The purpose of this study was to evaluate the efficiency of the preparation of oval canals using hand and engine-driven instruments with SEM observation. Thirty single-rooted teeth with oval canal were used in this study. The teeth were divided into 3 groups. In group A, the teeth were instrumented up to a size 35 K-file using RC-prep and irrigated with 5% NaOCl between each file size. In group B, the teeth were instrumented with Profile according to the manufacture's instructions using RC-Prep and irrigated with 5% NaOCl between each file size. In group C, the teeth were instrumented with GT file according to the manufacture's instructions using RC-prep and irrigated with 5% NaOCl between each file size. Then, in all teeth, a final flush of 5ml of distilled water delivered for 30s. Canals were dried with sterile standardized paper points. After preparing the canals, the teeth were sectioned along their mesial and diatal surfaces by using low-speed diamond disc, chisel and mallet. Each root section was then dehydrated in graded concentration of alcohol (70, 80, 90, 100%), mounted on an aluminum stub, sputter-coated with gold-palladium and observed with scanning electron microscope (HITACHI S-4200) in middle and apical area.

The results of this study were as follows:

In the middle area, group B and group C showed less smear layer than group A, and it was statistically significant (p < 0.05).

The purpose of this study was to investigate the quantity of debris which was extruded apically after canal instrumentation using different types of enlarging instrument in endodontic resin models.

Five groups of 9 endodontic resin models were instrumented using each different technique: hand instrumentation without early coronal flaring, hand instrumentation after early coronal flaring, and three nickel-titanium engine-driven instrumentations (Hero 642, Protaper, K³). Debris extruded from apical foramen during instrumentation was collected on preweighed CBC bottle, desiccated and weighted using electronic balance. The results were analyzed using Kruskal-wallis test and Mann-Whitney U rank sum test at a significance level of 0.05.

The results were as follows:

All of instrumentation techniques produced apically extruded debris.

The early coronal flaring is very important to reduce the amount of debris extruded apically.

This study investigated that the effect of rewetting agent on dentinal microtensile bond strength (µTBS). Human molars were sectioned to expose the superficial dentin surfaces.

Samples were divided into two groups according to type of adhesives-Single Bond (S) and One-Step (O)], and again subdivided into five groups by different dentin surface treatment-dry for 15s (D), blot dry (BD) or dry for 15s, and rewet with different rewetting agents [distilled water (DW), Gluma Desensitizer (GD) and Aqua-Prep (AP)] for 30s. After application of adhesive, composite resin was built up on the bonding surface. Each tooth was sectioned to obtain stick with 1 mm² cross sectional area and the µTBS was determined by EZ test.

In the S group, the mean µTBS of GD, AP and BD group was significantly higher than that of DW and D group (p < 0.05). In the O group, the mean µTBS of AP, GD, BD and DW group was significantly higher than that of D group (p < 0.05).

The data suggested that Gluma Desensitizer and Aqua-Prep could be successfully used as rewetting agents, and Distilled water could be acceptable in aceton based adhesive system only.

This study evaluated the marginal microleakage of five single step adhesives. Class V cavity preparations with occlusal margins in enamel and gingival margins in dentin were prepared on both buccal and lingual surfaces of extracted human molar teeth. Prepared teeth were randomly divided into five groups and restored using one of the single step adhesives and composite resins: Prompt L-Pop/Filtek Z-250 (Group 1), AQ Bond/Metafil CX (Group 2), One-Up Bond F/Palfique Toughwell (Group 3), Futurabond/Admira (Group 4), Xeno III/Spectrum TPH (Group 5).

The restored teeth were thermocycled. Microleakage was assessed by dye penetration using 2% methylene blue dye solution. The teeth were bisected buccolingually and evaluated for microleakage under steromicroscope. The data were statistically analysed by Kruskal-Wallis test and Mann-Whitney tests.

The results of this study were as follows;

Microleakage of enamel margins in group 3 was statistically higher than that in groups 1, 2, 4, 5 (p < 0.05).

In conclusion, Prompt L-Pop showed the least leakage at enamel margin, and AQ Bond showed at dentin margin in this study. Marginal miroleakage in dentin was higher than that in enamel.

The purposes of this study were to estimate the material properties of the recently developed domestic composite resins for core filling material (Chemical, Dual A, Dual B; Vericom, Korea) and to compare them with other marketed foreign products (CorePaste, Den-Mat, USA; Ti-Core, Essential Dental Systems, USA; Support, SCI-Pharm, USA). Six assessments were made; working time, setting time, depth of polymerization, flexural strength, bonding strength, and marginal leakage. All items were compared to ISO standards.

All domestic products satisfied the minimum requirements from ISO standards (working time: above 90 seconds, setting time: within 5 minutes), and showed significantly higher flexural strength than Core Paste. Dual A and B could, especially, reduce the setting time to 60 seconds when cured with 600 mW/cm² light intensity. All experimental materials showed 6 mm depth of polymerization.

Bond strengths of Ti-Core and Dual B materials were significantly higher than the other materials. Furthermore, three domestic products and Ti-Core could reduce the microleakage effectively.