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).

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).