Purpose: Since a free electron laser (FEL) not only has wavelength variability but also can irradiate a micropulse having an ultrashort pulse width, FEL can provide useful information on the effect of differences in pulse structure on irradiated materials, by irradiating laser beams tuned to the same wavelength as another laser for testing but with a different pulse structure. Methods: Consequently, the present study focused on the effect of ultrashort pulses emitted by an FEL, and a high-speed camera was used to observe the aspects of bovine dentin transpiration using the FEL tuned to the same wavelength as erbium-doped yttrium aluminum garnet (Er: YAG) lasers (2.94μm). The ejected transpiration particles were also observed using a scanning electron microscope (SEM), and the depth of transpiration was compared with that obtained using an Er: YAG laser. Additionally, irradiation was performed on bovine dentin with varying FEL irradiation wavelengths of 2.50μm, 2.94μm, 3.50μm, and 4.00μm, the depth of transpiration was measured, and increases in temperature at the irradiated site (irradiated side) and the opposite side of the sample directly under the irradiated site (dental pulp side) were also measured using a radiation thermometer. Result: 1. From 8,000 fps high-speed camera images of the bovine dentin at the time of ablation, a scattering of dentin particles was confirmed in the case with the irradiation by Er: YAG laser, and the SEM images of the collected ejected particles produced by Er: YAG laser irradiation showed dentin particles with sizes in the range of 10 to 100μm. On the other hand, in FEL, no scattering of ejected particles was observed with high-speed camera images taken with a 50-power lens. However, many microscopic particles with sizes in the range of 10 to 20μm were found with SEM. 2. Under the conditions of the experiment, the depths of transpiration exhibited by the Er: YAG laser and the FEL were 208μm and 670μm, respectively, with the latter being three times deeper. 3. The depths of transpiration under varying FEL wavelengths of 2.50μm, 2.94μm, 3.50μm, and 4.00μm were 35μm, 671μm, 414μm, and 220μm, respectively, demonstrating that the depth of transpiration was significantly larger at the wavelength of 2.94μm. 4. The peak temperature increases under varying FEL wavelengths of 2.50μm, 2.94μm, 3.50μm, and 4.00μm were 2.4℃, 2.2℃, 2.0℃, and 2.2℃ on the irradiation side, and 1.1℃, 1.1℃, 1.3℃, and 1.3℃ on the dental pulp side, respectively. Conclusion: These results showed that dentin could be ablated effectively by using a laser, having a pulse width shorter than the thermal relaxation time and an approximate wavelength of 2.94μm.

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Purpose: The resin coating technique currently is used for indirect restorative procedures after inlay cavity or full cast crown preparation. The technique has been applied to preventing contamination of the target tooth surface, protecting dental pulp tissue and preventing dentinal hypersensitivity in vital teeth. Hybrid Coat (HyC), a one-step resin coating material and bonding agent, has recently become commercially available. In a previous study, the author made the trial resin coating material T33, containing trimethylpropanetrimethacrylate (TMPT) based on HyC, to improve the dentin bond strength. This material achieved a higher shear bond strength than commercial HyC. However, T33 showed no significantly higher dentin bond strength than HyC. To further improve the dentin bond strength, a newly developed trial resin coating material, NC, was produced. Methods: The concentration in NC of camphorquinone (CQ), a kind of photosensitizer, was three times higher than in T33. NC was used as a base coating agent and coat-sponges with different molar ratio of NPG to CQ were used to test the shear bond strength to dentin. Additionally, the degree of polymerization, which is believed to affect dentin bond strength, was investigated to obtain a moderate molar ratio of NPG to CQ. Results: 1. The coating agent having three times more CQ than in T33 was shown to have higher average shear bond strength. However, no significant differences were observed in the shear bond strength in all samples. Shear bond strength did not increase with higher CQ. 2. The dentin shear bond strength of NC using coat-sponges with a different molar ratio of NPG to CQ was shown to be higher in NPG 4.4 and 7.3, which were significantly higher than in HyC. However, this strength was lower in 11.7 and 14.7, which contained a larger molar ratio of NPG. 3. The degree of polymerization of NC using coat-sponges with a different molar ratio of NPG to CQ was shown to be higher in NPG 4.4 and 7.3, but was lower in 11.7 and 14.7. Conclusion: These results showed that the dentin shear bond strength and the degree of polymerization of NC containing three times more CQ than T33 was increased when the molar ratios of NPG to CQ were 4.4 and 7.3, respectively.

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Purpose: Matrix metalloproteinase (MMP)-3 is a member of the MMP family, which comprises typical proteinases that degrade the extracellular matrix. MMP-3 is involved in various physiological and pathological processes. Recently, application of MMP-3 to injured pulp tissues was reported to induce angiogenesis and wound healing, but its anti-inflammatory functions are still unknown. The purposes of this study were to evaluate the effects of MMP-3 on inflammatory mediator synthesis from macrophages (RAW264) and mice dental papilla cells (MDP). Methods: RAW264 and MDP were cultured in 10% FBS supplemented D-MEM and MEMα, respectively. They were stimulated by LPS (100 ng/ml) in the presence or absence of MMP-3 (100 ng/ml) Non-LPS-stimulated RAW264 and MDP were used as controls. NO production was measured using the Griess reagent, and inflammatory mediator synthesis was evaluated using real-time PCR. Effects of MMP-3 for cell growth and caspase-3 activity were assessed. Results: Application of MMP-3 down-regulated the NO synthesis from LPS-stimulated macrophages, which showed a typical increase of NO synthesis compared to non-LPS-stimulated macrophages. mRNA of inflammatory mediators (IL-1β, IL-6, TNF-α and Cox2) was highly expressed in LPS-stimulated macrophages, but the application of MMP-3 significantly down-regulated their expression. Cox2 mRNA expression was highly induced in LPS-stimulated MDP, which was down-regulated by MMP-3 application. MMP-3 did not influence the cell growth and caspase-3 activity of RAW264 and MDP. Conclusion: MMP-3 down-regulated the inflammatory-mediator synthesis from LPS-stimulated macrophages and dental papilla cells, suggesting that MMP-3 may be a candidate for reducing pulpal inflammation.

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Purpose: The purpose of this study was to evaluate the influence of prophylactic paste containing fluoride on the enamel bond strength of single-step self-etch adhesives. Methods: Three adhesives, BeautiBond, Bond Force and G-Bond Plus, were used in this study. The enamel surfaces were treated with fluoride paste for 30 s twice a day. After 10 minutes (immediate group) and 7 days of treatments, bond strength specimens were made using each adhesive. Specimens were stored in 37℃ distilled water for 24 h, and then subjected to a shear bond strength test in a universal testing machine at a crosshead speed of 1.0 mm/min. Results: In the immediate group, the bond strengths of the enamel surface treated with fluoride paste, no significant differences were observed in all the adhesives, compared with the baseline. However, in prophylactic paste, the bond strengths were different, depending on the adhesives. On the other hand, in the 7-day group, the bond strengths were significantly lower in both pastes. After the bond strength test, the dominant failure mode was adhesive failure. Conclusion: The enamel bond strengths of the single-step self-etch adhesives were adversary affected by the use of prophylactic paste containing fluoride.

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Objective: The effect of brushing teeth with dentifrice containing Enterococcus faecium WB2000 on oral health was assessed in a double-blind randomized study. Materials and Methods: This study included 68 adult volunteers who provided informed consent to participate in the research project. The subjects cleaned their teeth with a dentifrice containing E. faecium WB2000 or placebo for four weeks. Oral assessment and saliva collection were performed on the day before study (baseline), and after two weeks and four weeks, and changes in oral health were evaluated. Quantitative analyses of the oral bacteria Streptococcus mutans, Streptococcus sobrinus, E. faecium, Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Fusobacterium spp., Prevotella intermedia and Treponema denticola in saliva samples were performed by the real-time polymerase chain reaction. Results: A total of 59 subjects including 30 (25 males, 5 females; mean age 44.3 ± 3.9 years) in the experimental group and 29 (22 males, 7 females; mean age 43.9 ± 4.2 years) in the placebo group were analyzed. There were no differences in age, gender, smoking habit, or oral clinical parameters between the two groups. In the experimental group, the amount of saliva significantly increased and salivary buffering capacity significantly improved after four weeks. The degree of plaque adherence was significantly decreased after two weeks in the experimental group and after four weeks in the placebo group. The index for periodontitis was significantly increased after four weeks in the placebo group, but was unchanged in the experimental group. Quantitative analyses of salivary bacteria revealed that the proportion of S. sobrinus, a cariogenic bacterium, was significantly decreased in the experimental group, but significantly increased in the placebo. Concerning periodontopathic bacteria, the proportions of A. actinomycetemcomitans and P intermedia significantly decreased in both groups, those of T denticola increased in the experimental group, and those of Fusobacterium spp. increased in the placebo group. The proportion of E. faecium significantly decreased in both groups. Conclusion: Brushing of teeth using the dentifrice containing E. faecium WB2000 improved oral health, as measured by an increased volume of saliva, significantly improved salivary buffering capacity, decreased dental plaque attachment, and reduced proportion of S. sobrinus, suggesting an anti-cariogenic effect in the oral cavity.

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Purpose: Enamel matrix derivative (EMD) extracted from the teeth germs of young pigs has been used clinically as a convenient material for periodontal tissue regeneration. However, EMD might be rejected by patients, because it is an animal-derived material and may carry unknown pathogenic organisms. The development of a newly synthesized oligopeptide with the same function as EMD is desirable. The present study examined the effects of a newly synthesized oligopeptide on human periodontal ligament cells by using matrix-assisted laser-desorption ionization time-of-flight mass spectrometry analysis of eosinophilic round bodies formed after subcutaneous injection of EMD into the backs of rats in a previous study. Methods: The in vitro effects of the oligopeptides on human periodontal ligament cells at the concentration of 100 ng/ml and on the control were determined by examining cell proliferation/viability and adhesion and chemotaxis. Cell proliferation/viability was determined after stimulating the oligopeptides for 1, 3, 24, or 72 hours. Cell adhesion was determined at 1 hour after seeding. Cell chemotaxis was determined at 1, 4 and 8 hours after seeding using the modified Boyden chamber method. Results: The proliferative response was enhanced by the oligopeptides. In the cell proliferation/viability, the fluorescence intensity at 100 ng/ml was significantly higher than that of the control at 1, 3, and 72 hours of culture. Additionally, the cell adhesion and chemotaxis of human periodontal ligament cells at 100 ng/ml was significantly higher than that of the control at all periods. Conclusion: These results suggest that the newly synthesized oligopeptides from enamel matrix derivative may enhance cell proliferation/viability, adhesion and chemotaxis of human periodontal ligament cells through the process of periodontal regeneration.

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