Biomedical subjects

David H Pashley

Publications and source records attributed to David H Pashley.

At least 37 records · Page 2Linked to original sources

PubMed2006

Bondability of Resilon to a methacrylate-based root canal sealer.

Resilon broadens the dimensions of endodontic adhesion by introducing the possibility of creating monoblocs between root canal filling materials and intraradicular dentin by using methacrylate-based sealers. The adhesive strength of Resilon to RealSeal, a methacrylate-based root canal sealer, was evaluated using a modified microshear bond testing design. Flat Resilon surfaces with different roughness were created for bonding to the sealer and compared to a composite control. The composite control exhibited mean shear strength 7.3 to 26.9 times higher than those of the Resilon groups. Shear strength differences among the Resilon groups of different surface roughness highlighted the contribution of micromechanical versus chemical coupling in sealer retention. Ultrastructural evidence of phase separation of polymeric components in Resilon suggested that the amount of dimethacrylate incorporated into this filled, thermoplastic composite may not yet be optimized for effective chemical coupling to methacrylate-based sealers.

Dental Bonding↗

PubMed2006

Ultrastructure of smear layer-covered intraradicular dentin after irrigation with BioPure MTAD.

The structure of mechanically instrumented intraradicular dentin after irrigation with NaOCl as the initial rinse and BioPure MTAD as the final rinse were examined from the coronal, middle, and apical parts of root canal walls using transmission electron microscopy. Sterile distilled water and EDTA as final rinses were employed as the respective positive and negative controls under the same experimental conditions. There were 2 to 5 mum thick smear layers produced on mechanically instrumented root canal walls that were completely removed by EDTA and BioPure MTAD under agitation. Both irrigants created a zone of demineralized collagen matrices in eroded dentin and around the dentinal tubules, with the mildly acidic BioPure MTAD being more aggressive than EDTA. These demineralized dentin zones create the opportunity for dentin hybridization by infiltration of hydrophilic adhesives/sealers. However, the potential consequences of compaction of hydrophobic sealers against air-dried, collapsed collagen matrices, and hydrolytic degradation of incompletely infiltrated matrices remain unresolved.

Bicuspid↗

PubMed2006

Ultrastructure of intraradicular dentin after irrigation with BioPure MTAD. II. The consequence of obturation with an epoxy resin-based sealer.

In addition to an initial report on the creation of thick demineralized collagen matrices in root dentin that were irrigated with BioPure MTAD or EDTA as final rinses for 5 minutes, this study examined the effect of a 2-minute irrigation time of these final irrigants on the extent of demineralization of intact intraradicular dentin and on interfacial nanoleakage after obturation with AH Plus and gutta-percha using warm vertical compaction. Transmission electron microscopy confirmed that the reduction in irrigation time did not compromise the smear layer removing capacity of these two irrigants when 1.3% NaOCl was employed as the initial rinse. BioPure MTAD created 5 to 6 microm thick demineralized dentin matrices, while 17% EDTA produced 1 to 2 microm thick matrices that were suboptimally infiltrated by the epoxy resin-based sealer, as manifested by the occurrence of silver tracer deposits within the hybrid layers.

Chelating Agents↗

PubMed2006

Potential iatrogenic tetracycline staining of endodontically treated teeth via NaOCl/MTAD irrigation: a preliminary report.

This study reported red-purple staining of light-exposed, root-treated dentin when root canals were rinsed with 1.3% NaOCl as initial rinse followed by the use of BioPure MTAD as final rinse. This intrinsic dentin staining occurred irrespective of whether the root canals were filled, and could be observed even in crown dentin when the latter was sequentially immersed in NaOCl and MTAD. Bench-top reproductions of the phenomenon revealed that the exothermic reaction is not an acid-base reaction. Conversely, the reaction is of a redox nature that highly resembled the previously reported mechanism of tetracycline staining, in which photo-oxidation of tetracycline resulted in a red-purple tetracycline degradation product that has a high affinity for hydroxyapatite. This photo-oxidative degradation process is probably triggered by the use of NaOCl as an oxidizing agent, and may be prevented by rinsing the NaOCl-treated dentin with ascorbic acid, a reducing agent, before the application of MTAD.

Antioxidants↗

PubMed2006

Activation of gelatinolytic/collagenolytic activity in dentin by self-etching adhesives.

Mild acids are known to activate dentin matrix metalloproteinase (MMPs). All self-etching dental adhesives are acidic (pH 1.5-2.7) and may activate dentin MMPs. The purpose of this study was to compare the ability of several all-in-one adhesives to activate gelatinolytic and collagenolytic activities in powdered mineralized dentin. Powdered dentin made from human teeth was mixed with all-in-one adhesives (Clearfil Tri-S Bond, G-Bond, Adper Prompt L-Pop) or a self-etching primer (Clearfil SE Bond primer) for varying times and then the reaction was stopped by extracting the adhesives using acetone. Fresh untreated mineralized dentin powder had a gelatinolytic activity of 3.31 +/- 0.39 relative fluorescent units (RFU) per mg dry weight (24 h) that increased, over storage time, to 87.5 RFU mg(-1) (24 h) after 6-8 wk. When fresh powder was treated with acidic Tri-S Bond, the gelatinolytic activity increased from 3.24 +/- 0.70 RFU mg(-1) to > 112.5 RFU mg(-1) (24 h) after 20 min and then remained unchanged. Monomers with lower pH values produced less activity. There was a significant, direct correlation between gelatinolytic activity and pH, with Tri-S giving the highest activity. Coating dentin powder with Tri-S resin prevented fluorescent substrates from gaining access to the enzyme, even though it activated the enzyme. In conclusion, self-etch adhesives may activate latent MMP and increase the activity to near-maximum levels and contribute to the degradation of resin-dentin bonds over time.

Adhesives↗

PubMed2006

Design of new phosphonic acid monomers for dental adhesives--synthesis of (meth) acryloxyalkyl 3-phosphonopropionates and evaluation of their adhesion-promoting functions.

The aims of this study were to synthesize new phosphonic acid monomers, and to examine their bonding performance. Four kinds of newly designed phosphonic acid monomers were synthesized, and seven experimental composite-type adhesive resins comprising the synthesized monomers (3 wt%), with BPO/DEPT/BPBA initiator were prepared. Tensile bond strengths of the adhesive resins to enamel and metal were measured with a universal testing machine at a crosshead speed of 1.0 mm/ min. The synthesized adhesive monomers were light yellow viscous liquids with 32.5%-49.3% yields, and identified by 1H NMR, IR and elemental analysis to be (meth)acryloxyalkyl 3-phosphonopropionates [R-P(=O) (OH)2] (5-MPPP, 6-MHPP, 6-AHPP, 10-MDPP). It was found that the newly developed phosphonic acid monomers with BPO/DEPT/BPBA initiator attained strong adhesion to both unetched, ground enamel and sandblasted Ni-Cr alloy with good durability. They exhibited significantly higher bond strengths than conventional phosphorous-containing monomers such as MEPP and VBPA (p <0.01). These findings indicate that the experimental phosphonic acid monomer-containing adhesive resins have potential prosthodontic and orthodontic applications, especially as self-etching, non-rinsing orthodontic adhesive resins.

Adhesives↗

PubMed2006

pKa value and buffering capacity of acidic monomers commonly used in self-etching primers.

PURPOSE: The aim of this investigation was to characterize acidic monomers used in self-etching primers/adhesives by determination of their pKa values and by calculation of their calcium dissolving capacity in comparison with phosphoric and hydrochloric acid. MATERIALS AND METHODS: The following acidic monomers were included in this study: 4-methacryloyloxyethyl trimellitate anhydride (4-META), 10-methacryloyloxydecyl dihydrogen phosphate (MDP), dimethacryloyloxyethyl hydrogen phosphate (di-HEMA-phosphate), ethyl 2-[4-(dihydroxyphosphoryl)-2-oxabutyl]acrylate (EAEPA), 2-[4-(dihydroxyphosphoryl)-2-ox-abutyl]acrylic acid (HAEPA), and 2,4,6 trimethylphenyl 2-[4-(dihydroxyphosphoryl)-2-oxabutyl]acrylate (MAEPA). The pKa values were obtained by titration with 0.1 mol/l NaOH in aqueous solution. The inflection points of the resulting potentiometric titration curve were determined as pKa values. In the case of the sparingly water-soluble acidic monomers MAEPA and 4-META, the co-solvent method using different water/ethanol ratios for MAEPA or water/acetone ratios for 4-META was used. The dissolving capacity of each acidic monomer is defined as the amount of hydroxyapatite (HA) dissolved by 1 g of acid. For each monomer, the HA dissolving capacity was calculated bythe corresponding pKa value and the molecular weight. To confirm the calculated dissolving capacities, increasing amounts of HA powder (100 mg portions) were slowly added to 15 mmol/l aqueous solutions of the monomers to determine how much HA could be dissolved in the acidic solutions. RESULTS: For all the investigated acidic monomers, pKal values between 1.7 to 2.5 were observed. The pKa2 values for the phosphate/phosphonate derivatives are between 7.0 and 7.3, and are comparable to phosphoric acid. For dicarboxylic acid derivatives, the pKa2 values are in the range of 4.2 to 4.5. Due to their comparable molecular weights and pKal values, the three tested acids di-HEMA phosphate, MDP and 4-META all possess comparable dissolving capacities for HA (ie, 0.26 to 0.28 g/g monomer). The same amount by weight of acidic monomer EAEPA dissolved more HA (ie, 0.35 g/g monomer). Due to their different molecular weights, phosphoric acid and hydrochloric acid dissolved three and ten times as much HA, respectively, as the first three acidic monomers. As a result, the ability of these acids to dissolve HA increases as their molecular weight decreases. CONCLUSION: There are no significant differences among the investigated acidic monomers in terms of their pKa values and HA dissolving capacities. Monomer selection criteria for new self-etching adhesives must include properties such as calcium salt stability, wetting of the substrate, and copolymerization behavior.

Acetone↗

PubMed2006

Effects of exogenous collagenase and cholesterol esterase on the durability of the resin-dentin bond.

PURPOSE: The purpose of this work was to determine microtensile dentin bond strengths (microTBS) of dentin-resin composite bonds after three-month storage in artificial saliva containing either collagenase (COL) or cholesterol esterase (EST). The null hypothesis tested is that the resin-dentin bond strength is equivalent for each storage medium at the tested storage times. MATERIALS AND METHODS: Resin composite was bonded to occlusal dentin, and microTBS specimens were formed and stored in the artificial saliva, COL, EST, or synthetic oil. After 24 h and 12-week storage, microTBS was determined and failure modes were characterized by SEM. The interfacial ultrastructure was evaluated by transmission electron microscopy as unstained and stained sections (phosphotungstic acid/uranyl acetate). Statistical analysis was performed by ANOVA and Weibull survival analyses at the 0.05 level of statistical significance. RESULTS: There were significantly weaker bond strengths after 12 weeks for all experimental storage media (p < 0.001). Artificial saliva containing EST lowered bond strengths to a significantly greater extent than did COL after 12 weeks of storage, while no difference between these groups could be discerned after 24 h. Therefore, the null hypothesis of this experiment is rejected. CONCLUSION: Exogenous enzymatic challenge to resin-dentin bonds decreased bond durability only with EST. However, when further challenges to ideal infiltration of the comonomers into the hybrid layer were carried out using inadequate removal of solvent, additional alterations in hybrid layer ultrastructure were discerned by TEM that may represent different potential degradative processes. The contribution of endogenous enzymatic challenges to the primary degradative process, ie, hydrolysis, is unknown and deserves continued attention.

Acid Etching, Dental↗

PubMed2006

A new technique for assessing hybrid layer interfacial micromorphology and integrity: two-photon laser microscopy.

PURPOSE: This study describes a two-photon laser fluorescence microscopy technique developed to evaluate the interfacial micromorphology of the hybrid layer in bonded restorations. MATERIALS AND METHODS: Micropermeability of the hybrid layer was characterized by means of simultaneously contrasting a dye-containing adhesive with a differently colored dye placed into the pulp chamber and allowed to diffuse toward the different-colored hybrid layer. A fluorescent red dye (rhodamine B) was incorporated into a commercial dentin bonding agent. Class I preparations (margins in enamel) were made on extracted human third molars. The teeth were restored using conventional methods: bonding agent, composite, finishing, and polishing. An aqueous solution of a yellow/green dye (fluorescein) was then placed into the pulp chamber for 3 h, allowing time to diffuse toward the different-colored bonded interface. The teeth were then embedded, sectioned, and microscopically analyzed using two-photon laser microscopy at 40X magnification. RESULTS: Subsurface fluorescent imaging using this technique enabled interfacial micromorphology to be characterized at submicrometer resolution and provided high-contrast images. The quality of surrounding structures and potential presence of gaps were also precisely assessed. CONCLUSION: Two-photon laser microscopy provided high quality, high-resolution images of the bonded interface and surrounding areas, allowing accurate qualitative and quantitative analysis of the structure and integrity of the hybrid layer.

Bisphenol A-Glycidyl Methacrylate↗

PubMed2006

Factors affecting use of fluorescent agents in identification of resin-based polymers.

PURPOSE: The present study is a compilation of methodologies developed in order to evaluate the effects of addition of a fluorescent agent, rhodamine B, to resin-based materials. The intent of the work was to develop a systematic methodology that accounts for variables not shown to be of concern in past testing, but may significantly affect interpretation of the resulting images and material properties. MATERIALS AND METHODS: Different methodologies were specifically developed to evaluate factors affecting the use of the fluorescent agent rhodamine B in the identification of resin-based materials. The influence of dye concentration was evaluated with respect to adhesive polymerization reaction kinetics and bond strength of the resin into which the dye is added. The pH of the dye-solvent solution was also considered. Additionally, the mass and percentage of rhodamine B leached into different media over time was determined. RESULTS: It was demonstrated that a specific dye must be used with caution, and the concentration of a fluorescent agent is important with respect to both the conversion and bond strength of the resin to which the dye is added. An alcohol-based dye solution also produced an extremely high amount of dye leaching from polymerized specimens. The adhesive pH was not altered. CONCLUSION: The standardized methodology developed here to analyze restoration interfaces using a fluorescent dye can lessen the impact of variables when interpreting results.

Composite Resins↗

PubMed2006

Bond strength of resin-based restorations polymerized with different light-curing sources.

PURPOSE: To evaluate the influence of different light-curing units on microtensile bond strength of resin composite restorations. MATERIALS AND METHODS: Standardized Class I preparations (6.0 x 4.5 mm, 2.5 mm deep) were made in extracted human third molars after abrading the cusps. Resin was inserted in bulk using a 3M ESPE restorative system [Adper Single Bond (DBA)/ Filtek Z250 (RC)]. Both materials were polymerized using different light-curing units: QTH at 540 mW/cm(2) (XL 3000, 3M ESPE); LED at 750 mW/cm(2) (Elipar FreeLight2, 3M ESPE); PAC at 2130 mW/cm(2) (Arc Light II, Air Techniques). Nine different light combinations were developed to polymerize both DBA and RC: QTH/QTH; QTH/LED; QTH/PAC; LED/LED; LED/QTH; LED/PAC; PAC/PAC; PAC/QTH; PAC/LED. Restored teeth were stored in distilled water for 24 h at 37 degrees C and then sectioned, yielding stick-shaped specimens with a bonded area of approximately 0.9 mm(2). Specimens were assessed in a testing machine at a crosshead speed of 1 mm/min. The results were analyzed using two-way ANOVA and Tukey's test at a pre-set alpha = 0.05. RESULTS: The combinations PAC/QTH and QTH/QTH presented the highest bond strength values, and LED/QTH the lowest (p < 0.05). Significantly lower values were observed in combinations when the LED light was used to polymerize DBA compared to QTH and PAC lights, irrespective of the light source used to polymerize RC (p < 0.05). Same light combinations presented similar bond strength values. CONCLUSIONS: Different light sources influence restoration bond strength. Bond strength is more dependent on the light source used for DBA than for curing RC.

Bisphenol A-Glycidyl Methacrylate↗

PubMed2005

The effects of common errors on sealing ability of total-etch adhesives.

OBJECTIVES: This study evaluated the effect of errors commonly made in using total-etch adhesives, on the resulting bond strength, fluid movement and nanoleakage of resin dentin bonds. METHODS: Two total-etch adhesives were used for bonding to dentin according to the manufacturers' recommendations, with meticulous solvent evaporation (control), or with the introduction of common bonding errors-wet bonding without solvent evaporation (no evaporation), and dry bonding. RESULTS: The 24-hour bond strength of the control was significantly higher than the other groups (p <0.05). For all groups, the higher initial permeability declined significantly after 24 h. The fluid movement across bonded dentin was similar in the control and dry bonding for both adhesives, whereas significantly higher permeability (p<0.05) was recorded for the no evaporation groups even after 24 h. Extensive silver impregnation within hybrid layers was seen by TEM in the no evaporation and dry bonding specimens after 24 h. Dry bonding caused collapse of the collagen matrix and interfered with resin infiltration. In contrast, inadequate solvent evaporation and/or residual water during dentin bonding results in dilution or incomplete polymerization of the resin, leading to severe nanoleakage formation. SIGNIFICANCE: Increased permeability associated with incomplete solvent evaporation in total-etch adhesives may lead to poor bond strength.

Acid Etching, Dental↗

PubMed2005

Effect of resin hydrophilicity and temperature on water sorption of dental adhesive resins.

This study examined the effects of copolymer hydrophilicity and temperature on water sorption and solubility characteristics of five copolymer blends of increasing degree of hydrophilicity using gravimetric measurements. Six resin disks (15 mm in diameter x 1 mm in thickness) were prepared from each copolymer blend and were stored in deionised water at 23, 37 and 55 degrees C. Water sorption and solubility of the resin disks were measured before and after water immersion and desiccation. Multiple regression analysis of water sorption was performed on two independent variables, copolymer hydrophilicity and temperature. Maximum water sorption increased significantly with Hoy's total cohesive energy density (delta(t)), Hoy's solubility parameter for polar forces (delta(p)) and hydrogen bonding (delta(h)), but was not influenced by temperature. However, a significant positive relationship was observed between diffusion coefficients (obtained using Fick's law of diffusion) and temperature. The water absorption activation energy was 10 kJ/mol for the most hydrophilic copolymer blend R5 and 35-51 kJ/mol for copolymer blends R1-R4. The positive relationship between maximum water uptake and copolymer hydrophilicity suggests that water molecules diffuse through the polymer matrices by binding successively to the polar sites via hydrogen bonding. Such water sorption may determine the durability of resin-dentine bonds.

Adhesives↗

PubMed2005

Efficacy of composite surface sealers in sealing cavosurface marginal gaps.

OBJECTIVES: The ability of commercially available composite surface sealers to penetrate and seal a controlled gap formed in all-enamel margin, Class V in vitro resin composite restorations in human bicuspids was examined. METHODS: A fluorescent red dye (Rhodamine B) was incorporated to a variety of commercially available composite surface sealers. The teeth were restored using acid etching, a dentin bonding agent, and a photo-activated microfilled composite, finished, polished, and sealed. The teeth were thermocycled and then immersed in an aqueous solution of a green fluorescent dye (Dextran-Fluorescein) to evaluate the sealing ability and penetration of surface sealers into the controlled gaps formed at unbonded margins. Teeth were embedded, sectioned, and images recorded using confocal microscopy. RESULTS: All sealers leaked, and use of a dentin-bonding agent to seal the gap performed better than the commercial sealing products. CONCLUSIONS: Commercial surface sealers evaluated were not able to totally seal controlled-size cavosurface gaps, and sealer penetration into the controlled gap varied greatly. Composite restorative procedures should be performed to obtain ideal marginal sealing, minimizing the need for composite surface sealers, which were found to not totally seal an exposed cavosurface margin. Use of a dentin-bonding agent may provide better sealing than commercial products developed specifically for this purpose.

Analysis of Variance↗

PubMed2005

Single-bottle adhesives behave as permeable membranes after polymerisation. II. Differential permeability reduction with an oxalate desensitiser.

OBJECTIVES: This study examined the changes in hydraulic conductance and ultrastructure of dentine bonded with simplified etch-and-rinse adhesives to oxalate desensitiser pre-treated acid-etched dentine. METHODS: Human dentine disks were acid-etched, treated with an oxalate desensitiser (BisBlock, Bisco), and bonded with One-Step (OS), Single Bond (SB), OptiBond Solo Plus (OB) or Prime and Bond NT (PB). Similar disks from each group were acid-etched, and bonded without oxalate pre-treatment. Hydraulic conductance of the specimens was measured at 20 cm of water pressure and analysed with nonparametric statistical methods. Epoxy resin replicas of the smear layer-covered dentine and bonded dentine were examined with SEM for the extent of fluid transudation. Specimens bonded under perfusion were examined with TEM after tracer immersion. RESULTS: OB and PB exhibited a highly significant reversal of the reduced hydraulic conductance obtained with BisBlock on unbonded acid-etched dentine. Profuse water transudation across the bonded dentine was observed from the replicas. Adhesive interfaces were covered with spherical globules that interfered with dentine hybridization. Conversely, no significant difference in hydraulic conductance was observed in SB, between Bisblock pre-treated, unbonded and bonded acid-etched dentine. Significantly lower hydraulic conductance was shown on application of OS to Bisblock-treated acid-etched dentine. Water transudation was sparse, interfering surface globular structures were absent, and only angular subsurface crystals were seen in the dentinal tubules. CONCLUSIONS: Convective water fluxes through dentine may be reduced by applying Bisblock to acid-etched dentine before bonding with One-Step or Single Bond. However, reducing adhesive permeability with the use of oxalate desensitiser is not applicable to low acidity adhesives such as OptiBond Solo Plus and Prime and Bond NT.

Adhesives↗

PubMed2005

Permeability of marginal hybrid layers in composite restorations.

The goal of adhesive dentistry is to restore the peripheral seal of dentin lost from removal of enamel. Unfortunately, the hybrid layer (HL) that is used to create that seal is permeable to small ions or molecules, even in the absence of detectable, interfacial gap formation via nanoleakage. This nanoleakage results from several mechanisms including incomplete infiltration of adhesive monomers into demineralized collagen matrix, presence of hydrophilic monomers, and insufficient removal of solvent or water that remains trapped inside the HL. These mechanisms lead to a porous interface with nanometer-sized channels that increase the permeability of the HL. The null hypothesis tested in this study was that water and acidic solution storage are able to alter in vitro the resin-dentin interface, further increasing the marginal hybrid layer (MHL) permeability. Class II cavities were made in vitro. The specimens were stored in water for 1 week and in lactic acid solution for 3 days. Polyvinyl siloxane impressions of restoration margins were taken before and after storage in water and lactic acid solution. Polyether replicas were obtained using the silicon impressions as molds. Replicas and original samples were observed under scanning electron microscopy. Lines of water droplets were detected on MHLs and overlying adhesive only after storage. Replicas obtained after acidic solution storage showed great numbers of irregularities such as gaps, voids, and degradation of the dentin-restoration surface margin, but also a great number of droplets. Dentin-restoration resin interfaces absorb water and are damaged by storage in dilute lactic acid. The presence of water droplets probably indicates water that flows out of the interface during the setting time of the impression and thus represents an index of marginal HL water permeability.

Acrylic Resins↗

PubMed2005

Water content and apparent stiffness of non-caries versus caries-affected human dentin.

Caries-affected dentin contains less mineral and more water than surrounding normal dentin. Such dentin should be less stiff and should shrink more than normal dentin when dried. The purpose of this study was to test the relationships between the stiffness, shrinkage, and water content of caries-affected versus normal dentin. Extracted human carious third molars were stained with caries-detector dye and the occlusal surfaces ground down until only caries-affected dentin remained, surrounded by normal dentin. Dentin disks were prepared from these crowns placed in a aluminum well positioned under a modified thermal mechanical analyzer. Changes in specimen height and stiffness were measured following drying or static loading in both caries-affected and surrounding normal dentin. Core samples of these two types of dentin were used to gravimetrically measure water content. Two-way ANOVA and regression analysis was used to test the relationship between shrinkage versus water content, stiffness versus water content, and stiffness versus shrinkage. Caries-affected dentin was found to be less stiff and contained more water than normal dentin (p < 0.05). Regression analysis revealed highly significant inverse relationships between stiffness and water content, and stiffness and shrinkage (p < 0.0005).

Dental Caries↗

PubMed2005

Nanoleakage within the hybrid layer: a correlative FEISEM/TEM investigation.

The aim of this study was to compare the nanoleakage patterns of the resin-dentin interfaces of three dentin bonding systems at both TEM and field emission in lens SEM (FEI-SEM) levels. A standardized smear layer was created with 180-grit silicon carbide paper (SiC) on dentin disks obtained from 18 noncarious human third molars. Specimens were randomly divided into three groups and bonded with a two-step total etching adhesive (Single Bond, SB), a two-step, self-etching adhesive (Clearfil SE BOND, SEB), and a one-step, self-etching adhesive (XENO III, XEIII). Nanoleakage was evaluated by using an ammoniacal silver-nitrate solution. Specimens were processed for TEM and FEI-SEM observation. The TEM of SB revealed silver deposits in adhesive and hybrid layers (HL). High-magnification FEI-SEM micrographs clearly identified these deposits as spherical clusters mainly associated with nonembedded collagen fibrils. TEM and FEI-SEM examination of SEB revealed some clusters of silver deposits within porosities and small channels of the HL. Additional silver deposits were observed between the peritubular dentin walls and the resin tags. XEIII revealed very fine and diffuse silver grains throughout the entire HL. SEM visualization of nanoleakage at a high level of resolution has not been previously described. FEI-SEM technology supported the TEM visualization with three-dimensional morphological data of the relations between the HL constituents and nanoleakage. The results of the present study confirm the hypothesis that both total- and self-etch adhesives are not able to fully infiltrate the dentin substrate.

Acid Etching, Dental↗