The purpose of this study was to evaluate the effect of dual bonding technique by comparing micro-shear bond strength between two different luting methods of resin cement to tooth dentin. Three dentin bonding systems(All-Bond 2, One-Step, Clearfil SE Bond), two temporary cements (Propac, Freegenol) were used in this study.

In groups used conventional luting procedure, dentin surfaces were left untreated. In groups used dual bonding technique, three dentin bonding systems were applied to each dentin surface. All specimens were covered with each temporary cement. The temporary cements were removed and each group was treated using one of three different dentin bonding system. A resin cement was applied to the glass cylinder surface and the cylinder was bonded to the dentin surface. Then, micro-shear bond strength test was performed. For the evaluation of the morphology at the resin/dentin interface, SEM examination was also performed.

Conventional luting procedure showed higher micro-shear bond strengths than dual boning technique. However, there were no significant differences.

The purpose of this study was to evaluate the canal configuration after shaping by ProFile, ProTaper and K-Flexofile in simulated resin canals with different angles of curvature.

Three types of instruments were used : ProFile, ProTaper, K-Flexofile. Simulated root canals, which were made of epoxy resin, were prepared by ProFile, ProTaper with rotary instrument using a crown-down pressureless technique, and hand instrumentation was performed by K-Flexofile using a step-back technique. All simulated canals were prepared up to size 25 file at end-point of preparation. Pre and post instrumentation images were recorded with Scanner. Assessment of canal shape was completed with Image Analysis program. Measurements were made at 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 mm from the apex. At each level, outer canal width, inner canal width, total canal width, and amount of transportation from original axis were recorded. Instrument deformation and fracture were recorded. Data were analyzed by means of one-way ANOVA analysis of variance and the Sheffe's test.

The result was that ProFile and ProTaper maintain original canal shape regardless of the increase of angle of curvature than K-Flexofile. ProFile show significantly less canal transportation and maintained original canal shape better than ProTaper.

The purpose of this study was to evaluate which type of Ni-Ti files are able to maintain canal configuration better in the simulated canal with abrupt curvature near it's apex.

Ninety six simulated root canals were made in epoxy resin and #15 finger spreader was used as root canal templates. The simulated root canals were made with radius of curvature of 1.5 mm, 3.0 mm, 4.0 mm, 6.0 mm respectively and the angle of curvature of all simulated canals were adjusted to 90 degree. The simulated canals were instrumented by ProFile, ProTaper, Hero 642, and K³ at a 300 rpm using crown-down pressureless technique. Pre-instrumented and post-instrumented images were taken by digital camera and were superimposed with Adobe Photoshop 6.0 program. Images were compared by image analysis program.

The changes of canal width at the inner and outer side of the canal curvature, canal transportation were measured at 9 measuring point with 1 mm interval. Statistical analysis among the types of Ni-Ti files was performed using Kruskal-Wallis test and Mann-Whitney U-test.

The result was that ProFile maintain original canal configuration better than other engine driven Ni-Ti files in the canals above 3.0 mm radius of curvature, and in the 1.5 mm radius of curvature, most of Ni-Ti flies were deformed or separated during instrumentation.

This study compared the microtensile bond strength (µTBS) of three single step adhesives to dentin.

Occlusal superficial dentin was exposed in fifteen human molars. They were assigned to three groups by used adhesives: Xeno group (Xeno III), Prompt group (Adper Prompt L-Pop), AQ group (AQ Bond).

Each adhesive was applied to dentin surface, and composite of same manufacturer was constructed. The bonded specimens were sectioned into sticks with an interface area approximately 1 mm², and subjected to µTBS testing with a crosshead speed of 1 mm/minute. The results of this study were as follows;

The µTBS to dentin was 48.78 ± 9.83 MPa for Xeno III, 30.22 ± 4.52 MPa for Adper Prompt L-Pop, and 26.31 ± 7.07 MPa for AQ Bond.

The mean µTBS of Xeno group was significantly higher than that of Prompt group and AQ group (p < 0.05).

There was no significant difference between the µTBS of Prompt group and AQ group.

This study compared the microtensile bond strength (µTBS) of single step adhesives to different dentin depths.

Superficial or deep dentin was exposed in 30 molar teeth by sectioning immediately under the DEJ or 1.5 mm area from central pit, respectively. After polishing with 600-grit SiC paper, the dentin surfaces were assigned to three groups: AQ group-AQ Bond, L-Pop group-Adper Prompt L-Pop, Xeno group-Xeno III.

The bonded specimens were sectioned into sticks and subjected to µTBS testing with a crosshead speed of 1 mm/minute. The results of this study were as follows;

The µTBS to superficial dentin was higher than that to deep dentin in all group.

The µTBS of Xeno group was significantly higher than that of L-Pop group and AQ group in both superficial and deep dentin (p < 0.05).

This study investigated the effect of anticurvature filing method on preparation of the curved root canal using ProFile.

Thirty six resin blocks were divided equally into three groups by instrumentation motions: anticurvature filing motion, circumferential filing motion and straight up-and-down motion. Each resin block was sectioned at 8 mm level from the apex and at the greatest curvature of the canal and reassembled in metal mold by a modified Bramante technique. All groups were instrumented with the ProFile system. At each levels, image of sectioned surface were taken using CCD camera under a stereomicroscope at ×40 magnification and stored. Distances of transportation at the inner and outer area of curvature and the centering ratio were determined and compared by statistical analysis, along with the assessment of the increase of root canal cross-sectional area.

The results were as follows;

1. In all groups, there was no statistical difference in the mean increase of root canal cross-sectional area, the centering ratio, and the mean distances of transportation at the inner area of curvature at each level.

2. At 8 mm level from the apex, the mean distances of transportation at the outer area of curvature decreases in following order anticurvature filing motion, circumferential filing motion, straight up-and-down motion but, no significant difference at the greatest curvature of the canal among three groups.

Effect of anticurvature filing motion using ProFile does not seem to be different from other instrumentation motions at the inner area of curvature in curved root canal.

Hemolytic property is a specific feature of bacteria to obtain iron which is essential for its survival in host tissues. Therefore, it is thought to be one of several factors of virulence. The purpose of this study was to investigate the hemolytic properties of Prevotella nigrescens isolated from the teeth diagnosed as pulp necrosis and apical periodontitis under the presence of hemolysin inhibitors such as NaN₃ and dithiothreitol, heat, various pH and cultural conditions.

The results were as follows;

1. Clinically isolated P. nigrescens strains and standard P. nigrscens ATCC 33563 showed hemolytic activity.

2. P. nigrescens showed higher hemolytic activity against human erythrocytes than sheep or horse erythrocytes.

3. NaN₃ and dithiothreitol (DTT) reduced the hemolytic activity of P. nigrescens in a dose dependent manner (p < 0.05).

4. Optimal pH for the maximum hemolytic activity of P. nigrescens was 4.0 and the hemolysin was stable under the 50℃, but the hemolytic activity was significantly decreased at 95℃.

5. P. nigrescens cultured in 10% CO₂ condition showed higher hemolytic activity than the bacteria cultured in the anaerobic condition.

This study compared the microshear bond strength (µSBS) to end and side of enamel rod bonded by four adhesives including two total etch adhesives and two self-etch adhesives.

Crown segments of extracted human molars were cut mesiodistally. The outer buccal or lingual surface was used as specimens cutting the ends of enamel rods, and inner slabs used as specimens cutting the sides of enamel rods.

They were assigned to four groups by used adhesives: Group 1 (All-Bond 2), Group 2 (Single Bond), Group 3 (Tyrian SPE/One-Step Plus), Group 4 (Adper Prompt L-Pop). After each adhesive was applied to enamel surface, three composite cylinders were adhered to it of each specimen using Tygon tube. After storage in distilled water for 24 hours, the bonded specimens were subjected to µSBS testing with a crosshead speed of 1 mm/minute. The results of this study were as follows;

1. The µSBS of Group 2 (16.50 ± 2.31 _MPa) and Group 4 (15.83 ± 2.33 _MPa) to the end of enamel prism was significantly higher than that of Group 1 (11.93 ± 2.25 _MPa) and Group 3 (11.97 ± 2.05 _MPa) (p < 0.05).

2. The µSBS of Group 2 (13.43 ± 2.93 _MPa) to the side of enamel prism was significantly higher than that of Group 1 (8.64 ± 1.53 _MPa), Group 3 (9.69 ± 1.80 _MPa), and Group 4 (10.56 ± 1.75 _MPa) (p < 0.05).

3. The mean µSBS to the end of enamel rod was significantly higher than that to the side of enamel rod in all group (p < 0.05).