• The Journal of Advanced Prosthodontics
• /
• v.14 no.5
• /
• pp.305-314
• /
• 2022

PURPOSE. The aim of this study was to evaluate the flexural strength of a 3D-printed denture base resin (Cosmos Denture), after different immediate repair techniques with surface treatments and thermocycling. MATERIALS AND METHODS. Rectangular 3D-printed denture base resin (Cosmos Denture) specimens (N = 130) were thermocycled (5,000 cycles, 5℃ and 55℃) before and after the different repair techniques (n = 10 per group) using an autopolymerized acrylic resin (Jet, J) or a hard relining resin (Soft Confort, SC), and different surface treatments: Jet resin monomer for 180 s (MMA), blasting with aluminum oxide (JAT) or erbium: yttrium-aluminum-garnet laser (L). The control group were intact specimens. A three-point flexural strength test was performed, and data (MPa) were analyzed by ANOVA and Games-Howell post hoc test (α = 0.05). Each failure was observed and classified through stereomicroscope images and the surface treatments were viewed by scanning electron microscope (SEM). RESULTS. Control group showed the highest mean of flexural strength, statistically different from the other groups (P < .001), followed by MMA+J group. The groups with L treatment were statistically similar to the MMA groups (P > .05). The JAT+J group was better than the SC and JAT+SC groups (P < .05), but similar to the other groups (P > .05). Adhesive failures were most observed in JAT groups, especially when repaired with SC. The SEM images showed surface changes for all treatments, except JAT alone. CONCLUSION. Denture bases fabricated with 3D-printed resin should be preferably repaired with MMA+J. SC and JAT+SC showed the worst results. Blasting impaired the adhesion of the SC resin.

• Restorative Dentistry and Endodontics
• /
• v.33 no.1
• /
• pp.1-8
• /
• 2008

The purpose of this study was to evaluate the effect of a new resin monomer, filler size and polishing technique on the surface roughness of composite resin restorations using confocal laser scanning microscopy. By adding new methoxylated Bis-GMA (Bis-M-GMA, 2,2-bis[4-(2-methoxy-3-methacryloyloxy propoxy) phenyl] propane) having low viscosity, the content of TEGDMA might be decreased. Three experimental composite resins were made: EX1 (Bis-M-GMA/TEGDMA = 95/5 wt%, 40 nm nanofillers); EX2 (Bis-M-GMA/TEGDMA = 95/5 wt%, 20 nm nanofillers); EX3 (Bis-GMA/TEGDMA = 70/30 wt%, 40 nm nanofillers). Filtek Z250 was used as a reference. Nine specimens (6 mm in diameter and 2 mm in thickness) for each experimental composite resin and Filtek Z250 were fabricated in a teflon mold and assigned to three groups. In Mylar strip group, specimens were left undisturbed. In Sof-lex group, specimens were ground with #1000 SiC paper and polished with Sof-lex discs. In DiaPolisher group, specimens were ground with #1000 SiC paper and polished with DiaPolisher polishing points. The Ra (Average roughness), Rq (Root mean square roughness), Rv (Valley roughness), Rp (Peak roughness), Rc (2D roughness) and Sc (3D roughness) values were determined using confocal laser scanning microscopy. The data were statistically analyzed by Two-way ANOVA and Tukey multiple comparisons test (p = 0.05). The type of composite resin and polishing technique significantly affected the surface roughness of the composite resin restorations (p < 0.001). EX3 showed the smoothest surface compared to the other composite resins (p < 0.05). Mylar strip resulted in smoother surface than other polishing techniques (p < 0.05). Bis-M-GMA. a new resin monomer having low viscosity, might reduce the amount of diluent, but showed adverse effect on the surface roughness of composite resin restorations.

• Restorative Dentistry and Endodontics
• /
• v.24 no.1
• /
• pp.88-99
• /
• 1999

The purpose of this study was to investigate the physical properties of experimental composite resins made with the spherical and crushed fillers. The 14 experimental composite resins containing 0, 5, 10, 15, 20 and 25%(w/w) in spherical filler group and 0, 10, 20, 30, 40, 50, 60 and 70%(w/w) in crushed filler group, incorporated in a Bis-GMA matrix (Aldrich Co., USA), were made with 1% ${\gamma}$-methoxy silane treated fillers. The polymer matrix was made by dissolving 0.7%(w/w) of benzoyl peroxide(Janssen Chemical Co. Japan) in methacrylate monomer, whereupon 0.7%(v/v) N,N-dimethyl-p-toluidine(Tokyo Kasei Co. Japan) was added to the monomer. The weight percentage of each specific particle size distribution could be determined from a knowledge of the specific gravity, the weight(w/w), and corresponding volume %(v/v) of the filler sample in resin monomer. In crushed silica group and spherical silica group, the diametral tensile strengths and compressive strengths were measured with Instron Testing Machine(No.4467), and analyzed in 14 experimental composite resins made by filler fractions. The shear bond strength of 14 experimental composite resins to bovine enamel was measured with universal testing machine(Instron No.4467). The fracture surfaces were sputter-coated with a gold film and investigated by SEM. The results were as follows; 1. The diametral tensile strength was tendency to increase in crushed silica group, but not in spherical silica group. The highest diametral tensile strength was found in 20% filler fractions of two groups. 2. The compressive strength was higher in 15%(w/w) and 20%(w/w) in spherical silica group than in crushed silica group, but not in spherical silica group. 3. The significant correlation was noticed in increase in shear bond strength in crushed silica group, but not in spherical silica group. 4. The significantly highest shear bond strength was noticed in 50% filler concentration in crushed silica group, and in 15% filler concentration in spherical silica group, it was not significant in relation. 5. In crushed silica group, cut surface of resin matrix and the interface between resin and filler is obvious. In spherical silica group, fractures that occurred through the filler particles were round in shape.

• Polymer(Korea)
• /
• v.28 no.5
• /
• pp.426-432
• /
• 2004

To reduce volumetric shrinkage of the commercially available polymeric dental composite during curing reaction, (2,2-bis [4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl] propane) (bis -GMA) derivatives, i.e., (2,2-bis[3-methyl, 4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl] propan) (DMBis-GMA) and (2,2-his [3,5-dimethyl ,4- (2-hydroxy-3-methacryloyloxy propoxy) phenyl] propane) (TMBis-GMA) were synthesized and then new dental composite resin composed of Bis-GMA derivatives, diluent, spiro orthocarbonate (SOC), and inorganic filler was produced. Among the Bis-GMA derivative/Bis-GMA derivative/diluent mixtures, Bis-GMA/ TMBis-GMA/TEGDMA mixture exhibited the lowest volumetric shrinkage. Volumetric shrinkage of this mixture was further reduced by adding SOC. Volumtric shrinkage of dental composite prepared from commercially available resin monomer mixture was $2.5\%$, while that prepared from resin monomer mixture having minimum volumetric shrinkage was reduced to $0.7\%$. Mechanical strength of this dental composite was nearly the same with that of commercial products but the time required for the curing reaction was retarded.

• Journal of Korean Dental Science
• /
• v.2 no.2
• /
• pp.5-11
• /
• 2009

Objectives : This study investigated the hypothesis that the dentin bond strength of self-etching adhesives (SEAs) may be improved by applying a coat of hydrophobic, neutral adhesive resin in addition to SEA. Method and Materials : The bond strengths of two SEAs - Experimental SEA (EX) and Adper Prompt (AP) - were measured with three bonding protocols. The D/E resin of All-Bond 2 was applied as the hydrophobic, neutral adhesive. Clearfil SE Bond (SE, self-etching primer system) and All-Bond 2 (AB, total etching system) were used as references. The following protocols were used: (1) EX1 (EX 1 coat); (2) EX2 (EX 2 coats); (3) EX+ (EX 1 coat + D/E resin); (4) AP1 (AP 1 coat); (5) AP2 (AP 2 coats); (6) AP+ (AP 1 coat + D/E resin); (7) SE (SE primer + SE bond); (8) SE+ (SE primer + D/E resin); (9) AB (etching + AB primer + D/E resin). Filtek Z250 composite resin was built up and the microtensile bond strength (MTBS) values of the specimens were compared. The fractured surfaces were observed using SEM. Results : When SEA was used as self-etching primer and hydrophobic, neutral adhesive was applied as well, MTBS was significantly higher than that when either one coat or two coats of SEA only were used (p < 0.05). Conclusion : The hydrophobic, neutral adhesive improved the integrity of the bonded interface obtained with SEA.

• Restorative Dentistry and Endodontics
• /
• v.26 no.5
• /
• pp.399-408
• /
• 2001

Tooth bleaching has been prevailing recently for its ability to recover the color and shape of natural teeth without reduction of tooth material. However, it has been reported that bleaching procedure adversely affects the adhesive bond strength of composite resin to tooth. At the same time the bond strength was reported to be regained by application of some chemical agents. The purpose of this in vitro study was to investigate the effect of the removal of residual peroxide on the composite- enamel adhesion and also evaluated fracture mode between resin and enamel after bleaching. Sixty extracted human anterior and premolars teeth were divided into 5 groups and bleached by combined technique using of office bleaching with 35 % hydrogen peroxide and matrix bleaching with 10% carbamide peroxide for 4 weeks. After bleaching, the labial surfaces of each tooth were treated with catalase, 70% ethyl alcohol, distilled water and filled with composite resin. Shear bond strength was tested and the fractured surfaces were also examined with SEM. Analysis revealed significantly higher bond strength values. (p＜0.05) for catalase-treated specimens, but water-treated specimens showed reduction of bond strength, alcohol- treated specimens had medium value between the two groups(p＜0.05). The fracture mode was shown that the catalase group and the alcohol group had cohesive failure but the water sprayed group had adhesive failure. It was concluded that the peroxide residues in tooth after bleaching seems to be removed by gradual diffusion and the free radical oxygen from peroxide prevents polymerization by combining catalyst in the resin monomer. Therefore it may be possible to eliminate the adverse effect on the adhesion of composite resin to enamel after bleaching by using water displacement solution or dentin bonding agent including it for effective removal of residual peroxide.

• The Journal of Korean Academy of Prosthodontics
• /
• v.53 no.4
• /
• pp.318-324
• /
• 2015

Purpose: This study compared shear bond strengths of five self-adhesive cements with phosphate monomer to zirconium oxide ceramic with and without airborn particle abrasion. Materials and methods: One hundred zirconia samples were air-abraded ($50{\mu}mAl_2O_3$). One hundred composite resin cylinders were fabricated. Composite cylinders were bonded to the zirconia samples with either Permacem 2.0 (P), $Clearfil^{TM}$ SA Luting (C), $Multilink^{(R)}$ Speed (M), $RelyX^{TM}$ U200 Automix (R), G-Cem $LinkAce^{TM}$ (G). All bonded specimens were stored in distilled water ($37^{\circ}C$) for 24 h and half of them were additionally aged by thermocycling ($5^{\circ}C$, $55^{\circ}C$, 5,000 times). The bonded specimens were loaded in shear force until fracture (1 mm/min) by using Universal Testing Machine (Model 4201, Instron Co, Canton, MA, USA). The failure sites were inspected under field-emission scanning electron microscopy. The data was analyzed with ANOVA, Tukey HSD post-hoc test and paired samples t-test ($\alpha$=.05). Results: Before and after thermocycling, $Multilink^{(R)}$ Speed (M) revealed higher shear-bond strength than the other cements. G-Cem $LinkAce^{TM}$ (G) showed significantly lower bond strengths after thermocycling than before treatment (P<.05), but the other groups were not significantly different (P>.05). Conclusion: Most self-adhesive cements with phosphate monomer showed high shear bond strength with zirconia ceramic and weren't influenced by thermocycling, so they seem to valuable to zirconia ceramic bonding.

• Journal of the Korean Applied Science and Technology
• /
• v.35 no.3
• /
• pp.595-605
• /
• 2018

In recent years, researches on organic-inorganic coating films have conducted a nanocomposite system composed of organic resin matrices having excellent flexibility and chemical stability and inorganic materials having excellent mechanical properties. The o-phenylphenoxyethyl acrylate (OPPEA) used as the acrylate monomer has a high refractive index of 1.58, and the bisphenol A ethoxylate diacrylate (BAEDA) has a low refractive index but improves the chemical stability of the organic resin. In addition, zirconia used as an inorganic material exhibits excellent durability and optical properties. In this study, the BAEDA contents in acrylate monomer were controlled to produce a film with suitable optical transparency. And optimum conditions were established by comparing the changes in surface properties of PET films detected with pencil hardness tester, Abbe's refractometer, and UV-vis spectrophotometer. The hydrophobicity and the dispersibility of zirconia in acrylate monomer were much improved after modification with ${\gamma}$-methacryloxypropyltrimethoxysilane (MPS), which is a silane coupling agent. And the existence of ester C=O bond peak at $1716cm^{-1}$ introduced by MPS through FT-IR ATR spectrophotometer confirmed the completion of surface modification of zirconia with MPS. In addition, the presence of silicon atom on the surface modified zirconia was also proved using X-ray fluorescence spectrometer. When the photocurable hybrid coating was prepared by introducing chemically modified zirconia into acrylate monomer, the refractive index of this coated PET film was improved by 1.2%, compared to the only acrylate coated PET film. The homogeneous distribution of zirconia in acrylate coating layer on PET film was also identified through SEM/EDS mapping analysis technique.

• Proceedings of the PSK Conference
• /
• 2003.04a
• /
• pp.118.2-119
• /
• 2003

This study was undertaken to assess overall effects of bisphenol A, a monomer widely used in manufacturing polycarbonate plastics or epoxy resin, exposure on immune system of mice. For in vitro evaluation, serial concentration of SPA was added into culture of various immune cells from normal female ICR mice, and for in vivo or ex vivo assessment, mice were orally exposed to BPA dissolved in olive oil as doses of 500, 1000, 2000 mg/g b.w. for acute expose or 100, 500, 1000 mg/kg/day b.w. 5days a week for subacute exposure. (omitted)

• Proceedings of the Korea Concrete Institute Conference
• /
• 2009.05a
• /
• pp.497-498
• /
• 2009

Unsaturated polyester(UP) and epoxy resin require 8${\sim}$11 hours long harding times and heating systems used by reinforcement liner. This study is to evaluate the effects of low temperature harding property of UP with methyl methacrylate(MMA) monomer mixing proportions.