Present tooth bonding system can be categorized into total etching bonding system (TE) and self-etching boding system (SE) based on their way of smear layer treatment. The purposes of this study were to compare the effectiveness between these two systems and to evaluate the effect of number of themocycling on microleakage of class V composite resin restorations.

Total forty class V cavities were prepared on the single-rooted bovine teeth and were randomly divided into four experimental groups: two kinds of bonding system and another two kinds of thermocycling groups. Half of the cavities were filled with Z250 follwing the use of TE system, Single Bond and another twenty cavities were filled with Metafil and AQ Bond, SE system. All composite restoratives were cured using light curing unit (XL2500, 3M ESPE, St. Paul, MN, USA) for 40 seconds with a light intensity of 600 mW/cm².

Teeth were stored in distilled water for one day at room temperature and were finished and polished with Sof-Lex system. Half of teeth were thermocycled 500 times and the other half were thermocycled 5,000 times between 5℃ and 55℃ for 30 second at each temperature.

Teeth were isolated with two layers of nail varnish except the restoration surface and 1 mm surrounding margins. Electrical conductivity (µA) was recorded in distilled water by electrochemical method. Microleakage scores were compared and analyzed using two-way ANOVA at 95% level.

From this study, following results were obtained: There was no interaction between variables of bonding system and number of thermocycling (p = 0.485). Microleakage was not affected by the number of thermocycling either (p = 0.814). However, Composite restoration of Metafil and AQ Bond, SE bond system showed less microleakage than composite restoration of Z250 and Single Bond, TE bond system (p = 0.005).

This study evaluated the effect of two different calcium hydroxide (Ca(OH)₂) paste removal techniques on the apical leakage of canals obturated with gutta percha cones and sealer after removing a Ca(OH)₂ dressing using an electrochemical method.

Seventy extracted single-rooted teeth were instrumented on with Profile rotary files under NaOCl irrigation. Fifty-eight canals were filled with calcium hydroxide paste, which was then removed using one of the following two techniques. In group A, calcium hydroxide was removed using only NaOCl irrigation, and in group B, the canals were re-prepared with a Profile rotary files-one size larger than the previous instrument and were irrigated with NaOCl. In both groups, the root surfaces were coated twice with nail varnish from CEJ to an area 4 mm away from the apex after canal obturation. Apical leakage was measured using an electrochemical method for 24 days.

All the specimens showed leakage that increased markedly in the first three days. There was no significant difference between the two groups (p > 0.05). The effect of two calcium hydroxide paste removal techniques on the apical leakage was not different during a short period.

The purpose of this study was to evaluate the effect of newly developed endodontic root canal cleanser (MTAD) on the apical leakage of obturated root canal using an electrochemical method.

Canals of 60 extracted single-rooted human teeth were prepared by using a crown-down technique with rotary nickel-titanium files. In Group 1 (positive control group) and 2 (negative control group), 5.25% NaOCl was used as a canal irrigant and no canal wall treatment was done. In group 3, only 5.25% NaOCl were used as canal irrigant, canal wall treatment and final rinse. In group 4, specimens were irrigated with 5.25% NaOCl, treated with 5 ml of 17% EDTA for 5 minutes and final rinsed with 5.25% NaOCl. Specimens of group 5 were irrigated with 1.3% NaOCl and treated with 5 ml of MTAD for 5 minutes. All root canals are dried with paper points and obtuated with gutta-percha and AH plus as a sealer using a continuous wave of condensation technique except in the group 1. The electrical resistance between the standard and experimental electrodes in canals was measured over a period of 10 days. Rising of apical leakage with time was observed for all the groups. Group 4 and 5 showed lower apical leakage than group 3 but differences between the group 3, 4 and 5 were no statistical significance at any measurement time.

The purpose of this study is to evaluate the effect of additional enamel etching with phosphoric acid on the microleakage of the adhesion of self-etching primer system.

Class V cavity(4 mm×3 mm×1.5 mm) preparations with all margins in enamel were prepared on buccal surface of 42 extracted human upper central incisor teeth. Prepared teeth were randomly divided into 3 groups.

Group 1 : no additional pretreatment with 37% phosphoric acid (NE).

Group 2 : additional pretreatment with 37% phosphoric acid for 10 seconds (E10s).

Group 3 : additional pretreatment with 37% phosphoric acid for 20 seconds (E20s).

The adhesives(Clearfil SE Bond®, Kuraray, Osaka, Japan) and composite resins(Clearfil AP-X®, Osaka, Kuraray, Japan) were applied following the manufacturer's instructions. All the specimens were finished with the polishing disc(3M dental product, St Paul, MN, USA), thermocycled for 500 cycles between 5℃ and 55℃ and resected apical 3-mm root. 0.028 stainless steel wire was inserted apically into the pulp chamber of each tooth and sealed into position with sticky wax. Surrounding tooth surface was covered with a nail varnish 2 times except areas 1 mm far from all the margins. After drying for one day, soaked the samples in the distilled water. Microleakage was assessed by electrochemical method(System 6514, Electrometer®, Keithley, USA) in the distilled water.

In this study, the microleakage was the lowest in group 1(NE) and the highest in group 3(E20s)(NE<E10s<E20s). But no statistically significant differences were found(p=0.5).

On the basis of findings from this experiment, it can be concluded that additional enamel etching has no influence on the microleakage of the adhesion of self-etching primer system.