Hyung Jun Choi

The effect of epigallocatechin-3-gallate (EGCG) on human alveolar bone cells both in vitro and in vivo

OBJECTIVE The effects of epigallocatechin-3-gallate (EGCG), a major catechin in green tea, on human and mouse osteoblasts remain controversial. This study investigated the direct effects of EGCG on human alveolar bone-derived cells (hABCs) both in vitro and in vivo. DESIGN hABCs which were collected from eight children (aged 7-9 years, seven males and one female) were treated with EGCG at various concentrations (1, 5, 10, 25, and 50μM), and a proliferation assay, flow cytometric analysis for apoptosis evaluation, migration assay, and in vitro osteogenic differentiation were performed. hABCs that were pretreated with 10μM EGCG and mixed with calcium phosphate carrier combined with EGCG (0.1, 0.5, or 1.5mg) in vivo were transplanted into immunodeficient mouse. Histological staining, quantitative gene expressions, and alkaline phosphatase activity were evaluated in the retrieved transplants. RESULTS The proliferation and migration were decreased when EGCG was present at over 25μM. The osteogenic differentiation increased slightly when EGCG was present at up to 10μM, and clearly decreased for higher concentrations of EGCG. In vivo, the potential for hard-tissue formation was slightly higher for the group with 0.1mg of EGCG than for the control group, and decreased sharply for higher concentrations of EGCG. CONCLUSION The present observations suggest that EGCG at a low concentration can slightly enhance the osteogenic effect in vivo, whereas at a higher concentration it can prevent the osteogenic differentiation of hABCs both in vitro and in vivo.

Comparative Study of Pulpal Responses to Pulpotomy with ProRoot MTA, RetroMTA, and TheraCal in Dogs' Teeth

INTRODUCTION This study was conducted to evaluate and compare pulpal responses to ProRoot MTA (Dentsply Tulsa Dental, Tulsa, OK), RetroMTA (Meta Biomed Co, Ltd, Seoul, Korea), and TheraCal (Bisco Inc, Schamburg, IL) in dog partial pulpotomy models. METHODS Partial pulpotomies were performed on 60 beagle teeth. The exposed pulp tissues were randomly capped with either ProRoot MTA (n = 15), RetroMTA (n = 15), TheraCal (n = 15), or interim restorative material as a negative control (n = 15). After 4 weeks, the teeth were extracted and processed for histologic and immunohistochemical examinations using osteocalcin and dentin sialoprotein. Calcific barrier formation, inflammatory reaction, and the odontoblastic layer were evaluated and scored in a blind manner. The areas of newly formed calcific barriers were measured for each group. RESULTS In most of the ProRoot MTA and RetroMTA specimens, continuous calcific barriers were formed, and the pulps contained palisading patterns in the odontoblastic layer that were free of inflammation. However, the TheraCal specimens had lower quality calcific barrier formation, extensive inflammation, and less favorable odontoblastic layer formation. Overall, areas of newly formed calcific barrier were higher in the ProRoot MTA and RetroMTA specimens than in the TheraCal specimens. Also, immunohistochemistry revealed that osteocalcin and dentin sialoprotein were more clearly visible in the ProRoot MTA and RetroMTA specimens than in the TheraCal specimens. CONCLUSIONS RetroMTA could provide an alternative to ProRoot MTA. Both materials produced favorable pulpal responses that were similar in nature, whereas TheraCal produced less favorable pulpal responses.

In vitro and in vivo characteristics of stem cells from human exfoliated deciduous teeth obtained by enzymatic disaggregation and outgrowth

OBJECTIVE Stem cells from human exfoliated deciduous teeth (SHED) are a good source of dental tissue for regeneration therapy, and can be obtained using different primary culture methods. The aim of this study was to determine the differences in the in vitro and in vivo characteristics between SHED isolated via enzymatic disaggregation (e-SHED) and outgrowth (o-SHED) primary culture methods. DESIGN Dental pulp stem cells were isolated from 14 exfoliated deciduous teeth by enzymatic disaggregation (n=7) and outgrowth (n=7). Their proliferation potential and colony-forming ability were evaluated in vitro, as was their mesenchymal stem-cell-marker expression (using flow cytometry), and their differentiation was verified using quantitative real-time PCR (qPCR) and histochemical staining. In addition, the qualitative and quantitative characteristics of the hard tissue that was generated after in vivo transplantation were compared using haematoxylin and eosin staining, immunohistochemical staining, qPCR, and quantitative alkaline phosphatase analysis. RESULTS The cell-proliferation potential, colony-forming ability, and Stro-1 and CD146 expression were higher in e-SHED than in o-SHED. While the in vitro adipogenic differentiation potential was greater in e-SHED than in o-SHED, the in vitro osteogenic differentiation did not differ significantly between the two cell types. Although in vivo hard tissue formation was greater following transplantation of o-SHED into mice, there was no difference in the quality of hard tissue generated by e-SHED and o-SHED. CONCLUSION The findings of this study indicate that e-SHED exhibit stronger stemness characteristics, but that o-SHED are more suitable for hard-tissue regeneration therapy in teeth.

Evaluation of Alveolar Bone Support of the Permanent Canine in Cleft and Noncleft Patients

Objective: To quantitatively compare the alveolar bone support ratio of the permanent canine in cleft patients who received secondary alveolar bone graft with that of the population without clefts. Design: Retrospective study utilizing periapical radiographs of the subjects with and without clefts. Setting: Hospital and university based. Patients: Eighteen unilateral and 9 bilateral cleft patients who had secondary bone graft procedures. Main Outcome Measures: Alveolar bone support of the permanent canine utilizing the ratio of bone height to root length. Results: Average bone support for the permanent canine was 88.55% in patients with clefts and 95.59% in patients with no history of clefts. This difference was statistically significant. There was no statistically significant difference in alveolar bone support ratio between the unilateral and bilateral cleft patients. Conclusions: Although alveolar bone support was significantly higher in the noncleft control group, a successful level of alveolar bone support was achieved for the permanent canine on the cleft site after secondary bone graft. There was no difference in alveolar bone support achieved for the permanent canine whether the type of the cleft was unilateral or bilateral.

TRPM7 Is Essential for RANKL-Induced Osteoclastogenesis

The transient receptor potential melastatin type 7 (TRPM7) channel is a widely expressed non-selective cation channel with fusion to the C-terminal alpha kinase domain and regarded as a key regulator of whole body Mg2+ homeostasis in mammals. However, the roles of TRPM7 during osteoclastogenesis in RAW264.7 cells and bone marrow-derived monocyte/macrophage precursor cells (BMMs) are not clear. In the present study, we investigate the roles of TRPM7 in osteoclastogenesis using methods of small interfering RNA (siRNA), RT-PCR, patch-clamp, and calcium imaging. RANKL (receptor activator of NF-κB ligand) stimulation did not affect the TRPM7 expression and TRPM7-mediated current was activated in HEK293, RAW264.7, and BMM cells by the regulation of Mg2+. Knock-down of TRPM7 by siTRPM7 reduced intracellular Ca2+ concentration ([Ca2+]i) increases by 0 mM [Mg2+]e in HEK293 cells and inhibited the generation of RANKL-induced Ca2+ oscillations in RAW264.7 cells. Finally, knock-down of TRPM7 suppressed RANKL-mediated osteoclastogenesis such as activation and translocation of NFATc1, formation of multinucleated cells, and the bone resorptive activity, sequentially. These results suggest that TRPM7 plays an essential role in the RANKL-induced [Ca2+]i oscillations that triggers the late stages of osteoclastogenesis.

Genetic Comparison of Stemness of Human Umbilical Cord and Dental Pulp

This study focuses on gene expression patterns and functions in human umbilical cord (UC) and dental pulp (DP) containing mesenchymal stem cells (MSCs). DP tissues were collected from 25 permanent premolars. UC tissue samples were obtained from three newborns. Comparative gene profiles were obtained using cDNA microarray analysis and the expression of tooth development-associated and MSC-related genes was assessed by the quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR). Genes related to cell proliferation, angiogenesis, and immune responses were expressed at higher levels in UC, whereas genes related to growth factor and receptor activity and signal transduction were more highly expressed in DP. Although UC and DP tissues exhibited similar expression of surface markers for MSCs, UC showed higher expression of CD29, CD34, CD44, CD73, CD105, CD146, and CD166. qRT-PCR analysis showed that CD146, CD166, and MYC were expressed 18.3, 8.24, and 1.63 times more highly in UC, whereas the expression of CD34 was 2.15 times higher in DP. Immunohistochemical staining revealed significant differences in the expression of genes (DSPP, DMP1, and CALB1) related to odontogenesis and angiogenesis in DP. DP and UC tissue showed similar gene expression, with the usual MSC markers, while they clearly diverged in their differentiation capacity.

Biological efficacy of two mineral trioxide aggregate (MTA)-based materials in a canine model of pulpotomy

The aim of this study was to compare the biocompatibility of Endocem Zr® and ProRoot MTA® by histopathologic analysis in a canine model of pulpotomy. This study utilized 39 teeth of two beagle dogs. The exposed pulp tissues were treated by pulpotomy using ProRoot MTA (n=19) or Endocem Zr (n=20). After 8 weeks, the teeth were extracted and processed with hematoxylin-eosin staining for histologic evaluation. Most of the specimens in both groups developed a calcific barrier at the pulp amputation site and formed an odontoblast layer. However, some of the Endocem Zr specimens showed less calcific barrier formation with a greater inflammatory response and less odontoblast layer formation when compared with the ProRoot MTA specimens. ProRoot MTA and Endocem Zr specimens developed a calcific barrier; however, ProRoot MTA was more biocompatible than Endocem Zr.

Continued root development of a surgically repositioned human incisor tooth germ

Conventional orthodontic traction may not be the treatment of choice in cases of inverted impaction of a maxillary incisor, especially when located near the alveolar crest. Poor prognosis is associated with the limited space for proper root development, resulting in a root too short for normal function and/or a severely dilacerated root interrupting the force-induced positioning. The surgical repositioning of ectopic impacted toothgerm before the development of root could be a valuable alternative choice of treatment before the decision of extraction. In this case report, an impacted immature incisor toothgerm in complete inversion was surgically repositioned using a closed-flap technique in a boy who was 6 years 8 months old. Continued root formation and spontaneous eruption were observed after surgery over the 51-month follow-up period, without pulpal or periodontal complications.

The Optimum Addition Ratio of Nano Hydroxyapatite to Glass Ionomer Dental Cement (Changes in Demineralization Resistance and Bonding Strength of Light Cured Glass Ionomer after the Addition of Nano Hydroxyapatite in Various Ratio)

The aim of this study was to evaluate changes in demineralization resistance and bonding strength of light cured glass ionomer after the addition of nano hydroxyapatite in various ratios. Fuji II LC GIC (GC Co., Japan) was used as the control group and also as a base material for experimental group. HA was mixed into the RMGIC at various ratio to create a HA-LC GIC mixture, preparing six experimental groups, i.e. 5%, 10%, 15%, 20%, 25%, 30% HA-LC GIC. According to the results, the bonding strength increased due to the addition of HA, showing the maximum value at the 15% nano HA group (p

Effects of Three Calcium Silicate Cements on Inflammatory Response and Mineralization-Inducing Potentials in a Dog Pulpotomy Model

This beagle pulpotomy study compared the inflammatory response and mineralization-inducing potential of three calcium silicate cements: ProRoot mineral trioxide aggregate (MTA) (Dentsply, Tulsa, OK, USA), OrthoMTA (BioMTA, Seoul, Korea), and Endocem MTA (Maruchi, Wonju, Korea). Exposed pulp tissues were capped with ProRoot MTA, OrthoMTA, or Endocem MTA. After 8 weeks, we extracted the teeth, then performed hematoxylin-eosin and immunohistochemical staining with osteocalcin and dentin sialoprotein. Histological evaluation comprised a scoring system with eight broad categories and analysis of calcific barrier areas. We evaluated 44 teeth capped with ProRoot MTA (n = 15), OrthoMTA (n = 18), or Endocem MTA (n = 11). Most ProRoot MTA specimens formed continuous calcific barriers; these pulps contained inflammation-free palisading patterns in the odontoblastic layer. Areas of the newly formed calcific barrier were greater with ProRoot MTA than with Endocem MTA (p = 0.006). Although dentin sialoprotein was highly expressed in all three groups, the osteocalcin expression was reduced in the OrthoMTA and Endocem MTA groups. ProRoot MTA was superior to OrthoMTA and Endocem MTA in all histological analyses. ProRoot MTA and OrthoMTA resulted in reduced pulpal inflammation and more complete calcific barrier formation, whereas Endocem MTA caused a lower level of calcific barrier continuity with tunnel defects.