Ultra-structure characterization of self-etching treated cementum surfaces

Objectives: to evaluate the effect of different conditioning treatments on surface roughness and topography of dental cementum. Study Design: Extracted human canines were used for the present study. The mesial surface from the cervical third of the roots were ground flat with wet 600-grit silicon carbide paper. They were polished (up to 1/4 µm diamond paste) and treated as follows: 1) No treatment, 2) 35% H3PO4 during 15 s, 3) Clearfil SE Bond primer (SEB), 4) One-Up Bond F (OUB). The adhesive systems were applied following manufacturer?s instructions. SEB primer and OUB were removed from surfaces by washing and ultrasonic agitation with ascending ethanol solutions. Digital images of treated surfaces (5x5 and 15x15 µm) were obtained by means of an atomic force microscope (AFM) analysis. The average surface roughness (Ra nanometers) of the scanned areas was assessed. Data were analyzed by ANOVA and SNK multiple comparisons tests (p<0.05). Results: phosphoric acid treatment produced the highest mean roughness value, at all scan sizes. At 5x5 µm AFM images, for self-etch adhesive systems no differences in roughness were detected. At 15x15 µm, when One-Up Bond F was employed the lowest value was obtained. Conclusions: When phosphoric acid treatment was applied, cementum surface roughness increased and a strong demineralization with exposed collagen fibers could be observed

Biomimetic Remineralization of an Extracellular Matrix Collagen Membrane for Bone Regeneration

Natural extracellular matrix (ECM) collagen membranes are frequently used for bone regeneration procedures. Some disadvantages, such as rapid degradation and questionable mechanical properties, limit their clinical use. These membranes have a heterologous origin and may proceed from different tissues. Biomineralization is a process in which hydroxyapatite deposits mainly in collagen fibrils of the matrices. However, when this deposition occurs on the ECM, its mechanical properties are increased, facilitating bone regeneration. The objective of the present research is to ascertain if different membranes from distinct origins may undergo biomineralization. Nanomechanical properties, scanning electron (SEM) and multiphoton (MP) microscopy imaging were performed in three commercially available ECMs before and after immersion in simulated body fluid solution for 7 and 21 d. The matrices coming from porcine dermis increased their nanomechanical properties and they showed considerable mineralization after 21 d, as observed in structural changes detected through SEM and MP microscopy. It is hypothesized that the more abundant crosslinking andMinistry of Economy and CompetitivenessEuropean Commission PID2020-114694RB-I00 PID2020-113919RB-I00Ministry of Universities FPU20/0045

Wetting ability of an acetone/based etch rinse adhesive after NaOCl-treatment

Objectives: to evaluate the effect of sodium hypochlorite (NaOCl) treatment on surface dentin roughness (Ra) and contact angle (CA) when using Prime and Bond NT adhesive (PB NT). Study Design: Extracted human third molars were sectioned to expose flat, superficial and deep dentin surfaces. CA and Ra were measured (1) before and (2) after 35% H 3 PO 4 etching, and (3) H 3 PO 4 etching + 5% NaOCl treated for 2 minutes before the application of PB NT. CA was measured by the Axisymmetric Drop Shape Analysis Technique using distilled and deionized water and PB NT. Roughness was evaluated with a profilometer, twelve radial measurements were performed in each treatment surface. Data were analyzed with two-way ANOVA and Newman-Keuls multiple comparison test procedures. Results: CA values decreased after acid etching and even more after NaOCl treatment on deep dentin when water was tested. With resin, there were not differences on CA results after H 3 PO 4 neither after NaOCl treatment, in both dentin surfaces. Etching and NaOCl treatment resulted in surface roughness increase. Conclusions: In spite of the higher roughness after NaOCl treatment on superficial and deep dentin, the use of 5% NaOCl for 2 min after dentin demineralization when PB NT was employed did not improved the wettability of dentin, probably due to nanofiller content and/or hydrogen-bonding interactions with residues of the organic matrix on collagen-depleted denti

Bonding efficacy of an acetone/based etch-and-rinse adhesive after dentin deproteinization

Objectives: to evaluate the effect of sodium hypochlorite (NaOCl) treatment on dentin bonding by means of shear bond strength (SBS) measurements when using Prime and Bond NT (PB NT) adhesive. Ultrastructure of the interfaces was examined by scanning electron microscopy (SEM). Study design: Extracted human third molars were sectioned and ground to expose flat surfaces of superficial or deep dentin. Specimens were randomly assigned to two equal groups, and bonded as follows: (1) according to the manufacturers? directions, after 35% H 3 PO 4 etching, (2) 5% NaOCl treated for 2 minutes, after 35% H 3 PO 4 etching. Each sample was embedded in a Watanabe shear test assembly for a single plane lap shear. After PB NT bonding, specimens were stored in water for 24 h at 37ºC and thermocycled (500x). Samples were tested in shear to failure using a universal testing machine at 0.75 mm/ min. Data were analyzed with ANOVA and Newman-Keuls multiple comparison test procedures. Two samples of each group were randomly selected to investigate the morphologic aspect of the resin/dentin interface with SEM. Results: After etching and after aqueous sodium hypochlorite (NaOCl aq ) application, SBS values were similar on superficial than deep dentin (p>0.05). SEM findings shows for H 3 PO 4 etching conditioned samples a detectable hybrid layer and long resin tags; for NaOCl treated specimens, it may be observed a non apparent hybrid layer, and the adhesive contact directly with the neck of the cylindrical resin tags. Conclusions: The use of 5% NaOCl for 2 min after dentin demineralization when PB NT was employed did not improve the bond strength to dentin, probably due to nanofiller content and/or oxidative changes on collagen-depleted denti

Assessing bone quality through mechanical properties in postmenopausal trabecular bone.

Background: The inner structure of trabecular bone is a result of structural optimisation provided by remodeling processes. Changes in hormonal status related to menopause cause bone tissue loss and micro-architectural deterioration with a consequent susceptibility to fracture. Accumulation of micro-damage in bone, as a function of the rate of production and rate of repair, underlies the development of stress fractures, increasing fragility associated to age and osteoporosis, especially in transmenopausal women. Patients and Methods: Quasi-static and nano-dynamic mechanical characterisation were undertaken in trabecular bone from femoral neck biopsies of postmenopausal women. AFM complementary studies were performed to determine nano-roughness (SRa) and the fibrils width of collagen. Nanoindentations were used to quantify transmenopausal changes in intrinsic mechanical properties of trabecular bone: hardness (Hi), modulus of Young (Ei), complex modulus (E*), tan delta (δ), storage modulus (E') and loss modulus (E"). Results: As result of the quasi-static measurements, 0.149 (0.036) GPa and 2.95 (0.73) GPa of Hi and Ei were obtained, respectively. As result of the nano-dynamic measurements, 17.94 (3.15), 0.62 (0.10), 13.79 (3.21 and 6.39 (1.28) GPa of E*, tan (δ), E' and E" were achieved, respectively. 101.07 SRa and 831.28 nm of fibrils width were additionally obtained. Conclusion: This study poses a first approach to the measurement of bone quality in postmenopausal trabecular bone by combining quasistatic, nano-DMA analysis and tribology of dentin surface through AFM characterizationProject MAT2017-85999-P supported by the Ministry of Economy and Competitiveness (MINECO) and European Regional Development Fund (FEDER)

Novel Pastes Containing Polymeric Nanoparticles for Dentin Hypersensitivity Treatment: An In Vitro Study

Tubule occlusion and remineralization are considered the two main goals of dentin hypersensitivity treatment. The objective is to assess the ability of dentifrices containing zinc-doped polymeric nanoparticles (NPs) to enduringly occlude the dentinal tubules, reinforcing dentin’s mechanical properties. Fifteen dentin surfaces were acid-treated for dentinal tubule exposure and brushed with (1) distilled water, or with experimental pastes containing (2) 1% of zinc-doped NPs, (3) 5% of zinc-doped NPs, (4) 10% of zinc-doped NPs or (5) Sensodyne®. Topographical and nanomechanical analyses were performed on treated dentin surfaces and after a citric acid challenge. ANOVA and Student–Newman–Keuls tests were used (p < 0.05). The main results indicate that all pastes produced tubule occlusion (100%) and reinforced mechanical properties of intertubular dentin (complex modulus was above 75 GPa). After the citric acid challenge, only those pastes containing zinc-doped NPs were able to maintain tubular occlusion, as specimens treated with Sensodyne® have around 30% of tubules opened. Mechanical properties were maintained for dentin treated with Zn-doped NPs, but in the case of specimens treated with Sensodyne®, complex modulus values were reduced below 50 GPa. It may be concluded that zinc-doped NPs at the lowest tested concentration produced acid-resistant tubular occlusion and increased the mechanical properties of dentin.Ministry of Economy and Competitiveness (MINECO) and European Regional Development Fund (FEDER), grant number PID2020-114694RB-I00 MINECO/AEI/ FEDER/UELaboratorios KIN® fabricated and provided tested experimental pastes loaded with Zn-doped NP

Resistance to bond degradation between dual-cure resin cements and pre-treated sintered CAD-CAM dental ceramics

Objective: To evaluate the bond stability of resin cements when luted to glass-reinforced alumina and zirconia CAD/CAM dental ceramics. Study design: Eighteen glass-infiltrated alumina and eighteen densely sintered zirconia blocks were randomly conditioned as follows: Group 1: No treatment; Group 2: Sandblasting (125 µm Al2O3-particles); and Group 3: Silica-coating (50 µm silica-modified Al2O3-particles). Composite samples were randomly bonded to the pre-treated ceramic surfaces using different resin cements: Subgroup 1: Clearfil Esthetic Cement (CEC); Subgroup 2: RelyX Unicem (RXU); and Subgroup 3: Calibra (CAL). After 24 h, bonded specimens were cut into 1 ± 0.1 mm2 sticks. One-half of the beams were tested for microtensile bond strength (MTBS). The remaining one-half was immersed in 10 % NaOCl aqueous solution (NaOClaq) for 5 h before testing. The fracture pattern and morphology of the debonded surfaces were assessed with a field emission gun scanning electron microscope (FEG-SEM). A multiple ANOVA was conducted to analyze the contributions of ceramic composition, surface treatment, resin cement type, and chemical challenging to MTBS. The Tukey test was run for multiple comparisons (p < 0.05). Results: After 24 h, CEC luted to pre-treated zirconia achieved the highest MTBS. Using RXU, alumina and zirconia registered comparable MTBS. CAL failed prematurely, except when luted to sandblasted zirconia. After NaOClaq storage, CEC significantly lowered MTBS when luted to zirconia or alumina. RXU decreased MTBS only when bonded to silica-coated alumina. CAL recorded 100 % of pre-testing failures. Micromorphological alterations were evident after NaOClaq immersion. Conclusions: Resin-ceramic interfacial longevity depended on cement selection rather than on surface pre-treatments. The MDP-containing and the self-adhesive resin cements were both suitable for luting CAD/CAM ceramics. Despite both cements being prone to degradation, RXU luted to zirconia or untreated or sandblasted alumina showed the most stable interfaces. CAL experimented spontaneous debonding in all tested groups. Key words:CAD/CAM ceramic, alumina, zirconia, resin cement, surface pre-treatment, sandblasting, silica-coating, chemical aging, bond degradation, microtensile bond strength

El retiro de confianza como causal de despido arbitrario en los servidores y funcionarios públicos, 2019

El presente informe, está basado en una investigación cualitativa donde se analizará y establecerá una posición sobre el despido injustificado como un estándar para la protección de los derechos de los trabajadores de confianza que finalmente se logra retirar la confianza para hacer una recomendación para que nuestro sistema legal pueda considerar conclusiones en estos casos, igualmente respetar los derechos del trabajador y su empleador. Es por medio de estas categorías emitidas, se provisionó una problemática bastante preocupante dentro del sector estatal, y es así como se tiene en particular los casos a estudiar, las cuales son el Exp. N° 03252-2011-PA/TC y el Exp. N° 03926-2007-PAlTC, por lo que como objetivo general se planteó identificar los criterios que existen con relación al retiro de confianza como causa de despido arbitrario en los servidores y funcionarios públicos, 2019. La metodología utilizada se ha basado en la recolección de datos, tanto como las entrevistas realizadas a servidores públicos de la Municipalidad Distrital de Acochaca, así como a especialistas legales de derecho laboral y en gestión pública y la guía de análisis documental recabada durante todo el proceso de proyección del presente informe, para lo cual se ha podido apreciar que el retiro de confianza sí podría considerarse como causa justa de despido arbitrario y esto conllevaría tras alguna falta grave realizada por el trabajador hacia la entidad pública donde se le contrató por sus habilidades y experiencias

Nanoscopic dynamic mechanical analysis of resin-infiltrated dentine, under in vitro chewing and bruxism events

The aim of this study was to evaluate the induced changes in mechanical behavior and bonding capability of resin–infiltrated dentine interfaces, after application of mechanical stimuli. Dentine surfaces were subjected to partial demineralization through 37% phosphoric acid etching followed by the application of an etch-and-rinse dentine adhesive, Single Bond (3M/ESPE). Bonded interfaces were stored in simulated body fluid during 24 h, and then tested or submitted to the mechanical loading challenge. Different loading waveforms were applied: No cycling (I), 24 h cycled in sine (II) or square (III) waves, sustained loading held for 24 h (IV) or sustained loading held for 72 h (V). Microtensile bond strength (MTBS) was assessed for the different groups. Debonded dentine surfaces were studied by field emission scanning electron microscopy (FESEM). At the resin–dentine interface, both the hybrid layer (HL) and the bottom of the hybrid layer (BHL), and both peritubular and intertubular were evaluated using a nanoindenter in scanning mode. The load and displacement responses were used to perform the nano-Dynamic Mechanical analysis and to estimate the complex and storage modulus. Dye assisted Confocal Microscopy Evaluation was used to assess sealing ability. Load cycling increased the percentage of adhesive failures in all groups. Specimens load cycled in held 24 h attained the highest complex and storage moduli at HL and BHL. The storage modulus was maximum in specimens load cycled in held 24 h at peritubular dentine, and the lowest values were attained at intertubular dentine. The storage modulus increased in all mechanical tests, at peritubular dentine. An absence of micropermeability and nanoleakage after loading in sine and square waveforms were encountered. Porosity of the resin–dentine interface was observed when specimens were load cycled in held 72 h. Areas of combined sealing and permeability were discovered at the interface of specimens load cycled in held 24 h. Crack-bridging images appeared in samples load cycled with sine waveform, after FESEM examination.This work was supported by grants MINECO/FEDER MAT2014-52036-P and FIS2013-41821-R

SEM and AFM characterization of surface of two RMGICs for degradation before and after modification with bioactive glass ceramic

“This is an Accepted Manuscript of an article published by Taylor & Francis Group in Journal of Adhesion Science and Technology on 09/12/2015, available online: http://www.tandfonline.com/10.1080/01694243.2015.1115603."Objectives: The aim of this study was to evaluate the effect of bioactive glass–ceramic particles (Biosilicate®) addition on surface nanoroughness and topography of Resin-modified glass ionomer cements (RMGICs).Methods: Experimental materials were made by incorporating 2 wt% of Biosilicate® into Fuji II LC® (FL) and Vitremer® (VT) powders. Disks of RMGICs (with and without Biosilicate®) measuring 0.5 cm (diameter) × 0.5 mm (thickness) were fabricated and polished. Samples were stored at 37 °C in dry or immersed in distilled water for 30 days. Digital images (20 × 20 μm) from the surfaces were obtained by means of an atomic force microscopy. Three images were acquired for each sample, and four nanoroughness measurements were performed in each image. Nanoroughness (Ra, nm) was assessed by Nanoscope Software V7. Data were analyzed with ANOVA and Student–Newman–Keuls multiple comparisons (p < 0.05). SEM images were obtained for surface topography analysis.Results: FL was significantly rougher than VT (p < 0.05) in wet and dry conditions. The addition of Biosilicate® increased the surface roughness in VT and decreased in FL, regardless of the storage media (p ≤ 0.05). No differences existed between materials and storage conditions after Biosilicate® addition. Significance: The Biosilicate® particles addition produced changes on the surface nanoroughness of the RMGICs. These changes depended on the particles size of the original cements in dry conditions. In water storage, dissolution of the Biosilicate® particles, a silica-rich gel formation, and a hydroxyl carbonate apatite precipitation on the surface of the materials changed the nanoroughness surface. FL was the roughest in both conditions.Significance: The Biosilicate® particles addition produced changes on the surface nanoroughness of the RMGICs. These changes depended on the particles size of the original cements in dry conditions. In water storage, dissolution of the Biosilicate® particles, a silica-rich gel formation, and a hydroxyl carbonate apatite precipitation on the surface of the materials changed the nanoroughness surface. FL was the roughest in both conditions.MINECO/FEDERMAT2014-52036-P