Hyun Seon Jang

Application of rpoB and Zinc Protease Gene for Use in Molecular Discrimination of Fusobacterium nucleatum Subspecies

ABSTRACT Fusobacterium nucleatum is classified into five subspecies that inhabit the human oral cavity (F. nucleatum subsp. nucleatum, F. nucleatum subsp. polymorphum, F. nucleatum subsp. fusiforme, F. nucleatum subsp. vincentii, and F. nucleatum subsp. animalis) based on several phenotypic characteristics and DNA-DNA hybridization patterns. However, the methods for detecting or discriminating the clinical isolates of F. nucleatum at the subspecies levels are laborious, expensive, and time-consuming. Therefore, in this study, the nucleotide sequences of the RNA polymerase β-subunit gene (rpoB) and zinc protease gene were analyzed to discriminate the subspecies of F. nucleatum. The partial sequences of rpoB (approximately 2,419 bp), the zinc protease gene (878 bp), and 16S rRNA genes (approximately 1,500 bp) of the type strains of five subspecies, 28 clinical isolates of F. nucleatum, and 10 strains of F. periodonticum (as a control group) were determined and analyzed. The phylogenetic data showed that the rpoB and zinc protease gene sequences clearly delineated the subspecies of F. nucleatum and provided higher resolution than the 16S rRNA gene sequences in this respect. According to the phylogenetic analysis of rpoB and the zinc protease gene, F. nucleatum subsp. vincentii and F. nucleatum subsp. fusiforme might be classified into a single subspecies. Five clinical isolates could be delineated as a new subspecies of F. nucleatum. The results suggest that rpoB and the zinc protease gene are efficient targets for the discrimination and taxonomic analysis of the subspecies of F. nucleatum.

Guided Tissue Regeneration of the Mixture of Human Tooth-Ash and Plaster of Paris in Dogs

This study evaluated the efficacy of periodontal tissue regeneration using guided tissue regeneration (GTR) with a mixture of tooth ash and plaster as a bone substitute material in the treatment of class II furcation defects in dogs. GTR was performed at the site of a surgically formed mandibular premolar bifurcation area in dogs. Four adult dogs were used in the animal study. The animals were in a good periodontal state without any systemic disease. A resorbable membrane (Bio-Gide®, Swiss) and bone graft material using a mixture of tooth ash and plaster were used to examine the biological activity. The defect in the control group was filled a Bio-Gide® only. For the experimental group, the defects were filled with a mixture of tooth ash and plaster and covered by a Bio-Gide®. Oral rinsing with 0.12% chlorhexidine was performed twice a day for 2 weeks. In control group, new bone formation was observed adjacent to the preexisting bone. Soft tissue ingrowth was also noted. In experimental group, new lamellar type trabecular bone formation as well as centum and PDL regeneration was observed in the base of the infrabony pocket. More bone regeneration would be expected when GTR is performed using a mixture of human tooth-ash and plaster of Paris as a bone graft material.

Bone Formation Effect of HA/β-TCP Composite Powders in Rabbit Calvarial Bone Defects: Histologic Study

This study evaluated the histology results of surgically created bone cavities in the calvaria of rabbits that were subsequently filled with a HA/ß-TCP composite powder developed in Korea (Dentium, Korea). Ten young adult rabbits were used. Four defects were surgically produced in the calvaria of each rabbit. These defects were classified into 4 groups: the control group, no graft materials; experimental group I, normal saline + graft materials; experimental group II, venous blood + graft materials; and experimental group III, graft materials only. The defects were randomly filled with the graft materials. The rabbits were sacrificed with at 1-, 2-, 4-, 6- and 8- weeks after surgery. The histology specimens were prepared using the general method with H & E staining at a 6 ㎛ thickness. Histologically, the degree of new bone formation was similar in all experimental groups. However, for experimental group II, many cells had gathered around the graft materials 1-week after surgery, and new bone formed slightly faster and than in the other groups. No bone formation was observed in the control group. Based on histology findings, the new HA/ß- TCP composite powders appeared to act as a scaffolding material for the regeneration of osseous defects.

Histomorphometric Analysis of Sinus Augmentation Using the ICB and MBCP

The purpose of this study is to evaluate the new bone formation of sinus augmentation with using ICB (Irradiated Cancellous Bone & Marrow; Rockey Mountain Tissue Bank, Denver, Co) and MBCP (Micro-Macroporous Biphasic Calcium Phosphate;Biomatlante, France). Study population consisted of 4 patients with maxillary posterior edentulous dentition and ridge heights were less than 5 mm. ICB (Rockey Mountain Tissue Bank, Denver, Co) and MBCP (Biomatlante, France) is mixed with 50: 50. After 6 months, the bone biopsies were done with 2mm trephine bur from lateral window opening. Mean new bone formations were 26.84 %, the residual grafts were 4.92 and soft tissues were 67.98 %. The small number of biopsies did not permit analysis of statistical significance. The variability of individual patient factors do not permit definitive conclusions. The mixtures of ICB & MBCP were superior or comparable to another various bone alternative materials in new bone formation of sinus floor elevation.