This study investigated the influence of IRM on marginal microleakage of 5th generation adhesives. Class V cavities with gingival margins in dentin were prepared on both buccal and lingual surfaces of 60 extracted human molar teeth. Prepared teeth were randomly divided into six groups. Group 1 and 4 received no temporary restoration with IRM. Group 2 and 5 were covered with IRM mixed at P/L ratio(10g/1g). Group 3 and 6 were covered with IRM mixed at P/L ratio(10g/2g). The temporary restorations were removed mechanically with an ultrasonic scaler after one-week storage in distilled water. The cavities were restored using one of two adhesives and composites; Single Bond/Filtek Z 250(Group 1, 2 and 3), UniFil Bond/UniFil F(Group 4, 5 and 6).

Following one day storage in distilled water, the restored teeth were thermocycled for 500 cycles(between 5℃ and 55℃) and immersed in 2% methylene blue for dye penetration testing. The results were analysed using Kruskal-Wallis Test, Mann-Whitney and Wilcoxon signed ranked test at a significance level of 0.05.

The results of this study were as follows:

1. Ranking of mean microleakage scores at the enamel margins was Group 1<Group 3<Group 2<Group 4<Group 5<Group 6. The microleakage of Group 6 was significantly higher than that of Groups 1, 2 and 3(p<0.05).

2. At the enamel margins, without regard to pretreatment with IRM, the microleakage of Single Bond was lower than that of UniFil Bond.

3. Ranking of mean microleakage scores at the dentin margins was Group 4<Group 1<Group 5<Group 6<Group 3<Group 2. But there were no significant difference among microleakages of each group(p>0.05).

4. At the dentin margins, the microleakage of the group not pretreated with IRM was lower than that of the group pretreated with IRM. And the microleakage of UniFil Bond was lower than that of Single Bond.

5. Compared with microleakages between the enamel and dentin margins of each groups, Group 1, 2, 3, 4, 5 and 6 at dentin margin were higher microleakage than those at enamel margin. There were significant difference between enamel and dentin microleakage of Group 2 and 3(p<0.05).

This study compared the dentin adhesion to composite resin according to air-dry, blot dry, application of rewetting agent on air-dry or blot dry dentin surface by microleakag test and SEM observation.

For microleakage test, class V cavity preparations with dentinal margins were prepared on both buccal and lingual surfaces of 40 extracted human molars. For SEM observation, occlusal dentin of 20 extracted human molars were exposed.

After etched the dentin, prepared teeth were randomly divided into four groups;

D group: air dry for 10-15 sec., B group: blot dry with moist cotton pellet, D-R group: air dry and rewet with Aqua-Prep F for 20 sec., B-R group: blot dry and rewet with Aqua-Prep F for 20 sec.

Treated cavities and surfaces were filled or constructed using One-Step adhesives and Aelitefil composite resins. Specimens were stored in distilled water for 24 hours. For microleakage test, the specimens were thermocycled and soaked into 2% methylene blue. The specimens were sectioned longitudinally and evaluated for microleakage under steromicroscope. The data were statistically analysed by Kruskal-Wallis Test, Mann-Whitney and Wilcoxon signed ranked tests. For SEM observation, the specimens were bisectioned mesiodiatally. After decalcified and deproteinized, specimens were observed under SEM.

The results of this study were as follows;

1. The microleakges on dentinal margin were the highest in D group compared with B group, D-R group, and B-R group(p<0.05). But there was no significant difference between B group, D-R group and B-R group.

2. D group showed gap and a few resin tags between dentin and composite resin.

3. B group, D-R group, and B-R groups showed close adaptation between dentin and composite resin. It showed that resin rags in B group were numerous and long, in D-R group were few and short, in B-R group were numerous and short or long.

4. Adhesive layer showed in D-R group (10 µm) and B-R group (3 µm)

In conclusion, use of rewetting agent to dry dentin was efficient to dentin adhesion, also it did not provide reverse effect on blot dry dentin.

The purpose of this study was to compare in vitro interfacial relationship of restorations bonded with three self-etching primer adhesives and one self-etching adhesive.

Class I cavity preparations were prepared on twenty extracted human molars. Prepared teeth were divided into four groups and restored with four adhesives and composites: Clearfil SE Bond/Clearfil™ AP-X (SE), UniFil Bond/UniFil® F (UF), FL Bond/Filtek™ Z 250 (FL) and Prompt L-Pop/Filtek™ Z 250 (LP)

After storing in distilled water of room temperature for 24 hours, the specimens were vertically sectioned and decalcified. Morphological patterns between the enamel/dentin and adhesives were observed under SEM.

The results of this study were as follows;

1. They showed close adaptation between enamel and SE, UF and FL except for LP.

2. The hybrid layer in dentin was 2 µm thick in SE, 1.5 µm thick in UF, and 0.4 µm in both FL and LP. So, the hybrid layers of SE and UF were slightly thicker than that of FL and LP.

3. The lengths and diameters of resin tags in UF and FL were similar, but those of LP were slightly shorter and slenderer than those of SE.

4. The resin tags were long rod shape in SE, and funnel shape in other groups.

Within the limitations of this study, it was concluded that self-etching primer adhesives showed close adaptation on enamel. In addition, the thickness of hybrid layer ranged from 0.4-1.5 µm between adhesives and dentin. The resin tags were long rod or funnel shape, and dimension of them was similar or different among adhesives.

Chewing simulator, which can partly mimic the motion of chewing motion of human, has been successfully developed. The purpose of its development was to make a new machine which can anticipate the clinical results of restoration in the human teeth more accurately in vitro condition It is composed of 4 major parts; chewing part, motor part, water bath, controlling part. The controlling part control the chewing force, frequency, the temperature and running time of water. Additionally, the actual chewing force and remaining time is shown in the monitor of controlling part. At present, the chewing cycle is composed depending on the pre-published data of foreign people. Long term clinical data should be additionally collected for the simulator to mimic the clinical results more accurately.

There are increasing usage of Nickel-Titanium rotary files in modern clinical endodontic treatment because it is effective and faster than hand filing due to reduced step.

This study was conducted to evaluate the effect of canal preparations using 3 different rotary Nickel-Titanium files that has different cross sectional shape and taper on the maintenance of canal curvature. Simulated resin block were instrumented with Profile(Dentsply, USA), GT rotary files(Dentsply, USA), Hero 642(Micro-Mega, France), and Pro-Taper(Dentsply, USA).

The image of Pre-instrumentation and Post-instrumentation were acquired using digital camera and overspreaded in the computer. Then the total differences of canal diameter, deviation at the outer portion of curvature, deviation at the inner portion of curvature, movement of center of the canal and the centering ratio at the pre-determined level from the apex were measured.

Results were statistically analyzed by means of ANOVA, followed by Scheffe test at a significance level of 0.05.

The results were as follows;

1. Deviation at the outer portion of curvature, deviation at the inner portion of curvature were showed largest in Pro-Taper, so also did in the total differences of canal diameter(p<0.05).

2. All the groups showed movements of center. Profile combined with GT rotary files and Hero 642 has no difference but Pro-Taper showed the most deviation(p<0.05).

3. At the 1, 2, 3mm level from the apex movements of center directed toward the outer portion of curvature, but in 4, 5 mm level directed toward the inner portion of curvature(p<0.05).

As a results of this study, it could be concluded that combined use of other Nickel-Titanium rotary files is strongly recommended when use Pro-Taper file because it could be remove too much canal structure and also made more deviation of canal curvature than others.

The purpose of this study was to evaluate the effects of EDTA and pulsed Nd:YAG laser on apical leakage of canal obturation. Forty-eight single-rooted teeth were used in this study. The teeth were instrumented up to a size 40 K-file and irrigated with 2.5% NaOCl between each file size. And the teeth were divided into 4 groups. In group A, the root canals were irrigated with a final flush of 5ml 2.5% NaOCl as a control group. The teeth in group B were irrigated with a final flush of 5ml 17% EDTA. The teeth in group C and D were irradiated by pulsed Nd:YAG laser(laser parameters were set at 1W, 100mJ, 10Hz, and 2W, 100mJ, 20Hz respectively).

The results were as follows:

1. Apical leakage was observed in 50% of samples in group A, 30% of samples in group B, 20% of samples in group C, and 10% of samples in group D.

2. The teeth in group B had less leakage than group A, but there was no statistically significant differences(p>0.05).

3. The teeth in group C, D had less leakage than group A, and there was statistically significant differences(p<0.05).

4. The teeth in group C, D had less leakage than group B, but there was no statistically significant differences(p>0.05).

5. There was no significant differences in apical leakage between group C and group D(p>0.05).

The purpose of the present study were to evaluate microleakage of a fourth generation dentin-bonding agent following a walking bleaching treatment, to determine the effect of temporary postbleaching dressing with calcium hydroxide on microleakage and to investigate the effect of delayed intracoronal restoration on microleakage.

The results of this study were as follows:

1. Bleached groups showed more microleakage than unbleached group.

2. Immediately restored group following bleaching procedure showed the highest microleakage score.

3. One-week delayed restorations showed less microleakage but there were no statistically significant difference between group II and III.

4. Provisional dressing with calcium hydroxide had no influence on microleakage.

It is necessary to know the time that has elapsed from the bleaching treatment to the restoration procedure to achieve optimal seal, as well as to reduce the risk of microleakage in adhesive restoration.

The purpose of this study was to compare the initial apical file(IAF) first file that fits to the apex in each canal before and after early flaring to analyze if the size of file to fit to the apex would increase after flaring. Eighty anterior teeth with complete apical formation and patent foramens were selected. The samples were randomly divided into 4 groups(GG, OS, GT, PT Group) of 20 teeth each. A file was fit to the apex in each canal and that size recorded. Radicular flaring were completed using different types of instruments. After flaring a file was again fit to the apex in the same manner as before and its size recorded.

The results of this study were as follows:

1. The mean diameter of IAF before flaring(file diameters in mm×10^-2) was 19.81±8.32 before and 25.94±9.21 after(p<0.05).

2. The increase in diameter of IAF was approximately one file size for all groups.

3. Ranking of increasing diameter of IAF were GG>GT>OS>PT group. There was a statistically significant difference between before and after flaring(p<0.05).

4. Ranking of the time for flaring were GG>GT>OS>PT group. There was a statistically significant difference between GG group and other groups(p<0.05).

5. In the case without change of IAF diameter, they showed decrease in force after flaring when IAF was pulled out from root canal(p<0.05).

This study suggested that early radicular flaring increases the file size that is snug at the apex, and awareness of that difference gives the clinician a better sense of canal size. Early flaring of the canal provides better apical size information and with this awareness, a better decision can be made concerning the appropriate final diameter needed for complete apical shaping.

The objective of this in vitro study was to evaluate the efficacy of a Ca(OH)₂ removal before and after early coronal flaring using different types of instruments. 100 plastic blocks with 30° artificial curved canals were used in this study and randomly divided into a control group and 4 experimental groups(GG, OS, GT, PT Group) 20 teeth each. The canals were instrumented, and Ca(OH)₂ was temporary filled into the each canal. Irrigation was performed with Max-i-Probe 25-, 30-gauge probes before and after recapitulation.

The results of this study were as follows:

1. There were no significant difference among the groups in size of irrigating needle(p<0.05).

2. There was a significant difference between before and after recapitulation regardless size of irrigating needle(p<0.05).

3. Before recapitulation, there was a significant difference between 25- and 30-gauge needle in all groups(p<0.05).

4. After recapitulation, there was a significant difference between 25- and 30-gauge needle in the control group(p<0.05). But there were no significant difference among the experimental groups.

It is concluded that the effectiveness of canal irrigation was decided to the depth of irrigating needle into the canal. The effect of canal irrigation tend to facilitate by the early coronal flaring. The recapitulation was the most effective during canal irrigation regardless the size of irrigating needle. Therefore, the recapitulation is a mandatory way to facilitate the effectiveness of canal irrigation during canal enlargement.

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.