Thickness Of Hybrid Layer Research Articles

Effects of dentin dry/moist condition on the immediate adhesive performance of different solvent-based etch-and-rinse adhesivesystems

PurposeThe purpose of this research was to analyze and measure, under optical microscopy, the hybrid layer thickness and resin tags length, as well as the microtensile bond strength of two conventional adhesive systems when applied to dry and moist dentinal substrate. MethodsThirty-two extracted human molars were randomly distributed into four groups according to the adhesive systems (XP Bond and Prime&Bond 2.1) and moisture condition (dry and moist). In Groups I and II, XP adhesive system was applied on dry and moist dentin, respectively; while Groups III and IV received PB adhesive system, in the same way as was done in Groups I and II, respectively. After adhesive and restorative procedures, all specimens were sectioned along their long axes; one hemi-tooth sample was subjected to the microtensile bond strength test while the other was decalcified and serially sectioned into six micron thick slices and sequentially mounted on glass slides. These sections were stained by the Brown and Brenn method for posterior analysis and measurement of the hybrid layer and resin tags under a light microscope with a micrometric ocular 40/075. ResultsData were analyzed using two-way ANOVA and Tukey’s test (α=0.05). For the variable “hybrid layer thickness”, XP showed no significant differences between dry and moist dentin (5.2μm and 5.5μm, respectively), but for PB, hybrid layer was significantly thicker for moist (4.0μm) than for dry dentin (3.0μm). For the variable “resin tags length” XP showed 17.9μm length for dry dentin and 20.8μm for moist dentin; PB 11.7μm for dry and 12.69μm for moist dentin;there was no significant differences between them, independent of the moisture condition. For the variable “microtensile bond strength”, XP showed 38.0MPa for dry dentin and 44.5MPa for moist dentin; and PB showed 22.7MPa for dry dentin and 20.8MPa for dry dentin no significant difference was observed between moist and dry dentin for XP (p=0.2) and PB (p=0.7), but XP was presented significantly higher bond strength values than PB in both moisture conditions (p=0.003 for dry and p=0.002 for moist). ConclusionThe two-step butanol-based etch-and-rinse adhesive XP Bond presented a superior behavior with regard to the hybrid layer thickness, length of resin tags and bond strength to dry and moist dentin substrates when compared with two-step acetone-based adhesive system Prime&Bond2.1.

Influence of Smear Layer on Depth of Demineralization and Thickness of Hybrid Layer

In order to evaluate the thickness of the hybrid layer and depth of demineralization of dentin surfaces submitted to different treatments, dentin slices from human teeth were divided into two groups: one polished with 60-grit SiC paper and the other with 600-grit SiC paper. The adhesive systems applied were: Adhe SE®, Clearfil SE™ Bond, G Bond™ and Adper Single Bond™. After treatment, the samples were fractured and prepared and the smear layer, the effect of conditioners, and thickness of the hybrid layer were analyzed by SEM. The adhesive system and smear layer influenced thickness of the hybrid layer. The conditioners were more efficient over thin smear layer. A direct correlation was demonstrated between depth of demineralization and thickness of the hybrid layer. The smear layer was able to influence the depth of demineralization and thickness of the hybrid layer; however, for the total-etching adhesive system, thickness of the hybrid layer was independent of the smear layer.

Ultrathin cellulose film coating of porous alumina membranes for adsorption of superoxide dismutase.

The non-toxic and biocompatible cellulose possesses nonspecific binding properties for many protein molecules. But its abundant inter- and intra-molecular hydrogen bonds induce spontaneous self-assembly of cellulose into a random fibrous morphology and cellulose film coating is usually just available for two-dimensional flat substrates, which severely limits its protein adsorption performance. In this study, direct self-assembly of an ultrathin cellulose film on hybrid polyelectrolyte multilayer pre-coated pore surfaces of an anodic aluminum oxide membrane was achieved through the dissolution and precipitation of cellulose from N-methylmorpholine oxide solution. Each pore channel surface pre-coated with a uniform polyelectrolyte hybrid layer (thickness ∼5.0 nm) was covered by a cellulose film (∼15.0 nm) consisting of dense cellulose nanoparticles with a diameter of 5.5 ± 1.4 nm. The three-dimensional porous structure of the aluminum oxide membrane was well-preserved and micrometre-long flexible nanotubes with an average outer diameter of ∼200 nm were obtained after further aluminum oxide template dissolution treatment in an acidic environment. Moreover, the cellulose film coated pore channel surfaces presented sufficient hydrogen bonds and exhibited a high adsorption capacity rate of ∼1.45 mg m-2 for superoxide dismutase. This facile cellulose deposition approach enabled ultrathin cellulose film coating on three-dimensional structured substrates for enhanced adsorption performance for protein molecules.

Nanoleakage in primary teeth prepared by laser irradiation or bur

The aim of this in vitro study was to analyze hybrid layer and nanoleakage of composite resin restorations in cavities prepared by either Er,Cr:YSGG laser or bur, followed by acid etching in primary teeth. Ten extracted primary molar teeth were randomly allocated into two groups consisting of ten cavities according to surface treatment regimen: Er,Cr:YSGG laser + acid etching(group 1) and bur + acid etching(group 2). Restorations of all samples were completed. Then, teeth were sectioned and immersed to ammoniacal silver nitrate solution. After polishing, hybrid layer thicknesses were examined under scanning electron microscopy (SEM) and ion analysis was carried out with SEM/energy dispersive X-ray spectroscopy preparation in terms of nanoleakage. Hybrid layer thickness and the amount of silver ions were assessed for the acid-etched groups. The collected data were analyzed with independent sample t test and Spearman's rank correlation. In groups 1 and 2, the mean hybrid layer thicknesses were 4.25 ± 1.41 and 5.24 ± 1.07μm and the silver ion percentages were 10.97 ± 13.81 and 22.79 ± 21.62%, respectively. Although no significant correlation was observed between the increase of hybrid layer thickness and the amount of silver ions, more silver ions were observed in group 2 (p < 0.05). According to the results of this study, acid-etched cavities prepared with laser promoted better results when compared to the acid-etched cavities prepared with bur.

Influence of Different Solvents on the Morphology of the Hybrid Layer Using Two-Step Etch-and-Rinse Adhesives

To evaluate if different etch-and-rinse adhesive solvents influenced the hybrid layer's morphology. Four one-bottle etch-and-rinse adhesive systems containing different solvents—Group A: Scotchbond 1XT™– 3 M ESPE, Group B: XP – Bond™ – Dentsply, Group C: Prime&Bond NT® – Dentply, and Group D: One Coat Bond® - Coltène Whaledent—were applied onto 32 dentin discs which were thermocycled, prepared, and examined using field-emission scanning electron microscopy. Micrographs were scanned and the data were processed using Statistical Package for Social Sciences. The mean value and standard deviation were calculated and the Anova Multivariant Test was used. The hybrid layer thickness average found was 3.23 µm (±0.53) in Group A, 3.13 µm (±0.73) in Group B, 2.53 µm (±0.50) in Group C, and 1.84 µm (±0.27) in Group D. Prime&Bond NT® presented a more inconsistent hybrid layer. The solvent seems to play a significant role in hybrid layer structure and thickness.

Hybrid Layer Width after Conventional Diamond, Carbide and Ultra-Sound CVD Burs

The aim of the present study was to evaluate hybrid layer thickness of primary molars sectioned with diamond, carbide and ultrasonic CVD burs. The occlusal enamel surfaces often molars were removed and superficial dentin was exposed. Three standardized cavities were prepared at mesial, central and distal exposed dentin with diamond, carbide and ultrasonic CVD burs, respectively. A self-etching adhesive system (Adhese, Ivoclar/Vivadent) was applied to prepared cavities and composite resin Z100 (3M/ESPE) was inserted according to manufacturers'instructions to hybridized dentin. Samples were light-cured and the crown was sectioned mesio-distally dividing the restored cavities in two halves which were observed under scanning electron microscopy (SEM), in order to quantitatively evaluate hybrid layer thickness (microm). Three repeated measures were performed at mesial, central and distal sites and mean values obtained were submitted to one-way analysis of variance (ANOVA). Data (mean +/- sd) obtained were (microm): 2.69 (0.44), 3.38 (1.23) and 2.72 (1.18)for diamond, carbide and CVD burs, respectively. No differences were observed among groups (p > 0.05). The adhesive systems promoted mechanical retention, uniform and continuous hybrid layer and resin tags formation at all dentin sites for all instruments tested. The results suggest that the minimally invasive cavities prepared with diamond, carbide and CVD for ultrasound, promoted hybrid layer formation with a similar thickness regardless the bur used.

HYBRID LAYER THICKNESS IN PRIMARY AND PERMANENT TEETH – A COMPARISON BETWEEN TOTAL ETCH ADHESIVES

SUMMARY Purpose: The aim this study is to compare the hybrid layer thickness and its micromorphological characteristics in samples from primary and permanent teeth following application of total etch adhesives. Materials and methods: On intact specimens of 20 primary and 10 permanent teeth was created flat dentin surfaces. The patterns were divided in 6 groups. Two different total etch adhesive systems were used – one tree steps (OptiBond, Kerr) and one two steps (Exite, VivaDent). In groups 3, 4, 5 and 6 recommended etching time was used - 15 s, in groups 1 and 2 the etching time was reduced to 7 s. After applying the adhesive, resin composite build-ups were constructed. Thus restored samples are stored in saline solution for 24 hours at temperature 37°C. Then they are subjected to thermal stress in temperature between 5°C to 55°C for 1,500 cycles and to masticatory stress – 150,000 cycles with force 100 N in intervals of 0.4 s. After that the teeth are cut through the middle in medio-distal direction with a diamond disc. SEM observation was done to investigate the thickness of the hybrid layer and the presence of microgaps. Statistical analysis was performed with ANOVA and Tukey's tests. Results: SEM observation showed significant differences of the hybrid layer thickness between primary and permanent teeth under equal conditions and after different etching time. Group 6 presented the highest average thickness 8.85 i and group 1 the lowest average in hybrid layer 3.74 i. Conclusion: In primary teeth the hybrid layer thickness increases with the increased etching time. The hybrid layer thickness in primary teeth is greater than that of the hybrid layer in permanent teeth under equal conditions. For primary teeth it is more appropriate to reduce the etching time to 7s to obtain a hybrid layer with better quality.

Layered manganese 4-phosphonoisophthalates (4-piH4) embedding Mn-O chains with metamagnetism in Mn3(4-piH)2(H2O)3·H2O

Two manganese phosphonates Mn3(4-piH)2(H2O)3·H2O (1) and Mn5(4-piH)2(4-piH2)2(phen)2(H2O)4 (2) (4-piH4 = 4-phosphonoisophthalic acid, phen = 1,10-phenanthroline) have been synthesized under hydrothermal conditions in the presence of organic co-ligand. Both compounds exhibit layer structures but with different topologies. In compound 1, a complicated “ladder-like” chain of {Mn3O3}O2 which contains three- and six-member rings made up of triangular shaped {Mn3O3} trimers is found. The chains are linked by the PO3C groups to form an inorganic layer. The phenyl and protonated carboxylate groups are pendent between the layers with extensive hydrogen bonds. In compound 2, tetramers of {Mn4O6} are connected by the {MnO6} octahedra through corner-sharing to form an infinite chain, which is further bridged by 4-piH3− ligands into a thick hybrid layer. Magnetic measurements reveal that antiferromagnetic interactions are dominant in both compounds. Metamagnetism is observed in compound 1 at low temperature, while no long range ordering is found in compound 2 down to 1.8 K.

Bond strengths, degree of conversion of the cement and molecular structure of the adhesive–dentine joint in fibre post restorations

ObjectivesBecause fibre post restorations are influenced by multiple factors such as the types of bonding materials, the dentine region and the time under moist exposure, this study sought to determine the bond strength of endodontic restorations and its relation to the degree of conversion of the cement layer and the molecular structure of the dentine-bonded joints. MethodsThe performance of 2 etch-and-rinse (All-Bond 2 and One-Step Plus) and 2 self-etch (Clearfil SE Bond and Xeno III) adhesives at post spaces regions, after 7d or 4m, was evaluated. FRC Postec Plus posts were cemented to the root canal with a dual-cure resin cement (Duo-Link). Transverse sections of the tooth were subjected to push-out testing, to degree-of-conversion measurements and to hybrid layer evaluation through μ-Raman spectroscopy. ResultsCoronal bonding was higher than cervical and middle bonding. The hybrid layer was thicker for the etch-and-rinse systems, with thicknesses decreasing towards the middle region. The degree of conversion measured for the 3-step etch-and-rinse group after 4m was significantly higher than that for the self-etching groups. ConclusionsAlthough not totally stable at the adhesive–dentine interface, the 3-step etch-and-rinse adhesive in the coronal dentine provided the best bond strength, degree of conversion of the cement and hybrid layer thickness in post restorations, in both short- and long-term analyses.

Morphological evaluation of new total etching and self etching adhesive system interfaces with dentin

Aim:The purpose of this study is to evaluate the resin-dentin interface, quality of the hybrid layer of total-etching and self-etching adhesive systems under scanning electron microscopy (SEM).Materials and Methods:Class V cavities were prepared in 40 extracted human molars. In Group I XP bond (Dentsply), in Group II Adper Single Bond II (3M ESPE), in Group III Adper Easy One (3M ESPE), and in Group IV Xeno V (Dentsply) were applied. Teeth were restored with resin composite, subjected to thermocycling, and sectioned in Buccolingual plane. The samples were demineralized using 6N HCl, for 30 sec, and deproteinized with 2.5% NaOCl for 10 min, gold sputtered, and viewed using a scanning electron microscope.Results:Among the total-etch systems used, the XP Bond showed a clear, thick hybrid layer, with long resin tags and few voids. Among the self-etch adhesive systems, the Xeno V did not show a clearly recognizable hybrid layer, but there were no voids and continuous adaptation was seen with the dentin.Conclusion:The adaptation of self-etch adhesives to the resin-dentin interface was good without voids or separation of phases; showing a thin, continuous hybrid layer.

Morphological confocal laser scanning microscope evaluation of four different “etch and rinse^|^quot; adhesives in post endodontic restoration

The aim of this study was to perform a morphometric evaluation of the resin-root canal dentine interface of four "etch and rinse" adhesive systems. Forty human teeth were restored through a fiber post insertion using: Group 1: XP Bond adhesive; Group 2: Prime & Bond NT; Group 3: Surgi Prime Bond adhesive; Group 4: Scotchbond Multi-Purpose Plus. Two cross-sections (apical and coronal) were obtained and analyzed in morphological confocal laser scanning microscope. The numbers of resin tags (RT) and the thickness of the hybrid layer (HL) were evaluated. Quantitative variables were tested by a Shapiro-Wilk test. Parametric variables by an Anova test. Group 4 produced the thickest HL and Group 1 showed the thinnest. Considering RT, Group 1 produced the highest density, while Group 3 the lowest density. All the adhesives produced good results in terms of HL thickness and RT density.

Nanoleakage at the resin-dental interface of four self-etching adhesives

To evaluate the nanoleakage and ultramorphology of four self-etching adhesives. Sixteen freshly extracted, caries-free human third molars were selected. A flat dentin surface was exposed by removing occlusal enamel. All teeth were randomly divided into four groups acorrding to four different self-etch adhesive: Adper Prompt (A), iBond (B), Xeno III (C) and SE Bond (D). The dentin were bonded with dentin adhesive system according to manufacturer's directions. Composite layers were built up incrementally. The specimens were sectioned longitudinally across the resin-dentin interface into 4.0 mm×0.9 mm sticks and then traced with ammoniacal silver solution. Epoxy resin-embedded sections were prepared for transmission electron microscope (TEM) to observe nanoleakage. The images were qualitatively compared by NIH software, and data was analyzed by SPSS. Different thickness of hybrid layer and adhesives layer were observed for each adhesive. The hybrid layer of A, C was thicker than that of B, D, and adhesive layer of D was thicker than the others. The extent of nanoleakage varied among different adhesives: A (45.02 ± 9.49), B (43.97 ± 8.55), C (27.02 ± 10.86), D (12.94 ± 2.07). D presented significantly less silver deposition than any of the others did (P < 0.05). The thickness of hybrid layer and adhesive layer vary among the four adhesives. The shape and extent of nanoleakage of each adhesive are also different. Two-step system shows less nanoleakage than one-step systems do.

Use of micro‐Raman spectroscopy to investigate hybrid layer quality in demineralized root dentine

Treatment of early root caries using resin adhesives to stabilize demineralized dentine and deprive bacteria of nutrients is a recognized and conservative treatment option. Essential to its success is a stable resin-dentine interface, with effective infiltration of demineralized dentine and adequate resin curing. The objective of this study was therefore to examine degree of cure (DoC) and depth of penetration of dentine adhesives in demineralized dentine using micro-Raman spectroscopy. Three commercially available adhesives were applied essentially according to manufacturers' instructions to visibly wet demineralized dentine, with two coats of primer to reduce dilution. Specimens were sectioned perpendicular to the bonded interface and micro-Raman spectroscopy performed on the cross section. Molecules associated with the adhesive were detected to depths greater than 100 μm indicating a thicker hybrid layer than seen in sound dentine. The hybrid layer showed an increase in proportion of aliphatic C=C double bonds at the base of the hybrid layer, which may be a consequence of reduced DoC or phase separation. Micro-Raman spectra suggest deep zones contain an increased concentration of HEMA and a lower concentration of BisGMA, which is likely to be less stable and may contribute to early breakdown of the dentine adhesive interface.

Effect of Hybrid Layer and Thickness on Stress Distribution of Cervical Wedge-Shaped Restorations

The aim of this finite elemental stress analysis study was to evaluate the effect of a hybrid layer and the hybrid layer thickness on the shear stress distribution in mandibular premolar teeth under occlusal loading. The mandibular premolar tooth was selected based on the anatomical measurements suggested by Wheeler. The analysis was performed with a computer with the SAP 2000 structural analysis program. Three different mathematical models were evaluated; 1) composite restoration without a hybrid layer 2) composite restoration with a 1.5 mum thick hybrid layer and 3) composite restoration with a 3 mum thick hybrid layer. A total of 200 N of occlusal loading force was simulated from the buccal tubercule and central fossa of the premolar tooth. The findings were drawn by the Saplot program. In model B, the output showed that hybrid layer reduced the shear stress concentration especially on gingival margin of the composite. Similarly shear stress intensity was decreased by a thick hybrid layer in model C, especially on the gingival margin of the composite. The hybrid layer and its thickness plays an important role on stress distribution and intensity in cervical restorations.

Bonding effectiveness of two contemporary self-etch adhesives to enamel and dentin

Objectives Among contemporary adhesives, self-etch adhesives have been adopted by general practitioners for routine adhesive restorative purposes, mainly because of their ease of use. However, many versions that differ for their clinical application procedure, pH, number of components, etc., are currently available on the market. The purpose of this study was to determine the bonding effectiveness of two new self-etch adhesives (Adper Easy Bond and Adper ScotchBond SE, 3M ESPE) to enamel and dentin using a micro-tensile bond strength (μTBS) protocol and to characterise the interfacial ultra-structure at enamel and dentin using transmission electron microscopy (TEM). Methods The adhesives were applied onto coronal human enamel and dentin surfaces and built up with the micro-hybrid resin composite Z100 (3M ESPE). The ‘gold-standard’ two-step self-etch adhesive Clearfil SE Bond (Kuraray) served as control. Specimens were sectioned to sticks and trimmed at the interface to a cylindrical hour-glass shape (‘trimmed’ micro-specimens). Non-demineralized and demineralized TEM sections through the adhesive-dentin/enamel interface were prepared by ultra-microtomy. Results The μTBS of the two self-etch adhesives to enamel was statistically significantly lower than that of the control. To dentin, the μTBS of Adper Easy Bond was significantly lower than that of Adper ScotchBond SE and the control. TEM showed a tight interface to enamel for all three self-etch adhesives. A relatively thick, completely demineralized and acid-resistant hybrid layer was formed at dentin by Adper ScotchBond SE, whereas the interaction of Adper Easy Bond was much shallower, and comparable to that of so-called ‘ultra-mild’ self-etch adhesives. Some degree of spot- and cluster-like nano-leakage was observed for both adhesives, but did not differ in extent and form from that observed for the control. Conclusions Although the new two self-etch adhesives revealed a tight interaction at both enamel and dentin, their bond strength to both tooth tissues was generally lower than that of the control adhesive. Nevertheless, their bonding effectiveness appears in line with other simplified self-etch adhesives.

Morphological and bond strength evaluation of different resin cements to root dentin

This study correlated the morphological characteristics with the bond strengths of various resin cements used for bonding fiber posts to root canal dentin. Fifty glass-fiber posts (FRC Postec Plus) were luted into the root canals of extracted human anterior teeth using five resin cements (n = 10): Panavia F 2.0, PermaFlo DC, Variolink II, RelyX Unicem, and Clearfil Core. Before insertion of the post, the adhesive systems were labeled with fluorescein and the resin cement was labeled with rhodamine isothiocyanate. The roots were sectioned into three slices (of 2 mm thickness), and each slice was analyzed using confocal laser scanning microscopy in dual fluorescence mode to determine hybrid layer thickness, the number of resin tags, and the number of broken tags. Bond strengths were measured using a micro push-out test. Bond strengths to root canal dentin, as well as the morphological characteristics, were significantly affected by the materials. However, these factors did not correlate. The self-adhesive resin cement, which showed the formation of a hybrid layer and resin tags only sporadically, had the highest bond strengths. These results indicate that chemical interactions between the adhesive cement and hydroxyapatite may be more crucial for root dentin bonding than the ability of the same material to hybridize dentin.

Bonding effectiveness and interfacial characterization of a HEMA/TEGDMA-free three-step etch&rinse adhesive

Small and hydrophilic monomers as HEMA and TEGDMA can easily penetrate human tissues. For biocompatibility issues it is therefore better to avoid such monomers in dental adhesive formulations. The purpose of this study was (1) to determine the micro-tensile bond strength (muTBS) to enamel/dentin of a HEMA/TEGDMA-free three-step etch&rinse adhesive (cmf Adhesive System, Saremco), and (2) to characterize it's interfacial interaction with enamel/dentin using transmission electron microscopy (TEM). Twelve intact freshly extracted human third molars were used for muTBS. The three-step etch&rinse adhesive OptiBond FL (Kerr) served as control adhesive. After bonding procedures and subsequent composite build-up (Z100, 3M ESPE), specimens were sectioned to sticks and trimmed at the interface to a cylindrical hour-glass shape. TEM section of non-demineralized and demineralized sections were prepared by ultra-microtomy and examined. The muTBS of the cmf Adhesive System to enamel was not statistically significantly different from that of the control (OptiBond FL) adhesive (p=0.3512); the muTBS to dentin was however significantly lower (p<0.0001). TEM showed a tight interface at enamel for both adhesives. A relatively thick, completely demineralized and acid-resistant hybrid layer was formed at dentin. Some degree of spot- and cluster-like nano-leakage was observed with cmf Adhesive System, but did not differ in extent and form in comparison to that observed with the OptiBond FL control. The new three-step adhesive cmf Adhesive System showed indications of good bonding effectiveness, certainly to enamel and only significantly lower to dentin, when compared to the gold-standard adhesive. The latter may be related to the adapted HEMA/TEGDMA-free formulation and the somewhat lower mechanical properties.

Comparison of the hybrid layer formed by Silorane adhesive, one-step self-etch and etch and rinse systems using confocal micro-Raman spectroscopy and SEM

Objectives To determine the extent of the hybrid layer (HL) of the novel adhesive system (Silorane, 3M ESPE) compared to one-step and etch and rinse adhesive systems, using 2D confocal micro-Raman spectroscopy and SEM. Methods Silorane adhesive system was compared to two one-step self-etch (G Bond, GC; AdheSE One, Ivoclar Vivadent) and etch and rinse (Excite, Ivoclar Vivadent) as controls. Adhesives were applied to human dentine, cured and sections prepared perpendicular to the flat adhesive–dentine surface. Two-dimensional micro-Raman mapping was performed over 20 μm × 20 μm areas across the adhesive–dentine interface. SEM micrographs of the same specimens were obtained. One-way ANOVA (Tukey's post-test) was used to analyse the differences in HL thickness among the four adhesive systems and the paired t-test to compare the results obtained by micro-Raman and SEM for each adhesive. Results Silorane adhesive system formed a HL of comparable thickness to methacrylate-based but thicker than the acrylamide-based one-step self-etch adhesives from SEM analysis. A gradual decrease in adhesive penetration was observed in all systems. A 1-μm zone, between the cured primer and bond was identified by Raman but not visualised on SEM. Compared to SEM, HL calculated from Raman data were always greater. Conclusions Micro-Raman spectroscopy gives a more precise indication of dentine demineralisation and monomer infiltration and highlights the intermediate zone of ∼1 μm between Silorane primer and bond, not visible with SEM at ×10,000 magnification. Giving as it does, a compilation of many linear scans it allows HL mean values to be calculated.

Nano-Hardness of Adhesive Interface between Er:YAG Laser-Irradiated Dentin and 4-META/MMA-TBB Resin

The purpose of this study was to evaluate the hardness of the adhesive interface between resin and Er:YAG laser-irradiated bovine dentin by nano-indentation. It has been reported that laser output energy and pulse repetition rate affect the tensile bond strength in Er:YAG laser-irradiated dentin. Three laser settings were evaluated at the same total energy level (approximately 1.0 W): 100 mJ/pulse-10 pps (100-10), 50 mJ/pulse-20 pps (50-20), and 33 mJ/pulse-30 pps (33-30). Laser-irradiated dentin in each group was conditioned with 10% citric acid solution containing 3% ferric chloride for 15 sec, rinsed with distilled water for 30 sec, and bonded to PMMA rods with 4-META/MMA-TBB resin. The bonded specimens were sectioned vertically, embedded in epoxy resin, and their nano-hardness measured. A non-irradiated control group was also investigated. The adhesive resin interface in the controls showed the lowest level of hardness, which gradually increased from the top of the hybrid layer (0 microm) through the bottom of the hybrid layer (5 microm) and into the underlying dentin ( approximately 10 microm). Significant differences in hardness were observed between the 5 microm point in the controls, the 10 microm and 15 microm points in the 100-10 group, and the 10 microm point in the 50-20 and 33-30 groups. The results suggest that laser settings affect hybrid layer thickness, even when the total energy level is constant.

A Comparative Evaluation of Tensile Bond Strength and Hybrid Layer of Three Generation Bonding Agents by Scanning Electron Microscope (An In-vitro Study)

ABSTRACT This study was done to compare the tensile bond strength of three different generation bonding agents to dentin using one composite resin and scanning electron microscopic study (SEM) of hybrid layer. In this study 36 non carious human molar teeth were selected. 30 teeth were used for evaluating tensile bond strength and were divided in to three groups. Six teeth were used for hybrid layer evaluation also divided into three groups. Group 1 specimens 10 teeth were etched with 37% phosphoric acid and Scotch bond multipurpose adhesive was applied. Group 2 specimens 10 teeth were etched with 37% phosphoric acid and 3M Single bond was applied. Group 3 specimens 10 teeth were treated with Prompt-L-Pop. Composite material (3M- Hybrid-Z100) was applied incrementally and cured for 40 seconds each. Specimens were then stored in distilled water before testing. Two teeth from each group were cross-sectioned to obtain 1mm thick dentin disks for SEM evaluation. Adhesives were applied as mentioned above. Composite was applied over these discs and light cured for 40 seconds. Samples were stored in distilled water at 37°c for two weeks; these disks were fractured with chisel for cross-sectional viewing Dentin conditioning with single bond (5th Generation) revealed better bond strengths as compared to scotch bond multipurpose (4th generation) and Prompt-L-Pop (6th generation). SEM evaluation of hybrid layer reveals that Single bond has shown a thicker hybrid layer comparing to other adhesives.