• Restorative Dentistry and Endodontics
• /
• v.32 no.4
• /
• pp.377-384
• /
• 2007

Present tooth bonding system can be categorized into total etching bonding system (TE) and self-etching boding system (SE) based on their way of smear layer treatment. The purposes of this study were to compare the effectiveness between these two systems and to evaluate the effect of number of themocycling on microleakage of class V composite resin restorations. Total forty class V cavities were prepared on the single-rooted bovine teeth and were randomly divided into four experimental groups: two kinds of bonding system and another two kinds of thermocycling groups. Half of the cavities were filed with Z250 following the use of TE system, Single Bond and another twenty cavities were filled with Metafil and AQ Bond, SE system. All composite restoratives were cured using light curing unit (XL2500, 3M ESPE, St. Paul, MN, USA) for 40 seconds with a light intensity of $600mW/cm^2$. Teeth were stored in distilled water for one day at room temperature and were finished and polished with Sof-Lex system. Half of teeth were thermocycled 500 times and the other half were thermocycled 5,000 times between $5^{\circ}C$ and $55^{\circ}C$ for 30 second at each temperature. Teeth were isolated with two layers of nail varnish except the restoration surface and 1 mm surrounding margins. Electrical conductivity (${\mu}A$) was recorded in distilled water by electrochemical method. Microleakage scores were compared and analyzed using two-way ANOVA at 95% level. From this study, following results were obtained: There was no interaction between variables of bonding system and number of thermocycling (p = 0.485). Microleakage was not affected by the number of thermocycling either (p = 0.814). However, Composite restoration of Metafil and AQ Bond, SE bond system showed less microleakage than composite restoration of Z250 and Single Bond, TE bond system (p = 0.005).

• Imaging Science in Dentistry
• /
• v.30 no.4
• /
• pp.265-274
• /
• 2000

Purpose: The aims of the present study are to determine the optimum compression rate in terms of file size reduction and diagnostic quality of the images after compression and evaluate the transmission speed of original or each compressed image. Materials and Methods: The material consisted of 24 extracted human premolars and molars. The occlusal surfaces and proximal surfaces of the teeth had a clinical disease spectrum that ranged from sound to varying degrees of fissure discoloration and cavitation. The images from Digora system were exported in TIFF and the images from conventional intraoral film were scanned and digitalized in TIFF by Nikon SF-200 scanner (Nikon, Japan). And six compression factors were chosen and applied on the basis of the results from a pilot study. The total number of images to be assessed were 336. Three radiologists assessed the occlusal and proximal surfaces of the teeth with 5-rank scale. Finally diagnosed as either sound or carious lesion by one expert oral pathologist. And sensitivity, specificity and k value for diagnostic agreement was calculated. Also the area (Az) values under the ROC curve were calculated and paired t-test and oneway ANOVA test was performed. Thereafter, transmission time of the image files of the each compression level was compared with that of the original image files. Results: No significant difference was found between original and the corresponding images up to 7% (1 : 14) compression ratio for both the occlusal and proximal caries (p<0.05). JPEG3 (1 : 14) image files are transmitted fast more than 10 times, maintained diagnostic information in image, compared with original image files. Conclusion: 1 : 14 compressed image file may be used instead of the original image and reduce storage needs and transmission time.

• Journal of Korean society of Dental Hygiene
• /
• v.13 no.1
• /
• pp.146-157
• /
• 2013

Objectives : The purpose of this paper is to analyze the effects of short-term oral health care on children at community care centers, in order to allow them to maintain good oral health. Methods : The SPSS (Statistical Package for Social Science), Window Version 18.0 was used to analyze the data for the children's present conditions of oral health; their ability to maintain good oral health; their general knowledge about oral health; changes in their oral health awareness; habit formations concerning oral health; and the satisfaction level of oral health education. Results : 1. While the average number of teeth before the program is 19.84(6.19), that of teeth after the program is 21.33(6.10). 2. Average test scores on oral health information of post-program are improved more than those of pre-program. 3. The 8th measurement of O'Leary plaque index is 3.27, which shows significant changes. 4. Satisfaction level with the program is 4.75(0.45), which shows that children are satisfied with the program. Conclusions : The paper shows that in order to maintain the oral health of children at community care centers, their habit formation and practice for the oral health is important. It also shows that cooperation among communities and public health centers is important to develop various oral health education programs like the program.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
• /
• v.17 no.1
• /
• pp.271-278
• /
• 1987

The purpose of the present study was to investigate associations between periapical and bitewing techniques by assessing the crestal alveolar bone. This article also reports the ability of these two techniques to correctly detect evidence of interproximal dental caries, and comparison between the interproximal overlapping of teeth. Bitewing and periapical radiographs were used from posterior quardants of 243 dental students in Seoul National University. The distance from cemento-enamel junction to the alveolar crest (CEJ-AC) was measured for each proximal surface from the distal of cuspid to the distal of second molar. Data were arranged according to the proximal surface examined, and bitewing and periapical measurements were compared using paired tests. The obtained results were as follows: 1. In maxilla, a significant t ratio with a P value of 0.05 or less reached for 100% and in mandible, reached for 94%. 2. The anatomic limitations imposed on periapical radiographic technique, most often result in somewhat foreshortened radiographic images. This situation would tend to be accentuated by the anatomical restrictions of the hard palate. 3. Consequently, since the significant differences frequently exist between measurements obtained from bitewing and periapical techniques, it is important to define which technique is used. 4. The number of the interproximal overlapping was the largest medial side of the maxillary second molar, while the smallest at the distal side of the mandibular second premolar. And the overall number of the interproximal overlapping was more (538) in the periapical technique than in the bitewing technique (372). 5. The interproximal dental carious lesions were detected more (74) on the bitewing films than on the periapical ones (23). The fact was resulted from the small number of interproximal overlapping and relative easi- ness of obtaining horizontal angulation in taking the bitewing radiographs.

• Journal of Periodontal and Implant Science
• /
• v.25 no.3
• /
• pp.459-469
• /
• 1995

The objectives of this study were to examine the prevalence of gingival recession (GR)and cervical abrasion(CA) and to relate some considered factors to them. We selected 308 subjects, consisting of male 174 and female 134, who had 14 teeth at least. As age increased, the prevalence rates of GR & CA was increased. And both the rates of GR & CA were higher in male than in female. Interestingly, the effect of alcohol consumption was the highest in GR and smoking affected CA highly among several variables. However, we could not prove the direct relationship between drinking & smoking and GR & CA. Only we assumed poor oral hygiene due to drinking & smoking as one of predisposing factors. The result of this study did not show the obvious factor which affected GR and CA greatly. The present study suggested that GR & CA should be related to a number of factors.

• The Journal of Korea Assosiation for Disability and Oral Health
• /
• v.1 no.1
• /
• pp.25-32
• /
• 2005

The purpose of this study was to furnish data on the disabled's oral health status of the disabled in Busan, Korea. Material and Methods: Two dentists who were well experienced in caries examination surveyed the oral health status on 793 of disabled men in Busan from March to June in 2000 under natural solar light with plane mirror by the criteria which are suggested by World Health Organization (WHO). Results: The number of present permanent teeth of the disabled are lower than the undisabled. DMF rate and DMFT indices of the disabled were higher than the undisabled. DT rate of the disabled was higher than the undisabled. Conclusions: The development of community oral health care programs for the prevention and treatments of dental caries for the disabled is needed and active administrative policies should be established for the promotion of the disabled's oral health.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.21 no.11
• /
• pp.1827-1836
• /
• 1997

In this paper, the clamping type forging of helical gears has been investigated. Clamping type forging is an operation in which the product is constrained to extrude sideways through an orifice in the container wall. Punch is cylindrical shaped. The punch compresses a cylindrical bilet placed in a die insetr. As a consequence the material flows in a direction perpendicular to that of punch movement. The forging has been analysed by using the upper-bound method. A kinematically admissible velocity field has been developed, wherein, an involute curve has been introduce to re4present tooth profile of the gear. Numerical calculations have been carried out to investigate the effects of various parameters, such as module, number of teeth, helix angle, friction factor and initial height of billet on the forging of helical gears. Some firgiing experiments were catrried out with aluminium alloy to show the validity of the analysis. Good agreement was found between the predicted values of the forging load and obtained from the experimental results.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.31 no.4
• /
• pp.671-679
• /
• 2004

The purpose of this study was to develop a practical caries activity test by fluorescence using laser, plasma light and halogen light. The subjects of study were 45 children of 7-8 years old Argon laser, plasma light and halogen light were irradiated to buccal or labial surface of all teeth. Fluorescence of initial carious lesion from teeth was observed through barrier filter and the number of teeth showing lesion was counted. Visual examination for the dDfFtT, mutans streptococci screening test and Lactobacilli colony counting were also done. Data analysis was accomplished by Axelsson's method. The result from the present study can be summarized as follows. 1. Laser, plasma light and halogen light could detect the initial carious lesions better than visual examination(p<0.05). 2. There was positive correlation between laser(r=0.42), plasma light(r=0.41), halogen light(r=0.39) and dBfFtT rate(p<0.01). 3. The specificity sensitivity and predictive value was showed highest value in laser, but was showed favorable value in plasma light and halogen light. In regard to above results, laser, plasma light and halogen light all considered to be reliable method for determining individual caries activity. And they were also considered to be practical method because it would be simple, inexpensive, and time saving method.

• Current Research on Agriculture and Life Sciences
• /
• v.3
• /
• pp.197-202
• /
• 1985

A number of the remains of animals were unearthed from Anup pond in Kyungzu during the repair work in March, 1975. To determine the species of animal origin and the ages and sexes of them, some judgement and morphological examination of the animal remains were conducted and the results obtained with the bone remains believed to be of horses are summarized as follow. 1. The total of the remains of horses excavated were 28 teeth and 9 pieces of bones. The bones were classified into on each of skull, humerus, radius, the first phalanx, femur and tibia, the remaining 3 pieces being cervical vertebrae. 2. The cranial bone was relatively in fair preservation and, on the whole, the gross appearance was quite similar to that of current Korean native horses. With the defacement of the teeth, the horse remains could be of a mare with the age less than 10 years. 3. The size of the appendicular skeletons were a bit smaller than that of Korean native horse at present. 4. The results obtained in the present study strongly indicated that the horse remains excavated from the An up pond could be of at least 2 or more horses.

• Korean journal of applied entomology
• /
• v.33 no.4
• /
• pp.216-224
• /
• 1994

Sex combs which lack in females are characteristic of some members of the subgenus Sophophora When present, they can be van/ from a single blistle to very extensive structures, but the meianogaster subgroup of the subgenus Sophophora have only on the f~rst tarsal segments of the fore legs. D mauritiona among the melanogaster compler of the melar~ogaster subgroup have significantly more sex comb teeth (mean 12.75) than other specie& and the yakubo complex (range of the mean 6.84-758) have less than the melanogaster complex (range of the mean 835-12.75). In sex comb tooth number of interspecd~ch ybrids among the melonogoster complex, there appeared difference u;ith parental species Thus, analysis of male sex comb tooth in FI hybrid could not exhibit the direction of hereditan/ nature. On the other hand, D auraria (the montium subgroup), D suzuki (the suzuki subgroup) and D, lutecens (the takohashii subgroup) of the melanogaster species have two sex combs on the first and second tarsal segments, and the mean number were different according to the species.