer. The aged bond strength of the experimentally formulated dental adhesives applied in self-etch (SE) bonding mode is 1.9 times higher than that of the SE gold-standard adhesive. Molecular dynamics calculations indicate the stable formation of covalent bonds, Zn-assisted coordinative bonds, and hydrogen bonds between PDA and collagen. Overall, this bioinspired dental adhesive provides an avenue technology for innovative biomedical applications and has already revealed promising perspectives for dental restorative dentistry.

Evaluation of the antibacterial activity of dental adhesive containing biogenic silver nanoparticles decorated nanographene oxide nanocomposites (Ag@nGO NCs) and effect on bond strength to dentine.

Our study aimed to evaluate the antibacterial activities and dentin bond strengths of silver nanoparticles (Ag NPs) and silver nano-graphene oxide nanocomposites (Ag@nGO NCs) produced by green and chemical synthesis methods added to the dental adhesive. Ag NPs were produced by green synthesis (biogenic) (B-Ag NPs) and chemical synthesis methods (C-Ag NPs) and deposited on nGO (nano-graphene oxide). Ag NPs and Ag@nGO NCs (0.05% w/w) were added to the primer and bond (Clearfil SE Bond). Group 1: control, Group 2: nGO, Group 3: B-Ag NPs, Group 4: B-Ag@nGO NCs, Group 5: C-Ag NPs, Group 6: C-Ag@nGO NCs. Streptococcus mutans (S. mutans) live/dead assay analysis, MTT metabolic activity test, agar disc diffusion test, lactic acid production, and colony forming units (CFUs) tests were performed. Bond strength values were determined by the microtensile bond strength test (µTBS). Failure types were determined by evaluating with SEM. Statistical analysis was performed using one-way ANOVA and two-way ANOVA (p < 0.05). There was a difference between the groups in the viable bacteria ratio and lactic acid production tests (p < 0.05). When the inhibition zone and S. mutans CFUs were evaluated, there was no difference between Group 3 and Group 4 (p > 0.05), but there was a difference between the other groups (p < 0.05). When the metabolic activity of S. mutans was evaluated, there was a difference between Group 1 and other groups, and between Group 2 and Group 5, and Group 6 (p < 0.05). There was no difference between the groups in the µTBS values (p > 0.05). As a result, although the antibacterial activity of B-Ag NPs and B-Ag@nGO Ag NPs obtained by green synthesis is lower than that of chemically synthesis obtained C-Ag NPs and C-Ag@nGO NCs, they provided higher antibacterial activity compared to the control group and did not reduce µTBS. The addition of biogenic Ag NPs to the adhesive system increased the antibacterial effect by maintaining the bond strength of the adhesive. Antibacterial adhesives can increase the restoration life by protecting the tooth-adhesive interface.

Engineering Interfacial Integrity with Hydrolytic-Resistant, Self-Reinforcing Dentin Adhesive.

The leading cause of composite restoration failure is secondary caries, and although caries is a multifactorial problem, weak, damage-prone adhesives play a pivotal role in the high susceptibility of composite restorations to secondary caries. Our group has developed synthetic resins that capitalize on free-radical polymerization and sol-gel reactions to provide dental adhesives with enhanced properties. The resins contain γ-methacryloxypropyltrimethoxysilane (MPS) as the Si-based compound. This study investigated the properties of methacrylate-based resins containing methacryloxymethyltrimethoxysilane (MMeS) as a short-chain alternative. The degree of conversion (DC), polymerization kinetics, water sorption, mechanical properties, and leachates of MMeS- and MPS-resins with 55 and 30 wt% BisGMA-crosslinker were determined. The formulations were used as model adhesives, and the adhesive/dentin (a/d) interfaces were analyzed using chemometrics-assisted micro-Raman spectroscopy. The properties of the 55 wt% formulations were comparable. In the 30 wt% BisGMA formulations, the MMeS-resin exhibited faster polymerization, lower DC, reduced leachates, and increased storage and loss moduli, glass transition (Tg), crosslink density, and heterogeneity. The spectroscopic results indicated a comparable spatial distribution of resin, mineralized, and demineralized dentin across the a/d interfaces. The hydrolytically stable experimental short-chain-silane-monomer dental adhesive provides enhanced mechanical properties through autonomous strengthening and offers a promising strategy for the development of restorative dental materials with extended service life.

Evaluation of the bonding effectiveness of a universal adhesive to the plasma-activated dentin surface.

This study aimed to evaluate the effect of non-thermal atmospheric pressure plasma on the bond strength of a universal adhesive used in etch-and-rinse mode. Dentin surfaces were etched with phosphoric acid and samples were divided into groups exposed to either dry bonding, plasma-dried bonding, plasma-dried and rewetted bonding, or wet bonding (n  =  10). Dentin surfaces of the plasma-dried specimens were treated with a plasma jet before the adhesive procedure. After application, composite blocks were built, and specimens were subjected to micro-tensile bond strength testing after 24 h and after 10,000 thermal cycles. The hybrid layer formation was evaluated by micro-Raman spectral analysis; the resin-dentin interface was analyzed by scanning electron microscopy. One-way ANOVA and Tukey's post hoc multiple comparison tests were used to statistically analyze the data. The bond strength values of the plasma-dried bonding groups were statistically higher than the non-plasma-treated groups both before and after aging. After the thermal cycles, bond strength values decreased significantly only in the wet bonding group. Micro-Raman spectral analysis revealed that plasma-drying increased adhesive penetration, especially hydrophobic monomer infiltration. This may increase the mechanical properties and durability of the resin-dentin interface, provide long-term stability, and improve the polymerization rate of the adhesive layer.

Antibacterial effect, cytotoxicity, and bond strength of a modified dental adhesive containing silver nanoparticles.

This study aimed to evaluate the antibacterial effect, cytotoxicity, and microtensile bond strength of an adhesive system containing silver nanoparticles (NAg). NAg was synthesized and incorporated (500 and 1000 ppm) into Scotchbond Multi-Purpose (SBMP) primer and bond. A microtensile bond test (µTBS) was performed after 24 h and 1 year. The adhesive interface was characterized using a confocal Raman microscope. The antibacterial activity was assessed using agar diffusion and biofilm inhibition assays (S. mutans). MTT assay was used to assess the cytotoxicity of NAg-conditioned culture media on human dental pulp stem cells (hDPSCs). The results were statistically analyzed using analysis of variance and Tukey's tests (α = .01). Incorporating 500 and 1000 ppm of NAg in the SBMP did not affect the µTBS after 24 h (p > 0.05). However, in the 1 year evaluation, 500 ppm presented the highest µTBS values (p < 0.05). The addition of NAg at 500 and 1000 ppm in the primer and bond led to larger inhibition halos and colony-forming units than the control (p < 0.05). For the unpolymerized and polymerized groups, the combination of primer and bond presented the highest cytotoxic effects on hDPSCs (p < 0.05). In conclusion, incorporating 500 or 1000 ppm of NAg into an etch-and-rinse adhesive system led to an antibacterial effect without altering the cytotoxicity. SBMP at 500 ppm presented a higher µTBS at 1 year.

Comparative Evaluation of the Repair Bond Strength of Dental Resin Composite after Sodium Bicarbonate or Aluminum Oxide Air-Abrasion.

The dental prophylactic cleaning of a damaged resin-based composite (RBC) restoration with sodium bicarbonate can change the surface characteristics and influence the repair bond strength. The purpose of this study was to compare the effect of sodium bicarbonate (SB) and aluminum oxide (AO) surface treatments on the microtensile bond strength (µTBS) of repaired, aged RBC. Bar specimens were prepared from microhybrid RBC and aged in deionized water for 8 weeks. Different surface treatments (AO air-abrasion; SB air-polishing), as well as cleaning (phosphoric acid, PA; ethylene-diamine-tetraacetic-acid, EDTA) and adhesive applications (single bottle etch-and-rinse, ER; universal adhesive, UA), were used prior to the application of the repair RBC. Not aged and aged but not surface treated RBCs were used as positive and negative controls, respectively. The repaired blocks were cut into sticks using a precision grinding machine. The specimens were tested for tensile fracture and the µTBS values were calculated. Surface characteristics were assessed using scanning electron microscopy. AO-PA-UA (62.6 MPa) showed a 20% increase in µTBS compared to the NC (50.2 MPa), which proved to be the most significant. This was followed by SB-EDTA-UA (58.9 MPa) with an increase of 15%. In addition to AO-PA-UA, SB-EDTA-UA could also be a viable alternative in the RBC repair protocol.

L-arginine-containing mesoporous silica nanoparticles embedded in dental adhesive (Arg@MSN@DAdh) for targeting cariogenic bacteria.

Dental caries is the major biofilm-mediated oral disease in the world. The main treatment to restore caries lesions consists of the use of adhesive resin composites due to their good properties. However, the progressive degradation of the adhesive in the medium term makes possible the proliferation of cariogenic bacteria allowing secondary caries to emerge. In this study, a dental adhesive incorporating a drug delivery system based on L-arginine-containing mesoporous silica nanoparticles (MSNs) was used to release this essential amino acid as a source of basicity to neutralize the harmful acidic conditions that mediate the development of dental secondary caries. The in vitro and bacterial culture experiments proved that L-arginine was released in a sustained way from MSNs and diffused out from the dental adhesive, effectively contributing to the reduction of the bacterial strains Streptococcus mutans and Lactobacillus casei. Furthermore, the mechanical and bonding properties of the dental adhesive did not change significantly after the incorporation of L-arginine-containing MSNs. These results are yielding glimmers of promise for the cost-effective prevention of secondary caries.

Evaluation of the ability of adhesives with antibacterial and remineralization functions to prevent secondary caries in vivo.

OBJECTIVE: The bonding interface of dental filling therapy is the weak point in resisting secondary caries. Adhesives containing nanoparticles of amorphous calcium phosphate (NACP) and dimethylaminohexadecyl methacrylate (DMAHDM) have been demonstrated in vitro to prevent bacteria from producing acid and to promote tooth remineralization. The present study aimed to evaluate the efficacy of adhesive with NACP and DMAHDM to prevent secondary caries in vivo. MATERIALS AND METHODS: Artificial cavities were created on the first molar on both sides of the maxillary in a rat model. One side was treated with adhesive containing NACP + DMAHDM, while on the other side, a commercial adhesive served as control. After 24 days of cariogenic feeding, the degree of secondary caries was evaluated by micro-CT and a modified Keyes scoring method. Quantitative real-time PCR (qPCR) and colony-forming unit (CFU) counts were used to evaluate the antibacterial efficacy of the materials. Biocompatibility was also investigated. RESULTS: In the rat model, the adhesive with NACP + DMAHDM showed excellent biocompatibility and effectively decreased the amount of bacteria. The experimental group demonstrated excellent remineralization effectiveness, with a lower modified Keyes score and mineral loss of 34.16 ± 2.13 vol% µm, compared with 77.44 ± 7.22 vol% µm in the control group, according to micro-CT (P < 0.05), showing excellent capacity to inhibit secondary caries. CONCLUSIONS: The NACP-DMAHDM-containing adhesive exhibited good performance in preventing secondary caries in vivo. CLINICAL RELEVANCE: Adhesives containing NACP and DMAHDM have great potential for use in clinical dentistry to prevent secondary caries by inhibiting bacterial growth and promoting remineralization.

Novel calcium phosphate ion-rechargeable and antibacterial adhesive to inhibit dental caries.

OBJECTIVES: This study aimed to develop an antibacterial and calcium (Ca) and phosphate (P) rechargeable adhesive and investigate the effects of dimethylaminododecyl methacrylate (DMAHDM) and nanoparticles of amorphous calcium phosphate (NACP) on dentin bonding, biofilm response, and repeated Ca and P ion recharge and re-release capability for the first time. MATERIALS AND METHODS: Pyromellitic glycerol dimethacrylate (PMGDM), ethoxylated bisphenol A dimethacrylate (EBPADMA), 2-hydroxyethyl methacrylate (HEMA), and bisphenol A glycidyl dimethacrylate (BisGMA) formed the adhesive (PEHB). Three groups were tested: (1) Scotchbond (SBMP, 3 M) control, (2) PEHB + 30% NACP, and (3) PEHB + 30% NACP + 5% DMAHDM. Specimens were tested for dentin shear bond strength, and Ca and P ion release, recharge, and re-release. Biofilm lactic acid production and colony-forming units (CFU) on resins were analyzed. RESULTS: The four groups had similar dentin shear bond strengths (p > 0.1). Adhesive with DMAHDM showed significant decrease in metabolic activity, lactic acid production, and biofilm CFU (p < 0.05). The adhesives containing NACP released high levels of Ca and P ions initially and after being recharged. CONCLUSION: This study developed the first Ca and P ion-rechargeable and antibacterial adhesive, achieving strong antibacterial activity and Ca and P ion recharge and re-release for long-term remineralization. CLINICAL RELEVANCE: Considering the restoration-tooth bonded interface being the weak link and recurrent caries at the margins being the primary reason for restoration failures, this novel calcium phosphate-rechargeable and antibacterial adhesive is promising for a wide range of tooth-restoration applications to inhibit caries.

Autonomous-Strengthening Adhesive Provides Hydrolysis-Resistance and Enhanced Mechanical Properties in Wet Conditions.

The low-viscosity adhesive that is used to bond composite restorative materials to the tooth is readily damaged by acids, enzymes, and oral fluids. Bacteria infiltrate the resulting gaps at the composite/tooth interface, demineralize the tooth, and further erode the adhesive. This paper presents the preparation and characterization of a low-crosslink-density hydrophilic adhesive that capitalizes on sol-gel reactions and free-radical polymerization to resist hydrolysis and provide enhanced mechanical properties in wet environments. Polymerization behavior, water sorption, and leachates were investigated. Dynamic mechanical analyses (DMA) were conducted using water-saturated adhesives to mimic load transfer in wet conditions. Data from all tests were analyzed using appropriate statistical tests (α = 0.05). The degree of conversion was comparable for experimental and control adhesives at 88.3 and 84.3%, respectively. HEMA leachate was significantly lower for the experimental (2.9 wt%) compared to control (7.2 wt%). After 3 days of aqueous aging, the storage and rubbery moduli and the glass transition temperature of the experimental adhesive (57.5MPa, 12.8MPa, and 38.7 °C, respectively) were significantly higher than control (7.4MPa, 4.3 MPa, and 25.9 °C, respectively). The results indicated that the autonomic sol-gel reaction continues in the wet environment, leading to intrinsic reinforcement of the polymer network, improved hydrolytic stability, and enhanced mechanical properties.

Non-Invasive Optical Coherence Tomography Data-Based Quantitative Algorithm for the Assessment of Residual Adhesive on Bracket-Removed Dental Surface.

The aim of this study was to quantitatively assess the residual adhesive on orthodontic ceramic bracket-removed dental surface. In orthodontic process, ceramic bracket was repeated debonding physically, then the adhesive remained on the dental surface. The residual adhesive caused a lack of adhesive strength between dental and ceramic bracket. Since commonly used adhesive in orthodontics is translucent, residual adhesive is hard to be detected with conventional microscopes. Therefore, 1310 nm center wavelength swept-source OCT system based on laboratory customized image processing algorithm was used for the precise detection of residual adhesive on tooth surface. The algorithm separates residual adhesive from dental surface by comparing the height of adjacent B-scan images, while providing color-scaled images emphasizing the thickness information of residual adhesive. Finally, the acquired results were compared with microscopic and adhesive remnant index scoring gold standards, while the comparison confirmed the potential merits and the improvements of the proposed method over gold standards.

Morpho-functional effects of different universal dental adhesives on human gingival fibroblasts: an in vitro study.

To analyze the effects of four universal adhesives (Optibond Solo Plus-OB, Universal Bond-UB, Prime&Bond Active-PBA, FuturaBond M + -FB) on human gingival fibroblasts in terms of cytotoxicity, morphology and function. After in vitro exposure for up to 48 h, fibroblast viability was determined by the MTT assay determined, morphology by phase-contrast microscopy and migration by the scratch wound assay. Expression levels of IL1ß, IL6, IL8, IL10, TNFα and VEGF genes were assessed by RT-PCR and their protein production by Western blot analysis. Apoptosis and cell cycle were analyzed by flow cytometry. OB and UB induced early morphological changes on fibroblasts (3 h) with extended cell death at 24 h/48 h. Gene expression of collagen type I and fibronectin increased fivefold compared with controls, elastin disappeared and elastase increased threefold, indicating gingival tissue tended to become fibrotic. Only UB and OB increased gene expression of inflammatory markers: IL1ß at 3 and 48 h (up to about three times), IL6 and IL8 at 3 h (up to almost four times) which corresponded to the increase of the activated form NF-kB. All adhesives showed an effect on the functionality of fibroblasts with cytotoxic effect time and concentration dependent. Among all the OB and UB adhesives, they showed the greatest cell damage. The in-depth analysis of the effects of universal adhesives and possible functional effects represents an important information for the clinician towards choosing the most suitable adhesive system.

Scoping review of trials evaluating adhesive strategies in pediatric dentistry: where do simplified strategies lie?

BACKGROUND: Adhesive restorations allow a conservative approach to caries management and are increasingly used as a restorative option in pediatric dentistry. Placement can be difficult in children because of the cooperation required for multiple bonding steps. Due to this, it is vital to assess if novel, simpler strategies have been featured in clinical trials and if clinical trials are researching the different existing adhesive strategies. METHODS: This review followed Preferred Reporting Items for Systematic Reviews and Meta-analysis adapted for Scoping Reviews (PRISMA-ScR) guidelines. PubMed/Medline, Cochrane Central, Scopus and EMBASE were used for systematic search, using free keywords and controlled search terms. Clinical trials of children requiring a restorative intervention which featured adhesive strategies were included. Only peer-reviewed trials of primary teeth restored with resin composites, published in the last 10-year period were eligible. Data charting was accomplished independently by two reviewers, and studies were summarized according to their date, type, intervention, sample size, observation period, outcomes and conclusions. Quality assessment was performed using Cochrane's Risk of Bias 2.0 tool. RESULTS: 700 potentially relevant references were found, which after a rigorous inclusion scheme, resulted in a total of 8 eligible clinical trials. Out of these, 7 were randomized clinical trials. Most trials featured a split-mouth design and the observation period ranged from 12 to 36 months. The trials evaluated interventions of two self-adhesive composites, two bulk-fill composites, two novel composites, one compomer and eight adhesives from different strategies. Most studies (4/8) included were judged to raise some concerns regarding risk of bias, while two were classified as high risk and two as low. CONCLUSION: Few studies comparing adhesive strategies were found, especially adhesives in sound substrates. The existing studies do not reflect all current approaches that could be used in pediatric dentistry. Further studies addressing bioactive composites and contemporary adhesives are necessary.

Allergic reaction from dental bonding material through nitrile gloves: Clinical case study and glove permeability testing.

OBJECTIVE: This study examines monomer permeation of commercial dental adhesive through nitrile-based gloves, and correlates findings with clinical case studies of dental students having localized skin eruptions following resin placement on a gloved hand to manipulate composite. METHODS: Three dental students self-reported presenting itchy, red skin lesions underneath the area where they placed uncured adhesive resin on a nitrile-gloved hand. Histories and cursory examinations were performed in the Department of Dermatology at The Medical College of Georgia. Infrared spectroscopic methods were used to determine permeation times of known monomer components of commercial adhesive material used through nitrile glove. Monomer permeation times were correlated with the time when the commercial adhesive first applied and penetrated through the glove. RESULTS: Assessment by the dermatologist concluded that the reporting students had occupational contact dermatitis resulting from components of the adhesive permeating through the barrier glove. Permeation times of neat monomer components of the adhesive resin varied over a wide range, with lower molecular weight showing faster pass-through times. Spectroscopic interpretation indicated that the probable causative agent for the student's skin reaction was 2-hydroxyethyl methacrylate (HEMA). CONCLUSIONS: Probable correlation of the observed skin reaction sites was made with diffusion of HEMA in the uncured dental adhesive formulation through nitrile glove material. CLINICAL SIGNIFICANCE: All measures to prevent skin contact with uncured methacrylate-based resin components should be taken, including avoidance of resin permeation through a gloved hand. Sensitization to one type of methacrylate can result in sensitization to other types of resins within this family, significantly impacting the careers of both dental auxiliaries as well as clinicians.

Dentin bonding and physicochemical properties of adhesives incorporated with epigallocatechin-3-gallate.

The aim was to assess dentin adhesion and physicochemical properties of experimental etch-and-rinse and self-etch adhesives doped with epigallocatechin-3-gallate (EGCG), a well-known collagen crosslinker obtained from green tea (Camellia sinensis). Experimental adhesives were prepared without (0 wt%), with 0.1 or 0.5 wt% EGCG addition. Their degree of conversion was surveyed by FTIR, and bar-shaped specimens were tested to obtain flexural strength and modulus initially and after 1-week ethanol storage. Extracted human molars were prepared, bonded, and cut into resin-dentin sticks for microtensile bond strength test, which was conducted after 24 h or 6-month water storage. Statistical analyses were performed with two-way ANOVA and Tukey's test (p < 0.05). Degree of conversion outcomes depicted a significant polymerization reduction by the addition of EGCG in self-etch adhesive in both concentrations. However, only 0.1% reduced the conversion of etch-and-rinse adhesive. Flexural modulus and strength were significantly diminished (p < 0.05) by the addition of both concentrations of EGCG for the two model adhesives. Dentin-bond strength was reduced after aging with the addition of EGCG to self-etch adhesive. Nevertheless, 0.5% EGCG increased the bond strength of etch-and-rinse adhesive after aging, conversely to the significant reduction for EGCG-free control adhesive. In conclusion, EGCG at 0.5% provides optimal improvements on dentin bonding without altering final polymerization of a model etch-and-rinse adhesive.

Effect of 2% Chlorhexidine Following Acid Etching on Microtensile Bond Strength of Resin Restorations: A Meta-Analysis.

Background and Objectives: The aim of this systematic review was to examine the effect of 2% chlorhexidine following acid etching on the microtensile bond strength of resin restorations for different follow-up times. Materials and Methods: A thorough search of PubMed, Scopus, and Embase databases were conducted. In vitro experimental studies or in vivo studies published up to December 2018 with an experimental group treated with a 2% chlorhexidine solution following acid etching and a control group were included, wherein the final restoration used a resin composite in both the groups. Results: Twenty-one articles were identified for qualitative analysis and 18 for meta-analysis. The difference in the means of microtensile bond strength between the two groups was calculated for the different follow-up times. The differences were significant for 6 months (4.30 MPa; 95% CI 2.72-5.89), 12 months (8.41 MPa; 95% CI 4.93-11.88), and 2-5 years including aged and thermocycling samples (9.08 MPa; 95% CI 5.36-12.81). There were no significant differences for the type of adhesive used. A meta-regression model showed a significant effect of time on the microtensile bond strength. Conclusions: The application of a 2% chlorhexidine solution after acid etching increased the microtensile bond strength significantly for follow-up times of 6 months or more. The adhesive type had no influence.

Doxycycline-loaded nanotube-modified adhesives inhibit MMP in a dose-dependent fashion.

OBJECTIVES: This article evaluated the drug loading, release kinetics, and matrix metalloproteinase (MMP) inhibition of doxycycline (DOX) released from DOX-loaded nanotube-modified adhesives. DOX was chosen as the model drug, since it is the only MMP inhibitor approved by the U.S. Food and Drug Administration. MATERIALS AND METHODS: Drug loading into the nanotubes was accomplished using DOX solution at distinct concentrations. Increased concentrations of DOX significantly improved the amount of loaded DOX. The modified adhesives were fabricated by incorporating DOX-loaded nanotubes into the adhesive resin of a commercial product. The degree of conversion (DC), Knoop microhardness, DOX release kinetics, antimicrobial, cytocompatibility, and anti-MMP activity of the modified adhesives were investigated. RESULTS: Incorporation of DOX-loaded nanotubes did not compromise DC, Knoop microhardness, or cell compatibility. Higher concentrations of DOX led to an increase in DOX release in a concentration-dependent manner from the modified adhesives. DOX released from the modified adhesives did not inhibit the growth of caries-related bacteria, but more importantly, it did inhibit MMP-1 activity. CONCLUSIONS: The loading of DOX into the nanotube-modified adhesives did not compromise the physicochemical properties of the adhesives and the released levels of DOX were able to inhibit MMP activity without cytotoxicity. CLINICAL SIGNIFICANCE: Doxycycline released from the nanotube-modified adhesives inhibited MMP activity in a concentration-dependent fashion. Therefore, the proposed nanotube-modified adhesive may hold clinical potential as a strategy to preserve resin/dentin bond stability.

Efficacy of antimicrobial agents incorporated in orthodontic bonding systems: a systematic review and meta-analysis.

AIMS: The purpose of this study was to evaluate the efficacy of orthodontic bonding systems containing different antimicrobial agents, as well as the influence of antimicrobial agent incorporation in the bonding properties of these materials. METHODS: Eight databases were searched: PubMed (Medline), Web of Science, Scopus, Lilacs, Ibecs, BBO, Scielo and Google Scholar. Any study that evaluated antimicrobial activity in experimental or commercial orthodontic bonding systems was included. DATA EXTRACTION: Data were tabulated independently and in duplicated by two authors on pre-designed data collection form. DATA SYNTHESIS: The global analysis was carried out using a random-effects model, and pooled-effect estimates were obtained by comparing the standardised mean difference of each antimicrobial orthodontic adhesive with the respective control group. A p-value < .05 was considered as statistically significant. RESULTS: Thirty-two studies were included in the qualitative analysis; of these, 22 studies were included in the meta-analysis. Antimicrobial agents such as silver nanoparticles, benzalkonium chloride, chlorhexidine, triclosan, cetylpyridinium chloride, Galla chinensis extract, acid ursolic, dimethylaminododecyl methacrylate, dimethylaminohexadecyl methacrylate, 2-methacryloyloxyethyl phosphorylcholine, 1,3,5-triacryloylhexahydro-1,3,5-triazine, zinc oxide and titanium oxide have been incorporated into orthodontic bonding systems. The antimicrobial agent incorporation in orthodontic bonding systems showed higher antimicrobial activity than the control group in agar diffusion (overall standardised mean difference: 3.71; 95% CI 2.98 to 4.43) and optical density tests (0.41; 95% CI -0.05 to 0.86) (p < .05). However, for biofilm, the materials did not present antimicrobial activity (6.78; 95% CI 4.78 to 8.77). Regarding bond strength, the global analysis showed antimicrobial orthodontic bonding systems were statistically similar to the control. CONCLUSIONS: Although there is evidence of antibacterial activity from in vitro studies, clinical and long-term studies are still necessary to confirm the effectiveness of antibacterial orthodontic bonding systems in preventing caries disease.

Evaluation of the marginal integrity of a bioactive restorative material.

This in vitro study evaluated the marginal microleakage of a bioactive restorative with other restorative materials in standard Class V preparations. Sixty previously extracted, noncarious human molars were randomly assigned to 3 experimental groups (n = 20): a bioactive composite resin, a universal hybrid composite resin, and a resin-modified glass ionomer restorative. Class V cavities were prepared on the facial or lingual surface of each tooth so that coronal margins were located in enamel and apical margins in cementum (dentin). After the cavity preparations were restored with the appropriate material, the specimens were artificially aged in water baths. The root apices were sealed with utility wax, the tooth surfaces were coated with nail varnish to within 1 mm of the restoration, and specimens were immersed in 1% methylene dye solution for 8 hours. The teeth were invested in clear polymer resin, sectioned longitudinally, and examined under a stereomicroscope to assess dye penetration. Nonparametric scores indicated that microleakage was significantly greater at the apical margins than the coronal margins for all groups (P > 0.0001). The specimens restored with the bioactive material exhibited greater microleakage at both the coronal and apical margins than did specimens restored with the composite resin or resin-modified glass ionomer material, although the differences were not statistically significant (P > 0.05). Based on the results of the present study, the type of restorative material did not appear to have a significant influence on microleakage. Rather, the marginal position (coronal versus apical) of the restoration was the determining factor in microleakage.

Glutaraldehyde collagen cross-linking stabilizes resin-dentin interfaces and reduces bond degradation.

This study evaluated the stability of resin-dentin interfaces treated with glutaraldehyde-containing agents, and assessed collagen degradation in dentin matrices treated with Gluma. Microtensile bond strength (µTBS) was evaluated 24 h and 6 months after treatment with three desensitizers (Gluma Desensitizer, Gluma Desensitizer Power Gel, and MicroPrime G) and two etch-and-rinse adhesives (Comfort Bond & Desensitizer and iBond TE). Demineralized beams of human dentin were treated with water or Gluma, and the degradation of collagen in these beams was assessed by quantification of the dry mass loss and of the amount of hydroxyproline released from hydrolyzed specimens after 1 or 4 wk. All groups demonstrated significant reduction in µTBS after 6 months, except for Gluma Desensitizer and iBond TE groups, which showed decreases of 7.2% and 10.8%, respectively. The most prevalent failure mode was 'mixed'. Significantly less hydroxyproline was released from Gluma-treated beams than from control beams after 4 wk. Beams treated with Gluma yielded significantly less dry mass loss than did beams in the control group. Collagen cross-linking with glutaraldehyde-containing agents may assist in the stabilization of resin-dentin bonds by reducing the amount of collagen solubilized from dental matrices in the hybrid layer. In turn, this may contribute to the preservation of adhesive interfaces.