• The Journal of the Korean dental association
• /
• v.48 no.6
• /
• pp.454-458
• /
• 2010

Dental caries is one of the most common chronic diseases in the world, which are caused by complex actions of oral such factors as the bacteria, food, tooth, saliva and other factors. Although this is one of the typical oral diseases, we can acquire a high prophylactic effect by use of proper prophylactic measures and management. At the beginning of the 1940s, fluorine was first introduced to prevent dental caries which now is widely used. The fluorine application effects are varied from different concentrations and categories of fluorine, and different application method and frequency, etc. There is great debate on the best application method at the present. Dental clinics use iontophoresis as the application method and use it clinically. It uses APF (1.23%, Acidulated phosphate fluoride, APF) and uses 2% NaF so as to encourage more absorption of fluorine. Recently, fluoride varnish, which uses admixture mucus of colophony resin into 5% NaF, and a variety of forms that can be applied in the oral cavity are still being continuously researched. When using fluoride topical application on the enamel surface, it was highly recommended that fluoride varnish be used directly after fluoride iontophoresis rather than fluoride iontophoresis only or fluoride varnish by itself. The new method is more effective and does not need repeated application.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.29 no.10
• /
• pp.641-646
• /
• 2016

Coil specimen was prepared by coating a copper wire with two varnish thin layers: the first was polyamideimide (PAI)/nanosilica (5 wt%) varnish and the second was anti-corona PAI/nanosilica (15 wt%) varnish. Insulation breakdown voltage was investigated under inverter surge condition at $20^{\circ}C$, $70^{\circ}C$, $100^{\circ}C$, $150^{\circ}C$, $200^{\circ}C$, $250^{\circ}C$, respectively. The insulation lifetime of the two layered coil was tens of times longer than that of original PAI coil. And the insulation lifetime decreased with increasing ambient temperature because there was weak binding strength between copper and varnish layer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.07a
• /
• pp.472-475
• /
• 2003

In this paper, insulating varnish has been used for field magnet and armature impregnated insulating material of electric locomotive and traction motor. When it was duplicated coating, it could be accuse internal void, and which could change electrical characteristics. We used to boundary elemental method of simulation tool, and improved optimal insulating design of insulating varnish according to measuring electric distribution in void of specimen.

• Proceedings of the KIEE Conference
• /
• 2004.05b
• /
• pp.180-182
• /
• 2004

We have investigated characteristics of varnish and oil impregnant. When transformers are manufactured with some moisture and varnish impregnant not entirely dried, those should be caused by factors that deteriorate the electrical or mechanical property after installation. Therefore, in this study we experienced moisture content of the new insulating paper and the varnish impregnant paper in the ratio of time for confirming factors that deteriorate the paper characteristics. Besides, we investigated a property study that was experienced the value of dielectric strength and tensile strength as no serviced insulating samples of transformer.

• Journal of Electrical Engineering and Technology
• /
• v.10 no.4
• /
• pp.1700-1711
• /
• 2015

In the last decade it has been witnessed significant developments in the area of nano particles and nano scale fillers on electrical, thermal, and mechanical properties of polymeric materials such as resins, varnishes, enamel and bakelites. The electric and thermal properties were more important in the electrical equipments for both steady state and transient state conditions. This paper deals with the characterization of the electric and thermal properties of the pure varnish and zirconia (ZrO₂) filler mixed varnish. The electric properties such as dielectric loss (tan δ), dielectric constant (ε), dielectric strength and partial discharge voltage were analyzed and detailed for different samples. It was observed that zirconia nano filler mixed varnish has the superior dielectric and thermal properties when compared to those of standard varnish. It has shown that at power frequency the 1wt% nano composite sample has the higher permittivity value when compared to other samples. It has been examined that the 1wt% sample was having higher inception and extinction voltages when compared to other samples. It has been observed that 1wt% sample has higher dielectric strength when compared with other samples. There has been an improvement of thermal property by adding few weight percent of zirconia nano fillers. There was not much variation in glass transition among the nano mixed composites. The weight loss was improved at 1wt% of the zirconia nano fillers.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.25 no.4
• /
• pp.825-836
• /
• 1998

The intention of this study was to investigate the preventive effect of chlorhexidine varnish on enamel demineralization. The sample consisted of 57 first premolars scheduled to be extracted for orthodontic purposes. The control group (N=10) was left untreated and the experimental groups were worn with specially designed stainless steel orthodontic bands on premolar for plaque accumulation. The group 1 (N=9) was worn band only, the group 2 (N=19) was applied with chlorhexidine varnish for one time, and the group 3 (N=19) was applied with chlorhexidine varnish for 3 times once a week. After 4 weeks of experimental periods, every specimen were examined by SEM and Vickers hardness test to evaluate and compare the degree of enamel decalcification. The results were as follows: 1. Although SEM revealed various degree of enamel demineralization in every experimental groups, the group 1 showed more severe demineralizations than the group 2 and 3. 2. The mean Vickers Hardness Numbers measured in this study seemed to reveal that there was a statistically significant difference between the control goup and the group 1 (P<0.05), and also a significant difference between the group 1 and the group 2, 3 (P<0.05). And there was no significant difference between the group 2 and the group 3 (p>0.05). 3. The results of VHN did not deemed to show a statistically significant difference between maxillary premolar and mandibular premolar in both group 2 and group 3 (P>0.05).

• Journal of the korean academy of Pediatric Dentistry
• /
• v.47 no.3
• /
• pp.266-276
• /
• 2020

The purpose of this study was to compare the remineralization effect of 38% silver diamine fluoride (SDF) and 5% sodium fluoride (NaF) varnish on artificially induced enamel caries. The present study standardized the physiochemical characteristics of the tooth structure using bovine teeth, realized the wash-off action of agents using a saliva, reproduced an environment similar to mouth through pH-cycling, and comparatively assessed the remineralization effect of 38% SDF and 5% NaF varnish in a non-destructive method using micro-CT. And the remineralized enamel surface structure was analyzed by scanning electron microscopy (SEM) and energy dispersive X-Ray spectroscopy (EDS). In both SDF and NaF varnish, mineral density (△Hounsfield unit value) and the volume of enamel restored to normal mineral density through remineralization gradually increased with time. And the SDF showed a much higher level of increase in mineral density at all depths and remineralized volume than NaF varnish. According to SEM analysis, the surface roughness decreased in the order of artificial saliva, NaF varnish and SDF. In addition, EDS analysis showed that silver ion was precipitated on the enamel surface in SDF group. In conclusion, SDF had a greater remineralization effect than NaF varnish on demineralized enamel.

• Journal of Korean society of Dental Hygiene
• /
• v.9 no.4
• /
• pp.740-752
• /
• 2009

Objectives : This study was carried out to examine the effect of varnish fluoride and APF gel on the acid resistance and the remineralization of the enamel. Methods : At first, the microhardness changes of enamel surface were measured after demineralizing the fluoride treated tooth surface. Next, the changes were measured after fluoride application to the demineralized enamel surface. Results : 1. Acid resistance was higher in varnish fluoride groups than APF gel groups and the difference was significant(p<0.001). 1) Varnish fluoride groups Microhardness of enamel surface showed $297.76{\pm}9.89$ after fluoride treatment and $260.90{\pm}28.67$ after drmineralization. The changes of Vickers hardness number(VHN) were $-36.86{\pm}27.30$. 2) APF gel groups Microhardness of enamel surface showed $298.79{\pm}17.28$ after fluoride treatment and $43.75{\pm}18.58$ after demineralization The changes of VHN were $-255.04{\pm}21.31$. 2. No significant changes were surveyed in both varnish fluoride groups and APF gel groups as for remineralization of enamel(p>0.05). 1) Varnish fluoride groups Microhardness of enamel surface showed $46.58{\pm}15.42$ after demineralization and $46.61{\pm}15.70$ after fluoride treatment. The changes of VHN were $0.02{\pm}3.75$. 2) APF gel groups Microhardness of enamel surface showed $47.13{\pm}19.31$ after demineralization and $42.59{\pm}16.12$ after fluoride treatment. The changes of VHN were $-4.54{\pm}5.06$. Conclusions : Varnish fluoride showed higher acid resistance than APF gel, however both of them were observed to have no effect on the remineralization of the enamel.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.07a
• /
• pp.299-302
• /
• 2001

In this study, we are studied the electrical conduction and dielectric breakdown properties of insulating varnish. In order to analyze the molecular structure and physical properties of insulating varnishs, FT-lR was used. As the result, it can be confirmed that the peak of alcoholic group appeared in wavenumbers 3452[cm$\^$-1], the peak of =CH appeared in 3080[cm$\^$-1] and the peak of -CH appeared in 2919[cm$\^$-1] respectively. The following results were obtained from electrical properties of insulating varnish. The amplitude of current density was decreased by thickness increasing and the current density was effected by the thermal energy from external due to temperature increasing. In study temperature dependence of dielectric strength, the specimen of 10[$\mu\textrm{m}$] thickness was measurement from room temperature to 180[$^{\circ}C$]. It is confirmed that the temperature regions below 60[$^{\circ}C$] is due to electron avalanche breakdown and the temperature regions over 60[$^{\circ}C$] is due to free volume breakdown which makes electron movements easy.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.25 no.3
• /
• pp.513-524
• /
• 1998

The purpose of this study was to compare the staining ratio on the enamel surface following the use of chlorhexidine mouthwash and the chlorhexidine varnish application. Labial and lingual surfaces of maxillary and mandibular incisors of adults were selected to evaluate the staining ratio. The control group was consisted of 8 individuals, the experimental group 1 and 2 were consisted of 50 each. Prophylaxis with pumice was performed to remove the stain already established on the enamel surface of all groups. The group 1 was asked to use chlorhexidine mouthwash(Hexadent, chlorhexidine gluconate 1ml/100ml) for a minute twice a day. The chlorhexidine $varnish^{(R)}$($Chlorzoin^{(R)}$, consisted of solution 1(10% chlorhexidine acetate) and solution 2(polyurethane sealant)) was applied on the enamel surfaces of the group 2. After 4 weeks of experiment, intraoral photogragh of tooth surfaces were taken in order to record the stained area on the enamel of the control and the experimental groups. Outline of teeth and the stained area in the photographs was traced on the OHP film. Scanner and computer processor were used to calculate stained surface ratio.