• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.2
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• pp.238-244
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• 2003

With the purpose of evaluating the effect of ailing amount of pit and assure sealants on the microleakage, 6 groups of specimens with different filling amount, filling materials and surface pretreatment were investigated. Sixty permanent third molars were divided into three groups. The occlusal surface of each tooth was divided into two parts; the filing width of one part was below 1mm (group1, 3, 5), and in the other part more than 2mm (group 2, 4, 6) Group 1 and 2: Helioseal F was applied directly to etched enamel; Group 3 and 4: Helioseal F was applied to etched and scotchbond Multi-purpose plus pre-treated enamel; Group 5 and 6: Tetric Flow was applied. After 500 times thermocycling and dye infiltration, we evaulated the microleakage. The results were as follows; 1. The mean microleakage score at each width were increased in the following order;group 5<3<1, and group 6<4<2. 2. In comparing the groups with same material and surface pretreatment but with different filling width (group 1 versus 2, 3 versus 4, 5 versus 6), the microleakage scores were significantly different. 3 The microleage was affected by filling amount of pit and assure sealants than Oiling materials and dentin bonding agent pretreatment.

• Restorative Dentistry and Endodontics
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• v.35 no.4
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• pp.257-266
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• 2010

The purpose of this study was to determine the effect of post types and sizes on fracture resistance in immature tooth model with various restorative techniques. Bovine incisors were sectioned 8 mm above and 12 mm below the cementoenamel junction to simulate immature tooth model. To compare various post-and-core restorations, canals were restored with gutta-percha and resin core, or reinforced dentin wall with dual-cured resin composite, followed by placement of D.T. LIGHT-POST, ParaPost XT, and various sizes of EverStick Post individually. All of specimens were stored in the distilled water for 72 hours and underwent 6,000 thermal cycles. After simulation of periodontal ligament structure with polyether impression material, compressive load was applied at 45 degrees to the long axis of the specimen until fracture was occurred. Experimental groups reinforced with post and composite resin were shown significantly higher fracture strength than gutta-percha group without post placement (p < 0.05). Most specimens fractured limited to cervical third of roots. Post types did not influence on fracture resistance and fracture level significantly when cement space was filled with dual-cured resin composite. In addition, no statistically significant differences were seen between customized and standardized glass fiber posts, which cement spaces were filled with resin cement or composite resin individually. Therefore, root reinforcement procedures as above in immature teeth improved fracture resistance regardless of post types and sizes.

• The Journal of Korean Academy of Prosthodontics
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• v.35 no.4
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• pp.647-661
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• 1997

The resin modified glass ionomer cements(RMGICs) have been used for years since 1989. Recently it has been developed for luting of fixed restorations. To evaluate the bond strength and marginal leakage of RMGICs for luting usage, the 80 extracted human molars which had uniform area of exposed dentin were cemented with 3 types of RMGICs(Fuji Duet, Advance, Vitremer), a conventional Glass Ionomer Cement(GIC-Fuji I), and a resin cement (Panavia 21) to base metal alloy(Ni-Cr-Be). After thermocycling the specimens were immersed in basic fuschin dye for measuring marginal leakage. The shear bond strength was measured with Instron and the maximum dye penetration was measured to 0.1mm. The types of fractured patterns were determined with stereoscope(${\times}7.5$). The results are as follows. 1. The difference between 3 RMGICs and a conventional GIC in shear bond strength was not statistically significant. It seemed that RMGICs had lower shear bond strength than resin cement. (p<0.01) 2. The mean scores of marginal leakage had no significant difference between the resin cement and 3 RMGICs but it was much higher in conventional GIC than the RMGICs (p<0.05) 3. It was determined that the manufacturer and the methods of dentin pretreatment determined the pattern of fracture surfaces and the frequency of adhesive failure between teeth and 3 RMGICs standed as in following order - Vitremer, Advance, Fuji Duet. (p<0. 01) When the fracture pattern was analyzed, it could be said that the materials and the method of dentin pretreatment have much effect on bonding states. This means that the dentin bonding agents should be improved. But the limited products in this experiment can not evaluate the physical properties of the entire RMGICs. Therefore a further study which can evaluate various RMGICs should be in progress to develope better cements.

• Journal of the korean academy of Pediatric Dentistry
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• v.26 no.4
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• pp.595-607
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• 1999

The purpose of this in vitro study was to evaluate the efficacy of self-etching primer which was developed to simplify the bonding procedures by measuring the shear bond strength and observing the interfacial morphology. 90 flat dentinal surfaces were prepared by grinding the buccal and lingual areas of caries-free human deciduous molars. After bonding of composite resin to sample surfaces according to the manufacturer's direction and thermocycling, shear bond strengths were measured using Universal testing machine(Instron). Another groups of specimens were treated by hydrochloric acid to secure the resin only and those tags were evaluated under SEM for their length and forms and the morphology of the bonding sites were also observed. The result as follows. 1. Group III showed higher shear bond strength than group I and II but no statistically significant difference was founded between group I and II(p>.05). 2. Adhesive failure was predominant in group II whereas dentin detachment was the main failure pattern in group I and III. 3. Relating long resin tags of $100-200{\mu}m$ were observed in samples of all groups under SEM. In group I, homogeneously long resin tags were arranged rather tight whereas rather loosely arranged resin tags of various length were found in group II. Lateral branching of resin tags was the characteristic finding observed in group III.

• Journal of the korean academy of Pediatric Dentistry
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• v.45 no.1
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• pp.90-97
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• 2018

The purpose of this study was to evaluate the effect of fissurotomy on the penetration and microleakage of flowable resins for carious fissures. A total of 250 extracted premolars with early fissure caries were selected and divided into five groups according to the fissurotomy; no fissurotomy (n = 50), fissurotomy with $Fissurotomy^{(R)}$ original bur (n = 50), fissurotomy with $Fissurotomy^{(R)}$ Miro NTF bur (n = 50), fissurotomy with SF104R tapered diamond bur (n = 50), fissurotomy with 1/2 round carbide bur (n = 50). Two types of flowable resins ($UniFil^{(R)}Flow$, $Filtek^{(R)}Flow$) were used as sealing materials. All samples were sectioned and observed using a stereoscopic microscope after thermocycling and immersing in methylene blue solution. The adaptation of flowable resin to the fissure wall was observed using scanning electron microscopy. The penetration of flowable resin into the carious fissure was significantly increased by fissurotomy, which also decreased microleakage. Fissure preparation using different burs showed a significantly different in penetration, but did not show any difference in microleakage. $Unifil^{(R)}Flow$ showed better penetration than $Filtek^{(R)}Flow$, but there was no significant difference in microleakage. Fissurotomy can be used to increase the penetration of flowable resin into carious fissures and decrease microleakage.

• Restorative Dentistry and Endodontics
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• v.22 no.2
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• pp.751-760
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• 1997

Resin-modified glass ionomers were introduced in 1988 to overcome the problems of moisture sensitivity and low early mechanical strengths of the conventional glass ionomers, and to maintain their dinical advantages. The purpose of this study was to evaluate the bi-axial fracture strength of four resinmodified glass-ionomers(Fuji II LC, Vitremer, Dyract, VariGlass), one resin composite material(Z-100), and one conventional glass-ionomer(Fuji II). Three specimens of each material and shade combination were made according to the manufacturers' instructions. Materials were condensed into metal mold with a diameter of 10mm and a thickness of 2.0mm and pressed between two glass plates. Resin-modified glass ionomers were polymerized using a Visilux II light curing unit by irradiating for 60 seconds from both sides, and conventional glass ionomer was cured chemically. After specimens were removed from the molds, surfaces were polished sequentially on wet sandpapers up to No. 600 silicone carbide paper. The specimens were thermocycled for 2,000 cycles between $5^{\circ}C$ and $55^{\circ}C$ distilled water. After thermocycling, bi-axial fracture strengths were measured using a compressive-tensile tester(Zwick 1456 Z020, Germany) with the cross head speed of 0.5mm/minute. The results were as follows: 1. Two factors of the kind and color of materials had a main effect on bi-axial fracture strength (p<0.01), and bi-axial fracture strength was influenced significantly by the kinds of materials (p<0.01). But there was no significant interaction between two variables of the kind and color of materials (p>0.05). 2. Comparing the mechanical properties of the materials, the elastic modulus of Z100 was higher than any other material, and there was no difference in the displacement at fracture among materials. The bi-axial fracture strength of Z100 was significantly higher than any other material, and that of resin-modified glass ionomers was significantly higher than that of conventional glass ionomer (p<0.05). 3. In the same material group, the color of material had little influence on the mechanical properties.

• Restorative Dentistry and Endodontics
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• v.31 no.6
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• pp.415-426
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• 2006

In this study, the changes in the degree of conversion (DC) and the microtensile bond strength (MTBS) of self-etching adhesives to dentin was investigated according to the time after curing. The MTBS of Single Bond (SB, 3M ESPE, USA), Clearfil SE Bond (SE, Kuraray, Japan), Xeno-III (XIII, Dentsply, Germany), and Adper Prompt (AP, 3M ESPE, USA) were measured at 48h, at 1 week and after thermocycling for 5,000 cycles between 5$^{\circ}$C and 55$^{\circ}$C. The DC of the adhesives were measured immediately, at 48h and at 7 days after curing using a Fourier Transform Infra-red Spectrometer. The fractured surfaces were also evaluated with scanning electron microscope. The MTBS and DC were significantly increased with time and there was an interaction between the variables of time and material (MTBS, 2-way ANOVA, p = 0.018; DC, Repeated Measures ANOVA, p < 0.001). The low DC was suggested as a cause of the low MTBS of self-etching adhesives, XIII and AP, but the increase in the MTBS of SE and AP after 48h could not be related with the changes in the DC. The microscopic maturation of the adhesive layer might be considered as the cause of increasing bond strength.

• Restorative Dentistry and Endodontics
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• v.26 no.1
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• pp.16-22
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• 2001

The purpose of this study was to evaluate the marginal microleakage of condensable composite resin restorations according to flowable resin lining of internal cavity wall. The eighty extracted human molar teeth without caries and/or restorations are used The experimental teeth were randomly assigned into four groups of ten teeth each. Eighty caries-free extracted human molars were used in this study. The conventional class II cavities (box-shaped on mesial and distal surface, faciolingual width : 3mm, gingival wall depth : 1.5mm) were prepared 1mm below cementoenamel junction with a # 701 carbide bur. The teeth were divided into four groups, and then each group were subdivided into A & B group according to flowable resin & compomer lining ; Group 1-A : Tetric Ceram filling, Group 1-B : Tetric Flow lining and Tetric Ceram filling, Group 2-A Ariston pHc filling, Group 2-B : Tetric Flow lining and Ariston pHc filing, Group 3-A SureFil filling, Group 3-B : Dyract Flow lining and SureFil filling, Group 4-A : Pyramid filling, Group 4-B : Aeliteflo lining and Pyramid filling. To simulate as closely as possible the clinical situation during retoration placement, a "restoration template" was fabricated, and the condensable resin was filled using a three-sited light-curing incremental technique. All the materials used were applied according to the manufacturers' instructions. The specimens were stored in the 100% humidity for 7 days prior to thermocycling (100 thermal cycles of 5~55$^{\circ}C$ water with a 30-second dwell time) The specimens were immersed in 2% metyleneblue dye for 24 hours, and then embedded in transparent acrylic resin and sectioned mesiodistally with diamond wheel saw. The degree of marginal leakage was scored under stereomicroscope ($\times$20) and the data were analyzed by Kruskal-Wallis test and Wilcoxon signed ranks test. The results were as follows : 1. In the gingival margins of all the group, microleakage of subgroup B was less than subgroup A. 2. In the group 1, 2, 4, there was significant differences between subgroup A and B (p<0.05), but in the group 3, there was not significant different between group 3-A (SureFil) and group 3-B (Dyract flow/SureFil) (p>0.05). 3. In the subgroup A and B, there was significant different between all group except group 4 of subgroup A. From the results above, it was suggested that the cavity lining of flowable resin and flowable compomer in condensable resin restoration decrease microleakage at gingival margin, and does improve their ability to seal the gingival margin of class II preparation.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.3
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• pp.527-533
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• 2004

One clinical technique recommended for improving marginal integrity is "rebonding" or application of unfilled resins to the surface of composite restoration. But continuously the restorations are affected with occlusal load. There is room for doubt that the rebonding agent has the positive effect on microleakage in spite of the stress generated by the occlusal load. This study determined the effect of rebonding on microleakage of Class V resin composite restorations under load cycling. Class V cavities were prepared on the buccal surface of 40 sound extracted premolars and restored with a hybrid light-cured resin composite according to manufacturers' directions. They were randomly divided into two groups consisting of 20 samples: a control(group I), without surface sealing, and the other group(group II) in which margins were etched and rebonded. After thermocycling, each of groups was divided into subgroups(group A, B), and load cycling(total 100,000 cycles with 4-100N load at a rate of 1 Hz) were applied on the group B. Assessment of microleakage utilized methylene blue dye penetration. The following results were obtained: 1. In the occlusal region, no significant difference was noted in the scores regardless of whether or not the rebonding agent was used(group TA-IIA, IB-IIB)(p>0.05). 2. In the cervical region, the control group with rebonding(group IIA) showed the better result than the group without rebonding(group IA)(p<0.05). 3. In the cervical region, the rebonded group with load cycling(group IIB) showed similar results to the group without rebonding(group IB) and no significant difference was noted(p>0.05).

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.5
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• pp.583-594
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• 2000

Dislodgement of a crown or extension bridge and the loosening of a retainer of a bridge is a serious clinical problem in fixed restoration. Generally these problems are considered to be associated with deformation of the restoration. During biting, the restoration is subjected to complex forces and deforms considerably within the limit of its elasticity. Deformation of the restoration under the occlusal force induces excessive stress in the cement film, which then leads to the cement fracture. Such a fracture may eventually cause loss of the restoration. Because most of the past retention tests for full veneer crown were done without fatigue loading, they were not exactly simulating intraoral environment. And the purpose of this study was to evaluate the effect of cyclic cantilever loading on the retentive strength of full veneer crowns depending on different type of cements and taper of prepared abutment. Steel dies with $8^{\circ}\;or\;16^{\circ}$ convergence angle were fabricated through milling and crowns with the same method. These dies and crowns were divided into 8 groups. Group 1 : $16^{\circ}$ taper die, cementation with zinc phosphate cement, without loading Group 2 : $16^{\circ}$ taper die, cementation with zinc phosphate cement, with loading Group 3 : $8^{\circ}$ taper die, cementation with zinc phosphate cement, without loading Group 4 : $8^{\circ}$ taper die, cementation with zinc phosphate cement, with loading Group 5 : $16^{\circ}$ taper die, cementation with Panavia 21, without loading Group 6 : $16^{\circ}$ taper die, cementation with Panavia 21, with loading Group 7 : $8^{\circ}$ taper die, cementation with Panavia 21 without loading Group 8 : $8^{\circ}$ taper die, cementation with Panavia 21, with loading After checking the fit of die and crown, the luting surface of dies and inner surface of crowns were air-abraded for 10 seconds. The crowns were cemented to the dies, with cements mixed according to the manufacturer's recommendations. A static load of 5kg was then applied for 10 minutes with static loading device. Twenty-four hours later, group 1, 3, 5, 7 were only thermocycled, group 2, 4, 6, 8 were subjected to cyclic loading after thermocycling. Retentive tests were performed on the Instron machine. From the finding of this study, the following conclusions were obtained 1. Panavia 21 showed significantly higher retentive strength than zinc phosphate cement for all groups (p<0.05). 2. There was a significant difference in the retentive strength between $8^{\circ}\;and\;16^{\circ}$ taper for zinc phosphate cement(p<0.05), but no significant difference for Panavia 21 (p>0.05). 3. Cyclic loading significantly decreased the retentive strength for all groups(p<0.05). 4. For zinc phosphate cement, there was 35% reduction of the retentive strength after loading in the $16^{\circ}$ taper die, 25% in the $8^{\circ}$ taper die, and for Panavia 21, 21% in the $16^{\circ}$ taper die, 18% in the $8^{\circ}$ taper die.