The purpose of this study was to evaluate the effect of the polymerization shrinkage and modulus of elasticity of composites on the cusp deflection of class V restoration in premolars. The sixteen extracted upper premolars were divided into 2 groups with similar size. The amounts of cuspal deflection were measured in Class V cavities restored with a flowable composite (Filtek flow) or a universal hybrid composite (Z-250). The bonded interfaces of the sectioned specimens were observed using a scanning electron microscopy (SEM). The polymerization shrinkage and modulus of elasticity of the composites were measured to find out the effect of physical properties of composite resins on the cuspal deflection. The results were as follows.

The amounts of cuspal deflection restored with Filtek flow or Z-250 were 2.18 ± 0.92 µm and 2.95 ± 1.13 µm, respectively. Filtek flow showed less cuspal deflection but there was no statistically significant difference (p > 0.05).

The purpose of this study was to evaluate the effect of passive or active application of primer and coat times of bond on the shear bond strength when a self-etching primer adhesive (Clearfil SE Bond) was applied to enamel surface.

Crowns of sixteen human molars were selected. Buccal and lingual enamels of crowns were partially exposed and slabs of 1.2 mm thick were made. They were divided into one of four equal groups (n = 8). Group 1: passive application of Primer and 1 coat of Bond, Group 2: active application of Primer and 1 coat of Bond, Group 3: passive application of Primer and 2 coats of Bond, Group 4: active application of Primer and 2 coats of Bond. Clearfil AP-X was bonded to enamel suface of each group using Tygon tubes. The bonded specimens were subjected to microshear bond strength (uSBS) testing with a crosshead speed of 1 mm/min.

The results of this study were as follows;

The uSBS of Group 1 was the lowest among groups and the uSBS of Group 4 was the highest.

The purpose of this study was to evaluate whether intracanal irrigation method could affect the adhesion between intracanal dentin and root canal filling materials (Gutta-percha/AH 26 sealer and Resilon/Epiphany sealer).

Thirty extracted human incisor teeth were prepared. Canals were irrigated with three different irrigation methods as a final rinse and obturated with two different canal filling materials (G groups : Gutta-percha/AH 26 sealer, R groups : Resilon/Epiphany sealer) respectively.

Group G1, R1 - irrigated with 5.25% NaOCl

Thirty obturated roots were horizontally sliced and push-out bond strength test was performed in the universal testing machine. After test, the failure patterns of the specimens were observed using Image-analyzing microscope.

The results were as follows.

Gutta-percha/AH 26 sealer groups had significantly higher push-out bond strength compared with the Resilon/Epiphany sealer groups (p < 0.05).

This study was performed to assess the radiopacity of a variety of canal filling and retrograde root-end filling materials according to the specification concerning root canal obturation materials.

Ten materials including Gutta-percha pellets, amalgam, Fuji II LC, Dyract® AP, Super EBA®, IRM®, AH 26®, Sealapex™, Tubli-Seal™ and dentin were evaluated in this study. In the first part, densitometric reading of an each step of aluminum step wedge on occlusal film were performed at 60 kVp (0.2, 0.3, 0.4 s), 70 kVp (0.2, 0.3, 0.33 s) to decide appropriate voltage and exposure time. In the second part, ten specimens which are 5 mm in diameter and 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 mm in thickness, were fabricated from each material studied. The specimens were radiographed simultaneously with an aluminum step wedge under decided condition (60 kVp, 0.2 s). The mean radiographic density values of the materials were transformed into radiopacity expressed equivalent thickness of aluminum (mm Al).

The following results were obtained.

Among the various conditions including 0.2 s, 0.3 s, 0.4 s at 60 kVp and 0.2 s, 0.3 s, 0.33 s at 70 kVp, the appropriate voltage and exposure time that meet the requirement of density from 0.5 to 2.0 was 0.2 s at 60 kVp.

It suggests that all experimental canal filling and retrograde root-end filling materials have a sufficient radiopacity that meet the requirement concerning root canal obturation materials except for Fuji II LC and Dyract.

The purpose of this study was to measure the polymerization shrinkage and hygroscopic expansion of resin-based temporary filling materials and to evaluate microleakage at the interface between the materials and cavity wall.

Five resin-based temporary filing materials were investigated: Fermit (Vivadent), Quicks (Dentkist), Provifil (Promedica), Spacer (Vericom), Clip (Voco). Caviton (GC) was also included for comparison. Polymerization shrinkage of five resin-based temporary filling materials was measured using the bonded disc method. For the measurement of hygroscopic expansion, the discs of six cured temporary filling materials were immersed in saline and a LVDT displacement sensor was used to measure the expansion for 7 days. For estimating of microleakage, Class I cavities were prepared on 120 extracted human molars and randomly assigned to 6 groups of 20 each. The cavities in each group were filled with six temporary filling materials. All specimens were submitted to 1000 thermo-cycles, with temperature varying from 5℃/55℃. Microleakage was determined using a dye penetration test.

The results were as follows:

Fermit had significantly less polymerization shrinkage than the other resin-based temporary filling materials. Fermit (0.22 %) < Spacer (0.38 %) < Quicks (0.64 %), Provifil (0.67 %), Clip (0.67 %)

The purpose of this study is to compare the shear bond strength of repaired composite resin with different bonding agents and evaluate the effect of bonding agents on composite repair strength. Forty composite specimens (Z-250) were prepared and aged for 1week by thermocycling between 5 and 55℃ with a dwell time of 30s. After air abrasion with 50 µm aluminum oxide, following different bonding agents were applied (n = 10); SB group: Scotchbond multipurpose adhesive (3 step Total-Etch system); SE group: Clearfil SE bond (2 step Self-Etch system); XP group: XP bond (2 step Total-Etch system); XE group: XenoIII (1 step Self-Etch system). After bonding procedure was completed, new composite resin (Z-250) was applied to the mold and cured. For control group, 10 specimens were prepared. Seven days after repair, shear bond strength was measured. Data was statistically analyzed using one-way ANOVA and Tukey's test (p < 0.05). The means and standard deviations of shear bond strength (MPa ± S.D.) per group were as follows: SB group: 17.06; SE group: 19.10; XP group: 14.44; XE group: 13.57; Control Group: 19.40. No significant difference found in each group. Within the limit of this study, it was concluded that the different type of bonding system was not affect on the shear bond strength of repaired composite resin.

The purpose of this study was to compare the apical microleakage in root canal filled with Resilon by several self-etching primers and methacrylate-based root canal sealer. Seventy single-rooted human teeth were used in this study. The canals were instrumented by a crown-down manner with Gate-Glidden drills and .04 Taper Profile to ISO #40. The teeth were randomly divided into four experimental groups of 15 teeth each according to root canal filling material and self-etching primers and two control groups (positive and negative) of 5 teeth each as follows: group 1 - gutta percha and AH26® sealer; group 2 - Resilon, RealSeal™ primer and RealSeal™ sealer; group 3 - Resilon, Clearfil SE Bond® primer and RealSeal™ sealer group 4 - Resilon, AdheSe® primer and RealSeal™ sealer. Apical leakage was measured by a maximum length of linear dye penetration of roots sectioned longitudinally by diamond disk. Statistical analysis was performed using the One-way ANOVA followed by Scheffe's test. There were no statistical differences in the mean apical dye penetration among the groups 2, 3 and 4 of self-etching primers. And group 1, 2 and 3 had also no statistical difference in apical dye penetration. But, there was statistical difference between group 1 and 4 (p < 0.05). The group 1 showed the least dye penetration. According to the results of this study, Resilon with self-etching primer was not sealed root canal better than gutta precha with AH26® at sealing root canals. And there was no significant difference in apical leakage among the three self-etching primers.

This study was aimed to develop an instrument for real-time measurement of fluid conductance and to investigate the hydrodynamics of dentinal fluid. The instrument consisted of three parts; (1) a glass capillary and a photo sensor for detection of fluid movement, (2) a servo-motor, a lead screw and a ball nut for tracking of fluid movement, (3) a rotary encoder and software for data processing.

To observe the blocking effect of dentinal fluid movement, oxalate gel and self-etch adhesive agent were used. BisBlock (Bisco) and Clearfil SE Bond (Kuraray) were applied to the occlusal dentin surface of extracted human teeth. Using this new device, the fluid movement was measured and compared between before and after each agent was applied.

The instrument was able to measure dentinal fluid movement with a high resolution (0.196 nL) and the flow occurred with a rate of 0.84 to 15.2 nL/s before treatment. After BisBlock or Clearfil SE Bond was used, the fluid movement was decreased by 39.8 to 89.6%.

The purpose of this study was to evaluate the effect of chlorhexidine (CHX) on microtensile bond strength (µTBS) of dentin bonding systems.

Dentin collagenolytic and gelatinolytic activities can be suppressed by protease inhibitors, indicating that MMPs (Matrix metalloproteinases) inhibition could be beneficial in the preservation of hybrid layers. Chlorhexidine (CHX) is known as an inhibitor of MMPs activity in vitro.

The experiment was proceeded as follows:

At first, flat occlusal surfaces were prepared on mid-coronal dentin of extracted third molars. GI (Glass Ionomer) group was treated with dentin conditioner, and then, applied with 2% CHX. Both SM (Scotchbond Multipurpose) and SB (Single Bond) group were applied with CHX after acid-etched with 37% phosphoric acid. TS (Clearfil Tri-S) group was applied with CHX, and then, with adhesives. Hybrid composite Z-250 and resin-modified glass ionomer Fuji-II LC was built up on experimental dentin surfaces. Half of them were subjected to 10,000 thermocycle, while the others were tested immediately. With the resulting data, statistically two-way ANOVA was performed to assess the µTBS before and after thermocycling and the effect of CHX. All statistical tests were carried out at the 95% level of confidence. The failure mode of the testing samples was observed under a scanning electron microscopy (SEM).

Within limited results, the results of this study were as follows;

In all experimental groups applied with 2% chlorhexidine, the microtensile bond strength increased, and thermocycling decreased the microtensile bond strength (P > 0.05).

2% chlorhexidine application after acid-etching proved to preserve the durability of the hybrid layer and microtensile bond strength of dentin bonding systems.