The aim of this study was to evaluate the microleakage of teeth according to root canal preparation with & without apical enlargement in various size of apical foramen. 60 extracted one canal roots were cross-cutted at 5 mm from root apex and divided into two groups according to their apical foramen size of large (L) and small (S). Each group was subdivided into two groups accordance with their cross-sectional configuration at 5 mm from apex, round (R) and ovoid (O); SR Group, SO Group, LR Group, LO Group. Each group was shaped in .02 taper by Quantec series Nickel-Titanium (NiTi) rotary file, obturated by lateral condensation method. Leakage was measured using a fluid transport model under 40 cmH₂O pressure. After the leakage test, blocks which had showed the leakage retreated with .04 taper and .06 taper and evaluated the degree of fluid filtration in each group. The data was analysed statistically using chi-square test and fisher's exact test.

The results obtained were as follows:

1. Significant difference in leakage was found in groups which had different apical foramen size in .02 taper instrumentation (p < 0.05), but not in .04 taper instrumentation (p > 0.05).

2. The difference in microleakage according to the shape of canal was not evident at 5 mm from apex (p > 0.05).

3. There was correlation between .02 taper instrumentation and .04 taper instrumentation in LR group , LO group (p < 0.05).

The aim of this study was to evaluate the effectiveness of sealer placement in simulated root canal extensions. Forty resin blocks were attained from the Endo-training Bloc. In each block, the simulated root canal was made with #20, 08taper GT file. After each block was longitudinally split into two halves, a standardized groove was prepared on one canal wall of two halves to simulate the canal extensions with various irregularities. The two halves of each block were assembled and all simulated root canals were obturated by single cone method with AH26 sealer. Four different methods of sealer placement were used: group A, #20 K-file; group B, ultrasonic file; group C, lentulo spiral; group D, EZ-Fill bi-directional spiral. All obturated blocks were stored in 100% humidity at 37℃ for 1 week. Using a low speed saw, each block was sectioned horizontally. Images of the sections were taken using a stereomicroscope at × 30 magnification and a digital camera. The amount of the sealer in the groove was evaluated using a scoring system, a higher score indicated better sealing effectiveness. The data was statistically analysed by Fisher's Exact Test.

The sealing score was the lowest, specially at the middle area of canal extensions in group A, and that was statistically significant difference from other groups. In conclusion, the ultrasonic file, lentulo spiral and EZ-Fill bi-directional spiral were effective methods of sealer placement in simulated canal extensions. The K file was the least effective method, specially at the middle area of canal extensions.

The purpose of this study was to investigate the bonding of resin-based root canal sealer, AH26 when the sealer was applied as a thin layer between dentine and gutta-percha surface.

In this study, forty non-caries extracted human molars and resin-based root canal sealer(AH 26, DeTrey/Dentsply, Germany) were used. Disks of gutta-percha, 6mm in diameter·6mm thick (Diadent/Dentsply, Korea) for thermoplastic obturation were used and dentin surfaces were treated with 2% NaOCl(Group 1) or 2%NaOCl+17% EDTA(Group 3). Disks of gutta-percha, 6mm in diameter·6mm thick (Diadent/Dentsply, Korea) for conventional obturation were used and dentin surface were treated with 2% NaOCl(Group 2) or 2%NaOCl+17% EDTA(Group 4). Enamel was removed by a horizontal section 1mm below the deepest portion of the central occlusal groove by using a water-cooled low speed diamond saw. A second horizontal section was done around cementoenamel junction. Exposed dentin surface was cut to approximately 8×8 mm rectangular shape and was ground against 320, 400, 600 grade silicon carbide abrasive paper serially. After grinding, the dentine surface were soaked in a solution of 2% NaOCl for 30 minutes and twenty of specimens were treated with 17% EDTA solution for 1 minute. The treated specimens were washed and dried. Root canal sealer, AH26 was prepared according to the manufacture's instructions. The Gutta-percha and dentin surface were coated with a thin layer of the freshly mixed sealer. The specimens were left overnight at room temperature. After their initial set, they were transferred to an incubator at 37℃ for 72 h. After 72 hours, resin blocks were made. The resin block was serially sectioned vertically into stick of 1·1mm. Twenty sticks were prepared from each group.

After that, tensile bond strength for each stick was measured with Microtensile Tester. Failure patterns of the specimens at the interface between gutta-percha and dentin were observed under the SEM(×1000) and Stereomicroscope (LEICA M420, Meyer Inst., TX U.S.A) at 1.25 ×25 magnification. The results were statistically analysed by using a One-way ANOVA and Tukey's test.

The results were as follows;

1. Tensile bond strengths(mean±SD) were expressed with ascending order as follows: Group 1, 3.09±1.05MPa ; Group 2, 6.23±1.16MPa ; Group 3, 7.12±1.07MPa ; Group 4, 10.32±2.06MPa.

2. Tensile bond strengths of the group 2 and 4 used disks of gutta-percha for conventional obturation were significantly higher than that of the group 1 and 3 used for thermoplastic obturation. (p < 0.05)

3. Tensile bond strengths of the group 3 and 4 treated with 2% NaOCl+17% EDTA were significantly higher than that of the group 1 and 2 treated with 2% NaOCl. (p < 0.05)

4. In analysis of failure patterns at the interface between sealer and gutta-percha, there were observed 49 (61%)cases of adhesive failure patterns and 31(39%) cases of mixed failures patterns.

Compomer is composed of matrix and filler; matrix is made of the combination of resins and polycarboxylic molecules that are light-cured, and a filler is a glass component which is capable of ion-release. The resin content of compomers produces polymerization shrinkage which can adversely affect marginal adaptation. Pretreatment is a fundamental step which is treated with conditioner or primer in the use of these materials.

Microleakage of restorative materials has been investigated mostly by dye penetration method. Dye penetration method was not quantitative and not measured repeatedly. Fluid filtration method, introduced and developed by Pashley's group, has been extensively used for 20 years for research purpose to understand the physiology of dentin, as well as the effects of various restorative treatments on dentin permeability. It permits quantitative, nondestructive measurment of microleakage in a longitudinal manner. The purpose of this study was to evaluate the change of dentin permeability according to the process of compomer restoration.

In this study, ClV cavities were prepared on buccal surface of thirty extracted human molars. The prepared cavities were etched by 37% phosphoric acid. The experimental teeth were randomly divided into three groups. Each group was treated with following materials; Group 1 : Prime & Bond NT/Dyract AP, Group2 : Single Bond/F2000 compomer, Group 3 : Syntac Single Component/Compoglass. The bonding agent and compomer were applied for each group following manufacturers information. Dentin permeability of each group was measured at each process by fluid filtration method; Step 1 : preparation(smear layer), Step 2 : etching(smear layer removal), Step 3 : applying the bonding agent, Step 4 : filling the compomer. Dentin permeability was expressed by hydraulic conductance(µl min^-1cmH₂O^-1).

The data were analysed statistically using One-way ANOVA and Sheffe's method.

The results were as follows :

1. Dentin permeability differences between each process were significant except between step 1 and step 2(p<0.01).

2. Dentin permeability after removal of smear layer was highly increased(p<0.01).

3. In most case, decrease of dentin permeability was obtained by applying bonding agent(p<0.01).

4. Dentin permeability differences among the experimental groups were not significant(p>0.05).

5. None of compomers used in this study showed perfect seal at the interface.

The purposes of this study were to evaluate the microtensile bond strength of one-step adhesives according to various dentin surface treatments and to observe the interface between resin(Z-100™) and dentin under SEM.

In this study forty-five non-caries extracted human molars and three adhesive systems were used; All-Bond 2(AB), One-Up Bond F(OU), AQ-Bond(AQ).; In Group 1, 2, 3, AB was used and tooth surfaces were treated by smearing(S), ultrasonic cleansing(US), etching(E) respectively. In Group 4, 5, 6, One-Up Bond F was used and tooth surfaces were also treated as the same way above. In Groups 7, 8, 9, AQ Bond was used and tooth surfaces were treated as the same way. Each specimen was prepared for microtensile bond testing, and were stored for 24hrs in 37℃ distilled water. After that, microtensile bond strength for each specimen was measured. Specimens were fabricated to examine the failure patterns of interface between resin and dentin and observed under the SEM.

The results were as follows;

1. The results(mean±SD) of microtensile test were group 1, 25.69±4.31MPa; group 2, 40.93±10.94MPa; group 3, 47.65±8.85MPa; group 4, 36.98±9.14MPa; group 5, 39.66±8.45MPa; group 6, 43.26±13.01MPa; group 7, 25.07±4.2MPa; group 8, 30.4±4.74MPa; group 9, 33.61±7.88MPa.

2. One-Up Bond F was showed the highest value of 36.98±9.14MPa in dentin surface treatment with smearing, and there were significant differences to the other groups(p<0.05).

3. All-Bond 2 was showed the highest value of 40.93±10.94MPa in dentin surface treatment with ultrasonic cleansing, but was no significant difference to One-Up Bond F(p>0.05).

4. All-Bond 2 was showed the highest value of 47.65±8.85MPa in dentin surface treatment with etching(10%phosphoric acid), and there were significant differences to the other groups(p<0.05).

5. All-Bond 2 was showed the highest value of 47.65±8.85MPa in dentin surface treatment according to manufacture's directions, but was no significant difference to One-Up Bond F(p>0.05).

6. AQ Bond was showed the lowest microtensile bond strength with various dentin surface treatment, and the were significant differences to the other groups(p<0.05).

Leakage studies have been performed frequently, since a fluid-tight seal provided by various dental filling materials has been considered clinically important. The leakage of the various root-end filling materials has been widely investigated mostly dye penetration method. These dye studies cannot offer any information about the quality of the seal of a test material over a long period of time The purpose of this study was to evaluate the microleakage of root end cavities in blood contamination filled amalgam, intermediate restorative material(IRM), light cured glass ionomer cement(GI) and mineral trioxide aggregate(MTA) by means of a modified fluid transport model. Fifty standard human root sections, each 5mm high and with a central pulp lumen of 3mm in diameter, were and filled with our commonly used or potential root end filling materials after they were contaminated with blood. At 24h, 72h, 1, 2, 4, 8, and 12 weeks after filling, leakage along these filling materials was determined under a low pressure of 10KPa(0.1atm) using a fluid transport model.

The results were as follows:

1. MTA group showed a tendency of decreasing percent of gross leakage (20ml/day) in process of time, whereas the other materials showed a tendency of increasing in the process time.

2. At the all time interval, GI group leaked significantly less than amalgam group and IRM group (p<0.05).

3. At the 4 weeks, the percentage of gross leakage in MTA group decreased to 0% thereafter, the low percentage of gross leakage was maintained in MTA group until the end of the experiment, whereas the percentage in IRM group increased to 100%.

4. At the 12 weeks, percentage of gross leakage was significantly low in MTA group(0%), comparison with GI group(40%), amalgam group(90%) and IRM group(100%), but there was no significant difference between latter two materials.

Physical properties of composite resins such as strength, resistance to wear, discoloration, etc depend on the degree of conversion of the resin components. The purpose of this study was to evaluate the degree of conversion of the composite resins according to the thickness of tooth structure penetrated by light and applied light curing time. The coronal portions of extracted human teeth (one anterior tooth, three posterior tooth) was embedded by pink denture material. the mounted teeth were cut into three illumination sections (1mm thickness enamel section, 1mm thickness dentin section, 2mm thicknes dentin section) and one backing section with cutting wheel. Thin resin films were made by using 6kg pressure between slide glass during 5 minutes.

Thin resin film was light cured on coupled illumination section during 40sec, 80sec and 120sec. each illumination section was coupled as follows; no tooth structure(X), ename section(E), enamel section + 1mm dentin section(ED1), enamel section + 2mm dentin section(ED2), enamel section + 1mm dentin section + 2mm dentin section(EDD). To simulate the clinical situation more closely, thin resin film was cured against a backing section of tooth structure. The degree of conversion of carbon double bonds to single bonds in the resin films were examined by means of Fourier Transform Infrared Spectrometer. The results were obtained as follows;

1. As curing time was increased, conversion rate was increased and as tooth thickness which was penetrated by curing light was increased, conversion rate was decreased.

2. At all tooth thickness groups, conversion rate between 80sec and 120sec was not significantly increased(P>0.05).

3. At 40sec group and 80sec, conversion rate between no tooth structure(X) group and 1mm enamel section(E) group was not significantly decreased(P>0.05).

4. At 80sec group and 120sec, conversion rate between 1mm enamel section(E) group and 1mm enamel section + 1mm dentin section(ED1) group was not significantly decreased(P>0.05).

The purpose of this study was to compare the shaping time of two shaping methods and the leakage of three different obturation techniques. Ninty three canaled human molar teeth were used, which were randomly divided into two groups of forty teeth each and ten control teeth. After working length determination, the one group was prepared crown-down technique using rotary root canal instruments of GT rotary files .12/20, .10/20, .08/20 and .06/20 taper(Maillefer Instrument SA. Switzerland). The other group was instrumented with Gates Glidden burs(#1, #2, and #3) to coronal preparation and GT rotary files .08/20 and .06/20 taper to apical preparation. Shaping time was measured.

After root canals were instrumented, they were divided to three subgroups and obturated as follows: Subgroup 1, obturated with single cone method : Subgroup 2, obturated with lateral condensation : Subgroup 3, obturated with continuous wave technique. Three subgroups were obturated using non-standardized gutta-percha cone(Diadent, Korea, .06 or .08 taper) and AH-26(Dentsply DeTrey, Germany) as a root canal cement.

Ten unobturated teeth served as positive and negative controls. After immersion in 2% methylene blue solution for 1 month, the teeth were washed during 24h. The teeth were demineralized in 10% nitric acid and dehydrated by immersion in 80, 90 and 100% ethyl alcohol. The teeth were finally cleared and stored in 100%methylsalicylate, and apical dye penetration was evaluated under stereomicroscope(Leica M420, LC, U.S.A)at ×8.75 magnification.

Liner measurement of dye penetration was assessed with the use of digitalized image analysing system (analySIS, GmbH, Germany). The data were analysed statistically using independent T-test and Two-way ANOVA and Tukey test. The result were as follows:

In canal prepared with GT™rotary file, shaphing time taked more than the group of using Gates Glidden drill to coronal preparation without statistical significance (p>0.05).