Kyung-San Min

Effect of Mineral Trioxide Aggregate on Dentin Bridge Formation and Expression of Dentin Sialoprotein and Heme Oxygenase-1 in Human Dental Pulp

This study was conducted to evaluate the pulpal response to direct capping with either mineral trioxide aggregate (MTA) or calcium hydroxide (CH) cement in humans, with a focus on dentin bridge formation and dentin sialoprotein (DSP) and heme oxygenase-1 (HO-1) expression. Direct pulp capping was performed in 20 cases of caries-free human third molars. The pulps were exposed and capped with either MTA or hard-setting CH. After 2 months, the teeth were extracted, and the specimens were prepared for histologic and immunohistochemical evaluations. Histologically, 100% of the MTA group and 60% of the CH group developed dentin bridges. The mean thickness of the dentin bridges observed in the MTA group was statistically greater than that of CH group. In addition, DSP and HO-1 were expressed in the odontoblast-like cells and pulp fibroblasts beneath the dentin bridge; furthermore, significantly greater immunostaining was observed in the MTA group than in the CH group. Collectively, these results indicate that MTA is superior to CH in terms of inducing the dentinogenic process in human pulp capping.

The Combined Effect of Mineral Trioxide Aggregate and Enamel Matrix Derivative on Odontoblastic Differentiation in Human Dental Pulp Cells

INTRODUCTION The current study investigated the effectiveness of enamel matrix derivative (EMD) and mineral trioxide aggregate (MTA) in inducing the differentiation of human dental pulp cells (HDPCs) into odontoblast-like cells in vitro. METHODS The effects of MTA and EMD on odontoblastic differentiation were indexed by alkaline phosphatase (ALP) activity and the expression of odontoblastic/osteoblastic markers, as determined by reverse-transcription polymerase chain reaction analysis. Mineralization was also evaluated by the staining of calcium deposits with Alizarin red. Cells were treated with a combination of MTA and EMD or with MTA alone. RESULTS Compared with MTA-treated cells on day 3, MTA/EMD-treated cells exhibited significantly greater increases in ALP activity and in dentin sialophosphoprotein and bone sialoprotein expression. Mineralization was significantly greater on day 7 in MTA/EMD-treated cells than in MTA-treated cells. CONCLUSIONS These results suggest that a combination of MTA and EMD promotes more rapid differentiation in HDPCs than MTA alone and that this combination is thus a potential pulp-capping agent.

Effects of Fibroblast Growth Factor-2 on the Expression and Regulation of Chemokines in Human Dental Pulp Cells

BACKGROUND Fibroblast growth factor-2 (FGF-2) participates in both hematopoiesis and osteogenesis; however, the effects of FGF-2 on chemokines during odontoblastic differentiation have not been reported. This study investigated whether human dental pulp cells (HDPCs) treated with FGF-2 could express chemokines during differentiation into odontoblastic cells and sought to identify its underlying mechanism of action. METHODS To analyze differentiation, we measured alkaline phosphatase (ALP) activity, calcified nodule formation by alizarin red staining, and marker RNA (mRNA) expression by reverse-transcriptase polymerase chain reaction (RT-PCR). Expression of chemokines, such as interleukin-6 (IL-6), IL-8, monocyte chemoattractant protein-1 (MCP-1), macrophage inflammatory protein-1α (MIP-1α), and MIP-3α, were evaluated by RT-PCR. RESULTS ALP activity, the mineralization, and mRNA expression for odontoblastic markers were enhanced by FGF-2 in HDPCs. FGF-2 also up-regulated the expression of IL-6, IL-8, MCP-1, MIP-1α, and MIP-3α mRNAs, which were attenuated by inhibitors of p38, ERK1/2 and p38 MAP kinases, protein kinase C, phosphoinositide-3 kinase, and NF-κB. CONCLUSION Taken together, these data suggest that FGF-2 plays a role not only as a differentiation inducing factor in the injury repair processes of pulpal tissue but also as a positive regulator of chemokine expression, which may help in tissue engineering and pulp regeneration using HDPCs. However, the fate of odontoblastic or osteoblastic differentiation, effective local delivery for FGF-2, interaction of chemotatic and odontogenic factors, and other limitations will need to be overcome before a major modality for the treatment of pulp disease.

Identification of Independent Middle Mesial Canal in Mandibular First Molar Using Cone-Beam Computed Tomography Imaging

INTRODUCTION The root canal treatment of a mandibular molar with aberrant canal configuration can be diagnostically and technically challenging. METHODS This case report presents the clinical management of a mandibular first molar with three separate mesial canals including middle mesial canal, which was confirmed by cone-beam computed tomography (CBCT) images. RESULTS Posttreatment images revealed three independent root canals in the mesial root obturated efficiently to the accepted lengths in all three canals. CONCLUSION This case report highlights the usefulness of CBCT imaging for accurate diagnosis and management of the unusual canal morphology.

Simvastatin Promotes Odontoblastic Differentiation and Expression of Angiogenic Factors via Heme Oxygenase-1 in Primary Cultured Human Dental Pulp Cells

INTRODUCTION Although simvastatin has multiple demonstrable effects, its function in dentinogenesis remains unclear. In this study, we tested the hypothesis that the addition of simvastatin to human dental pulp cells (HDPCs) stimulates odontogenesis both by promoting odontoblastic differentiation and by favoring the release of angiogenic factors. In addition, the role of heme oxygenase-1 (HO-1) in these effects was investigated. METHODS The expression of markers for odontoblastic differentiation and angiogenesis was analyzed by means of alkaline phosphatase (ALP) activity, alizarin red staining, and Western blotting. RESULTS Simvastatin enhanced the differentiation of HDPCs by up-regulating mineralization nodules and odontogenic markers as well as angiogenic markers. These phenomena were then correlated with the induction of HO-1 protein levels. The inducing effect of simvastatin on odontoblastic differentiation and angiogenesis was nullified by an HO-1 inhibitor and a carbon monoxide (CO) scavenger. CONCLUSIONS These results suggested that simvastatin exerts its odontoblastic differentiation and angiogenesis-inducing effects in HDPCs through a mechanism that involves the action of HO-1 and its product CO.

Biological Effects and Washout Resistance of a Newly Developed Fast-setting Pozzolan Cement

INTRODUCTION Mineral trioxide aggregate has been widely used as a retrograde filling material. The aim of this study was to evaluate the biological effects of a newly developed fast-setting, mineral trioxide aggregate-derived pozzolan cement (Endocem). Furthermore, we explored whether this cement is resistant to washout in comparison with ProRoot. METHODS Biocompatibility was evaluated on the basis of cell morphology and a viability test. The expression of osteogenic genes was evaluated by performing real-time polymerase chain reaction, and calcified nodule formation was assessed by alizarin red S staining. The setting time was measured, and washout testing was performed by placing the material into fetal bovine serum. RESULTS The biocompatibility and osteogenicity of Endocem were similar to those of ProRoot. Moreover, Endocem showed a higher resistance to washout than ProRoot did. CONCLUSIONS These results suggest that Endocem can be used as an available retrograde filling material because it sets faster and shows similar biological effects when compared with ProRoot.

Odontogenic responses of human dental pulp cells to collagen/nanobioactive glass nanocomposites

OBJECTIVES Collagen-based nanocomposite incorporating nanobioactive glass (Col/nBG) was developed as a scaffolding matrix for dentin-pulp regeneration. The effects of the novel matrix on the proliferation of human dental pulp cells (hDPCs) and their differentiation into odontoblastic lineage were investigated. METHODS Nanocomposite scaffold was prepared by incorporating nBG within the Col solution and then reconstituting them into a membrane form. Cell growth by MTS assay, adhesion by scanning electron microscopy (SEM), and odontoblastic differentiation by alkaline phosphatase (ALP) activity, mineralization, and the mRNA expression of differentiation-related genes of DPCs on each scaffold were evaluated. RESULTS The introduction of nBG significantly improved the bone mineral-like apatite formation in the simulated body fluid, suggesting excellent acellular bone-bioactivity. The hDPCs cultured on the Col/nBG nanocomposite have shown active growth behavior during culture for 14 days. The mRNA levels of major organic extracellular matrix of dentin, collagen type I and III were highly expressed in the Col/nBG matrix. Moreover, the alkaline phosphatase (ALP) activity and the mineralized nodule formation were increased in the Col/nBG nanocomposite compared to those in Col. Odontoblatic differentiation genes, including dentin sialophosphoprotein, dentin matrix protein I, ALP, osteopontin and osteocalcin were significantly stimulated in the Col containing nBG. Moreover, the key adhesion receptor integrin components α2 and β1, specifically binding to collagen molecule sequence, were upregulated in Col/nBG compared to Col, suggesting that odontogenic stimulation was closely related to the integrin-mediated process. SIGNIFICANCE In our study, the nanocomposite Col/nBG matrix induced the growth and odontogenic differentiation more effectively than Col alone, providing a promising scaffold condition for regeneration of dentin-pulp complex tissue.

Microleakage and fracture patterns of teeth restored with different posts under dynamic loading

STATEMENT OF PROBLEM Many studies concerned with the microleakage of endodontically treated teeth restored with posts and cores and subjected to loading can be found in the literature. However, no studies have investigated microleakage under dynamic loading with simultaneous dye penetration, which is more relevant to clinical situations. PURPOSE The purpose of this study was to compare microleakage and to classify fracture patterns of endodontically treated teeth restored with various post systems under dynamic loading. MATERIAL AND METHODS The crown portions of 40 human mandibular incisors were sectioned at the cementoenamel junction, and the teeth were endodontically treated. Teeth were divided into 4 groups (n=10): teeth restored with a cast post and core, prefabricated metal post (ParaPost), fiber-reinforced composite resin post (FRC Postec), and ceramic post (Cosmopost). After preparing the post space, each post was cemented with dual-polymerized resin cement (DuoLink). With the exception of the cast post-and-core group, the cores were formed directly using a light-polymerized composite resin (Light-Core). An intermittent load of 98 N at 1 Hz was applied for 50,000 cycles at an angle of 135 degrees to the long axis of the restored teeth, which were immersed in a 0.5% basic fuchsin solution. The ratio of the dyed surface area to the total area of the sectioned root surface was determined using an image analysis program. The data were analyzed by a 1-way ANOVA and Duncans multiple range test (alpha =.05). The fracture patterns of the teeth were classified according to their fracture propagation lines. RESULTS The cast post group showed a significantly higher level of microleakage compared to the other groups (P=.001). Regarding the failure mode, the FRC Postec and Cosmopost groups showed fracture patterns that would favor retreatment. The number of cycles of repeated loading was not significantly different among the groups (P=.161). CONCLUSIONS Both FRC Postec and Cosmopost groups showed less microleakage under dynamic loading and fracture patterns favoring a retreatment of fractured specimens.

Effects of simvastain and enamel matrix derivative on Portland cement with bismuth oxide-induced growth and odontoblastic differentiation in human dental pulp cells.

INTRODUCTION We previously reported that bismuth oxide containing Portland cement (BPC) showed similar biocompatibility to Portland cement (PC) in periodontal ligament cells. However, the bioactivity of simvastatin and Emdogain (Biora AB, Malmö, Sweden) on BPC was not reported. The aim of this study was to evaluate the effects of simvastatin and Emdogain on BPC compared with mineral trioxide aggregate (MTA) in human dental pulp cells (HDPCs). METHODS Cell growth was determined by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium-bromide (MTT) assay. Differentiation was evaluated by alkaline phosphatase (ALP) activity, alizarin red staining, and reverse-transcriptase polymerase chain reaction. RESULTS The cell growth of HDPCs exposed to Emdogain and simvastatin plus BPC was superior to those administered BPC alone and similar to those that received MTA for 14 days. The simvastatin and Emdogain groups increased the odontogenic potential of the BPC group with respect to ALP activity, mineralization nodules, messenger RNA expression of ALP, osteopontin, osteocalcin, Runx2, and osterix. CONCLUSIONS These results suggest that simvastatin and Emdogain improved cell growth and the differentiation of the BPC group in HDPCs and may be useful ingredients in BPC as pulp-capping material.

Role of SIRT1 in Heat Stress- and Lipopolysaccharide-induced Immune and Defense Gene Expression in Human Dental Pulp Cells

INTRODUCTION Although bacterial infection and heat stress are common causes of injury in human dental pulp cells (HDPCs), little is known about the potential defense mechanisms mediating their effects. This study examined the role of SIRT1 in mediating heat stress and lipopolysaccharide (LPS)-induced immune and defense gene expression in HDPCs. METHODS HDPCs were exposed to heat stress (42°C) for 30 minutes after stimulation with LPS (1 μg/mL) for 48 hours. The expression of defense genes was evaluated by reverse-transcriptase polymerase chain reaction, Western blotting, and enzyme-linked immunosorbent assay. RESULTS LPS and heat stress synergistically increased the expression of SIRT1 and immune and defense genes such as interleukin (IL)-8, hemeoxygenase-1 (HO-1), and human β-defensin 2 (hBD-2). Resveratrol enhanced LPS- and heat stress-induced expression of HO-1 and hBD-2 but reduced IL-8 messenger RNA levels. The stimulation of HO-1 and hBD-2 messenger RNA expression by LPS and heat stress was inhibited by sirtinol; SIRT1 small interfering RNA; and inhibitors of p38, ERK, JNK, and nuclear factor κB. CONCLUSIONS These results show for the first time that SIRT1 mediates the induction of immune and defense gene expression in HDPCs by LPS and heat stress. SIRT1 may play a pivotal role in host immune defense system in HDPCS.