Combined effects of simvastatin and enamel matrix derivative on odontoblastic differentiation of human dental pulp cells.

INTRODUCTION: We previously reported that simvastatin and enamel matrix derivative (EMD) have a dentinogenic effect. However, there is little information about the combined effects of these 2 agents on odontoblastic differentiation. The aim of this study was to investigate the effects of combined treatment with simvastatin and EMD on odontoblastic differentiation of human dental pulp cells (hDPCs). This study further explored the role of extracellular signal-regulated kinase (ERK) as a target and mediator of the differentiation induced by simvastatin in hDPCs. METHODS: The odontoblastic differentiation was analyzed by alkaline phosphatase activity, real-time polymerase chain reaction (PCR) for odontoblastic/osteoblastic markers (ie, dentin sialophosphoprotein, dentin matrix protein 1, and osteonectin), and alizarin red S staining. We also explored the role of ERK signaling as a mediator of simvastatin by Western blotting and real-time PCR. The expression of osteoblast-specific transcription factors was detected by reverse-transcription PCR. RESULTS: The alkaline phosphatase activity and the expression of odontoblastic markers (ie, dentin sialophosphoprotein and dentin matrix protein 1) increased in simvastatin/EMD-treated cells. Mineralized nodule formation increased in EMD- and simvastatin/EMD-treated cells. Notably, the combined use of both simvastatin and EMD resulted in more potent differentiation than that observed after a single therapy. Simvastatin activated ERK phosphorylation and treatment with ERK inhibitor blocked the messenger RNA expression of odontoblastic markers. However, in simvastatin/EMD-treated cells, the expression of these genes did not decrease significantly. Compared with other groups, the EMD- and simvastatin/EMD-treated group showed a greater expression of osterix. CONCLUSIONS: Simvastatin promotes odontoblastic differentiation of hDPCs via the ERK signaling pathway. In addition, simvastatin-induced differentiation is facilitated by co-treatment with EMD. Collectively, these results suggest a new strategy to induce odontoblastic differentiation of hDPCs.

Mesiobuccal root canal anatomy of Korean maxillary first and second molars by cone-beam computed tomography.

OBJECTIVE: The aim of this study was to investigate the types of canal configurations and the incidence of a second mesiobuccal (MB2) canal in Korean maxillary molar mesiobuccal (MB) roots by analyzing cone-beam computed tomographic (CBCT) images. STUDY DESIGN: Three-dimensional CBCT images of 458 maxillary first molars and 467 second molars from 276 Korean patients were analyzed to determine the incidence of an MB2 canal, the types of canal configurations, and the correlations between the incidence of an MB2 canal and age, gender, and tooth position. RESULTS: The incidence of 2-canaled MB roots was 71.8% in first molars and 42.2% in second molars, with the most common configurations being Weine types III and II. The frequency of an MB2 canal decreased with age in both molars (P < .05). CONCLUSIONS: Types III and II canal configurations were the most prevalent in the 2-canaled MB roots of Korean maxillary molars.

A comparison of nickel-titanium rotary instruments manufactured using different methods and cross-sectional areas: ability to resist cyclic fatigue.

OBJECTIVE: This study examined the effect of the manufacturing methods (ground, electropolished, and twisted) and the cross-sectional area (CSA) of nickel-titanium (NiTi) rotary instruments on their cyclic fatigue resistance. STUDY DESIGN: A total of 80 NiTi rotary instruments (ISO 25/.06 taper) from 4 brands (K3, ProFile, RaCe, and TF) were rotated in a simulated root canal with pecking motion until fracture. The number of cycles to failure (NCF) was calculated. The CSA at 3 mm from the tip of new instruments of each brand was calculated. The correlation between the CSA and NCF was evaluated. All fractured surfaces were analyzed using a scanning electron microscope to determine the fracture mode. RESULTS: The TF instruments were the most resistant to fatigue failure. The resistance to cyclic failure increased with decreasing CSA. All fractured surfaces showed the coexistence of ductile and brittle properties. CONCLUSION: The CSA had a significant effect on the fatigue resistance of NiTi rotary instruments.

Chlorhexidine gluconate attenuates the ability of lipoteichoic acid from Enterococcus faecalis to stimulate toll-like receptor 2.

Chlorhexidine gluconate (CHX) has been widely used as a canal irrigant or an intracanal medicament on account of its antibacterial substantivity. This in vitro study aimed to determine if CHX attenuates the inflammatory activity of Enterococcus faecalis and its major virulence factor, lipoteichoic acid (LTA). An enzyme-linked immunosorbent assay showed that CHX-killed E. faecalis was less potent than heat-killed E. faecalis in the production of tumor necrosis factor alpha (TNF-alpha) by a murine macrophage cell line, RAW 264.7 (p < 0.05). Interestingly, pretreatment of LTA with 2% CHX for 6 hours or with 0.2% CHX for 24 hours almost eliminated the TNF-alpha inducibility (p < 0.05). Furthermore, CHX abrogated the ability of LTA to stimulate Toll-like receptor 2, resulting in the attenuated induction of TNF-alpha expression. Collectively, our results suggest that CHX can inactivate LTA of E. faecalis leading to the alleviation of inflammatory responses induced by E. faecalis and its LTA.