Hemolytic property is a specific feature of bacteria to obtain iron which is essential for its survival in host tissues. Therefore, it is thought to be one of several factors of virulence. The purpose of this study was to investigate the hemolytic properties of Prevotella nigrescens isolated from the teeth diagnosed as pulp necrosis and apical periodontitis under the presence of hemolysin inhibitors such as NaN₃ and dithiothreitol, heat, various pH and cultural conditions.

The results were as follows;

1. Clinically isolated P. nigrescens strains and standard P. nigrscens ATCC 33563 showed hemolytic activity.

2. P. nigrescens showed higher hemolytic activity against human erythrocytes than sheep or horse erythrocytes.

3. NaN₃ and dithiothreitol (DTT) reduced the hemolytic activity of P. nigrescens in a dose dependent manner (p < 0.05).

4. Optimal pH for the maximum hemolytic activity of P. nigrescens was 4.0 and the hemolysin was stable under the 50℃, but the hemolytic activity was significantly decreased at 95℃.

5. P. nigrescens cultured in 10% CO₂ condition showed higher hemolytic activity than the bacteria cultured in the anaerobic condition.

The purpose of this study was to compare the microhardness and the fluoride content of enamel and dentin around fluoride- or non fluoride-containing restorations. Forty extracted human teeth were used and prepared cervical cavities on proximal surface. Experimental teeth were divided into five groups. Group 1 : Prime & Bond NT and Z100, Group 2 : Prime & Bond NT and F2000, Group 3 : Scotchbond Multi-Purpose and Z100, Group 4 : Scothcbond Multi-purpose and F2000, Group 5 : Fuji II LC. The cavities were filled with dentin adhesives and restorative materials. After each tooth was bisected, one half was tested microhardness and the other half was analyzed the fluoride at the enamel and dentin by an EPMA-WDX device. The results were as follows:

1. There was no statistical difference among the microhardness of enamel surface in all group.

2. The microhardness at dentin of 100 µm point in Group 2 and 20 µm point in Group 4 was lower than that of normal dentin (p>0.05).

3. There was no statistical difference among the fluoride content of enamel surface in all group.

4. The fluoride content at the dentin of 30 µm point in Group 2 and 5 were higher than those at 100 µm and 200 µm point in Group 2 and normal dentin (p<0.05).

5. At the dentin of 30 µm point, Group 2 showed higher fluoride content than Group 1 and 3, and Group 5 showed higher fluoride content than other groups.

One of the latest concepts in bonding are "total etch", in which both enamel and dentin are etched with an acid to remove the smear layers, and "wet dentin" in which the dentin is not dry but left moist before application of the bonding primer. Ideally, the application of a bonding agent to tooth structure should be insensitive to minor contamination from oral fluids. Clinically, contaminations such as saliva, gingival fluid, blood and handpiece lubricant are often encountered by dentists during cavity preparation.

The aim of this study was to evaluate the effect of contamination by hemostatic agents on shear bond strength of compomer restorations. One hundred and ten extracted human maxillary and mandibular molar teeth were collected. The teeth were removed soft tissue remnant and debris and stored in physiologic solution until they were used. Small flat area on dentin of the buccal surface were wet ground serially with 400, 800 and 1200 abrasive papers on automatic polishing machine. The teeth were randomly divided into 11 groups. Each group was conditioned as follows:

Group 1: Dentin surface was not etched and not contaminated by hemostatic agents.

Group 2: Dentin surface was not etched but was contaminated by Astringedent®(Ultradent product Inc., Utah, U.S.A.).

Group 3: Dentin surface was not etched but was contaminated by Bosmin®(Jeil Pharm, Korea.).

Group 4: Dentin surface was not etched but was contaminated by Epri-dent®(Epr Industries, NJ, U.S.A.).

Group 5: Dentin surface was etched and not contaminated by hemostatic agents.

Group 6: Dentin surface was etched and contaminated by Astringedent®.

Group 7: Dentin surface was etched and contaminated by Bosmin®.

Group 8: Dentin surface was etched and contaminated by Epri-dent®.

Group 9: Dentin surface was contaminated by Astringedent®. The contaminated surface was rinsed by water and dried by compressed air.

Group 10: Dentin surface was contaminated by Bosmin®. The contaminated surface was rinsed by water and dried by compressed air.

Group 11: Dentin surface was contaminated by Epri-dent®. The contaminated surface was rinsed by water and dried by compressed air.

After surface conditioning, F2000® was applicated on the conditoned dentin surface. The teeth were thermocycled in distilled water at 5℃ and 55℃ for 1,000 cycles. The samples were placed on the binder with the bonded compomer-dentin interface parallel to the knife-edge shearing rod of the Universal Testing Machine(Zwick Z020, Zwick Co., Germany) running at a cross head speed of 1.0 mm/min.

Group 2 showed significant decrease in shear bond strength compared with group 1 and group 6 showed significant decrease in shear bond strength compared with group 5.

There were no significant differences in shear bond strength between group 5 and group 9, 10 and 11.

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.