Go to the main menu
Skip to content
Go to bottom
REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
Restorative Dentistry and Endodontics
Journal Basic Information
Journal DOI :
The Korean Academy of Conservative Dentistry
Editor in Chief :
Volume & Issues
Volume 23, Issue 2 - Dec 1998
Volume 23, Issue 1 - Apr 1998
Selecting the target year
INFLUENCES OF APICOECTOMY AND RETROGRADE CAVITY PREPARATION METHODS ON THE APICAL LEAKAGE
Yang, Jeong-Ok ; Kim, Sung-Kyo ; Kwon, Tae-Kyung ;
Restorative Dentistry and Endodontics, volume 23, issue 2, 1998, Pages 537~549
The purpose of this study was to evaluate the influence of root resection and retrograde cavity preparation methods on the apical leakage in endodontic surgery. To investigate the effect of various root resection and retrograde cavity preparation methods on the apical leakage, 71 roots of extracted human maxillary anterior teeth and 44 mesiobuccal roots of extracted human maxillary first molars were used. Root canals of the all the specimens were prepared with step-back technique and filled with gutta-percha by lateral condensation method. Three millimeters of each root was resected at a 45 degree angle or perpendicular to the long axis of the tooth according to the groups. Retrograde cavities were prepared with ultrasonic instruments or a slow-speed round bur, and occlusal access cavities were filled with zinc oxide eugenol cement. Three coats of clear nail polish were placed on the lateral and coronal surfaces of the specimens except the apical cut one millimeter. All the specimens were immerged in 2% methylene blue solution for 7 days in an incubator at
. The teeth were dissolved in 14 ml of 35% nitric acid solution and the dye present within the root canal system was returned to solution. The leakage of dye was quantitatively measured via spectrophotometric method. The obtained data were analysed statistically using two-way ANOVA and Duncans Multiple Range Test. The results were as follows: 1. No statistically significant difference was observed between ultrasonic retrograde cavity preparation method and slow-speed round bur technique, without apical bevel (p>0.05). 2. Ultrasonic retrograde preparation method showed significantly less apical leakage than slow-speed round bur technique, with bevel (p<0.0001). 3. No statistically significant difference was found between beveled resected root surface and non-beveled resected root surface, with ultrasonic technique (p>0.05). 4. Non-beveled resected root surface showed significantly less apical leakage than beveled resected root surface, with slow-speed round bur technique (p<0.0001). 5. No statistically significant difference in apical leakage was found between the group of retrograde cavity prepared parallel to the long axis of the tooth and the group of one prepared perpendicular to the long axis of the tooth (p>0.05). 6. Regarding isthmus preparation, ultrasonic retrograde preparation method showed significantly less apical leakage than slow-speed round bur technique, in the mesiobuccal root of maxillary molar, without bevel (p<0.0001).
EFFECT OF POLYPHOSPHATE ON THE GROWTH OF ORAL BACTERIUM, PREVOTELLA INTERMEDIA
Kong, Hee-Joung ; Choi, Ho-Young ; Min, Byung-Soon ; Part, Sang-Jin ; Lee, Jin-Yong ; Choi, Gi-Woon ;
Restorative Dentistry and Endodontics, volume 23, issue 2, 1998, Pages 550~560
Prevotella intermedia has been known as one of the important bacterial species involved in the endodontic infections and various periodontal diseases. Polyphosphate has been widely used to prevent decomposition of food and known to have an inhibitory effect on the growth of gram positive bacteria. The purpose of this study was to evaluate the effect of poly phosphate on the growth of Prevotella intermedia, a gram negative bacterium. Prevotella intermedia G8GK3(ATCC 49046) was grown in the presence of polyphosphates with different chain lengths. Inhibitory effect of each polyphosphate, which was added at the beginning or at the early exponential growth phase of Prevotella intermedia, was determined by measuring optical density of the bacterial cells at 540nm, viable cells and lysis of Prevotella intermedia. The results from this study were as follows : 1. Poly phosphate inhibited the growth of Prevotella intermedia. 2. The minimum inhibitory concentration(MIC) of poly phosphate appeared to be 0.05%. 3. Polyphosphates with chain lengths of 5 and 65 demonstrated the greatest inhibitory effect on the growth of Prevotella intermedia. 4. Polyphosphate was bactericidal to Prevotella intermedia, demonstrating the growth inhibition of the bacterium. 5. Polyphosphate induced lysis of Prevotella intermedia. The overall results suggest that polyphosphate has a bactericidal effect on Prevotella intermedia, causing the lysis of the bacterium.
EFFECT OF SMEAR LAYER ON THE APICAL LEAKAGE OF WARM VERTICAL CANAL FILLING
Kwon, Tae-Kyung ; Kim, Sung-Kyo ;
Restorative Dentistry and Endodontics, volume 23, issue 2, 1998, Pages 561~574
The purposes of this study were to observe the difference in the root canal wall after hand instrumentation or engine-driven Ni-Ti instrumentation under the scanning electron microscope, and to evaluate the apical leakage provided by continuous wave of canal filling technique with or without root canal sealer and smear layer. Twenty recently extracted human maxillary anterior teeth were instrumented with K-type files or engine-driven Ni-Ti files, Quantec series 2000
and irrigated with 5.25% NaOCl alone or 15% EDT A and final flush of 5.25% NaOCl. After the instrumentation and flushing, teeth were split in half with a knife and a mallet. They were then examined with a scanning electron microscope Forty-four recently extracted human maxillary anterior teeth were divided into four groups with and without smear layer and then warm vertical canal filling using System-B with or without sealer. The extent of leakage was scored after immersion in India ink for 1 week. The results were as follows: 1. No significant difference of smear layer was observed between K-type file-instrumented group and engine-driven Ni-Ti file-instrumented group. 2. A group without smear layer showed significantly less apical leakage than a group with smear layer when sealer was used for the canal filling (p<0.01). 3. There was no significant difference between a group without sealer and smear layer and a group without sealer and with smear layer (p<0.01). 4. In groups without smear layer, a group with sealer showed significantly less apical leakage than a group without sealer (p<0.01). 5. When root canals were irrigated with NaOCl alone, a group with sealer showed significantly less apical leakage than a group without sealer (p<0.01).
COLOR REPRODUCIBILITY OF THE NEW COLOR ANALYZING TECHNIQUE USING A CORRECTION PAPER, CASMATCH
Shin, Ki-Sung ; Cho, Kyoung-Mo ; Cho, Yong-Bum ; Shin, Dong-Hoon ;
Restorative Dentistry and Endodontics, volume 23, issue 2, 1998, Pages 575~585
Use of the digital camera as a color measuring device was proposed. Digital camera can save, adjust and transmit image using computer. But it has great disadvantage that color of image possibly altered by environment of image capturing state, so the color reproducibility of digital camera can severly damage, Casmatch, the supplement for color correction, was proposed for enhance the color reproducibility of digital camera. Thus for study the efficacy of the Casmatch in enhancing the color reproducibility of digital camera, image of 78area in 39teeth was captured three times during two days and color reproducibility was evaluated and analyzed in terms of the use of Casmatch, teeth positions, and area within the tooth and comparatively analyzed. Results were as follow ; 1.
E the color reproducibility of digital camera was 6.90
3.27 in same day and 7.43
3.94 in different day, and the color reproducibility when using Casmatch correction was 6.21
4.48, there is no enhancement in using Casmatch correction. 2. There is no difference in color reproducibility between teeth, but color reproducibility of the middle third was greater(p<0.05) than the gingival third before color correction using Casmatch.
THE EFFECT OF THE POLYSTYRENE LINER ON MICROLEAKAGE OF AMALGAM RESTORATION
Lee, Kyoung-Sun ; Ro, Byeng-Duck ; Youn, Tai-Cheol ;
Restorative Dentistry and Endodontics, volume 23, issue 2, 1998, Pages 586~596
Amalgam is one of the most commonly used dental restoration material because of its convenience, economic and physical properties. But microleakage in the tooth and amalgam interface has been its major problem, and many efforts have been made to overcome this shortcoming. The purpose of this study is to compare the effect of various liners on microleakage of amalgam restoration. Cavities were prepared on the buccal or lingual surface of ninety sound, extracted human premolars and six different liners (Tubulitec
, Superbond D-liner II Plus
, Superbond D-liner II Plus
with polymer, Scotchbond Multipurpose Plus
, No liner) were unapplied according to manufacturer's instructions and amalgam had been condensed immediately. The specimens were thermocycled by dipping in methylene blue dye at
for 1500 cycles. The amalgam-tooth interface was examined under stereobinocular microscope and the dye penetration was scored. The results were as follows : 1. The Tubulitec
group showed less microleakage than no liner or Copalite
group (p<0.01). 2. The Tubulitec
, Superbond D-liner II Plus
, Superbond D-liner II Plus
with polymer and Scotch bond Multipurpose Plus
groups were not significantly different. 3. The Copalite
and Scotchbond Multipurpose Plus
groups were not significantly different. Using the polystyrene liner and resin liners under admixed type of high-copper amalgam restoration significantly reduced microleakage in the tooth-amalgam interface. Further clinical studies on polystyrene liner are recommended.
EFFECT ON THE SHEAR BOND STRENGTH OF A COMPOMER TO DENTIN ACCORDING TO SURFACE CONDITIONING
Kim, Soo-Mee ; Cho, Young-Gon ; Moon, Joo-Hoon ;
Restorative Dentistry and Endodontics, volume 23, issue 2, 1998, Pages 597~606
The purpose of this study was to evaluate the shear bond strength of the Compoglass Carvifil bonded on the dentin surface according to etching or non-etching and two time application or three time application of single component. Human non-carious 60 extracted 3rd molar were used. The occlusal dentin surfaces of all teeth were exposed with Diamond Wheel Saw and polished with Lapping & Polishing machine(South Bay Technology Co., U.S.A). The teeth were then distributed randomly into four groups of 15 teeth each and dentin surface were conditioned as following. Control group : Non-etching, two times application of Syntac Single Component. (According to manufacture's instruction) Experimental group 1 : Non-etching, three times application of Syntac Single Component. Experimental group : 2 Etching, two times application of Syntac Single Component. Experimental group 3 : Etching, three times application of Syntac Single Component. Compoglass were bonded to exposed dentin surfaces and all samples were placed in distilled water for 7 days. The shear bond strengths were measured by universal testing machine (SHIMADAZU AUTOGRAPH, AGS-4D., Japan). The results were as follows : 1. Experimental group 3 revealed the highest value (30.75
4.74 MPa) and control group revealed the lowest value(14.85
2.69 MPa). There was significant difference of shear bond strength among four groups(P<0.01) 2. The acid-etching groups (experimental group 2, 3) had higher shear bond strengths than non etching groups(control group and experimental group 1). 3. The additional application of Syntac single component groups revealed a higher bond strength than two times application groups (control group and experimental group 2).
A COMPARISON OF THE APICAL SEALING ABILITY OF OBTURATION TECHNIQUES BY THERMALLY SOFTENED GUTTA PERCHA
Baek, Seung-Ho ;
Restorative Dentistry and Endodontics, volume 23, issue 2, 1998, Pages 607~617
The purpose of this study was to evaluate the apical sealing ability of lateral condensation method, vertical condensation method, and MicroSeal obturation system. Sixty-four extracted anterior teeth were instrumented to #40 using Profile. Three groups of 20 teeth were obturated by lateral condensation technique, vertical condensation technique, and and MicroSeal obturation system. Control group were not obturated. Teeth were immersed in resorcinol-formaldehyde resin for 5 days at
, and the resin was allowed to polymerize completely for 4 days at room temperature. Teeth were ground horizontally at 1,5mm(level 1), 2.5mm(level 2), and 3.5mm(level 3) from the anatomic apex and examined with a stereomicroscope at X40 magnification. The photographs were taken a at X40 magnification of the filling in each level and scanned. The leakage area, which was filled with the resin, was measured at each of the three levels. Each ratio of leakage was evaluated by calculating the ratio of thearea of the resin to the total area of the canal and was analyzed statistically. The results were as followed: 1. Vertical condensation group had significantly higher percentage of the area which was obturated by gutta percha than other two technique at each level. 2. At the level 1, there was the greatest leakage in the lateral condensation group, but there was no statistically significant(P>0.05) 3. At the level 2, there was the least leakage in the MicroSeal group, and the most leakage in the lateral condensation group. There was statistically significant difference between the MicroSeal group and the lateral condensation group(P<0.05). 4. At the level 3, there was least leakage in the vertical condensation group, and the most leakage in the lateral condensation group. There was statistically significant difference between the vertical condensation group and the lateral condensation group(P<0.05).
MARGINAL AND INTERNAL FIT OF CAD/CAM-MANUFACTURED CERAMIC INLAY
Son, Ho-Hyun ;
Restorative Dentistry and Endodontics, volume 23, issue 2, 1998, Pages 618~629
CAD/CAM-fabricated ceramic restorations nowadays are used as alternatives of amlagam and posterior composite resin restorations, especially in the cases of inlay restorations. But the reported results on marginal and internal fit of CAD/CAM-fabricated ceramic inlay have showed considerable difference. In this study, to evaluate the marginal and internal fit of CEREC2-fabricated ceramic inlay restoration and to compare with the fit of gold inlay and amalgam restoration, standardized Class II MO cavities were prepared in forty extracted caries-free human premolars. The teeth with prepared cavities were divided into 4 groups of ten teeth each. In group 1, CEREC2-fabricated ceramic inlays were treated with Scotchbond Multi-Purpose Plus(SMP plus) and cemented with Scotchbond Resin Cement. In group 2, casted gold inlays were cemented in the same method as in group 1. In group 3, casted gold inlays were cemented with zinc-phosphate cement. And in group 4, the prepared cavities were restored with amalgam. Restored teeth were thermocycled, stored in 1% methylene blue for 24 hours, and sectioned faciolingually and mesiodistally using EXAKT. Sectioned surfaces were observed with stereomicroscope and the gaps were measured at 9 points of mesiodistally sectioned surface and 7 points of faciolingually sectioned surface. The measured data were treated by Kruskal-Wallis one way ANOVA and Student-Newman-Keuls test. 1. The differences among measured gaps at each points were statistically significant for 4 experimental groups (P<0.05). 2. There were statistically significant differences in the measured gaps at each points between group 1 and group 2, group 1 and group 3, group 1 and group 4, group 2 and group 4, and group 3 and group 4 (P<0.05). 3. There were not statistically significant differences in the measured gaps at each points between group 2 and group 3 (P>0.05). 4. In the cases of inlay restorations(group 1, group 2, group 3), the gaps at internal line angle(distopulpal, axiogingival, faciopulpal, linguopulpal line angle) had a tendency to increase. In the cases of amalgam restorations(group 4), the gaps at occlusal margin, gingival margin and axiogingival line angle were greater than those at the other parts of cavities. 5. In CEREC2-fabricated ceramic inlays which were treated with Scotchbond Multi-Purpose Plus and cemented with Scotchbond Resin Cement, the mean gaps were
at cavity margins,
at vertical walls of cavities,
at internal line angles and
at cavity floors.
THE EFFECT OF GALVANIC CURRENT BETWEEN DENTAL RESTORATIONS ON HUMAN SALIVA
Kwon, Hyuk-Choon ; Um, Chung-Moon ; Cho, In-Sik ; Ryu, Ju-Hee ; Son, Ho-Hyun ;
Restorative Dentistry and Endodontics, volume 23, issue 2, 1998, Pages 630~638
The purpose of this study was to evaluate the effect of galvanic current between different metallic restorations on human saliva. The rate of salivary flow and concentrations of IgG, IgM, sIgA and lactoferrin were measured. In this study, unstimulated whole saliva collected before restoration was regarded as control group and unstimulated whole saliva collected 10 minutes, 1 day, 1 week, and 1 month after restoration were regarded as experimental groups. Following results were obtained from this study. 1. There were some differences in values of salivary flow rate between experimental groups, but the changes in values compared to those of the control group were not statistically significant(P>0.05). 2. Measurements of major antibacterial components of saliva showed that while the concentrations of IgG and IgM decreased significantly 1 week and 1 month after restoration(P<0.05), changes in values of sIgA and lactoferrin were not statistically significant(P>0.05). 3. In vitro measurements of galvanic currents decreased sharply in the first 20 seconds and thereafter decreased gradually. Galvanic current values measured in the early stages were greatly varied, but after 2 hours, the values in all groups approximated each other.
TWO-DIMENSIONAL FINITE ELEMENT ANALYSIS ON THE EFFECT OF INTERFACE CONDITION AND RETENTION GROOVE IN CLASS V COMPOSITE RESIN RESTORATION
Cho, Byeong-Hoon ; Yoo, Hyeon-Mee ; Kim, Dong-Ho ;
Restorative Dentistry and Endodontics, volume 23, issue 2, 1998, Pages 639~646
To evaluate the effect of interface conditions and retention grooves in the Class V composite resin restoration of the maxillary first premolar, the distribution of the values of stress and displacement was analyzed with the two-dimensional finite element method. The results were obtained as follows : 1. Boundary elements and Stiffness values could be used as the interface parameters in the, finite element method. 2. The amount of restriction of the displacement at the cervical margin by placing a retention groove at the cervical wall was about three times as high as that by placing a retention groove at the occlusal wall. 3. Because of the relative amount of tensile components of the stress values in the bucco-lingual direction, the possibility of dislocation of the restoration was much higher at the cervical margin than at the occlusal margin. 4. It might be recommended that both occlusal and cervical retention grooves be used routinely, but if one, it be placed at the cervical wall.
THREE-DIMENSIONAL FINITE ELEMENT STRESS ANALYSIS OF PORCELAIN INLAY AND ONLAY
Kwon, Hyuk-Choon ; Um, Chung-Moon ; Son, Ho-Hyun ; Cho, Byeong-Hoon ;
Restorative Dentistry and Endodontics, volume 23, issue 2, 1998, Pages 647~655
A QUANTITATIVE STUDY ON THE DEGRADING EFFECT OF THE VARIOUS IRRIGATING AGENTS IN THE ELIMINATION OF RESIDUAL HYDROGEN PEROXIDE FOLLOWING WALKING BLEACHING
Kum, Kee-Yeon ; Han, Won-Sup ; Jung, Il-Young ; Lee, Seung-Jong ; Lee, Chan-Young ; Oh, Byung-Hoon ;
Restorative Dentistry and Endodontics, volume 23, issue 2, 1998, Pages 656~669
Hydrogen peroxide at high concentration during walking bleaching may cause damage to the tooth structure and to the surrounding periodontal tissues and may develop external root resorption. Clinically, It is so important to find a method of prevention or minimization of these complications. The efficacy of various chamber-irrigating agents to eliminate residual hydrogen peroxide after walking bleaching was examined and compared with water rinse in this study. Extracted human 46 premolars without any cementoenamel junction defects were treated endodontically and based with IRM to 1 mm below CEJ and totally bleached 3 times for each tooth with 30% hydrogen peroxide and sodium perborate. Upon completion of the 3rd walking bleaching procedure, the cervical portion and pulp chamber of each group of teeth were irrigated with catalase, 70% ethylalcohol, acetone, and distilled water. And then, a radicular hydrogen peroxide penetration was measured with spectrophotometer immediately after each bleaching and following treatment with each chamber-irrigating agents, and the significance of their eliminating efficacy of residual hydrogen peroxide was analyzed by Kruskal-Wallis test. The results were obtained as follows. 1. Cervical root penetration of hydrogen peroxide was increased as the bleaching procedure was repeated(P<.01). 2. The most effective irrigant that removed residual hydrogen peroxide was the catalase, and the least effective one was water rinsing (P<.01).; there was no significant difference between the acetone and ethanol group. 3. The Irrigation with antioxidant enzyme or water-displacement solutions can eliminate residual oxygen radicals from the pulp chamber effectively after walking bleaching. So, these agents can reduce adverse effects such as cervical external resorption and periapical inflammation and prevent residual
from impeding composite resin polymerization, thus increase the bonding strength of composite resin. This, in turn reduces microleakage and discoloration of the esthetic restoration, extending its service-life.
EVALUATION OF THE ACCURACY OF THE APEX FINDER A.F.A.
Yang, Mi-Young ; Yoo, Hyeon-Mee ; Oh, Tae-Seok ;
Restorative Dentistry and Endodontics, volume 23, issue 2, 1998, Pages 670~675
Recently electronic apex locators have been used widely in root canal treatment, but, accuracy of electronic apex locators is controversial. The purpose of this study was to evaluate the accuracy of Apex Finder A.F.A(EIE Analytic Technology, U.S.A.) in vivo compared with Root-Zx and radiograph. The root canal lengths were determined with Root-Zx(32 tooth) in before pulp extirpation and after pulp extirpation. Then the radiographs were taken with a file in the canal. The root canal lengths were determined with Apex Finder A.F.A.(21 tooth) in before pulp extirpation and after pulp extirpation and under NaOCl. Then the radiographs were taken with a file in the canal. The results were as follows: 1. There was no significant statistical difference in Root-Zx between before pulp extirpation and after pulp extirpation(p > 0.05). 2. There was no significant statistical difference in Apex Finder A.F.A. between before pulp extirpation and after pulp extirpation(p > 0.05). But, there was significant statistical difference under NaOCl(p < 0.05). 3. There was no significant statistical difference in accuracy between Root-Zx and Apex Finder A.F.A.
A STUDY ON THE MECHANISM BY WHICH THE FREQUENCY-DEPENDENT APEX LOCATOR DETECTS THE APEX OF THE ROOT IN MOIST CANALS
Park, Han-Soo ; Yoo, Hyeon-Mee ; Oh, Tae-Seok ;
Restorative Dentistry and Endodontics, volume 23, issue 2, 1998, Pages 676~681
The purpose of this study is to explain theoretically the mechanism of the frequency-dependent apex locator which can detect the apex of the root in moist canals with blood or other conductible canal irrigants. The frequency-dependent apex locator is based on measuring the ratio of the two impedances of the two alternating currents with different frequencies. We analyzed the changes of the ratio between the two impedances by using differential calculus. Our analysis shows that : 1. When the file is in the moist canal, the ratio between the two impedances is almost constant. 2. As the file approaches the apex of the root, the ratio decreases sharply. By this mechanism, the frequency-dependent apex locator can detect the apex of the-root quite accurately in moist canals.
EVALUATION OF THE SEALING ABILITY OF Microseal
Oh, Tea-Seok ; Yoo, Hyeon-Mee ; Hwang, Hea-Kyung ;
Restorative Dentistry and Endodontics, volume 23, issue 2, 1998, Pages 682~689
The purpose of this study was to evaluate the sealing ability of the Microseal
, which was new obturation system made by Tycom company, U.S.A. Forty-five extracted single-rooted human teeth were resected at cemento-enamel junction and divided three groups. All canals were prepared using Profile system, and then each group was obturated by lateral condensation technique (group 1), vertical condensation technique (group 2) and Microseal
condensation technique (group 3) with root canal sealer. Teeth were immersed in resorcinol-formaldehyde resin for 5 days at
and the resin was allowed to polymerize completely for 4 days at room temperature. Teeth were resected horizontally at 1 mm (level I), 2 mm (level II), 3 mm (level III) from the anatomical root apex using low speed microtome and examined with Image analyzer (IBASR, Zeiss co., Germany.) at
magnification. The gab between the canal wall and the filling material, which was filled with the resin, was measured at each of the three levels. Each ratio of leakage was expressed percentage by calculating the ratio of the area of the resin to the total area of the canal and was analyzed statistically (one-way ANOVA). The results were as follows; 1. The mean ratio of leakage (%) was 6.46% at group 1, 3.06% at group 2, 11.27% at group 3. 2. When evaluating the ratio of leakage at the three levels, there was level I> level II> level III in all groups. Especially, the difference between level I and level III was statistically significant (p<0.05). 3. When evaluating the ratio of leakage at the three groups, there was group 3> group 1> group 2 at all levels. Especially the difference between group 2 and group 3 was statistically significant (p<0.05).
EFFECT OF CORE-SHELL PARTICLES ON PHYSICAL PROPERTIES OF DENTAL COMPOSITES
Choi, Kyoung-Kyu ;
Restorative Dentistry and Endodontics, volume 23, issue 2, 1998, Pages 690~700
Rubber-toughened particles which are used in the field of chemical engineering are used to increase the fracture toughness of thermoset resin. The application of Core-Shell particles, one of rubber-toughened particles, as a filler for dental composite or restoration have not been examined. The purpose of this study was to evaluate possible use of Core-Shell particles for dental composite, and the hypothesis was that additional toughening mechanisms are activated by the addition of Core-Shell particles. After blending 50vol% quartz with Bis-GMA/TEGDMA resin matrix, the experimental resins were made by the addition of Core-Shell particles with varied content level as 0, 2.5, 5, 7.5, 10, 12.5, 15, and 20wt%. Fracture toughness was determined on three-point bending specimen with single-edge notch according to ASTM-E 399. Also, flexural properties, that is, strength and modulus were measured by three-point bending testing. Fractogragh of fracture toughness specimen was observed using SEM (JEOL 6400 SEM, MA). The following results from this study were obtained ; 1. Fracture toughness of composite resin added 2.5wt% Core-Shell particles was significantly higher than control group (
). 2. Flexural properties were decreased with increasing Core-Shell particle content, which showed a correlation statistically (
). 3. A toughening mechanism such as lamination and microcrack was observed in specimen determined high fracture toughness. 4. The dispersion of Core-Shell itself and quartz filler particles was limited present high content of Core-Shell particles, which decreased a resulting mechanical properties of composites. These results suggest that adequate Core-Shell particles can be used to enhance mechanical properties included toughening for dental composites.
A COMPARISON OF RELEASE RATE AND CUMULATIVE RELEASE OF TEGDMA WITH OR WITHOUT THE APPLICATION OF BONDING RESIN
Shin, Hee-Jung ; Jeon, Seong-Min ;
Restorative Dentistry and Endodontics, volume 23, issue 2, 1998, Pages 701~709
Many dental composites are Bis-GMA based resin which diluted with the more fluid monomer triethylenglycol dimethacrylate(TEGDMA). TEGDMA is often present in exess so that some quantity remains unreacted following photo-initiated polymerization. TEGDMA is a component of some resin composites which contributes to their cytotoxicity. The presence of dentin between resin composite and pulp space reduce the cytotoxicity in vitro. The root system from extrcted human third molar was removed and then a circular occlusal cavity 4mm in diameter was prepared, leaving a remaining dentinal thickness to the roof of the pulpal chamber within the range 1.0-1.5mm. Dentine was treated with 37% phosphoric acid prior to Z 100 placement without using bonding resin(group 1). In group 2, SMP(Scotchbond Multi Purpose) primer, bonding resin prior to Z 100 placement were applied sequently. In group 3, moulds with internal dimensions 4mm diameter by 2mm depth were used to contain the composite alone with an equvalent mass on tooth model, and then they were immersed directly into water. The purpose of this study is to evaluate the release rate and quantity of TEGDMA with or without the application of bonding resin. Both release rate and total cumulative amount of TEGDMA for the three groups were determined using reversed-phase HPLC at times up to 10 days. The results were as follows: 1. All experimental groups showed the highest rate of release was in the first sample period(0-4.32 min) and the rate of release declined exponentially thereafter. 2. The maximum release rate and total cumulative account of TEGDMA in the tooth model of group 1 and group 2 with the use of SMP bonding resin were reduced however ther were no significant differences between these groups(P>0.05). 3. In the first sample period(0-4.32 min), the rate of release of TEGDMA from composite resin in group 3 immersed directly into water was significantly higher than that in group 1 and group 2 of tooth model(P<0.05). Conclusively, TEGDMA diffusion from Z 100 resin was not effectively prevented by the presence of dentin in spite of using the SMP bonding resin.
PH CHANGES AT THE SURFACE OF ROOT DENTIN WHEN USING ROOT CANAL SEALERS CONTAINING CALCIUM HYDROXIDE
Rheu, Ean ; Jeon, Seong-Min ;
Restorative Dentistry and Endodontics, volume 23, issue 2, 1998, Pages 710~717
The pH changes in 3 cavities prepared at the facial inner dentin and lingual outer dentin of the cervical portion and apical portion of roots filled with calcium hydroxide containing sealers were investigated. 50 extracted permanent teeth with single canal were instrumented with step-back method. An irrigant of 5% NaOCl was used between files. Then 3 small cavities were prepared. The cavity of apical portion and inner dentin cavity of coronal portion was cut a distance of about 1.0mm from the canal wall and outer dentin cavity of coronal portion was cut to a depth of about 0.5mm from root surface. 10 teeth of control group was not filled. 20 teeth were not flushed with 17% EDTA before using root canal sealers and then divided into 2 groups obturated with Sealapex and Apexit. The remaining 20 teeth were flushed with 17% EDTA and 5% NaOCl to remove smear layer and divided into 2 groups obturated with Sealapex and Apexit. The pH change of the dentin in each cavity was measured at 0, 1, 3, 5, 7, 15, 30 days with pH microelectrode(WPI Co., USA). The results were as follows: 1. The groups obturated with Sealapex and Apexit(calcium hydroxide based-sealers) have no increase in the pH level at root dentin. And there is no significant difference in pH level between groups obturated with Sealapex and Apexit(P>0.05). 2. Differences in pH levels between the treated and untreated groups with EDTA were not significant(P>0.05). 3. There is no significant difference in pH level between apical and cervical dentin, inner and outer dentin throughout the duration of the experiment(P>0.05).