Does Making An Adhesive System Radiopaque by Filler Addition Affect Its Bonding Properties?

PURPOSE: To evaluate the radiopacity, bond strength, and micromorphology of experimental filled dental adhesives. MATERIALS AND METHODS: Five experimental filled dental adhesives with different concentrations of radiopaque barium-borosilicate glass (wt%) [0 (R0), 30 (R30), 40 (R40), 50 (R50), and 60 (R60)] and the commercial adhesive Adper Single Bond 2 were used in this study. Specimens were prepared by dispensing the uncured resin into a mold (5.0 mm x 1.0 mm). Digital radiographs (n = 5) of both 1-mm-thick adhesive specimens and tooth were taken with a CCD sensor. The gray levels of enamel, dentin, and adhesive systems were measured by histogram analysis and compared. Adhesives were applied to flat dentin surfaces of third molars (n = 7). Resin composite buildups were constructed and sectioned to obtain resin-dentin bonded sticks to test immediately or after 6 months of water storage. Three specimens for each tooth were qualitatively analyzed using scanning electron microscopy. Data on bond strength and radiopacity were evaluated by two-way and one-way ANOVA, respectively, and Tukey's test (α = 0.05). RESULTS: All experimental filled dental adhesives showed radiopacity similar to enamel (p > 0.05) and most yielded significant reductions of bond strength over time. However, the R30 produced a radiopaque material without jeopardizing the bonding of the material to the dentin substrate. CONCLUSIONS: The addition of 30% barium-borosilicate oxide produced radiopaque adhesives without jeopardizing the bonding to the dental substrate.

Influence of the base and diluent monomer on network characteristics and mechanical properties of neat resin and composite materials.

This study evaluated the effect of the combination of two dimethacrylate-based monomers [bisphenol A diglycidyl dimethacrylate (BisGMA) or bisphenol A ethoxylated dimethacrylate (BisEMA)] with diluents either derived from ethylene glycol dimethacrylate (ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate) or 1,10-decanediol dimethacrylate (D3MA) on network characteristics and mechanical properties of neat resin and composite materials. The degree of conversion, maximum rate of polymerization and water sorption/solubility of unfilled resins and the flexural strength and microhardness of composites (after 24 h storage in water and 3 months storage in a 75 vol% ethanol aqueous solution) were evaluated. Data were analyzed with two-way ANOVA and Tukey's test (α = 0.05). The higher conversion and lower water sorption presented by BisEMA co-polymers resulted in greater resistance to degradation in ethanol compared with BisGMA-based materials. In general, conversion and mechanical properties were optimized with the use of long-chain dimethacrylate derivatives of ethylene glycol. D3MA rendered more hydrophobic materials, but with relatively low conversion and mechanical properties.

Effects of adding barium-borosilicate glass to a simplified etch-and-rinse adhesive on radiopacity and selected properties.

PURPOSE: To evaluate the radiopacity, ultimate tensile strength (UTS), microhardness (KHN), degree of conversion (DC), water sorption (WS) and solubility (SL) of experimental adhesives. MATERIALS AND METHODS: Five experimental adhesives with different concentrations of barium-borosilicate oxide microfillers [0% (R0), 30% (R30), 40% (R40), 50% (R50), 60% (R60)] were formulated based on the adhesive system Ambar (FGM). The adhesive Adper Single Bond 2 (SB, 3M ESPE) was used as commercial reference. For the radiopacity (n = 5), KHN (n = 5), WS (n = 10), and SL (n = 10) tests, adhesive disks were constructed (5.0 mm in diameter and 1.0 mm thick), while for UTS (n = 5), hourglass-shaped specimens with a cross-sectional area of 0.8 mm2 were used. The FTIR spectra of unpolymerized and polymerized adhesives were used to determine the DC. Data were submitted to a one-way ANOVA and Tukey's test (α = 0.05). RESULTS: All experimental adhesives showed radiopacity similar to enamel, except those of R0 and SB. Filler addition did not jeopardize the UTS, KHN, or WS of the filled adhesives in comparison with the unfilled version. Except for R40, filler addition reduced the SL. The filled adhesives showed lower DC when compared with R0, but the DC was similar or higher when compared with SB. CONCLUSIONS: The addition of barium-borosilicate glass up to 50% did not jeopardize the mechanical properties of the adhesive layer and seems to reduce its solubility.

New dimethacrylate monomers based on phenolphthalein and resveratrol for the application of dental materials.

Potential estrogenic effects and changes in fertility are some of the health problems associated with bisphenol A (BPA) derivatives used to produce some polymers, including dental materials that contain Bis-GMA. Those issues drove this study proposing the synthesis of methacrylate resveratrol and phenolphthalein monomers that, combined with diluent monomers, generate copolymers. Their key characteristics were determined and analyzed on the chemical structure-property perspective considering monomer planarity and flexibility based on molecular dynamic simulations. METHODS: Methacrylate resveratrol ((E)-5-(4-(methacryloyloxy)styryl)-1,3-phenylenebis(2-methylacrylate)), EMPM) and methacrylate phenolphthalein ((3-oxo-1,3-dihydroisobenzofuran-1,1-diyl)bis(4,1-phenylene)bis(2-methylacrylate)), DIFPM) were synthesized through the reaction of precursors with methacryloyl chloride. After monomers purification and spectroscopic characterization (FTIR and NMR), the following copolymers were produced: DIFPM/TEGDMA and Bis-GMA/TEGDMA, EMPM/HEMA and Bis-GMA/HEMA. Microhardness, degree of conversion, water sorption and contact angle data were statistically analyzed through one-way ANOVA and Tukey's test (p ≤ 0.05). RESULTS: The DIFPM molecular structure's reduced flexibility proved to be an important factor to inhibit TEGDMA cyclization. In turn, the EMPM molecule's high planarity modified the spatial organization of the HEMA copolymer, altering the water diffusion and, therefore, the water sorption when compared to Bis-GMA copolymers. CONCLUSION: The scientific findings contribute to better understand the effect of monomer chemical structures, molecular geometry, and planarity on some physicochemical properties of copolymers. Knowledge that can contribute to the design of new monomers to replace Bis-GMA.

Characteristics of persons with an eating disorder and type 1 diabetes and psychological comparisons with persons with an eating disorder and no diabetes.

OBJECTIVES: Describe characteristics of patients who have both an eating disorder and type 1 diabetes and compare their responses on psychological tests with those with an eating disorder and no diabetes at time of initial assessment to an eating disorder facility. METHOD: A chart audit conducted on all 48 patients with ED-DMT1 who were seen collaboratively by the diabetes and eating disorder treatment teams between 2005 and 2008 at Park Nicollet Health Services and 96 (1:2) matched eating disordered controls. RESULTS: Diabetes was diagnosed an average of 10.2 years (SD = 9.4) before the diagnosis of an eating disorder; HbA1c at initial assessment was 11% (±3.2%). Those without diabetes reported greater depression (p = .048) and greater state and trait anxiety (p = .015 and p = .039, respectively) at initial assessment. DISCUSSION: Persons with both an eating disorder and type 1 diabetes were less psychologically compromised than their matched cohorts with an eating disorder only. These findings may not remain constant during the course of treatment.

Synthesis and characterization of experimental endodontic sealers containing bioactive glasses particles of NbG or 45S5.

OBJECTIVE: This study evaluated the influence of adding bioactive glasses particles [Niobophosphate (NbG) or bioglass (45S5)] into endodontic cements in relation to physical, chemical and biological properties. METHODS: The following commercial cements were used as comparison: AH Plus (Dentsply), Endofill (Dentsply), MTA Fillapex (Angelus) and EndoSequence (BC Sealer, Brasseler). Setting time, radiopacity, flow rate, weight loss/variation, alkaline capacity (pH) at different time-intervals (24h/48h/7d/14d/28d), bioactivity (assessed under SEM/EDS, FTIR/ATR and XDR) and cell viability were measured. Data were analyzed by One-way ANOVA/Holm-Sidak post-test (α = 5%) (normal distribution) and Kruskal-Wallis/Students-Newman-Keuls post-test (α = 5%) (non-normal distribution). RESULTS: Bioactive endodontic experimental cements (containing NbG or 45S5) had high alkalinization capacity. The experimental cements presented high weight loss/variation (p < 0.001). 45S5 experimental cement did not present radiopacity (p < 0.001). AH Plus had the lowest cell cytotoxicity when compared to the other tested cements (p < 0.001). Regarding bioactivity, SEM/EDS analyses showed precipitates with high concentrations of Ca/P for 45S5 and NbG, as well as for MTA Fillapex and BC Sealer. AH plus and Endofill did not present bioactive precipitates. FTIR/ATR and XDR analyses found hydroxyapatite precursors for NbG, 45S5, MTA Fillapex and BC Sealer. SIGNIFICANCE: The incorporation of bioactive particles (NbG or 45S5) into endodontic cements had potential to neutralize acidic environments and induced formation of hydroxyapatite precursors. Clinically, these would produce a cement that is bactericidal and have the potential to improve tissue healing. The improved radiopacity and flowability would facilitate the visualization of the material in the radiograph and the filling of anatomical complexities during root canal obturation. As drawbacks, the excessive weight loss and post-setting cytotoxicity could result in clinical degradation of the cement and adjacent tissue irritation for the patient.

Improvement of exposure times: effects on adhesive properties and resin-dentin bond strengths of etch-and-rinse adhesives.

PURPOSE: This study evaluated the effect of prolonged polymerization times on the microtensile resin-dentin bond strength (µTBS), degree of conversion of adhesive films (DC) and silver nitrate uptake (SNU) for an ethanol/water- (Adper Single Bond 2, [SB]) and an acetone-based (One Step Plus, [OS]) etch-and-rinse adhesive. MATERIALS AND METHODS: Thirty caries-free extracted molars were included in this study. The occlusal enamel of all teeth was removed by wet grinding the occlusal enamel on 180-grit SiC paper. Adhesives were applied according to the manufacturer's instructions, but they were light cured for 10, 20 and 40 s at 600 mW/cm2. Bonded sticks (0.6 mm2) were tested in tension (0.5 mm/min). Two bonded sticks from each tooth were immersed in an ammoniacal solution of silver nitrate (24 h), photodeveloped (8 h), and analyzed by SEM. The DC of the adhesives was evaluated under Fourier Transformed Infra-Red spectroscopy (FTIR). Data for each property were analyzed by two-way ANOVA and Tukey's test (α = 0.05). RESULTS: Statistically higher µTBS and DC were observed for SB and OS when both adhesives were light cured for 40 s in comparison with 10 s. For OS, the µTBS in the 20- and 40-s groups did not differ statistically, while for SB it did. Higher prolonged exposure times did not prevent nanoleakage within the hybrid layer for all groups regardless of the adhesive. CONCLUSION: This study supports the hypothesis that exposure times longer than those recommended can improve the degree of conversion of adhesive films and the immediate resin-dentin bonds. The prolonged curing times (20 and 40 s) for polymerization of simplified adhesives resulted in an increase in the degree of conversion of the adhesive films and resin-dentin bond strengths but did not reduce the nanoleakage within the hybrid layer.

Effects of increased exposure times of simplified etch-and-rinse adhesives on the degradation of resin-dentin bonds and quality of the polymer network.

One of the reasons for resin-dentin degradation is poor polymerization of the adhesive layer. This study evaluated the effect of prolonged polymerization times on the immediate and 6-month resin-dentin bond strengths, silver nitrate uptake, and polymer quality of etch-and-rinse adhesives. Thirty extracted teeth were obtained, and a flat dentin surface was exposed on each tooth. Adhesives (Adper Single Bond 2 and One Step Plus) were applied to the dentin surface of these teeth and light-cured for 10, 20, or 40 s at 600 mW cm(-2) . Bonded sticks (0.6 mm(2) ) were tested in tension (0.5 mm min(-1) ) and analyzed, after immersion in 50% silver nitrate, using scanning electron microscopy. The polymer quality of adhesive films was evaluated using thermogravimetric analysis. Statistically higher bond strengths were observed for both adhesives when light-cured for 40 s. Degradation of dentin bonds occurred under all experimental conditions but it was less pronounced for adhesives light-cured for 40 s. Longer exposure times reduced silver nitrate uptake for Adper Single Bond 2. Solvent retention and the amount of residual monomer were statistically lower when both adhesives were light-cured for 40 s. Although longer exposure times than those recommended cannot prevent degradation of the dentin bonds, they can increase bond strength, probably because of the removal of an increased amount of solvent and the presence of a lower amount of residual monomer.

Bioactive bacterial cellulose membrane with prolonged release of chlorhexidine for dental medical application.

Bioabsorbable barrier membrane is desired in dental medicine for treatment of periodontal diseases caused by different types of bacteria. Bioactive and bioabsorbable bacterial cellulose (BC) is a promising material for such application. However, a key challenge to implement this approach is produce BC membranes selectively oxidized and loaded with a bactericide, in order to modulate bioabsortion time and bactericide effect, respectively. In the present study, the drug model chlorhexidine (CHX) was chosen and NaIO4 was used as oxidizing agent. To modulate CHX release and efficacy, inclusion complexes of CHX with ß-cyclodextrin (CHX:ßCD) were synthesized. A linear dependence between degree of oxidation (DO) and oxidant concentration was found (DO = 2.07 + 45 [NaIO4]). CHX has strong chemical interaction with cellulose structure, contributing for its significant retention. The association of membrane oxidation and formation of the inclusion complex with ßCD causes a 10-fold increase in CHX release rate compared to unmodified cellulose. Thus, validating the concept that CHX release can be modulated using these two strategies. All membranes loaded with CHX inhibited S. aureus, E. coli and C. albicans growth, but DABC+CHX:ßCD showed greater inhibition zone (p < 0.05). That, associated with other results, indicates potential application as bioactive and bioabsorbable membrane.

Development of calcium phosphate/ethylene glycol dimethacrylate particles for dental applications.

This study describes the synthesis of dicalcium phosphate dihydrate (DCPD) particles in the presence of different ethylene glycol dimethacrylates (EGDMA, ethylene glycol/EG units: 1, 2, 3 or 4) at two monomer-to-ammonium phosphate molar ratios (1:1 and 2:1), as a strategy to develop CaP-monomer particles with improved interaction with resin matrices. Particles displaying high surface areas and organic contents were added to a photocurable BisGMA-TEGDMA resin and the resulting materials were tested for degree of conversion (DC), biaxial flexural strength (BFS), flexural modulus, and ion release. Data were subjected to one-way ANOVA or Kruskal-Wallis/Dunn test (alpha: 0.05). Functionalization with EGDMA derivatives was dependent upon the length of the spacer group and monomer concentration in the synthesis. No differences in DC were observed among materials (p > 0.05). A 39% increase in BFS was obtained with the use of particles with the highest functionalization level compared to non-functionalized particles (p < 0.001). The use of functionalized DCPD reduced flexural modulus in comparison to non-functionalized particles (p < 0.001). Calcium release was similar among materials and remained constant during the experiment, while phosphate release was higher at 7 days in comparison to the remaining weeks (p < 0.001). In conclusion, diethylene glycol dimethacrylate resulted in the highest functionalization levels and the highest BFS among DCPD-containing materials. Ion release was not affected by functionalization. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2018. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 708-715, 2019.

Evaporating solvents with a warm air-stream: effects on adhesive layer properties and resin-dentin bond strengths.

OBJECTIVES: This study evaluated the effect of a warm or cold air-dry stream for solvent evaporation on the microtensile resin-dentin bond strength (muTBS), nanoleakage pattern (SEM), degree of conversion (DC) and solvent evaporation rates (SE) of an ethanol/water- (Adper Single Bond, [SB] 3MESPE) and an acetone-based (Prime & Bond 2.1, [PB] Dentsply), two-step etch-and-rinse adhesive system. MATERIALS AND METHODS: Adhesives were applied on demineralized dentin surfaces. For SE, a warm or cold air-dry stream (10 s) was applied prior to light-activation (10 s). Bonded sticks (0.8mm2) were tested in tension (0.5 mm/min). Two bonded sticks from each tooth were immersed in a 50% (w/v) solution of silver nitrate (24 h), photodeveloped (8 h) and analyzed by SEM. The DC and solvent evaporation rate of the adhesives were evaluated under FTIR and analytical balance, respectively. Data were analyzed by two-way ANOVA and Tukey test (alpha=0.05). RESULTS: Higher muTBS and lower nanoleakage were observed when the SE step was performed with warm air-dry stream. However, the DC of the adhesives was not altered by the use of a warm air-dry. CONCLUSIONS: The use of a warm air-dry stream seems to be a clinical tool to improve the bond strength and the quality of the hybrid layer (less nanoleakage infiltration), since it might reduce the number of pores within the adhesive layer.

Bioactivity and properties of an adhesive system functionalized with an experimental niobium-based glass.

OBJECTIVE: This study evaluated the incorporation of niobophosphate bioactive glass (NbG) fillers into a commercial adhesive resin. MATERIALS AND METHODS: The silanized (NbGs) or non-silanized (NbG) NbG was added to the commercial adhesive system One Step (OS) at 30% by weight; unfilled adhesive served as control. The bioactivity of adhesives was analyzed by SEM and FTIR/ATR after 28 days in PBS. The adhesives were evaluated as regards microtensile bond strength immediately and after six months (n = 6); degree of conversion (n = 3), microhardness (n = 5); and radiopacity (n = 3). Data from each test were submitted to ANOVA and Tukey tests (P <0.05). RESULTS: FTIR/ATR analysis showed phosphate and carbonate precipitates on the NbG adhesive specimen surface. Statistical analysis of microtensile bond strength values showed that material x time interaction was not significant, but NbG group values were similar to those of unfilled adhesive (p <0.05). Addition of NbG did not alter the degree of conversion, but did increase microhardness and radiopacity values of the adhesive systems compared with those of the control group (OS). Incorporation of NbG into the adhesive system did not compromise the properties of the adhesive. CONCLUSION: A smart adhesive system with bioactive properties, high radiopacity, microhardness, and similar bond strength and degree of conversion was obtained by incorporating 30% by weight of NbG.

Ion-releasing dental restorative composites containing functionalized brushite nanoparticles for improved mechanical strength.

OBJECTIVES: This study describes the synthesis of brushite nanoparticles (CaHPO4·2H2O) functionalized with triethylene glycol dimethacrylate (TEGDMA) and their application in dental restorative composites with remineralizing capabilities. METHODS: Nanoparticles were synthesized, with TEGDMA being added to one of the precursor solutions at three different molar ratios (0:1, 0.5:1 and 1:1, in relation to the ammonium phosphate precursor). Then, they were added (10 vol%) to a photocurable dimethacrylate matrix containing 50 vol% of reinforcing glass particles. The resulting composites were tested for degree of conversion, biaxial flexural strength and elastic modulus (after 24h and 28days in water), and ion release (over a 28-day period). Commercial composites (one microhybrid and one microfilled) were tested as controls. RESULTS: The final TEGDMA content in the functionalizing layer was modulated by the molar ratio added to the precursor solution. Functionalization reduced nanoparticle size, but did not reduce agglomeration. Improved mechanical properties were found for the composite containing nanoparticles with higher TEGDMA level in comparison to the composite containing non-functionalized nanoparticles or those with a low TEGDMA level. All brushite composites presented statistically significant reductions in strength after 28 days in water, but only the material with high-TEGDMA nanoparticles retained strength similar to the microhybrid commercial control. Overall, ion release was not affected by functionalization and presented steady levels for 28 days. SIGNIFICANCE: Though agglomeration was not reduced by functionalization, the improvement in the matrix-nanoparticle interface allowed for a stronger material, without compromising its remineralizing potential.

Adhesives Doped with Bioactive Niobophosphate Micro-Filler: Degree of Conversion and Microtensile Bond Strength.

To evaluate the effect of incorporating niobium phosphate bioactive glass (NbG) into commercial etch-and-rinse adhesive systems, with and without silane, on their degree of conversion (DC) (%) and microtensile bond strength (µTBS). The NbG micro-filler was added to two etch-and-rinse adhesive systems: One Step (OS) and Prime & Bond (PB) at 40% concentration. The following groups were formed: control without glass addition OS; addition of unsilanized NbG (OSNbG); addition of silanized NbG (OSNbGS); control without glass PB; addition of unsilanized NbG (PBNbG); addition of silanized NbG (PBNbGS). The DC was determined using total Fourier spectroscopy reflection (FTIR/ATR). For µTBS testing, 48 human third molars (n=8) were restored and sliced to obtain specimens (0.8 mm2) and they were tested at two different time intervals: immediately and after 6 months. The fracture mode was evaluated with a stereoscopic loupe (40×) and by scanning electron microscopy (SEM). The data were subjected to ANOVA and Tukey tests (a=0.05). NbG addition did not compromise the adhesive system DC values (p>0.05). Furthermore, the NbG added to the adhesive systems did not affect µTBS values (p>0.05). Fracture occurred predominantly at the dentin-adhesive interface. NbG bioactive glass did not affect the DC or microtensile bond strength results.

Poly(ethylene-co-methyl acrylate) membranes as rate-controlling barriers for drug delivery systems: characterization, mechanical properties and permeability.

Poly(ethylene-co-methyl acrylate) (EMA) membranes with different amounts of methyl acrylate (MA) content were studied in terms of the thermal and mechanical properties, swelling and drug permeation. The increase in MA content in the copolymer significantly increased the percentage of elongation and decreased the tensile strength and modulus of elasticity of the membranes. The degree of swelling of the EMA membranes increased with the ethanol composition and MA content. The contact angle of a sessile drop (10 microL of ethanol/water solution) decreased with an increase in the ethanol fraction suggesting that the membrane wettibility increased with the ethanol content. The flux of diltiazem hydrochloride increased from 0.012 to 0.018 mg cm(-2)h(-1) with an increase in the MA content from 16.5 to 29.0%. By increasing the ethanol fraction from 0.4 to 1.0, the flux of diltiazem hydrochloride into the membranes with 29.0% MA, increased from 2.56 (+/-0.09) x 10(-3) to 18.38 (+/-0.62) x 10(-3) mg cm(-2)h(-1). The permeability coefficient increased from 5.85 x 10(-6) to 3.53 x 10(-4) cm h(-1) with an increase in the ethanol fraction. The flux can also be correlated with the drug solubility in the membrane and ethanol. For example, the solubilities of diltiazem hydrochloride, paracetamol and ibuprofen were 0.64, 6.68 and 504.48 mg cm(-3) in the membrane, respectively. Under the same conditions, the flux for the above mentioned drugs was 0.08 (+/-0.01), 0.53 (+/-0.01) and 45.11 (+/-2.00) mg cm(-2)h(-1).

Characterization and drug-permeation profiles of microporous and dense cellulose acetate membranes: influence of plasticizer and pore forming agent.

The use of pore forming agents and plasticizers are efficient ways to obtain membranes for controlled drug permeation through polymeric membranes. The challenge of the present study was to combine these two strategies to obtain cellulose acetate (CA) membranes, where poly(caprolactone triol) (PCL-T) was used as a plasticizer and water, dissolved in a casting solution, was used as a pore forming agent. First, the influence of water on membrane morphology, porosity and the permeation coefficient of a model drug (paracetamol) was analyzed. The influence of different amounts of PCL-T on the permeation coefficient of the CA membranes was then evaluated. Finally, both strategies were combined to obtain porous CA/PCL-T membranes. The membrane microstructure was analyzed using scanning electron microscopy (SEM), the CA crystallinity was determined via differential scanning calorimetry (DSC), and membrane permeability was investigated using paracetamol. The addition of water, a non-solvent, during the membrane casting process was found to be a simple and effective way to change membrane porosity and consequently the drug-permeation profile. When small quantities of non-solvent were used to obtain low porosity membranes, the presence of a plasticizer agent could be used to better modulate drug permeation. Combining the addition of PCL-T with the use of a non-solvent resulted in a series of CA membranes with paracetamol-permeation coefficient values in the range of ca. 10(-7) to 10(-5) cm s(-1).

Fracture toughness and cyclic fatigue resistance of resin composites with different filler size distributions.

OBJECTIVES: To verify the influence of filler size distributions on fracture toughness (KIc), initial fracture strength (IFS) and cyclic fatigue resistance (CFR) of experimental resin composites. METHODS: Four composites were prepared with same inorganic content (78 wt%), in which 67 wt% was constituted by glass particles with d50 of 0.5; 0.9; 1.2; 1.9 µm KIc of the composites was determined by the single-edge notched beam (SENB) method. To evaluate the IFS and the CFR a biaxial bending test configuration was used. The CFR was determined under cyclic loading for 10(5) cycles using the 'staircase' approach. The fracture surfaces of IFS and CFR specimens were analyzed under scanning electron microscope (SEM). RESULTS: There was a positive linear correlation between d50 vs. KIc and statistical difference was found only between C0.5 (1.24±0.10 MPa m0.5) and C1.9 (1.41±0.17 MPa m0.5). There were no statistical differences among IFS means, which ranged from 155.4±18.8 MPa (C0.9) to 170.7±23.1 MPa (C1.2). C0.5 (93.0±18.6a MPa) showed the highest and C0.9 the lowest CFR (82.5±8.0c MPa). There was no correlation between CFR with d50 values or with KIc means. SEM images showed the morphology with brittle fracture patterns for the surfaces of IFS specimens and a more smooth fracture surface for CFR specimens. SIGNIFICANCE: Resin composites showed different failure mechanisms for quasi-static and fatigue loading. For KIc and IFS, composites with larger filler size distributions showed better results due to crack deflection; while under cyclic loading, viscous behavior was predominant and composites with smaller particles showed higher fatigue resistance.

Mechanical properties and modeling of drug release from chlorhexidine-containing etch-and-rinse adhesives.

OBJECTIVES: To evaluate the effects of chlorhexidine (CHX) addition in different concentrations into simplified etch-and-rinse adhesives on the ultimate tensile strength (UTS), water sorption (WS), solubility (SO) and the rate of CHX release over time. METHODS: We added CHX diacetate to Ambar [AM] (FGM) and XP Bond [XP] (Dentsply) in concentrations of 0, 0.01, 0.05, 0.1 and 0.2 wt%. For UTS (n=10 for each group), adhesive specimens were constructed in an hourglass shape metallic matrix with cross-sectional area of 0.8 mm(2). Half of specimens were tested after 24 h and the other half after 28 days of water storage in tension of 0.5 mm/min. For WS and SO (n=10 for each group), adhesive discs (5.8 mm×1.0 mm) were prepared into a mold. After desiccation, we weighed and stored the cured adhesive specimens in distilled water for evaluation of the WS, SO and the cumulative release of CHX over a 28-day period. For CHX release (n=10 for each group), spectrophotometric measurements of storage solution were performed to examine the release kinetics of CHX. We subjected data from each test to ANOVA and Tukey' test (α=0.05). RESULTS: XP Bond adhesive showed significantly more WS and SO and lower UTS than Ambar. In general, the addition of CHX did not alter WS, SO and UTS of the adhesives. XP showed a higher CHX release than AM (p<0.05) in all concentrations and the final amount of CHX release was directly proportional to the initial CHX concentration added to the adhesives. After 28 days of water storage, approximately 20% of CHX was released from XP and 8.0-12.0% from AM. CONCLUSIONS: Addition of CHX to commercial adhesive is a feasible method to provide a controlled release of CHX over time without jeopardizing WS, SO and UTS of the adhesives. SIGNIFICANCE: Manufacturers should consider adding CHX to commercial adhesives to provide a controlled release of CHX over time.

Effects of diphenyliodonium salt addition on the adhesive and mechanical properties of an experimental adhesive.

OBJECTIVES: The aim of this study was to assess the microtensile bond strength (µTBS), nanoleakage (NL), nano-hardness (NH) and Young's modulus (YM) of resin-dentine bonding components formed by an experimental adhesive system with or without inclusion of diphenyliodonium salt (DPIH) in the camphorquinone-amine (CQ) system. METHODS: On 12 human molars, a flat superficial dentine surface was exposed by wet abrasion. A model simplified adhesive system was formulated (40 wt.% UDMA/MDP, 30 wt.% HEMA and 30 wt.% ethanol). Two initiator systems were investigated: 0.5 mol% CQ+1.0 mol% EDMAB and 0.5 mol% CQ+1.0 mol% EDMAB+0.2 mol% DPIH. Each adhesive was applied and light-cured (10s; 600 mW/cm(2)). Composite build-ups were constructed incrementally and resin-dentine specimens (0.8mm(2)) were prepared. For NL, 3 bonded sticks from each tooth were coated with nail varnish, placed in the silver nitrate, polished down with SiC papers and analysed by EDX-SEM. NH and YM were performed on the hybrid layer in 2 bonded sticks from each teeth. The remaining bonded sticks were tested on µTBS (0.5mm/min). The data from each test were submitted to a Student t-test (α=0.05). RESULTS: No significant difference was found for µTBS between groups (p>0.05). Significant lower NL and higher NH and YM were found in the hybrid layer and adhesive layer produced with the iodinium salt-containing adhesive (p<0.05). CONCLUSIONS: The inclusion of the DPIH to the traditional CQ is a good strategy to improve the adhesive and mechanical properties of a simplified etch-and-rinse adhesive system.

Determining the influence of type 1 diabetes on two common eating disorder questionnaires.

PURPOSE: This research evaluated the level of influence that having type 1 diabetes (T1DM) has on responses to questions about food choices, eating concerns, dietary restraint, and others that are included on two widely used, validated eating disorder (ED) questionnaires and examined responses to these two questionnaires from patients with T1DM and an eating disorder (ED-T1DM) and an ED-no-diabetes. METHOD: An expert panel rated each item on the Eating Disorders Examination Questionnaire (EDE-Q) and Eating Disorders Inventory, version 3 (EDI-3) regarding T1DM level of influence on item interpretation. These questionnaires were completed by 2 matched samples (ED-T1DM, n = 48 and ED-no-diabetes, n = 96); responses were compared between the samples with particular attention to items of high T1DM influence. RESULTS: The expert panel identified that 50% (19/38) of the items on the EDE-Q and 6.6% (6/91) on the EDI-3 could be highly influenced by having T1DM. Before Bonferroni correction, the 2 groups responded statistically different on 9 out of 38 items on the EDE-Q and 27 out of 91 items on the EDI-3; generally responses were healthier for those with ED-T1DM than ED-no-diabetes. Of these items, on the EDE-Q, 5 were rated high T1DM influence and on the EDI-3, 3 were rated high. CONCLUSION: Having T1DM influences responses on ED questionnaires developed for the general population. This influence may be greater when questionnaires focus on eating, weight, and shape and result in misinterpretation of total and subscale scores by even well-trained clinicians. A careful review of individual item responses by the treatment team is warranted.