Young Chan Jeon

High-efficiency tooth bleaching using non-thermal atmospheric pressure plasma with low concentration of hydrogen peroxide.

Light-activated tooth bleaching with a high hydrogen peroxide (HP; H2O2) concentration has risks and the actual role of the light source is doubtful. The use of conventional light might result in an increase in the temperature and cause thermal damage to the health of the tooth tissue. Objective: This study investigated the efficacy of tooth bleaching using non-thermal atmospheric pressure plasma (NAPP) with 15% carbamide peroxide (CP; CH6N2O3) including 5.4% HP, as compared with conventional light sources. Material and Methods: Forty human teeth were randomly divided into four groups: Group I (CP+NAPP), Group II (CP+plasma arc lamp; PAC), Group III (CP+diode laser), and Group IV (CP alone). Color changes (ΔE ) of the tooth and tooth surface temperatures were measured. Data were evaluated by one-way analysis of variance (ANOVA) and post-hoc Tukeys tests. Results: Group I showed the highest bleaching efficacy, with a ΔE value of 1.92-, 2.61 and 2.97-fold greater than those of Groups II, III and IV, respectively (P<0.05). The tooth surface temperature was maintained around 37ºC in Group I, but it reached 43ºC in Groups II and III. Conclusions: The NAPP has a greater capability for effective tooth bleaching than conventional light sources with a low concentration of HP without causing thermal damage. Tooth bleaching using NAPP can become a major technique for in-office bleaching in the near future.

Optimization of Holographic PDLC for Binary Monomers

Reflective holographic polymer dispersed liquid crystals (HPDLC) have been fabricated by irradiating Ar-ion laser of various intensities on LC/acrylate monomer mixtures of various compositions sandwiched between two ITO coated glass plates. Polarized optical micrography (POM), scanning electron microscopy (SEM) images of the gratings and UV-visible spectra of the films have been obtained and reflection efficiency-irradiation intensity-monomer ratio relationships have been obtained.

The effects of Mg‐ion implantation and sandblasting on Porphyromonas gingivalis attachment

OBJECTIVES The purpose of this study was to evaluate the effect of titanium surface treatment on Porphyromonas gingivalis bacterial attachment. MATERIALS AND METHODS Titanium disks of 15 mm in diameter and 1 mm in thickness (n=40) were subjected to mechanical grinding, or sandblasting. Magnesium (Mg) ions were implanted onto the titanium surface using a plasma source ion implantation method. The structure, chemistry, and surface morphologies of the titanium surfaces were analyzed using scanning electron microscopy (SEM), X-ray photoelectron spectroscopy and Auger electron spectroscopy. Surface roughness was measured using a laser profilometer. Half of the titanium disks in each group were dipped in saliva for 24 h. All of the titanium specimens were rinsed with distilled water. A P. gingivalis strain was cultured in anaerobic conditions at 37°C for 72 h, and all titanium specimens were dipped in the bacterial suspension at 37°C for 24 h. Specimens were examined at × 3000 magnification using a SEM. The number of bacteria in each of 10 separate fields was determined by directly counting the number of bacterial colonies that adhered to each specimen. The mean values were calculated afterward. The resulting data were analyzed to assess the significance of observed differences based on the method of the surface treatment, ion implantation, and saliva dipping. RESULTS The amount of P. gingivalis attached to the sandblasted specimens was greater than that on the ground specimens (P<0.001). Moreover, surfaces with Mg-ion implantation had more attachments than nonimplanted surfaces (P<0.001). Saliva dipping acted synergistically with surface roughness and chemical composition of the specimens. CONCLUSIONS Chemically modified surface increase the attachment of a major periodontopathic bacterium, P. gingivalis.

Enhancement of the killing effect of low-temperature plasma on Streptococcus mutans by combined treatment with gold nanoparticles

BackgroundRecently, non-thermal atmospheric pressure plasma sources have been used for biomedical applications such as sterilization, cancer treatment, blood coagulation, and wound healing. Gold nanoparticles (gNPs) have unique optical properties and are useful for biomedical applications. Although low-temperature plasma has been shown to be effective in killing oral bacteria on agar plates, its bactericidal effect is negligible on the tooth surface. Therefore, we used 30-nm gNPs to enhance the killing effect of low-temperature plasma on human teeth.ResultsWe tested the sterilizing effect of low-temperature plasma on Streptococcus mutans (S. mutans) strains. The survival rate was assessed by bacterial viability stains and colony-forming unit counts. Low-temperature plasma treatment alone was effective in killing S. mutans on slide glasses, as shown by the 5-log decrease in viability. However, plasma treatment of bacteria spotted onto tooth surface exhibited a 3-log reduction in viability. After gNPs were added to S. mutans, plasma treatment caused a 5-log reduction in viability, while gNPs alone did not show any bactericidal effect. The morphological changes in S. mutans caused by plasma treatment were examined by transmission electron microscopy, which showed that plasma treatment only perforated the cell walls, while the combination treatment with plasma and gold nanoparticles caused significant cell rupture, causing loss of intracellular components from many cells.ConclusionsThis study demonstrates that low-temperature plasma treatment is effective in killing S. mutans and that its killing effect is further enhanced when used in combination with gNPs.

Physical stability of arginine-glycine-aspartic acid peptide coated on anodized implants after installation

PURPOSE The aim of this study was to evaluate the stability of arginine-glycine-aspartic acid (RGD) peptide coatings on implants by measuring the amount of peptide remaining after installation. MATERIALS AND METHODS Fluorescent isothiocyanate (FITC)-fixed RGD peptide was coated onto anodized titanium implants (width 4 mm, length 10 mm) using a physical adsorption method (P) or a chemical grafting method (C). Solid Rigid Polyurethane Foam (SRPF) was classified as either hard bone (H) or soft bone (S) according to its density. Two pieces of artificial bone were fixed in a customized jig, and coated implants were installed at the center of the boundary between two pieces of artificial bone. The test groups were classified as: P-H, P-S, C-H, or C-S. After each installation, implants were removed from the SRPF, and the residual amounts and rates of RGD peptide in implants were measured by fluorescence spectrometry. The Kruskal-Wallis test was used for the statistical analysis (α=0.05). RESULTS Peptide-coating was identified by fluorescence microscopy and XPS. Total coating amount was higher for physical adsorption than chemical grafting. The residual rate of peptide was significantly larger in the P-S group than in the other three groups (P<.05). CONCLUSION The result of this study suggests that coating doses depend on coating method. Residual amounts of RGD peptide were greater for the physical adsorption method than the chemical grafting method.

Effects of Mg-ion and Ca-ion implantations on P. gingivalis and F. nucleatum adhesion

The purpose of this study was to evaluate the effects of ion implantation on Porphyromonas gingivalis (P. gingivalis) and Fusobacterium nucleatum (F. nucleatum) bacterial adhesion. Titanium (Ti) discs of 15 mm diameter and 1 mm in thickness (n = 42, 7 per group) were fabricated. Magnesium (Mg) and calcium (Ca) ions were implanted into the Ti surfaces using a plasma-source ion-implantation method. The roughness, chemistry, morphology, and contact angle of the titanium surfaces were analyzed using scanning electron microscopy, Rutherford back-scattering spectroscopy, Auger electron spectroscopy, and contact angle meter. P. gingivalis and F. nucleatum strains were cultured in anaerobic conditions at 37°C for 72 hours, and all titanium specimens were dipped in the bacterial suspension at 37°C for 24 hours. Specimens were examined at 1,000× magnification using a fluorescence microscope. The number and total area of bacteria in each of 10 separate fields were determined by computer imaging analysis method. The resulting data was analyzed to assess the significance of observed differences based on the method of the surface treatment, ion implantation. The number of P. gingivalis and F. nucleatum attached to the Mg-(927 and 227, respectively) and Caionimplanted (1325 and 231, respectively) surfaces were greater than those attached to the non-implanted surfaces (306 and 98, p <.001). Total area occupied by P. gingivalis adhesion was greater than those of F. nucleatum in the Mgand Caion-implanted surfaces (p <.001). The types of ion and bacteria did not affect the amount of bacterial adhesion. Ion implantation enhanced the adhesions of P. gingivalis and F. nucleatum. Non-specific bonding derived from the electrostatic force affected by positively charged ions might be the predominant factor in bacterial adhesion. The possibility of specific bonding could not be ruled out in the Ca-ion- implanted surface.

Comparison of changes in retentive force of three stud attachments for implant overdentures.

PURPOSE The aim of this study was to compare the changes in retentive force of stud attachments for implant overdentures by in vitro 2-year-wear simulation. MATERIALS AND METHODS Three commercially available attachment systems were investigated: Kerator blue, O-ring red, and EZ lock. Two implant fixtures were embedded in parallel in each custom base mounting. Five pairs of each attachment system were tested. A universal testing machine was used to measure the retentive force during 2500 insertion and removal cycles. Surface changes on the components were evaluated by scanning electron microscopy (SEM). A Kruskal-Wallis test, followed by Pairwise comparison, was used to compare the retentive force between the groups, and to determine groups that were significantly different (α<.05). RESULTS A comparison of the initial retentive force revealed the highest value for Kerator, followed by the O-ring and EZ lock attachments. However, no significant difference was detected between Kerator and O-ring (P>.05). After 2500 insertion and removal cycles, the highest retention loss was recorded for O-ring, and no significant difference between Kerator and EZ lock (P>.05). Also, Kerator showed the highest retentive force, followed by EZ lock and O-ring, after 2500 cycles (P<.05). Based on SEM analysis, the polymeric components in O-ring and Kerator were observed to exhibit surface wear and deformation. CONCLUSION After 2500 insertion and removal cycles, all attachments exhibited significant loss in retention. Mechanism of retention loss can only be partially explained by surface changes.

The effect of bupivacaine·HCl on the physical properties of neuronal membranes

Fluorescent probe techniques were used to evaluate the effect of bupivacaine·HCl on the physical properties (transbilayer asymmetric lateral and rotational mobilities, annular lipid fluidity and protein distribution) of synaptosomal plasma membrane vesicles (SPMVs) isolated from bovine cerebral cortex. An experimental procedure was used based on selective quenching of both 1,3-di(1-pyrenyl)propane (Py-3-Py) and 1,6-diphenyl-1,3,5-hexatriene (DPH) by trinitrophenyl groups, and radiationless energy transfer (RET) from the tryptophans of membrane proteins to Py-3-Py. Bupivacaine·HCl increased the bulk lateral and rotational mobilities, and annular lipid fluidity in SPMVs lipid bilayers, and had a greater fluidizing effect on the inner monolayer than that of the outer monolayer. The magnitude of increasing effect on annular lipid fluidity in SPMVs lipid bilayer induced by bupivacaine·HCl was significantly far greater than magnitude of increasing effect of the drug on the lateral and rotational mobilities of bulk SPMVs lipid bilayer. It also caused membrane proteins to cluster. These effects of bupivacaine·HCl on neuronal membranes may be responsible for some, though not all, of the local anesthetic actions of bupivacaine·HCl.

Optimization of Holographic PDLC for Green

Abstract Reflective holographic polymer dispersed liquid crystals(HPDLC) have been fabricated by irradiating Ar-ion laser(λ=514 nm) of various intensities on LC/monomer mixtures sandwiched between two ITO coated glass plates. Gratings were written for various monomer compositions and laser intensities. UV-visible spectra have been analyzed. Eventually, reflective efficiency-irradiation intensity-monomer composition relationships have been obtained.

Effect of the use of a ready-made plastic stent on the peri-implant soft tissue

Abstract Objective. This study compared the effect of the use of a ready-made plastic stent on the width of peri-implant keratinized mucosa with that of conventional methods and examined the effects of a plastic stent on peri-implant soft tissue. Materials and methods. Five young-adult beagle dogs were used. Forty titanium implants were placed in the mandibular alveolar ridge. Stage 2 surgery was performed 8 weeks after implant installation. Each dog received a full-thickness, apically positioned flap (fAPF) with a lingual crestal incision using a suture material in the control group (n = 20) and a ready-made plastic stent in the test group (n = 20). The keratinized mucosa width after stage 2 surgery was measured in each group. The pocket depth, length of connective-tissue contact and biological width were measured in the tissue samples. A students t-test was used to test the differences between the groups (95% confidence level). Results. The width of the keratinized mucosa was significantly higher and the distance from the top of the implant platform to the mucogingival junction was significantly longer in the test group than the control group. Histometric observations revealed the pocket depth and biological width to be significantly lower in the test group than the control group. Conclusion. The use of a fAPF with a lingual crestal incision using a ready-made plastic stent can effectively preserve or enhance the width of the keratinized mucosa and might restore a more optimal biological environment at the early soft-tissue healing stage.