• Restorative Dentistry and Endodontics
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• v.21 no.1
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• pp.202-217
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• 1996

The purpose of this study was to compare the degree of microleakage of Glass-Ionomer root canal sealer possessed several enviable properties with that of the other sealers and to evaluate clinical performance. One hundred twenty single-rooted teeth were used in this experiment. The teeth were cleaned mechanically and immersed for 24 hours in 5.25% sodium hypochlorite and clinical crowns then were removed. After the root canals were instrumented using a step-back technique. one hundred twenty single-rooted teeth were divided into five groups of 24 in each. Group 1 : Tubli-Seal(Kerr Co., MI, U.S.A/ZOE-based), lateral condensation Group 2 : Sealapex(Kerr/Sybron, Romulus, MI/ $Ca(OH)_2$-based), lateral condensation Group 3 : AH 26(De Trey Co., Zurich Switzerland/Resin-based), lateral condensation Group 4 : Ketac-Endo(ESPE GMBH & CO. KG Seefeld:oberbay. Germany/ Glass Ionomer Cement-based), lateral condensation Control group : no sealer. lateral condensation And then. the root canals were obturated by lateral condensation technique with gutta-percha and experimental sealers. The control group were obturated without sealer. The teeth were placed in a vacuum chamber for 15 minutes and immersed 2% methylene blue under vacuum for 15 minutes. The teeth were passively stained for 1 week and 2 weeks and were cleared and evaluated for linear dye leakage using Tool maker's microscope(${\times}200$). The results were as follows: 1. There were statistically significant differences in the degree of dye penetration between the control group and experimental groups(p<0.05). 2. In the experimental groups, Sealapex($1.2871{\pm}0.9180mm$) exhibited the lowest mean value of dye penetration, followed by Ketac-Endo($1.4432{\pm}0.8082mm$), AH 26($1.5030{\pm}0.7752mm$) and Tubli-Seal($1.6458{\pm}1.0292mm$)(p>0.05). 3. There were statistically significant differences in the variation of microleakage between 1 week and 2weeks in Tubli-Seal and Seal apex groups (p<0.05). 4. The degree of dye penetration of all groups were increased as the time elapsed and AH 26 showed the lowest variation(+0.11) and Tubli-Seal(+ 1.03) showed the highest variation (p<0.001).

• The Journal of Korean Academy of Prosthodontics
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• v.39 no.3
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• pp.260-272
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• 2001

All-ceramic restorations have had a more limited life expectancy than metal ceramic restorations because of their low strength. Their relatively lower strength and resistance to fracture have restricted the use of all-ceramic crowns to anterior applications where occlusal loads are lower. But there has been increasing interest in all-ceramic restorations because patients are primarily concerned with improved esthetics. Many efforts have been made to in prove the mechanical properties of dental ceramics. This study was designed to elucidate the influence of the luting agent on the strength of the Empress 2 crown (staining technique) cemented on human teeth. Seventy extracted human permanent molar teeth were chosen. Teeth were prepared for Empress 2 crowns with milling machine on a surveyor. A dental bur was placed in the mandrel that was positioned so that the long axis of the bur was perpendicular to the surveyor base. Dimensions of the Empress 2 crown preparation were $6^{\circ}$ taper on each side, $1.5{\pm}0.1mm$ shoulder margin, and 4mm crown height. The luting cements used in this study were as follow: 1. Uncemented 2. Zinc phosphate cements (Confi-Dental) 3. Conventional glass ionomer cement : Fuji 1 (GC) 4. Resin-modified glass ionomer cements : Fuji plus (GC) 5. Adhesive cements : Panavia F (Kuralay), Variolink II (Vivadent), Choice (Bisco). Fracture test using Instron. The crowns were loaded in compressive force to evaluate the effect of these cements on the breaking strength of these all-ceramic crowns. A steel ball with a diameter of 4mm was placed on the occlusal surface and load was applied to the steel ball by a cylindrical bolt with a crosshead speed of 0.5mm per minute until fracture occurred. The fractured surface was examined using Scanning Electron Microscopic Image (SEM) to discover the correlation between fracture strength and bonding capacity. Within the limitation of this in vitro study design, the results were as follows : 1. fomentations significantly increased the fracture resistance of Empress ceramic crowns compared to control. Uncemented (206.9 N): ZPC (812.9 N): Fuji 1 (879.5 N): Fuji Plus (937.7 N): Choice (1105.4 N): Variolink II (1221.1 N): Panavia F (1445.2 N). 2. Resin luting agent, treated by a silane bond enhancing agents, yielded a significant increase in fracture resistance. In some of the Panavia F group, a fracture extended into dentin. 3. According to SEM images of fractured Empress crowns, the stronger the bond at both interfaces(crown and die), the more fracture strength was acquired.

• Restorative Dentistry and Endodontics
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• v.17 no.1
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• pp.95-103
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• 1992

The purpose of this study was to evaluate the effect of the dentin pretreatment on the marginal leakage of a glassionomer cement. 1n this study, 60 molars with sound and healthy crown portion were used. The dentin surface of these teeth were exposed and polished with 600 grit silicon carbide paper. Square - shaped cavities were prepared on the flattened dentin surfaces and these were divided into 4 groups according to the dentin pretreatment procedures. Group I : Dentin pretreatment with distilled water as a control group. Group II : Dentin pretreatment with 5% sodium hypochlorite solution. Group III : Dentin pretreatment with Ketac conditioner. Group IV : Dentin pretreatment with 40% polyacrylic acid. The degrees of dye penetration in the cavity walls were assessed using a stereoscope at ${\times}40$ magnification according to the maximum dye penetration. The results were analyzed by using Mann - Whitney U test. The results were as follows : 1. All groups showed varying depth of dye penetration. 2. Distilled water group showed the most severe marginal leakage when compared with the other groups(P<0.05). 3. 40% polyacrylic acid group showed the least amount of marginal leakage compared with the other groups (P<0.05). 4. There were significant differences between Goup I(distilled water) and Group IV (40% polyacrylic acid)(P<0.05), but there were no significant differences among Group I(distilled water), Group II(sodium hypochlorite), Group III(Ketac conditioner) (P>0.05).

• Journal of Dental Rehabilitation and Applied Science
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• v.37 no.4
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• pp.217-224
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• 2021

Purpose: The purpose of this study was to evaluate the porosity of resin modified glass ionomer (RMGI) by different mixing methods. Materials and Methods: Five specimens were prepared for each groups according to capsules and mixing methods. Two RMGI capsule and two mixing machines were used for this study. One resin-modified glass ionomer cement is Fuji II LC (F2LC) and the other is Photac Fil Quick Aplicap (PFQ). For Mixing of RMGI capsule, Rotomix using rotating motion and CM-II using shaking motion were used. After measuring height, radius and mass of specimens, Density was calculated. And porosity was measured using micro-computed tomography (micro-CT). All data were statistically analyzed using T-test, two-way ANOVA to compare between groups at 95% significance level to evaluate the affect of capsule and mixing method on the porosity. Results: The porosity was observed in all specimens generally. And there is significant differece between porosities according to RMGI capsule and Mixing method. The porosity of PFQ was lower than that of F2LC and the porosity of Rotomix was lower than that of CM-II. Conclusion: There was a difference of porosity according to kind of capsules and mixing methods. When using same capsule, less porosity was observed on PFQ than F2LC. When using same mixing mehod, less porosity was observed on Rotomix than CM-II. Using mixing machine of same coporation as that of RMGI capsule did not lead to lower porosity. Therefore, Selecting optimal mixing machine is important.

• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.4
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• pp.317-324
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• 2008

The objective of this study was to test effects of (1) where the occlusal contact points locate on a full veneer crown, and (2) which direction the contact forces are directed to, on the stresses within the luting cement layer that might suffer microfracture. A total of 27 finite element models were created for a mandibular first molar, combining 9 different locations of the occlusal contact points and 3 different loading directions. Type 3 gold alloy was used for crown material with a chamfer margin, and the luting cement material was glass ionomer cements in uniform thickness of $75{\mu}m$. Modeled crowns were loaded at 100 N. Different patterns in the cement stress were observed in the vicinity of the buccal and lingual margins. Whereas, the peak stress in buccal margin occurred approximately 0.5 mm away from the external surface, the highest stress in lingual margin was observed at approximately 1 mm. Significantly different distribution of stresses was recorded as a function either of the location of the occlusal contact points or of the loading direction. Higher stresses were produced by more obliquely acting load, and when the loaded point was in the vicinity of the cusp tip.

• Journal of Dental Rehabilitation and Applied Science
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• v.31 no.1
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• pp.1-9
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• 2015

Purpose: The purpose of this study was to evaluate the mechanical properties of several dual-cure cements by different curing modes. Materials and Methods: One resin-modified glass ionomer cement (FujiCEM 2), two conventional dual-cure resin cements (RelyX ARC, Multilink N), and two dual-cure self-adhesive resin cements (RelyX U200, G-CEM LinkAce) were used. To evaluate the influence of the curing methods, each cements divided into four conditions (n = 20); Condition 1: self-curing for 10 minutes, Condition 2: immediate after 20 seconds light-curing, Condition 3: 24 hours after self-curing, Condition 4: 24 hours after light-curing. The compressive strength and diametral tensile strength were measured with a universal testing machine. All data were statistically analyzed using t-test, one-way ANOVA and Scheffe's test. Results: The results showed the compressive strength and diametral tensile strength after 24 hours in all curing modes were higher than immediate except RelyX ARC light-cured and Multilink N light-cured. The FujiCEM 2 showed lowest values (P < 0.05). Conclusion: The outcome was cement-depend, but there is no significant difference about compressive strength and diametral tensile strength between dual-cure self-adhesive resin cements and conventional resin cements. And this result will be used as a base line data selecting resin cement for favorable long-term prognosis.

• The Journal of Korean Academy of Prosthodontics
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• v.36 no.6
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• pp.832-845
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• 1998

The purpose of this study was to compare the marginal fit of all ceramic crowns prepared from alumina slip casting, which is consistent with the conventional In-ceram system, and those fabricated from alumina tapes which is currently under development in an effort to alleviate complexities involved in the forming procedure of the In-ceram crown core. All ceramic crowns, made of In-ceram(slip casting) and alumina tapes(Doctor blade casting), were prepared with $90^{\circ}\;and\;135^{\circ}$ shoulder margins. The crowns were cemented with a glass ionomer cement and embeded in epoxy resin. The embedded crowns were sectioned faciolingually and mesiodistally and marginal discrepancies and marginal gaps were measured under the Measurescope MM II. The measurements were analyzed using Wilcoxon rank sum test and Kruskal-Wallis test and the results were as follows: 1. In the case of $90^{\circ}$ shoulder margin, the combined marginal discrepancies and marginal gaps were $78.3{\mu}m\;and\;44.4{\mu}m$ respectively, for the all ceramic crowns fabricated using the alumina tapes. In comparison, the values were $65{\mu}m\;and\;25.5{\mu}m$ for the In-ceram crowns. For the marginal gaps a statistical difference existed (p<0.05) but no significant difference was observed for the marginal discrepancy (p>0.05). 2. In the case of $135^{\circ}$ shoulder margin, the combined marginal discrepancy and marginal gaps were $82.1{\mu}m\;and\;40.2{\mu}m$ respectively, for the all ceramic crowns formed with the tapes. As compared with the marginal discrepancy and gaps of the $90^{\circ}$ shoulder margin in the fabricated from the alumina tapes, no significant statistical differencies were discerned in both cases (p>0.05). 3. There was no statistically significant difference in the fits among four locations around the margins of the all ceramic crowns fabricated using the alumina tapes. The results obtained in this study showed that the marginal fits of the glass infiltrated alumina cores fabricated from the alumina tapes are slightly higher value than those prepared using the In-ceram but the difference is within a clinically acceptable range.

• Restorative Dentistry and Endodontics
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• v.27 no.4
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• pp.389-393
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• 2002

The marginal integrity of the crown can be broken during endodontic access cavity preparation due to the vibration of burs. Therefore, the purpose of this study was to evaluate the effect of endodontic access cavity preparation on the marginal leakage of full veneer gold crowns. 24 intact molars were mounted in acrylic resin blocks and prepared for crowns by a restorative dentist and crowns were cast with gold alloy. 20 Crowns were cemented with glass ionomer cement and 2 crowns were not cemented for positive control. 200 thermo-cycles from 5$^{\circ}C$ to 5$0^{\circ}C$ with a travel time of 20s were completed. Then samples were randomly divided into 2 experimental groups of 9 each. Endodontic access preparation and zinc-oxide eugenol temporary fillings were done in Group 1. Teeth in Group 2 were not treated. Samples were coated with 2 layers of nail varnish and were immersed in 1% methylene blue dye for 20 hrs. Endodontic access was prepared in 2 samples, which were coated with nail varnish on all surfaces for negative control. After washing in running water gold crowns were cut with a #330 bur. Four buccolingual sections, 2 mm apart, were cut from the central section of each tooth and were examined and scored under the microscope for dye leakage. Score 1: leakage to the cervical 1/3 of the axial wall, Score 2: leakage to the middle 1/3 of the axial wall, Score 3: leakage to the coronal 1/3 of the axial wall, Score 4: leakage to the occlusal surface. The median value for Group 1 is 4 and for Group 2 is 2. The result of this study showed that samples in Group 1 leaked more than those in Group 2. This finding was significant(P<0.001).

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.1
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• pp.82-86
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• 2001

The aim of this study was to investigate the level of radiopacity of esthetic dental restorative materials and determine the optimum level of radiopacity in pediatric dentistry. Disks of 8 dental restorative material groups as the experimental group, 7mm in diameter and 2mm thick, were radiographed with intact human deciduous teeth and aluminum stepwedge standard. Radiopacity was evaluated with an image analysis program following the digitization of the radiographs using a flatbed scanner with transparency unit. All materials and tooth structure also the significant difference except FP, VB, VM. For the radiopacity of esthetic restorative dental materials to exceed that of enamel, it should be greater than 1.7mm of equivalent thickness of aluminum.

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.1
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• pp.110-115
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• 2003

Dens evaginatus is an anomalous tooth development arising during morphodifferentiation. It is most often reported in premolar, and familial occurrence has been reported. The primary dental complication of dens evaginatus is fracture or wear of the tubercle which leads to pulp exposure, pulpal necrosis and periapical infection. Pathosis of the pulp can occur before complete root formation with cessation of root development. A rational and conservative approach to the management of dens evaginatus in vital teeth includes early diagnosis and treatment to prevent fracture or attrition of the tubercle. This treatment would include careful sequential grinding, pulp capping, preventive resin restoration. When presented with a case of dens evaginatus in a nonvital tooth with incomplete root development, the treatment of choice has been extraction, apexification. We report two cases of dens evaginatus that appear in two sisters. In the elder, a periapical lesion on radiographs is shown, and it is treated by calcium hydroxide apexification. The other sister is early recognized of dens evaginatus, it is treated using glass ionomer cement reinforcing with sequential grinding.