• Journal of Technologic Dentistry
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• v.35 no.3
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• pp.209-218
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• 2013

Purpose: The purpose of this study was to know the availability of two photosensitizers, PD, DA, as a photosensitizer instead of CQ in UDMA dental composite resin. We want to know photopolymerization effect of UDMA unfilled resin and surface hardness of composite resin containing PD and DA were compared with those of CQ, most widely used photosensitizer for dental composite resins. Methods: The photopolymerization effect of UDMA studied by FT-IR spectroscopy increased with irradiation time and the amount of photosensitizer. Knoop hardness of experimental composite resins prepared by the addition of the photosensitizer content and irradiation time. Results: The relative photopolymerization effect of UDMA increased in the order of PD > CQ > DA. The composite resin of UDMA containing DA or PD, which shows better Knoop hardness than that containing CQ. Conclusion: PD and DA show as effective photosensizers, suitable for UDMA dental composite resin compare with a higher efficiency than CQ.

• Journal of Technologic Dentistry
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• v.23 no.2
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• pp.49-59
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• 2002

The photopolymerization efficiency and surface hardness of composite resin containing 1,2-phenylpropanedione (PD) and diacetyl (DA) as photoinitiators were studied by IR and Vickers hardness and the results were compared with that of camphorquinone (CQ). Relative photopolymerization efficiency of the photoinitiators increased in the order of DA < CQ < PD. Vickers hardness of composite resin containing the photoinitiators increased in the order of CQ < PD < DA. Thus, PD is a new visible light photoinitiator for dental composite resin with higher photopolymerization efficiency and surface hardness than that of CQ. Mechanical properties such as Vickers hardness, diametral tensile strength, and flexural strength of the experimental resin composite prepared by addition of the photosensitizer into a resin of bis-GMA improved with increasing the photosensitizer content and irradiation time. The resin composite of bis-GMA containing DA or PD shows better mechanical properties than that of CQ.

• Journal of Technologic Dentistry
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• v.35 no.4
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• pp.313-320
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• 2013

Purpose: The purpose of this study was to know the physical properties of UDMA dental composite resins containing two photosensitizers, PD, DA, as a photosensitizer instead of CQ. We want to know Remaining Double Bond(RDB) of UDMA unfilled resin and diametral tensile strength and flexural strength of composite resin containing PD and DA were compared with those of CQ, most widely used photosensitizer for dental composite resins. Methods: The RDB of UDMA studied by FT-IR spectroscopy increased with irradiation time. The composite resins were tested for their physical properties. The dental composite resins were made with UDMA as a monomer, silanized silica as filler, N,N-dimethylaminoethyl methacrylate (DAEM) as amine initiator, and one of the two kinds of new photosensitizers. Results: The relative RDB of UDMA was in the order: DA > CQ > PD but the physical properties of the composite resins show PD and DA with higher results compared with that containing CQ. The reason for the results is that PD and DA serve not only as a photosensitizer but also as a photo-crosslinking agent. Conclusion: PD and DA show as effective photosensizers, suitable for UDMA dental composite resin compare with a higher efficiency than CQ.

• Restorative Dentistry and Endodontics
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• v.17 no.1
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• pp.153-165
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• 1992

Dental composite resin is a kind of the particle - reinforced composite material, and is widely used in recent dental restoration of anterior and posterior tooth region. The purpose of this study was to investigate the fracture behaviour according to volume fractions and external findings of the filler particles for better interpretation of the fracture characteristics of posterior dental composite resins by analytic method of fracture mechanics. The plane strain fracture toughness($K_{IC}$) and Acoustic Emission were determined with three - point bending test using the single edge notch specimen according to the ASTM - E399, and its analyzed data was compared with filler volume fractions derived from the standard ashing test and scanning electron fractographs of each specimen including the unfilled experimental resin as a control. The results were that the value of fracture toughness of the composite resin material was in the range from 0.85 MPa$\sqrt{m}$ to 1.60 MPa$\sqrt{m}$ and was higher than the value of the unfilled experimental resin, and the fracture behaviours dervied from Acoustic Emission analysis show prominent differences according to the volume fraction and the size of filler particles used in each composite resin. The degree of resistance against crack propagation seems to be increase and the fractographs demonstrate the high degree of surface roughness and irregularity according with the increase of fracture toughness value.

• The Journal of Korean Academy of Prosthodontics
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• v.37 no.3
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• pp.313-327
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• 1999

The aim of this study was to compare wear resistance of resin denture teeth opposing various restorative materials. The wear resistance of conventional acrylic resin teeth(Trubyte Biotone) and three high-strength resin teeth(Bioform IPN, Endura, SR-Orthosit-PE) opposing different restorative materials(gold alloys, dental porcelain, composite resin) was compared. Wear tests were conducted with a sliding-induced wear testing apparatus which applied 100,000 strokes to the specimen in a mesio-distal direction under conditions of 100 stroke/min and constant loading of 1Kgf/tooth. Wear resistance of the resin denture teeth was evaluated by the following criteria : 1) wear depth, 2) weight loss, and 3) SEM observation. Results were as follows. 1. When opposed to gold alloys and composite resin, high-strength resin teeth showed superior wear resistance compared to acrylic resin teeth. But, in cases opposing dental porcelain, differences between the wear of the high-strength and acrylic resin teeth were not statistically significant (p<0.05). 2. When comparing wear resistance among high-strength resin teeth, opposing gold alloys, Endura was slightly more resistant and while in cases opposing dental porcelain, SR-Orthosit-PE was showed to be slightly resistant(p<0.05). 3. The wear of high-strength resin teeth was greater by 5 to 7 times when opposing porcelain and 2 to 3 times when opposing composite resin compared to gold alloys(p<0.05). 4. SEM observations of the wear surface showed that wear of resin teeth opposing gold alloys is a fatigue type of wear and wear of resin teeth opposing dental porcelain is fatigue and abrasion type of wear. Trubyte Biotone showed more severe fatigue type of wear than high-strength resin teeth. In conclusion, the use of dental porcelain should seriously be considered as restorative material in cases opposing resin denture teeth and improvement seems to be needed on resin teeth in the areas of wear resistance.

• The Journal of the Korean dental association
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• v.50 no.7
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• pp.368-376
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• 2012

The demand for tooth-colored restorations has grown considerably during the last decade. Posterior composite restorations have risen in popularity as a result of the development of improved resin composites, bonding systems and operating techniques. A major limitation of direct composite restoration is the difficulty of controlling the polymerization shrinkage. To overcome this limitation, the indirect fabrication of a composite restoration and cementation with resin cement has been advocated. Unfortunately, the current available resin cements with indirect restorations do not always bond to dentin as strongly as dentin adhesive systems bond with direct resin composite restorations. Several procedural strategies have been proposed for indirect composite restoration. In this regard, the rationale for the indication, characteristics and clinical application is described in this paper. As a result, we will try to suggest the evidence-based guidelines for indirect composite restorations by reviewing each available indirect composite products, technical procedure and pronosis.

• Polymer(Korea)
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• v.28 no.4
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• pp.321-327
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• 2004

The applications of dental restorative composite resins containing 2,2-bis [4-(2-hydroxy-3-me-thacryloyloxy propoxy) phenyl] propane as a base resin, and triethylene glycol dimethacrylate, as a diluent, were often limited in dentistry due to the relatively large amount of volumetric shrinkage that occurs during the curing reaction. In this study, in order to reduce volumetric shrinkage of the current dental restorative composite resin, asymmetric spiro orthocarbonates were synthesized and then the characteristics of resin composites containing them were explored. The volumetric shrinkage of the dental composites containing spiro orthocarbonates was decreased approximately 45%. However, the curing characteristics and mechanical properties of the new dental composites were slightly poor than those of the commercially available dental composite.

• Journal of Technologic Dentistry
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• v.30 no.2
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• pp.23-29
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• 2008

The purpose of this study is to evaluate possibility of using indirect composite resin instead of porcelain through the measurement of shear bond strength between zirconia core and indirect composite resin under treatment of $Rocatec^{TM}$ system for improving the adhesion of indirect composite resin. 20 cylindrical zirconia core specimens were divided into 2 groups, according to zirconia surface treatment and attached materials: 1) treated with sandblast and attached with indirect composite resin, 2) treated with sandblast + $Rocatec^{TM}$ system and attached with indirect composite resin. The shear bond strength of each experimental group was measured by MTS and the changes of zirconia core surface according to surface treatments were obtained by SEM observation and measurements of surface roughness. The mean shear bond strength values are $0.55\;{\pm}\;0.11MPa$(Group SC) and $1.16\;{\pm}\;0.46MPa$(Group SRC). The mean Ra values for the surface treatments were follows: $0.39\;{\pm}\;0.13$($100{\beta}_{{\mu}m}$ sandblast) and $0.50\;{\pm}\;0.03$($100{\beta}_{{\mu}m}$ sandblast + $Rocatec^{TM}$ system). In the analysis of EDS, Si element was detected in the Group SC. The shear bond strength between zirconia core and indirect composite resin was improved significantly by using $Rocatec^{TM}$ system.

• Polymer(Korea)
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• v.33 no.2
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• pp.153-157
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• 2009

The resin matrix in the dental composite is generally composed of 2,2-bis[4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl] propane (Bis-GMA) as a base resin and triethylene glycol dimethacrylate (TEGDMA) as a diluent for the reduction of viscosity. The applications of dental composite were often limited in dentistry due to the relatively large amounts of volumetric shrinkage during polymerization and water uptake caused by the addition of TEGDMA to the resin matrix. In this study, in order to solve problems stemmed from the TEGDMA by reducing amount of diluent added to resin matrix, diethylene glycol dimethacrylate (DEGDMA) and ethylene glycol dimethacrylate (EGDMA) were explored as new diluents. A decrease in the volumetric shrinkage and an increase in the mechanical strength were observed by replacing TEGDMA in the dental composite to DEGDMA (or EGDMA). Reduction in the mechanical strength of the dental composite containing DEGDMA (or EGDMA), was not serious in comparison with that of the dental composite containing TEGDMA after water uptake.

• Journal of Technologic Dentistry
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• v.38 no.3
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• pp.135-142
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• 2016

Purpose: The aim of this research was to evaluate the influence of different surface treatments on the shear bond strength of zirconia ceramic to composite resin. Methods: Seventy two cylinder-shape (diameter: 5 mm; height: 12 mm) blocks of experimental industrially manufactured Y-TZP ceramic were abraded with $125{\mu}m\;Al_2O_3$ particles and randomly divided into 4 groups. All the materials were categorized as group Gc(control group - composite resin veneering on zirconia surface), Gr - composite resin veneering after surface treatment of Rocatec system (3M ESPE, Seefeld, Germany) group; Gz - composite resin veneering after surface treatment of Zirconia primer (Z-primer, Bisco, U.S.A) group; Gm - composite resin veneering after surface treatment of zirconia primer (Monobond plus, ivoclar vivadent AG, Liechtenstein) group. Two different zirconia primers and Rocatec system were used to zirconia cylinders (n=16) onto the zirconia surface. Zirconia specimens, polished and roughened, were pretreated and composite bilayer cylinders bonded using conventional adhesive techniques. Results: Shear bond strengths were analyzed using single-factor ANOVA(p<0.05). Bond strength values achieved after airbone particle abrasion and zirconia surface pre-treatments(p<0.05). Conclusion: Shear bond strength tests denmonstrated that zirconia primer is a viable method to improved bond strength between zirconia ceramic core and veneering composites.