• The Journal of Korean Academy of Prosthodontics
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• v.32 no.2
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• pp.268-280
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• 1994

Tissue conditioners have been used for treatment of denture stomatitis caused by wearing of dentures. Early studies pointed out Candide albicans (C. albicans) as main etiologic factor, and antifugal agents were added for control of the species. But there is a little information about broad comparison on the effect of tissue conditioners and antifungal agents added. The purpose of the present study was to compare the inhibiting effect of four tissue conditioners and one temporary soft liner on the growth of C. albicans for treatment of denture stomatitis using gel diffusion method by measuring diameter of the zone of growth inhibition. Three antifungal agents were added to each material for evaluation of the effect of added agents. Finally, observation was made to evaluate the effect of the loss of antifungal elements by aging of the specimen. The results of this study were obtained as follows : 1. Tempo had remarkable antifungal effect showing the zone of growth inhibition as 2.35 mm at 1st day, and was most effective on End: 4th and 7th day from incubation (p<0.05). But Coecomfort, Dura conditioner, Visco-gel, Coe-soft had little antifungal effect from the 1st day of incubation. 2. Nystatin was most effective showing 9.60-12.04 mm of zone of inhibition at the 1st day from incubation. The antifungal properties were reduced to amphotericin B, chlorhexidine and materials without agent (p<0.05), and the effect was diminished by time. 3. As pretreatment with amphotericin B, nystatin, chlorhexidine, Tempo was very effective at the 1st day from incubation showing zone of inhibition as 3.65, 12.04, 4.78 mm with addition of each agent. Dura conditioner had strongest antifungal effect at the next day as 2.86, 5.33, 1.29 mm of zone of inhibition, and yielding results of Coe-comfort, Tempo, Coe-soft was shown at 4th and 7th day from incubation (p<0.05). Taken all together, tissue conditioners have little antifungal effect except Tempo. Formation of the zone of growth inhibition was due to agents amphotericin B, nystatin, chlorhexidine and nystatin was most effective. Conclusively, it is advisable to select material which is effective on the growth of C. albican and consider addition of antifungal agents for treatment of denture stomatitis.

• Journal of the korean academy of Pediatric Dentistry
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• v.32 no.4
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• pp.649-656
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• 2005

The present study was designed to formulate cephalometric norms of normal occlusion for usage in orthodontic diagnosis of malocclusion in Korean children. Thirty two children, aged 4 to 6, with normal occlusion were chosen for this study, Sagittal and vertical relations were analyzed using lateral cephalogram and clinical photos and the measurements were compared with those of adults. On skeletal sagittal analysis, the mean values of the SNA and SNB angles were $83^{\circ}\;and\;78.72^{\circ}$. It showed that the mandible was retrognathic and retropositioned in comparison to those of adults. On skeletal vertical analysis, the mean values of the genial angle was $127^{\circ}$. This showed high angle pattern in children and reduction of genial angle due to counterclockwise rotation of the mandible is expected with growth. On soft tissue analysis, children showed convex pronto, obtuse nasolabial angle. On dental analysis, the mean values of the U1 to SN and IMPA were $91.04^{\circ}\;and\;86.57^{\circ}$. This showed retroclined upper and lower deciduous teeth in comparison to adults. For skeletal values, the liner values were generally greater in males than females.

• Journal of the korean academy of Pediatric Dentistry
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• v.32 no.2
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• pp.312-320
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• 2005

The purpose of this study was to evaluate the polymerization contraction and the microhardness of compostie resin($Supreme^{(R)}$, Filtek $Flow^{(R)}$, 3M-ESPE, USA) according to irradiation modes of LED curing unit(Elipar $Freelight^{(R)}$, 3M-ESPE, USA). The strain guage method was used for determination of polymerization contraction. Sample were divided by 6 groups according to curing modes and filling method. Group A: $Supreme^{(R)}$, Filtek $Flow^{(R)}$ lining, 10seconds curing, Group B: $Supreme^{(R)}$, Filtek $Flow^{(R)}$ lining, 15seconds curing, Group C: $Supreme^{(R)}$, Filtek $Flow^{(R)}$ lining, 15seconds soft start curing, Group D: $Supreme^{(R)}$ only, 10seconds curing, Group E: $Supreme^{(R)}$ only, 15seconds curing, Group F: $Supreme^{(R)}$ only, 15seconds soft start curing. Preparations of acrylic molds were followed by filling and curing. Strain guage attached to each sample were connected to a strainmeter. Measurements were recorded at each second for the total of 10 minutes including the periods of light application. And microhardness of each group after 24hours from light irradiation were measured. Obtained data were analyzed statistically using Repeated measures ANOVA and Tukey test. The results of the present study are as follows: 1. In flowable resin liner group, soft start curing group was not found decrease of polymerization contraction. But, In Supreme only filling group, the lowest polymeriation contraction was found in soft start curing group. 2. 10 seconds curing group showed statistically significant reduction of polymerization contraction compared with 15 seconds curing group(p<0.05). 3. The microhardness values of each group not revealed significant difference(p>0.05). But, lower surface microhardness was not reached 80% of upper surface microhardness.

• The Journal of Advanced Prosthodontics
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• v.7 no.3
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• pp.191-198
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• 2015

PURPOSE. The purpose of this study was to compare the coronal bone level and patient satisfaction in 1-implant and 2-implant assisted mandibular overdentures. MATERIALS AND METHODS. Twenty patients who had maladaptive mandibular dentures were treated in this study. Patients were randomly divided into two groups. The first group received 1 implant (Simple line II, Implantium, South Korea) in their mandibular midline and the second group received 2 implants in their B and D regions (according to Misch's category). If the primary stability of each implant was at least 60 ISQ, ball attachment was placed and denture relined with soft liner. After 6 weeks, retentive cap incorporated with hard acrylic resin. In the 6 and 12 months recalls, periapical digital radiograph were made and visual analogue scale questionnaires were used to record patient satisfaction. The Friedman test was done for comparing the presurgical and postsurgical parameters in each group and the U-Mann Whitney test (P<.05) was done for comparison of post-treatment results between the two groups. RESULTS. All implants achieved sufficient primary stability to be immediately loaded. Patient satisfaction was high, and there were no significant differences between two groups (P>.05). In addition, mean marginal bone loss was $0.6{\pm}0.67$ mm in the first group and $0.6{\pm}0.51$ mm in the second group, after 12 month. Mean marginal bone loss showed no significant differences between two groups. CONCLUSION. This preliminary one-year result indicated that mandibular overdentures anchored to a single implant can be a safe and cost-effective method as a starting step for implant-overdenture treatment.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.18 no.1
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• pp.58-63
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• 2010

Introduction : Head trauma is the main cause of death in aircraft crash. In a Michigan study of structurally survivable, fatal accidents, 80% of the fatally injured had received head trauma. We tried to develop a new helmet for passengers, and perform its efficiency test. Methods : An aircraft helmet requires an excellent protection against head trauma, lightness, and small volumes. In addition, it must be wearable, fire resistant, and non toxic when it is burning. We developed two new helmets made from silicone foam which met all theses requirements. One was thin (2.5cm), and the other was thick (6.3cm). These looked like a motorcycle helmet and had only a soft silicone as liner material without an outer hard shell. Therefore we can carry them easily inside aircrafts. The standard test for helmet is Snell's drop test. It measures the impact acceleration of head shaped metal wearing helmet during we drop it at certain heights. Impact sites were total 5 sites (front, back, right, left and top) for each helmet. All these sites were impacted twice. Results : The thickness of impact sites varied from 2.5cm to 6.3cm. The impact acceleration of 2.5cm thickness site when it was dropped from 1.0 meter was 379g. But, that of 6.3cm thickness site when it was dropped from 1.5 meter was only 163g. Unfortunately, both helmets didn't meet the Snell Standard for motorcycle helmets. Discussion : If we add suitable outer hard shell, and change its thickness and design, the efficiency will be increased. A study indicated that helmet could reduce the risk of head trauma up to 85%. We made helmet for passengers in aircraft crash for the first time. If we improve its weak points, it will decrease the frequency of head trauma in aircraft craft.

• The Journal of the Acoustical Society of Korea
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• v.26 no.1E
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• pp.33-38
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• 2007

Compressional wave velocity and shear wave velocity were measured for gassy sediments collected from Jinhae Bay, Korea. To distinguish inhomogeneities of gassy sediments, Computed Tomography (CT) was carried out for gassy sediment using CT Scanner. The cored sediments are composed of homogeneous and soft mud (greater than $8{\Phi}$ in mean grain size) containing clay content more than 50%. In depth interval of gassy sediments, compressional wave velocity is significantly decreased from 1480m/s to 1360m/s, indicating that the gas greatly affects compressional wave velocity due to a gas and/or degassing cracks. Shear wave velocity shows a slight increasing pattern from ${\sim}55\;m/s$ in the upper part of the core to ${\sim}58\;m/s$ at 320 cm depth, and then decreases to ${\sim}54\;m/s$ in the lower part of the core containing a small amount of gas. But shear wave velocity in the gassy sediments is slightly greater than that of non-gassy sediments in the upper part of the core. Thus, the Vp/Vs ratio is decreased (from 30 to 25) in gas charged zone. The Vp/Vs ratio is well correlated with shear wave velocity, but no correlation with compressional wave velocity. This suggests that low concentrations of gas have little affects on shear wave velocity. By CT images, the gas in the sediments is mostly concentrated around inner edge of core liner due to a long duration after sediment collection.

• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.4
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• pp.325-335
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• 2008

The junction between resilient denture liner and the denture base is difficult to finish and polish due to difference of the physical property of the materials. Gaps tend to be formed during finishing and polishing procedures. The purpose of this study was measuring the width of junctional gap between $Molloplast-B^{(R)}$ and denture base material after finishing and polishing procedure, and evaluating the effect of method and direction on gap width. $Molloplast-B^{(R)}$ was processed (according to the manufacturer's instruction) against Lucitone $199^{(R)}$ acrylic resin. 50 specimens were fabricated with a raised center section. All of specimens were examined and photographed with a stereoscopic microscope(x120), and the largest gap along the junction of $Molloplast-B^{(R)}$ and acrylic resin on each specimen was measured. One-way analysis of variance(ANOVA) and independent t-test at 95% confidence level were used to analyze the data and to compare groups. The results of this study were as follows. In comparison with finishing tools, the gap width was the largest in $Molloplast^{(R)}$-Cutter and the smallest in FSQ-cross cut bur. There was statistically significant difference between FSQ-cross cut bur and $Molloplast^{(R)}$-Cutter(p<0.05). There was no significant difference in gap width between the direction of polishing. The mean value of gap width was the smallest in case of no polishing, and the largest in case of polishing with pumice & tin oxide. There was statistically significant difference between pumice and pumice & tin oxide. From the results, it is concluded that the use of $Molloplast^{(R)}$-Cutter in clinic need serious consideration even though it has good cutting ability. Further careful study is needed for finishing and polishing methods for decreasing gap width in junction of two materials.

• The Journal of Korean Academy of Prosthodontics
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• v.58 no.4
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• pp.275-281
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• 2020

Purpose: Development of a latent antimicrobial soft liner is strongly needed to overcome a possible inflammation related with its dimensional degrade or surface roughness. Modified tissue conditioner (TC) containing chitosan-doped silver nanoparticles (ChSN) complexes were synthesized and assessed for their characterizations. Materials and methods: ChSN were preliminarily synthesized from silver nitrate (AgNO₃), sodium borohydride (NaBH₄) as a reducing agent and chitosan biopolymer as a capping agent. Ultraviolet-visible and Fourier transform infrared spectroscopy were conducted to confirm the stable reduction of nanoparticles with chitosan. Modified TC blended with ChSN by 0 (control), 1.0, 3.0 and 5.0 % mass fraction were mechanically tested by ultimate tensile strength (UTS), silver ion elution and color stability (n=7). Results: At 24 hour and 7 day storage periods, UTS values were not significant (P>.05) as compared with pristine TC (control) and silver ion was detected with the dose-dependent values of ChSN incorporated. Color stability of TC were influenced by ChSN add, with the higher doses, the significantly greater color changes (P<.05). Conclusion: A stable synthesized ChSN was acquired and modified TC loading ChSN was characterized as silver ion releasing without detrimental physical property. For its clinical application, antimicrobial test, color control and multifactor investigations are still required.