Avaliação das propriedades de um sistema adesivo modificado por partículas de vidro bioativas / Evaluation of the properties of an adhesive system modified by bioactive glass particles

O objetivo desse estudo foi avaliar as propriedades de um sistema adesivo modificado com a incorporação de partículas de vidro bioativas (SCHOTT Bioactive Glass) em duas diferentes concentrações (0,5 e 1%). Foram avaliados a resistência de união da interface adesiva, o grau de conversão e a atividade antibacteriana, além da análise por meio do Estereomicroscópio e Microscópio Eletrônico de Varredura (MEV). Os adesivos foram divididos em três grupos: ASB - Adesivo Single Bond 2 (3M-ESPE) sem a incorporação de partículas bioativas, ASB0,5 ­ Adesivo Single Bond 2 com a incorporação de partículas bioativas na concentração de 0,5% e ASB1 ­ Adesivo Single Bond 2 com a incorporação de partículas bioativas na concentração de 1%. Para o teste de resistência de união foram utilizados 30 molares humanos hígidos (n=10) que posteriormente foram observados em Estereomicroscópio para análise do padrão da fratura. O grau de conversão foi feito no FTIR, onde foram feitas três leituras das gotas do adesivo dos diferentes grupos. A atividade antibacteriana foi feita através dos testes de difusão em ágar e contagem da unidade formadora de colônia (UFC), onde foram utilizados discos de adesivos polimerizados dos diferentes grupos. Os testes antibacterianos foram repetidos por três vezes. Os dados foram analisados estatisticamente quanto à sua normalidade. Como estes apresentaram distribuição normal, realizou-se o teste de análise de variância (ANOVA) paramétrica um fator (sistema adesivo) e o teste de Tukey, sendo adotado o nível de significância de 5% para a tomada de decisões. De acordo com os resultados obtidos na microtração (MPa±Dp) , a maior média foi observada no grupo ASB0,5 49,04±4,72A, seguida do grupo ASB 41,19±2,34B e a menor média foi observada no grupo ASB1 27,15±2,36C. No grau de conversão a maior média foi observada no grupo ASB 77,75±2,97A, seguido do grupo ASB0,5 63,18 ± 20,03A e grupo ASB1 58,35 ± 14,95A. Na atividade antibacteriana não houve diferença na formação de áreas de inibição, entretanto na unidade formadora de colônia o grupo ASB0,5 0,36±0,02B apresentou menor média em relação aos grupos ASB1 0,53±0,06A e ASB 0,51±0,01A. Foi concluído que a incorporação de partículas de vidro bioativas na concentração de 0,5% no sistema adesivo, aumentou a resistência de união da interface adesiva e apresentou atividade antibacteriana (UFC), no entanto, nas diferentes concentrações, não influenciou no grau de conversão do adesivo(AU)

The objective of this study was to evaluate the properties of a modified adhesive system with the incorporation of bioactive glass particles (SCHOTT Bioactive Glass) in two different concentrations (0.5 and 1%). The bond strength of the adhesive interface, the degree of conversion and antibacterial activity were evaluated, in addition to analysis using the Stereomicroscope and Scanning Electron Microscope (SEM). The adhesives were divided into three groups: ASB - Single Bond 2 Adhesive (3MESPE) without the incorporation of bioactive particles, ASB0.5 - Single Bond 2 Adhesive with the incorporation of bioactive particles at a concentration of 0.5% and ASB1 - Single Bond 2 adhesive with the incorporation of bioactive particles at a concentration of 1%. For the microtensile bond strength test, 30 healthy human molars (n = 10) were used, which were subsequently observed in a stereomicroscope to analyze the fracture pattern. The degree of conversion was made in the FTIR, where three readings of the drops of the adhesive of the different groups were made. The antibacterial activity was performed through the agar diffusion tests and colony forming unit (CFU) counting, where polymerized adhesive discs from different groups were used. The antibacterial tests were repeated three times. The data were analyzed statistically for normality. As these showed normal distribution, the parametric one-way analysis of variance (ANOVA) test (adhesive system) and the Tukey test were performed, with a significance level of 5% for decision making. According to the results obtained in microtensile (MPa ± Dp), the highest average was observed in the ASB0.5 group 49.04 ± 4.72A, followed by the ASB group 41.19 ± 2.34B and the lowest average was observed in the ASB1 group 27.15 ± 2.36C. In the degree of conversion, the highest average was observed in the ASB group 77.75 ± 2.97A, followed by the ASB0.5 group 63.18 ± 20.03A and ASB1 group 58.35 ± 14.95A. In the antibacterial activity there was no difference in the formation of areas of inhibition, however in the colony-forming unit the ASB0.5 group 0.36 ± 0.02B presented a lower average in relation to the ASB1 groups 0.53 ± 0.06A and ASB 0.51 ± 0.01A. It was concluded that the incorporation of bioactive glass particles at a concentration of 0.5% in the adhesive system, increased the bond strength of the adhesive interface and showed antibacterial activity (CFU), however, in different concentrations, did not influence the degree of conversion of the adhesive(AU)

Novel magnetic nanoparticle-containing adhesive with greater dentin bond strength and antibacterial and remineralizing capabilities.

OBJECTIVES: A nanoparticle-doped adhesive that can be controlled with magnetic forces was recently developed to deliver drugs to the pulp and improve adhesive penetration into dentin. However, it did not have bactericidal and remineralization abilities. The objectives of this study were to: (1) develop a magnetic nanoparticle-containing adhesive with dimethylaminohexadecyl methacrylate (DMAHDM), amorphous calcium phosphate nanoparticles (NACP) and magnetic nanoparticles (MNP); and (2) investigate the effects on dentin bond strength, calcium (Ca) and phosphate (P) ion release and anti-biofilm properties. METHODS: MNP, DMAHDM and NACP were mixed into Scotchbond SBMP at 2%, 5% and 20% by mass, respectively. Two types of magnetic nanoparticles were used: acrylate-functionalized iron nanoparticles (AINPs); and iron oxide nanoparticles (IONPs). Each type was added into the resin at 1% by mass. Dentin bonding was performed with a magnetic force application for 3min, provided by a commercial cube-shaped magnet. Dentin shear bond strengths were measured. Streptococcus mutans biofilms were grown on resins, and metabolic activity, lactic acid and colony-forming units (CFU) were determined. Ca and P ion concentrations in, and pH of biofilm culture medium were measured. RESULTS: Magnetic nanoparticle-containing adhesive using magnetic force increased the dentin shear bond strength by 59% over SBMP Control (p<0.05). Adding DMAHDM and NACP did not adversely affect the dentin bond strength (p>0.05). The adhesive with MNP+DMAHDM+NACP reduced the S. mutans biofilm CFU by 4 logs. For the adhesive with NACP, the biofilm medium became a Ca and P ion reservoir. The biofilm culture medium of the magnetic nanoparticle-containing adhesive with NACP had a safe pH of 6.9, while the biofilm medium of commercial adhesive had a cariogenic pH of 4.5. SIGNIFICANCE: Magnetic nanoparticle-containing adhesive with DMAHDM and NACP under a magnetic force yielded much greater dentin bond strength than commercial control. The novel adhesive reduced biofilm CFU by 4 logs and increased the biofilm pH from a cariogenic pH 4.5-6.9, and therefore is promising to enhance the resin-tooth bond, strengthen tooth structures, and suppress secondary caries at the restoration margins.

Hydrogen bonds of a novel resin cement contribute to high adhesion strength to human dentin.

OBJECTIVE: The detachment of fiber posts from root canals is primarily caused by the loss of adhesion between dentin and cement; therefore, the purpose of this study was to formulate a novel resin cement that improves the bond strength of fiber posts to the dentin-cement interface. METHODS: Three concentrations (30, 35, and 40wt.%) of bis[2-(methacryloyloxy)-ethyl] phosphate (2MP) were prepared as dentin bonding agent components. Isobornyl acrylate (IBOA) and ethylhexylacrylate (EHA) were used as key components to fabricate the resin cement (named IE cement). The adhesive strengths of IE cement to coronal and root canal dentin were tested after placement of specimens in a water bath at 100% humidity and 37°C for either 24h or 5 months. The microtensile bond test, the push-out bond test, and the fracture toughness test were performed. Four commercially available resin cements (Nexus(®) third generation (NX3), Variolink II, RelyX Unicem, and Panavia F 2.0) were used for comparisons. X-ray photoelectron spectroscopy (XPS) was used to analyze the interaction of collagen extracted from human dentin and 2MP as well as the fracture surfaces of the specimens submitted to the microtensile bond test. RESULTS: The 35% concentration of 2MP, in combination with IBOA and EHA, was the most effective for improving the IE cement's bond strength to dentin. The XPS results revealed that the phosphate groups of 2MP formed hydrogen bonds with the collagen and that such bonds prominently decreased in number in the specimens that were stored for 5 months. SIGNIFICANCE: The combination of 2MP, IBOA, and EHA can effectively increase the adhesive strength of IE cement to dentin via hydrogen bond formation.

Doxycycline-encapsulated nanotube-modified dentin adhesives.

This article presents details of fabrication, biological activity (i.e., anti-matrix metalloproteinase [anti-MMP] inhibition), cytocompatibility, and bonding characteristics to dentin of a unique doxycycline (DOX)-encapsulated halloysite nanotube (HNT)-modified adhesive. We tested the hypothesis that the release of DOX from the DOX-encapsulated nanotube-modified adhesive can effectively inhibit MMP activity. We incorporated nanotubes, encapsulated or not with DOX, into the adhesive resin of a commercially available bonding system (Scotchbond Multi-Purpose [SBMP]). The following groups were tested: unmodified SBMP (control), SBMP with nanotubes (HNT), and DOX-encapsulated nanotube-modified adhesive (HNT+DOX). Changes in degree of conversion (DC) and microtensile bond strength were evaluated. Cytotoxicity was examined on human dental pulp stem cells (hDPSCs). To prove the successful encapsulation of DOX within the adhesives-but, more important, to support the hypothesis that the HNT+DOX adhesive would release DOX at subantimicrobial levels-we tested the antimicrobial activity of synthesized adhesives and the DOX-containing eluates against Streptococcus mutans through agar diffusion assays. Anti-MMP properties were assessed via ß-casein cleavage assays. Increasing curing times (10, 20, 40 sec) led to increased DC values. There were no statistically significant differences (p > .05) in DC within each increasing curing time between the modified adhesives compared to SBMP. No statistically significant differences in microtensile bond strength were noted. None of the adhesives eluates were cytotoxic to the human dental pulp stem cells. A significant growth inhibition of S. mutans by direct contact illustrates successful encapsulation of DOX into the experimental adhesive. More important, DOX-containing eluates promoted inhibition of MMP-1 activity when compared to the control. Collectively, our findings provide a solid background for further testing of encapsulated MMP inhibitors into the synthesis of therapeutic adhesives that may enhance the longevity of hybrid layers and the overall clinical performance of adhesively bonded resin composite restorations.

One-pot synthesis of antibacterial monomers with dual biocidal modes.

OBJECTIVES: The present study reported a method for preparing a blend of antibacterial quaternary ammonium silanes and quaternary ammonium methacryloxy silane (QAMS) based on the sol-gel reaction between dimethyldiethoxy silane and two trialkoxysilanes, one with an antibacterial quaternary ammonium functionality and the other with a methacryloxy functionality. METHODS: Reaction products of the sol-gel reaction were characterised by direct infusion mass spectrometry, FTIR and proton, carbon and silicon NMR. This blend of monomers was incorporated into an experimental universal adhesive for evaluation of antimicrobial activity against Streptococcus mutans biofilms, microtensile bond strength and cytotoxicty. Retention of quaternary ammonium species on polymerised adhesive, leaching of these species from the adhesive and the ability of resin-dentine interfaces to inhibit S. mutans biofilms were evaluated over a 3-month water-ageing period. RESULTS: The antibacterial adhesive version killed bacteria in S. mutans biofilms not only through the release of non-copolymerisable quaternary ammonium silane species (release-killing), but also via immobilised quaternary ammonium methacryloxy silane that are copolymerised with adhesive resin comonomers (contact-killing). Contact-killing was retained after water-ageing. The QAMS-containing universal adhesive has similar tensile bond strength as the control and two commercially available universal adhesives, when it was used for bonding to dentine in the etch-and-rinse mode and self-etching mode. Incorporation of the antimicrobial quaternary ammonium species blend did not adversely affect the cytotoxicity of the universal adhesive formulation. CONCLUSIONS: Instead of using quaternary ammonium dimethacrylates and nanosilver, an alternative bimodal antimicrobial strategy for formulating antimicrobial universal dentine adhesives is achieved using the one-pot sol-gel synthesis scheme. CLINICAL SIGNIFICANCE: The QAMS containing universal dentine adhesives with dual antimicrobial activity is a promising material aimed at preventing second caries and prolonging the longevity of resin composite restorations.

Antimicrobial properties and dentin bonding strength of magnesium phosphate cements.

The main objective of this work was to assess the antimicrobial properties and the dentin-bonding strength of novel magnesium phosphate cements (MPC). Three formulations of MPC, consisting of magnesium oxide and a phosphate salt, NH4H2PO4, NaH2PO4 or a mixture of both, were evaluated. As a result of the setting reaction, MPC transformed into either struvite (MgNH4PO4·6H2O) when NH4H2PO4 was used or an amorphous magnesium sodium phosphate when NaH2PO4 was used. The MPC had appropriate setting times for hard tissue applications, high early compressive strengths and higher strength of bonding to dentin than commercial mineral trioxide aggregate cement. Bacteriological studies were performed with fresh and aged cements against three bacterial strains, Escherichia coli, Pseudomonas aeruginosa (planktonic and in biofilm) and Aggregatibacter actinomycetemcomitans. These bacteria have been associated with infected implants, as well as other frequent hard tissue related infections. Extracts of different compositions of MPC had bactericidal or bacteriostatic properties against the three bacterial strains tested. This was associated mainly with a synergistic effect between the high osmolarity and alkaline pH of the MPC. These intrinsic antimicrobial properties make MPC preferential candidates for applications in dentistry, such as root fillers, pulp capping agents and cavity liners.

Dental primer and adhesive containing a new antibacterial quaternary ammonium monomer dimethylaminododecyl methacrylate.

OBJECTIVES: The main reason for restoration failure is secondary caries caused by biofilm acids. Replacing the failed restorations accounts for 50-70% of all operative work. The objectives of this study were to incorporate a new quaternary ammonium monomer (dimethylaminododecyl methacrylate, DMADDM) and nanoparticles of silver (NAg) into a primer and an adhesive, and to investigate their effects on antibacterial and dentin bonding properties. METHODS: Scotchbond Multi-Purpose (SBMP) served as control. DMADDM was synthesized and incorporated with NAg into primer/adhesive. A dental plaque microcosm biofilm model with human saliva was used to investigate metabolic activity, colony-forming units (CFU), and lactic acid. Dentin shear bond strengths were measured. RESULTS: Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the new DMADDM were orders of magnitude lower than those of a previous quaternary ammonium dimethacrylate (QADM). Uncured primer with DMADDM had much larger inhibition zones than QADM (p<0.05). Cured primer/adhesive with DMADDM-NAg greatly reduced biofilm metabolic activity (p<0.05). Combining DMADDM with NAg in primer/adhesive resulted in less CFU than DMADDM alone (p<0.05). Lactic acid production by biofilms was reduced by 20-fold via DMADDM-NAg, compared to control. Incorporation of DMADDM and NAg into primer/adhesive did not adversely affect dentin bond strength. CONCLUSIONS: A new antibacterial monomer DMADDM was synthesized and incorporated into primer/adhesive for the first time. The bonding agents are promising to combat residual bacteria in tooth cavity and invading bacteria at tooth-restoration margins to inhibit caries. DMADDM and NAg are promising for use into a wide range of dental adhesive systems and restoratives.

Effect of calcium salt of functional monomer on bonding performance.

To determine the amount of 10-methacryloyloxydecyl dihydrogen phosphate (MDP)-calcium (MDP-Ca) salt produced through the demineralization of enamel or dentin by MDP, we designed experimental MDP-based one-step adhesives with different amounts of MDP. The null hypotheses were that (1) the amount of MDP-Ca salt produced through the demineralization of enamel was the same as that for dentin, and (2) the amounts of MDP-Ca salt have no effect on bonding performance. Increases in the amount of MDP resulted in increased amounts of MDP-Ca salt. The production amount of MDP-Ca salt of the dentin was 1.3 times higher than that of the enamel. The predominant species of the MDP and enamel reactants was a calcium hydrogen phosphate of MDP. In contrast, the dentin yielded both calcium phosphate and calcium hydrogen phosphate of MDP. Increases in the amount of MDP-Ca salt decreased both enamel and dentin bond strengths. An optimal concentration of MDP exists in one-step self-etch adhesives.

A novel dentin bonding system containing poly(methacrylic acid) grafted nanoclay: synthesis, characterization and properties.

OBJECTIVES: Developing a novel dentin bonding system containing poly(methacrylic acid)-grafted-nanoclay (PMAA-g-nanoclay) as reinforcing filler, with high stability of nanoparticle dispersion and improved bond strength and mechanical properties were the main objectives of this study. MATERIALS AND METHODS: Poly(methacrylic acid) (PMAA) was grafted onto the pristine sodium montmorrillonite (Na-MMT) nanoclay surface and characterized using FTIR, TGA, and X-ray diffraction (XRD). The PMAA-g-nanoclay was incorporated into an experimental dentin bonding system as filler in different concentrations and stability of nanoclay dispersion in the dilute adhesive, morphology of nanoclay layers in the photocured adhesive matrix, shear bond strength to caries-free extracted human premolar teeth, and mode of failure were studied. The mechanical properties including diametral tensile strength (DTS), flexural strength (FS), and flexural modulus (FM) were also investigated. The measured FM was also compared to theoretical prediction models. RESULTS: The grafting of PMAA onto the nanoclay surface was confirmed and the results revealed a partially exfoliated structure for PMAA-g-nanoclay. The dispersion stability of the modified nanoparticles in the dilute adhesive increased more than 45 times in comparison with the pristine nanoclay. The incorporation of 0.5wt.% PMAA-g-nanoclay to the adhesive resulted in a significant increase in microshear bond strength, DTS, and FS. Higher PMAA-g-nanoclay contents resulted in increased flexural modulus. The experimental flexural modulus was in good agreement with the Halpin-Tsai theoretical model. SIGNIFICANCE: Incorporation of PMAA-g-nanoclay particles as novel functional fillers into dental adhesive could result in the development of bonding systems with improved physical, mechanical, and adhesion properties.

Poly(acrylic acid) grafted montmorillonite as novel fillers for dental adhesives: synthesis, characterization and properties of the adhesive.

OBJECTIVE: This work investigates the graft polymerization of acrylic acid onto nanoclay platelets to be utilized as reinforcing fillers in an experimental dental adhesive. Physical and mechanical properties of the adhesive and its shear bond strength to dentin are studied. The effect of the modification on the stability of the nanoparticle dispersion in the dilute adhesive is also investigated. MATERIALS AND METHODS: Poly(acrylic acid) (PAA) was grafted onto the pristine Na-MMT nanoclay (Cloisite(®) Na(+)) through the free radical polymerization of acylic acid in an aqueous media. The resulting PAA-g-nanoclay was characterized using FTIR, TGA and X-ray diffraction (XRD). The modified nanoclays were added to an experimental dental adhesive in different concentrations and the morphology of the nanoclay layers in the photocured adhesive matrix was studied using TEM and XRD. Shear bond strength of the adhesives containing different filler contents was tested on the human premolar teeth. The stability of nanoclay dispersion in the dilute adhesive was also studied using a separation analyzer. The results were then statistically analyzed and compared. RESULTS: The results confirmed the grafting reaction and revealed a partially exfoliated structure for the PAA-g-nanoclay. Incorporation of 0.2 wt.% of the modified nanoclay into the experimental adhesive provided higher shear bond strength. The dispersion stability of the modified nanoparticles in the dilute adhesive was also enhanced more than 25 times. SIGNIFICANCE: Incorporation of the modified particles as reinforcing fillers into the adhesive resulted in higher mechanical properties. The nanofiller containing bonding agent also showed higher shear bond strength due to the probable interaction of the carboxylic acid functional groups on the surface of the modified particles with hydroxyapatite of dentin.

Estimation of properties of a photoinitiated silorane-based composite with potential for orthopaedic applications.

We have synthesized a filler-reinforced silorane composite that has potential applications in orthopaedic surgery, such as for a bone stabilizer. The purpose of the present work was to develop a method for estimating four properties of this material; namely, maximum exotherm temperature, flexural strength, flexural modulus, and fracture toughness. The method involved the use of mixture design-of-experiments and regression analysis of results obtained using 23 formulations of the composite. We validated the estimation method by showing that, for each of four composite formulations that were not included in the method development, the value of each of the aforementioned properties was not significantly different from that obtained experimentally. Our estimation method has the potential for use in the development of a wide range of orthopaedic materials.

Synthesis and characterization of triethylene glycol dimethacrylate nanocapsules used in a self-healing bonding resin.

OBJECTIVES: To date, the production of highly durable dentine bonding is still a challenge. Self-healing bonding resins may provide a new direction for the improvement of the bonding durability. The objective of the current study was to synthesize polyurethane nanocapsules encapsulated with the core material triethylene glycol dimethacrylate (TEGDMA) for use as a major component in a self-healing bonding resin. METHODS: TEGDMA nanocapsules were synthesized via interfacial polycondensation in a miniemulsion, and the TEGDMA nanocapsules were then characterized via Fourier-transform infrared (FTIR) spectrometer, field emission scanning electron microscopy (FESEM), and high-performance liquid chromatography (HPLC) to investigate the morphology, the average TEGDMA loading (DL%), and encapsulation efficiency (EE%). The mechanical property of dental adhesive with different concentrations (0, 3, 6, 9, and 12 wt%) of the TEGDMA nanocapsules were also measured, and the cytotoxicity was investigated using an MTT assay. RESULTS: FTIR confirmed that the TEGDMA nanocapsules were successfully synthesized. These nanocapsules showed a high drug load. The bond strength of the dental adhesive incorporated with 9 wt% TEGDMA nanocapsules was significantly higher compared with those of the other groups (P<0.001). Moreover, the biocompatibility of the dental adhesive was not affected by the incorporation of the TEGDMA nanocapsules. CONCLUSIONS: The current study demonstrated the successful synthesis of TEGDMA nanocapsules, and the overall properties of the dental adhesive were not compromised.

[Synthesis and application of novel dental adhesive materials of 10-methacryloyloxydecyl dihydrogen phosphate].

10-methacryloyloxydecyl dihydrogen phosphate was synthesized from the reaction of phosphoryl chloride with methylacrylic acid and 1, 10-decanediol. The structure of product was characterized by 1H-NMR, 31P-NMR and MS. The effect of this product on the bond durability of composite resin joined to enamel, dentin and dental alloy was evaluated by the test of shear strengths. 10-methacryloyloxydecyl dihydrogen phosphate significantly elevated the bond strength of the composite resin joined to enamel, dentin, Ti alloy and Co-Cr alloy; the relevant shear strengths were 13.5, 11.2, 16.2 and 18.1 MPa, respectively.

Synthesis of phosphate monomers and bonding to dentin: esterification methods and use of phosphorus pentoxide.

OBJECTIVES: The aim of this study was to synthesize an acidic monomer using an alternative synthetic pathway and to evaluate the influence of the acidic monomer concentration on the microtensile bond strength to dentin. METHODS: The intermediary 5-hydroxypentyl methacrylate (HPMA) was synthesized through methacrylic acid esterification with 1,5-pentanediol, catalyzed by p-toluenesulfonic acid. To displace the reaction balance, the water generated by esterification was removed by three different methods: anhydrous sodium sulfate; molecular sieves or azeotropic distillation. In the next step, a phosphorus pentoxide (4.82 mmol) slurry was formed in cold acetone and 29 mmol of HPMA was slowly added by funnel addition. After the reaction ended, solvent was evaporated and the product was characterized by 1HNMR and FTIR. The phosphate monomer was introduced in a self-etch primer at concentrations of 0, 15, 30, 50, 70 and 100 wt%. Clearfil SE Bond was used as commercial reference. Microtensile bond strength to dentin was evaluated 24h after the bonding procedures, followed by fracture analysis (n=20). Data was submitted to ANOVA and Tukey's post hoc test. RESULTS: The highest yield was obtained (62%) when azeotropic distillation was used, while the reaction with molecular sieves was not feasible. The phosphoric moiety attachment to the monomer was successfully performed with a quantitative yield that reached around 100%. The acidic monomer concentration significantly affected the bond strength and the highest mean (55.1+/-12.8 MPa) was obtained when 50% of acidic monomer was used. CONCLUSION: The synthesis pathways described in the present study appear to be a viable alternative for developing phosphate monomers.

2,3-Epithiopropyl methacrylate as functionalized monomer in a dental adhesive.

OBJECTIVES: The aim of this study was to investigate new dentin bonding agents formulated with 2,3-epithiopropyl methacrylate (ETMA) comonomer blends. METHODS: Synthesis and characterization of ETMA were performed. Adhesive resins with three different ETMA concentrations (0.1, 1 and 10 wt.%) were prepared. To comparison a blend with only Bis-GMA/HEMA and with 1% of GMA were used as controls. FTIR analysis was used to verify the degree of conversion. Blend copolymerization was investigated by (1)H NMR spectroscopy analysis. To investigate immediate properties of experimental adhesives, microtensile bond strength to human dentin and SEM fractographic analysis were studied. RESULTS: ETMA was synthesized with 90% yield through a one step synthetic route. Degree of conversion for the experimental and control resins was not significantly different. Different monomers showed copolymerization among them, not presenting traces of ETMA release in 0.1 and 1% groups. Bonding agents containing ETMA had statistically higher microtensile bond strength values than the no ETMA adhesive (p<0.05). CONCLUSIONS: Dental adhesive resin-ETMA mixtures produced increased bond strengths without harming the other properties investigated.

Mejorando la fuerza adhesiva de los brackets ortodóncicos / Improving the shear bond strength of orthodontic brackets

Los objetivos de este estudio fueron: determinar el efecto de 2 promotores de la adhesión, Enhance-L.C. (Reliance, Itasca, Ill.) y OrthoSolo (Ormco, Sybron Dental Specialities, Tokyo, Japan), en la fuerza adhesiva y en el adhesivo remanente tras el descementado de brackets (Victory Series, 3M Unitek Dental Products, Monrovia, Calif.), y comprobar si Enhance-L.C. es específico del material, como sugiere su fabricante, o si su efecto es similar con otros sistemas adhesivos que no pertenezcan a su línea de productos. Ciento veinticinco premolares superiores extraídos se dividieron en 5 grupos de 25 premolares cada uno: I, Transbond-XT (3M Unitek Dental Products, Monrovia, Calif.); II, Transbond-XT/Enhance-L.C.; III, Transbond-XT/OrthoSolo; IV, Light-Bond (Reliance, Itasca, Ill.), y V, Light-Bond/Enhance-L.C. La resistencia a las fuerzas de cizalla se midió en una máquina universal de tests y el adhesivo remanente se cuantificó con un sistema de análisis de imagen. OrthoSolo mejoró significativamente la adhesión de Transbond-XT. Enhance-L.C. no aumentó significativamente la adhesión de Transbond-XT ni de Light-Bond (sistema recomendado por el fabricante). Sin embargo, la combinación Light-Bond/ Enhance-L.C. proporcionó una fuerza adhesiva significativamente mayor que Transbond-XT y Transbond-XT/Enhance-L.C. (p 0,005). En cuanto al adhesivo remanante, no se observó un aumento significativo (p > 0,05) con la aplicación de los potenciadores. Se recomienda la utilización de OrhoSolo en los casos en los que se necesite aumentar la adhesión del sistema Transbond-XT. En cambio, Enhance-L.C. es preferible usarlo con Light-Bond cuando se necesite mayor fuerza adhesiva

The aims of this study were: to determine the effect of two adhesion promoters, Enhance-L.C. (Reliance, Itasca, Ill.) and OrthoSolo (Ormco, Sybron Dental Specialities, Tokyo, Japan) on the shear bond strength, and the ammount of adhesive remnant on teeth after debonding brackets (Victory Series, 3M Unitek Dental Products, Monrovia, Calif.); and to find out if Enhance-L.C. is material specific as suggested by the manufacturer or if it has similar effects when used with other orthodontic adhesive systems which do not belong to the same product range. Were divided into five groups of 25, 125 upper premolars: I, Transbond-XT (3M Unitek Dental Products, Monrovia, Calif.); II, Transbond-XT/Enhance-L.C; III, Transbond-XT/OrthoSolo; IV, Light-Bond (Reliance, Itasca, Ill.); and V, Light-Bond/Enhance-L.C. Shear bond strength was tested using a universal test machine and adhesive remnant was quantified using an image analysis equipment. OrthoSolo significantly improved bonding for Transbond-XT adhesive system. Enhance L.C. did not significantly increase bond strength for either Transbond-XT or Light-Bond (the system recommended by the manufacturer). However the combination Light-Bond/Enhance-LC provided a significantly greater bond strength than Transbond-XT and Transbond-XT/Enhance-L.C. (P.005). As for adhesive remnant, no significant increase (P>.05) was observed with the application of the promoters. The use of OrthoSolo is recommended in those cases requiring increased bond strength for Transbond-XT. With Light-Bond system, it is preferible to use Enhance-L.C. when increased bond strength is needed

Dental biomaterials and the healing of dental tissue.

This paper addresses the application of new adhesive technologies to dentistry. The bonding of synthetic polymers to dentin is difficult and it has taken a long time to produce reliable methods. Success has been achieved suing a 4-methacryloyloxyethyltrimellitate anhydride/methyl methacrylate-tri-n-butyl borane system which allows the generation of a layer of hybridised dentin. This provides a pseudo-wound-healing layer that resists demineralisation and degradation, is impermeable and inhibits secondary caries and hypersensitivity.

Design, formulation, and evaluation of isocyanatoacrylate copolymer dental adhesives.

Experiments have recently been completed to explore the development of isocyanatoacrylate copolymers as new dental adhesives. A main goal of this work was to test the utility of solubility parameter differences between the candidate adhesives and etched dentin as a predictor of relative bond strength. All candidate adhesive mixtures contained 2-isocyanatoethyl methacrylate (IEM), a selected amount of tri-n-butylborane oxide (TBBO) initiator, and one of 13 methacrylate comonomers. Reactivity ratios were computed for comonomer pairs as indicators of relative reactivity. The concentration of TBBO was optimized for each comonomer mixture to obtain working times of 2-6 min and setting times of 6-10 min. The solubility parameter difference Deltadelta (J/cm(3))(1/2) was calculated for each test mixture with respect to an etched dentin substrate, as an approximation of wetting ability. Using standard techniques for shear bond strength evaluation, mean shear bond strength values ranging between 7-15.5 MPa were obtained for comonomer adhesives in bonding Z-100 composite to treated dentin. Shear bond strength values showed a good correlation (r = -0.612, P

Effects of N-methacryloyl amino acid applications on hybrid layer formation at the interface of intertubular dentin.

To understand the role of NMAA in the bonding of composite resin to a dentin surface, we investigated the effects of N-methacryloyl amino acid (NMAA) application on the expansion of aggregated collagen fibers, formation of a hybrid layer, and the tensile bond strength between composite resin and dentin. Four NMAA derivatives--N-methacryloyl-alpha-glycine (NMGly), N-methacryloyl-gamma-amino n-butyric acid (NMBu), N-methacryloyl-alpha-hydroxyproline (NMHPro), and N-methacryloyl-alpha-glutamic acid (NMGlu)--were prepared and applied to dentin surfaces which had been etched with 40% by mass H3PO4 and air-blown. The shrunken collagenous layer expanded by approximately 50% to 70% by volume of the original collagenous layer thickness after application of the NMAA primers. Application of the bonding agent and composite resin after NMAA treatment resulted in the formation of a hybrid layer. The thickness of the hybrid layer was somewhat smaller than the collagenous layer formed by the NMAA treatment only, regardless of the type of NMAA used. The thickness of the hybrid layer was approximately ten times larger than that formed without NMAA treatment. Although all NMAA primers formed hybrid layers of similar thickness, higher tensile bond strengths, from 13 to 15 MPa, were obtained when etched and air-blown dentin was treated with NMBu, NMGly, or NMGlu. NMHPro gave only 6.6 MPa, a value similar to that obtained when no NMAA was used. We concluded, therefore, that formation of the hybrid layer is a necessary but insufficient condition for high bond strength.