So-Young Yang

Improvement of the Properties of Mineral Trioxide Aggregate by Mixing with Hydration Accelerators

INTRODUCTION Mineral trioxide aggregate (MTA) is used widely in endodontic therapy. This study examined the setting time, compressive strength, and pH of MTA mixed with several hydration accelerators (calcium chloride, low-dose citric acid, calcium lactate gluconate solution). METHODS Group 1 (control) was obtained by mixing MTA with distilled water. In group 2, MTA containing 10% calcium chloride was mixed with distilled water. In group 3, MTA was mixed with 0.1% citric acid. In group 4, MTA was mixed with a calcium lactate gluconate solution. The setting time, compressive strength, and pH were examined. RESULTS The setting time of MTA mixed with hydration accelerators was significantly shorter than that of MTA mixed with water (P < .01). In particular, replacing distilled water with a calcium lactate gluconate solution provided a significant decrease in setting time. The compressive strengths of MTA mixed with hydration accelerators were significantly lower than that of MTA mixed with water (P < .01), but those values increased with time. The pH of MTA mixed with hydration accelerators was significantly lower than that of MTA mixed with water (P < .01) but stable at a high level (pH 11-12). CONCLUSIONS Hydration accelerators improved the setting time of MTA. Nevertheless, more study will be needed to improve MTA without impairing its preexisting advantages.

Parasympathectomy induces morphological changes and alters gene-expression profiles in the rat submandibular gland.

OBJECTIVE The chorda-lingual (CL) nerve carries parasympathetic fibers to the hilum of the sublingual and submandibular glands (SMGs) and evokes the secretion of saliva. The effect of cutting the CL nerve on the biological processes in SMGs was investigated by examining the gene-expression profiles in the SMGs after a surgical parasympathectomy. METHODS At day 3 after the CL nerve cut, the changes in the SMGs at both the experimental cut and contralateral control sides were analysed by microarray and light microscopy. The expression levels of 6 selected genes were confirmed by real-time PCR, Western blot and immunofluorescence staining. RESULTS The wet weight of the parasympathectomised SMGs decreased significantly compared to that of the contralateral side (p<0.05). Histological analyses after the parasympathectomy showed a widened interacinar space as well as some atropic changes to the acini of the SMGs in the cut side. Microarray analysis revealed that twofold differential expression in mRNA expression in the parasympathectomized SMGs were detected in 88 genes (0.004%): 41 genes were overexpressed, 11 were underexpressed and 36 were unknown. Changes of the expression of 6 selected genes detected by Western blot and/or real-time PCR were consistent with the microarray data. CONCLUSION The important genes involved in biological processes for salivation were identified through a large-scale gene expression analysis.

Relaxin is up-regulated in the rat ovary by orthodontic tooth movement.

Relaxin (Rln) is an ovarian hormone that stimulates osteoclastic and osteoblastic activities and connective tissue turnover. To investigate the expression of Rln during orthodontic tooth movement, rats were implanted with orthodontic appliances that connected a spring from the upper incisors to the first molar with a 70 cN force. Rats in each group were killed 6, 48, and 144 h after activating the appliance, and the levels of Rln1 and Rln3 expression in the ovary were determined by real-time RT-PCR, northern blots, western blots, and immunofluorescence analyses. The amount of tooth movement induced by the orthodontic force increased in a time-dependent manner. The levels of Rln1 mRNA increased by 12-, 41-, and 263-fold at 6, 48, and 144 h, respectively, after orthodontic tooth movement. The time-dependent increase in the concentration of Rln 1 protein in the ovary was also confirmed by western blotting. Rln 1 was localized in the granulosa cells of the ovarian follicles, and the immunoreactivity against Rln 1 was increased by the movement. In contrast, the concentration of Rln 3 was below the level of detection. The results of this study suggest that local changes in periodontal tissues induced by orthodontic tooth movement may affect Rln1 expression in the ovary. However, further studies are needed to decipher the mechanisms involved and the possible contribution of the increased level of expression of Rln 1 to the tooth movement.

Alendronate affects cartilage resorption by regulating vascular endothelial growth factor expression in rats.

This study was performed to determine effects of alendronate on the tibial proximal epiphyseal cartilage undergoing endochondral ossification and the expression of vascular endothelial growth factor (VEGF) from the cartilage. Alendronate was injected subcutaneously every other day in postnatal Day 1 Sprague Dawley rats. The rats were sacrificed 3, 5, 7, and 10 days after the first injection. The effect of alendronate treatment for 10 days was demonstrated from the morphological change that the area of the secondary ossification center in the epiphysis was significantly smaller in the alendronate group than that in the control group (P < 0.05). Strong immunoreactivity to VEGF was observed in the hypertrophied chondrocytes and some proliferating chondrocytes in the epiphyseal cartilage at postnatal Day 5 and was decreased after the alendronate treatment for 5 days. Immunoreactivity was observed in not only hypertrophied cells but also the peripheral cartilaginous matrix adjacent to the vascular canals invading into the central portion of the cartilage at postnatal Day 7. This reactivity was also reduced considerably by the alendronate treatment for 7 days. The level of VEGF expression was reduced by the alendronate treatment at both the transcription and translation levels. However, the transcriptional level of the flt‐1 and flk‐1 receptors was relatively unaltered by the treatment. These results suggest that VEGF expression is required for vascular invasion into the developing cartilage and alendronate can affect its resorption by downregulating VEGF expression. Anat Rec, 293:786–793, 2010.

Synaptic vesicle protein 2b is expressed temporospatially in (pre)odontoblasts in developing molars.

The formation of dentin and enamel is initiated by the differentiation of odontogenic precursor cells into odontoblasts and ameloblasts, respectively. This study was performed to identify new molecules involved in the differentiation of odontogenic cells. The genes expressed differentially between the root stage (after the differentiation of odontogenic cells and dental hard-tissue formation) and the cap stage (before the differentiation of odontogenic cells and dental hard-tissue formation) were searched using differential display PCR. For the first time, synaptic vesicle protein (SV) 2b, an important transmembrane transporter of Ca(2+) -stimulated vesicle exocytosis, was identified as a differentially expressed molecule. Real-time PCR and western blotting revealed an increase in the transcriptional and translational levels of SV2b during or after the differentiation of odontogenic cells. Immunofluorescence revealed this molecule to be localized in not only fully differentiated odontoblasts but also in pre-odontoblasts before dentin matrix secretion. The expression pattern of the SV2a isoform was similar to that of the SV2b isoform, whereas the SV2c isoform showed a contrasting pattern of expression. After treatment with alendronate, an inhibitor of protein isoprenylation for the transport of secretory vesicles, the expression of SV2a and SV2b decreased, whereas that of SV2c increased. These results suggest that the SV2 isoforms are functional molecules of (pre)odontoblasts which may be involved in vesicle transport.

Differential expression of cxcl‐14 during eruptive movement of rat molar germs

Tooth eruption at the early postnatal period is strictly controlled by the molecules secreted mainly from follicular tissues, which recruit monocytes for osteoclast formation. In this study, it was hypothesized that different molecules can be expressed according to the stages of tooth eruption. Rat molar germs together with follicles were extracted and DD-PCR was performed from the root formation stage 2nd molars germs (after eruptive movement) and cap stage 3rd molar germs (before movement) at postnatal day 9. Cxcl-14, a potent chemoattractant, was detected as one of the differentially expressed molecules from DD-PCR. Its expression increased significantly at the root formation stage, compared with the cap or crown formation stage at both transcription and translation levels. The expression patterns of cxcl-14 were consistent with those of MCP-1 and CSF-1, and opposite to OPG. Immunofluorescence showed that cxcl-14 was localized in the dental follicular tissues only at the root formation stage overlaying the proximo-occlusal region of the molar germs. Many osteoclasts appeared on the surface of the alveolar bone which overlayed the occlusal region of the root formation stage 2nd molar germs and underwent resorption. Cxcl-14 expression was reduced considerably at both the translation and transcription levels by an alendronate treatment. These results suggest that cxcl-14 may be implicated in the formation of the eruptive pathway of tooth germs via osteoclastogenesis.

Biocompatibility of experimental mixture of mineral trioxide aggregate and glass ionomer cement

Objectives: The purpose of the present in vitro study was to evaluate the biocompatibility of mineral triox- ide aggregate (MTA) mixed with glass ionomer cement (GIC), and to compare it with that of MTA, GIC, IRM and SuperEBA. Materials and Methods: Experimental groups were divided into 3 groups such as 1 : 1, 2 : 1, and 1 : 2 groups depending on the mixing ratios of MTA powder and GIC powder. Instead of distilled water, GIC liq- uid was mixed with the powder. This study was carried out using MG-63 cells derived from human osteosarcoma. They were incubated for 1 day on the surfaces of disc samples and examined by scanning electron microscopy. To evaluate the cytotoxicity of test materials quantitatively, XTT assay was used. The cells were exposed to the extracts and incubated. Cell viability was recorded by measuring the optical den- sity of each test well in reference to controls. Results: The SEM revealed that elongated, dense, and almost confluent cells were observed in the cultures of MTA mixed with GIC, MTA and GIC. On the contrary, cells on the surface of IRM or SuperEBA were round in shape. In XTT assay, cell viability of MTA mixed with GIC group was similar to that of MTA or GIC at all time points. IRM and SuperEBA showed significantly lower cell viability than other groups at all time points ( p < 0.05). Conclusions: In this research MTA mixed with GIC showed similar cellular responses as MTA and GIC. It suggests that MTA mixed with GIC has good biocompatibility like MTA and GIC. (J Kor Acad Cons Dent ABSTRACT

Differential expression of cyclophilin A and EMMPRIN in developing molars of rats.

A complex and intricate cascade of gene expression is essential for late stage tooth development. This study was performed to detect molecules involved in dental hard tissue formation and tooth eruption by comparing gene expression in cap stage molar germs (before eruptive movement and dental hard tissue formation) with that in root formation stage molar germs (after eruptive movement and dental hard tissue formation). DD‐PCR revealed that cyclophilin A (Cyp‐A), a potent chemoattractant for monocytes as well as a ligand for extracellular matrix metalloproteinase inducer (EMMPRIN) was expressed differentially in the two stages molar germs. The levels of Cyp‐A and EMMPRIN mRNA were significantly higher at the root formation stage than at the cap and crown stages of the molar germs. Immunofluorescence showed that Cyp‐A and EMMPRIN were expressed strongly in the follicular cells overlaying the occlusal region of the molar germs at the root formation stage. In contrast, their immunoreactivity was weak in the follicular tissues and was not region‐specific in molar germs at the cap stage. In addition, the MCP‐1 and CSF‐1 mRNA levels increased in parallel to that of Cyp‐A mRNA and the increased number of osteoclasts at the occlusal region. Immunoreactivity against Cyp‐A and EMMPRIN was also observed in the fully differentiated ameloblasts and odontoblasts. This study suggests that Cyp‐A and EMMPRIN play roles in the maturation of dental hard tissue and the formation of an eruption pathway. Anat Rec, 2012.

Comparison of Antibacterial effect of Listerine® with Various root canal irrigants

The purpose of this study is to compare the antibacterial effect of on two microorganisms (P. gingivalis and E. faecalis) with various root canal irrigants (NaOCl, CHX, EDTA) and to identify possibility of using as a root canal irrigant. Porphyromonas gingivalis ATCC 3327 and Enterococcus faecalis ATCC 29212 were used in this experiment. For the test irrigants, 0.5%, 1%, 2.5%, 5.25% NaOCl, 0.1%, 0.2%, 1%, 2% CHX, 0.5M EDTA (18.6% EDTA) and were prepared. Distiled water was used as control. Two methods-1) Comparison of turbidity in broth and 2) Agar diffusion test-were used to determine the extent of antibacterial effect of and to compare it with that of NaOCl, CHX, and EDTA. All solutions tested were effective against two bacterial strains compared with control (p showed significantly low antibacterial effect compared with the other root canal irrigants (p as compared with root canal irrigants in general so it is not suitable for the root canal irrigant.