Experimental Resin Research Articles

Influence of filler charge on gloss of composite materials before and after in vitro toothbrushing

ObjectivesThis study evaluated the gloss behaviour of experimental resin composites loaded with different filler percentages, immediately after polishing and after toothbrushing simulation. MethodsSixteen disc-shaped specimens were fabricated for each different-charged composite (40%, 50%, 60%, 70% and 75%) and polished with SiC abrasive papers. Gloss measurements were made prior to simulated toothbrushing. The specimens were subjected to the simulation for 5, 15, 30 and 60min using an electrical toothbrush with a standardized pressure while being immersed in a toothpaste/artificial saliva slurry. ResultsBaseline composite gloss values ranged from 69.7 (40%) to 81.3 (75%) GU (gloss units) and from 18.1 (40%) to 32.3 (75%) GU after 1h of brushing. Highest gloss values were obtained by 75%-charged resin, while the lowest values were obtained by the 40%-charged one. ConclusionsAll tested materials showed a gloss decrease. However, the higher filler load a composite resin has, the higher gloss it can achieve. Clinical significanceGloss of resin composite materials is an important factor in determining aesthetic success of anterior restorations, and this property may vary according to the filler charge of the restorative material. Higher filler load of a composite resin results in higher gloss values.

Micro-hardness and mineral loss of enamel lesions after infiltration with various resins: Influence of infiltrant composition and application frequency in vitro

ObjectivesThe aim of this in vitro study was to evaluate the influence of infiltrant composition and application frequency on micro-hardness and lesion progression after resin infiltration of artificial enamel lesions. MethodsIn each of 100 bovine enamel samples, three artificial caries lesions were created (pH=4.95, 50 days). After etching two of the lesions (37% phosphoric acid) specimens were randomly allocated to five infiltrants (four experimental infiltrants with different monomer and solvent compositions and penetration coefficients, and one commercial infiltrant [Icon, DMG]). Lesions were then infiltrated and light-cured, and infiltration repeated afterwards for one of the lesions. Infiltrated samples were cut into halves, with one half being demineralised for further 50 days. Micro-hardness (VHN) and integrated mineral loss (ΔZ) were evaluated at baseline and after second demineralisation. Repeated measures ANOVA and paired t-tests were used to analyse influence of material composition and application frequency on micro-hardness and lesion progression (integrated mineral loss difference ΔΔZ). ResultsResin infiltration significantly increased micro-hardness and reduced lesion progression compared to untreated artificial lesions (p<0.05, t-test). Neither micro-hardness nor lesion progression were significantly influenced by material composition (p>0.05, ANOVA). In contrast, twice application resulted in significantly increased micro-hardness and demineralisation resistance of infiltrated lesions (p<0.05, ANOVA). ConclusionResin infiltration significantly improves micro-hardness and demineralisation resistance of enamel lesions; these effects are significantly enhanced if resins are applied twice. Experimental resins did not outperform the commercial infiltrant. Clinical significanceThis in vitro study demonstrated that resin infiltration significantly increases both micro-hardness and demineralisation resistance of enamel caries lesions. Twice application of the infiltrant seems to increase these effects. In contrast, the composition of the infiltrant had no significant influence on investigated parameters.

1,3-Diethyl-2-thiobarbituric acid as an alternative coinitiator for acidic photopolymerizable dental materials

The ethyl-4-dimethylaminobenzoate (EDAB) is widely used as a coinitiator of the camphorquinone (CQ), but in acidic circumstances it might present some instability, reducing the polymerization efficiency of the material. Considering this, new coinitiators are being evaluated. Hence, this study evaluated the kinetic of polymerization (KP), the degree of conversion (DC), and the rate of polymerization (RP ) of experimental resin adhesives containing 1,3-diethyl-2-thiobarbituric acid (TBA) as a coinitiator of the CQ. The experimental monomeric blend was prepared with bisphenol A glycidyl dimethacrylate, 2-hydroxyethyl methacrylate, and acidic monomers. CQ was added at 1 mol % as photoinitiator. Six groups were formulated: four containing concentrations of 0.1, 0.5, 1, and 2 mol % of TBA, one without coinitiator, and the last one containing 1 mol % of EDAB (control group). The KP and the RP were performed using real-time Fourier Transform infrared spectroscopy. The group without coinitiator has not formed a polymer, whereas the addition of TBA resulted in the conversion of monomers in polymer. The DC of the adhesives was as higher as the increase in the TBA content. The group with 2 mol % of TBA presented improved DC and reactivity (RP ) than the other groups and the control one. Hence, the TBA has performed as a coinitiator of the CQ for the radical polymerization of methacrylate resin adhesives and it has improved the DC and the reactivity of the materials. Thus, it is a potential coinitiator for the photopolymerization of dental materials.

Remineralisation properties of innovative light-curable resin-based dental materials containing bioactive micro-fillers.

Innovative dental restorative materials should be highly bioactive to induce therapeutic effects at the bonding interface during intimate contact with biological fluids. This study aimed at evaluating the remineralisation properties of innovative light-curable resin-based dental materials containing bioactive calcium-phosphosilicates micro-fillers. The apatite formation ability was assessed by ATR-FTIR, XRD, calcium-chelation dye-assisted confocal microscopy (CLSM) and SEM analysis after soaking in SBF. Changes in transition glass temperature (Tg), water sorption/solubility, alkalinising activity (pH) Knoop micro-hardness (KHN), were also evaluated. Four experimental resin-based materials containing various silicate-base micro-fillers and a control filler-free resin blend were formulated. Disc-shaped specimens were polymerised and submitted to pH/alkalinising activity and water sorption/solubility analyses. The bioactivity and the apatite precipitation induced by the tested materials were evaluated through ATR/FTIR vibrational analysis, SEM and XRD analyses subsequent to SBF storage. Knoop micro-hardness (KHN) and differential scanning calorimetry (DSC) were also performed. The experimental resins containing the bioactive micro-fillers were able to induce apatite precipitation subsequent to prolonged SBF storage (30-90 days). However, the resins containing the bioactive ZnO/polycarboxylated micro-fillers (BAG-Zn; βTCS-Zn) showed the lowest water sorption and solubility mass changes (P < 0.05). A significant increase of the KHN and Tg subsequent prolonged SBF storage was also observed. The use of such light-curable bioactive materials in restorative dentistry might represent a potentially therapeutic approach to increase the longevity of the restorations via apatite deposition the mineral-depleted tissues at the bonding.

Sal de iodônio aumenta a resistência coesiva de uma resina adesiva experimental na presença de solvente

This study evaluated the effect of organic solvent concentration on the tensile strength for an experimental adhesive resin containing a ternary photoinitiator system. A monomer blend based on the Bis-GMA, TEGDMA and HEMA was used as a model dental adhesive resin. Two photoinitiation systems were used: a binary system camphorquinone (CQ) and ethyl 4-dimethylamine benzoate (EDAB)] and a ternary system CQ, EDAB and diphenyliodonium hexafluorphosphate (DPIHFP)]. Varied ethanol concentrations were added to the resins, viz. 0, 5, 10, 20, 30, 40 wt%. The ultimate tensile strength test was used to investigate the influence of the solvent amount on the resistance of resins. Furthermore, the use of iodonium salt in photoinitiation system increased the cohesive strength when compared with the binary system. Regardless of solvent concentration, the cohesive strength of polymers containing diphenyliodonium was higher than for the binary photoinitiator system.

Evaluation of the antimicrobial and physical properties of an orthodontic photo-activated adhesive modified with an antiplaque agent: An in vitro study

This study was designed to investigate the antimicrobial and physical properties of orthodontic composite resin modified by the addition of an antimicrobial agent. Transbond XT (3M Unitek), a photo-activated, light-cured composite resin, modified by the addition of chlorhexidine, in concentrations 2.5 wt% was formed into a uniform disc and also used for direct bonding of the brackets on the freshly extracted premolars for testing. The tablets of each group and a control group were subjected to the agar plate diffusion test to measure the zone of bacterial inhibition. In addition, they were incubated for 24 h in brain heart infusion medium inoculated with Streptococcus mutans and examined for antimicrobial action. A total of 80 extracted premolars were collected and divided into two sets of 40 teeth each. Stainless steel preadjusted edgewise appliance (PEA) brackets were bonded by using control and experimental composites. A universal testing machine was used to determine the shear bond strength. The first set of teeth was tested after 24 h and the second set after 25 days of storage in distilled water. Time-dependent release of antimicrobial agents from the modified composites was also monitored spectrophotometrically. The findings indicated that (1) addition of chlorhexidine to the orthodontic composite resin enhanced its antimicrobial properties, (2) there was no significant difference between the bond strengths of the control and the experimental resins tested after 24 h and 25 days and (3) maximum release of chlorhexidine from the modified resin was much higher than the minimum inhibitory concentration level.

Water sorption of CH3- and CF3-Bis-GMA based resins with additives

ObjectivesTo evaluate the effect of additives on the water sorption characteristics of Bis-GMA based copolymers and composites containing TEGDMA, CH3Bis-GMA or CF3Bis-GMA. Material and methodsFifteen experimental copolymers and corresponding composites were prepared combining Bis-GMA and TEGDMA, CH3Bis-GMA or CF3Bis-GMA, with aldehyde or diketone (24 and 32 mol%) totaling 30 groups. For composites, barium aluminosilicate glass and pyrogenic silica was added to comonomer mixtures. Photopolymerization was effected by 0.2 wt% each of camphorquinone and N,N-dimethyl-p-toluidine. Specimen densities in dry and water saturated conditions were obtained by Archimedes' method. Water sorption and desorption were evaluated in a desorption-sorption-desorption cycle. Water uptake (%WU), water desorption (%WD), equilibrium solubility (ES; µg/mm3), swelling (f) and volume increase (%V) were calculated using appropriate equations. ResultsAll resins with additives had increased %WU and ES. TEGDMA-containing systems presented higher %WU, %WD, ES, f and %V values, followed by resins based on CH3Bis-GMA and CF3Bis-GMA. ConclusionsAldehyde and diketone led to increases in the water sorption characteristics of experimental resins.

Experimental Resin Cements Containing Bioactive Fillers Reduce Matrix Metalloproteinase–mediated Dentin Collagen Degradation

IntroductionCollagen dentin matrix may represent a suitable scaffold to be remineralized in the presence of bioactive materials. The purpose of this study was to determine if experimental resin cements containing bioactive fillers may modulate matrix metalloproteinase–mediated collagen degradation of etched dentin. MethodsHuman dentin beams demineralized using 10% phosphoric acid or 0.5 mol/L EDTA were infiltrated with the following experimental resins: (1) unfilled resin, (2) resin with Bioglass 45S5 particles (Sylc; OSspray Ltd, London, UK), and (3) resin with β–tricalcium phosphate–modified calcium silicate cement (HCAT-β) particles. The filler/resin ratio was 40/60 wt%. The specimens were stored in artificial saliva, and the determination of C-terminal telopeptide (ICTP) was performed by radioimmunoassay after 24 hours, 1 week, and 4 weeks. Scanning electron microscopic analysis of dentin surfaces after 4 weeks of storage was also executed. ResultsCollagen degradation was prominent both in phosphoric acid and EDTA-treated dentin. Resin infiltration strongly reduced the MMP activity in demineralized dentin. Resin-containing Bioglass 45S5 particles exerted higher and more stable protection of collagen at all tested dentin states and time points. HCAT-β induced collagen protection from MMPs only in EDTA-treated specimens. Dentin remineralization was achieved when dentin was infiltrated with the resin cements containing bioactive fillers. ConclusionsMMP degradation of dentin collagen is strongly reduced in resin-infiltrated dentin. The inclusion of Bioglass 45S5 particles exerted an additional protection of collagen during dentin remineralization.

Subcritical crack growth and in vitro lifetime prediction of resin composites with different filler distributions

ObjectivesVerify the influence of different filler distributions on the subcritical crack growth (SCG) susceptibility, Weibull parameters (m and σ0) and longevity estimated by the strength–probability–time (SPT) diagram of experimental resin composites. MethodsFour composites were prepared, each one containing 59vol% of glass powder with different filler sizes (d50=0.5; 0.9; 1.2 and 1.9μm) and distributions. Granulometric analyses of glass powders were done by a laser diffraction particle size analyzer (Sald-7001, Shimadzu, USA). SCG parameters (n and σf0) were determined by dynamic fatigue (10−2 to 102MPa/s) using a biaxial flexural device (12×1.2mm; n=10). Twenty extra specimens of each composite were tested at 100MPa/s to determine m and σ0. Specimens were stored in water at 37°C for 24h. Fracture surfaces were analyzed under SEM. ResultsIn general, the composites with broader filler distribution (C0.5 and C1.9) presented better results in terms of SCG susceptibility and longevity. C0.5 and C1.9 presented higher n values (respectively, 31.2±6.2a and 34.7±7.4a). C1.2 (166.42±0.01a) showed the highest and C0.5 (158.40±0.02d) the lowest σf0 value (in MPa). Weibull parameters did not vary significantly (m: 6.6 to 10.6 and σ0:170.6 to 176.4MPa). Predicted reductions in failure stress (Pf=5%) for a lifetime of 10 years were approximately 45% for C0.5 and C1.9 and 65% for C0.9 and C1.2. Crack propagation occurred through the polymeric matrix around the fillers and all the fracture surfaces showed brittle fracture features. SignificanceComposites with broader granulometric distribution showed higher resistance to SCG and, consequently, higher longevity in vitro.

Biofilm inhibition by an experimental dental resin composite containing octenidine dihydrochloride

ObjectivesThe aim of the present study was to investigate an antimicrobial additive containing experimental resin composite with regards to its impact on biofilm formation under oral conditions. MethodsBiofilms were established in situ on composite specimens (n=192) which contained octenidine dihydrochloride (ODH, 3wt.% or 6wt.%). Samples without antimicrobial additive served as control (n=96). Composite specimens were fixed on custom made splints and exposed to the oral cavity of six healthy volunteers for three or seven days. Biofilm formation was assessed by scanning electron microscopy (SEM) and fluorescence microscopy (FM). ResultsThe biofilm formation was significantly reduced on ODH containing samples compared to controls after three as well as after seven days in situ. FM evaluation additionally showed a lower viability of the reduced biofilms for both ODH concentrations. SignificanceDuring this short term investigation, incorporation of ODH into resin based composite materials caused biofilm inhibiting effects in situ.

Effects of Silanes Alone and Their Blends with HEMA on Resin–Titanium Bonding

Two organofunctional silane coupling agents alone and two silane blend systems with HEMA were evaluated in vitro as adhesion promoters for bonding bis-GMA resin to a silica-coated titanium surface. The silanes were applied onto tribochemically silica-coated titanium surfaces. Experimental bis-GMA resin stubs were applied and photo-polymerized onto titanium. The specimens were subjected to three different conditions: (1) dry storage for 24 h, (2) storage in de-ionized water at 37°C for six months and (3) alternating storage in de-ionized water at 37°C and thermocycling (6000 cycles, 5–55°C) for 6 months. Shear bond strengths of the resin to titanium were measured using a universal testing machine. Surface examination was made with a scanning electron microscope (SEM) after the bond strength test. Highest shear bond strength was obtained with 3-acryloxypropyltrimethoxysilane stored in dry condition (20.2 ± 3.2MPa), and the lowest value was obtained with 3-methacryloxypropyltrimethoxysilane (ESPE Sil) in alternating water storage and thermocycling condition (1.4 ± 0.6 MPa). The type of storage condition affected significantly the shear bond strength (p < 0.05). The shear bond strength obtained from dry storage was the highest, while the shear bond strength obtained from alternating water storage and thermocycling condition was the lowest. Interfacial failure was the main failure mode (87.2%) followed by mixed failure (9.4%) and cohesive failure (3.4%). The addition of 0.5 vol%. HEMA into silane primers did not improve the shear bond strength between the experimental resin and silica-coated titanium.

Influence of filler content on physicomechanical and bonding properties of an experimental dental resin cement

AbstractTo investigate the effects of filler contents on the bonding and physicomechanical properties of experimental dental resin cements and the correlation between them, four groups were formulated with silicon dioxide filler in the following weight percentages: A: 40%, B: 50%, C: 60%, and D: 70%. LuxaCore dental resin cement was used as group E for commercial reference. For testing bond strength, resin cements were applied to the prefabricated dental fiber posts in the artificial teeth canal and photo cured, and then the microtensile bonding strength (BS) between posts and resin cement was measured in sticks of 1 × 1 mm2. For the mechanical properties, flexural strength (FS), diametral tensile strength (DTS), compressive strength (CS), and hardness (H) were tested according to the related standard. Water sorption and solubility were also determined. The results showed both bonding and physicomechanical strengths of the experimental resin cements varied to different extents with filler addition. Positive correlations existed respectively between the filler content and some mechanical properties (rFS = 0.964, rCS = 0.967, and rH = 0.959), whereas no significant correlations were found between the filler content and the other strength values tested in this study (rDTS = 0.321, rBS = 0.014), neither were between bond strength and mechanical properties. The effect of filler content on mechanical properties was more influential and prominent compared to that on bond strength. It is partial to compare properties and to predict clinical behaviors of resin materials based on a single in vitro test, and comprehensive evaluation is necessary. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Antibacterial effect of a resin incorporating a novel polymerizable quaternary ammonium salt MAE‐DB against Streptococcus mutans

The antibacterial properties of resins incorporating MAE-DB and the underlying mechanisms of action were evaluated. Antibacterial effects against Streptococcus mutans were tested using the film contact method, with accumulation and membrane integrity observed by scanning electron microscopy and confocal laser scanning microscopy, respectively. Quantitative PCR was used to determine expression of the S. mutans glucosyltransferase B (gtfB) gene on the surface of resins containing 10% MAE-DB. Bacterial growth was inhibited on resin containing 10% MAE-DB as compared with the control at 1 day, 7 days, 30 days, or 180 days (p < 0.05). For the 10%-MAE-DB resin, no significant differences in bacterial viability were found regardless of the time of incubation (p > 0.05). The number of bacteria attached to resin containing 10% MAE-DB was considerably lower than the control. The proportion of bacteria with damaged cell membranes was increased in the experimental resin over controls. Expression of gtfB was reduced by 10% MAE-DB compared with the control (p < 0.05). These findings demonstrate that MAE-DB can be incorporated into resin materials at sufficient concentrations for long-term antibacterial effects against S. mutans after polymerization by attenuating gtfB expression and impairing membrane integrity.

Properties of experimental resins based on synthesized propoxylated bis-GMA with different propionaldehyde ratios

The effect of different propionaldehyde ratios on the properties of bis-GMA-based comonomers and copolymers diluted with propoxylated bis-GMA (CH3bis-GMA) was evaluated. Five experimental comonomers were prepared combining bis-GMA with CH3bis-GMA and propionaldehyde at 0, 2, 8, 16, 24 mol%. Light polymerization was effected with the use of 0.2 wt. (%) each of camphorquinone and N,N-dimethyl-p-toluidine. Resin degrees of conversion (%DC) were evaluated by FT-IR spectrophotometry and Tg by Differential Scanning Calorimeter. Complex viscosity (η*), the effect of temperature on η*, and Microhardness (H) for dry and wet samples were also determined. Data were analyzed by Student's t-test, one-way ANOVA and Tukey-Kramer test (α = 0.05). The group with 24 mol% additive had a significant increase in %DC and H, and the lowest comonomer Tg and η*. No remarkable variation was noted in copolymers Tg s. All resins presented Newtonian behavior of viscosity, which linearly decreased with increased temperature. The η* decreased sigmoidally as the additive ratio increased.

Therapeutic effects of novel resin bonding systems containing bioactive glasses on mineral-depleted areas within the bonded-dentine interface

This study aimed in evaluating the effects of two experimental resin bonding systems containing conventional Bioglass 45S5 (BAG) or Zinc-polycarboxylated bioactive glass (BAG-Zn) micro-fillers on the resin-bonded dentine interface after storage in a simulated body fluid solution (SBFS). Three resin bonding systems were formulated: Resin-A: (BAG containing); Resin-B; (BAG-Zn containing); Resin-C (no filler). The ability of the experimental resins to evoke apatite formation was evaluated using confocal Raman spectroscopy. Acid-etched dentine specimens were bonded, and prepared for AFM/nano-indentation analysis in a fully-hydrated status to evaluate the modulus of elasticity (Ei) and hardness (Hi) across the interface at different SBFS storage periods. Further resin-dentine specimens were tested for microtensile bond strength after 24 h or 3 months of SBFS storage. SEM examination was performed after de-bonding and confocal laser microscopy was used to evaluate the ultramorphology of the interfaces and micropermeability. The resin A and B showed a consistent presence of apatite (967 cm(-1)), reduced micropermeability within the resin-dentine interface and a significant increase of the Ei and Hi along the bonded-dentine interface after prolonged SBFS storage. Bond strength values were affected by the resin system (P < 0.0001) and by storage time (P < 0.0001) both after 24 h and 3 months of SBFS storage. In conclusion, resin bonding systems containing bioactive fillers may a have therapeutic effect on the nano-mechanical properties and sealing ability of mineral-depleted resin-dentine interface.

Bracket bond strength and cariostatic potential of an experimental resin adhesive system containing Portland cement

To determine if a new experimental resin-based material containing Portland cement (PC) can help prevent enamel caries while providing adequate shear bond strength (SBS). Brackets were bonded to human premolars with experimental resin-based adhesive pastes composed of three weight rations of resin and PC powder (PC 30, 7:3; PC 50, 5:5; PC 70, 3:7; n = 7). Self-etching primer (SEP) adhesive (Transbond Plus) and resin-modified glass ionomer cement (RMGIC) adhesive (Fuji Ortho FC Automix) were used for comparison. All of the bonded teeth were subjected to alternating immersion in demineralizing (pH 4.55) and remineralizing (pH 6.8) solutions for 14 days. The SBS for each sample was examined, and the Adhesive Remnant Index (ARI) score was calculated. The hardness and elastic modulus of the enamel were determined by a nanoindenter at 20 equidistant depths from the external surface at 100 µm from the bracket edge. Data were compared by one-way analysis of variance and a chi-square test. PC 50 and PC 70 showed significantly greater SBS than Fuji Ortho FC Automix, although Transbond Plus showed significantly greater SBS than other bonding systems. No significant difference in the ARI category was observed among the five groups. For specimens bonded with PC 50 and PC 70, the hardness and elastic modulus values in most locations were equivalent to those of Fuji Ortho FC Automix. Experimental resin-based bonding material containing PC provides adequate SBS and a caries-preventive effect equivalent to that of the RMGIC adhesive system.

Novel experimental cements for use on the dentin-pulp complex

This aim of this study was to evaluate the physicochemical and biological properties of novel experimental cements (Hybrid, Paste and Resin) based on synergistic combinations of existing materials, including pH, diametral tensile strength (DTS) and cytotoxicity comparing them with mineral trioxide aggregate (MTA - Angelus®) and a glass ionomer cement (GIC) developed at our laboratory. For the physicochemical and biological tests, specimens with standard dimensions were produced. pH measurements were performed with digital pH meter at the following time intervals: 3, 24, 48 and 72 h. For the DTS test, cylindrical specimens were subjected to compressive load until fracture. The MTT assay was performed for cytotoxicity evaluation. Data were analyzed by ANOVA and Tukey's test (α=0.05). Paste group showed pH values similar to MTA, and Hybrid group presented pH values similar to GIC (p>0.05). The tested materials showed pH values ranging from alkaline to near neutrality at the evaluated times. MTA and GIC showed similar DTS values. The lowest and highest DTS values were seen in the Paste and Resin groups, respectively (p<0.05). Cell viability for MTA and experimental Hybrid, Paste and Resin groups was 49%, 93%, 90% and 86%, respectively, when compared with the control group. The photo-cured experimental resin cement showed similar or superior performance compared with the current commercial or other tested experimental materials.

Elution of chlorhexidine and BisGMA from an experimental adhesive resin

Elution of chlorhexidine and BisGMA from an experimental adhesive resin

Evaluation of antibacterial properties of Acrylate-Triclosan in experimental resin materials

Evaluation of antibacterial properties of Acrylate-Triclosan in experimental resin materials

A Novel Antibacterial Dental Resin Composite

This study reports the synthesis and evaluation of a novel furanone-containing antibacterial resin composite. Compres-sive strength (CS) and S. mutans viability were used to evaluate the mechanical strength and antibacterial activity of the composites. With 5% to 30% addition of the furanone derivative, the composite showed no change in CS but a significant antibacterial activity with a 16% - 68% reduction in the S. mutans viability. Further, the antibacterial activity of the modified composite was not affected by human saliva. The aging study implies that the modified composite may have a long-lasting antibacterial function. Within the limitations of this study, it appears that this experimental resin composite may potentially be developed into a clinically attractive dental restorative due to its high mechanical strength and antibacterial function.