• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.1
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• pp.105-112
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• 2008

The purpose of this study was to evaluate the contact angle made by 3 kinds of self etching primers (Clearfil SE Bond, AdheSE, and Tyrian) on dentin and to measure the microtensile bond strength of resin composite to dentin using these self-etching primers. Contact angle between each of 3 self etching primers and polished dentin surface was measured (n=30) by contact angle analyzer and the result was analyzed by One-way ANOVA. For the measurement of microtensile bond strength, polished dentin surface was treated with each of 3 self etching primers and dentin adhesives. Z-250 composite resin was built-up with a height of 5 mm on the adhesive-treated surface and light cured for 40s with a halogen light curing unit. Thereafter, each tooth was sectioned into slabs perpendicular to the bonded interface and trimmed (n=45). The microtensile bond strength was measured with universal testing machine and the result was analyzed with Kruskal-Wallis test. AdheSE group showed the highest contact angle followed by Clearfil SE group and Tyrian group (p<0.05). AdheSE group and Clearfil SE group showed significantly higher microtensile bond strength than Tyrian group (P<0.05).

• The Journal of Korean Academy of Prosthodontics
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• v.36 no.3
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• pp.483-495
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• 1998

The purpose of this study was to evaluate the human pulpal response to Dentin Bonding Desensitizer. Class V cavities were prepared on the buccal surfaces of the first premolars and Dentin Bonding Desensitizer(ALL-BOND Desensitizer, Bisco, Inc. U.S.A.) was applicated in ten experimental teeth, or ZOE(PROPAC, GC Co. TOKYO, JAPAN) cement in eight control teeth and cavities were filled with light curing glass ionomer(Fuji II LC, GC Co., TOKYO, JAPAN). At 3-day and 25-day postoperative interval. pulpal response was observed and evaluated histologically with light microscope. The results were as follows. ; 1. At 3-day postoperative interval, the control teeth were grade 1 inflammatory cell response and grade 1 connective tissue response. 2. At 25-day postoperative interval, all control teeth were grade 1 inflammatory cell response and in three control teeth grade 1 connective tissue response were observed, and one teeth showed grade 2 connective tissue response. 3. At 3-day postoperative interval, the experimental teeth were grade 1 inflammatory cell response and grade 1 connective tissue response. Below the cavity, a few inflammatory cell(PMNs) in odontoblastic layer, increased blood vessels and pulpal cells were seen and this pulpal response was similar to control teeth. 4. At 25-day postoperative interval, in four experimental teeth grade 1 inflammatory cell response and grade 1 connective tissue response were observed, and one experimental teeth showed mild inflammatory response. 5. At 3-day and 25-day postoperative interval, no reparative dentin deposition was seen. 6. Both experimental and control group, pulpal response showed difference between 3 and 25-day of postoperative interval. In control teeth, increased predentin and pulpal cells were seen and in experimental teeth, congestion of blood vessels and increased pulpal cells were seen. In conclusion, the pulpal irritation due to this Dentin Bonding Desensitizer was not severe, and it was considered that the agent was not harmful to the human pulp.

• Journal of Conservation Science
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• v.34 no.3
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• pp.157-166
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• 2018

In this study, gelatin binding ability was increased by adding cross linking agent to improve adhesive characteristic of animal glue. Animal glue added genipin measured gel strength and viscosity, the structural analysis, the color retention degree, elution degree, and rupture strength. And the water resistance and ultraviolet light resistance with the addition of genipin were compared. As a result of the study, the gel strength and viscosity increased with the amount of genipin. As a result of the structural analysis, in gelatin, the absorption peak of the triple structure of collagen structurally stabilized was observed. As a result of the color retention degree, the film was observed because of the lowered brightness. The amount of elution glue was increased with addition of genipin at $50^{\circ}C$ distilled water condition and rupture strength has increased with the amount of genipin. In the water resistance and light fastness, there was no appearance before and after deterioration due to the addition of genipin. Based on the results of this study, it confirmed the adhesive characteristics of animal glue added genipin and examined the experimental method applicable for animal glue. After the addition of genipin, flexibility, re-solving, adhesive force, and curing speed, which are unique characteristics of glue, can be improved without disappearing, so it is expected that it will be applicable to production of animal glue and conservation of cultural heritage when homogeneous glue is secured.

• Restorative Dentistry and Endodontics
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• v.20 no.1
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• pp.193-213
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• 1995

The purpose of this study is to investigate a possible contribution of nonspecific esterases, which occur in the oral cavity, to the degradation of ester bonds in polymethacrylates. One of the problems connected with the use of composite resins for restorations is their inadequate resistance to wear. It has been shown that methacrylate hydrolysis can be catalyzed by enzymes and that a carboxylic hydrolase (porcine liver esterase) catalyzed the hydrolysis of several mono - and dimethacrylates. The softening effect on a BISGMA/TEGDMA polymer induced by hydrolase will accelerate the in vivo wear of the polymer. Porcine liver esterase (EC 3.1.1.1) 3.2 mol/L $(NH_4)_2$ $SO_4$ was obtained from Sigma Chemical Company. The esterase activity of one unit is defined as the amount of enzyme capable of hydrolyzing $l{\mu}mol$ ethyl butyrate per min at pH 8.0 AT $25^{\circ}C$. Phosphate buffer, 10mmol/L, pH 7.0, was made by adjustment of a solution of $Na_2HPO_4$ with $H_3PO_4$. Composite resins used in this study are Silux Plus, Z-100, Durafil VS, and Prisma APH. Cylindrical specimens, 14mm in diameter and 3mm thick, of Silux Plus, Z-100, Durafil VS, Prisma APH were polymerized under the celluloid strip. 60 specimens were divided into 2 groups. One group was emersed only in buffer solution, the other group was emersed in buffer and enzyme solution. Silux Plus and Z-100 were divided into 2 subgroups, one subgroup was cured only Visilux 2. And the other subgroup was cured Visilux 2 and Triaid II. Thereafter, specimens were polished to its best achievable surface according to manufacture's directions. The Vickers hardness of the specimens was measured after 1, 2, 4, 7, 9, 15, 50 days. The solutions were changed after each measurement. Composite resin surfaces were evaluated for the surface roughness with profilometer (${\alpha}$-step 200, Tencor instruments, USA) after 1 and 50 days. And then surfaces of specimens were pictured with stereosopy after 1 and 50 days. The results were as follows. 1. The surface hardness of Silux plus, durafil VS, and Prisma APH were decreased with time. But, the surface hardness of Z-100 was not decreased. 2. The surface hardness of all composite resins was decreased by esterase. 3. Composite resins, which were light-cured by Visilux 2 and concomitantly baked by oven, showed more hardened surface than light-cured by Visilux 2 only. 4. Significant surface changes were occured in Silux plus after esterase treatment.

• Restorative Dentistry and Endodontics
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• v.13 no.2
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• pp.337-348
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• 1988

The purpose of this study was to examine the fracture strength and characteristics of teeth with MOD cavity preparation. Freshly extracted sound maxillary premolars were cleaned and stored in normal saline solution $37^{\circ}C$ for 72 hours before experiments. The roots of teeth were embedded in a self-curing resin, and the exposed crown were maintained in a vertical position by a modelling wax in a brass ring. The MOD cavities were prepared with No. 57 carbide bur under high speed to a depth of 2.0mm and a width of 2.0mm(Fig.1). All the prepared teeth specimens were divided into 7 groups according to the mode of cavity form and restorative materials (Table 1, 2): Group I, unpreapred, intact teeth as control Group II, prepared cavity without restoration Group III, prepared teeth restored with amalgam Group IV, prepared teeth restored with composite resin (P-10) Group V, prepared teeth with beveled enamel margins restored with composite resin (P-10) Group VI, prepared teeth restored with light-cured composite resin (P-30) Group VII, prepard teeth with beveled enamel margins restored with light-cured composite resin (P-30) After placement of restorations, all of the specimens were stored in water at $37^{\circ}C$ for 72 hours before testing. All of the specimens were tested on the Instron Universal Testing machine (No. 6025) in order to evaluate the strength of fracture. One metal ball 5.0mm in diameter contacting the specimens parallel to the occlusal surface was used to in this study (Fig. 1). The fracture characteristics of the specimens were examined with naked eye and in the scanning electron microscope (JSM-20). The results obtained from this study were as follows: 1. The mean fracture strength was the highest in group VI and that in group II was the lowest. 2. The progress of crack of teeth propagated into the pulp cavity. 3. In case of the group of the restored teeth, the crack occurred to be accompanied with cuspal fracture. 4. The crack of restored teeth was initiated along the pulpo-axial line angle of the cavity.

• Journal of the Korean Academy of Esthetic Dentistry
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• v.27 no.2
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• pp.82-96
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• 2018

3D printing is a process of producing 3d object from a digital file in STL format by joining, bonding, sintering or polymerizing small volume elements by layer. The various type of 3d printing is classified according to the additive manufacturing strategies. Among the types of 3D printer, SLA(StereoLithography Apparatus) and DLP(Digital Light Processing) 3D printer which use polymerization by light source are widely used in dental office. In the previous study, a full-arch scale 3d printed model is less precise than a conventional stone model. However, in scale of quadrant arch, a 3d printed model is significantly precise than a five-axis milled model. Using $3^{rd}$ Party dental CAD program, full denture, provisional crowns and diagnostic wax-up model are fabricated by 3d printer in dental office. In Orthodontics, based on virtual setup model, indirect bracket bonding tray can be generated by 3d printer. And thermoforming clear aligner can be fabricated on the 3d printed model. 3D printed individual drilling guide enable the clinician to place the dental implant on the proper position. The development of layer additive technology enhance the quality of 3d printing object and shorten the operating time of 3D printing. In the near future, traditional dental laboratory process such as casting, denture curing will be replaced by digital 3D printing.

• Journal of the korean academy of Pediatric Dentistry
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• v.49 no.2
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• pp.149-157
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• 2022

The aim of this study was to evaluate the effects of erythrosine-mediated photodynamic therapy (PDT) on Streptococcus mutans biofilm recovery by counting its colony-forming units (CFUs) and via confocal laser scanning microscopy analysis at different time points following PDT. In PDT, photosensitizer was an erythrosine. S. mutans ATCC25175 biofilms were irradiated using an LED curing light. Chlorhexidine (CHX) was used as positive control. After each antimicrobial treatment, samples were cultured to allow biofilm recovery. Viability was measured by calculating the CFU counts after treatment and after every 3 hours for up to 24 hours. Immediately after treatment, the PDT and CHX groups showed equally significant decreases in S. mutans CFU counts compared to the negative control. After 12 hours of reculture, the PDT group showed no significant difference in the decrease in CFU count compared to the negative control, whereas the CHX group showed significantly lower CFU counts throughout the 24-hour period. Erythrosine-mediated PDT can effectively inhibit S. mutans biofilm formation. However, biofilm recovery occurred earlier in the CHX group after PDT. This study provides insights into the clinical effectiveness of PDT in preventing dental caries.

• Restorative Dentistry and Endodontics
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• v.27 no.2
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• pp.158-174
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• 2002

The aim of this study was to investigate the effect of light irradiation modes on polymerization shrinkage, degree of cure and microleakage of a composite resin. VIP$^{TM}$ (Bisco Dental Products, Schaumburg, IL, USA) and Optilux 501$^{TM}$ (Demetron/Kerr, Danbury, CT, USA) were used for curing Filtek$^{TM}$ Z-250 (3M Dental Products, St. Paul., MN, USA) composite resin using following irradiation modes: VIP$^{TM}$ (Bisco) 200mW/$\textrm{cm}^2$ (V2), 400mW/$\textrm{cm}^2$ (V4), 600mW/$\textrm{cm}^2$ (V6), Pulse-delay (200 mW/$\textrm{cm}^2$ 3 seconds, 5 minutes wait, 600mW/$\textrm{cm}^2$ 30seconds, VPD) and Optilux 501$^{TM}$ (Demetron/Kerr) C-mode (OC), R-mode (OR). Linear polymerization shrinkage of the composite specimens were measured using Linometer (R&B, Daejeon, Korea) for 90 seconds for V2, V4, V6, OC, OR groups and for up to 363 seconds for VPD group (n=10, each). Degree of conversion was measured using FTIR spectrometer (IFS 120 HR, Bruker Karlsruhe, Germany) at the bottom surface of 2 mm thick composite specimens V2, Y4, V6, OC groups were measured separately at five irradiation times (5, 10, 20, 40, 60 seconds) and OR, VPD groups were measured in the above mentioned irradiation modes (n=5 each). Microhardness was measured using Digital microhardness tester (FM7, Future-Tech Co., Tokyo, Japan) at the top and bottom surfaces of 2mm thick composite specimens after exposure to the same irradiation modes as the test of degree of conversion(n=3, each). For the microleakage test, class V cavities were prepared on the distal surface of the ninety extracted human third molars. The cavities were restored with one of the following irradiation modes : V2/60 seconds, V4/40 seconds, V6/30 seconds, VPD , OC and OR. Microleakage was assessed by dye penetration along enamel and dentin margins of cavities. Mean polymerization shrinkage, mean degree of conversion and mean microhardness values for all groups at each time were analyzed using one-way ANOVA and Duncan's multiple range test, and using chi-square test far microleakage values. The results were as follows : . Polymerization shrinkage was increased with higher light intensity in groups using VIP$^{TM}$ (Bisco) : the highest with 600mW/$\textrm{cm}^2$, followed by Pulse-delay, 400mW/$\textrm{cm}^2$ and 200mW/$\textrm{cm}^2$ groups, The degree of polymerization shrinkage was higher with Continuous mode than with Ramp mode in groups using Optilux 501$^{TM}$ (Demetron/Kerr). . Degree of conversion and microhardness values were higher with higher light intensity. The final degree of conversion was in the range of 44.7 to 54.98% and the final microhardness value in the range of 34.10 to 56.30. . Microleakage was greater in dentin margin than in enamel margin. Higher light intensity showed more microleakage in dentin margin in groups using VIP$^{TM}$ (Bisco). The microleakage was the lowest with Continuous mode in enamel margin and with Ramp mode in dentin margin when Optilux 501$^{TM}$ (Demetron/Kerr) was used.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.3
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• pp.516-526
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• 2004

Polymerization shrinkage of photoinitiation type composite resin cause several clinical problems. The purpose of this study was to evaluate the shrinkage strain stress, linear polymerization shrinkage, compressive strength and microhardness of recently developed composite resins. The composite resins were divided into four groups according to the contents of matrix and filler type. Group I : $Denfil^{TM}$(Vericom, Korea) with conventional matrix, Group II : $Charmfil^{(R)}$(Dentkist, Korea) with microfiller and nanofller mixture, Group III : $Filtek^{TM}$ Z250(3M-ESPE, USA) TEGDMA replaced by UDMA and Bis-EMA(6) in the matrix, and Group IV : $Filtek^{TM}$ Supreme(3M-ESPE, USA) using pure nanofiller. Preparation of acrylic molds were followed by filling and curing with light gun. Strain gauges were attached to each sample and the leads were connected to a strainmeter. With strainmeter shrinkage strain stress and linear polymerization shrinkage was measured for 10 minutes. The data detected at 1 minute and 10 minutes were analysed statistically with ONE-way ANOVA test. To evaluate the mechanical properties of tested materials, compressive hardness test and microhardness test were also rendered. The results can be summarized as follows : 1. Filling materials in acrylic molds showed initial temporary expansion in the early phase of polymerization. This was followed by contraction with the rapid increase in strain stress during the first 1 minute and gradually decreased during post-gel shrinkage phase. After 1 minute, there's no statistical differences of strain stress between groups. The highest strain stress was found in group IV and followed by group III, I, II at 10 minutes-measurement(p>.05). In regression analysis of strain stress, group III showed minimal inclination and followed by group II, I, IV during 1 minute. 2. In linear polymerization shrinkage test, the composite resins in every group showed initial increase of shrinkage velocity during the first 1 minute, followed by gradually decrease of shrinkage velocity. After 1 minute, group IV and group III showed statistical difference(p<.05). After 10 minutes, there were statistical differences between group IV and group I, III(p<.05) and between group II and group III(p<.05). In regression analysis of linear polymerization shrinkage, group II showed minimal inclination and followed by group IV, III, I during 1 minute. 3. In compressive strength test, group III showed the highest strength and followed by group II, IV, I. There were statistical differences between group III and group IV, I(p<.05). 4. In microhardness test, upper surfaces showed higher value than lower surfaces in every group(p<.05).

• Journal of the korean academy of Pediatric Dentistry
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• v.26 no.3
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• pp.520-527
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• 1999

For the purpose of providing some suggestions in selection of filling materials used in 'sandwich technique', the bond strengths between glass ionomer cement bases and composite resins were investigated and compared. For lining materials, 'Vitrebond' and 'Ketac-fil' were used. Using these two as bases, 10 of each following resins were built up on the top ; Z-100 (light curing resin) Clear-fil (chemical curing resin), Bis-core (dual cure resin), Dyract (compomer), therfore 10 specimens of each group and total of 80 specimens were made. After storing specimens in $37^{\circ}C$ deionized water for 24 hours, the shear bond strengths were measured under universal testing machine with 50 kg of full load scale and 1mm/min of cross-head speed and obtained the results as follows : 1. Over Vitrebond base, Z-100 showed the lowest bond strength but the other three did not show any difference in bond strength. 2. Over Ketac-fil base, Clear-fil showed the highest bond strength followed by Dyract, Bis-core, and Z-100 showed the lowest bond strengths. 3. Whereas Clear-fil showed the similar bond strengths on the Vitrebond base as other resins, it showed the highest bond strength on Ketac-fil base, which showed some difference in bond strength by differing GIC bases. 4. The bond strengths between base materials and composite resin showed a stronger resin-dependence tendency in cases with Ketac-fil bases rather than with Vitrebond bases.