Thickness Of Hybrid Layer Research Articles

Morphological Analysis and Bond Strength to Root Canal Dentin of Endodontically Treated and Retreated Teeth: An Ex Vivo Study.

To assess the bond strength and the hybrid layer (HL) micro-morphological characteristics at the cement-dentin interface (CD-i) between root canal walls and two adhesive resin cements [self-etch (SERc) and self-adhesive (SARc)] in root-canal-treated (RCT) and naturally aged retreated teeth (RCR-T). Vital (n = 16) and RCT (n = 16) teeth were, respectively, endodontically treated or retreated. Fiber posts were luted either with SERc (Clearfil Universal Bond Quick + DC Core Plus) or SARc (iCEM). Samples were then sectioned into 1 mm thick slices perpendicular to the fiber post and submitted to push-out bond strength test. Vital (n = 4) and RCT (n = 4) first maxillary molars were also selected and prepared to evaluate CD-i morphology through confocal laser scanning microscopy (CLSM). Three-way analysis of variance (ANOVA) and Tukey post-hoc tests were assessed to statistically analyze the obtained data (p 0.05). Bond strength was significantly jeopardized in retreated teeth and in the root apical half, while the cements had no significant influence. Most failures occurred between dentin and resin cement. HL thickness was also hindered in retreated teeth. iCEM produced a thinner HL compared to SERc. Resin tag formation was significantly hampered in the root apical half. SARc performed as well as SERc on aged RCT radicular dentin. Clinicians can rely on simplified one-step luting systems when adhesion is required in unfavorable substrates such as the root canal post space of aged RCT teeth.

Fracture resistance and bonding performance after antioxidants pre-treatment in non-vital and bleached teeth.

This study aimed to evaluate the effect of antioxidant solutions on fracture strength and bonding performance in non-vital and bleached (38% hydrogen peroxide) teeth. One hundred and eighty dentin specimens were obtained, 60 for each test: fracture strength, hybrid layer thickness, and bond strength. The groups (n=10) were randomly composed according to post-bleaching protocol: REST - restoration, without bleaching; BL - bleaching + restoration; SA - bleaching, 10% sodium ascorbate solution, and restoration; AT - bleaching, 10% α-tocopherol solution, and restoration; CRAN - bleaching, 5% cranberry solution, and restoration; CAP - bleaching, 0.0025% capsaicin solution, and restoration. Data were analyzed with ANOVA, Kruskal-Wallis, Dunn, and Qui-Square tests (α=0.05). The highest fracture strength values were observed in REST (1508.96 ±148.15 N), without significant difference for the bleached groups (p>0.05), regardless of the antioxidant use. The hybrid layer thickness in the group that was not subjected to bleaching (REST) was significantly higher than in any other group. The bond strength in the bleached and antioxidants-treated groups (SA, AT, CRAN, CAP) has no differences with the bleached group without antioxidants (BL). Adhesive failures were predominant in the groups that did not receive the antioxidant application. In conclusion, the evaluated antioxidants did not show an effect on the fracture strength, hybrid layer thickness, or bond strength of dentin bleached after endodontic treatment. The application of 10% sodium ascorbate, 10% alpha-tocopherol, 5% cranberry, or 0.0025% capsaicin solutions is not an effective step and should not be considered for the restorative protocols after non-vital bleaching.

Evaluation of six different one-step universal adhesive systems in terms of dentin bond strength, adhesive interface characterization, surface tension, contact angle, degree of conversion and solvent evaporation after immediate and delayed use.

In this study, it was aimed to investigate the effects of different waiting periods on resin-dentin bond strength (BS), degree of conversion (DC), contact angle (CA), surface tension (ST), solvent evaporation (weight loss) and the characteristics of adhesive interfaces of the current six universal adhesive resins (ARs). A total of 216 caries-free human lower third molar teeth were used. Composite resin restorations were performed by applying six universal ARs in etch-and-rinse and self-etch mode on standardized dentin surfaces after 0, 5, and 30 min waiting time. Then, a micro-shear BS test, SEM examination and characterization of the adhesive interface were performed. In addition, DC, CA, ST, solvent evaporation of all tested ARs were evaluated. The obtained data were statistically anaIyzed. The tested ARs did not show any statistical difference between 0 and 5min evaluations in all parameters evaluated except for weight loss (p > 0.05). While the weight loss, ST and CA of all ARs increased in 30 min (p < 0.05), the BS, DC, thickness of the adhesive layer and the hybrid layer, resin tag length and number of resin tags varied according to the ARs used. When the ARs were used in etch-and-rinse mode, all the parameters evaluated also varied according to the AR used. Higher adhesive layer thickness and lower hybrid layer thickness were found in the self-etch mode (p < 0.05). All of the adhesives tested can be safely used up to 30 min. This could also prevent economical loss caused by waste adhesive material. It is important to know how the bond strength, degree of conversion, adhesion, contact angle and surface tension properties of the adhesive resin waiting in the dispensing cup for a long time during clinical use are affected to make ideal restorations.

Examination of caries‐affected dentin and composite‐resin interface after different caries removal methods: A scanning electron microscope study

To evaluate the caries-affected dentin and composite-resin interface with scanning electron microscopy (SEM) after different caries removal methods in human molars. Twelve with extensive approximal caries lesions that did not reach the pulp and five caries-free molars (control group [CG]) were used. Carious teeth were divided into four experimental groups: Atraumatic Restorative Treatment (ART), Rotary Instrument (RI), Photo-Ablation, and Papain-Based Enzymatic Gel (Brix 3000®, Brix, Brazil). Class II slot cavities were prepared with RI in the CG. Then all caries removed teeth and control groups were restored (All-Bond Universal, BISCO, USA; Clearfil MajestyES-2, Kuraray, Japan). Specimens were prepared for SEM examinations. Hybrid layer (HL) thicknesses were measured using ImageJ programme. Gap measurements were performed with micro-CT. Data were analyzed with ANOVA and posthoc Dunnett's t-tests (p <.05). The highest HL thickness was found in Photo-Ablation Group, and a statistically significant difference was observed among the control and experimental groups (p < .05). The lowest HL thickness was measured in the Enzymatic Gel Group. In terms of internal gap formation, CG showed statistically significant differences compared to the other groups (p < .05). The highest internal gap was observed in RI Group, while the lowest gap was observed in CG. According to SEM, a uniform HL and resin tags were seen in the CG. Smear layer, irregular HL, and gap formation were observed in ART Group. In RI Group, nonuniform HL formation and resin tags were observed. In Photo-Ablation Group, a uniform HL without smear layer and internal gap was observed. In the Enzymatic Gel Group, both opened dentinal tubules, and melting-like formations were observed on the dentin surface. Especially melting-like formations were observed in peritubular dentin. It can be concluded that all caries removal methods except rotary instrumentation were conservative methods, which preserve more healthy dental tissues. RESEARCH HIGHLIGHTS: Among the caries removal procedures, the photo-ablation caries removal method stands out with the highest hybrid layer (HL) thickness and the lowest internal gap formation. Despite having the lowest HL thickness, the enzymatic gel method can be advantageous for patients requesting an alternative caries removal instead of a rotary instrument.

Bonding effects of cleaning protocols and time-point of acid etching on dentin impregnated with endodontic sealer.

ObjectivesThis study aimed to investigate the bonding effects of cleaning protocols on dentin impregnated with endodontic sealer residues using ethanol (E) or xylol (X). The effects of dentin acid etching immediately (I) or 7 days (P) after cleaning were also evaluated. For bonding to dentin, universal adhesive (Scotchbond Universal; 3M ESPE) was used. The persistence of sealer residues, hybrid layer formation and microshear bond strength were the performed analysis.Materials and MethodsOne hundred and twenty bovine dentin specimens were allocated into 4 groups (n = 10): G1 (E+I); G2 (X+I); G3 (E+P); and G4 (X+P). The persistence of sealer residues was evaluated by SEM. Confocal laser scanning microscopy images were taken to measure the formed hybrid layer using the Image J program. For microshear bond strength, 4 resin composite cylinders were placed over the dentin after the cleaning protocols. ANOVA followed by Tukey test and Kruskal-Wallis followed by Dunn test were used for parametric and non-parametric data, respectively (α = 5%).ResultsG2 and G4 groups showed a lower persistence of residues (p < 0.05) and thicker hybrid layer than the other groups (p < 0.05). No bond strength differences among all groups were observed (p > 0.05).ConclusionsDentin cleaning using xylol, regardless of the time-point of acid etching, provided lower persistence of residues over the surface and thicker hybrid layer. However, the bond strength of the universal adhesive system in etch-and-rinse strategy was not influenced by the cleaning protocols or time-point of acid etching.

CLINICAL PROCEDURE OF IMMEDIATE DENTIN SEALING FOR INDIRECT BONDED RESTORATION

Immediate Dentin Sealing or pre-hybridization implies the application of resin adhesive to freshly cut dentin after teeth preparation, before impression. Immediate Dentin Sealing has been suggested as an alternative to the delayed dentin sealing (DDS), a technique in which resin adhesive is applied just before final bonding of indirect restorations. Immediate Dentin Sealing technique is universal i.e used in inlays, onlays, veneers, crowns and well documented clinically and experimentally. Various types of Dentin Bonding Agents are available on the market. Difference lies in the thickness of hybrid layer formed and the adhesive used.

Comparative Evaluation of Resin Dentin Interface using Universal and Total- Etch Adhesive Systems on Sound and Eroded Dentin: In Vitro Study.

Objective This study aimed to compare the resin-dentin interface of sound and eroded dentin using universal and total-etch adhesive systems. Materials and Methods Forty caries-free extracted human premolars were collected, and the occlusal surfaces were ground by using slow speed diamond disc with copious water supply until a flat superficial dentin was exposed. The test group underwent erosive cycle (n = 20), and another group (n = 20) was reserved for control group. Erosive protocol consisted of immersion in 1.23% citric acid for 1 minute every 12 hours and stored in artificial saliva. Both the control and eroded teeth were further subdivided (n = 10) for composite restoration by using either self-etch or total-etch systems. Then the tooth samples were sectioned longitudinally and observed under confocal laser scanning microscope at ×10 magnification to evaluate resin tag length and hybrid layer thickness. Statistical Analysis The data obtained were analyzed by using independent t-test. Results The highest mean value of the resin tag length and thickness of hybrid layer was observed with total-etch system in sound dentin group compared with other groups (p < 0.001). Conclusion The resin-dentin interface of sound dentin was found to be better than eroded dentin by using total-etch system. The resin-dentin interface of eroded dentin was superior to sound dentin by using self-etch adhesive system.

Phenolic extract of Libidibia ferrea inhibits dentin endogenous enzymatic activity depending on the adhesive system strategy

This study evaluated the influence of Libidibia ferrea (Lf) extract used as dentin pretreatment on the resin-dentin bond strength stability and dentin endogenous enzymatic activity. The phytochemical profile (PP) of the Lf extract was evaluated by liquid chromatography; particle size, polydispersity index (PdI), and zeta potential (ZP) were evaluated by dynamic light scattering. The tested groups were ER-Scotchbond Universal (SBU) in the etch-and-rinse (ER) mode; ERLf-SBU in the ER mode + Lf after etching; SE- SBU in the self-etch (SE) mode; and LfSE-Lf before SBU in the SE mode. Sticks were obtained for microtensile bond strength tests and failure mode (24 hr and 12 months). The hybrid layer was evaluated using scanning electron microscopy. The endogenous enzymatic activity of the underlying dentin was analyzed by in situ zymography with the same treatments. The PP showed the presence of quercetin (2.6% w/w). Lf particles were considered large after the analysis of the PdI. The ZP remained stable over time. The ER and ERLf groups had lower bond strength after 12 months, but SE and LfSE remained stable. The predominant failure mode was adhesive for both times. ER and ERLf had longer resin tags and a thicker hybrid layer. The ER and LfSE groups showed higher enzymatic activity than the ERLf and SE groups after 12 months. The Lf extract may contribute to inhibit the dentin endogenous enzymatic activity when associated with an adhesive system in the ER mode.

Effect of Thickness of Various Restorative Materials and Hybrid Layer on Stress Distribution of Direct Cervical Restorations of Teeth using a Three Dimensional Structural Finite Element Analysis

Simulation of effect of thickness of restorative materials and hybrid layer on stress distribution of direct cervical restorations is critical to evaluate the best option for a bi-layered restoration in the cervical cavity.

Microleakage and characteristics of resin-tooth tissues interface of a self-etch and an etch-and-rinse adhesive systems.

ObjectivesThis study was conducted to compare the microleakage and characteristics of the resin-tooth tissue interface between self-etch and etch-and-rinse adhesive systems after 48 hours and 3 months.Materials and Methods40 extracted premolar teeth were randomly divided into 2 groups: 1-step self-etch adhesive system – Optibond™ All-In-One, and 2-step etch-and-rinse adhesive system - Adper™ Single Bond 2. Both groups were subjected to 500 thermocycles (5°C–55°C) before scanning electron microscope (SEM) analysis or microleakage trial at 48-hour and 3-month time periods.ResultsSEM images showed the hybrid layer thickness, diameter, and length of resin tags of the self-etch adhesive (0.42 ± 0.14 µm; 1.49 ± 0.45 µm; 16.35 ± 14.26 µm) were smaller than those of the etch-and-rinse adhesive (4.39 ± 1.52 µm; 3.49 ± 1 µm; 52.81 ± 35.81 µm). In dentin, the microleakage scores of the 2 adhesives were not different in both time periods (48 hours/3 months). However, the microleakage score of etch-and-rinse adhesive increased significantly after 3 months (0.8 ± 0.63 and 1.9 ± 0.88, p < 0.05).ConclusionsThe self-etch adhesive exhibited better long-term sealing ability in dentin when compared to that of the etch-and-rinse adhesive. The greater hybrid layer thickness and dimensions of resin tags did not guarantee reliable, long-lasting sealing in the bonding area.

Hybrid Layer Thickness and Resin Tags Penetration of two Universal Adhesives Incorporated with Ascorbic Acid Coated Superparamagnetic Nanoparticles Subjected to External Magnetic Field

Hybrid Layer Thickness and Resin Tags Penetration of two Universal Adhesives Incorporated with Ascorbic Acid Coated Superparamagnetic Nanoparticles Subjected to External Magnetic Field

Experimental and Analytical Investigation of Hybrid Layer Thickness Effect on Replacing the Rebar for Reinforced Concrete Beams

Many researchers emphasize the effectiveness of steel fiber to replace the reinforcing bar in the reinforced concrete structural elements. The fiber of different types, sizes and geometries have been added to the concrete mix with a pozzolanic material to produce Ultra-High Strength Concrete (UHSC), which has excellent properties, high strength, and durability. This paper is a lab work and theoretical study consisting of casting and testing. Twenty-one simply supported RC beams to examine the beam's behavior and the shear capacity with the full or partial depth of UHSC with or without steel fibers (UHSSFRC) for replacing the reinforcing bars. The beams were divided into five groups. Preliminary experiments tests were conducted and carried out to study hardened properties of concrete such as (compressive strength, splitting tensile strength, modulus of rupture and modulus of elasticity). The selected finite element program (ANSYS) was applied to model all tested beams. It was observed that the performance of the finite element representation gives and shows good agreement with the lab work results. The test consists of failure load, deflection, cracks and failure mode. The experimental laboratory work results showed that for (1% steel fiber with reinforcement ratio ρ=0.0105 full UHSC layer) was able to give the same shear capacity for beam with (reinforcement ratio ρ=0.0157 regular concrete), while for (2% steel fiber half UHSC layer and reinforcement ratio ρ=0.0105) was able to give the same ultimate shear loads of beam with (reinforcement ratio ρ=0.0157 normal concrete). This research reveals that the hybrid layer and steel fiber effects were able to substitute for a higher reinforcement ratio with the same shear capacity.

Moist vs over-dried etched dentin: FE-SEM/TEM and bond strength evaluation of resin-dentin interfaces produced by universal adhesives.

To evaluate the influence of the degree of dentin moisture on interfacial ultramorphology and bond strength (μTBS) of universal adhesives. Futurabond U (FBU), Scotchbond Universal (SBU), Adhese Universal (ADU), and Prime&Bond active (PBA) were used. After acid-etching, moist or over-dried dentin surfaces were tested. Teeth were restored for scanning and transmission electron microscopy (n = 3) and μTBS evaluation (n = 5). μTBS results were analyzed by two-way ANOVA and Tukey. For moist dentin, a well-formed hybrid layer (HL) was observed. However, when applied to over-dried dentin, remarkable differences were observed. Defects, gaps, and reduced HL thickness were observed mainly for ADU and FBU. When applied to wet dentin, μTBS values were similar for all adhesives, except for FBU, which was significantly lower. When applied to over-dried dentin, PBA presented the highest μTBS values, followed by SBU, ADU, and FBU. ADU presented significantly lower μTBS when applied to over-dried dentin. PBA, SBU, and FBU μTBS values were not sensitive to the degree of moisture. Even though application to over-dried dentin revealed defects, gaps and reduced HL thickness for SBU, ADU, and FBU, μTBS analysis only revealed a significant reduction for ADU. Universal adhesives can be applied in either self-etching or etch-and-rinse mode. However, clinicians are not aware which universal adhesives should be strictly applied on a moist dentin for bonding in the etch-and-rinse mode.

Investigation of five α-hydroxy acids for enamel and dentin etching: Demineralization depth, resin adhesion and dentin enzymatic activity

ObjectivesSurface conditioning of enamel and dentin is a key step during adhesive restorative procedures and strategies. The aim of this study was to investigate the effectiveness of five α-hydroxy-acids (AHAs) as enamel and dentin surface etchants. MethodsEnamel and dentin specimens were prepared from human molars to determine the depth of demineralization by optical profilometry (Δz), the resin bond strength to enamel and dentin (μTBS), the micro-permeability of dentin–resin interfaces, and the gelatinolytic activity of dentin matrix induced by AHAs [glycolic (GA), lactic (LA), citric (CA), malic (MI) and tartaric (TA)] and controls [phosphoric (PA) and maleic (MA)]. All acids were prepared at 35% concentration. Adhesion studies employed Adper Single Bond Plus bonding system. Data were individually processed and analyzed by ANOVA, post-hoc tests and Pearson correlations (α = 0.05). ResultsAHA exhibited statistically lower depth of demineralization of enamel and dentin (average 4 fold) than controls (p < 0.001). In enamel, MA and PA etching resulted in higher μTBS than AHA groups (p < 0.001). In dentin, GA, TA, CI and LA etching resulted in statistically similar μTBS than PA (p < 0.05). The hybrid-layer (HL) thickness and interfacial micro-permeability intensity were statistically lower for AHA groups (p < 0.05). A significant positive correlation was observed between the intensity of micro-permeability and the thickness of HL (p < 0.05). AHA etchants elicited lower dentin enzymatic activity than controls (p < 0.05). SignificanceAHAs effectively etched enamel and dentin surfaces. In particular, GA and TA resulted in suitable μTBS and sealing ability as well as induced less gelatinolytic activity in dentin than PA and MA.

Shear bond strength to sound and caries-affected dentin of sim-plified “etch-and-rinse” and “self-etch” adhesives and the hybrid layer micromorphology

Background/Aim. After removal of caries-infected dentin, a considerable area of the cavity floor comprising caries- affected dentin. Bonding to caries-affected dentin is characterized by lower bound strength and inferior hybrid layer guality compared to bonding to sound dentin. The purpose of study was to compare shear bond strength (SBS) of currently available adhesive systems to sound dentin (SD) and caries-affected dentin (CAD) and elucidate the hybrid layer micromorphology. Methods. Sixty extracted human molars with coronal carious lesions formed the experimental sample while additional sixty extracted intact human molars (impacted third molars) served as controls. Identification of a carious-affected dentin was carried out using visual identification (North Carolina Dentin Sclerosis Scale). Teeth from both the experimental and the control sample were allocated to one of the following three groups: Adper Single Bond Plus/Filtek Supreme XT (ASB/FS) (3M ESPE), AdheSE One/Tetric EvoCeram (AO/TEC) (IvoclarVivadent), and Prime&amp;Bond NT/CeramX Mono (PB/CXM) (Dentsply). Bonding procedures utilized in this work were in line with the manufacturers? instructions. The SBS was measured using a universal testing apparatus. Hybrid layer micromorphology was observed under scanning electron microscope (SEM). The mean SBS values (MPa), and hybrid layer thickness (in ?m) were statistically analyzed using the t-test, Mann-Whitney U-test, ANOVA, and Holm?s test. Results. Mean SBS ? standard deviation were: ASB/FS to SD = 10.56 ? 3.49; ASB/FS to CAD = 10.06 ? 2.55; AO/TEC to SD = 7.01 ? 2.05; AO/TEC to CAD = 6.73 ? 1.66; PB/CXM to SD = 9.01 ? 2.47; PB/CXM to CAD = 7.83 ? 1.42. A statistically significant difference was found between the bonding strength of ASB/FS and AO/TEC to both SD and CAD, and between ASB/FS and PB/CXM to CAD. Hybrid layer thickness was statistically significantly greater for ASB/FS than for PB/CXM. For the ASB/FS system, a statistically significantly thicker hybrid layer was formed on CAD than on SD. No hybrid layer could be observed for AO/TEC. Conclusion. All tested compsite systems bond equally well on sound and caries-affected dentin. The etch-and-rinse adhesives achieved stronger bond strengths. The Adper single Bond Plus-Filtek Supreme XT system formed a statistically significantly thicker hybrid layer on both type 1 of dentin than the Primu 8 Bond NT-CeramX Mono system.

Tailoring electroluminescence characteristics with enhanced electron injection efficiency in organic light emitting diodes by doping engineering

In present work, by employing doping engineering, we demonstrate a new type of organic light-emitting diodes (OLEDs) constructed by novel hybrid electron-injecting and electron-transporting layers (EITL) with cadmium sulfide (CdS) and Alq3 as buffer active materials. Our developed OLEDs exhibit highly effective electron injection from cathode to organic layers. Simultaneously, the driving voltage is significantly reduced with Alq3/Alq3 doped CdS hybrid EITL structure. Importantly, equipped with 60 nm constant thickness of hybrid layer, the device with 15 nm-thickness of Alq3 doped CdS exhibit improved performance than the others with the maximum luminance and the maximum of current efficiency 32340 cd/m2 at 12 V and 5.92 cd/A at 11.5 V, respectively, with the CIE coordinates almost nearby (0.33, 0.56). And at the current density of 200 cd/m2, the current efficiency of the device with EITL was 5.18 cd/A, improved 31% than that of the device non-doped CdS. Such enhanced improvements are attributed to the injection of photo-generated electrons produced by CdS which absorbed the light waves. Our systematic studies and complementary engineering investigations upon highly efficient hybrid OLEDs open new opportunities for innovative applications with optimized integration among performance, dimension and cost in a variety of solid-state lighting field applications, e.g., digital displays, portable systems, smart wearable devices and human–machine interfaces.

Medición de la capa híbrida resultante del uso de cementos autograbadores de uno y dos pasos

Antecedentes: La formación de la capa híbrida debe ser proporcional a la capacidad de los cementos para retener con éxito postes de fibra de vidrio en el interior del conducto preparado endodónticamente. Objetivo: Medir el espesor de la capa híbrida en los tercios coronal y apical as usar cementos autograbadores de uno y dos pasos. Métodos: Se realizó un estudio experimental con 30 premolares humanos que se trataron endodónticamente y se asignaron a tres grupos. Se cementaron postes de fibra de vidrio con tres cementos siguiendo las instrucciones de los fabricantes. Se realizaron cortes coronales y apicales y se cuantificó el grosor de la capa híbrida por microscopía electrónica de barrido. Los datos se analizaron con las pruebas estadísticas H de Kruskal-Wallis y U de Mann-Whitney (p&lt;0,05). Resultados: El promedio del grosor de la capa híbrida fue de 0,74 mm con Multilink N® (grupo 1), 0,24 mm con RelyX Ultimate® (grupo 2) y 0,03 mm con RelyX U200® (grupo 3) (p = 0,0092). Los promedios en los tercios coronal y apical fueron: 1,29 mm y 0,19 mm para el grupo 1; 0,33 mm y 0,14 mm para el grupo 2 y 0,26 mm y 0,23 mm para el grupo 3, diferencias que fueron estadísticamente significativas (p = 0,043). Conclusiones: El espesor de la capa híbrida formada con el uso de los cementos de dos pasos fue mayor que con el cemento de un solo paso, especialmente en la porción coronal.

Qualitative evaluation of hybrid layer formation using Er:YAG laser in QSP mode for tooth cavity preparations.

The purpose of this study was to evaluate the thickness and qualitative characteristics of the hybrid layer after two cavity preparation methods, using Er:YAG laser in QSP mode and conventional carbide burs. Additionally, two different adhesive techniques were investigated using etch-and-rinse and self-etch adhesive systems. Sixty sound human third molars were used and were randomly divided into four groups (n = 15). In the first two groups, large (4mm length, 3mm wide, and 3mm deep) class I cavities were prepared using Er:YAG laser (2.94μm) in QSP mode, while in the other two groups, the cavities were prepared using carbide burs. After cavity preparations, two different adhesive techniques with GLUMA® 2 Bond (etch-and-rinse) and Clearfil™ Universal Bond Quick (self-etch) were applied. For the qualitative evaluation of the formed hybrid layer, photomicrographs were taken using SEM, and elemental semi-quantitative analysis was performed using EDS to confirm the extent of the hybrid layer. One-way ANOVA was applied to verify the existence of statistically significant differences, followed by Tukey test for post hoc comparisons (Bonferroni corrected), and the level of significance was set at a = 0.05. The laser-treated groups exhibited higher hybrid layer thickness than bur-treated groups (p < 0.001). Between the laser-treated groups, etch-and-rinse technique presented higher hybrid layer thickness than self-etch technique (p < 0.001), while between the bur-treated groups, no significant differences were detected (p = 0.366). Er:YAG laser cavity preparations in QSP mode may be advantageous for adhesion of composite restorations, but more data are necessary to confirm its clinical effectiveness.

Calibration of a lactic-acid model for simulating biofilm-induced degradation of the dentin-composite interface

ObjectiveTo verify and calibrate a chemical model for simulating the degradation of the dentin-composite interface induced by multi-species oral biofilms in vitro. MethodsDentin-composite disks (5-mm dia.×2-mm thick) were made from bovine incisor roots and filled with either Z100™ (Z100) or Filtek™ LS (LS) composite. The disks, which were covered with nail varnish, but with one of the dentin-composite margins exposed, were immersed in lactic acid solution at pH 4.5 for up to 48h. Diametral compression was performed to measure the reduction in bond strength of the dentin-composite disks following acid challenge. Scanning electron microscopy (SEM) was used to examine decalcification of dentin and fracture modes of the disks. To better understand the degradation process, micro-computed tomography, in combination with a radiopaque dye (AgNO3), was used to assess interfacial leakage in 3D longitudinally, while SEM was used to determine the path of leakage. One-way analysis of variance (ANOVA) was used to analyze the results, with the level of statistical significance set at p<0.05. The results were compared with those obtained previously using multi-species biofilms for verification and calibration purposes. ResultsAfter 48h of acid challenge, the debonding load of both the LS- and Z100-filled disks reduced significantly (p<0.05). In the Z100-filled disks, debonding mostly occurred at the adhesive-dentin interface, while in the LS-filled disks, this happened at the adhesive-composite interface, instead. The degree of dentin demineralization, the reduction in debonding load and the modes of failure observed were very similar to those induced by multi-species oral biofilms found in the previous work. Leakage of AgNO3 occurred mainly along the hybrid layer. The specimens filled with Z100 had a thicker hybrid layer (∼6.5μm), which exhibited more interfacial leakage than those filled with LS. SignificanceThe chemical model with lactic acid used in this study can induce degradation to the dentin-composite interface similar to those produced by multi-species biofilms. With appropriate calibration, this could provide an effective in vitro method for ageing composite restorations in assessing their potential clinical performance.

MICROTENSILE BOND STRENGTH AND NANOLEAKAGE OF A RESIN COMPOSITE BONDED TO DENTIN TREATED WITH GALLA CHINENSIS EXTRACT

Aim: This in vitro study aimed to evaluate the effect of dentin surface-treatment with 4mg/ml Galla Chinensis Extract (GCE) on microtensile bond strength and nanoleakage of a resin composite restoration, subjected to two different water storage periods.Materials and Methods: A total of thirty freshly extracted sound human molars were prepared and sliced coronally for application of a nanohybrid resin composite restorative material (Filtek Z350 XT). Exposed dentin surfaces, were acid-etched, to be either routinely covered by adhesive and resin composite, or treated with 4mg/ml Galla Chinensis Extract, followed by application of an adhesive and a resin composite. Treated teeth were divided into 3 subgroups according to time of assessment of their microtensile bond strength and nanoleakage after 24 hours, 3 months and 6 months of water storage.Data were statistically analyzed with One-way ANOVA at 95% confidence interval. Kolmogorov Smirnov and Shapiro-Wilk tests were applied for normality testing. Independent t-test was used to compare between different groups for different water storage periods.Results: Insignificantly different microtensile bond strength values between control and surface-treated teeth were recorded for the resin composite material immediately and after 3 months water storage periods. Lowest values were recorded after 6 months storage period, differing significantly (p ≤0.001) between control and surface-treated dentin group. The immediately tested control group revealed significantly the highest mean microtensile bond strength values (32.1±7.84 MPa) compared to both other control groups at different storage periods. SEM micrographs showed extensive silver deposition throughout the entire hybrid layer thickness of silver-impregnated sections at resin/dentin interfaces after 6 months aging period. These depositions penetrated into dentinal tubules and around the resin tags in the control group.Conclusions: Surface treatment of etched dentin with 4mg/ml Galla Chinensis Extract improved resistance of bonded resin composite restorations to hydrolysis in terms of improved microtensile bond strength and nanoleakage after 3and 6 months of water storage.