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Objective This work measured the amount of bound versus unbound water in completely-demineralized dentin. Methods Dentin beams prepared from extracted human teeth were completely demineralized, rinsed and dried to constant mass. They were rehydrated in 41% relative humidity (RH), while gravimetrically measuring their mass increase until the first plateau was reached at 0.064 (vacuum) or 0.116 g H2O/g dry mass (Drierite). The specimens were then exposed to 60% RH until attaining the second plateau at 0.220 (vacuum) or 0.191 g H2O/g dry mass (Drierite), and subsequently exposed to 99% RH until attaining the third plateau at 0.493 (vacuum) or 0.401 g H2O/g dry mass (Drierite). Results Exposure of the first layer of bound water to 0% RH for 5 min produced a -0.3% loss of bound water; in the second layer of bound water it caused a -3.3% loss of bound water; in the third layer it caused a -6% loss of bound water. Immersion in 100% ethanol or acetone for 5 min produced a 2.8 and 1.9% loss of bound water from the first layer, respectively; it caused a -4 and -7% loss of bound water in the second layer, respectively; and a -17 and -23% loss of bound water in the third layer. Bound water represented 21-25% of total dentin water. Chemical dehydration of water-saturated dentin with ethanol/acetone for 1 min only removed between 25 and 35% of unbound water, respectively. Significance Attempts to remove bound water by evaporation were not very successful. Chemical dehydration with 100% acetone was more successful than 100% ethanol especially the third layer of bound water. Since unbound water represents between 75 and 79% of total matrix water, the more such water can be removed, the more resin can be infiltrated. © 2014 Academy of Dental Materials.

Dental Materials Volume 31, Issue 2, 1 February 2015, Pages e25-e32 Can quaternary ammonium methacrylates inhibit matrix MMPs and cathepsins? (Article) Tezvergil-Mutluay, A.a, Agee, K.A.b, Mazzoni, A.c, Carvalho, R.M.d, Carrilho, M.e, Tersariol, I.L.fg, Nascimento, F.D.h, Imazato, S.i, Tjäderhane, L.jk, Breschi, L.ce, Tay, F.R.b, Pashley, D.H.b a Adhesive Dentistry Research Group, Institute of Dentistry, University of Turku, Turku, Finland b Department of Oral Biology, College of Dental Medicine, Georgia Regents University, Augusta, GA, United States c Department of SAUandFAL, University of Bologna, Bologna, Italy View additional affiliations View references (31) Abstract Objective Dentin matrices release ICTP and CTX fragments during collagen degradation. ICTP fragments are known to be produced by MMPs. CTX fragments are thought to come from cathepsin K activity. The purpose of this study was to determine if quaternary methacrylates (QAMs) can inhibit matrix MMPs and cathepsins. Methods Dentin beams were demineralizated, and dried to constant weight. Beams were incubated with rh-cathepsin B, K, L or S for 24 h at pH 7.4 to identify which cathepsins release CTX at neutral pH. Beams were dipped in ATA, an antimicrobial QAM to determine if it can inhibit dentin matrix proteases. Other beams were dipped in another QAM (MDPB) to determine if it produced similar inhibition of dentin proteases. Results Only beams incubated with cathepsin K lost more dry mass than the controls and released CTX. Dentin beams dipped in ATA and incubated for 1 week at pH 7.4, showed a concentration-dependent reduction in weight-loss. There was no change in ICTP release from control values, meaning that ATA did not inhibit MMPs. Media concentrations of CTX fell significantly at 15 wt% ATA indicating that ATA inhibits capthesins. Beams dipped in increasing concentrations of MDPB lost progressively less mass, showing that MDPB is a protease-inhibitor. ICTP released from controls or beams exposed to low concentrations were the same, while 5 or 10% MDPB significantly lowered ICTP production. CTX levels were strongly inhibited by 2.5-10% MDPB, indicating that MDPB is a potent inhibitor of both MMPs and cathepsin K. Significance CTX seems to be released from dentin matrix only by cathepsin K. MMPs and cathepsin K and B may all contribute to matrix degradation.

This study determined if dentin proteases are denatured by phosphoric acid (PA) used in etch-and-rinse dentin adhesives. Dentin beams were completely demineralized with EDTA for 30 days. We “acid-etched” experimental groups by exposing the demineralized dentin beams to 1, 10, or 37 mass% PA for 15 sec or 15 min. Control beams were not exposed to PA but were incubated in simulated body fluid for 3 days to assay their total endogenous telopeptidase activity, by their ability to solubilize C-terminal crosslinked telopeptides ICTP and CTX from insoluble dentin collagen. Control beams released 6.1 ± 0.8 ng ICTP and 0.6 ± 0.1 ng CTX/mg dry-wt/3 days. Positive control beams pre-incubated in p-aminophenylmercuric acetate, a compound known to activate proMMPs, released about the same amount of ICTP peptides, but released significantly less CTX. Beams immersed in 1, 10, or 37 mass% PA for 15 sec or 15 min released amounts of ICTP and CTX similar to that released by the controls (p > 0.05). Beams incubated in galardin, an MMP inhibitor, or E-64, a cathepsin inhibitor, blocked most of the release of ICTP and CTX, respectively. It is concluded that PA does not denature endogenous MMP and cathepsin activities of dentin matrices.

Made available in DSpace on 2018-12-11T17:01:28Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-03-15 During dentin bonding with etch-and-rinse adhesive systems, phosphoric acid etching of mineralized dentin solubilizes the mineral crystallites and replaces them with bound and unbound water. During the infiltration phase of dentin bonding, solvated adhesive resin comonomers are supposed to replace all of the unbound collagen water and polymerize into copolymers. A recently published review suggested that dental monomers are too large to enter and displace water from tightly-packed collagen molecules. Conversely, recent work from the authors' laboratory demonstrated that HEMA and TEGDMA freely equilibrate with water-saturated dentin matrices. However, because adhesive blends are solvated in organic solvents, those solvents may remove enough free water to allow collagen molecules to come close enough to exclude adhesive monomer permeation. The present study analyzed the size-exclusion characteristics of dentin collagen, using a gel permeation-like column chromatography technique, filled with dentin powder instead of Sephadex beads as the stationary phase. The elution volumes of different sized test molecules, including adhesive resin monomers, studied in both water-saturated dentin, and again in ethanol-dehydrated dentin powder, showed that adhesive resin monomers can freely diffuse into both hydrated and dehydrated collagen molecules. Under these in vitro conditions, all free and some of the loosely-bound water seems to have been removed by ethanol. These results validate the concept that adhesive resin monomers can permeate tightly-bound water in ethanol-saturated collagen molecules during infiltration by etch-and-rinse adhesives. Statement of Significance It has been reported that collagen molecules in dentin matrices are packed too close together to allow permeation of adhesive monomers between them. Resin infiltration, in this view, would be limited to extrafibrillar spaces. Our work suggests that monomers equilibrate with collagen water in both water and ethanol-saturated dentin matrices. Department of Cariology and Operative Dentistry Tokyo Medical and Dental University Department of Prosthodontics Peking University School Hospital of Stomatology Department of Orthodontics and Pediatric Dentistry Universidade Estadual Paulista-UNESP Araraquara Dental School Department of Oral Biology Dental College of Georgia Augusta University Department of Biomedical and Neuromotor Sciences DIBINEM University of Bologna IGM-CNR Unit of Bologna Department of Biomaterials Faculty of Odontology University of Toulouse III Department of Materials Science Engineering Georgia Institute of Technology Department of Orthodontics and Pediatric Dentistry Universidade Estadual Paulista-UNESP Araraquara Dental School

Prolonged exposure of root dentin to calcium hydroxide alters the fracture resistance of dentin. Calcium silicate-based materials (CSMs) used in endodontics release calcium hydroxide on setting. This study examined whether prolonged contact of dentin with CSMs adversely affects its mechanical properties.Dentin beams prepared from extracted human molars (7 × 3 × 0.3 mm) were divided into 3 groups on the basis of the material to which dentin was exposed (Biodentine, MTA Plus, and untreated control beams). Three-point flexure to failure was performed for each beam at designated exposure times (24 hours, 1, 2, and 3 months; n = 10). Data were analyzed with 2-factor repeated-measures analyses of variance to determine the effects of material and aging time on flexural modulus, flexural strength, and modulus of toughness (α = 0.05).For flexural modulus, there was no significant difference for material (P = .947) or aging time (P = .064) when compared with baseline control. For flexural strength, significant differences were associated with aging time (P.001) but not with material (P = .349). Flexural strength of dentin exposed to Biodentine decreased significantly after 2 and 3 months, whereas that exposed to MTA Plus decreased significantly after 3 months of aging (P.05). For modulus of toughness, significant declines were observed for both material (P.004) and aging time (P.001).Both CSMs alter material toughness more than the strength and stiffness of dentin after aging in 100% relative humidity. Because dentin toughness is attributed to its collagen matrix, the amount of collagen extracted from mineralized dentin and changes in collagen ultrastructure should be further examined after exposure of dentin to CSMs.

Matrix metalloproteinases (MMPs) cause collagen degradation in hybrid layers created by dentin adhesives. This in vitro study evaluated the feasibility of using a cross-linking agent, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC), to inactivate soluble rhMMP-9, as an example of dentin MMPs, and matrix-bound dentin proteases. The inhibitory effects of 5 EDC concentrations (0.01-0.3 M) and 5 incubation times (1-30 min) on soluble rhMMP-9 were screened with an MMP assay kit. The same EDC concentrations were used to evaluate their inhibitory effects on endogenous proteinases from completely demineralized dentin beams that were incubated in simulated body fluid for 30 days. Decreases in modulus of elasticity (E) and dry mass of the beams, and increases in hydroxyproline content of hydrolysates derived from the incubation medium were used as indirect measures of matrix collagen hydrolysis. All EDC concentrations and pre-treatment times inactivated MMP-9 by 98% to 100% (p < 0.05) compared with non-cross-linked controls. Dentin beams incubated in 0.3 M EDC showed only a 9% decrease in E (45% decrease in control), a 3.6% to 5% loss of dry mass (18% loss in control), and significantly less solubilized hydroxyproline when compared with the control without EDC cross-linking (p < 0.05). It is concluded that EDC application for 1 min may be a clinically relevant and effective means for inactivating soluble rhMMP-9 and matrix-bound dentin proteinases if further studies demonstrate that EDC is not toxic to pulpal tissues.

Objective: This study evaluated the ability of benzalkonium chloride (BAC) to bind to dentine and to inhibit soluble recombinant MMPs and bound dentine matrix metalloproteinases (MMPs). Methods: Dentine powder was prepared from extracted human molars. Half was left mineralized; the other half was completely demineralized. The binding of BAG to dentine powder was followed by measuring changes in the supernatant concentration using UV spectrometry. The inhibitory effects of BAC on rhMMP-2, -8 and -9 were followed using a commercially available in vitro proteolytic assay. Matrix-bound endogenous MMP-activity was evaluated in completely demineralized beams. Each beam was either dipped into BAG and then dropped into 1 mL of a complete medium (CM) or they were placed in 1 mL of CM containing BAG for 30 days. After 30 days, changes in the dry mass of the beams or in the hydroxyproline (HYP) content of hydrolysates of the media were quantitated as indirect measures of matrix collagen hydrolysis by MMPs. Results: Demineralized dentine powder took up 10-times more BAG than did mineralized powder. Water rinsing removed about 50% of the bound BAC, whilst rinsing with 0.5 M NaCl removed more than 90% of the bound BAG. BAG concentrations 0.5 wt% produced 100% inhibition of soluble recombinant MMP-2, -8 or -9, and inhibited matrix-bound MMPs between 55 and 66% when measured as mass loss or 76-81% when measured as solubilization of collagen peptide fragments. Conclusions: BAC is effective at inhibiting both soluble recombinant MMPs and matrix-bound dentine MMPs in the absence of resins. (C) 2010 Elsevier Ltd. All rights reserved.

Objectives. The aim of this study was to compare the curing reaction of five experimental adhesive blends containing different photo-initiating systems. The hypothesis tested was that degree of conversion (DC) of resin blends is affected by resin type, solvent content and photo-initiating system. Methods. The experimental methacrylate resin blends were ranked from hydrophobic (R2) to hydrophilic (R3 and R4) and tested as neat, or solvated with 10% or 20% ethanol, or 10% ethanol and 10% water. Three different photo-initiators were used: IS-1 = 0.25% CQ (camphorquinone) + 1% EDMAB (ethyl 4-dimethylaminobenzoate); IS-2 = 1.25% TPO (diphenyl(2,4,6-trimethylbenzoyl)-phosphine oxide); IS-3 = 0.25% CQ+0.50% EDMAB+0.50% TPO. DC of resin blends was measured with a differential scanning calorimeter. Data were analyzed with a three-way ANOVA. Results. Neat resin type influenced DC, as R4 showed the highest values compared to R2 and R3 (p < 0.05). Solvent had a significant effect on DC (p < 0.05): dilution of resin blends with 10% or 20% ethanol or 10% ethanol + 10% water increased the DC of all resins, except for R4. Initiators influenced the polymerization since neat resins and mixtures solvated with 10% or 20% ethanol showed their highest DC values when polymerized with IS-1 or IS-3 (p > 0.05), while IS-2 or IS-3 increased the DC values of resins diluted with 10% ethanol and 10% water (p < 0.05). Conclusions. Water-compatible photo-initiators such as TPO should be included in the hydrophilic solvated adhesive formulation to ensure an appropriate DC of the adhesive layer. (C) 2009 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

It is thought that increasing the strength of the dentin matrix using crosslinking agents may improve both the strength and the durability of resin-dentin bonds. The purpose of this study was to evaluate the effect of two collagen crosslinking agents (glutaraldehyde, GD and grape seed extract, GSE) on the modulus of elasticity of demineralized dentin. Sound molar fragments were fully demineralized and divided into five groups according to the type and concentration of crosslinking agents: 2.5% GD; 5% GD, 25% GD; 0.65% GSE; 6.5% GSE. Specimens were immersed in their respective solution and tested at baseline, 10 min, 30 min, 1 h, 2 h, 4 h. The elastic modulus of dentin was significantly affected by the treatment (p < 0.01) and exposure time (p < 0.01). There was a statistically significant interaction between the two factors evaluated (treatment vs. time p < 0.01). Mean baselines values varied between 4.8 and 6.2 MPa in water; after 4 h of treatment the values increased between 34.9 and 242.5 MPa, that were treatment time and agent dependent. The use of these collagen crosslinkers to increase the stiffness of demineralized dentin, was both concentration and time dependent.

The aim of this study was to evaluate the ability of five experimental resins, which ranged from hydrophobic to hydrophilic blends, to seal acid-etched dentine saturated with water or ethanol. The experimental resins (R1, R2, R3, R4, and R5) were evaluated as neat bonding agents (100% resin) or as solutions solvated with absolute ethanol (70% resin/30% ethanol). Fluid conductance was measured at 20 cm H(2)O hydrostatic pressure after sound dentine surfaces were: (i) covered with a smear layer; (ii) acid-etched; or (iii) bonded with neat or solvated resins, which were applied to acid-etched dentine saturated with water or ethanol. In general, the fluid conductance of resin-bonded dentine was significantly higher than that of smear layer-covered dentine. However, when the most hydrophobic neat resins (R1 and R2) were applied to acid-etched dentine saturated with ethanol, the fluid conductance was as low as that produced by smear layers. The fluid conductance of resin-bonded dentine saturated with ethanol was significantly lower than for resin bonded to water-saturated dentine, except for resin R4. Application of more hydrophobic resins may provide better sealing of acid-etched dentine if the substrate is saturated with ethanol instead of with water.

Made available in DSpace on 2018-12-11T17:06:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-09-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) National Institute of Dental and Craniofacial Research Objective To determine if acid-etched, cross-linked dentin can be dehydrated without lowering bond strength below that of cross-linked wet-bonded dentin in vitro. Methods Using extracted human third molars, control acid-etched dentin was bonded with Single Bond Plus, using either the wet- or dry-bonding technique. Experimental acid-etched dentin was treated with 5 mass% grape seed extract (GSE) in different solvents for 1 min before undergoing wet vs dry resin-dentin bonding with Single Bond Plus. Completely demineralized dentin beams were treated with 5% GSE for 0, 1 or 10 min, before measuring stiffness by 3-point flexure. Other completely demineralized beams were treated similarly and then incubated in buffer for 1 week to measure the collagen solubilization by endogenous dentin proteases. Results 24 h microtensile bond strengths (μTBS) in wet and dry controls were 53.5 ± 3.6 and 9.4 ± 1.8 MPa, respectively (p 0.05). Cross-linking demineralized dentin with 5% GSE increased stiffness of dentin and decreased collagen degradation (p

This study evaluated the effect of incorporating increasing concentrations of sodium fluoride in incubation media, on the loss of dry mass and solubilization of collagen from demineralized dentin beams incubated for up to 7 days. The effect of fluoride on the inhibition of matrix-bound metalloproteinases (MMPs) was also measured.Dentin beams were completely demineralized in 10% phosphoric acid. After baseline measurements of dry mass, the beams were divided into six groups (n=10) and incubated at 37°C either in buffered media containing sodium fluoride (NaF) at 75, 150, 300, 450, 600 ppm or in fluoride-free media (control) for seven days. Following incubation, dry mass was re-measured. The incubation media was hydrolyzed with HCl for the quantitation of hydroxyproline (HYP) as an index of solubilization of collagen by endogenous dentin proteases. Increasing concentrations of fluoride were also evaluated for their ability to inhibit rhMMP-9.Addition of NaF to the incubation media produced a progressive significant reduction (p0.05) in the loss of mass of dentin matrices, with all concentrations demonstrating significantly less mass loss than the control group. Significantly less HYP release from the dentin beams was found in the higher fluoride concentration groups, while fluoride concentrations of 75 and 150 ppm significantly reduced rhMMP-9 activity by 6.5% and 79.2%, respectively.The results of this study indicate that NaF inhibits matrix-bound MMPs and therefore may slow the degradation of dentin matrix by endogenous dentin MMPs.

The purpose of this study was to determine if hydrophobic resins can be coaxed into dentin wet with ethanol instead of water. The test hypothesis was that dentin wet with ethanol would produce higher bond strengths for hydrophobic resins than would dentin wet with water. This study examined the microtensile bond strength of 5 experimental adhesives (50 wt% ethanol/50% comonomers) of various degrees of hydrophilicity to acid-etched dentin that was left moist with water, moist with ethanol, or air-dried. Following composite buildups, hourglass-shaped slabs were prepared from the bonded teeth for microtensile testing. For all 3 types of dentin surfaces, higher bond strengths were achieved with increased resin hydrophilicity. The lowest bond strengths were obtained on dried dentin, while the highest bond strengths were achieved when dentin was bonded moist with ethanol. Wet-bonding with ethanol achieved higher bond strengths with hydrophobic resins than were possible with water-saturated matrices.

This study examined the hypotheses that the use of a self-etching-adhesive improves the adhesion of EndoRez to dentin, and that both techniques are unaffected by the prolonged use of NaOCl when EDTA is used as the final rinse. A tensile bond testing design was employed with composite cylinders bonded to dentin using: (a) 17% EDTA-2 min/EndoRez; (b) 6.15% NaOCl-1 h/EDTA-2min/EndoRez; (c) EDTA-2 min/Clearfil Liner Bond 2V/EndoRez; and (d) NaOCl-1 h/EDTA-2min/Clearfil Liner Bond 2V/EndoRez. Fractographic analyses of debonded specimens were performed using SEM. Two-way ANOVA and Tukey test revealed higher tensile bond strengths with the self-etching-adhesive-modified EndoRez technique (p0.001). Sealer tags pulled away from dentinal tubules when EndoRez was used alone, whereas mixed failures occurred within sealer tags, hybrid layers, adhesive, and sealer in the self-etching-adhesive-modified EndoRez technique. Both techniques were unaffected by the prolonged use of NaOCl (p0.05) when EDTA was employed as the final rinse.

During dentin bonding, solvated adhesive comonomers are applied to water-saturated decalcified dentin matrices. When alcohol-solvated hydrophilic or hydrophobic methacrylate monomers are applied, they chemically remove water and cause matrix shrinkage during comonomer infiltration. Evaporation of solvent induces further shrinkage. The purpose of this work was to compare the shrinkage of water-saturated dentin matrices infiltrated with ethanol- or methanol-solvated 2-hydroxyethyl methacrylate (HEMA), 2,2-bis[4(2-hydroxy-3-methacryloyloxy-propyloxy)-phenyl] propane (BisGMA), or triethyleneglycol dimethacrylate (TEGDMA) at 90/10, 70/30, 50/50, and 30/70 mass fraction % alcohol/monomer before and after evaporation of alcohol. Thin (ca 0.2 mm) disks of human mid-coronal dentin were demineralized and placed in a well beneath the contact probe of a linear variable differential transformer (LVDT). The height of the matrix was measured before and after random application of one of the twelve alcohol/monomer mixtures. Matrix height was measured during infiltration and during solvent evaporation. Between trials, residual monomer was extracted using ethanol. These studies were repeated on specimens in which 100% alcohol was used to substitute for water in the matrix. Both studies revealed that matrices shrink 30-50% but that pretreatment of matrices with alcohol prevents BisGMA phase separations from occurring. Wet bonding with ethanol instead of water permits infiltration of relatively hydrophobic alcohol/monomers.

The aim of this study was to test the null hypothesis that the tensile properties of demineralized dentin are not influenced by the hydrogen bonding ability of anhydrous polar solvents.Dentin disks 0.5mm thick were prepared from mid-coronal dentin of extracted, unerupted, human third molars. 'I' beam and hour-glass shaped specimens were prepared from the disks, the ends protected with nail varnish and the central regions completely demineralized in 0.5M EDTA for 5 days. Ultimate tensile stress (UTS) and low-strain apparent modulus of elasticity (E) were determined with the specimens immersed for 60 min in water, methanol, HEMA, acetone or air prior to testing in those same media. Apparent moduli of elasticity were measured on the same specimens in a repeated measures experimental design. The results were analyzed with a one-way ANOVA on ranks, followed by Dunn's test at alpha=0.05. Regression analysis examined the relationship between UTS or E and Hansen's solubility parameter for hydrogen bonding (delta(h)) of each solvent.The UTS of demineralized dentin in water, methanol, HEMA, acetone and air was 18(7), 29(7), 31(6), 41(13) and 146(27)MPa, x(SD), n=10. Low-strain E for the same media were 11(7), 43(12), 79(21), 132(31) and 253(115)MPa. Regression analysis of UTS vs delta(h) revealed a significant (p0.0005, r=-0.69, R(2)=0.48) inverse, exponential relationship. A similar inverse relationship was obtained between low-strain E vs delta(h) (p0.0001, r=-0.93, R(2)=0.86).The tensile properties of demineralized dentin are dependent on the hydrogen bonding ability of polar solvents (delta(h)). Solvents with low delta(h) values may permit new interpeptide H-bonding in collagen that increases its tensile properties. Solvents with high delta(h) values prevent the development of these new interpeptide H-bonds.

Objectives . The submicron hiatus represents a potential space between the base of the collagen network and the mineralized dentin when dentin is acid-etched for bonding. These spaces were observed in SEM studies after acid-etched dentin specimens were critical point dried or dehydrated in hexamethyldisilasane. However, they have never been identified in TEM studies of dentin hybrid layers. This study critically examined the cause of submicron hiati formation using a silver staining technique to measure nanoleakage. Methods . Two multi-step, total-etch adhesives (One-Step, Bisco; Single Bond, 3M) and two single-step, self-etching adhesives (Prompt L-Pop, ESPE; One-Up Bond F, Tokuyama) were examined. Flat dentin surfaces were bonded with these adhesives and a lining composite. In each adhesive group, 0.8 mm thick slabs from the same bonded tooth were coated with nail varnish applied 1 mm from the bonded interfaces. The varnish was either left to dry completely for 10 min before immersing in 50 wt% silver nitrate (AgNO 3 ) for 24 h (group D), or painted on blotted tooth slabs that were immediately dropped into the AgNO 3 solution (group M). After developing, undemineralized, unstained, epoxy resin-embedded sections were prepared for transmission electron microscopy (TEM) to identify the amount and distribution of silver uptake. Results . Nanoleakage patterns were observed in all adhesive-bonded teeth, regardless of brand. Fine reticular silver deposits were also found in the underlying undemineralized dentin. In group D, submicron hiati were seen as tunnels of heavy silver deposits beneath hybrid layers. Specifically, a hiatus occurred between the undemineralized intertubular dentin and a cohesively fractured layer of the same matrix that was attached to the base of the hybrid layer. Hiati were completely absent in group M, regardless of the brand of adhesive. Significance . Submicron hiati are artifacts created by desiccation during specimen processing, and should be referred to as such in future studies of bonded dentin interfaces.

Objectives. This study examined the null hypothesis that there is no difference between the effect of a one versus two-layer applications of Prompt L-Pop (3M ESPE, Seefeld, Germany) to sound, abraded human coronal dentine. Methods. In group I, the mixed adhesive was applied for 15 s, and light-cured for 10 s. In group II, after light-curing the first layer, the adhesive was re-applied and light-cured. Specimens bonded with a hybrid composite were sectioned into beams for microtensile bond strength evaluation. Additional teeth from each group were bonded similarly using a lining composite for transmission electron microscopy examination of the resin–dentine interfaces, and nanoleakage evaluation using ammoniacal silver nitrate. Results. A significant difference (p

Objective The objective of this study was to determine if Gluma dentin desensitizer (5.0% glutaraldehyde and 35% HEMA in water) can inhibit the endogenous MMPs of dentin matrices in 60 s and to evaluate its effect on dentin matrix stiffness and dry mass weight. Methods Dentin beams of 2 mm × 1 mm × 6 mm were obtained from extracted human third molars coronal dentin. To measure the influence of Gluma treatment time on total MMP activity of dentin, beams were dipped in 37% phosphoric acid (PA) for 15 s and rinsed in water. The acid-etched beams were then dipped in Gluma for 5, 15, 30 or 60 s, rinsed in water and incubated into SensoLyte generic MMP substrate (AnaSpec, Inc.) for 60 min. Controls were dipped in water for 60 s. Additional beams of 1 mm × 1 mm × 6 mm were completely demineralized in 37% PA for 18 h, rinsed and used to evaluate changes on the dry weight and modulus of elasticity ( E ) after 60 s of Gluma treatment followed by incubation in simulated body fluid buffer for 0, 1 or 4 weeks. E was measured by 3-pt flexure. Results Gluma treatment inhibited total MMP activity of acid-etched dentin by 44, 50, 84, 86% after 5, 15, 30 or 60 s of exposure, respectively. All completely demineralized dentin beams lost stiffness after 1 and 4 weeks, with no significant differences between the control and Gluma-treated dentin. Gluma treatment for 60 s yielded significantly less dry mass loss than the control after 4 weeks. Significance The use of Gluma may contribute to the preservation of adhesive interfaces by its cross-linking and inhibitory properties of endogenous dentin MMPs.

Objective: Adding antimicrobial/anti-MMP quaternary ammonium methacrylates (QAMs) to comonomer blends should not weaken the mechanical properties of dental resins. This work evaluated the degree conversion and mechanical properties of BisGMA/TEGDMA/HEMA (60:30:10) containing 0-15 mass% QAMs A-E (A: 2-acryloxyethyltrimethyl ammonium chloride; B: [3-(methacryloylamino)propyl]trimethylammonium chloride; C: [2-(methacryloxy)ethyl] trimethyl ammonium chloride; D: diallyldimethyl ammonium chloride; E: 2-(methacryloyloxy) ethyltrimethyl ammonium methyl sulfate. Methods: Unfilled resins with and without QAM were placed on ATR-FTIR and light-polymerized for 20 s in a thin film at 30 °C. Unfilled resin beams were casted from square hollow glass tubings. Half of the beams were tested after 3 days of drying (control); the other half were tested wet after 3 days of water storage. Results: Addition of QAMs in control resins significantly increased conversion 600 s after light termination, with the exception of 5% MAPTAC (p < 0.05). Increase of QAM content within a formulation significantly increased conversion. Control beams gave dry Young's moduli of ∼700 MPa. Addition of 5, 10 or 15 mass% QAMs produced significant reductions in dry Young's moduli except for 5% B or C. 15 mass% A, B and C lowered the wet Young's moduli of the resin beams by more than 30%. The ultimate tensile stress (UTS) of control dry resin was 89 ± 11 MPa. Addition of 5-10 mass% QAMs had no adverse effect on the dry UTS. After water storage, the UTS of all resin blends fell significantly (p < 0.05), especially when 15 wt% QAMs was added. Control dry beams gave fracture toughness (KIC) values of 0.88 ± 0.1 MPa m1/2. Wet values were significantly higher at 1.02 ± 0.06 (p < 0.05). KIC of dry beams varied from 0.85 ± 0.08 at 5% QAMs to 0.49 ± 0.05 at 15% QAMs. Wet beams gave KIC values of 1.02 ± 0.06 MPa m1/2 that fell to 0.23 ± 0.01 at 15% QAMs. Significance: Addition of 10% QAMs increased the degree of conversion of unfilled resins, but lowered wet toughness and UTS; addition of 15% QAMs lowered the mechanical properties of wet resins below acceptable levels.

The purpose of this study was to test the null hypothesis that the re-expansion of dried matrix and the shrinkage of moist, demineralized dentin is not influenced by polar solvents. Dentin disks were prepared from midcoronal dentin of extracted human third molars. After complete demineralization in 0.5M of EDTA (pH 7), the specimens were placed in the well of a device that measures changes in matrix height in real time. Dry, collapsed matrices were created by blowing dry N(2) on the specimens until they shrank to a stable plateau. Polar solvents [water, methanol, ethanol, n-propanol, n-butanol, formamide, ethylene glycol, hydroxyethyl methacrylate (HEMA), or mixtures of water-HEMA] as model primers then were added and the degree of re-expansion measured. These same solvents also were applied to moist, expanded matrices and the solvent-induced shrinkages measured. Regression analysis was used to test the correlations between matrix height and Hansen's dispersive, polar, hydrogen bonding, and total solubility parameters (delta(d), delta(p), delta(h), delta(t)). The results indicate that water-free polar solvents of low hydrogen bonding (H-bond) ability (e.g., neat HEMA) do not re-expand dried matrices and that they shrink moist matrices. When HEMA was mixed with progressively higher water concentrations, the model water-HEMA primers expanded the dried matrix in proportion to their water concentrations and they produced less shrinkage of moist matrices. Solvents with higher H-bonding capacities (methanol, ethanol, ethylene glycol, formamide, and water) re-expanded the dried matrix in proportion to their solubility parameters for H-bonding (delta(h)). They also induced small transient shrinkages of moist matrices, which slowly re-expanded. The results require rejection of the null hypothesis.

Little research has been done to evaluate the effects of acids commonly used in adhesive dentistry, on the tensile properties of the demineralized dentin matrix. The purpose of this study was to evaluate the effects of a number of acidic conditioners on the ultimate tensile strength (UTS) and modulus of elasticity (E) of human coronal dentin matrix.Small hour-glass shaped (for UTS) or l-beam shaped (for determination of E) were prepared from mid-coronal dentin of extracted human third molars. After protecting the ends with varnish, the middle of the specimens was completely demineralized in 0.5 M EDTA (pH 7). UTS was determined by tensile stressing to failure. Modulus of elasticity was calculated from stress strain curves. The results were analyzed by ANOVA and Student-Neuman-Keuls test at the 95% confidence level.Brief (ca. 1-2 min) exposure of demineralized dentin matrix to acids had no measurable effects on its tensile properties. Ten-minute exposures to 2.5% and 17.5% nitric acid lowered (p0.05) the UTS compared to phosphate buffered saline (PBS)-exposed controls. Exposure of the decalcified dentin to 10% citric acid containing 3% ferric chloride, 10% citric acid, 37% phosphoric acid or 17.5% nitric acid containing 3% ferric chloride for 10 min had no effect on UTS. None of these acids consistently lowered stiffness.The results indicate that relatively long exposures to acids are required to alter the tensile properties of demineralized dentin. It is unlikely that the brief exposures to acids that are used in adhesive dentistry would acutely weaken the physical properties of demineralized dentin. However, long-term studies should be done to determine if such treatment increases the susceptibility of the matrix to hydrolysis.

The mineral phase of dentin is located primarily within collagen fibrils. During development, bone or dentin collagen fibrils are formed first and then water within the fibril is replaced with apatite crystallites. Mineralized collagen contains very little water. During dentin bonding, acid-etching of mineralized dentin solubilizes the mineral crystallites and replaces them with water. During the infiltration phase of dentin bonding, adhesive comonomers are supposed to replace all of the collagen water with adhesive monomers that are then polymerized into copolymers. The authors of a recently published review suggested that dental monomers were too large to enter and displace water from collagen fibrils. If that were true, the endogenous proteases bound to dentin collagen could be responsible for unimpeded collagen degradation that is responsible for the poor durability of resin-dentin bonds. The current work studied the size-exclusion characteristics of dentin collagen, using a gel-filtration-like column chromatography technique, using dentin powder instead of Sephadex. The elution volumes of test molecules, including adhesive monomers, revealed that adhesive monomers smaller than ∼1000 Da can freely diffuse into collagen water, while molecules of 10,000 Da begin to be excluded, and bovine serum albumin (66,000 Da) was fully excluded. These results validate the concept that dental monomers can permeate between collagen molecules during infiltration by etch-and-rinse adhesives in water-saturated matrices.

Made available in DSpace on 2014-12-03T13:10:45Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-03-01Bitstream added on 2014-12-03T13:23:00Z : No. of bitstreams: 1 WOS000332906100007.pdf: 424548 bytes, checksum: 3c472963dcb87490ac01c5a6126e73b0 (MD5) NIDCR Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Objectives: Published transmission electron microscopy analysis of in vitro resin-dentin bonds shows that, after 44 months, almost 70% of collagen fibrils from the hybrid layer disappear. Matrix metalloproteinases (MMPs) play an important role in that process and are thought to be the main factor responsible for the solubilization of dentin collagen. Therefore, this study aimed to evaluate the inactivation of matrix-bound MMPs by two different cross-linking agents, carbodiimide (EDC) or proanthocyanidin (PA), or the MMP-inhibitor, chlorhexidine (CHX), on acid-etched dentin using a simplified MMP assay method.Materials and Methods: Dentin beams (2x1x6 mm) were obtained from mid-coronal dentin of sound third molars and randomly divided into six groups (G) according to the dentin treatment: G1: Deionized water (control); G2: 0.1 M EDC; G3: 0.5 M EDC; G4: 0.5 M EDC + 35% hydroxyethyl methacrylate (HEMA); G5: 5% PA; and G6: 2% CHX. The beams were etched for 15 seconds with 37% phosphoric acid, rinsed, and then immersed for 60 seconds in one of the treatment solutions. The data were expressed both in absorbance values at 412 nm and in MMP-9 activity equivalents. The total MMP activity of dentin was analyzed for one hour by colorimetric assay (Sensolyte). Data were submitted to Wilcoxon nonparametric test and Mann-Whitney tests (p>0.05).Results: All experimental cross-linking solutions significantly reduced MMP activity from 79.8% to 95.2% when compared to the control group. No difference was observed among 0.1 M EDC (84.8%), 5% PA (87.6%), and 2% CHX (79.8%). Addition of 35% HEMA to 0.5 M EDC produced inactivation (95.2%) that was similar to that of 0.5 M EDC alone (92.7%).Conclusion: Dentin treatment with cross-linking agents is effective to significantly reduce MMP activity. Mixing 0.5 M EDC and 35% HEMA did not influence EDC inhibitor potential. Araraquara Sch Dent, Sao Paulo, Brazil FOAR UNESP, Dept Orthodont & Pediat Dent, Araraquara, Brazil Georgia Regents Univ, Augusta, GA USA Univ Trieste, Sch Dent, Trieste, Italy Ararquara Sch Dent, Dept Oral Biol, Sao Paulo, Brazil Georgia Regents Univ, Coll Dent Med, Dept Oral Biol, Augusta, GA USA FOAR UNESP, Dept Orthodont & Pediat Dent, Araraquara, Brazil NIDCRR01 DE015306 CNPq: 305204/2010-6 FAPESP: 12/08866-4

Introduction Calcium silicate–based materials (CSMs) are used in various endodontic procedures. The present study examined whether prolonged contact of mineralized dentin with recently commercialized versions of these materials adversely affects dentin collagen matrix integrity. Methods Dentin slabs prepared from extracted human third molars (7 × 3 × 0.3 mm) were divided into 3 groups on the basis of the material to which dentin was exposed (MTA Plus, Biodentine, untreated control dentin slabs) and the time period of exposure (24 hours, 1, 2, and 3 months; n = 6). Hydroxyproline assay was performed on each group’s supernatant to quantify the collagen extraction amounts of each group per time period. Data were analyzed with two-factor repeated-measures analysis of variance and Holm-Sidak pair-wise comparisons (α = 0.05) to determine the effects of material and aging time on collagen extraction. Dentin slabs from the 3 months of aging group were demineralized for transmission electron microscopy examination of collagen matrix ultrastructural changes. Results Material (P = .002), aging time (P < .001), and their interactions (P = .007) significantly affected the amount of hydroxyproline (pg/mg of mineralized dentin) extracted from mineralized dentin and were significantly correlated by power regression models. Collagen degradation was identified from the surface of dentin slabs that were in direct contact with CSMs. Conclusions Prolonged contact of mineralized dentin with CSMs has an adverse effect on the integrity of the dentin collagen matrix. However, the amount of collagen extracted was limited to the contact surface. Clinicians can continue to apply CSMs in endodontic procedures; however, caution is advised when these materials are applied to thin dentinal walls.

Endogenous dentin matrix metalloproteinases (MMPs) contribute to extracellular collagen matrix degradation in hybrid layers after adhesive dentin bonding procedures. Endodontic irrigants, including chlorhexidine and ethylenediaminetetraacetic acid (EDTA), might help protect the hybrid layer from this process. The objective of the present study was to determine the exposure time necessary for EDTA to inactivate endogenous MMP activity in human dentin.Dentin beams (2 × 1 × 3 mm) were prepared from mid-coronal dentin of extracted third molars. The beams were demineralized in 10 wt% phosphoric acid, which also activated endogenous MMPs, and were divided into 4 experimental groups on the basis of exposure time to 17% EDTA (0, 1, 2, or 5 minutes). A generic colorimetric MMP assay measured MMP activity via absorbance at 412 nm. Data were evaluated by Kruskal-Wallis analysis of variance, followed by Dunn pair-wise comparisons at α = 0.05.All exposure times resulted in significant inhibition (P.001) compared with unexposed controls. Specifically, percent inhibition for 1-, 2-, and 5-minute exposure times was 55.1% ± 21.5%, 72.8% ± 11.7%, and 74.7% ± 19.7%, respectively.Seventeen percent EDTA significantly inhibits endogenous MMP activity of human dentin within 1-2 minutes. This might minimize hybrid layer degradation after resin bonding procedures in the root canal space.

Matrix metalloproteinases (MMPs) bound to dentin contribute to the progressive degradation of collagen fibrils in hybrid layers created by dentin adhesives. This study evaluated the MMP-inhibiting potential of quaternary ammonium methacrylates (QAMs), with soluble rhMMP-9 and a matrix-bound endogenous MMP model. Six different QAMs were initially screened by a rhMMP-9 colorimetric assay. For the matrix-bound endogenous MMPs, we aged demineralized dentin beams for 30 days in calcium- and zinc-containing media (CM; control), chlorhexidine, or QAMs in CM to determine the changes in dry mass loss and solubilization of collagen peptides against baseline levels. The inhibitory effects of QAMs on soluble rhMMP-9 varied between 34 and 100%. Beams incubated in CM showed a 29% decrease in dry mass (p < 0.05), whereas beams incubated with QAMs showed only 0.2%-6% loss of dry mass. Significantly more solubilized collagen was detected from beams incubated in CM (p < 0.05). It is concluded that QAMs exhibited dentin MMP inhibition comparable with that of chlorhexidine, but required higher concentrations.

Objectives. While screening the activity of potential inhibitors of matrix metalloproteinases (MMPs), due to the limited water solubility of some of the compounds, they had to be solubilized in ethanol. When ethanol solvent controls were run, they were found to partially inhibit MMPs. Thus, the purpose of this study was to compare the MMP-inhibitory activity of a series of alcohols. Methods. The possible inhibitory activity of a series of alcohols was measured against soluble rhMMP-9 and insoluble matrix-bound endogenous MMPs of dentin in completely demineralized dentin. Increasing concentrations (0.17, 0.86, 1.71 and 4.28 mol/L) of a homologous series of alcohols (i.e. methanol, ethanol, propanols, butanols, pentanols, hexanols, the ethanol ester of methacrylic acid, heptanols and octanol) were compared to ethanediol, and propanediol by regression analysis to calculate the molar concentration required to inhibit MMPs by 50% (i.e. the IC(50)). Results. Using two different MMP models, alcohols were shown to inhibit rhMMP-9 and the endogenous proteases of dentin matrix in a dose-dependent manner. The degree of MMP inhibition by alcohols increased with chain length up to 4 methylene groups. Based on the molar concentration required to inhibit rhMMP-9 fifty percent, 2-hydroxyethylmethacrylate (HEMA), 3-hexanol, 3-heptanol and 1-octanol gave the strongest inhibition. Significance. The results indicate that alcohols with 4 methylene groups inhibit MMPs more effectively than methanol or ethanol. MMP inhibition was inversely related to the Hoy's solubility parameter for hydrogen bonding forces of the alcohols (i.e. to their hydrophilicity). (C) 2011 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

The progressive degradation of resin-dentin bonds is due, in part, to the slow degradation of collagen fibrils in the hybrid layer by endogenous matrix metalloproteinases (MMPs) of the dentin matrix. In in vitro durability studies, the storage medium composition might be important because the optimum activity of MMPs requires both zinc and calcium. Objective. This study evaluated the effect of different storage media on changes in matrix stiffness, loss of dry weight or solubilization of collagen from demineralized dentin beams incubated in vitro for up to 60 days. Methods. Dentin beams (1 mm x 2 mm x 6 mm) were completely demineralized in 10% phosphoric acid. After baseline measurements of dry mass and elastic modulus (E) (3-point bending, 15% strain) the beams were divided into 5 groups (n = 11/group) and incubated at 37 degrees C in either media containing both zinc and calcium designated as complete medium (CM), calcium-free medium, zinc-free medium, a doubled-zinc medium or water. Beams were retested at 3, 7, 14, 30, and 60 days of incubation. The incubation media was hydrolyzed with HCl for the quantitation of hydroxyproline (HOP) as an index of solubilization of collagen by MMPs. Data were analyzed using repeated measures of ANOVA. Results. Both the storage medium and the storage time showed significant effects on E, mass loss and HOP release (p < 0.05). The incubation in CM resulted in relatively rapid and significant (p < 0.05) decreases in stiffness, and increasing amounts of mass loss. The HOP content of the experimental media also increased with incubation time but was significantly lower (p < 0.05) than in the control CM medium, the recommended storage medium. Conclusions. The storage solutions used to age resin-dentin bonds should be buffered solutions that contain both calcium and zinc. The common use of water as an aging medium may underestimate the hydrolytic activity of endogenous dentin MMPs. (c) 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Objectives. To better comprehend the role of CHX in the preservation of resin-dentin bonds, this study investigated the substantivity of CHX to human dentin. Material and methods. Dentin disks (n = 45) were obtained from the mid-coronal portion of human third molars. One-third of dentin disks were kept mineralized (MD), while the other two-thirds had one of the surfaces partially demineralized with 37% phosphoric acid for 15 s (PDD) or they were totally demineralized with 10% phosphoric acid (TDD). Disks of hydroxyapatite (HA) were also prepared. Specimens were treated with: (1) 10 mu L of distilled water (controls), (2) 10 mu L of 0.2% chlorhexidine diacetate (0.2% CHX) or (3) 10 mu L of 2% chlorhexidine diacetate (2% CHX). Then, they were incubated in 1 mL of PBS (pH 7.4, 37 degrees C). Substantivity was evaluated as a function of the CHX-applied dose after: 0.5 h, 1 h, 3 h, 6 h, 24 h, 168 h (1 week), 672 h (4 weeks) and 1344 h (8 weeks) of incubation. CHX concentration in eluates was spectrophotometrically analyzed at 260 nm. Results. Significant amounts of CHX remained retained in dentin substrates (MD, PPD or TDD), independent on the CHX-applied dose or time of incubation (p < 0.05). High amounts of retained CHX onto HA were observed only for specimens treated with the highest concentration of CHX (2%) (p < 0.05). Conclusion. The outstanding substantivity of CHX to dentin and its reported effect on the inhibition of dentinal proteases may explain why CHX can prolong the durability of resin-dentin bonds. (C) 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Objectives. The purposes of this work were to quantitate the affinity and binding capacity of chlorhexidine (CHX) digluconate to mineralized versus demineralized dentin powder and to determine how much debinding would result from rinsing with water, ethanol, hydroxyethylmethacrylate (HEMA) or 0.5 M NaCl in water. Methods. Dentin powder was made from coronal dentin of extracted human third molars. Standard amounts of dentin powder were tumbled with increasing concentrations of CHX (0-30 mM) for 30 min at 37 degrees C. After centrifuging the tubes, the supernatant was removed and the decrease in CHX concentration quantitated by UV-spectroscopy. CHX-treated dentin powder was resuspended in one of the four debinding solutions for 3 min. The amount of debound CHX in the solvents was also quantitated by UV-spectroscopy. Results. As the CHX concentration in the medium increased, the CHX binding to mineralized dentin powder also increased up to 6.8 mu mol/g of dry dentin powder. Demineralized dentin powder took up significantly (p < 0.01) more CHX, reaching 30.1 mu mol CHX/g of dry dentin powder. Debinding of CHX was in the order: HEMA < ethanol < 0.05 M NaCl < water. The highest CHX binding to demineralized dentin occurred at 30 mM (1.5 wt.%). Significance. As CHX is not debound by HEMA, it may remain bound to demineralized dentin during resin-dentin bonding. This may be responsible for the long-term efficacy of CHX as an MMP inhibitor in resin-dentin bonds. (C) 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Objectives. This study evaluated the kinetics of water uptake and percent conversion in neat versus ethanol-solvated resins that were formulated to be used as dental bonding agents. Methods. Five methacrylate-based resins of known and increasing hydrophilicities (R1, R2, R3, R4 and R5) were used as reference materials. Resins were evaluated as neat bonding agents (100% resin) or they were solvated with absolute ethanol (95% resin/5% ethanol or 85% resin/15% ethanol). Specimens were prepared by dispensing the uncured resin into a circular mold (5.8 mm x 0.8 mm). Photo-activation was performed for 80 s. The water sorption/diffusion/solubility was gravimetrically evaluated, while the degree of conversion (DC) was calculated by Fourier-transform infrared spectroscopy. Results. Water sorption increased with the hydrophilicity of the resin blends. In general, the solvated resins exhibited significantly higher water sorption, solubility and water diffusion coefficients when compared to their corresponding neat versions (p < 0.05). The only exception was resin R1, the least hydrophilic resin, in which neat and solvated versions exhibited similar water sorption (p > 0.05). Addition of ethanol increased the DC of all resins tested, especially of the least hydrophilic, R1 and R2 (p < 0.05). Despite the increased DC of ethanol-solvated methacrylate-based resins, it occurs at the expense of an increase in their water sorption/diffusion and solubility values. Significance. Negative effects of residual ethanol on water sorption/solubility appeared to be greater as the hydrophilicity of the resin blends increased. That is, the use of less hydrophilic resins in dental adhesives may create more reliable and durable bonds to dentin. (C) 2009 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Objectives Resin-modified glass ionomers (RMGI) have demonstrated clinical success in their ability to minimize post-operative sensitivity of restorations. RMGIs have been recently introduced as paste-liquid systems for convenience of clinical usage. The objective of this study was to measure the ability of a new paste-liquid RMGI liner/base to reduce fluid flow through human dentin. Methods Dentin permeability was measured on human crown sections on etched dentin, using etched dentin as a model for the exposed tubules typical of root sensitivity, and permitting measurement of the maximum permeability. In the one group, the etched dentin was coated with the RMGI, and pre- and post-treatment permeability was measured on the coated dentin. In the second group, a smear layer was created on the dentin with sandpaper, then the samples were coated with the RMGI; permeability was measured on the smeared and coated dentin. Samples from each group were sectioned and examined via scanning electron microscopy (SEM). Results The new paste-liquid RMGI liner/base significantly reduced fluid flow through dentin, and exhibited excellent seal on dentin with either a smear layer or open tubules. SEM images show evidence that the RMGI infiltrated the smear layer with resin during placement, penetrated dentin tubules, and formed resin tags in acid-etched dentin. Conclusions Based on these results, combined with previous research on adhesion and microleakage, it is concluded that the new RMGI liner/base should minimize post-operative sensitivity in restorations.

This study evaluated the permeability properties of five experimental resin membranes that ranged from relatively hydrophobic to relatively hydrophilic to seal acid-etched dentin saturated with water or ethanol. The experimental resins (R1, R2, R3, R4, and R5) were evaluated as neat bonding agents or as solutions solvated with ethanol (70% resin/30% ethanol). The quality of dentin sealing by these experimental resins was expressed in terms of reflection coefficients calculated as the ratio of the effective osmotic pressure to the theoretical osmotic pressure of test solutions. The effective osmotic pressure produced across resin-bonded dentin was induced in hypertonic solutions (CaCl(2) or albumin) at zero hydrostatic pressure. The outward fluid flow induced by these solutions was brought to zero by applying an opposing negative hydrostatic pressure. The least hydrophilic resins blends, R1 and R2, exhibited significantly (p < 0.05) higher reflection coefficients than the most hydrophilic resins (R4 and R5) in both conditions of dentin saturation (water and ethanol). The reflection coefficients of neat resins were, in general, significantly higher when compared with their corresponding solvated versions in both conditions of dentin saturation. In dentin saturated with ethanol, bonding with neat or solvated resins, resulted in reflection coefficients that were significantly higher when compared with the results obtained in dentin saturated with water. Reflection coefficients of CaCl(2) (ca. 1 x 10(-4)) were significantly lower (p < 0.05) than for albumin (ca. 3 x 10(-2)). Application of hydrophobic resins may provide better sealing of acid-etched dentin if the substrate is saturated with ethanol, instead of water.

Higher 24-hour resin-dentin bond strengths are created when ethanol is used to replace water during wet bonding. This in vitro study examined if ethanol-wet-bonding can increase the durability of resin-dentin bonds over longer times. Five increasingly hydrophilic experimental resin blends were bonded to acid-etched dentin saturated with water or ethanol. Following composite build-ups, the teeth were reduced into beams for 24-hour microtensile bond strength evaluation, and for water-aging at 37°C for 3, 6, or 12 months before additional bond strength measurements. Although most bonds made to water-saturated dentin did not change over time, those made to ethanol-saturated dentin exhibited higher bond strengths, and none of them fell over time. Decreased collagen fibrillar diameter and increased interfibrillar spacing were seen in hybrid layers created with ethanol-wet-bonding. Increases in bond strength and durability in ethanol-wet-bonding may be due to higher resin uptake and better resin sealing of the collagen matrix, thereby minimizing endogenous collagenolytic activities.

Matrix metalloproteinases (MMPs) bound to dentin matrices are activated during adhesive bonding procedures and are thought to contribute to the progressive degradation of resin-dentin bonds over time. The purpose of this study was to evaluate the changes in mechanical, biochemical, and structural properties of demineralized dentin treated with or without chlorhexidine (CHX), a known MMP-inhibitor. After demineralizing dentin beams in EDTA or phosphoric acid (PA), the baseline modulus of elasticity (E) of each beam was measured by three-point flexure. Specimens were pretreated with water (control) or with 2% CHX (experimental) and then incubated in artificial saliva (AS) at 37 degrees C for 4 weeks. The E of each specimen was remeasured weekly and, the media was analyzed for solubilized dentin collagen at first and fourth week of incubation. Some specimens were processed for electron microscopy (TEM) immediately after demineralization and after 4 weeks of incubation. In EDTA and PA-demineralized specimens, the E of the control specimens fell (p < 0.05) after incubation in AS, whereas there were no changes in E of the CHX-pretreated specimens over time. More collagen was solubilized from PA-demineralized controls (p < 0.05) than from EDTA-demineralized matrices after I or 4 weeks. Less collagen (p < 0.05) was solubilized from CHX-pretreated specimens demineralized in EDTA compared with PA. TEM examination of control beams revealed that prolonged demineralization of dentin in 10% PA (12 h) did not denature the collagen fibrils. (C) 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 90B: 373-380, 2009

Objectives The setting time and the expansion in deionized water, phosphate-buffered saline (PBS), 20% fetal bovine serum (FBS)/80% PBS or hexadecane oil of experimental accelerated calcium-silicate cements and ProRoot MTA were evaluated. Study design Different compounds such as sodium fluoride, strontium chloride, hydroxyapatite, and tricalcium phosphate were separately added to a basic experimental calcium-silicate cement to test their effect on setting and expansion. The initial and final setting times were determined using appropriate Gilmore needles. A linear variable differential transformer (LVDT) device was used to test the restricted hygroscopic linear expansion over 180 minutes of cements immersed in different solutions. Results were statistically compared using a 2-way ANOVA test (cement type versus solution type). Results All experimental cements showed initial setting times between 28 and 45 minutes and final setting times between 52 and 80 minutes. MTA showed a final setting time of 170 minutes. Final setting time of all experimental cements was faster than MTA. All cements showed slight (0.04%-0.77%) expansion in water, PBS, or FBS/PBS. Only fluoride-containing cement showed a significant expansion in water (6.68%) and in PBS (6.72%). The PBS/FBS contamination significantly reduced the expansion of fluoride-containing cement (2.98%) and MTA (0.07%). In contrast, cements showed a slight shrinkage when immersed in hexadecane, especially fluoride-containing cement. Conclusions The study demonstrated that: (1) the setting time of calcium-silicate cements may be effectively reduced; (2) the expansion is a water dependent mechanism owing to water uptake, because no expansion occurred in cements immersed in oil; (3) a correlation between setting time and expansion in water and PBS exists; (4) fluorine-containing cement showed a significant expansion in water and in PBS; (5) the immersion in FBS/PBS strongly reduced the expansion of MTA and fluoride-doped cement suggesting that fluid contamination (ie, blood) during surgical procedures may greatly affect the expansion of some calcium-silicate cements.

Objectives. This study examined the extent of ethanol retention in five comonomer blends of experimental methacrylate-based dental adhesives, containing (10, 20, or 30 wt.%) ethanol, after solvent evaporation, as well as observing the effect of residual ethanol and exposure duration on degree of conversion (DC). The null hypothesis that was tested was that residual, unevaporated ethanol has no effect on the rate or extent of DC of polymerized adhesive resins. Methods. A known mass of each mixture was placed in glass wells and evaporated for 60 s. The mass of the mixtures before and after evaporation was measured, allowing calculation of the gravimetric ethanol loss/retention. Results. The concentration of retained ethanol increased significantly with ethanol concentration (p

Plasticization of polymers by water sorption lowers their mechanical properties in a manner that is predictable by the polarity of their component resins. This study tested the hypothesis that when adhesive resins were used to create resin-infiltrated dentin, the reductions in their flexural moduli after water storage would be lowered proportional to their hydrophilic characteristics. Three increasingly hydrophilic resin blends were used to fabricate polymer beams and macro-hybrid layer models of resin-infiltrated dentin for testing with a miniature three-point flexure device, before and after 1–4 weeks of water storage. Flexural modulus reductions in macro-hybrid layers were related to, and more extensive than, reductions in the corresponding polymer beams. Macro-hybrid layers that were more hydrophilic exhibited higher percent reductions in flexural modulus, with the rate of reduction proportional to the Hoy’s solubility parameters for total intermolecular attraction forces (δt) and polar forces (δp) of the macro-hybrid layers.

Objective. This study examined the ability of five comonomer blends (R1-R5) of methacrylate-based experimental dental adhesives solvated with 10 rnass% ethanol, at reducing the permeability of acid-etched dentin. The resins were light-cured for 20, 40 or 60s. The acid-etched dentin was saturated with water or 100% ethanol. Method, Human unerupted third molars were converted into crown segments by removing the occlusal enamel and roots. The resulting crown segments were attached to plastic plates connected to a fluid-filled system for quantifying fluid flow across smear layer-covered dentin, acid-etched dentin and resin-bonded dentin. The degree of conversion of the resins was measured using Fourier transform infrared spectroscopy. Result. Application of the most hydrophobic comonomer blend (RI) to water-saturated dentin produced the smallest reductions in dentin permeability (31.9, 44.1 and 61.1% after light-curing for 20, 40 or 60s, respectively). Application of the same blend to ethanol-saturated dentin reduced permeability of 74.1, 78.4 and 81.2%, respectively (p < 0.05). Although more hydrophilic resins produced larger reductions in permeability, the same trend of significantly greater reductions in ethanol-saturated dentin over that of water-saturated dentin remained. This result can be explained by the higher solubility of resins in ethanol vs. water. Significance. The largest reductions in permeability produced by resins were equivalent but not superior, to those produced by smear layers. Resin sealing of dentin remains a technique-sensitive step in bonding etch-and-rinse adhesives to dentin. (C) 2008 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Self-etching primers and adhesives contain very hydrophilic methacrylate monomers that result in high water sorptions by their polymers. Water sorption plasticizes the polymers and lowers their mechanical properties. The purpose of this work was to rank the hydrophilicity of a series of acidic primers by their Hoy's solubility parameters (delta) to determine if there was a significant relationship between the delta of polymers and their mechanical properties. A series of six acidic primer blends containing a fixed concentration of phenyl-P but variable amounts of 2-hydroxyethyl methacrylate (HEMA), 2,2 bi[4-(2-hydroxy-3-methacryloyloxy)propane (BisGMA), and triethylene-glycol dimethacrylate (TEGDMA) was formulated and their Hoy's solubility parameters calculated. The polymers were cast into small 'I' beams and light-cured. The modulus of elasticity (E) and ultimate tensile strength (UTS) were measured in dry polymers and after immersion in water for 24 h. The results showed significant correlations between E and UTS under dry or wet conditions. Both E and UTS fell significantly when the specimens were immersed in water. After water immersion, the E and UTS showed significant correlations with Hoy's delta(p) values. Both E and UTS correlated significantly with the BisGMA concentration of the polymers, either wet or dry. The percentage changes in E or UTS were significantly correlated with the water sorption of the polymers.

To review the use of a new resin-dentin bonding model called the macro-hybrid layer, to quantify resin uptake and matrix shrinkage during resin infiltration and solvent evaporation. A secondary purpose was to introduce the concept of ethanol-wet bonding where water-saturated acid-etched dentin is exchanged with ethanol to create ethanol-saturated dentin. Adhesive monomers seem to penetrate ethanol-saturated dentin more thoroughly than water-saturated dentin.

The purpose of this work was to determine if nonaqueous methacrylate monomer/alcohol mixtures could expand dried collapsed demineralized dentin matrix. Thin disks (ca. 200 μm) of human dentin were demineralized and placed in wells beneath contact probes of linear variable differential transformers. The probes were placed on water-saturated expanded matrices to record the shrinkage associated with drying. Monomer mixtures containing hydroxyethyl methacrylate, 2,2-bis[4-(2-hydroxy-3 methacryloyloxy)propoxyphenyl] propane, or triethyleneglycol dimethacrylate were mixed with methanol or ethanol at alcohol/monomer mass fraction % of 90/10, 70/30, 50/50, or 30/70. They were randomly applied to the dried matrices to determine the rate and magnitude of expansion; then shrinkage was recorded during evaporation of the alcohols. The results indicated that matrix expansion was positively correlated with the Hoy's solubility parameters for hydrogen bonding forces (δh) of the monomer/solvent mixtures (p < 0.001). Expansions were more rapid with methanol-containing than with ethanol-containing monomer mixtures. For the test solutions, triethyleneglycol dimethacrylate-containing mixtures produced the slowest rate of matrix expansion and hydroxyethyl methacrylate-containing mixtures the most rapid expansion. When the solvents were evaporated, the matrix shrank in proportion to the solvent content and the δh of the monomer-solvent mixtures. The results indicate that expansion of dried, collapsed dentin matrices requires that the δh of the mixtures be larger than 17 (J/cm3)1/2. The greater the δh of the monomer solutions, the greater the rate and extent of expansion. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2006

The bond strengths of resins to caries-affected dentin are low. This could be due to weakened organic matrix. The purpose of this work was to determine if the ultimate tensile strength (UTS) of excavated carious dentin is weaker than that of normal dentin. Soft caries was excavated from extracted human molars, and the tooth was vertically sectioned into slabs. Each slab was trimmed to an hourglass shape, parallel or perpendicular to the tubule direction. Half of the specimens were mineralized, while the other half were completely demineralized in EDTA. ANOVA on ranks showed that the three-factor interactions (mineralization, caries, tubule direction) were all significant (p < 0.0001), indicating that mineralization and tubule direction gave different UTS results in normal and caries-affected dentin. No significant differences were seen between the UTS of normal and and that of caries-affected demineralized dentin in the parallel or perpendicular group. The matrix of demineralized caries-affected dentin was as strong as that of normal demineralized dentin when tested in the same direction.

This study investigated the ability of One-Up Bond alone and mineral trioxide aggregate (MTA), with and without a secondary seal of One-Up Bond or SuperEBA to seal saucer-shaped perforation defects in human molars. Cusps were removed, roots were amputated, and endodontic therapy completed on 40 extracted teeth. A cylindrical hole was made in each tooth from the furcation area to the chamber, into which a section of steel tubing was cemented. Intracoronal saucer-shaped defects were created over the perforation. The teeth were restored with MTA, One-Up Bond, or MTA with a secondary seal of One-Up Bond or SuperEBA. The integrity of the seal was evaluated by fluid filtration. MTA alone leaked significantly more than One-Up Bond or MTA with either secondary seal at 24 h. At 1 month, MTA, MTA plus One-Up Bond, and One-Up Bond alone were equivalent.

To assess the convective and evaporative fluid movement across glass-ionomer treated dentin.Crown segments made from extracted human teeth, were divided into two groups of 14 teeth each. Each segment was cemented onto a plexiglass slab penetrated by a stainless steel tube, permitting filling of the pulp chamber with water. This set-up was attached to a device that measured fluid movement through the dentin in the crown segment. The experimental design involved repeated measurements of convective and evaporative fluid movements in each of the following conditions: smear layer-covered dentin, conditioned dentin, dentin after placement of one of two glass-ionomers (Fuji IX or Ketac-Molar), with and without a protective coating. The same water fluxes were remeasured after storage of the samples for 24 hours in distilled water.Statistical analysis of the results using ANOVA indicated a significant difference between the two measured water fluxes (P0.001). There was also a significant difference between the two materials (P0.001), with Ketac-Molar allowing higher permeability than Fuji IX. Conditioning the dentin surface with polyacrylic acid increased the convective water flux (P0.05) but did not change the evaporative water flux. Placement of the glass-ionomer material did not change the rate of spontaneous evaporation of water from the dentin, but the application of a coating agent reduced the evaporative water loss. These values were not significantly different when the specimens were stored for 24 hours.

Objectives. To evaluate the viscoelastic properties of demineralized dentin matrix. Stress – relaxation studies were done on matrices in tension and strain elongation or creep studies were done in both tension and compression. Methods. Mid-coronal dentin disks were prepared from extracted unerupted human third molars. Disks were 0.5 mm thick for stress – relaxation or tensile creep experiments and 0.2– 0.3 mm thick for compressive creep studies. ‘I’ beam specimens were prepared from dentin disks and the middle region was demineralized in 0.5 M EDTA (pH 7) for 4 days. The specimens were held in miniature friction grips in water and pulled at 100 m ms 21 to strains of 5, 10, 15 or 20% and then held for 10 min to follow the decay of stress over time. Creep was determined on demineralized dentin immersed in water in tension and in compression. Compressive creep was measured using an LVDT contact probe with loads of 0.02– 0.5 N. Strain data were converted to compliance – time curves (strain/stress) and expressed as total compliance ðJtÞ; instantaneous elastic compliance ðJoÞ; retarded elastic compliance ðJRÞ and viscous response ðt=hÞ or creep. Results. The dentin matrix exhibits both stress –relaxation and creep behavior. Stress – relaxation and tensile creep were independent of strain but compressive creep rates were inversely related to compressive strain. Creep values were about 10% at low compressive strains, but fell progressively to 1% at high strains. Compliance – time curves fell with stress and came closer together. However, tensile creep was about 3% regardless of the strain. Significance. The dentin matrix exhibits viscoelastic properties, but is not linearly viscoelastic. The relatively high creep rates of the matrix under low compressive loads may cause viscous deformations in poorly infiltrated hybrid layers in resin-bonded teeth under function. 2003 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.