Immune responses associated with bacterial infection involve various inflammatory cells. Clinical symptoms and pathologic features are particularly influenced by the predominant cells. Among inflammatory cells, T cells have the heterogenity. T cells may develop into the mature cells expressing the cell surface markers with different functions and T helper cells are categorized into Th1 and Th2 cells based on their different patterns of cytokine production. The objective of this study was to investigate the change of expression of surface markers on T cells and the Th1/Th2 immune response in pulpal inflammation associated with specific bacteria.

We experimentally induced pulpal inflammation in rat incisors by drilling without coolant and innoculated with Streptococcus mutans (S.M. group), Porphyromonas endodontalis (P.E. group), or only sterile cotton (control group). After 1, 2, and 5 days, mandibular incisors were extracted and the pulp tissues were extirpated. The expressions of IL-2 recepters (CD25) and ICAM-1 (CD54) on CD4+ and CD8+ cells in the pulps were determined using a flow cytometer, and the concentration of IL-2, IFN-γ and IL-4 was measured by enzyme-linked immunosorbent assay.

The results were as follows;

1. In the S.M. group, CD4+ cells were more increased at 2nd day than 1st day and in the P.E. group, CD8+ cells were more increased at 2nd day than 1st day.

2. The percentages of CD4+, CD4+25+ and CD4+54+ cells were decreased in the pulp tissues at 5th day after irritation in all groups.

3. The ratios of CD4+/CD8+, CD4+/CD4+25+ and CD4+/CD4+54+ in the pulps at 2nd day after irritation by P. endodontalis were significantly lower than the other groups.

4. The higher concentrations of IFN-γ than IL-4 in the pulps at 2nd day after irritation by P. endodontalis showed that T helper 1 reaction were predominant in the early stage of the pulpal inflammation induced by P. endodontalis.

5. The higher concentrations of IL-4 than IFN-γ in the pulps at 1st day and 5th day after irritation by S. mutans were measured but the differences were not significant.

The first purpose of present study was to compare the anticariogenic effect of compomer, resin modified glass ionomer cement and composite (RMGIC).

The second purpose was to evaluate the recently introduced methods, which use confocal scanning microscope, in detecting initial caries around restoration.

2×4×1.5mm cavities were prepared from the recently extracted 50 human teeth on the buccal or lingual surface. The prepared teeth were randomly devided into 5 groups and restored with each filling material. Group 1: Dyract AP, Group 2: compoglass F, Group 3: F2000, Group 4: Z100, Group 5:Fuji Ⅱ LC. The teeth were stored for 30 days in the distilled water, then stored in the buffer solution for artificial caries development; pH 4.3, lactic acid 100 mM, calcium 16 mM, phosphate 8mM, sodium azide 3mM. Then, the samples were sectioned longitudinally and examined with confical scanning microscope. The results showed that the use of compomer and resin modified glass ionomer cement showed caries inhibition zone whereas the composite did not. There was no difference in the width of caries inhibition zone between compomers and RMGIC. The confocal scanning microscope was useful in detecting initial caries around restoration.

Physical properties of composite resins such as strength, resistance to wear, discoloration, etc depend on the degree of conversion of the resin components. The purpose of this study was to evaluate the degree of conversion of the composite resins according to the thickness of tooth structure penetrated by light and applied light curing time. The coronal portions of extracted human teeth (one anterior tooth, three posterior tooth) was embedded by pink denture material. the mounted teeth were cut into three illumination sections (1mm thickness enamel section, 1mm thickness dentin section, 2mm thicknes dentin section) and one backing section with cutting wheel. Thin resin films were made by using 6kg pressure between slide glass during 5 minutes.

Thin resin film was light cured on coupled illumination section during 40sec, 80sec and 120sec. each illumination section was coupled as follows; no tooth structure(X), ename section(E), enamel section + 1mm dentin section(ED1), enamel section + 2mm dentin section(ED2), enamel section + 1mm dentin section + 2mm dentin section(EDD). To simulate the clinical situation more closely, thin resin film was cured against a backing section of tooth structure. The degree of conversion of carbon double bonds to single bonds in the resin films were examined by means of Fourier Transform Infrared Spectrometer. The results were obtained as follows;

1. As curing time was increased, conversion rate was increased and as tooth thickness which was penetrated by curing light was increased, conversion rate was decreased.

2. At all tooth thickness groups, conversion rate between 80sec and 120sec was not significantly increased(P>0.05).

3. At 40sec group and 80sec, conversion rate between no tooth structure(X) group and 1mm enamel section(E) group was not significantly decreased(P>0.05).

4. At 80sec group and 120sec, conversion rate between 1mm enamel section(E) group and 1mm enamel section + 1mm dentin section(ED1) group was not significantly decreased(P>0.05).

Leakage studies have been performed frequently, since a fluid-tight seal provided by various dental filling materials has been considered clinically important. The leakage of the various root-end filling materials has been widely investigated mostly dye penetration method. These dye studies cannot offer any information about the quality of the seal of a test material over a long period of time The purpose of this study was to evaluate the microleakage of root end cavities in blood contamination filled amalgam, intermediate restorative material(IRM), light cured glass ionomer cement(GI) and mineral trioxide aggregate(MTA) by means of a modified fluid transport model. Fifty standard human root sections, each 5mm high and with a central pulp lumen of 3mm in diameter, were and filled with our commonly used or potential root end filling materials after they were contaminated with blood. At 24h, 72h, 1, 2, 4, 8, and 12 weeks after filling, leakage along these filling materials was determined under a low pressure of 10KPa(0.1atm) using a fluid transport model.

The results were as follows:

1. MTA group showed a tendency of decreasing percent of gross leakage (20ml/day) in process of time, whereas the other materials showed a tendency of increasing in the process time.

2. At the all time interval, GI group leaked significantly less than amalgam group and IRM group (p<0.05).

3. At the 4 weeks, the percentage of gross leakage in MTA group decreased to 0% thereafter, the low percentage of gross leakage was maintained in MTA group until the end of the experiment, whereas the percentage in IRM group increased to 100%.

4. At the 12 weeks, percentage of gross leakage was significantly low in MTA group(0%), comparison with GI group(40%), amalgam group(90%) and IRM group(100%), but there was no significant difference between latter two materials.

The purpose of this study was to compare microleakage and marginal hybrid layer in class Ⅴ restorations using two one-bottle adhesives and one self-etching adhesive.

Class Ⅴ cavity preparations with occlusal margins in enamel and gingival margins in dentin were prepared on buccal and lingual surfaces of 30 extracted human molar teeth. Prepared teeth were randomly divided into three treatment groups (n=30) and restored with three adhesives and composites: Single Bond/Filtek Z-250 (Group 1), Prime&BondNT/Esthet∙X (Group 2), UniFil Bond/UniFil F (Group 3).

For microleakage, samples were stored in room temperature water for 24 hours, thermocycled, stained with 2% methylene blue dye, sectioned into halves, scored and analysed using Mann-whitney test and Wilcoxon signed rank sum test.

For marginal hybrid layer, samples were sectioned into halves, treated with 10% phosphoric acid for 5 seconds, stored in 5% NaOCL solution for 24 hours, dried and gold coated. Occlusal and gingival margins of each sample were inspected under SEM.

The results of this study were as follows;

Microleakage at the occlusal margins was not evident in group 1 and group 2, but it showed in group 3 (p<0.05).

In coclusion, the effect of dentin adhesives on microleakge in class Ⅴ composite restorations was excellent when one-bottle adhesives were applied on enamel margin, and it was good when a self-etching adhesive was applied on dentinal margin. There was no corelation between microleakage and thickness of marginal hybrid layer.

Black-pigmented bacteria have been implicated in the endodontic infections. This group of microorganisms includes Porphyromonas endodontalis, Porphyromonas gingivalis, Prevotella intermedia, and Prevotella nigrescens. The organisms display a wide variety of virulence factors that may be pertinent to acute endodontic infections.

The aim of this study was to identify P. endodontalis, P. gingivalis, P. intermedia, and P. nigrescens by using special potency disk test, filter paper spot test, 16S rRNA gene-directed PCR, and API 32A.

Microbial samples were collected from root canals of 33 intact teeth with necrotic pulp and/or apical periodontitis. Conventional laboratory methods were used for identification of the strains of black pigmented bacteria. Eighteen of 33 samples were positive for the growth of black-pigmented bacrteria. Five colonies were cultured from each pure cultured colonies from Brucella agar plate. Seventy seven colonies were positive for the growth of black-pigmented bacteria.

Thirty three of 77(42.6%) were identifed as P. nigrescens, 10 of 77(12.9%) were P. gingivalis, 6 of 77(7.8%) were P. endodontalis, 10 of 77(12.9%) were P. intermedia. On the contrary the reference strains of P. nigrescens, experimental strains of P. nigrescens was sensitive to kanamycin in special potency disk test.

16S rRNA gene PCR and API test after rapid presumptative identification methods, such as special potency disk test and filter paper spot test, would be accurate detection methods for black-pigemented bacteria.

The purpose of this study is to evaluate the effectiveness of customized master cone on apical sealing in various apical size of prepared root canals, that is MAF(Master Apical File) and to know at which apical size the apical leakage is to be significantly reduced using customized master cone.

120 extracted single rooted premolars were divided into four groups according to their apical size(MAF), #30, 40, 50 and 60. And then, each group was subdivided into three in accordance with three obturation methods, lateral condensation with standardized master cone, lateral condensation with chloroform-dipped customized master cone, and continuous wave of obturation technique.

Resorcinol-formaldehyde resin was used for the microleakage test of this study. Teeth were sectioned horizontally at 1.5mm(Level 1), 2.5mm(Level 2), and 3.5mm(Level 3) from the anatomical root apex using low speed microtome. All sections were examined under ×40 magnification with a stereomicroscope, photographed, and then scanned. With the scanned images, resin-infiltrated area presenting the microleakage was calculated using SigmaScan/Image, and the ratio of leakage to the total root canal area of each group was analyzed statistically(one way ANOVA).

The results were as follows;

1. In groups of MAF #30, there was no significant difference of mean leakage ratio among three obturation methods at all three levels.

2. In groups of MAF #40, the group using lateral condensation with customized master cone had the lowest mean leakage ratio at all three levels, but there was no significant difference among three obturation techniques.

3. In groups of MAF #50, the mean leakage ratio of the group using lateral condensation with standard master cone was the highest among those of three obturation techniques at level 1, and this difference was statistically significant(p<0.05).

4. In groups of MAF #60, the groups using lateral condensation with standard master cone had also the highest mean leakage ratio at all levels, but there was no significant difference at level 1 and 2. At level 3, the leakage of the group using lateral condensation with standard master cone was significantly higher than that of the group using continuous wave of obturation(p<0.05).

The results of this study suggested that the obturation method using customized master cone or the continuous wave of obturation is more effective for apical sealing than that using standardized master cone when MAF is larger than #50.

Current composites are made with dimethacrylate monomers and silane-treated silica microfillers, either alone or with silane treated glass fillers. The main reasons for clinical failure of dental composites are secondary caries, wear and fracture. Most of practitioner want to get a composite which is more tougher under occlusal stress, less polymerization contraction, and better handling properties in application clinically. The aim of this study was to investigate the influence of resin matrix with various flows on the physical properties such as fracture toughness and degree of conversion of the experimental resins. It was hypothesized that flexible or tough resin composites can be designed by judicious choice of monomer composition.

Various flow resin matrices containing Bis-GMA, UDMA, and TEG-DMA were made by altering the proportion of the monomers. After the unfilled resins were light-cured for different light intensity, the fracture toughness(K_1c) was measured according to ASTM standard using the single edge notched geometry, and degree of conversion(DC) was measured by FTIR. And experimental composites were formulated with variations in the proportion of silanated quartz and strontium glass fillers as 60, 75, and 77wt%. Also, the physical properties of composites with various filler contents were evaluated as same manner. All resulting data were compared by ANOVA/Tukeys test at 0.05 level.

The results were as follows;

1. The degree of conversion of high flow resin containing less Bis-GMA was higher than that of low flow unfilled resin.

2. While the degree of conversion of unfilled resin was increased according to light intensity for polymerization, there was no significant increase with moderate and high light intensity. Also, the fracture toughness was not increased by high light intensity.

3. The fracture toughness was high in the low flow unfilled resin containing higher contents of Bis-GMA.

4. There was a significant increase for fracture toughness and a tendency for degree of conversion to be reduced when the content of fillers was increased.

5. In the experimental composites, the flow of resin matrix did not affected on the fracture toughness, even, which was decreased as increase of viscosity.

These results showed that the physical properties of a dental composite could be attributed to the flow of resin matrix with relative content of monomers. Specific combination of resin monomers should be designed to fulfil the needs of specific indication for use.

The purpose of this study was to evaluate the color changes of composite resin polymerized with three type of light curing units. Composite resin (Z100, shade A2) were applied in a cylindrical metal mold(2 mm thick, 7 mm diameter).

Twenty specimens according to light curing units were made.

Group1: the specimens were polymerized with Apollo 95E for 3seconds(1370 mW/cm²).

Group2: the specimens were polymerized with XL 3000 for 40seconds(480 mW/cm²).

Group3: the specimens were polymerized with Spectrum 800 for 10 seconds(250 mW/cm²) and 30 seconds(700 mW/cm²).

The microhardness values(VHN) of upper and lower surfaces specimens after light polymerization were measured for the degree of polymerization. All specimens were stored in distilled water at 60℃ for 30 days.

The color characteristics(L^*, a^*, b^*) of the specimens before and after immersion were measured by spectrophotometer and the total color difference (ΔE^*) was computed.

The results obtained were as follows:

1. The microhardness values of Group I showed significantly lower than those of Group II and III(p<0.05).

2. In all groups the ΔE^* values presented below 2.0.

3. Group I showed the highest ΔE^* values followed order from highest to lowest by Group II and III (p<0.05).