The purpose of this study was to compare the microhardness and the fluoride content of enamel and dentin around fluoride- or non fluoride-containing restorations. Forty extracted human teeth were used and prepared cervical cavities on proximal surface. Experimental teeth were divided into five groups. Group 1 : Prime & Bond NT and Z100, Group 2 : Prime & Bond NT and F2000, Group 3 : Scotchbond Multi-Purpose and Z100, Group 4 : Scothcbond Multi-purpose and F2000, Group 5 : Fuji II LC. The cavities were filled with dentin adhesives and restorative materials. After each tooth was bisected, one half was tested microhardness and the other half was analyzed the fluoride at the enamel and dentin by an EPMA-WDX device. The results were as follows:

1. There was no statistical difference among the microhardness of enamel surface in all group.

2. The microhardness at dentin of 100 µm point in Group 2 and 20 µm point in Group 4 was lower than that of normal dentin (p>0.05).

3. There was no statistical difference among the fluoride content of enamel surface in all group.

4. The fluoride content at the dentin of 30 µm point in Group 2 and 5 were higher than those at 100 µm and 200 µm point in Group 2 and normal dentin (p<0.05).

5. At the dentin of 30 µm point, Group 2 showed higher fluoride content than Group 1 and 3, and Group 5 showed higher fluoride content than other groups.

This study compared the shaping ability of nickel-titanium rotary files with different rake angle and radial land.

The nickel-titanium files used in this study were Profile(Dentsply, Maillefer, Ballaigues, Switzerland), Hero 642(Micromega, Besancon, France), and K3(SybronEndo, Glendora, Ca, USA) file. Resin blocks substituted for root canals. 36 resin blocks were divided into 3 groups with 12 canals each. The time for canal preparation was recorded. The images of pre- and postoperative resin canal were scanned and those were superimposed. Amounts of canal deviation, total canal widths, inner canal widths, and outer canal widths were measured at apical 1, 2, 3, 4, 5, 6, and 7mm levels.

The amount of canal deviation was the smallest in Profile group, and the time for canal preparation was the shortest in Hero 642 group. K3 group resulted in competent characteristics in both measurements. Positive rake angle seemed to result in fast shaping of root canal and radial land guide the instrument in center of the canals and around curvatures. Radial land also tended to reduce the sense of screwing into the root canal.

The proper selection of the nickel-titanium file based on the knowledge about file design is needed for the safer, simpler and faster root canal therapy.

The objectives of this study was to evaluate current visible light curing units regarding microhardness and microleakage. Fourty samples of composite resin(Z-250, 3M) were cured by different light curing units(Flipo, LOKKI; Credi II, 3M; XL 3000, 3M; Optilux 500,Demetron) in acrylic blocks. Microhardness was measured using a calibrated Vickers indenter on both top and bottom surfaces after 24 hours of storage in air at room temperature. Class V cavities were prepared on buccal and lingual surfaces of fourty extracted human molars. Each margin was on enamel and dentin/cementum. Composite resin(Z-250, 3M) was filled in cavities and cured by four different light curing units(Flipo, LOKKI; Credi II, 3M; XL 3000, 3M; Optilux 500, Demetron).

The results of this syudy were as follows:

Microhardness

1. Flipo showed low microhardness compared to Optilux 500, Credi II significantly in upper surface. Flipo didn't show a significant difference compared to XL 3000.

2. The microhardness resulting from curing with Flipo was lower than that of others on lower surfaces.

Microleakage

1. Dentin margin showed significantly high dye penetration rate than enamel margin in all groups(p<0.05).

2. No significant differences were found on both enamel and dentin margin regarding curing units.

All-in-one adhesives were recently developed for reducing the techique sensitivity and chair time, but lots of concerns were made on bondability, longevity, and microleakage.

The object of this study was to evaluate microleakage and marginal quality of all-in-one adhesives using electrochemical method and SEM analysis quantitatively.

After making Class V cavities, they were bulk filled with Heliomolar(#A1) after surface treatment with three adhesives: Adper Prompt (Group A), One up bond F (Group O), Xeno III (Group X). Electrical conductivity (microamphere, µA) was checked two times: before and after cavity filling.

Percentage of leaky margin was estimated from SEM image (×1,000).

The data were statistically analysed: ANOVA and Paired T test for electrical conductivity, Kruskal-Wallis and Mann-Whitney test for marginal quality, Spearman's rho test for checking of relationships between 2 methods.

The result were as follows:

1. There was no difference in microleakage between adhesive systems and every specimen showed some of microleakage after filling.

2. Microleakage was reduced about 70% with composite resin filling.

3. Marginal quality was the best in group A, decreasing among groups in the following order: group O, followed by group X. There were significant differences between group A and group X (p=0.015), and between group O and group X (p=0.019).

4. There was no relationship between the microleakage measured by electrochemical method and marginal quality measured by SEM analysis.

Within the results of this study, there was no difference in microleakage among groups by electrical conductivity. However, significant difference in marginal quality was seen among groups. It was believed that these dissimilar results might be induced because of their own characteristics. Analysis of microleakage needs various methods for accuracy.