The purpose of this study was to evaluate the effect of film thickness of various resin cements on bonding efficiency in indirect composite restoration by measurement of microtensile bond strength, polymerization shrinkage, flexural strength and modulus, fractographic FE-SEM analysis. Experimental groups were divided according to film thickness (< 50 µm-control, 50 µm-T50, 100 µm-T100, 150 µm-T150) using composite-based resin cements (Variolink II, Duo-Link) and adhesive-based resin cements (Panavia F, Rely X Unicem). The data was analyzed using ANOVA and Duncan's multiple comparison test (p < 0.05).

The results were as follows;

Variolink II showed higher microtensile bond strength than that of adhesive-based resin cements in all film thickness (p < 0.05) but Duo-Link did not show significant difference except control group (p < 0.05).

The objective of this study is to evaluate the effect of an additional application of bonding resin on the bond strength of resin luting cements in both the light-cure (LC) and self-cure (SC) modes by means of the µTBS tests.

Three combinations of One-Step Plus with Choice, Single Bond with Rely X ARC, and One-Up Bond F with Bistite II were used. D/E resin and Pre-Bond resin were used for the additional application. Twelve experimental groups were made. Three mandibular 3^rd molars were used in each group. Indirect composite blocks were cemented on the tooth surface. 1 × 1 mm² dentin-composite beam for µTBS testing were made and tested.

When total-etching dentin adhesives were used, an additional application of the bonding resin increased the bond strength (P < 0.05). However, this additional application didn't influence the bond strength of self-etching dentin adhesives (P > 0.05).

In conclusion, the results suggest that an additional application of the bonding resin increases bond strength and enhances quality of bonding when using total-etching dentin adhesives.

The purpose of this study was to prove that an intermediate resin layer (IRL) can increase the bond strength to dentin by reducing the permeability of single-step adhesives.

Flat dentin surfaces were created on buccal and lingual side of freshly extracted third molar using a low-speed diamond saw under copious water flow. Approximately 2.0 mm thick axially sectioned dentin slice was abraded with wet #600 SiC paper. Three single-step self-etch adhesives; Adper Prompt L-Pop (3M ESPE, St Paul, MN, USA), One-Up Bond F (Tokuyama Corp, Tokyo, Japan) and Xeno III (Dentsply, Konstanz, Germany) were used in this study. Each adhesive groups were again subdivided into ten groups by; whether IRL was used or not; whether adhesives were cured with light before application of IRL or not; the mode of composite application.

The results of this study were as follows;

1. Bond strength of single-step adhesives increased by an additional coating of intermediate resin layer, and this increasement was statistically signigicant when self-cured composite was used (p < 0.001).

2. When using IRL, there were no difference on bond strengths regardless the curing procedure of single-step adhesives.

3. There were no significant difference on bond strengths between usage of AB2 or SM as an IRL.

4. The thickness of hybrid layer was correlated with the acidity of adhesive used, and the nanoleakage represented by silver deposits and grains was examined within hybrid and adhesive layer in most of single-step adhesives.

5. Neither thickness of hybrid layer nor nanoleakage were related to bond strength.

The purpose of this study was to evaluate the effects of cyanate methacylate on the shear bond strengths to bovine dentin surfaces as a dentin primers.

Seven experimental adhesives were made with different mass fraction of Isocyanatoetylmethacrylate (IEM), 40wt% HEMA (Wako Pure Chemical Industries Osaka, Japan), 0.6% camphoroquinone, 0.4% amine and ethanol as balance. dentin bonding agents (0, 2, 4, 6, 8, 10, 12%) were made and applied on the surface of bovine dentin specimens of 7 experimental groups.

Shear bond strengths were measured using a universal testing machine (Instro 4466).

To identify the ratio and modes of cohesive failures, microscopic examinationn was performed. The ultra-structure of resin tags were observed under scanning electron microscope.

The results were as follows ;

1) A higher shear bond strengths (33.62 _MPa) in group 8% of Cyanate methacrylate to dentin were found, but there were no statistically significancy between Groups (p > 0.05).

2) The higher ratio of cohesive failures mode in group 2, 6, an 10% could be seen than that in any other groups.

3) A shorter resin tags were observed in all experimental groups.

This could be resulted that the preventing from the cyanate methacrylate penetrate into dentin owing to reacting it with dentin collagen.

Therefore the resin tags were shorter in lengths.

Whether the higher bonding strengths of dentin bonding agents can be affected was not been assured with statistic results.

The results indicated that the relation between tensile strengths of the dentin adhesives to bovine dentin and resin tags formed into the dentin could not affected.

The main reason of increasing the shear bond strength to bovine dentin in experimental groups could not be assured.

The fracture toughness test is believed as a clinically relevant method for assessing the fracture resistance of the dentinal restoratives. The objectives of this study were to measure the fracture toughness (K_1C) and microtensile bond strength of dentin-resin composite interface and compare their relationship for their use in evaluation of the integrity of the dentin-resin bond.

A minimum of six short-rod specimens for fracture toughness test and fifteen specimens for microtensile bond strength test was fabricated for each group of materials used. After all specimens storing for 24 hours in distilled water at 37℃, they were tensile-loaded with an EZ tester universal testing machin. Statistical analysis was performed using ANOVA and Tukey's test at the 95% confidence level, Pearson's coefficient was used to verify the correlation between the mean of fracture toughness and microtensile bond strength. FE-SEM was employed on fractured surface to describe the crack propagation.

Fracture toughness value of Clearfil SE Bond (SE) was the highest, followed by Adper Single Bond 2 (SB), OptiBond Solo (OB), ONE-STEP PLUS (OS), ScotchBond Multi-purpose (SM) and there was significant difference between SE and other 4 groups (p < 0.05). There were, however, no significant difference among SB, OB, OS, SM (p > 0.05). Microtensile bond strength of SE was the highest, followed by SB, OB, SM, OS and OS only showed significant lower value (p < 0.05). There was no correlation between fracture toughness and microtensile bond strength values. FE-SEM examination revealed that dentin bonding agent showed different film thickness and different failure pattern according to the film thickness.

From the limited results of this study, it was noted that there was statistically no correlation between K1C and µTBS. We can conclude that for obtaining the reliability of bond strength test of dentin bonding agent, we must pay more attention to the test procedure and its profound scrutiny.

The objectives of this study was to evaluate the effect of thermocycling on the μTBS (microtensile bond strength) to dentin with four different adhesive systems to examine the bonding durability.

Freshly extracted 3^rd molar teeth were exposed occlusal dentin surfaces, and randomly distributed into 8 adhesive groups: 3-steps total-etching (Scotchbond Multi-Purpose Plus; SM, All Bond-2; AB), 2-steps total-etching (Single Bond; SB, One Step plus; OS), 2-steps self-etching (Clearfil SE Bond; SE, AdheSE; AD) and single-step self-etching systems (Promp L-Pop; PL, Xeno III; XE). Each adhesive system in 8 adhesives groups was applied on prepared dentin surface as an instruction and resin composite (Z250) was placed incrementally and light-cured. The bonded specimens were sectioned with low-speed diamond saw to obtain 1 × 1 ㎜ sticks after 24 hours of storage at 37 °C distilled water and proceeded thermocycling at the pre-determined cycles of 0, 1,000 and 2,000. The μTBS test was carried out with EZ-tester at 1 mm/min. The results of bond strength test were statistically analyzed using one-way ANOVA/ Duncan's test at the α〈 0.05 confidence level. Also, the fracture mode of debonded surface and the interface were examined under SEM.

The results of this study were as follows;

3-step total etching adhesives showed stable, but bond strength of 2-step adhesives were decreased as thermocycling stress.

Within limited results of this study, the bond strength of adhesive system was material specific and the bonding durability was affected by the bonding step/ procedure of adhesive. Simplified bonding procedures do not necessarily imply improved bonding performance.

Mechanical removals in decayed teeth have been performed using drill and sharp hand instruments. These methods have some disadvantages such as pain, local anesthesia and overextended cavities. Therefore chemo-mechanical excavation of dentin carious lesions has been introduced. The purpose of this study was to evaluate the efficacy of traditional mechanical methods using burs and chemo-mechanical methods (Carisolv) of caries dentin.

Mechanical caries removal was carried with low speed round bur. Chemo-mechanical caries excavation was performed with Carisolv (Medi-team), using the Carisolv hand instruments. The mean time to remove caries with two different methods was evaluated and the data analyzed with SPSS software (ver 11.5) by t-test (p < 0.05). For histomorphometry of caries removal were also carried with mechanical or chemo-mechanical (Carisolv) methods from 20 extracted caries permanent molars. Complete caries removal was verified with a #23 sharp explorers, Caries Detector (Kuraray Co. Japan), and standard apical radiography.

1. Chemo-mechanical method was taken more times than mechanical method (1.5 fold) (p < 0.05).

2. Excavation for caries took more time for molar lesion than premolar lesion, and the least time was taken to remove the caries in incisor lesion (p < 0.05).

3. There were no significant differences to remove the caries between the maxilla and mandible (p > 0.05).

4. The remaining carious dentin was detected after the chemo-mechanical removal of the carious dentin, and no smear layer were seen after the mechanical and chemo-mechanical removal of the carious dentin.

The purpose of this study is to evaluate the sealing effect of several root-end filling materials using spectrophotometric analysis. 180 single root teeth with one canal were instrumented and canal filled. Root resected and root end preparation was made. Teeth were randomly classified to 5 experimental group(MTA, EBA, IRM, TCP, ZOE) and 1 control group according to root-end filling material MTA group used PRO ROOT MTA, EBA group used Super EBA, TCP group used NEW APATITE LINER TYPE II main component of which is α-tricalcium phosphate(TCP). According to manufacture's instruction experimental material was mixed and retrfilled. After 2% methylene blue solution penetration absorbance for each test sample was measured with spectrophotometer (JASCO UV-530, Japan).

The mean absorbance of control and experimental group was as follows;

MTA : 0.092, IRM : 0.226, Super EBA : 0.255, ZOE : 0.374, Control : 0.425, TCP : 0.501 and the result analyzed by Turkey test at P=0.05 level.

Conclusions of this study are as follows;

The absorbance increase in follwing sequence MTA, IRM, Super EBA, ZOE, Control, TCP.