Biomedical subjects

Manuel Toledano

Publications and source records attributed to Manuel Toledano.

At least 19 recordsLinked to original sources

PubMed2007

Polymerization kinetics and mechanical characterization of new formulations of light-cured dental sealants.

The aim of the study was to develop and evaluate the in vitro performance of a new and simplified formulation of photocuring resin to be used as dental sealant. Two experimental dental sealants (CYTED1 and CYTED2) were formulated and their kinetic of polymerisation and physico-chemical properties were studied and compared to those of two commercially available sealants (Helioseal, Delton-FS). Rates of photoinitiated polymerisation (Rp), as well as the conversions and the quantum yields of polymerisation (phi(p)) were calculated. Flexural strength, Young's modulus, microhardness, microleakage, water sorption, and solubility were also tested. ANOVA, Student-Newman-Keuls, Pearson correlation and Kruskal-Wallis tests were used (p < 0.05). The highest Rp and phi(p) were obtained for the sealant CYTED2, Rp and phi(p) were similar for CYTEDl and Helioseal, and the lowest for Delton. Water sorption values were similar for Helioseal and CYTED2 being higher for CYTED1 and lower for Delton. No differences were found for solubility and microleakage values. Mechanical properties were better for Delton and no differences were found within the rest of the sealants. At short irradiation times (30 s), the maximum effectiveness of the photoinitiating system was obtained by the experimental CYTED2.

Dental Stress Analysis↗

PubMed2006

Novel light-cured resins and composites with improved physicochemical properties.

OBJECTIVES: The aim of this study was to determine the effect of two new diluent agents (Bis-GMA analogues), at different dilution levels and filler contents on relevant physicochemical properties of several novel resins and composites containing Bis-GMA as matrix. Composites using TEGDMA as diluent were used as control. METHODS: Twenty formulations were prepared combining three monomer mixtures (Bis-GMA/TEGDMA, Bis-GMA/CH(3) Bis-GMA and Bis-GMA/CF(3) Bis-GMA), at three dilution levels (85/15, 10/90, 0/100) and two percentages of filler loading (silanated barium aluminosilicate glass): 0%, 10%, 35%. Preliminary rheological testing was performed in order to obtain the viscosity of the resin samples. Resins and composites were then inserted into molds and light-cured (500mW/cm(2)). The properties evaluated were: (1) homogeneity of curing (HC), using FTIR or Vickers microindentor, (2) microhardness, by a Vickers microindentor, (3) depths of cure and oxygen inhibitor effect (OIE), quantified by scraping, (4) water contact angle on the materials surface, (5) water sorption and solubility, performed by the Oysaed-Ruyter method and (6) scanning electron microscopy analysis of the specimens surfaces. Data were analyzed by ANOVA and Student-Newman-Keuls tests (p<0.05). RESULTS: Materials with CH(3) Bis-GMA and CF(3) Bis-GMA exhibited less hydrophilicity, water sorption and solubility. Bis-GMA dilution induced an increase in depth of cure and promoted a higher OIE, particularly when the diluent was TEGDMA. Filler loading reduced the OIE and increased hydrophobicity of the resins. SIGNIFICANCE: CH(3) Bis-GMA may be considered as good candidate to be used as diluent because when replacing TEGDMA-induced lower hydrolytic degradation and increase in HC.

Acrylic Resins↗

PubMed2006

Resistance to degradation of resin-dentin bonds using a one-step HEMA-free adhesive.

OBJECTIVE: To evaluate the resistance to degradation of resin-dentin bonds formed with a one-step acetone-containing and HEMA-free adhesive. METHODS: Flat, mid-coronal dentin surfaces were bonded with G Bond under dry and wet conditions. The bonded teeth were subjected to fatigue loading (90 or 250 N) using 5000 or 50000 cycles (at 3.0 Hz) and to chemical degradation (10% NaOCl immersion for 5 h). Specimens were sectioned into beams and tested for microtensile bond strength. Fractographic analysis was performed by scanning electron microscopy (SEM). Additional specimens were processed for morphological examination of the interfaces. RESULTS: Bond strength significantly decreased after the chemical challenge (p<0.05), but not after load cycling. Dentinal moisture did not affect bond strength. Most of the recorded failures were adhesive and located at the top of the hybrid layer. A poorly infiltrated hybrid layer with bubbles entrapped within the adhesive was observed in all groups. CONCLUSIONS: A discrepancy between water/solvent evaporation rate and convective and evaporative water fluxes from the underlying dentin may be responsible of the droplet formation within the adhesive layer, thus reducing bond strength. A "stress relieving" effect may occur during loading. A loss of bonding effectiveness is expected overtime, mainly due to chemical degradation of the hybrid layer.

Acetone↗

PubMed2006

Durability of resin-dentin bonds: effects of direct/indirect exposure and storage media.

OBJECTIVES: To evaluate the longevity of resin-dentin bonds of three adhesives using different storage media and specimen size. METHODS: Flat dentin surfaces from extracted human third molars were bonded with: a two-step etch-and-rinse self-priming adhesive (Single Bond), a two-step self-etching adhesive (Clearfil SE Bond), and a one-step self-etching adhesive (One-Up Bond F). Composite build-ups were constructed. The bonded teeth were stored under three conditions: dry, distilled water, or mineral oil. Half of the specimens were stored as intact bonded teeth (Indirect Exposure/IE). The other half were first sectioned into beams and stored under same conditions (Direct Exposure/DE). After storage periods of 24h, 3 months or 1 year, the intact teeth (IE) were sectioned into beams and both subgroups (DE and IE) were tested for microtensile bond strengths. Results were analyzed with multiple ANOVA and Student-Newman-Keuls tests. Fractographic analysis was performed by SEM. RESULTS: After 24h, Single Bond and Clearfil SE Bond performed equally and were superior to One-Up Bond F. After 3 months of DE to water storage, decreases in bond strengths were observed for Single Bond and One-Up Bond F, this decrease occurred for Clearfil SE Bond after 12 months of water storage. Bonded specimens aged in dry did not alter bond strengths over time. Bond strength increased when Single Bond was stored in mineral oil after 3 and 12 months. Micromorphological alterations were evident after water storage. SIGNIFICANCE: Although dentin bond strength of all the adhesives fell over time in DE, SE Bond fells the least.

Acid Etching, Dental↗

PubMed2006

Effect of simulated pulpal pressure on dentin permeability and adhesion of self-etch adhesives.

OBJECTIVES: Dentin bonds made with one-bottle etch-and-rinse and self-etch adhesives are affected by the formation of interfacial blisters, porosities and deterioration. The first objective of this study was to evaluate the fluid flow through resin-dentin interfaces created by self-etching adhesives applied to deep dentin using a replica technique and by directly measuring dentin permeability (P). The second objective was to examine the effect of intrapulpal pressure on the microtensile bond strength of these adhesives. METHODS: A fluid-transport model was used to measure the fluid permeability (%P) through different adhesives. Impressions of bonded dentin were taken with a polyvinylsiloxane impression material to monitor fluid transudation from the surface of the adhesive. Positive replicas were fabricated for SEM examination. Two groups of resin-bonded specimens (pulpal pressure versus no pulpal pressure) were created for microtensile bond strength evaluation. Adhesive application was performed under 0 cm H(2)O. Pulpal pressure group was submitted to 20 cm H(2)O of pulpal pressure during build-up procedures. RESULTS: Clearfil Protect Bond exhibited the lowest permeability and fewest numbers of fluid droplets over the surface of the bonded dentin. G-Bond and Clearfil-S3 Bond were more permeable than Clearfil Protect Bond. One Up Bond F was the most permeable adhesive. A highly significant correlation was observed between the relative permeability of these adhesives (%P) and the number of fluid droplets on the adhesive surfaces. The application of pulpal pressure significantly reduced bond strength. SIGNIFICANCE: Resin-dentin bonds created by contemporary self-etch adhesives are susceptible to fluid permeation induced by pulpal pressure. HEMA-based adhesives showed the largest reductions in bond strengths after pulpal pressure application.

Acid Etching, Dental↗

PubMed2006

Reactivation of inactivated endogenous proteolytic activities in phosphoric acid-etched dentine by etch-and-rinse adhesives.

Auto-degradation of collagen matrices occurs in resin-infiltrated dentine by the slow action of host-derived matrix metalloproteinases. As phosphoric acid-etching inactivates these endogenous enzymes, it is puzzling how hybrid layers created by simplified etch-and-rinse adhesives can degrade in vivo. This study tested the null hypothesis that there are no differences in the relative proteolytic activities of mineralised dentine, acid-etched dentine, and etch-and-rinse adhesive-treated acid-etched dentine. Powdered dentine prepared from extracted human teeth was treated with 17% EDTA, 10% phosphoric acid, or with five simplified etch-and-rinse adhesives that were applied to 10% phosphoric acid-etched dentine. The gelatinolytic activity of the dentine powder was assayed using fluorescein-labelled gelatine. TEM examination of the air-dried, treated dentine powder was performed to confirm the presence of remnant mineralised dentine after acid-etching. 17% EDTA significantly reduced the relative proteolytic activity (73.2%) of the untreated mineralised dentine powder (control), while 10% phosphoric acid-etched dentine exhibited the highest reduction (98.1%). Treating the acid-etched dentine powder with any of the five simplified etch-and-rinse adhesives resulted in the reactivation of the proteolytic activity, with a significant negative linear correlation (P<0.05) between the increases in fluorescence and the corresponding pH values of the adhesives. It is concluded that simplified etch-and-rinse adhesives can reactivate endogenous enzymatic activities in dentine that are previously inactivated by phosphoric acid-etching. The amount of enzyme reactivated may even exceed the original quantity present in untreated mineralised dentine. This provides an explanation for the degradation of hybrid layers after acid-etched dentine matrices are infiltrated with these adhesives.

Dentin↗

PubMed2006

Improving the quality of the quartz fiber postcore bond using sodium ethoxide etching and combined silane/adhesive coupling.

The influence of different silane/dentin adhesives on the microtensile bond strengths of a hybrid composite to sodium ethoxide-etched quartz fiber posts was investigated. A prehydrolyzed silane was applied without an adhesive and compared to two-component systems in which hydrolysis of the silane occurred after mixing with the acidic monomer present in the dentin adhesives. Nanoleakage along post/core interfaces was examined after silver nitrate tracer penetration using scanning electron microscopy. Higher interfacial strengths and more uniform adaptation between the etched fiber post surface and the composite core were recorded after post treatment with silane/adhesive couplings. The combination of silane with two-step self-etch adhesives improves the chemical retention of composites around etched fiber posts with minimal nanoleakage. Although the one-step self-etching adhesive/silane combination enhances post adhesion, the extensive nanoleakage provides channels for rapid water sorption that may expedite hydrolytic degradation of the post/core interface.

Composite Resins↗

PubMed2006

Differential effect of in vitro degradation on resin-dentin bonds produced by self-etch versus total-etch adhesives.

OBJECTIVE: To evaluate the effect of an in vitro challenge (NaOCl immersion) on microtensile bond strength (MTBS) of five adhesive systems to dentin. METHODS: Flat dentin surfaces from 40 molars were bonded with three total-etch adhesives (Single Bond, Prime&Bond NT and the experimental Prime&Bond XP), and two self-etching agents (Clearfil SE Bond and Etch&Prime 3.0). Composite build-ups were constructed with Tetric Ceram. Teeth were then sectioned into beams of 1.0 mm2 cross-sectional area. Half of the beams were immersed in 10% NaOCl aqueous solution for 5 h. Each beam was tested in tension in an Instron machine at 0.5 mm/min. Data were analyzed by 2-way ANOVA and multiple comparisons tests (p < 0.05). RESULTS: Clearfil SE Bond and Single Bond attained higher MTBS than the other three adhesives. Prime&Bond NT and Prime&Bond XP performed equally, and Etch&Prime resulted in the lowest MTBS. After NaOCl immersion, MTBS decreased in all groups. The highest MTBS values were obtained for Clearfil SE Bond and Prime&Bond XP. Scaning electron microscopy observation of debonded sticks evidenced dissolution and microstructural alterations of intertubular dentin, except when Clearfil SE Bond was used. CONCLUSIONS: Resin-dentin bonds are prone to chemical degradation. The extent of the resin degradation is adhesive system specific. Chemical degradation of the nonresin infiltrated collagen fibers does also exist in total-etch adhesives. Both processes may reduce long-term resin-dentin bond strength.

Biocompatible Materials↗

PubMed2006

Sorption and solubility testing of orthodontic bonding cements in different solutions.

To evaluate and compare the solubility and sorption of orthodontic bonding cements after immersion in different solutions, five different cements were used: a fluoride-containing resin composite, a light-cured glass ionomer cement, a light-cured resin composite, a paste-paste chemically cured resin composite, and a liquid-paste chemically cured resin composite. Five different solutions were employed: distilled water, artificial saliva, an alcohol-free mouthrinse solution (Orthokin), a 5% alcohol mouthrinse solution (Perioaid), and a 75% ethanol/water solution. Five disc specimens (15 mm x 0.85 mm) were used for each experimental condition. Materials were handled following manufacturers' instructions and were ground wet with silicon carbide paper. Solubility and sorption of the materials were calculated by means of weighing the samples before and after immersion and desiccation. Data were analyzed by two-way ANOVA and Student-Newman-Keuls test (p < 0.05). The light-cured glass ionomer cement showed the lowest solubility and the highest sorption values. When using alcohol-containing solutions as storage media, solubility of the paste-paste chemically cured resin composite increased, and sorption values for the tested chemically cured resin composites were also increased. The use of alcohol-free mouthrinses does not affect sorption and solubility of orthodontic cements. The chemically cured (paste-paste) composite resin cement, requiring a mixing procedure, was the most affected by immersion in alcohol-containing solutions.

Absorption↗

PubMed2006

Effects of adhesive systems and luting agents on bonding of fiber posts to root canal dentin.

The study evaluated the influence of different luting materials on the microtensile bond strength of glass fiber posts to root canal dentin. Thirty extracted maxillary premolars were endodontically treated, and the roots were prepared for post cementation using the FRC Postec system (Vivadent). Two luting materials (Multilink, Vivadent and Clearfil Photo Core, Kuraray) were used in combination with three adhesive: Multilink Primer (Vivadent), Clearfil Photo Bond, and Clearfil New Bond (Kuraray). A composite build-up was performed around the root to provide adequate gripping during testing. Specimens were cut to obtain beams with the post in the center and with the radicular dentin overlaid by the composite build-up on each side. Microtensile testing was performed with a universal testing machine at a cross-head speed of 0.5 mm/min. The failure mode was classified under a stereomicroscope and four representative beams of each group were selected for SEM analysis. Bond strength data that were analyzed with two-way ANOVA and Student-Newman-Keuls multiple comparisons tests revealed that adhesive systems, luting materials, and the interaction between these two factors significantly influenced the bond strength results (p < 0.01). Multilink applied with its own adhesive system obtained the best results, while the lowest bond strength was achieved with clearfil photo core in combination with multilink primer.

Adhesives↗

PubMed2006

A simple etching technique for improving the retention of fiber posts to resin composites.

Coupling of fiber posts to composites is hampered by absence of chemical union between epoxy resins and methacrylate-based resins. This study examined a clinically feasible protocol for creating micromechanical retention on the surface of fiber posts, using hydrogen peroxide etching to remove the surface layer of epoxy resin. This was followed by silanization of the exposed quartz fibers to enhance their chemical bonding to composites. Etching with 24% H2O2 for 10 min or 10% H2O2 for 20 min produced a 50 microm thick surface zone that is depleted of epoxy resin, leaving intact, undamaged quartz fibers for silanization. Low viscosity flowable composites were employed to infiltrate this zone, to simulate the creation of hybrid layers in acid-etched dentin by dentin adhesives. Interfacial strengths were enhanced with the adjunctive use of H2O2 etching and silanization, and were probably dependent on the ability of the flowable composites to completely infiltrate this interdiffusion zone.

Barium Compounds↗

PubMed2005

Effect of temperature on the silane coupling agents when bonding core resin to quartz fiber posts.

OBJECTIVES: To evaluate the effect of different silane agents and air-drying temperatures on bond strength of translucent quartz fibre posts to composite resin. METHODS: The post surface was etched with 10 vol% hydrogen peroxide for 20 min. A two-liquid coupling agent containing 4-methacryolxyethyl trimellitate anhydride (4-META) and gamma-trimethoxysilyil propyl methacrylate (gamma-MPTS) and two pre-hydrolyzed single component silanes containing 3-methacryloxypropyltrimethoxysilane (3-MPS) and glycid-oxi-propyl-trimetil-oxi-silane (GPS), respectively, were used for treating the fiber posts. Two different post-silanization drying temperatures were applied (21 and 38 degrees C). A dual-cure composite resin (Core Paste XP) was selected to build-up the core around posts, obtaining cylindrical specimens that were serially cut in beams and subsequently loaded in tension (muTBS) at a cross-head speed of 1 mm/min until failure. Bond strength data were statistically analyzed by two-way ANOVA and Student-Newman-Keuls tests (alpha=0.05). RESULTS: Warm air-drying determined significantly higher bond strengths (p<0.001) for glycid-oxi-propyl-trimetil-oxi-silane (11.6 MPa) and 4-methacryolxyethyl trimellitate anhydride/gamma-trimethoxysilyil propyl methacrylate silane (11.7 MPa). These two systems exhibited lower bond strengths (6.9 and 8.8 MPa, respectively) than 3-methacryloxypropyltrimethoxysilane (11.0 MPa) when dried at 21 degrees C. No statistical differences were recorded for 3-methacryloxypropyltrimethoxysilane when drying at 21 or 38 degrees C. SIGNIFICANCE: The composition of the silane coupling agent in terms of acidic content, solvent rate or degree of hydrolysis may influence resin/post bond strength when dried at 21 degrees C. Drying at 38 degrees C most likely facilitates the evaporation of solvents present in the silane agent, resulting in increased bond strength of the composite resin to the fiber post.

Acid Etching, Dental↗

PubMed2005

Post-surface conditioning improves interfacial adhesion in post/core restorations.

OBJECTIVES: To verify the influence of different etching procedures of the post-surface on microtensile bond strength values between fiber posts and composite core materials. METHODS: 60 DT Light Posts were divided into 10 subgroups using five different chemical surface treatments and two composite materials to build-up the abutment. Chemical surface treatments including etching with potassium permanganate; treatment with 10% hydrogen peroxide; treatment with 21% sodium ethoxide; etching with potassium permanganate and 10 vol.% HCl; silanization (control group) were performed on the post's surface. The build-up was performed using (A) Core Paste XP (Dent Mat) and (B) Unifil Flow (GC). Two samples of each group were randomly selected to investigate the morphologic aspect of the post/core interface with a scanning electron microscope (SEM). The remaining specimens were cut so as to obtain microtensile sticks that were loaded in tension at a cross-head speed of 1mm/min until failure. The statistical analysis was performed using two-way ANOVA and the Tukey's test for post-hoc comparisons (alpha=0.05). RESULTS: SEM examination showed an interpenetrating adhesion network between the treated fiber post-surface and the composite material in all the groups tested. The results achieved with potassium permanganate had a significant influence on microtensile interfacial bond strength values with both the tested materials. Post-superficial treatments enhanced the bond strength particularly of Core Paste XP. SIGNIFICANCE: Etching procedures showed a similar effect on the post-surface and enhanced the adhesion of composite core build-ups as a result of micromechanical and chemical retention.

Composite Resins↗

PubMed2005

Evaluation of two Bis-GMA analogues as potential monomer diluents to improve the mechanical properties of light-cured composite resins.

OBJECTIVES: The aim of this study was to investigate the influence of new diluent agents, diluent ratio and filler content, on relevant mechanical properties of several novel composite resins containing Bis-GMA as resin matrices, and to compare these with the properties of composites based on TEGDMA, a conventionally used diluent. METHODS: Two Bis-GMA analogues were synthesized and 20 experimental composite resins were prepared combining three monomer mixtures (Bis-GMA/TEGDMA, Bis-GMA/CH3 Bis-GMA and Bis-GMA/CF3 Bis-GMA), at three dilution rates (85/15, 10/90, 0/100) and three levels of hybrid filler content (barium aluminosilicate glass): 0, 10 and 35%. Flexural strength (FS), modulus of elasticity (ME) and microhardness (VHN) of the composites were evaluated. Five specimens of each material were prepared for each mechanical test, light-cured over 120 s and stored in water at 37 degrees C for 1 week. Three-point bending test was used for FS measurement and VHN was quantified by using a Vickers microindentor. Data were analyzed by ANOVA and Student-Newman-Keuls tests (P<0.05). RESULTS: Materials with CH3 Bis-GMA showed an enhanced VHN. Mean FS was higher for matrices containing TEGDMA. Overall, dilution favored FS and VHN but not ME. Filler loading specially improved ME and VHN. SIGNIFICANCE: Results correlate with an increase in the extent of polymerization due to the higher flexibility of the less viscous comonomer starting system and the hydrophobic character of the Bis-GMA analogues.

Aluminum Silicates↗

PubMed2005

Longevity of bonds made by composite and polyacid-modified resins to dentin using a dual-cured adhesive system.

PURPOSE: To evaluate the microtensile bond strengths (MTBS) of a dual-cured dentin adhesive bonded to dentin using a light-cured resin-based composite (composite) or a polyacid-modified resin-based composite (compomer), and to investigate the effect of water aging on the bond strengths of these systems. METHODS: Flat dentin surfaces prepared from extracted human third molars were bonded with Prime&Bond NT Dual-Cured version (PBNT). Resin build-up crowns were constructed incrementally with two different materials: a composite (Z250) or a compomer (Dyract AP). When Dyract AP was used as the restorative material, half of the specimens were etched with 36% phosphoric acid, and the other half of the specimens were not etched. After storage in water for 24 hours or for 6 months, the teeth were sectioned to obtain bonded 1.3 mm2 beams containing the bonded interface. Each beam was tested in tension in an Instron machine at 0.5 mm/minute. Results were analyzed by multiple ANOVA and Student-Newman-Keuls multiple comparison tests. RESULTS: The group PBNT/Dyract AP bonded to acid-etched dentin showed the highest bond strength, in the 24-hour evaluation. Bond strength values decreased significantly after aging. The groups treated with PBNT in light-cured, dual-cured and self-cured modes performed equally well in the 24-hour evaluation. After 6 months of water aging, bond-strengths of the light-cured groups remained stable. By contrast, decreases in the bond strengths of the self-cured groups were observed.

Acid Etching, Dental↗

PubMed2004

Microhardness of acid-treated and resin infiltrated human dentine.

OBJECTIVE: The aim is to determine if superficial or deep dentine microhardness (MH) is affected by different chemical dentine pre-treatments performed for resin bonding. METHODS: Dentine discs of superficial (SD) and deep dentine (DD) were obtained by transversally sectioning the crowns of human third molars. Knoop MH was measured after different treatments: (1) polished up to 4000 grit, (2) polished and etched (37% ortophosphoric acid for 15 s), (3) resin (Single Bond -SB-) infiltrated dentine after acid etching, (4) polished, etched and treated with 5% NaOCl for 2 min, (5) resin infiltrated (SB) after etching and NaOCl treatment. For resin infiltrated surfaces care was taken in order to remove the excess adhesive layer, and obtain infiltrated dentine, by measuring thickness of the sample before resin infiltration and polishing after resin infiltration until obtaining the initial thickness of the sample. Indentations (n=20) were performed on moist surfaces with a standard Knoop MH tester (20 g, 5 s). Data were expressed in Knoop Hardness Numbers (KHN) and analysed by ANOVA and multiple comparisons (P<0.05). RESULTS: Dentine KHN decreased on both SD and DD after acid etching. NaOCl treatment after acid etching did not affect MH on SD, but KHN of DD was lowered. Resin infiltration increased KHN but did not recover the initial MH values in both SD and DD. CONCLUSIONS: Treating dentine with either H3PO4 or NaOCl caused marked reduction of its surface hardness and subsequent resin infiltration was not capable to restore it.

Acid Etching, Dental↗

PubMed2004

Tensile strength and microhardness of treated human dentin.

OBJECTIVES: To determine the ultimate tensile strength and Knoop hardness of mineralized, EDTA-treated, sodium hypochlorite (NaOCl)-treated, EDTA-treated resin-infiltrated, and NaOCl-treated resin-infiltrated dentin. METHODS: Dumbell-shaped specimens with a cross-sectional area of 0.5 mm2 were prepared from the crowns of extracted human third molars. Specimens were randomly assigned to the following experimental groups: (1) mineralized dentin; (2) 0.5 M EDTA-demineralized dentin, pH 7/5 days; (3) 5% NaOCl-deproteinized dentin/2 days; (4) EDTA-treated, Single Bond resin-infiltrated dentin; (5) NaOCl-treated, Single Bond resin-infiltrated dentin. All specimens were tested in tension in a Vitrodyne testing machine at 0.6 mm/min. Knoop microhardness was measured on the fractured edges of specimens in groups 1, 3, 4, and 5. Results were analyzed by ANOVA and SNK tests (p < 0.05). RESULTS: Both EDTA and NaOCl treatments caused significant reductions in the tensile strength and microhardness of mineralized dentin (p < 0.05) with the largest reductions observed after NaOCl treatment (p < 0.05) Resin infiltration of treated dentin resulted in moderate increase of its tensile strength and microhardness, however, the original mineralized values were not recovered (p < 0.05). SIGNIFICANCE: Whenever dentin surfaces are treated with EDTA or NaOCl prior to a clinical bonding procedure, clinicians must be aware that a weak layer may be present at the interface, which may lead to premature failures of resin/dentin bonds.

Analysis of Variance↗

PubMed2004

Effect of the hydration status of the smear layer on the wettability and bond strength of a self-etching primer to dentin.

PURPOSE: To evaluate the microtensile bond strength (MTBS) of a resin-based composite to smear layer-covered dentin using a self-etching primer, Clearfil SE Bond (CSEB), under two different hydration states. Surface roughness and wettability (contact angle measurements) of water and the CSEB primer were also evaluated on this substrate. METHODS: Contact angle (CA) measurements were performed on four caries-free extracted human third molars. The specimens were sectioned parallel to the occlusal surface to expose the moderately deep dentin and ground flat (180-grit SiC) under water to provide uniform flat surfaces. In two samples, the smear layer was completely air-dried; in the other two specimens, the smear layer was briefly air-dried. Contact angle measurements were performed to assess wettability of water and CSEB primer using the Axisymmetric Drop Shape Analysis technique. Surface roughness (SR) was determined with a contact profilometer. In another four molars, CSEB was applied to the smear layer-covered dentin with both hydration states. Resin build-ups were performed incrementally with Tetric Ceram. After storage for 24 hours in water at 37 degrees C, the teeth were sectioned to obtain bonded beams with an average cross-sectional area of 1.0 mm2. Each beam was tested in tension in an Instron machine at 0.5 mm/minute. Kolmogorov-Smirnov and Student t-tests were performed at a 95% significance level. RESULTS: Observed water contact angles were lower on the hydrated smear layer but no differences were found between contact angles on completely and briefly air-dried smear layer when the primer was used for CA measurements. SR was similar for both substrates and MTBS was greater when the adhesive was applied on the completely air-dried smear layer.

Acid Etching, Dental↗