The purpose of this study was to assess the current materials, methods and difficulties according to the year of licence and educational background of Korean dentists in Class II direct composite resin restorations.

Total 17 questions were included in the questionnaire. Questions were broadly divided into two parts; first, operator's information, and second, the materials and methods used in Class II posterior composite restoration. The questionnaire was sent to dentists enrolled in Korean Dental Association via e-mail. Total 12,193 e-mails were distributed to dentists, 2,612 e-mails were opened, and 840 mails (32.2%) were received from respondents. The data was statically analyzed by chi-square test using SPSS(v. 12.0.1, SPSS Inc, Chicago, IL, USA).

Male dentists among respondents was 79%. 60.3% of the respondents acquired their licences recently (1998-2007), and 77% practiced in private offices. 83.4% have acquired their knowledge through school lectures, conferences and seminars.

For the Class II restorations, gold inlays were preferred by 65.7% of respondents, while direct composite resin restorations were used by 12.1% amalgam users were only 4.4% of respondents.

For the restorative technique, 74.4% of respondents didn't use rubber dam as needed. For the matrix, mylar strip (53.4%), metal matrix (33.8%) and Palodent system (6.5%) were used. 99.6% of respondents restored the Class II cavity by incremental layering.

Obtaining of the tight interproximal contact was considered as the most difficult procedure (57.2%) followed by field isolation (21%).

Among various bonding systems, 22.6% of respondents preferred SE Bond and 20.2% used Single Bond. Z-250 was used most frequently among a variety of composite resins.

The aim of this study was to evaluate the influence of light energy on the tooth whitening effect of bleaching agent in vitro. Extracted human mandibular molars were sectioned to 2 fragments(mesial, distal) and lingual portions of crown were used in this study. All specimens were stained using a red wine for 24 hours and immersed in artificial saliva. Specimens divided into four groups, group 1 and 2 light-activated by LumaCool (LED, LumaLite, Inc., Spring Valley, USA), group 3 and 4 light-activated by FlipoWhite2 (Plasma acr lamp, Lokki, Australia). Group 1 and 3 bleached with LumaWhite(LumaLite, Inc., Spring Valley, USA), group 2 and 4 bleached with Polaoffice(SDI, Victoria, Australia). Bleaching treatment performed during 10 minutes every 24 hours and repeated 6 times. During bleaching treatment , distal fragments was light-activated(L) but mesial fragments was not(NL). Shade assessment employed before and after bleaching treatment using spectrophotometer. The results of the change in shade was compared and analysed between NL and L by using paired-sample T test with 95% level of confidence.

There were no significant differences between NL and L with a few exceptions. In group 2, a^* value more change in L, in group 3, b^* value more change in L, in group 4, a^* value less change in L. After bleaching, L^* value and ΔE increased in all groups and the value of a^* and b^* decreased in all groups.

Within the limitation of this test conditions, the results of this study indicate that the light energy has no obvious improving impact on the tooth whitening effect of a bleaching agent.

The purpose of this study was to compare the effect of curing methods of adhesive resins and resin cements in the root canal. Crown portions of 32 single-rooted mandibular premolars were removed. Routine endodontic treatment was done, and 9 mm deep post spaces were prepared within root canals. No. 3 FRC Postec posts (Ivoclar-Vivadent AG, Liechtenstein) were cemented in the post spaces by self-(SC) or light-curing (LC) using two dual-cured adhesives (Adper Scotchbond multi-purpose plus and Exite DSC )and resin cements (RelyX ARC and Variolink II). They were assigned to 4 groups (n=8); R-SC, R-LC, V-SC, V-LC group.

After stored in distilled water for 24 hours, each root was transversally sectioned with 1.5 mm thick and made three slices. The specimens were subjected to push-out test in a universal testing machine (EZ Test, Shimadzu Co., Japan) with a crosshead speed of 1 mm/min. The data were analyzed with repeated ANOVA and one-way.

ANOVA. Also the interface of post-resin cement and resin cement-canal wall of each group was observed under FE-SEM.

When fiber posts were cemented into the root canal using total-etch adhesives, the bond strength and adaptation between post and root canal dentin was affected by curing method. Self-cure of adhesives and resin cements showed higher bond strength and closer adaptation than light-cure of them.

The purpose of this study was to compare the tensile bond strength of several self-adhesive resin cements bonded to dentin surfaces with different wet conditions.

Three self-adhesive resin cements; Rely-X Unicem (3M ESPE, St. Paul, MN, USA), Embrace Wetbond (Pulpdent, Oakland, MA, USA), Maxcem (Kerr, Orange, CA, USA) were used. Extracted sixty human molars were used. Each self-adhesive resin cement was adhered to the dentin specimens (two rectangular sticks from each molar) in different wet conditions.

Tensile bond strength were measured using universal testing machine (EZ Test, Shimadzu corporation, Kyoto, Japan) at a crosshead speed of 1.0mm/min. After the testing, bonding failures of specimens were observed by Operative microscope (OPMI pro, Carl Zeiss, Oberkochen, Germany). T-test was used to evaluate the effect of dentin surface wetness. One-way ANOVA test was used to evaluate the tensile bond strength of self-adhesive resin cements in the same condition. Scheffe's test was used for statistical analyzing at the 95% level of confidence.

The result showed that wetness of dentin surface didn't affect tensile bond strength of self-adhesive resin cements and Maxcem showed the lowest tensile bond strength.

The purpose of this study was to investigate the pulpal response to direct pulp capping with dentin sialo-protein (DSP) -derived synthetic peptide in teeth of dogs, and to compare its efficacy to capping substances Ca(OH)₂ and white mineral trioxide aggregate (WMTA). A total of 72 teeth of 6 healthy male beagle dogs were used. The mechanically exposed pulps were capped with one of the following: (1) DSP-derived synthetic peptide (PEP group); (2) Ca(OH)₂ (CH group); (3) a mixture paste of peptide and Ca(OH)₂ (PEP+CH group); or (4) white MTA (WMTA group). The access cavity was restored with a reinforced glass ionomer cement. Two dogs were sacrificed at each pre-determined intervals (2 weeks, 1 month, and 3 months). After the specimens were prepared for standard histological processing, sections were stained with hematoxylin and eosin. Under a light microscope, inflammatory response and hard tissue formation were evaluated in a blind manner by 2 observers. In the PEP group, only 3 of 17 specimens showed hard tissue formation, indication that the DSP-derived synthetic peptide did not induce proper healing of the pulp. Compared with the CH group, the PEP group demonstrated an increased inflammatory response and poor hard tissue formation. The CH and WMTA groups showed similar results for direct pulp capping in mechanically exposed teeth of dogs.

The aim of this study was to develop a method for measuring the slumping resistance of flowable resin composites and to evaluate the efficacy using rheological methodology.

Five commercial flowable composites (Aelitefil flow:AF, Filtek flow:FF, DenFil flow:DF, Tetric flow:TF and Revolution:RV) were used. Same volume of composites in a syringe was extruded on a glass slide using a custom-made loading device. The resin composites were allowed to slump for 10 seconds at 25℃ and light cured. The aspect ratio (height/diameter) of cone or dome shaped specimen was measured for estimating the slumping tendency of composites. The complex viscosity of each composite was measured by a dynamic oscillatory shear test as a function of angular frequency using a rheometer. To compare the slumping tendency of composites, one way-ANOVA and Turkey's post hoc test was performed for the aspect ratio at 95% confidence level. Regression analysis was performed to investigate the relationship between the complex viscosity and the aspect ratio. The results were as follows.

1. Slumping tendency based on the aspect ratio varied among the five materials (AF < FF < DF < TF < RV).

2. Flowable composites exhibited pseudoplasticity in which the complex viscosity decreased with increasing frequency (shear rate). AF was the most significant, RV the least.

3. The slumping tendency was strongly related with the complex viscosity. Slumping resistance increased with increasing the complex viscosity.

The slumping tendency could be quantified by measuring the aspect ratio of slumped flowable composites. This method may be applicable to evaluate the clinical handling characteristics of flowable composites.

The aim of this study was to investigate the shapes and diameters of the physiological foramen and anatomy of the root canal at 3mm from apex in mandibular first molars.

Sixty mandibular first molars were randomly selected. The apical anatomy of 60 mandibular first molars was investigated by means of a stereomicroscope (60x magnification).

The results were as follows;

1. There was a high percentage of two physiological foramina in mesial (61.67%) and one foramen in distal(71.66%) roots of mandibular first molars.

2.There was a high frequency of accessory foramina in mesial roots with one foramen (26.07%).

3. The diameters of physiological foramen was as follows:

0.329mm in single mesial foramen

4. The most common physiological foramen shape was oval (69.93%).

5. The incidence of isthmus in mesial root at 3mm from apex was 55%. The 3mm-sections contained a complete isthmus 31.66% and a partial isthmus 23.34%.

6. 3mm from the apex, the most common canal shape was oval (50.64%).

Knowledge of the apical anatomy of mandibular first molar would be necessary for success of surgical and nonsurgical endodontic treatment.

The purpose of this study was to evaluate the effect of instrument compliance on the polymerization shrinkage stress measurements of dental composites. The contraction strain and stress of composites during light curing were measured by a custom made stress-strain analyzer, which consisted of a displacement sensor, a cantilever load cell and a negative feedback mechanism. The instrument can measure the polymerization stress by two modes: with compliance mode in which the instrument compliance is allowed, or without compliance mode in which the instrument compliance is not allowed.

A flowable (Filtek Flow: FF) and two universal hybrid (Z100: Z1 and Z250: Z2) composites were studied. A silane treated metal rod with a diameter of 3.0 mm was fixed at free end of the load cell, and other metal rod was fixed on the base plate. Composite of 1.0 mm thickness was placed between the two rods and light cured. The axial shrinkage strain and stress of the composite were recorded for 10 minutes during polymerization, and the tensile modulus of the materials was also determined with the instrument. The statistical analysis was conducted by ANOVA, paired t-test and Tukey's test (α<0.05).

There were significant differences between the two measurement modes and among materials. With compliance mode, the contraction stress of FF was the highest: 3.11 (0.13), followed by Z1: 2.91 (0.10) and Z2: 1.94 (0.09) MPa. When the instrument compliance is not allowed, the contraction stress of Z1 was the highest: 17.08 (0.89), followed by FF: 10.11 (0.29) and Z2: 9.46 (1.63) MPa. The tensile modulus for Z1, Z2 and FF was 2.31 (0.18), 2.05 (0.20), 1.41 (0.11) GPa, respectively. With compliance mode, the measured stress correlated with the axial shrinkage strain of composite; while without compliance the elastic modulus of materials played a significant role in the stress measurement.

This clinical study evaluated the whitening effect and safety of polymer based-pen type BlancTis Forte (NIBEC) containing 8.3% carbamide peroxide. Twenty volunteers used the BlancTis Forte whitening agent for 2 hours twice a day for 4 weeks. As a control, Whitening Effect Pen (LG) containing 3% hydrogen peroxide was used by 20 volunteers using the same protocol. The change in shade (ΔE^*, color difference) was measured using Shadepilot™ (DeguDent) before, during, and after bleaching (2 weeks, 4 weeks, and post-bleaching 4 weeks). A clinical examination for any side effects (tooth hypersensitivity or soft tissue complications) was also performed at each check-up. The following results were obtained.

1. Both the experimental and control groups displayed a noticeable change in shade (ΔE) of over 2. No significant differences were found between the two groups (p > 0.05), implying that the two agents have a similar whitening effect.

2. The whitening effect was mainly due to changes in a and b values rather than in L value (brightness). The experimental group showed a significantly higher change in b value, thus yellow shade, than the control (p < 0.05).

3. None of the participants complained of tooth hypersensitivity or soft tissue complications, confirming the safety of both whitening agents.