• Korean Journal of Dental Materials
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• v.44 no.4
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• pp.311-318
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• 2017

The purpose of this study was to examine the effects of the curing sequence and polymerization temperature on the flexural strength and microhardness of two provisional resins (Bis-acryl resin composite and polymethyl methacrylate (PMMA)). Polymerization was carried out under various conditions, in air at $25^{\circ}C$ (control) and in hot water (40, 50, 60, 70, and $80^{\circ}C$). The flexural strength test was conducted according to ISO-4049. The Knoop hardness was measured. For the Bis-acryl resin, the temperature up to $50^{\circ}C$ did not increase the flexural strength nor the hardness of the bis-acryl resin composite (p>0.05) but higher temperatures increased the strengths. For the PMMA resin, flexural strength increased with temperatures up to $70^{\circ}C$ and then decreased slightly. Bis-acryl resin composite had higher mechanical properties than the PMMA resin. The effect of heat was more pronounced in the bis-acryl resin composite than in the PMMA resin (p<0.05).

• Restorative Dentistry and Endodontics
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• v.43 no.2
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• pp.22.1-22.9
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• 2018

Objectives: To evaluate and compare light-transmittance in dental tissues and dental composite restorations using the incremental double-layer technique with varying layer thickness. Materials and Methods: B1-colored natural teeth slabs were compared to dental restoration build-ups with A2D and B1E-colored nanofilled, supra-nanofilled, microfilled, and microhybrid composites. The enamel layer varied from 0.3, 0.5, or 1.2 mm thick, and the dentin layer was varied to provide a standardized 3.7 mm overall sample thickness (n = 10). All increments were light-cured to $16J/cm^2$ with a multi-wave LED (Valo, Ultradent). Using a spectrophotometer, the samples were irradiated by an RGB laser beam. A voltmeter recorded the light output signal to calculate the light-transmittance through the specimens. The data were analyzed using 1-way analysis of variance followed by the post hoc Tukey's test (p = 0.05). Results: Mean light-transmittance observed at thicker final layers of enamel were significantly lower than those observed at thinner final layers. Within 1.2 mm final enamel resin layer (FERL) thickness, all composites were similar to the dental tissues, with exception of the nanofilled composite. However, within 0.5 mm FERL thickness, only the suprananofilled composite showed no difference from the dental tissues. Within 0.3 mm FERL thickness, none of the composites were similar to the dental tissues. Conclusions: The supra-nanofilled composite had the most similar light-transmittance pattern when compared to the natural teeth. However, for other composites, thicker FERL have a greater chance to match the light-transmittance of natural dental tissues.

• The Journal of Advanced Prosthodontics
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• v.5 no.4
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• pp.479-484
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• 2013

PURPOSE. The aim of this study was to evaluate the effects of additional acid etching and curing mechanism (light-curing or self-curing) of a composite resin on the dentin bond strength and compatibility of one-step self-etching adhesives. MATERIALS AND METHODS. Sixteen human permanent molars were randomly divided into eight groups according to the adhesives used (All-Bond Universal: ABU, Clearfil S3 Bond: CS3), additional acid etching (additional acid etching performed: EO, no additional acid etching performed: EX), and composite resins (Filtek Z-250: Z250, Clearfil FII New Bond: CFNB). Group 1: ABU-EO-Z250, Group 2: ABU-EO-CFNB, Group 3: ABU-EX-Z250, Group 4: ABU-EX-CFNB, Group 5: CS3-EO-Z250, Group 6: CS3-EO-CFNB, Group 7: CS3-EX-Z250, Group 8: CS3-EX-CFNB. After bonding procedures, composite resins were built up on dentin surfaces. After 24-hour water storage, the teeth were sectioned to make 10 specimens for each group. The microtensile bond strength test was performed using a microtensile testing machine. The failure mode of the fractured specimens was examined by means of an optical microscope at ${\times}20$ magnification. The data was analyzed using a one-way ANOVA and Scheffe's post-hoc test (${\alpha}$=.05). RESULTS. Additional etching groups showed significantly higher values than the no additional etching group when using All-Bond Universal. The light-cured composite resin groups showed significantly higher values than the self-cured composite resin groups in the Clearfil S3 Bond. CONCLUSION. The additional acid etching is beneficial for the dentin bond strength when using low acidic one-step self-etch adhesives, and low acidic one-step self-etch adhesives are compatible with self-cured composite resin. The acidity of the one-step self-etch adhesives is an influencing factor in terms of the dentin bonding strength and incompatibility with a self-cured composite resin.

• Restorative Dentistry and Endodontics
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• v.38 no.1
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• pp.36-42
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• 2013

Objectives: This study evaluated the antibacterial effect and mechanical properties of composite resins ($L_{CR}$, $M_{CR}$, $H_{CR}$) incorporating chitosan with three different molecular weights (L, Low; M, Medium; H, High). Materials and Methods: Streptococcus (S). mutans 100 mL and each chitosan powder were inoculated in sterilized 10 mL Brain-Heart Infusion (BHI) solution, and was centrifuged for 12 hr. Absorbance of the supernatent was measured at $OD_{660}$ to estimate the antibacterial activities of chitosan. After S. mutans was inoculated in the disc shaped chitosan-containing composite resins, the disc was cleansed with BHI and diluted with serial dilution method. S. mutans was spread on Mitis-salivarius bacitracin agar. After then, colony forming unit (CFU) was measured to verify the inhibitory effect on S. mutans biofilm. To ascertain the effect on the mechanical properties of composite resin, 3-point bending and Vickers hardness tests were done after 1 and 3 wk water storage, respectively. Using 2-way analysis of variance (ANOVA) and Scheffe test, statistical analysis was done with 95% significance level. Results: All chitosan powder showed inhibition effect against S. mutans. CFU number in chitosan-containing composite resins was smaller than that of control resin without chitosan. The chitosan containing composite resins did not show any significant difference in flexural strength and Vickers hardness in comparison with the control resin. However, the composite resin, $M_{CR}$ showed a slightly decreased flexural strength and the maximum load than those of control and the other composite resins $H_{CR}$ and $L_{CR}$. Conclusions: $L_{CR}$ and $H_{CR}$ would be recommended as a feasible antibacterial restorative due to its antibacterial nature and mechanical properties.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.29 no.2
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• pp.92-102
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• 2020

Bond-Fill SB is made of powder/liquid, and the flowability can be controlled by adjusting the amount of liquid in the brush. Thanks to the strong catalyst called TBB, it has the advantage of being able to polymerize even in the presence of water and oxygen. Also, since it contains 4-META, it has the advantage of being able to adhere to metals and ceramics with appropriate surface treatment. If you fully understand these advantages, you can actively utilize them in cases where it is difficult to treat with conventional composite resin.

• Composites Research
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• v.28 no.1
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• pp.6-14
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• 2015

Polymerization shrinkage stress analysis of dimethacrylate-based composite (Clearfil AP-X, Kuraray) and silorane-based composite (Filtek P90, 3M ESPE) used for dental composite restorations was performed using strain-gage measurement and FEM analysis. A theoretical equation based on Young's modulus and polymerization shrinkage of the composite resin was proposed to predict the polymerization shrinkage stress. Experimental results showed that the maximum shrinkage stress of Clearfil AP-X was about 2.8 times higher than Filtek P90. FEM analysis agreed with such experimental stress behaviours and showed that the maximum Von-Mises stress appeared near the margin of the filled resin adhered with PMMA ring. The stress concentration at the interface on the specimen surface was higher than that in the interior. The maximum error of shrinkage stress by the theoretical equation was reasonable within 5% in comparison to FEM results under plane stress.

• The Journal of Korean Academy of Prosthodontics
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• v.37 no.5
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• pp.620-639
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• 1999

Indirect composite resins are used as an popular effective esthetic material in prosthetic dentistry, often with metallic substructure that provides support for restorations. Recently, new indirect composite resins as a substitute of ceramic have been developed. These resins provide good esthetics, with a wide range of hue and chroma. And the flexural strength of those is in the range of 120-150MPa, Which is higher than that of feldspathic Ceramic, and similar th that of Dicor. Although it has many merits, one of the major clinical problems of composite resins is the bond failure between metal and resin due to insufficient interfacial bond strength. The purpose of this study was to evaluate shear bond strength of the reinforced indirect composite resin to dental alloys. Three different composite resin systems($Artglass^{(R)},\;Sculpture^{(R)},\;Targis^{(R)}$) as test groups and ceramic($VMK\;68^{(R)}$) as control group were bonded to Ni-Cr-Be alloy($Rexillium\;III^{(R)}$) and gold alloy(Deva 4). All specimens were stored at $^37{\circ}C$ distilled water for 24 hours and the half of specimens were thermocycled 2000 times at temperature from $5^{\circ}C\;to\;60^{\circ}C$. The shear bond strengths of reinforced indirect composite resins to dental alloys were measured by using the universal testing machine, and modes of debonding were observed by stereoscope and scanning electron microscope. The results were as follows: 1 The shear bond strengths of reinforced indirect composite resins to dental alloys were approximately half those of ceramic to dental alloys(P<0.01). 2. There was no significant difference between the shear bond strength of several reinforced indirect composite resins to metal. 3. Alloy type did not affect on the shear bond strengths of resin to metal, but the shear bond strengths of ceramic to gold alloys were higher than those of ceramic to Ni-Cr alloys(P<0.05). 4. The shear bond strengths of Artglass and Targil to gold alloys were significantly decreased after thermocycling treatment(P<0.01). 5. Sculpture showed cohesive, adhesive, and mixed failure modes, but Artglass and Targis showed adhesive or mixed failures. And ceramic showed cohesive and mixed failures.

• Restorative Dentistry and Endodontics
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• v.45 no.1
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• pp.12.1-12.8
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• 2020

Objectives: The aim of this in vitro study was to evaluate the microhardness and surface roughness of composite resins before and after tooth bleaching procedures. Materials and Methods: Sixty specimens were prepared of each composite resin (Filtek Supreme XT and Opallis), and BisCover LV surface sealant was applied to half of the specimens. Thirty enamel samples were obtained from the buccal and lingual surfaces of human molars for use as the control group. The surface roughness and microhardness were measured before and after bleaching procedures with 35% hydrogen peroxide or 16% carbamide (n = 10). Data were analyzed using 1-way analysis of variance and the Fisher test (α = 0.05). Results: Neither hydrogen peroxide nor carbamide peroxide treatment significantly altered the hardness of the composite resins, regardless of surface sealant application; however, both treatments significantly decreased the hardness of the tooth samples (p < 0.05). The bleaching did not cause any change in surface roughness, with the exception of the unsealed Opallis composite resin and dental enamel, both of which displayed an increase in surface roughness after bleaching with carbamide peroxide (p < 0.05). Conclusions: The microhardness and surface roughness of enamel and Opallis composite resin were influenced by bleaching procedures.

• Journal of the korean academy of Pediatric Dentistry
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• v.37 no.4
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• pp.438-444
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• 2010

Giomer is a recently developed light-cured resin-based material. This study compared compressive strength and microhardness of composite resin, giomer and compomer after 5000 times of thermocycling at $5^{\circ}C$ and $55^{\circ}C$. The following results were obtained. 1. Composite resin resulted in the highest compressive strengths both before and after thermocycling, followed by giomer and compomer. There were statistically significant differences between composite resin and giomer/compomer (p<0.05), but no statistically significant differences between giomer and compomer. 2. Both before and after thermocycling, microhardness values appeared in the order of composite resin, giomer and compomer with statistically significant differences in microhardness of composite resin, giomer and compomer (p<0.05). 3. After thermocycling, microhardness of composite resin, giomer and compomer decreased with a statistically significant difference (p<0.05). In conclusion, giomer demonstrates higher microhardness than compomer, but lower compressive strength and microhardness than composite resin. In addition, the decrease in microhardness and compressive strength after thermocycling proves the necessity for a thorough understanding in mechanical properties of restoration materials prior to their clinical application.

• The Journal of the Korean dental association
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• v.54 no.1
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• pp.16-20
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• 2016

There is a difficulty for many practioner in anterior direct restroation with composit resin. Because its result is various according to patient, a practioner have a fear about that unpromisable result. Moreover in esthetic region, there is difference in satisfaction by patient character. That is one of difficulty in this practice. But if we make a manual for parctice it will be easier. So I will summarize the process and things to note in direct anterior composite resin restoration.