Age and experience with dental operating microscope: Do these factors influence on the post space preparation and adhesion of glass fiber posts?

This study evaluated the influence of operator's age and experience with dental operating microscope (DOM) on the cleaning of post space walls and on bond strength of glass fiber posts associated with self-adhesive resin cement. Sixty bovine roots were selected. Root canal preparation was performed and roots were filled using gutta-percha/AH Plus. For post space preparation, specimens were divided into four groups (n = 15), according to operator's age and the use of DOM: (1) ≥40 years; (2) ≥40 years with magnification; (3) <40 years; (4) <40 years with magnification. Next, a high-speed bur of the post system and torque-controlled round burs were used for cleaning of post space. Five roots in each group were evaluated for the degree of cleanliness under a stereo microscope using a scoring system. In the remaining 10 specimens from each group, glass fiber posts were cemented with RelyX U200. Two slices (1 ± 0.1 mm) prepared on each root third of all specimens were evaluated by push-out analysis. The scoring system was analyzed using Kruskal-Wallis and push-out data using ANOVA. Significance level was set at 5%. No significant difference was observed in cleaning scores among groups (p > .05). There was no significant difference when comparing the groups and the root thirds (p > .05). The adhesive failure between dentin, cement, and post predominated in all groups. Operator's age and experience with DOM did not influence the cleanliness of root canal walls or the bond strength of glass fiber posts associated with self-adhesive resin cement for post space preparation. RESEARCH HIGHLIGHTS: Although magnification is considered part of Endodontics, little is known about the variables associated. Operator's age and experience with microscope on cleaning of canals and on push-out of posts with self-adhesive resin cement were evaluated.

Molhabilidade de um cimento endodôntico à base de resina epóxi na dentina tratada com diferentes protocolos de quelação / Wettability of an epoxy resin-based root canal sealer on dentin treated with different chelating protocols

Objetivo: Avaliar a molhabilidade do cimento AH Plus em contato com a dentina radicular após diferentes protocolos quelantes envolvendo ácido etidrônico (HEBP) e o EDTA. Métodos: Cinquenta e seis fatias de dentina radicular foram utilizadas e irrigadas com 5.25% de hipoclorito de sódio (NaOCl) ou com uma mistura de 5.25%NaOCl/18%HEBP para simular a irrigação durante o preparo químico-mecânico. As amostras irrigadas com NaOCl foram divididas em 5 grupos, de acordo com o agente quelante: G1- água destilada (AD); G2-17%EDTA; G3-17%EDTA+2.5%NaOCl; G4-18%HEBP; e G5-18%HEBP+2.5%NaOCl. As amostras irrigadas com a mistura de NaOCl/HEBP foram dividias em 2 grupos: G6-AD; G7-NaOCl/HEBP+2.5%- NaOCl. Todos os protocolos receberam irrigação de AD entre as substâncias irrigadoras e como lavagem final. O goniômetro Rame-Hart foi utilizado para mesurar o ângulo de contato entre a superfície da dentina radicular e o cimento. O teste estatístico Kruskal-Wallis e Dunn foram aplicados (p<0.05). Resultados: Os grupos onde a smear layer foi removida apresentaram menor ângulo de contato (p<0.05), com exceção do G7. O G6 apresentou o menor ângulo de contato do AH Plus, entretanto, a irrigação final com NaOCl (G7) aumentou significativamente o ângulo de contato. G2 e G4 apresentaram comportamento similar e a irrigação final com NaOCL (G3 e G4) não modificou a molhabilidade da dentina. Conclusão: O tratamento da dentina radicular com a mistura NaOCl/HEBP, quando usada como irrigante, conferiu boa molhabilidade desta superfície ao cimento AH Plus(AU).

Evaluate the wettability of AH Plus in contact with root dentin after different chelating protocols involving etidronic acid (HEBP) and EDTA. Material and Methods: Fifty six human polished root dentin slices were used. They were irrigated with 5.25% sodium hypochlorite (NaOCl) or a mixture of 5.25%NaOCl/18%HEBP to simulate irrigation during chemomechanical preparation. The specimens irrigated with NaOCl were divided into 5 groups regarding chelating agents: G1-destiled water (DW); G2- 17%EDTA; G3-17%EDTA+2.5%NaOCl; G4-18%HEBP; and G5-18%HEBP+2.5%NaOCl. The specimens irrigated with the mixture NaOCl/HEBP were divided into 2 groups: G6-DW; G7-NaOCl/HEBP+2.5%NaOCl. All protocols received irrigation with DW between irrigants and as final rinse. Rame-Hart goniometer was used to measure the contact angle between the dentin surfaces and the sealer. Kruskal-Wallis and Dunn tests were applied (p<0.05). Results: Groups in which the smear layer was removed showed a lower contact angle (p<0.05), except for G7. The G6 showed the lowest contact angle of AH Plus, but the NaOCl final irrigation (G7) increased the angle. G2 and G4 have similar behaviour and final irrigation with NaOCl (G3 and G5) did not change wettability when these chelators were used. Conclusions: The mixture NaOCl/HEBP showed good effect on the wettability of sealer on to the root canal dentine, when used as main irrigant (AU).

Evaluation of different surface treatments on fiber post cemented with a self-adhesive system.

Surface treatment of fiber-reinforced posts can increase adhesion, especially on the post/resin cement interface. The purpose of this in vitro study was to evaluate the effect of different surface treatments on fiber post cemented with a self-adhesive system. Sixty fiberglass epoxy resin posts were cleaned, dried and divided into 6 groups (n=10): Control (no surface treatment), silane (silane coupling agent was applied homogeneously on surface), 24% hydrogen peroxide (H2O2) (immersion during 1min), blasting (blasting with aluminum oxide for 30s), NH3 plasma (plasma treatment for 3min) and HMDSO plasma (plasma treatment for 15min). After the treatments, posts were inserted into a silicon matrix that was filled with the resin cement RelyX U200. Afterwards, the post/cement specimens were cut perpendicularly to the long axis of the posts into six 1.0mm thick discs and submitted to a push-out bond strength (POBS) test. Failure pattern was classified in 5 types: type I: cohesive in post; type II: cohesive in cement; type III: cohesive post and cement; type IV: adhesive post/cement; and type V: mixed (association between cohesive and adhesive). Data were analyzed by one-way ANOVA and Tukey HSD post hoc test (α=0.05). Silane (15.94±6.5), blasting (13.13±3.6), NH3 plasma (14.44±4.0) and HMDSO plasma (13.23±5.3) showed higher POBS when compared to control (p<0.05) and similar among them. H2O2 (9.40±4.0) treatment showed POBS values statistically similar to control (9.65±3.6). Failures were predominantly cohesive post and cement, type III, in all groups. In conclusion, surface treatments influenced in the adhesion of fiberglass post with the self-adhesive cement RelyX U200. Silane, blasting with aluminum oxide and plasmas (NH3 and HMDSO) showed results superior to 24% hydrogen peroxide.

Effects of auxiliary device use on smear layer removal.

This study evaluated the effects of different auxiliary irrigation devices on smear layer removal with a chelating solution (QMix). Fifty single-rooted permanent human teeth were shaped with a sequence of nickel-titanium instruments. A 2% chlorhexidine gel was used as a chemical auxiliary substance during preparation. Samples were assigned to five groups (n = 10 each) according to final irrigation protocol, namely, distilled water (control group), QMix 1 min, QMix + passive ultrasonic irrigation (PUI), QMix + plastic endodontic finishing file (EC), and QMix 3 min. Teeth were prepared and evaluated by scanning electron microscopy, and three photomicrographs (magnification, 1,000×) were obtained for each root third. Two blinded and precalibrated evaluators analyzed and scored the images, and the data were statistically analyzed by the Kruskal-Wallis and Dunn tests (P < 0.05). Groups were ranked according to the extent of smear layer removal. The total area of the root canal walls and apical root thirds was calculated, and the groups ranked PUI > EC = QMix 3 min > QMix 1 min > control. QMix 1 min was effective for smear layer removal only when used with auxiliary devices, and QMix + passive ultrasonic irrigation yielded the best results, particularly for the apical third.(J Oral Sci 58, 561-567, 2016).

Visualization of internal structure of banana starch granule through AFM.

Atomic force microscopy (AFM) is a high resolution technique for studying the external and internal structures of starch granules. For this purpose granules were isolated from bananas and embedded in a non-penetrating resin. To achieve image contrast of the ultrastructure, the face of the cut blocks were wetted in steam and force modulation mode imaging was used. Images of starch from green bananas showed large variation of height across the granule due to a locational specific absorption of water and swelling of amorphous regions; the data reveal that the center of the granules are structurally different and have different viscoelastic properties. Images of starches from ripe bananas showed an even greater different level of organization: absence of growth rings around the hilum; the central region of the granule is richer in amylose; very porous surface with round shaped dark structures; the size of blocklets are larger than the green fruits.

Analysis of asphaltic binders modified with PPA by surface techniques.

Samples of unmodified and modified asphalt binders containing 1% polyphosphoric acid were studied. Fourier-transform infrared spectroscopy was used to evaluate the structural indices of the functional groups present in the samples and the results indicated there was a strong interaction between the polyphosphoric acid and oxygenated species. Contact angle measurements indicated that adhesion of the binder to the aggregate depended on the polyphosphoric acid content. Atomic force microscopy was used to relate features observed on the surface of the asphalt binder 50/70, with their local mechanical properties such as stiffness and elasticity. It was observed that the surface of the sample containing 1% polyphosphoric acid provides stiffness values lower than the unmodified asphalt binder.

Effect of different irrigation protocols on resin sealer bond strength to dentin.

INTRODUCTION: The aim of this study was to evaluate the influence of different irrigation protocols on resin-based sealer bond strength to dentin and the associated failure pattern. METHODS: One hundred eighty single-rooted premolars were used. Roots were divided into 18 groups according to the irrigation protocol used and instrumented using 5.25% NaOCl or 2% chlorhexidine (CHX) gel as chemical auxiliary substances and 17% EDTA or 37% phosphoric acid for smear layer removal. Finally, CHX solution was used as the final irrigant in some groups. Root canals were filled with either gutta-percha and AH Plus (Dentsply, Petropolis, RJ, Brazil) (GP/AH) or Resilon/Real Seal SE (SybronEndo, Orange, CA). Bond strength was measured by the push-out test. Additionally, failure patterns were classified as adhesive, cohesive, and mixed. Data were statistically analyzed by Kruskal-Wallis and Mann-Whitney U tests. RESULTS: In the GP/AH groups, high bond strength values were obtained when NaOCl was associated with phosphoric acid with (6.9 ± 3.9) and without (7.4 ± 3.8) a final flush with CHX. However, when CHX gel was used, the association with EDTA with (7.5 ± 3.2) and without (6.0 ± 2.3) a final flush with CHX solution showed better results. The GP/AH groups mainly showed a cohesive failure pattern. Evaluation of Resilon/Real Seal SE showed that higher bond strength values were reached when CHX was associated with phosphoric acid with (5.2 ± 3.0) and without (4.2 ± 2.0) a final flush with CHX solution. The failure patterns were mainly adhesive. CONCLUSIONS: Irrigation protocols influenced the bond strength of resin sealers to dentin.

Interactions between irrigants commonly used in endodontic practice: a chemical analysis.

INTRODUCTION: The aim of this work was to characterize the by-products formed in the associations between the most commonly used irrigants in endodontic practice through electrospray ionization quadrupole time-of-flight mass spectrometry analyses. METHODS: Sodium hypochlorite (NaOCl) (0.16%, 1%, 2.5%, and 5.25%) was associated with 2% chlorhexidine (CHX) solution and gel, 17% EDTA, 10% citric acid, 37% phosphoric acid, saline solution, ethanol, and distilled water. CHX solution and gel were also associated with all above mentioned irrigants. The solutions were mixed in a 1:1 ratio, and electrospray ionization quadrupole time-of-flight mass spectrometry was used to characterize the precipitates when formed. RESULTS: CHX produced an orange-brown precipitate when associated with NaOCl from 1%-5.25% and an orange-white precipitate when associated with 0.16% NaOCl. When associated with EDTA, CHX produced a white milky precipitate, and when associated with saline solution and ethanol, a salt precipitation was produced. No precipitation was observed when CHX was associated with citric acid, phosphoric acid, or distilled water. In the NaOCl associations, precipitation occurred only when CHX was present. CONCLUSION: The orange-brown precipitate observed in the association between CHX and NaOCl occurs because of the presence of NaOCl, an oxidizing agent causing chlorination of the guanidino nitrogens of the CHX. The precipitates formed in the reaction of CHX with EDTA, saline solution, and ethanol were associated with acid-base reactions, salting-out process, and lower solubility, respectively. NaOCl associated with EDTA, citric acid, and phosphoric acid leads mainly to chlorine gas formation. Intermediate flushes with distilled water seem to be appropriate to prevent or at least reduce formation of by-products.

Effect of in-office bleaching agents on the surface roughness and morphology of different dental composites: an AFM study.

The aim of this study was to evaluate, using atomic force microscopy, the effect of two different bleaching agents on the modification of dental composites materials. This modification will be judged by analyzing the variation of surface roughness and surface morphology of two different composites: one containing nanoparticles and other consisting of microhybrid resin. The bleaching was performed by using two different concentrations of hydrogen peroxide: HP Blue (20% hydrogen peroxide) and Whiteness HP Maxx (35% hydrogen peroxide). Disks of Esthet X and Filtek™ Z350 composites were used. Atomic force microscopy was used for analyses of the same place of the sample before and after treatment. A total of 12 analyses were performed per group (n = 12). The samples were analyzed qualitatively by evaluating morphological changes in the images and quantitatively by using roughness parameters (Ra). Data were analyzed statistically using Kruskal-Wallis, Mann-Whitney, and Friedman tests (P < 0.05). Changes were observed both qualitatively and quantitatively only in the groups where Esthet X resin was used. The use of hydrogen peroxide bleaching agents caused changes only in the surface of microhybrid composites, with no changes being observed in the composite containing nanoparticles. Despite being even significant, these alterations are clinically slight and can be eliminated by polishing them.

Inducing surface hydrophobization on cornstarch film by SF6 and HMDSO plasma treatment.

The development of thermoplastic materials based on starch has become a promising alternative for reducing plastic waste. To this end, plasma treatments were used to enhance the hydrophobicity of cornstarch films. Cornstarch films plasticized using glycerol and distilled water were prepared by casting. A surface modification method was employed using different precursor gases, HMDSO and SF(6), and a combined treatment using HMDSO followed by SF(6) (HMDSO/SF(6)) and then the reverse, using SF(6) first followed by HMDSO (SF(6)/HMDSO). The results indicated that the induced surface morphology determines the contact angle. It was observed that all films became hydrophobic, and films that were initially treated with SF(6) showed the greatest hydrophobicity if no further coating was applied, or if the treated surface was further coated using HMDSO. Under both of these treatment conditions the contact angle was greater than 110°.

Evaluation of different irrigation protocols concerning the formation of chemical smear layer.

The aim of this work was to evaluate, by means of scanning electron microscopy (SEM) and electron dispersive spectroscopy (EDS), the different irrigation protocols concerning the formation of chemical smear layer (CSL). Fifty-five teeth were instrumented by using distilled water (DW) as irrigant. Next, the teeth were submitted to a protocol for removal of the mechanical smear layer produced. The teeth were divided into 11 groups, according to irrigation regimen. Then, the teeth were prepared and analyzed with SEM and EDS. Only in Group 1 [1 mL sodium hypochlorite (NaOCl) + 10 mL DW + 1 mL chlorhexidine (CHX) solution], Group 2 [1 mL NaOCl + 10 mL DW + 1 mL ethylenediaminetetraacetic acid (EDTA) + 10 mL DW + 1 mL CHX solution], and Group 3 [1 mL NaOCl + 10 mL DW + 1 mL citric acid (CA) + 10 mL DW + 1 mL CHX solution], the formation of CSL was observed. In the groups where CHX gel was used alone or in association with EDTA, CA, phosphoric acid (PA), and CHX solution, no formation of CSL was observed. According to the results found in the cases in which one wants to associate NaOCl with CHX, the protocol using PA (1 mL NaOCl + 10 mL DW + 1 mL PA + 10 mL DW + 1 mL CHX solution) did not induce formation of CSL.

Effect of disinfection solutions on the adhesion force of root canal filling materials.

INTRODUCTION: Sodium hypochlorite (NaOCl) and chlorhexidine (CHX) are usually used to disinfect gutta-percha (GP) and Resilon (Res) cones. This study investigated the adhesion force (Fad) between root canal sealers and GP and Res cones following different disinfection protocols by using atomic force microscopy. METHODS: Nine flat surfaces of each material were obtained with medium points of GP and Res. The samples were divided into 6 groups (n = 3): control group GP, immersion in distilled water (DW); NaOCl group GP, immersion in 5.25% NaOCl and then washing with DW; CHX group GP, immersion in 2% CHX and then washing with DW; control group Res, immersion in DW; NaOCl group Res, immersion in 5.25% NaOCl and then washing with DW; and CHX group Res, immersion in 2% CHX and then washing with DW. Atomic force microscopy tips containing AH Plus sealer were used to obtain force versus distance curves regarding GP surfaces. Fad was calculated from the force curves. The same procedure was performed with Real Seal SE and Res surfaces. Data were statistically analyzed. RESULTS: A higher Fad between solid filling materials (GP and Res) and root canal sealers was found when CHX solution was used. Treatment with NaOCl solution did not show influence on the Fad values. CONCLUSIONS: The decontamination of GP and Res with 2% CHX resulted in higher Fad values. The use of CHX in the disinfection process of GP and Res cones might be a better option before root canal obturation.

Effect of disinfectant solutions on gutta-percha and resilon cones.

The aim of this study was to evaluate the effects of the 5.25% sodium hypochlorite (NaOCl), 2% chlorhexidine (CHX), and MTAD solutions on the surface of gutta-percha and Resilon cones by using atomic force microscopy (AFM). Accessory cones were washed and dried. The cones were randomly divided into six groups: gutta-percha immersed in NaOCl, CHX, and MTAD, and Resilon immersed in NaOCl, CHX, and MTAD. AFM images of the same area were made in different periods of time. JPK™ Image Processing Software was used to evaluate the images. The parameters used to evaluate the changes were RMS and line profiles. No statistically significant change was observed in the RMS values. The line profiles detected changes only for gutta-percha surfaces after immersion in NaOCl and MTAD solutions. In conclusion, 5.25% NaOCl and MTAD are associated with local changes in surface roughness of gutta-percha cones. No change was observed when 2% CHX was used. The use of all tested solutions did not produce any changes on Resilon surface.

Comparison between the effect of plasma and chemical treatments on fiber post surface.

INTRODUCTION: The aim of the present study was to evaluate the fiber post surface after plasma and usual treatments and the adhesion between treated fiber posts and Rely X Unicem resin cement (3M ESPE, St Paul, MN). METHODS: Flat fiber posts were divided into 6 groups according to surface treatment: silane, hydrofluoric acid, hydrofluoric acid plus silane, plasma polymerization with argon, ethylenediamine plasma (EDA), and the control group. A goniometer was used to measure the contact angle between the groups with water or resin cement. Scanning electron microscopy and electron dispersive spectroscopy were used to examine the topography and chemical changes in the post surfaces after treatment. Push-out tests were performed using a universal testing machine to evaluate the adhesion strength between treated fiber posts and resin cement. RESULTS: In the contact angle with water, the most hydrophilic surface was observed in samples treated with argon plasma, followed by treatments with silane and hydrofluoric acid plus silane. The hydrophobic characteristic was observed with EDA and hydrofluoric acid. The contact angle with dual resin cement showed lower values with argon and EDA, followed by silane and hydrofluoric acid plus silane. Electron dispersive spectroscopy analyses showed chemical modifications in the surface after different treatments although topographic changes were verified only with EDA plasma compared with the control. Push-out results did not show differences between groups compared with the control, except for EDA plasma treatment. CONCLUSIONS: Plasma treatment favored the wettability of the post surface by modifying it chemically. Adhesion improvement was only observed after EDA treatment.

Evaluation of the interaction between endodontic sealers and dentin treated with different irrigant solutions.

INTRODUCTION: Dentin surface treatment with different substances might cause alterations in chemical and structural compositions of the human dentin. The aim of this study was to investigate the wettability of endodontic sealers in contact with dentin treated with 5.25% sodium hypochlorite (NaOCl) and 2% chlorhexidine (CHX) in the presence or absence of smear layer. METHODS: Thirty-six dentin slices were used. They were irrigated with NaOCl and washed with distilled water (DW) to simulate irrigation during chemomechanical preparation. After this procedure, the samples were divided into 6 groups: group 1, DW (control); group 2, NaOCl + DW; group 3, CHX + DW; group 4, ethylenediaminetetraacetic acid (EDTA) + DW; group 5, EDTA + DW + NaOCl + DW; group 6, EDTA + DW + CHX + DW. The Ramé-Hart goniometer was used to measure the contact angle between the dentin surfaces and the AH Plus and Real Seal SE sealers. Data were statistically analyzed. RESULTS: With regard to the contact angle between AH Plus and treated surfaces, the values of contact angle were lower when CHX was used, regardless of the presence or absence of smear layer. When Real Seal SE was evaluated, in the absence of smear layer, CHX presented lower values of contact angle. In the presence of smear layer, the use of NaOCl and CHX did not favor the spread of the sealer. CONCLUSIONS: The present study has revealed that smear layer removal and final flush with CHX favor the wettability of AH Plus and Real Seal SE sealers.

Effect of disinfectant solutions on the surface free energy and wettability of filling material.

INTRODUCTION: Gutta-percha (GP) and Resilon (Res) cones are usually disinfected by the use of solutions such as sodium hypochlorite (NaOCl) and chlorhexidine (CHX). The aims of this study were to evaluate the surface free energy of GP and Res cones after disinfection procedures and to investigate the wettability of endodontic sealers in contact with these surfaces. METHODS: GP and Res flat smooth surfaces were prepared. Thirty-six samples of each material were used. The samples were divided into 6 groups as follows: Control group GP, immersed in Milli-Q water (MQW); CHX group GP, immersed in 2% CHX solution and then washed with MQW; NaOCl group GP, immersed in 5.25% NaOCl and then washed with MQW; Control group Res, immersed in MQW; CHX group Res, immersed in 2% CHX solution and then washed with MQW; and NaOCl group Res, immersed in 5.25% NaOCl and then washed with MQW. Samples were analyzed first with a goniometer to measure the contact angle between the test surfaces and 3 solutions (water, ethylene glycol, and diiodomethane) to determine the surface free energy. Then the contact angle between surfaces and each one of the sealers tested, AH Plus and Real Seal SE, was measured. Data were statistically analyzed. RESULTS: The results showed that when disinfectant solutions were used, the surface free energy was greater. When evaluating the interaction between materials and sealers, the use of CHX presented lower values of contact angle, followed by NaOCl. CONCLUSIONS: It was concluded that the solutions used in decontamination increase the surface free energy, promoting high interaction between GP/Res and sealers.

The importance of final rinse after disinfection of gutta-percha and Resilon cones.

OBJECTIVES: The aim of this study was to evaluate the morphologic alterations on the surface of gutta-percha and Resilon cones exposed to disinfectant solutions. STUDY DESIGN: Fifty-six gutta-percha and Resilon cones were used. Seven groups were analyzed: G1: control; G2, G3, and G4: 5.25% NaOCl, 2% CHX, and MTAD, respectively, without final rinse; G5, G6, and G7: the same solutions with final rinse. Then the samples were analyzed by means of scanning electron microscopy and energy dispersive spectroscopy. RESULTS: Regarding the use of NaOCl without rinse, there was chloride crystal formation in all samples. When the cones were rinsed, the crystals were removed. When 2% chlorhexidine was used, no change was observed. MTAD without rinse showed the presence of a precipitate in gutta-percha cones. When the cones were rinsed, it was eliminated. CONCLUSIONS: The final rinse is essential, especially when NaOCl and MTAD are used in the cones' disinfection process.

Scanning electron microscopic investigation of the effectiveness of phosphoric acid in smear layer removal when compared with EDTA and citric acid.

INTRODUCTION: The smear layer adheres to dentinal surface, thus occluding the dentinal tubules. Because this layer disfavors the penetration of irrigant solutions and root canal fillings, it should be removed. The aim of this study was to compare the effectiveness of 37% phosphoric acid with that of 17% EDTA and 10% citric acid in the removal of smear layer. MATERIALS AND METHODS: Fifty-two maxillary single-rooted human canines were accessed and instrumented. Between each instrument used, the canals were irrigated with sodium hypochlorite. After instrumentation, the teeth were irrigated with distilled water and then divided into groups according to the time and substances employed. The substances used were 17% EDTA, 10% citric acid, and 37% phosphoric acid solution and gel. The experimental time periods were of 30 seconds, 1 minute, and 3 minutes. The samples were prepared and observed by means of scanning electron microscopy. Three photomicrographs (2,000×) were recorded for each sample regarding the apical, middle, and cervical thirds. A score system was used to evaluate the images. RESULTS: None of the substances analyzed in this study was effective for removing the smear layer at 30 seconds. In the 1-minute period, the phosphoric acid solution showed better results than the other substances evaluated. In the 3-minute period, all the substances worked well in the middle and cervical thirds although phosphoric acid solution showed excellent results even in the apical third. CONCLUSIONS: These findings point toward the possibility that phosphoric acid solution could be a promising agent for smear layer removal.

Hydrophobic corn starch thermoplastic films produced by plasma treatment.

Polymer coating technology is currently an important field in science as it can lead to final products with enhanced characteristics characterized by desired bulk and surface properties. Low power plasmas can induce the polymerization of a precursor gas on the substrate surface as well as introduce functional groups under specific plasma conditions. In the present work, we studied the possibility of reducing water sensitivity of corn starch films by sulfur hexafluoride (SF(6)) plasma treatment. Confocal laser microscopy as well as atomic force microscopy was used to observe the main surface modifications and results indicated starch cross-linking. Fluoride was incorporated to the surface and the relationship between fluoride and sulfur incorporation to the surface was very much dependent on plasma power. Results indicate that fluoride could be preferentially incorporated on polymeric surfaces at -100V self-bias and the overall surface morphology determined the measured contact angle. The dynamic behavior of surface contact angle was observed to be very much dependent on the treatment time and force-distance curves were used to further characterize the chemical surface modifications locally. Optimized treatment conditions led to water contact angles up to 130 degrees . Even after being in contact with water for 10min, surfaces remained hydrophobic, presenting contact angles over 100 degrees .