• Polymer(Korea)
• /
• v.29 no.1
• /
• pp.36-40
• /
• 2005

Poly(amino acid) derivatives have been widely investigated as a drug carrier in drug delivery system. Particularly,polysuccinimide (PSI) is one of the most promising drug carriers since it possesses suitable physicochemical characteristics for development of macromolecular prodrugs, due to biocompatibility and biodegradability. In this study, we deal with the synthesis of polyaspartamide having various functional groups such as methoxy-poly(ethylene glycol) (MPEG) via ring closing of PSI. PSI was synthesized by polyonensation polymerization of spartic acid. The variety of average molecular weight was confirmed with reacion time and catalyst content to observe the optimum condition of synthesis. MPEG, hydrophilic chain, was bonded to fabricate polymeric micell composed of hydrophilic and hydrophobic polymer. All materials were characterized by 1H-NMR, FT-IR and GPC. In addition, the formation of nanoparticle micelle as drug carrier were also examined. Micelle size was measured by ELS and AFM. The functionalized polysparamide formed nanoparticle micelle whose size ranged from 90 to 130 nm. In conclusion, we prepared polyaspartamide functionalized with PEG examined the possibility as drug carriers.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.59-59
• /
• 2010

Graphene is a 2-D sheet of $sp^2$-bonded carbon arranged in a honeycomb lattice. This material has attracted major interest, and there are many ongoing efforts in developing graphene devices because of its high charge mobility and crystal quality. Therefore clear understanding of the substrate effect and mechanism of synthesis of graphene is important for potential applications and device fabrication of graphene. In a published paper in J. Phys. Chem. C (2008), the effect of substrate on the atomic/electronic structures of graphene is negligible for graphene made by mechanical cleavage. However, nobody shows the interaction between Ni substrate and graphene. Therefore, we have studied this interaction. In order to studying these effect between graphene and Ni substrate, We have observed graphene synthesized on Ni substrate and graphene transferred on $SiO_2$/Si substrate through Raman spectroscopy. Because Raman spectroscopy has historically been used to probe structural and electronic characteristics of graphite materials, providing useful information on the defects (D-band), in-plane vibration of sp2 carbon atoms (G-band), as well as the stacking orders (2D-band), we selected this as analysis tool. In our study, we could not observe the doping effect between graphene and Ni substrate or between graphene and $SiO_2$/Si substrate because the shift of G band in Raman spectrum was not occurred by charge transfer. We could noticed that the bonding force between graphene and Ni substrate is more strong than Van de Waals force which is the interaction between graphene and $SiO_2$/Si. Furthermore, the synthesized graphene on Ni substrate was in compressive strain. This phenomenon was observed by 2D band blue-shift in Raman spectrum. And, we consider that the graphene is incommensurate growth with Ni polycrystalline substrate.

• Restorative Dentistry and Endodontics
• /
• v.35 no.6
• /
• pp.479-485
• /
• 2010

Objectives: The aim of this study was to compare the push-out bond strengths of resin cement/fiber post systems to post space dentin using different application methods of resin cement. Materials and Methods: Thirty extracted human premolars were selected and randomly divided into 3 groups according to the technique used to place the cement into root canal: using lentulo-spiral instrument (group Lentulo), applying the cement onto the post surface (group Direct), and injecting the material using a specific elongation tip (group Elongation tip). After shaping and filling of the root canal, post space was drilled using Rely-X post drill. Rely-X fiber post was seated using Rely-X Unicem and resin cement was light polymerized. The root specimens were embedded in an acrylic resin and the specimens were sectioned perpendicularly to the long axis using a low-speed saw. Three slices per each root containing cross-sections of coronal, middle and apical part of the bonded fiber posts were obtained by sectioning. The push-out bond strength was measured using Universal Testing Machine. Specimens after bond failure were examined using operating microscope to evaluate the failure modes. Results: Push-out bond strengths were statistically influenced by the root regions. Group using the elongation tip showed significantly higher bond strength than other ways. Most failures occurred at the cement/dentin interface or in a mixed mode. Conclusions: The use of an elongation tip seems to reduce the number of imperfections within the selfadhesive cement interface compared to the techniques such as direct applying with the post and lentulospiral technique.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.37 no.4
• /
• pp.209-216
• /
• 2021

Purpose: The purpose of this study is to compare the shear bond strength of resin cement for orthodontic brackets without applying an adhesive primer, to the case of applying an adhesive primer. Materials and Methods: The specimens were divided into three experimental groups, Transbond XT, GC Ortho Connect and Orthomite LC, and the enamel surface was divided into two sections, one with 37% phosphoric acid and the other with 37% phosphoric acid and an adhesive primer or universal adhesive. Each of three types of cement was applied to orthodontic bracket, and after bonding, the shear bond strength was measured. Results: Transbond XT and Orthomite LC significantly increased shear bond strength when orthodontic brackets were bonded after applying an adhesive primer and universal adhesive, respectively. Conclusion: It is expected that application of an adhesive primer or universal adhesive after acid etching will improve shear bond strength of orthodontic brackets in Transbond XT and Orthomite LC.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.49 no.3
• /
• pp.264-273
• /
• 2022

Due to the development of properties of adhesive materials currently used in dentistry, the bonding ability between the brackets and the tooth enamel has been greatly improved. In general, in situations where cooperation can be obtained, adhesion of the orthodontic bracket through the conventional three-step process can show excellent bonding strength. However, if it is difficult to expect patient cooperation, as in the pediatric dentistry area, or if moisture isolation is not properly performed, the binding strength that does not reach the expected effect. As a result, various products that simplify the process for adhesion are being developed. The aim of this study was to evaluate and compare the shear bonding strength between the conventional 3-step adhesion system, self-etching primer system and one-step adhesion system that reduces the priming process. A total of 60 human maxillary, mandibular premolars were prepared. Group I (control group) were followed conventional 3-step bonding process. Group II were conditioned with self-etching primer. Group III were etched with 37% phosphoric acid and brackets were bonded with self-priming adhesive. The resultant shear bond strength of each group was measured and an adhesive remnant index (ARI) was recorded. The mean shear bond strength of group I, II, III were 14.69 MPa, 11.21 MPa and 12.21 MPa respectively. Significant differences could only be found between group I, II and group I, III (p < 0.05). The ARI indicated no significant difference among all groups.

• The korean journal of orthodontics
• /
• v.25 no.2 s.49
• /
• pp.223-233
• /
• 1995

The purpose of this study was to evaluate the effects of surface conditioning with $10\%$ polyacrylic acid, etching with $38\%$ phosphoric acid, and polishing with a slurry of pumice on shear bond strengths of light-cured glass ionomer cement, chemically cured glass ionomer cement, and a composite resin to enamel, and to observe the failure patterns of bracket bondings. Shear bond strengths of glass ionomer cements were compared with that of a composite resin. Metal brackets were bonded on the extracted human bicuspids after enamel surface treatments, and samples were immersed in the $37^{\circ}C$ distilled water bath, and shear bond strengths of glass ionomer cements and a composite resin were measured on the Instron machine after 24hrs passed, and the deboned samples were measured in respect of adhesive remnant index. Scanning electron micrographs were taken of enamel surfaces after various treatments. The data were evaluated and tested by ANOVA and Duncan's multiple range test, and those results were as follows. 1. Shear bond strength of light-cured glass ionomer cement showed statistically higher than that of chemically cured glass ionomer cement. 2. Shear bond strengths of light-cured and chemically cured glass ionomer cements to enamel treated with $10\%$ polyacrylic acid and $38\%$ phosphoric acid showed statistically higher than those with a slurry of pumice. 3. According to scanning electron micrographs, enamel surface conditioned with $10\%$ polyacrylic acid is slightly etched and cleaned, that etched with $38\%$ phosphoric acid is severely etched, and that polished with a slurry of pumice is irregulary scretched and not completely cleaned. 4. After debonding, light-cured glass ionomer cement to enamel treated with $10\%$ polyacrylic acid showed less residual materials on the enamel solace than composite resin to enamel etched with $38\%$ phosphoric acid. 5. There was no significant difference in the shear bond strength of light-cured glass ionomer cement to enamel treated with $10\%$ polyacrylic acid and that of composite resin to enamel etched with $38\%$ Phosphoric acid.

• The Journal of Korean Academy of Prosthodontics
• /
• v.52 no.2
• /
• pp.113-120
• /
• 2014

This study will evaluate the effectiveness of various pretreatments when fiber-reinforced composite (FRC) post is bonded to endodontically treated tooth with resin cement. Materials and methods: Canal shaping of FRC post (DT Light post, Size 3, Bisco Inc., Schaumburg, IL, USA) was performed on endodontically treated premolars at 1.5 cm from CEJ. Samples were divided into 6 groups of surface treatment after conventional washing and drying to the canal. Total of 24 FRC posts were randomly divided into 6 groups of surface treatment as follows: Group C: control - no surface treatment, Group A: airborne-particle abrasion (Cojet sand, 3M ESPE), Group S: silanization (Bis-silane, Bisco Inc.), Group M: universal primer (Monobond-plus primer, Ivoclar Vivadent Inc.), Group AS: silanization after airborne-particle abrasion, Group AM: universal primer treatment after airborne-particle abrasion. Pretreated fiber posts were cemented with resin-based luting material and photo-polymerized and cut to the thickness of 1 mm. Push-out test using a universal testing machine was performed. Bonding failure strength of post dislodgement was measured and the type of bonding failure was classified. Data were analyzed with Kruskal-Wallis test and multiple comparison groups were performed using Tukey HSD value of rank test (${\alpha}=0.05$). Results: Group AS showed significantly highest bonding strength. Group S, group AM, group A, and group M showed lower bonding strength in order. The control group showed the lowest bonding strength. Conclusion: Surface treatment with silane showed to be the most effective of the surface pretreatment methods for cementation of FRC post. Surface treatment with universal primer showed no significant difference compared with no surface treatment group as for bonding strength.

• The Journal of Korean Academy of Prosthodontics
• /
• v.52 no.1
• /
• pp.1-8
• /
• 2014

Purpose: The purpose of this study is to evaluate the effect of applying Silano-pen to feldspathic porcelain and zirconia on shear bond strength with composite resin. Materials and methods: Feldspathic porcelain and zirconia specimens were produced into 30 per each 2 mm thick and 12 mm in diameter and their surface was made smooth and even and then embedded in acrylic resin. The specimens were divided into each Group F (Feldspathic porcelain) and Group Z (Zirconia), (1) Hydrofluoric acid etching and silane (F1 & Z1), (2) Silano-pen and silane (F2 & Z2), (3) Hydrofluoric acid etching and Silano-pen, silane (F3 & Z3). After surface conditioning, substrate surfaces of the specimen were examined by SEM. Composite resin cylinders (2 mm high, 3 mm in diameter)were bonded to specimen and shear bond strength between ceramic and composite resin was measured by using universal testing machine. The measured values were statistically analyzed by using two way ANOVA and Tukey's multiple comparison test (${\alpha}=.05$). Results: In the scanning electron micrograph of the treated ceramic surface, Group F2 and F3 appeared the high roughness and Group Z3 appeared the highest density of silica particle. In Feldspathic porcelain, the result of measuring shear bond strength showed that Group F3 was measured to be highest and Group F1 was measured to be lowest but there was no statistical significance among Groups. In zirconia, Group Z3 was measured to be highest and Group Z1 was measured to be lowest and there was statistical significance among Groups (P<.05). Conclusion: In zirconia, applying hydrofluoric acid etching and then Silano-pen and silane is effective for composite resin adhesion.

• The Journal of Korean Academy of Prosthodontics
• /
• v.51 no.1
• /
• pp.20-26
• /
• 2013

Purpose: The purpose of this study was to evaluate the bond strengths between the latest CAD/CAM ceramic inlay and various resin cements which are used primarily for esthetic restoration. Materials and methods: Cylindrical ceramic blocks(Height: 5 mm, diameter: 3 mm) were fabricated by using Cerec3 and bonded on the dentin of the ninety extracted caries-free molars using three different kinds of resin cement(Unicem$^{(R)}$, Biscem$^{(R)}$, and Variolink II$^{(R)}$) according to the manufacturer's instructions. Ninety specimens were divided into 3 groups according to three different kinds of resin cement. Half of each group were conducted thermocycling under the conditions of the $5-55^{\circ}C$, 5,000 cycle but the other half of them weren't. All specimens were kept in normal saline $37^{\circ}C$, for 24 hours before measuring the bond strength. The shear bond strength was measured by Universal testing machine with a cross head speed of 0.5 mm/min. The results were analyzed statistically by t-test and one-way ANOVA. Results: Unicem$^{(R)}$ group showed the highest shear bond strength despite a slight decline by thermocycling. The shear bond strength of Unicem$^{(R)}$ group and ValiolinkII$^{(R)}$ group were significantly influenced by thermocycling, whereas Biscem$^{(R)}$ group was not influenced (P<.05). There were no significant differences in the bond strength between the three groups without thermocycling, but there was significant differences between Unicem$^{(R)}$ group and Valiolink II$^{(R)}$ group with thermocycling(P<.05). Conclusion: It has been shown to be clinically effective when the self-adhesive resin cements Unicem$^{(R)}$ and Biscem$^{(R)}$ were used instead of the etch-and-rinse resin cement Valiolink II$^{(R)}$ during the bonding of CAD/CAM ceramic inlay restorations with teeth.

• Korean Journal of Soil Science and Fertilizer
• /
• v.20 no.3
• /
• pp.251-259
• /
• 1987

Humic acids extracted from decomposing plant residues were characterized by infrared(IR) spectra. The IR spectra were further interpreted by chemical analyses for oxygen-containing functional groups such as carboxyl, phenolic, alcoholic, carbonyl, and quinionic groups. 1. The IR spectra obtained in this study were divied into three categories: spectra of humic acids from grain crop straws of rice, barley, wheat and rye produced Type I, while that from wild grass hay yielded Type II, and those from forest tree litter of the deciduous and conifers were led to give Type III. 2. There were no significant changes in the absorption bands observed among humic acids extracted at various stages of decomposition of a given Plant material. 3. The absorption band at about $3,430cm^{-1}$ represents the presence of hydrogen-bonded hydroxyl groups, phenolic-OH groups being the major component. 4. A close relationship was found between the total acidity and the content of phenolic-OH groups of humic acids. The content of carboxyl groups maintains a direct relationship with the content of total hydroxyl groups, and such a close relationship also exists between the content of alcoholic hydroxyls and that of total hydroxyl groups. 5. Overlapping of the absorption bands of carbonyl groups and quinones renders it difficult to make differentiation between the two. 6. A variety of non-armoatic cyclic hydrocarbons appears to be a structural component as evidenced by a sharp absorption peak near $995-1000cm^{-1}$.