Impact of Calcium-Hydroxide, Sodium Ascorbate, and Sodium Thiosulphate on Bond Strength of Composite Restorations to Bleached Dentin.

This study evaluated the impact of using calcium-hydroxide or the antioxidant agents on the bond strength of adhesive restorations to bleached dentin. Forty teeth were prepared and allocated into 8 groups according to the surface treatment after bleaching (application or not of calcium hydroxide, 10% sodium ascorbate and 5% sodium thiosulphate for 10min), and the time of final restoration (immediate or after 7-days). Sodium perborate with 20% hydrogen peroxide was applied for 3 weeks using a developed artificial pulp chamber, with replacement every week. Composite resin restoration was performed and microtensile test was performed. Then, specimens were analyzed using a stereomicroscope and SEM. Data was submitted to Kruskal-Wallis and Dunn tests (p<0.05). The bond strength of non-bleached teeth was similar to the groups restored after 7 days of bleaching (p<0.05). The lowest values of bond strength were showed by groups restored immediately after bleaching (p<0.05). In all groups, there was a considerable predominance of adhesive fractures. Delaying the final restoration of teeth submitted to nonvital bleaching for 7 days permits an increase in bond strength. The immediate restoration of bleached teeth after the use of 10% sodium ascorbate or 5% sodium thiosulfate for 10 minutes showed unsatisfactory results. Clinical relevance Irrespective of the dentin protocol applied before adhesion, a satisfactory and an unsatisfactory result of bond strength values will be obtained delaying the final restoration or immediately performing the final restoration, respectively. Therefore, after nonvital tooth bleaching, clinicians should always delay the final restoration for a minimum period of 7 days.

Investigating the origin of laser-induced fluorescence in mannan-rich Phytelephas macrocarpa seeds before and after thermal aging.

Natural polysaccharides, e.g., starch, cellulose and sodium alginate have been highlighted as unconventional chromophores owing to their chain structures containing clustered electron-rich groups and the rigidification imposed by inter/intramolecular interactions. On account of the abundant hydroxyl groups and dense packing of low-substituted (< 5 %) mannan chains, we have investigated the laser-induced fluorescence of mannan-rich vegetable ivory seeds (Phytelephas macrocarpa), both in the native state and after thermal aging. The untreated material emitted fluorescence at 580 nm (yellow-orange) when excited at 532 nm (green). This luminescence is intrinsic to the polysaccharide matrix abundant in crystalline homomannan, as demonstrated by lignocellulosic analyses, fluorescence microscopy, NMR, Raman, FTIR and XRD. Thermal aging at 140 °C and above intensified the yellow-orange fluorescence and caused the material to fluoresce when excited by a near-infrared laser (785 nm). In view of the clustering-triggered emission mechanism, the fluorescence of the untreated material can be attributed to hydroxyl clusters and the conformational rigidification in mannan I crystals. On the other hand, thermal aging caused dehydration and oxidative degradation of mannan chains, inducing the substitution of hydroxyl groups by carbonyls. These physicochemical changes may have affected cluster formation and increased conformational rigidification, enhancing fluorescence emission.

Dentine biomodification by sulphonamides pre-treatment: bond strength, proteolytic inhibition, and antimicrobial activity.

We evaluated the effects of dentine biomodification after pre-treatment with two sulphonamide carbonic anhydrase inhibitors (CAIs) of the N-[4-sulphamoylphenethylcarbamoyl]benzenesulphonamide type, investigating matrix metalloproteases activity, resin-dentine micro tensile bond strength, dentine surface wettability, and antimicrobial activities. Ninety-five sound-extracted human molars were selected for the study. Inhibitory effects were evaluated by gelatinase and collagenase activity tests and collagen degradation FT-IR spectroscopic analysis. Pre-treatment with the two CAIs kept the micro tensile values after 12 months of storage (32.23 ± 5.95) and cariogenic challenge (34.13 ± 2.71) similar to the initial, pre-treatment values (33.56 ± 4.34). A decreased Streptococcus mutans biofilm formation on dentine surfaces and antibacterial activity against planktonic bacteria were observed after CAI treatment. Dentine pre-treatment with sulphonamide CAIs maintained adhesion strength stability, allowed better dentine wettability, maintained matrix collagen, and showed anti-S. mutans activity.

Effects of Two In-Office Bleaching Agents with Different Compositions on the Bond Strength to Enamel.

This study evaluates the effect of two in-office bleaching agents with different compositions on the bond strength to enamel surface. Fifty bovine teeth were divided into five groups (n = 10 teeth per group), according to the bleaching agent used and the time elapsed to perform the restorative procedures: restorative procedures performed without bleaching (control group); bleaching with 35% hydrogen peroxide (HP), with restorative procedures 24 hours or 7 days after bleaching (HP/24h and HP/7d groups, respectively); and bleaching with 35% HP with calcium compost, with restorative procedures 24 hours or 7 days after bleaching (HP AutoMixx/24h and HP AutoMixx/7d groups, respectively). The specimens were stored at 37°C in artificial saliva. Restored teeth were submitted to a micro-shear bond strength test. The specimens were analyzed using a stereoscope to determine the fracture pattern, classified as adhesive, cohesive, or mixed. The results of the bond strength test were evaluated by analysis of variance, with significance set at P < .05. The groups showed similar bond strength values without significant difference among them (P > .05). There was a predominance of the adhesive-type fracture pattern in all groups. The bleaching agents with different compositions showed similar bond strength values when the restoration was performed 24 hours and 7 days after bleaching, and the results were similar to the control group.

Effect of cementation delay on bonding of self-adhesive resin cement to yttria-stabilized tetragonal zirconia polycrystal ceramic treated with nonthermal argon plasma.

STATEMENT OF PROBLEM: Nonthermal argon plasma (NTAP) has been reported to improve the bond strength of resin cements to yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramics. However, the effect of the inevitable delay before cementation and after treating Y-TZP ceramics with NTAP is unclear. PURPOSE: The purpose of this in vitro study was to investigate whether delays of 8, 12, and 24 hours between the Y-TZP ceramic treatment with NTAP and the cementation would affect the surface energy and the bond strength of a self-adhesive resin cement to Y-TZP ceramic. MATERIAL AND METHODS: Sixty plates and 50 blocks of 3Y-TZP ceramic were divided into 2 groups (n=30 and n=25): as-sintered (AS) and airborne-particle abraded with 50-µm Al2O3 (APA). These groups were further divided into 5 subgroups (n=6 and n=5) according to the delay between the NTAP treatment and the measurement of surface energy and microtensile bond strength (µTBS) evaluation: (0, 8, 12, and 24 hours). For both 3Y-TZP surface conditions (AS and APA), a control group without NTAP treatment was used (ASC and APAC). The surface energy (SE) was evaluated with a goniometer and the 3Y-TZP elemental composition with X-ray photoelectron spectroscopy (XPS). For the µTBS test, the 3Y-TZP ceramic blocks were cemented to composite resin blocks with a self-adhesive resin cement. After storage in distilled water at 37 °C for 24 hours, the 3Y-TZP-composite resin blocks were sectioned into beams and submitted to a µTBS test. Data were submitted to 2-way ANOVA and the Tukey HSD test (α=.05). RESULTS: For the AS group, NTAP increased the SE irrespective of the delay before measurement: ASC<0 hour=8 hours=12 hours=24 hours (P<.05). For the APA group, except after 12 hours, NTAP also increased the surface energy (P<.05). XPS analysis showed an increase in the oxygen/carbon ratio after NTAP treatment for both groups. For the AS group, NTAP increased the µTBS after 0, 8, and 12 hours (P<.05), whereas for the APA group this occurred only after 8 hours (P<.05). For the AS and APA groups, the highest µTBS was reached after 8 hours (P<.05). CONCLUSIONS: Treatment of 3Y-TZP ceramic with NTAP improved the SE and increased the µTBS of self-adhesive resin cement to 3Y-TZP ceramic. These effects were time dependent, with better results at 8 hours after NTAP treatment.

Avaliação das características superficiais dos instrumentos Reciproc, Reciproc Blue e Xp-Endo Shaper / Evaluation of the surface characteristics of the Reciproc, Reciproc Blue and Xp-Endo Shaper instruments

Introdução: o controle da qualidade no processo de fabricação dos instrumentos endodônticos é importante uma vez que defeitos e falhas superficiais podem comprometer o preparo dos canais. Objetivo: avaliar a presença de defeitos e falhas do processo de fabricação na superfície de instrumentos Reciproc (R25), Reciproc Blue (RB25) e XP-endo shaper (XP), por meio de microscopia eletrônica de varredura (MEV). Materiais e Métodos: Ao total, foram avaliados 60 instrumentos de níquel titânio, sendo 20 por grupo: R25, RB25 e XP, em três regiões: 0mm (ponta do instrumento), 4mm e 7mm da ponta, no MEV, com aumento de 100x. As imagens foram avaliadas quanto ao número de falhas de fabricação (bordo irregular, ranhura, microcavidade e rebarba) e por um sistema de escores de 1 a 4, sendo 1, nenhuma área com defeito e 4, mais de cinco áreas com defeitos na superfície. Os dados foram submetidos à análise estatística utilizando o teste de Dunn (p<0,05). Resultados: Sobre a análise por regiões, foram identificadas diferenças significativas em grande parte dos instrumentos. Comparando os diferentes instrumentos, não foi observada diferença significativa para microcavidade (p=0,76), bordo irregular (p=0,98) e rebarba (p=0,40). O instrumento R25 mostrou maior número de ranhuras em comparação aos demais (p=0,0000*). RB25 mostrou maiores valores de escores que os instrumentos R25 (p= 0,0002) eXP (p=0,01). Conclusão: Todos os instrumentos avaliados apresentaram defeitos/falhas superficiais do processo de fabricação.

Introduction: The quality control of endodontic instruments is extremely importantsince defects and failures on their surface, during their manufacturing process, can compromise the preparation of root canal. Objective: this study evaluated the presence of defects and failures in the manufacturing process on the surface of Reciproc (R25), Reciproc Blue (RB25) and XP endo-shaper (XP) instruments by means of scanning electron microscopy (SEM). Materials and Methods: In total, sixty nickel titanium instruments (n=20): R25, RB25 and XP were evaluated in the scanning electron microscope in three regions: 0mm (tip of the instrument), 4mmand 7mm of the tip, with a magnification of 100x. The images were evaluated in relation to the number of manufacturing faults (irregular border, groove, microcavity and burr) and by a system of scores, from 1 to 4, where 1 is no defective area and 4, more than five areas with defects on the surface. The data were submitted to statistical analysis using Kruskal-Wallis and Mann-Whitney tests (p<0.05). Results: Regarding the analysis by regions, significant differences were identified in most of the instruments. Comparing the different instruments, no significant difference was observed for microcavity (p=0.76), irregular border (p=0.98) and burr (p=0.40). The R25 instrument showed a greater number of grooves compared to the others (p=0.0000*). RB25 showed higher scores than the R25(p=0.0002) and XP (p=0.01) instruments. Conclusion: All evaluated instruments showed defects/failures in the manufacturing process.Introduction: The quality control of endodontic instruments is extremely importantsince defects and failures on their surface, during their manufacturing process, can compromise the preparation of root canal. Objective: this study evaluated the presence of defects and failures in the manufacturing process on the surface of Reciproc (R25), Reciproc Blue (RB25) and XP endo-shaper (XP) instruments by means of scanning electron microscopy (SEM). Materials and Methods: In total, sixty nickel titanium instruments (n=20): R25, RB25 and XP were evaluated in the scanning electron microscope in three regions: 0mm (tip of the instrument), 4mmand 7mm of the tip, with a magnification of 100x. The images were evaluated in relation to the number of manufacturing faults (irregular border, groove, microcavity and burr) and by a system of scores, from 1 to 4, where 1 is no defective area and 4, more than five areas with defects on the surface. The data were submitted to statistical analysis using Kruskal-Wallis and Mann-Whitney tests (p<0.05). Results: Regarding the analysis by regions, significant differences were identified in most of the instruments. Comparing the different instruments, no significant difference was observed for microcavity (p=0.76), irregular border (p=0.98) and burr (p=0.40). The R25 instrument showed a greater number of grooves compared to the others (p=0.0000*). RB25 showed higher scores than the R25(p=0.0002) and XP (p=0.01) instruments. Conclusion: All evaluated instruments showed defects/failures in the manufacturing process.

Corn starch films as a long-term drug delivery system for chlorhexidine gluconate.

The present study describes the development of a chlorhexidine long-term drug delivery system using starch as a biodegradable polymer base. Three batches of thermoplastic starch films, containing starch particles/nanoparticles and chlorhexidine (CHX), were manufactured by casting. Morphological characterization showed an irregular surface with particles incorporated with chlorhexidine agglomerated in a starch matrix. Nanoindentation showed that the control film (without chlorhexidine) presented a more plastic and rigid behavior in relation to the films containing CHX. CHX was partially bounded to starch and prevented starch crystallization. Starch nanoparticles formed by precipitation were observed through transmission electron microscopy. By incorporating CHX into the solution, the nanoparticles presented different morphology, suggesting absorption of the drug. In vitro drug release was observed for 21 days by UV-vis spectrophotometry and released CHX amounted up to 19 mg/100 ml. Films presented microbiological potential for inhibiting Staphylococcus aureus growth as evaluated by the disk diffusion test in agar. It has been concluded that the developed film met the main requirements for a drug delivery system and that it is possible to be produced from a simple, cheap and reproduceable process.

Effect of previous irrigation with chlorhexidine on the push-out bond strength of a calcium silicate-based material.

This study evaluated the effect of previous irrigation with chlorhexidine (CHX) on the bond strength of a calcium silicate-based material, Biodentine, when used for furcal repair. Furcal perforations were produced in 30 extracted mandibular molars. Teeth were divided into 3 groups according to the irrigant used: distilled water (DW), CHX followed by DW (CHX), and CHX followed by ethylenediaminetetraacetic acid (EDTA) and DW (CHX/EDTA). Biodentine was used to repair the perforations. A push-out bond strength test was performed after 7 days, and data were statistically analyzed using Kruskal-Wallis and Dunn tests (P < 0.05). The CHX/EDTA group showed significantly lower values than the DW and CHX groups (P < 0.05). The failure mode of the DW group was mainly mixed, while that of the CHX group was cohesive. The CHX/EDTA group exhibited adhesive and mixed failures. Irrigation with CHX prior to furcation repair did not result in a statistically significant difference, compared to the use of DW, in the push-out bond strength of Biodentine.

Effect of different times of nonthermal argon plasma treatment on the microtensile bond strength of self-adhesive resin cement to yttria-stabilized tetragonal zirconia polycrystal ceramic.

STATEMENT OF PROBLEM: Nonthermal argon plasma may increase the surface energy of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) dental ceramics. However, studies that evaluated the effect of increased plasma treatment times on the bond strength of resin cements to Y-TZP ceramics are lacking. PURPOSE: The purpose of this in vitro study was to evaluate the effect of different nonthermal argon plasma (NTAP) treatment times on the surface energy and bond strength of a self-adhesive resin cement to Y-TZP ceramic. MATERIAL AND METHODS: Forty-eighty Y-TZP plates were divided into 2 groups (n=24): as-sintered (AS) and airborne-particle abrasion (APA) with 50-µm Al2O3, which were subdivided into 4 groups (n=6) according to the time of NTAP treatment: 0, 20, 60, and 120 seconds. The surface energy was evaluated with a goniometer. Forty Y-TZP blocks submitted to the same surface treatments (8 groups; n=5) were cemented to composite resin blocks, using a self-adhesive resin cement. After storage in distilled water at 37°C for 24 hours, the Y-TZP-composite resin blocks were cut into beams and submitted to a microtensile bond strength (µTBS) test. Data were analyzed using 2-way ANOVA and the Tukey honestly significant differences test (α=.05). RESULTS: Treatment with NTAP increased the surface energy for AS and APA groups (P<.05). For both groups, the µTBS was as follows: 0 seconds < 20 seconds < 60 seconds = 120 seconds (P<.05). Only after 120 seconds of NTAP treatment was the µTBS of APA higher than that of AS (P<.05). CONCLUSIONS: Treatment with NTAP improved the surface energy and increased the µTBS of self-adhesive resin cement to Y-TZP ceramic, with higher times of plasma treatment resulting in higher bond strength.

Preparation and characterization of thermoplastic starch composite reinforced by plasma-treated poly (hydroxybutyrate) PHB.

The present work aims to study the effect of the addition of poly (hydroxybutyrate) PHB as reinforcement in thermoplastic cornstarch (TPS) produced by the thermal compression molding method. Initially, the physical and chemical properties of TPS with different amounts of glycerol as the plasticizer (25, 30 and 35 wt%), are evaluated. Then, the composites, including 35% glycerol and different PHB contents (10, 20 and 30 wt%), are prepared. Additionally, the surface of the PHB granules is modified by plasma treatment using atmospheric air and sulfur hexafluoride (SF6) gas. In order to evaluate the influence of the PHB contents before and after the plasma treatment, the composites are characterized by FTIR, TGA, DSC, XRD, SEM, and mechanical tests. SEM showed a homogeneous distribution of PHB granules in the TPS matrix. On the other hand, the micrographs of the composites, using the high concentration of plasma-treated PHB, showed the agglomerated particles in the starch matrix, which represented stress concentrators, and showed weak interfacial adhesion leading to the poor mechanical properties. The thermogravimetric analysis of the composites with PHB treated by plasma showed a higher thermal stability compared to the composites of TPS and untreated PHB.

Tendências atuais em irrigação, entre os endodontistas brasileiros / Current trends in irrigation among Brazilian endodontists

Introdução: diferentes irrigantes têm sido estudados, propostos e utilizados durante a terapia endodôntica. Objetivo: o objetivo deste estudo foi determinar as tendências atuais em irrigação, entre os endodontistas brasileiros. Métodos: um total de 398 endodontistas brasileiros respondeu a um questionário de pesquisa na internet, com 15 questões de múltipla escolha, seleções múltiplas e rankings numéricos, sobre sua seleção de irrigante, concentração, remoção da smear layer e uso de coadjuvantes para irrigação. Resultados: o hipoclorito de sódio foi o irrigante mais utilizado em uma concentração inferior a 5,0%. Clorexidina (CHX) foi o segundo irrigante primário mais utilizado, sendo a CHX 2% em gel a forma de apresentação mais prevalente. Em relação à remoção da smear layer, 88,4% dos entrevistados declararam realizar a remoção, onde o EDTA foi o irrigante mais utilizado (93,7%). Mais de 70% dos endodontistas utilizam um sistema coadjuvante durante a irrigação, dos quais 39,9% utilizam ativação ultrassônica; 24,4%, lima plástica e 1%, ativação sônica. O uso de EndoVac não foi relatado. Conclusões: a maioria dos entrevistados utiliza hipoclorito de sódio e remove rotineiramente a smear layer durante o tratamento endodôntico utilizando EDTA. Os endodontistas brasileiros utilizam técnicas coadjuvantes à irrigação. (AU)

Effect of pH on the adsorption and interactions of Bovine Serum Albumin with functionalized silicon nitride surface.

Force-distance curves between atomic force microscopy (AFM) tip (Si3N4 non-functionalized) and bovine serum Albumin (BSA) immobilized on Si3N4 substrates have been performed with the purpose to understand how multiple interactions between the protein and the tip were favored in different pHs (4, 6 and 10). In this work, 100 silicon wafer samples were used to deposit a layer of Si3N4. Protein immobilization consisted of the silanization of the substrates with 3-aminopropyltriethoxysilane (APTES) and crosslinking with glutaraldehyde (GA). All functionalization steps were evaluated by contact angle, X-Ray electron spectroscopy (XPS) and AFM. AFM images showed increase of roughness following functionalization. At pH 4, it was possible to note that small forces (49.1 ±â€¯2.4 pN) were needed to stretch BSA, with a contour length of CL = (30.0 ±â€¯1.1 nm). At pH 6, the force applied was higher (101.5 ±â€¯5.0 pN) with a higher molecule stretch CL = (75.6 ±â€¯3.8 nm) because the pH is close to the BSA isoelectric point where the folding of the protein is favored as surfaces charges are minimized leading to lower attractive intramolecular forces. Young's Modulus were also calculated and the lowest value (265 kPa) was observed at pH 10.

Effect of a sonic device on bonding of fiberglass posts to root canals

Aim: This study evaluated the effect of a sonic device on the bonding of fiberglass posts cemented with a self-etching adhesive combined with conventional cement or a self-adhesive cement to root dentin. Methods: Forty single-rooted bovine incisors were endodontically prepared using a step-back technique. Gutta-percha and AH Plus sealer were used for root canal filling, combined with a thermoplasticization technique. After 1 week, the post space was prepared and the roots were divided into four groups according to the following factors: adhesive system/resin cement (Ambar/ AllCem Core [FGM] and RelyX U200 [3M]) and application mode (manual or sonic). The posts were cemented and the roots were cut into discs and submitted to push-out bond strength (POBS) test. The failure mode was evaluated using a stereoscope at 25x magnification. The data were analyzed statistically using ANOVA and Tukey's post-hoc test (α = 0.05). Results: The sonically activated RelyX U200 group was superior to the other groups. RelyX U200 manually applicated showed similar results to those of sonically activated Âmbar/AllCem. These three groups outperformed the Âmbar/AllCem manually applicated group. Adhesive failure between dentin and resin cement was the most predominant pattern. Conclusion: Sonic application of self-etching adhesive and self-adhesive cement improved the POBS of fiber posts to the root canal

The use of auxiliary devices during irrigation to increase the cleaning ability of a chelating agent.

OBJECTIVES: This study investigated the cleaning ability of ultrasonically activated irrigation (UAI) and a novel activation system with reciprocating motion (EC, EasyClean, Easy Equipamentos Odontológicos) when used with a relatively new chelating agent (QMix, Dentsply). In addition, the effect of QMix solution when used for a shorter (1 minute) and a longer application time (3 minutes) was investigated. MATERIALS AND METHODS: Fifty permanent human teeth were prepared with K3 rotary system and 6% sodium hypochlorite. Samples were randomly assigned to five groups (n = 10) according to the final irrigation protocol: G1, negative control (distilled water); G2, positive control (QMix 1 minute); G3, QMix 1 minute/UAI; G4, QMix 1 minute/EC; G5, QMix 3 minutes. Subsequently the teeth were prepared and three photomicrographs were obtained in each root third of root walls, by scanning electron microscopy. Two blinded and pre-calibrated examiners evaluated the images using a four-category scoring system. Data were statistically analyzed using Kruskal-Wallis and Dunn tests (p < 0.05). RESULTS: There were differences among groups (p < 0.05). UAI showed better cleaning ability than EC (p < 0.05). There were improvements when QMix was used with auxiliary devices in comparison with conventional irrigation (p < 0.05). Conventional irrigation for 3 minutes presented significantly better results than its use for 1 minute (p < 0.05). CONCLUSIONS: QMix should be used for 1 minute when it is used with UAI, since this final irrigation protocol showed the best performance and also allowed clinical optimization of this procedure.

The effects of non-thermal plasma and conventional treatments on the bond strength of fiber posts to resin cement.

OBJECTIVES: This study compared the effect of hexamethyldisiloxane (HMDSO) and ammonia (NH3) plasmas on the bond strength of resin cement to fiber posts with conventional treatments. MATERIALS AND METHODS: Sixty-five fiber posts were divided into 5 groups: Control (no surface treatment); H2O2 (24% hydrogen peroxide for 1 min); Blasting (blasting with aluminum oxide for 30 sec); NH3 (NH3 plasma treatment for 3 min); HMDSO (HMDSO plasma treatment for 15 min). After the treatments, the Ambar adhesive (FGM Dental Products) was applied to the post surface (n = 10). The fiber post was inserted into a silicon matrix that was filled with the conventional resin cement Allcem Core (FGM). Afterwards, the post/cement specimens were cut into discs and subjected to a push-out bond strength (POBS) test. Additionally, 3 posts in each group were evaluated using scanning electron microscopy. The POBS data were analyzed by one-way analysis of variance and the Tukey's honest significant difference post hoc test (α = 0.05). RESULTS: The Blasting and NH3 groups showed the highest POBS values. The HMDSO group showed intermediate POBS values, whereas the Control and H2O2 groups showed the lowest POBS values. CONCLUSION: Blasting and NH3 plasma treatments were associated with stronger bonding of the conventional resin cement Allcem to fiber posts, in a procedure in which the Ambar adhesive was used.

Surface lignin removal on coir fibers by plasma treatment for improved adhesion in thermoplastic starch composites.

The high lignin to cellulose ratio of coir fibers results in low compatibility between these fibers and natural polymers like starch, leading to poor mechanical properties in the composites. Plasma treatment using either air or oxygen proved to be an effective in removing the lignin rich amorphous layer on coir fibers, as it was clearly observed by SEM. The ratio of the FTIR signal related to lignin (1508cm-1) and cellulose (1317cm-1) decreases 10 times for air plasma treated fibers and 20 times for oxygen plasma treated samples. Composites of plasma treated short coir fibers and thermoplastic starch presented considerable increase in mechanical properties in comparison to composites made with untreated fibers. Tensile strength increased by up to 300% and elastic modulus improved by a factor of nearly 20 times, which was associated with enhanced fiber-matrix adhesion after plasma treatment with oxygen for 7.2min at 80W power.

Efeito de agentes dessensibilizantes na obliteração dos túbulos dentinários - estudo in vitro / Effect of desensitizing agents for dentinal tubules obliteration - in vitro study

Objetivo: avaliar o número de aplicações necessárias para a completa obliteração dos túbulos dentinários utilizando diferentes agentes dessensibilizantes. Material e Métodos: a porção do esmalte coronário da face vestibular de 40 incisivos bovinos foi removida com auxílio de lixas para expor a dentina superficial da junção amelo-cementária. Em seguida, as raízes e a porção coronária referente ao terço médio-incisal dos dentes foram removidas. A seguir foi realizada a completa remoção de smear layer, evidenciando os túbulos dentinários. As amostras foram divididas em quatro grupos experimentais conforme o agente dessensibilizante utilizado: verniz fluoretado, adesivo dentinário, dessensibilizante dentinário e creme dental. Os produtos foram aplicados de acordo com as recomendações do fabricante. As amostras foram avaliadas previamente e após o uso dos agentes por microscopia eletrônica de varredura de baixo vácuo. A aplicação do agente e a análise foram realizadas até a completa obliteração dos túbulos dentinários. Os dados foram avaliados estatisticamente em relação ao número de aplicações necessárias utilizando os testes de Kruskal-Wallis e Mann-Whitney (p < 0,05). Resultados: o verniz fluoretado foi o mais eficaz dos agentes avaliados, sendo necessária uma aplicação para a completa obliteração dos túbulos. Para o adesivo dentinário foram necessárias duas aplicações e para o dessensibilizante e o creme dental foram necessárias cinco aplicações. Conclusão: os agentes dessensibilizantes testados necessitam de um número variado de aplicações, sendo o mais eficaz o verniz fluoretado, onde apenas uma aplicação possibilitou a completa obliteração dos túbulos.

Objective: The aim of this study was to evaluate the number of applications necessary for the complete obliteration of dentinal tubules using different desensitizing agents. Materials and Methods: A portion of coronary enamel of the buccal surface of 40 bovine incisors was removed with the aid of sandpaper in order to expose the superficial dentin at the dentin-enamel junction. The roots and the coronary portions of the mesial-incisal third of the teeth were also removed. Complete smear-layer removal was performed, exposing the dentinal tubules. Samples were divided into four experimental groups according to the desensitizing agents used: fluoride varnish; dentin adhesive; dentin desensitizing; and toothpaste. The products were applied in accordance with the manufacturer's recommendations. Samples were evaluated before and after the application of different agents by scanning electronic microscopy of low vacuum. The application of the products and analyses were carried out until complete obliteration of dentinal tubules. Data were evaluated statistically in relation to the required number of applications, using Kruskal-Wallis and Mann-Whitney tests (p < 0.05). Results: The results showed that fluoride varnish was the most efficient of the tested agents, requiring a single application for the complete obliteration of the dentinal tubule. For the dentin adhesive, two applications were necessary and for the dentin desensitizing and toothpaste, five applications were required. Conclusion: The desensitizing agents tested required a distinct number of applications, and the fluoride varnish was the most effective agent, with a single application resulting in the complete obliteration of the dentin tubule.

Efeito do plasma de oxigênio na dentina previamente exposta ao NaOCl / Effect of oxygen plasma on dentin exposed to NaOCl

Introdução: O tratamento de plasma é uma tecnologia eficaz que pode manter as propriedades internas dos materiais inalteradas após o tratamento, modificando apenas a superfície. Objetivo: Avaliar o efeito do plasma de oxigênio na dentina previamente exposta ao NaOCl 6%. Material e método: Foram utilizados 60 incisivos bovinos. A coroa foi removida, a raiz foi dividida e as faces planificadas, totalizando 120 segmentos referentes ao terço cervical. As amostras foram divididas em dois grupos: controle (imersa em NaOCl 6%, lavada com água destilada, seca, imersa em EDTA 17%, lavada e seca) e plasma de oxigênio (após tratamento descrito no grupo controle, plasma de oxigênio foi aplicado por 30 s). As amostras foram avaliadas qualitativamente em relação à topografia por microscopia eletrônica de varredura, utilizando-se microfotografias com ampliação de 1.000×. O goniômetro Ramé-hart foi utilizado para a mensuração do ângulo de contato entre as superfícies e as seguintes soluções foram utilizadas: água, etilenoglicol e di-iodometano. Em seguida, a energia de superfície, representada pelas componentes polar e dispersiva, foi calculada. Avaliou-se também o escoamento dos cimentos Pulp Canal Sealer EWT (PCS) e Real Sal SE (RS) na superfície dentinária. Os dados foram analisados estatisticamente utilizando os testes Kruskal-Wallis e Mann-Whitney U (p<0,05). Resultado: O tratamento com plasma levou à formação de uma camada semelhante à smear layer na superfície dentinária. Este tratamento levou a um aumento da energia de superfície e da componente polar, favorecendo a hidrofilicidade da superfície. Entretanto, desfavoreceu o escoamento do cimento PCS e não influenciou no escoamento do cimento RS. Conclusão: O plasma de oxigênio ocasionou mudanças topográficas na superfície dentinária, favorecendo a hidrofilicidade desta. Contudo, não favoreceu o escoamento dos cimentos endodônticos na dentina.

Introduction: Plasma treatment is an effective technology since the internal properties of the material is kept unchanged after treatment, modifying only the surface. Objective: To evaluate the effect of oxygen plasma on dentin previously exposed to 6% NaOCl. Material and method: 60 bovine incisors were used. The crown was removed, the root splited and the faces planned amounting 120 segments related to the cervical third. The samples were divided into 2 groups, control (immersed in 6% NaOCl, washed with distilled water, dried, immersed in 17% EDTA, washed and dried) and oxygen plasma (after treatment described in the control group, oxygen plasma was applied for 30s). The samples were evaluated qualitatively in relation to topography by scanning electron microscopy using photomicrographs at 1000× of magnification. The Ramé-hart goniometer was used to measure the contact angle between the surfaces and the following solutions: water, ethyleneglycol, and diiodomethane. Then, surface energy, polar and dispersive components, was calculated. Additionally, it was evaluated the flow of Pulp Canal Sealer EWT (PCS) and Real Salt SE (RS) sealers on dentin surface. Data were statistically analyzed using Kruskal-Wallis e Mann-Whitney U (p<0.05). Result: Plasma treatment caused topographical changes on dentin surface. This treatment led to an increase in surface energy and polar component, favoring the hydrophilicity of the surface. However, it disfavors the wettability of PCS and did not influence the RS wettability. Conclusion: The oxygen plasma caused topographical changes on dentin surface, favoring its hydrophilicity. However, it did not favor the sealers wettability on dentin.

Effect of Non-Thermal Argon Plasma on Bond Strength of a Self-Etch Adhesive System to NaOCl-Treated Dentin.

Studies have been showing a decrease of bond strength in dentin treated with sodium hypochlorite (NaOCl). The aim of this study was to evaluate the effect of non-thermal argon plasma on the bond strength of a self-etch adhesive system to dentin exposed to NaOCl. Thirty-two flat dentin surfaces of bovine incisors were immersed in 2.5% NaOCl for 30 min to simulate the irrigation step during endodontic treatment. The specimens were divided into four groups (n=8), according to the surface treatment: Control (without plasma treatment), AR15 (argon plasma for 15 s), AR30 (argon plasma for 30 s) and AR45 (argon plasma for 45 s). For microtensile bond strength test, 5 specimens were used per group. In each group, the specimens were hybridized with a self-etch adhesive system (Clearfil SE Bond) and resin composite buildups were constructed. After 48 h of water storage, specimens were sectioned into sticks (5 per tooth, 25 per group) and subjected to microtensile bond strength test (µTBS) until failure, evaluating failure mode. Three specimens per group were analyzed under FTIR spectroscopy to verify the chemical modifications produced in dentin. µTBS data were analyzed using ANOVA and Tamhane tests (p<0.05). AR30 showed the highest µTBS (20.86±9.0). AR15 (13.81±6.4) and AR45 (11.51±6.8) were statistically similar to control (13.67±8.1). FTIR spectroscopy showed that argon plasma treatment produced chemical modifications in dentin. In conclusion, non-thermal argon plasma treatment for 30 s produced chemical changes in dentin and improved the µTBs of Clearfil SE Bond to NaOCl-treated dentin.

Surface modification of gutta-percha cones by non-thermal plasma.

This study was designed to evaluate the effects of Oxygen and Argon plasma on gutta-percha surfaces. A total of 185 flat smooth gutta-percha surfaces were used. Samples were divided into groups: control: no plasma treatment; Oxygen: treatment with Oxygen plasma for 1min; Argon: treatment with Argon plasma for 1min. Samples were evaluated topographically by scanning electron microscopy and atomic force microscopy; and chemically by Fourier Transform-infrared Spectroscopy. A goniometer was used to determine the surface free energy and the wettability of the endodontic sealers. Additionally 60 bovine teeth were filled using pellets of gutta-percha (control, oxygen and argon plasma) and the sealers. Teeth were evaluated by push-out and microleakage tests. Data were statistically analyzed using specific tests. Argon plasma did not change the surface topography, while Oxygen plasma led to changes. Both treatments chemically modified the gutta-percha surface. Argon and Oxygen plasma increased the surface free energy and favored the wettability of AH Plus and Pulp Canal Sealer EWT. Regarding bond strength analysis, for AH Plus sealer, both plasma treatments on gutta-percha favored the bond strength to dentin. However, for Pulp Canal Sealer, there is no statistically significant influence. For leakage test, dye penetration occurred between sealer and dentin in all groups. In conclusion, Oxygen plasma led to both topographic and chemical changes in the gutta-percha surface, while Argon plasma caused only chemical changes. Both treatments increased the surface free energy, favoring the wettability of AH Plus and Pulp Canal Sealer EWT sealers and influenced positively in the adhesion and leakage.