The aim of this study was to evaluate the microleakage of teeth according to root canal preparation with & without apical enlargement in various size of apical foramen. 60 extracted one canal roots were cross-cutted at 5 mm from root apex and divided into two groups according to their apical foramen size of large (L) and small (S). Each group was subdivided into two groups accordance with their cross-sectional configuration at 5 mm from apex, round (R) and ovoid (O); SR Group, SO Group, LR Group, LO Group. Each group was shaped in .02 taper by Quantec series Nickel-Titanium (NiTi) rotary file, obturated by lateral condensation method. Leakage was measured using a fluid transport model under 40 cmH₂O pressure. After the leakage test, blocks which had showed the leakage retreated with .04 taper and .06 taper and evaluated the degree of fluid filtration in each group. The data was analysed statistically using chi-square test and fisher's exact test.

The results obtained were as follows:

1. Significant difference in leakage was found in groups which had different apical foramen size in .02 taper instrumentation (p < 0.05), but not in .04 taper instrumentation (p > 0.05).

2. The difference in microleakage according to the shape of canal was not evident at 5 mm from apex (p > 0.05).

3. There was correlation between .02 taper instrumentation and .04 taper instrumentation in LR group , LO group (p < 0.05).

This study evaluated the influence of a desensitizer(MS coat) on microtensile bond strength of different adhesives: a three-step adhesive(All-Bond 2), a two-step adhesive(Single Bond), a one-step adhesive(One-up Bond F).

Non-caries extracted human molars were used. Dentin surface was obtained by horizontal section on midportion of crown using a water-cooled low speed diamond saw. Teeth were randomly divided into 6 group. AMO(MS coat + All Bond)-, SMO(MS coat + Single Bond)- and OMO(MS coat + One-up Bond F)-dentin surface were treated with 17% EDTA before bonded adhesive. AMX-, SMX- and OMX-dentin surface were bonded with All-Bond 2, Single Bond and One-up Bond F, respectively, with no previous treatment with MS coat and 17% EDTA. About 1cm high resin composite(Z-250™) were incrementally build-up on the treated surface. The specimens for the microtensile test were serially sectioned perpendicular to the adhesive layer to obtain 0.7×0.7 mm sticks. 30 sticks were prepared from each group.

After that, tensile bond strength for each stick was measured with Microtensile Tester at a 1mm/min crosshead speed. Fractured dentin surfaces were observed under the SEM. The results were statistically analysed by using a One-way ANOVA and Tukey's test(p<0.05).

Value in MPa were: AMO-44.35±13.21; SMO-39.35±13.32; OMO-31.07±10.25; AMX-49.22±16.38; SMX-56.02±13.35; OMX-72.93±16.19. Application of MS coat reduced microtensile bond strengths of both Single Bond and One-up Bond F, whereas microtensile bond strengths of All-Bond 2 were not affected significantly.

Compomer is composed of matrix and filler; matrix is made of the combination of resins and polycarboxylic molecules that are light-cured, and a filler is a glass component which is capable of ion-release. The resin content of compomers produces polymerization shrinkage which can adversely affect marginal adaptation. Pretreatment is a fundamental step which is treated with conditioner or primer in the use of these materials.

Microleakage of restorative materials has been investigated mostly by dye penetration method. Dye penetration method was not quantitative and not measured repeatedly. Fluid filtration method, introduced and developed by Pashley's group, has been extensively used for 20 years for research purpose to understand the physiology of dentin, as well as the effects of various restorative treatments on dentin permeability. It permits quantitative, nondestructive measurment of microleakage in a longitudinal manner. The purpose of this study was to evaluate the change of dentin permeability according to the process of compomer restoration.

In this study, ClV cavities were prepared on buccal surface of thirty extracted human molars. The prepared cavities were etched by 37% phosphoric acid. The experimental teeth were randomly divided into three groups. Each group was treated with following materials; Group 1 : Prime & Bond NT/Dyract AP, Group2 : Single Bond/F2000 compomer, Group 3 : Syntac Single Component/Compoglass. The bonding agent and compomer were applied for each group following manufacturers information. Dentin permeability of each group was measured at each process by fluid filtration method; Step 1 : preparation(smear layer), Step 2 : etching(smear layer removal), Step 3 : applying the bonding agent, Step 4 : filling the compomer. Dentin permeability was expressed by hydraulic conductance(µl min^-1cmH₂O^-1).

The data were analysed statistically using One-way ANOVA and Sheffe's method.

The results were as follows :

1. Dentin permeability differences between each process were significant except between step 1 and step 2(p<0.01).

2. Dentin permeability after removal of smear layer was highly increased(p<0.01).

3. In most case, decrease of dentin permeability was obtained by applying bonding agent(p<0.01).

4. Dentin permeability differences among the experimental groups were not significant(p>0.05).

5. None of compomers used in this study showed perfect seal at the interface.