Histological Study of Reparative Dentin Formation after Direct Pulp Capping and Pulpotomy using MTA / 대한해부학회지

The ultimate goal of a regenerative pulp treatment strategy is to reconstitute normal tissue continuum at the pulp-dentin border, regulating tissue-specific processes of reparative dentinogenesis. However, little is known about the molecular mechanism of reparative dentinogenesis. The purpose of this study was to investigate the pulpal response after direct pulp capping and pulpotomy with mineral trioxide aggregate (MTA) by histological and immunohistochemical studies. There was continuous reparative dentin bridge formation at 2 weeks after treatment with MTA in both the pulp capping and the pulpotomy groups. The cells in the pulp capping group showed typical odontoblast characteristics, while the cells of reparative dentin in pulpotomy group were round in shape, lost their polarity, organized as a sheet of cells, and trapped in osteodentin-like mineralized tissue. In pulp capping group, upper layer of the reparative dentin showed cell lacunae indicating osteoblastic characteristics, whereas lower layer of the reparative dentin contained predentin and dentinal tubule-like structures as normal dentin. However, there was osteodentin formation in pulpotomy group. DSP protein was expressed at 4 weeks in odontoblasts of pulp capping group, while BSP was expressed at 4 weeks after pulpotomy. These results suggest that two different types of reparative dentin formation, dentin-like and bone-like dentin, may depend on the type and extent of the injury and the effect of the associated defense reaction on the structural and functional integrity at the dentin-pulp border.

A comparison of the length between mesio-buccal and mesio-lingual canals of the mandibular molar / 대한치과보존학회지

The aim of this study was to compare the initial apical file (IAF) length between the mesio-buccanl and mesio-lingual canals of the mandibular molar before and after early coronal flaring. Fifty mandibular molars with complete apical formation and patent foramens were selected. After establishing the initial working length of the buccal and lingual canal of the mesial root using the Root-ZX, radiographs were taken for the working length with a 0.5 mm short of #15 K-file tip just visible at the foramen under a surgical microscope (OPMI 1-FC, Carl Zeiss Co. Germany) at 25X. After early coronal flaring using the K3 file, additional radiographs were taken using the same procedure. The root canal morphology and the difference in working length between the buccal and lingual canals were evaluated. These results show that the difference in the length between the mesio-buccal and mesio-lingual canals of the mandibular molar was < or = 0.5 mm. If one canal has a correct working length for the mesial root of the mandibular molar, it can be used effectively for measuring the working length of another canal when the files are superimposed or loosening. In addition, the measured the working length after early coronal flaring is much more reasonable because the difference in the length between the mesio-buccal and mesio-lingual canals can be reduced.

Identification of putative pathogens in acute endodontic infections by PCR based on 16S rDNA / 대한치과보존학회지

The purpose of this study was to investigate the frequency of 7 putative pathogens in endodontic infections. The specimens were collected from infected pulpal tissue of patients who were referred for root canal treatment to the department of conservative dentistry, Chosun University. Samples were collected aseptically using a barbed broach and a paper point. The cut barbed broaches and paper points were transferred to an eppendorf tube containing 500 ml of 1 X PBS. DNAs were extracted from the samples by direct DNA extraction method using lysis buffer (0.5% EDTA, 1% Triton X-100). Identification of 7 putative pathogens was performed by PCR based on 16S rDNA. The target species were as follows: Porphyromonas endodontalis, Porphyromonas gingivalis, Prevotella intermedia, Prevotella nigrescens, Bacteroides forsythus, Actinobacillus actinomycetemcomitans, and Treponema denticola. Our data revealed that the prevalence of P. endodontalis was found in 88.6% (39/54), P. gingivalis 52.3% (23/44), P. nigrescens 18.2% (8/44), P. intermedia 15.9% (7/44), B. forsythus 18.2% (8/44), A. actinomycetemcomitans 2.3% (1/44), T. denticola 25% (11/44) of the samples. The high prevalence of P. endodontalis and P. gingivalis suggests that they may play an important role in the etiology of endodontic infections.

Sequencing of p53 Gene Mutations in Primary Breast Cancer Tissues / 대한암학회지

PURPOSE: The etiology of breast cancer involves very complex factors such as genetic, hormonal, and dietary. The peak age of Korean breast cancer is much earlier, about ten years, than those of western countries. The role of p53 gene on the carcinogenesis has been studied since 1991. This study was designed for the evaluation of genetic factor by determining p53 gene mutations in Korean breast cancer. MATERIALS AND METHODS: Mutation screening on p53 tumor suppressor gene was examined with PCR-SSCP and nucleotide sequencing technique from the genomic DNA extracted from the 27 fresh-frozen breast cancer tissues. RESULTS: Mutations in p53 gene exon 5-7 were identified in 2 of 27 cases (7%). One had a missense mutation substituted gcg with ggg at codon 159, exon 5, and the other had a point mutation substituted tcc serine to tGc cysteine at codon 241, exon 7. CONCLUSION: Point mutation of p53 gene in breast cancer seems to be the major defect found in Korean patients. It is necessary to perform further study in mutation of other exon 2, 4, 8, 9, and 11 of p53 gene to compare the genetic backgrounds of Korean breast cancer with those of westerns.