Thickness Of Hybrid Layer Research Articles

Broadband visible perfect absorber for sensor based on ultra-thin metamaterial

A metamaterial perfect absorber having a hybrid layer and total thickness of 50 nm is demonstrated in this paper. The results indicate that a broadband absorption above 90% is achieved from 421.2 to 671.8 THz and the absorption of 99.8% can be obtained at the absorption peaks. The absorption is also illustrated to be polarization insensitive under vertical incidence. Furthermore, the broadband and high-efficient absorption are sustained over a wide incident angle range. In addition, the impedance matching theory, surface current distributions, and power loss at the resonant frequencies are also discussed. Moreover, this study demonstrates the application of different permittivity on the performance of the sensor.

ROOT CANAL DENTIN;

Objectives: To compare the mean thickness of hybrid layer by using selfetchadhesive at coronal dentin and root canal dentin with scanning electronic microscope.Study Design: Experimental study. Setting: Liaquat University of Medical & Health Sciences,Jamshoro. Period: July 2009 to 31st December 2009. Material & Methods: Fifty permanentsingle rooted extracted teeth were used in this study. The sample size was divided into twoequal groups of 25 teeth each. Group 1(n=25) self etch adhesive was applied on coronal dentinthen light cured for 10seconds. Group 2(n=25)self etch adhesive to root canal dentin and thenlight cured was applied for 10seconds then 2mm thick layer was placed to adhesive bondedsurfaces of coronal and root canal dentin. Data were analyzed using t-test of significance. p-Value was significant at ≤0.05. Results: The mean ±standard deviation of thickness of hybridlayer was 2.3088 ±1.027 um in coronal dentin; and it was 2.1104 ±1.0316 um in root canaldentin. Conclusion: There is no statistically significant differences in mean thickness of hybridlayer between root canal dentin and coronal dentin with self etch adhesive.

Push-Out Bond Strength of Quartz Fiber Posts Luted with Self-Adhesive and Conventional Resin Cements

The aim of this study was to evaluate the influence of the resin cement on push-out bond strength of quartz fiber posts to intraradicular dentin. Fifty-six single-rooted human teeth were selected. After removing the crown, roots were endodontically treated and the dowel spaces were prepared with # 2 post drills of DT Ligth® SL Post System (VDW®). The specimens were randomly divided into four groups (n = 14). Group 1: RelyX™ Unicem (3M ESPE), Group 2: Clearfil ™ SA Cement (Kuraray), Group 3: Bifix SE (Voco), and G4 RelyX™ ARC (3M ESPE). After 24 h, 12 specimens of each group were sectioned in 6 slices with 1 mm of thickness, two of each radicular third. The push-out test was conducted in an Instron machine at 0.5 mm/min. Data were submitted to ANOVA and Bonferroni test. Fractured specimens were observed at 25X to evaluate the types of failures. Two specimens of each group were processed for SEM evaluation. The Mean values (MPa) for groups 1, 2, 3 and 4 were respectively: 11.06, 8.85, 8.37 and 13.36. All experimental groups showed higher values of resistance in the cervical third, while the lowest were in the apical third. Adhesive failures between cement and dentin (46.87 %) prevailed, followed by mixed failures (45.15 %). SEM photomicrographs illustrating the interface formed between the self-adhesive resin cements and dentin showed an interface without the formation of a hybrid layer. G4 showed the formation of a thick and homogeneous hybrid layer with resin tags. The conventional resin cement associated with a three-step adhesive system displayed the higher bond strength to intraradicular dentin, when compared to the different self-adhesive resin cements.

Push-Out Bond Strength of Quartz Fiber Posts Luted with Self-Adhesive and Conventional Resin Cements

The aim of this study was to evaluate the influence of the resin cement on push-out bond strength of quartz fiber posts to intraradicular dentin. Fifty-six single-rooted human teeth were selected. After removing the crown, roots were endodontically treated and the dowel spaces were prepared with # 2 post drills of DT Ligth® SL Post System (VDW®). The specimens were randomly divided into four groups (n = 14). Group 1: RelyX™ Unicem (3M ESPE), Group 2: Clearfil ™ SA Cement (Kuraray), Group 3: Bifix SE (Voco), and G4 RelyX™ ARC (3M ESPE). After 24 h, 12 specimens of each group were sectioned in 6 slices with 1 mm of thickness, two of each radicular third. The push-out test was conducted in an Instron machine at 0.5 mm/min. Data were submitted to ANOVA and Bonferroni test. Fractured specimens were observed at 25X to evaluate the types of failures. Two specimens of each group were processed for SEM evaluation. The Mean values (MPa) for groups 1, 2, 3 and 4 were respectively: 11.06, 8.85, 8.37 and 13.36. All experimental groups showed higher values of resistance in the cervical third, while the lowest were in the apical third. Adhesive failures between cement and dentin (46.87 %) prevailed, followed by mixed failures (45.15 %). SEM photomicrographs illustrating the interface formed between the self-adhesive resin cements and dentin showed an interface without the formation of a hybrid layer. G4 showed the formation of a thick and homogeneous hybrid layer with resin tags. The conventional resin cement associated with a three-step adhesive system displayed the higher bond strength to intraradicular dentin, when compared to the different self-adhesive resin cements.

Nd:YAG laser influence on the hybridization quality, employing total-etching or self-etching adhesives: sem analysis

Background: The application of Nd:YAG laser on dentin with the adhesive system non-polymerized can influenced the quality of hybrid layer formed. Objectives: The aim of this study is to assess through analysis by scanning electronic microscopy (SEM), the Nd:YAG laser influence on the hybridization quality, using conventional Adper Single Bond (SB) or self-etching Clearfil SE Bond-Kuraray (CSEB) adhesives. Methods: Nine bovine incisors were treated on their incisal with SB and with CSEB in their cervical portion. They were divided into 3 groups with 6 specimens in each and treated as follows; G1- adhesive system and polymerization; G2- adhesive system, laser (60mJ/pulse) and polymerization; G3- adhesive system, laser (140mJ/pulse) and polymerization. All samples were restored with composite resin (Filtek Z350-3M). The thickness, the presence of failures (gap/porosity) and tags/microtags in the hybrid layer were analyzed using the SEM. The data were submitted to ANOVA and Tukey statistical tests 5%. Results: The highest average of hybrid layer thickness (1.89±0.15) was observed for G3 and the smallest was observed for G1-CSEB (1.36±0.14). The multiple comparison of ratio test showed that the smallest prevalence of failures was for G3-CSEB and the best performance for the presence of tags/microtags was found for G2-SB. Conclusion: Independent of the adhesive system used, the Nd:YAG laser, according to the parameter applied, had a positive influence on the hybridization quality.

Dentin bonding performance using Weibull statistics and evaluation of acid-base resistant zone formation of recently introduced adhesives.

Dentin bonding durability of recently introduced dental adhesives: Clearfil SE Bond 2 (SE2), Optibond XTR (XTR), and Scotchbond Universal (SBU) was investigated using Weibull analysis as well as analysis of the micromorphological features of the acid-base resistant zone (ABRZ) created for the adhesives. The bonding procedures of SBU were divided into three subgroups: self-etch (SBS), phosphoric acid (PA) etching on moist (SBM) or dry dentin (SBD). All groups were thermocycled for 0, 5,000 and 10,000 cycles followed by microtensile bond strength testing. Acid-base challenge was undertaken before SEM and TEM observations of the adhesive interface. The etch-and-rinse method with SBU (SBM and SBD) created inferior interfaces on the dentin surface which resulted in reduced bond durability. ABRZ formation was detected with the self-etch adhesive systems; SE2, XTR and SBS. In the PA etching protocols of SBM and SBD, a thick hybrid layer but no ABRZ was detected, which might affect dentin bond durability.

Üniversal bir adezivin ER:YAG lazerle prepare edilmiş çürükten etkilenmiş dentine mikrogerilim bağlanma dayanımı

The microtensile bond strength of universal adhesive on caries-affected dentin after ER:YAG laser treatment Background: The aim of this study was to evaluate the microtensile bond strength (μTBS) of an universal adhesive system on Er-YAG laser treated caries affected dentine. Methods: Ten molar teeth with coronal caries were randomly divided into two groups according to the bonding technique performed (group 1); self-etch adhesive (group 2), etchr noncontact) laser was used to remove caries, and the teeth were irradiated until the soft and demineralized dentin removed. Then Single bond universal adhesive agent (3M ESPE) was applied to teeth according to the manufacturers’ instructions and restored with the same light-cured composite resin material (Universal restorative 200 3M, ESPE). Teeth were then subjected to thermocycling for 2500 cycles at a temperature of 5°C and 55°C with a dwell time of 10 seconds. Resin-dentin sticks (n=10) were obtained with diamond saw and subjected to μTBS test. One tooth of each group was examined using scanning electron microscopy. Statistical analysis was performed in SPSS for Windows 15.0. Mann-Whitney U test was used for comparing the groups at a significance level of p0.05). One of the sample from each group was examined using scaning electron microscopy. Results: Although higher μTBS record obtained from group 1, between these two groups statistically significant difference was not observed (p˃0.05). Hybrid layer formation between composite resin and dentin bonding interface was a thin layer observed by SEM in group 1, in group 2 a thick hybrid layer was found. Conclusion: It can be concluded that both self-etch approach and etch & rinse approach can be used for adhesive restorations to caries affected dentine after Er-YAG laser irradiation of molar teeth.

Evaluation of hybrid layer thickness and resin tag length of self-etch adhesives with different ph using confocal laser scanning microscope: an in vitro study

The aim of this in vitro study is to evaluate the hybrid layer thickness and resin tag length of self-etches adhesives with different pH using Confocal Laser Scanning Microscope (CLSM). Total 40 teeth was prepared and divided into four groups. Group-I (Prime and Bond NT), group-II: (Xeno III), group-III: (Xeno V) and group-IV: (Xeno IV). Each group contains 10 teeth. The samples were mounted on Borosilicate cover glass with cover slip. The excitation laser light was generated with a wavelength 514nm. The image was recorded in fluorescent mode and hybrid layer and resin tag length were visualized as green. They were analyzed, and thickness of hybrid layer and length of resin tag were measured by means of Image Browser software (zeiss, Germany) in micrometers. Results were tabulated and mean obtained. Group-I (Prime and Bond NT) showed the maximum values for hybrid layer thickness & resin tag length compared to group-II (Xeno III), group-III (Xeno V) and group-IV (Xeno IV). Among the self-etching primer group-II (Xeno III) with strong pH (<1) gave higher values for hybrid layer thickness and resin tag length. Among the self-etching adhesives, strong self-etch adhesive showed the maximum hybrid layer thickness and resin tag length. Further studies with more parameters must be conducted to evaluate the resin-dentin interface.

Micro-arc oxidation as a tool to develop multifunctional calcium-rich surfaces for dental implant applications.

Titanium (Ti) is commonly used in dental implant applications. Surface modification strategies are being followed in last years in order to build Ti oxide-based surfaces that can fulfill, simultaneously, the following requirements: induced cell attachment and adhesion, while providing a superior corrosion and tribocorrosion performance. In this work micro-arc oxidation (MAO) was used as a tool for the growth of a nanostructured bioactive titanium oxide layer aimed to enhance cell attachment and adhesion for dental implant applications. Characterization of the surfaces was performed, in terms of morphology, topography, chemical composition and crystalline structure. Primary human osteoblast adhesion on the developed surfaces was investigated in detail by electronic and atomic force microscopy as well as immunocytochemistry. Also an investigation on the early cytokine production was performed. Results show that a relatively thick hybrid and graded oxide layer was produced on the Ti surface, being constituted by a mixture of anatase, rutile and amorphous phases where calcium (Ca) and phosphorous (P) were incorporated. An outermost nanometric-thick amorphous oxide layer rich in Ca was present in the film. This amorphous layer, rich in Ca, improved fibroblast viability and metabolic activity as well as osteoblast adhesion. High-resolution techniques allowed to understand that osteoblasts adhered less in the crystalline-rich regions while they preferentially adhere and spread over in the Ca-rich amorphous oxide layer. Also, these surfaces induce higher amounts of IFN-γ cytokine secretion, which is known to regulate inflammatory responses, bone microarchitecture as well as cytoskeleton reorganization and cellular spreading. These surfaces are promising in the context of dental implants, since they might lead to faster osseointegration.

Effect of Er:YAG laser and diamond drill on hybrid layer morphology obtained with self-etch adhesive – analysis by SEM and confocal laser scanning microscopy (CLSM)

This study aimed to evaluate the effect of Er:YAG (L) and diamond drills (DD) on: 1) the microshear bond strength (MPa); 2) the adhesive interface of two-step (TS) – Adper Scotchbond Multipurpose and one-step (OS) adhesives – Adper EasyOne, both from 3M ESPE. Material and methods:According to the preparation condition and adhesives, the samples were divided into four groups: DD_TS (control); DD_OS; L_TS and L_OS. 60 bovine incisors were randomly divided into experimental and groups: 40 for microshear bond strength (n = 10) and 20 for the adhesive interface morphology [6 to measure the thickness of the hybrid layer (HL) and length of tags (t) by CLSM (n = 3); 12 to the adhesive interface morphology by SEM (n = 3) and 2 to illustrate the effect of the instruments on dentine by SEM (n = 1)].To conduct the microshear bond strength test, four cylinders (0.7 mm in diameter and 1 mm in height with area of adhesion of 0.38 mm) were constructed with resin composite (Filtek Z350 XT – 3M ESPE) on each dentin surface treated by either L or DD and after adhesives application. Microshear bond strength was performed in universal testing machine (EMIC 2000) with load cell of 500 kgf and a crosshead speed of 0.5 mm / min. Adhesive interface was characterized by thickness of hybrid layer (HL) and length of tags (t) in nm, with the aid of UTHSCSA ImageTool software. Results: Microshear bond strength values were: L_TS 34.10 ± 19.07, DD_TS 24.26 ± 9.35, L_OS 33.18 ± 12.46, DD_OS 21.24 ± 13.96. Two-way ANOVA resulted in statistically significant differences only for instruments (p = 0.047). Mann-Whitney identified the instruments which determined significant differences for HL thickness and tag length (t). Concerning to the adhesive types, these differences were only observed for (t). Conclusion: It can be concluded that 1) laser Er:YAG results in higher microshear bond strength values regardless of the adhesive system (TS and OS); 2) the tags did not significant affect the microshear bond strength; 3) the adhesive interface was affected by both the instruments for cavity preparation and the type of adhesive system used.

Hybrid layer of etch and rinse versus self-etching adhesive systems: A comparative study

Aim: This study is to evaluate the effectiveness in the formation of resin tags, and hybrid layers of self-etching adhesives and total etch adhesives of total etch and two self-etching bonding systems to dentine surface by scanning electron microscopic study. The etch and rinse system shows thick hybrid layer than self-etching systems. Result: The resin tags formation in etch and rinse system is much longer than self-etch sixth and seventh generation bonding systems and bonding interface is more uniform in two self-etching bonding systems than total etch bonding resin supporting null hypotheses. Conclusion: Self-etching bonding agents containing acidic monomer is able to penetrate dissolve the smear layer to form a more uniform hybrid layer. However, the long-term durability of self-etching bonding system should be evaluated.

Evaluación de la interfase adhesiva obtenida en restauraciones de resina compuesta realizadas con un sistema adhesivo universal utilizado con y sin grabado ácido previo

ObjectiveThe purpose of this research was to study the tooth-restoration adhesive interface, using a universal adhesive system (Single Bond Universal, 3M/ESPE, Germany), with the techniques of etching and self-etching using scanning electron microscopy. Material and methodsClass V cavities were prepared in buccal and palatine/lingual surface, in human teeth. Etching with 37%H3PO4 was performed in the buccal cavity, with no etching being performed in the palatine or lingual cavity. The samples were placed in an oven at 37°C and 100% humidity for 48hours, simulating the oral environment. The samples were cut perpendicularly through the restoration and prepared to be observed by scanning electron microscopy, in order to evaluate the adhesive interface in relation to the presence of breaches and the formation of resin tags. ResultsImages were observed with a gradual increase to 2000×. Microstructural differences were observed in the penetration of the adhesive but with no formation of breaches in the adhesive interface. ConclusionsAn unbreached interface is obtained when using both techniques. In enamel, less penetration was present in the crystal structure of the adhesive with the self-etching technique. While in dentin, with the same technique, a less thick hybrid layer and shorter resin tags were observed.

The Effect of Different Dental Adhesive Systems on Hybrid Layer Qualities

The study aimed to evaluate the quality of the hybrid layer form by three different adhesive systems. Class V cavities were prepared on the buccal surface of fourty extracted human premolars. The prepared teeth were randomly assigned into four groups according to the adhesive system and application mode. The systems were: Optibond S (OS, total-etch); Optibond Versa (OV, two-bottles, self-etch); Single Bond Universal (SBU, one-bottle, self-etch) and Single Bond Universal with etchant (SBU + etchant). All cavities were restored with composite (Filtek Z350XT). The samples were sectioned, polished and pretreated to remove minerals, protein and water prior to SEM evaluation. From the images, thickness of the hybrid layers was measured. Present of resin tags and adaptation failure were also recorded. The data obtained were analyzed using ANOVA, Dunnett’s T3, Kruskal-Wallis and Mann-Whitney tests. OS group showed the highest average hybrid layer thickness (4.34 μm), followed by SBU + etchant (3.06 μm), OV (1.91 μm) and SBU (0.95 μm). Both adhesive and cohesive failures were observed in SBU group. Present of prominent resin tags were seen in both OS and OV groups. In conclusion, all the investigated adhesive systems were able to perform distinguishable actions as shown in micro-morphological alteration and hybrid layer thickness. Two-bottles, self-etch adhesive (OV) was proven to produce negligible adaptation failure compared to other adhesive systems in the present study. Combined all-in-one adhesive (SBU) was found to render a superior bonding performance in total-etch mode comparing to self-etch mode.

Proteoglycans affect monomer infiltration in the etch-and-rinse bonding technique

ObjectivesTo identify proteoglycans (PGs) and collagen fibrils (CF) within human dentin by means of a dual immunofluorescent labeling technique and to investigate the monomer infiltration of two etch-and-rinse adhesives to tosyl-phenylalanine chloromethyl-ketone (TPCK)-treated trypsin (TRY)-pretreated dentin. MethodsThirty-micrometer sections of middle coronal dentin were obtained and etched with 37% phosphoric acid gel for 15s. After preconditioning with or without TRY digestion, the sections were subjected to dual immunofluorescent labeling and observed with a confocal laser scanning microscope (CLSM). Demineralized dentin matrixes treated with or without TRY were observed with field emission scanning electron microscope (FE-SEM). Two etch-and-rinse adhesives, Adper Single Bond 2 (SB) and Prime & Bond NT (PBNT), were applied to the dentin surfaces that were pretreated with or without TRY. The thickness of the hybrid layers was evaluated under confocal micro-Raman spectroscopy and analyzed with a two-way ANOVA. ResultsGreen and red fluorescence was used to represent the PGs and the CF that were colocalized in the same section with different distributions. PGs were localized in the lumens of the dentin tubules and in peritubular dentin, while the type-I collagen fibrils were localized in intertubular dentin and peritubular dentin. After preconditioning with TRY digestion, the red fluorescence decreased or disappeared, the organic filaments in the lumens of the dentin tubules disappeared, the tubules were enlarged, and the hybrid layer thickness for adhesives bonded to the TRY-pretreated dentin surfaces were significantly increased (p<0.001 for both SB and PBNT). SignificanceThe dual immunofluorescence labeling methodology can be used to study the human dentin matrix without decalcifying the entire dentin fragment. Proteoglycans were localized in the lumens of the dentin tubules and in peritubular dentin, which could depress the infiltration of the adhesive resin monomers. The use of TRY digestion increased the thickness of the hybrid layer created by the tested two-step etch-and-rinse adhesive.

Formation of Expanded Austenite Using Hybrid Low Temperature Thermochemical Heat Treatment on 2205 Duplex Stainless Steel

Surface modification on 2205 duplex stainless steel (DSS) was performed by low temperature thermochemical hybrid (nitrocarburizing) heat treatment at temperature of 450° C and at holding time of 30 hours. During the process, carbon and nitrogen elements were simultaneously introduced onto the surface of DSS with composition of 5%CH4 + 25% NH3 + 70% N2. Microstructural observations reveal the formation of thick diffusional hybrid layer on the surface of 2205 DSS with very high hardness at cross sectional area. Both carbon and nitrogen diffusions formed expanded austenite (γN/C) and expanded ferrite (αC), however precipitation of nitride (Cr2N) which also occurred at the layer may deteriorate the corrosion resistance of 2205 DSS. Further investigation is required based on the parameters used in the process to produced precipitation free hybrid layer.

Analysis of Resin-Dentin Interface Morphology and Bond Strength Evaluation of Core Materials for One Stage Post-Endodontic Restorations

PurposeRestoration of endodontically treated teeth using fiber posts in a one-stage procedure gains more popularity and aims to create a secondary monoblock. Data of detailed analyses of so called “post-and-core-systems” with respect to morphological characteristics of the resin-dentin interface in combination with bond strength measurements of fiber posts luted with these materials are scarce. The present study aimed to analyze four different post-and-core-systems with two different adhesive approaches (self-etch and etch-and-rinse).Materials and MethodsHuman anterior teeth (n = 80) were endodontically treated and post space preparations and post placement were performed using the following systems: Rebilda Post/Rebilda DC/Futurabond DC (Voco) (RB), Luxapost/Luxacore Z/Luxabond Prebond and Luxabond A+B (DMG) (LC), X Post/Core X Flow/XP Bond and Self Cure Activator (Dentsply DeTrey) (CX), FRC Postec/MultiCore Flow/AdheSE DC (Ivoclar Vivadent) (MC). Adhesive systems and core materials of 10 specimens per group were labeled using fluorescent dyes and resin-dentin interfaces were analyzed using Confocal Laser Scanning Microscopy (CLSM). Bond strengths were evaluated using a push-out test. Data were analyzed using repeated measurement ANOVA and following post-hoc test.ResultsCLSM analyses revealed significant differences between groups with respect to the factors hybrid layer thickness (p<0.0005) and number of resin tags (p = 0.02; ANOVA). Bond strength was significantly affected by core material (p = 0.001), location inside the root canal (p<0.0005) and incorporation of fluorescent dyes (p = 0.036; ANOVA). CX [7.7 (4.4) MPa] demonstrated significantly lower bond strength compared to LC [14.2 (8.7) MPa] and RB [13.3 (3.7) MPa] (p<0.05; Tukey HSD) but did not differ significantly from MC [11.5 (3.5) MPa].ConclusionIt can be concluded that bond strengths inside the root canal were not affected by the adhesive approach of the post-and-core-system. All systems demonstrated homogenous hybrid layer formation and penetration into the dentinal tubules in spite of the complicating conditions for adhesion inside the root canal.

Clinical recipe for durable dental bonding: why and how?

Current dental adhesive technology involves either an etch-and-rinse or self-etching approach.8 Evidence of clinical durability exists for both approaches, albeit depending on the specific brand.4,5 Today, enamel still requires phosphoric-acid etching and thus an etch-andrinse approach to obtain a durable bond. The adhesiveenamel bond seals the cavity and even protects the more vulnerable bond to adjacent dentin.3 Although functional monomers in self-etching adhesives are designed to chemically interact with hydroxyapatite (HAp), the structure, size, and orientation of enamel HAp crystals appear to provide insufficient chemical bonding sites to achieve durable bonding to enamel. As a rule, the micromechanical interlocking provided by the etch-and-rinse step remains necessary. For dentin, phosphoric acid may be less preferable, as adhesives generally cannot envelop the exposed collagen tightly enough to make the relatively thick hybrid layer resistant to hydrolytic and enzymatic degradation processes.2 Ethanol wet bonding6 and biomimetic repair7 by remineralization of etch-andrinse hybrid layers have proven to be effective. However, these techniques are rather time consuming, which makes their applicability questionable for routine clinical practice. Moreover, the use of MMP inhibitors applied separately or mixed with the primer/adhesive appeared to retard rather than prevent bond degradation.1,6 Another strategy employed in the attempt to improve bond durability to dentin involves chemical interaction of functional monomers with HAp following a “mild” self-etching approach.9 Among the current functional monomers investigated, the phosphate monomers 10-MDP and more recently also MF8P were documented to bond durably to hydroxyapatite.9,12 In addition, correlative chemical (XRD, NMR) and high-resolution (TEM) structural interfacial analysis revealed that both monomers self-assemble into nanolayers, consisting of two monomer molecules joined by stable monomer-Ca salt formation.10,11 The stable bond formed to HAp along with interfacial nanolayering is thought to be the basis for the more biodegradation-resistant adhesive interface. Strategies to intensify nanolayering need to be explored further. Clinical Recipe for Durable Dental Bonding: Why and How?

Effect preparation on the hybrid layer with resin cement

Purpose: The aim of this study was to evaluate the effect of preparation mode of dentin on the thickness and quality of hybrid layer with resin cement and an adhesive system. Methods and materials: Sixty sound human teeth extracted within six months were obtained from the Uberaba University human tooth bank under ethical approval # 27584814.2.0000.5145. The teeth were cut 2mm below the ADJ mesio-distally to expose the coronal dentin and divided into three groups (n=15). (1) The dentin surface was prepared with a fine particle diamond bur; (2) with a course particle diamond bur and (3) with multi laminated carbide bur. Composite resin blocks (Tetric Ceram, Ivoclar-Vivadent) were fabricated and cemented on the dentin surfaces with Single Bond Universal adhesive system mixed with OPC bioactivator and RelyX ARC resin cement (all from 3MESPE) and stored for 24h in distilled water at 37 ◦C. Following, the restored teeth were sectioned perpendicular to the bonding surface using a low speed saw machine to obtain sections of 1mm thickness. The section pieceswere cleaned and individually embedded in epoxy resin (Buehler) and after the resin polymerization the pieces were prepared to scanning electron microscope analysis to verify the hybrid laser. Results: The fine particle diamond bur (6.55 m) produced a thinner hybrid layer compared to the coarse diamond bur (9.18 m). The multi laminated carbide bur (7.88 m) did not differ from the diamond burs. The quality of the hybrid layer was equal to all preparation modes. Conclusion:The type of rotary instrument did influence the thickness of the hybrid layer for the resin cement studied, but did not affect the quality of it.

Evaluation of thickness of hybrid layer and length of resin tags of three adhesives to the root canal dentin: An in vitro scanning electron microscopic study

Objectives: This present study was done to evaluate the resin-dentin interface of three adhesive systems used for bonding the root canal under scanning electron microscopic (SEM). Materials and Methods: Sixty single-rooted human maxillary anterior teeth were decoronated at the cementoenamel junction apical preparation done up to 60 no. K-file and obturated with cold lateral compaction of gutta-percha and resin sealer (AH Plus). The specimens were then randomly divided into four groups of 15 teeth each. Group I-Etch and rinse adhesive system Group II-Self-etch adhesive system Group III-Resin modified glass ionomer adhesive system Group IV-No adhesive system used (control). All the adhesive systems were light cured then fiber posts were luted with dual cure resin cement and the specimens were prepared for SEM examination at magnifications ×1500 and ×5000 at coronal, middle and apical thirds of root canal. Results: Statistical analysis was performed using one-way ANOVA followed by post-hoc Tukey's honestly significant difference test. Group I showed highly statistical significant difference when compared with other groups. Conclusion: Maximum thickness of hybrid layer and long resin tags were shown by etch and rinse adhesives followed by self-etch adhesives.

Effect of Sodium Ascorbate on Dentin Bonding After Two Bleaching Techniques

The purpose of this study was to analyze the influence of 10% sodium ascorbate (SA) on the hybrid layer, resin tag length, and bond strength to dentin after bleaching. Six groups were tested: G C, control; G SA, sodium ascorbate (SA) + restoration; G CP, bleaching with carbamide peroxide (CP) + restoration; G CP+SA, bleaching with CP + SA+ restoration; G HP, bleaching with 35% hydrogen peroxide (HP) + restoration; and G HP+SA, HP + SA + restoration. After dental bleaching, the dentin was exposed and the antioxidant solution was applied to groups G SA, G CP+SA, and G HP+SA, before bonding procedures. The teeth were sectioned in the mesiodistal direction. One section was decalcified, and the specimens were embedded in paraffin and sectioned in the longitudinal direction with a thickness of 6 μm. Fifteen slices of each specimen were selected according to a systematic sample of slices with an interval proportional to the total number of slices obtained for each tooth. The specimens were stained using the Brown & Brenn method, and an optic microscope was used to analyze the hybrid layer thickness and resin tag length. The remaining tooth segment was sectioned into stick-shaped specimens and used for microtensile bond strength testing (0.5 mm/min). Statistical analysis was performed using two-way analysis of variance and Fisher test. The results for hybrid layer + tag formation (in micrometers) were G C, 13.27 Aa; G SA, 11.85 Ba; G CP, 6.84 Bb; G CP+SA, 9.02 Ab; G HP, 7.28 Bb; and G HP+SA, 9.22 Ab; bond strength results (in MPa) were G C, 49.5 Aa; G SA, 51.7 Aa; G CP, 37.16 Bb; G CP+SA, 47.69 Aa; G HP, 32.39 Ab; and G HP+SA, 39.67 Ab. Tooth bleaching with CP or HP impairs the formation of the hybrid layer and resin tags and reduces the microtensile bond strength. Statistically, the use of SA significantly increases the hybrid layer thickness and resin tag length. The microtensile bond strength values for carbamide peroxide increased, but the microtensile bond strength for hydrogen peroxide was not affected.