• Journal of the korean academy of Pediatric Dentistry
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• v.45 no.3
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• pp.299-306
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• 2018

The aim of this study was to evaluate the effect of etching time and bonding agents on bond strength of sealant applied to the occlusal surface of primary molars. Forty non-carious exfoliated human primary molars were included in the study. The teeth were randomly divided into 4 groups for measurement. For group I, no acid etching treatment was used. For group II, III, and IV, acid etching gels were applied on the occlusal surface for 15, 30, and 60 seconds, respectively. Each group was divided into 2 subgroups; one group was treated with bonding agents on the enamel while the other was not. Microtensile bond strength was evaluated using a universal testing machine. There were no statistically significant differences in bond strength with varying duration of etching among groups. The results revealed that the use of bonding agents prior to application of fissure sealant increased the bond strength(p < 0.05). It could be concluded that etching time greater than 15 seconds does not significantly enhance the bond strength, but the use of bonding agents as an intermediate layer between the primary molar and fissure sealant would be beneficial in increasing the bond strength.

• Journal of the korean academy of Pediatric Dentistry
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• v.47 no.2
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• pp.157-166
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• 2020

The first dental visit is recommended at the time of the eruption of the first tooth and no later than 12 months of age. However, even before the age of 1, children can visit the dental hospital for various reasons. The purpose of this study was to analyze the reasons for the dental visit of infant. From January 2006 to December 2015, medical records of infants who visited the Department of Pediatric Dentistry of Kyung Hee University were analyzed. The total number of patients was 419 (238 males and 181 females). The reasons for the dental visits were trauma (47.5%), natal/neonatal tooth (19.8%), dental caries (8.1%), teething problem (4.3%), abnormal frenum (3.6%), soft tissue swelling (3.6%), Bohn's nodule (3.3%), cleft lip and palate (2.9%), gingival neoplasm (1.9%), tongue ulceration (1.7%), oral examination (1.4%), enamel hypoplasia (1.2%) and abnormal temporomandibular joint sound (0.7%). According to this study, there were various oral diseases that could occur in infants. Since infants are usually cared by caregivers, pediatricians, and obstetricians, education of oral diseases of infants is needed to manage the oral symptoms properly.

• Journal of Korean society of Dental Hygiene
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• v.13 no.4
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• pp.701-711
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• 2013

Objectives : The aim of this study was to evaluate the pH and buffering capacity in some commercial fermented milks in Korea. Methods : The study was carried ouf from June to August, 2012. In 35 liquid type, 79 condense-stirred type and 71 condense-drink type fermented milks, available on the market, pH and buffering capacity were measured. Titration(with NaOH) was used to determine the buffering effect of each fermented milk. They were titrated with 1 M sodium hydroxide, added in 0.1 milliliters increments, until the pH reached about 5.5 and 7.0. Results : The average pH of tested fermented milks was $4.08{\pm}0.27$. The average pH values of fermented milks were $3.64{\pm}0.22$ in liquid type, $4.14{\pm}0.12$ in condense-stirred type, and $4.22{\pm}0.17$ condense-drink type. The average buffering capacity (pH 5.5) of tested fermented milk was $2.40{\pm}0.54$. The average buffering capacity (pH 5.5) of liquid type fermented milk was $2.37{\pm}0.33$, condense-stirred type fermented milk was $2.77{\pm}0.46$ and condense-drink type fermented milk was $2.01{\pm}0.42$. The average buffering capacity (pH 7.0) of tested fermented milks was $4.00{\pm}0.87$. The average buffering capacity (pH 7.0) of liquid type fermented milk was $3.11{\pm}0.36$, condense-stirred type fermented milk was $4.78{\pm}0.55$ and condense-drink type fermented milk was $3.58{\pm}0.59$. Conclusions : The average pH of tested fermented milks in this study was lower than pH 4.5. The type of fermented milks was an important factor for selection of fermented milk which is related with enamel erosion.

• Restorative Dentistry and Endodontics
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• v.24 no.1
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• pp.88-99
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• 1999

The purpose of this study was to investigate the physical properties of experimental composite resins made with the spherical and crushed fillers. The 14 experimental composite resins containing 0, 5, 10, 15, 20 and 25%(w/w) in spherical filler group and 0, 10, 20, 30, 40, 50, 60 and 70%(w/w) in crushed filler group, incorporated in a Bis-GMA matrix (Aldrich Co., USA), were made with 1% ${\gamma}$-methoxy silane treated fillers. The polymer matrix was made by dissolving 0.7%(w/w) of benzoyl peroxide(Janssen Chemical Co. Japan) in methacrylate monomer, whereupon 0.7%(v/v) N,N-dimethyl-p-toluidine(Tokyo Kasei Co. Japan) was added to the monomer. The weight percentage of each specific particle size distribution could be determined from a knowledge of the specific gravity, the weight(w/w), and corresponding volume %(v/v) of the filler sample in resin monomer. In crushed silica group and spherical silica group, the diametral tensile strengths and compressive strengths were measured with Instron Testing Machine(No.4467), and analyzed in 14 experimental composite resins made by filler fractions. The shear bond strength of 14 experimental composite resins to bovine enamel was measured with universal testing machine(Instron No.4467). The fracture surfaces were sputter-coated with a gold film and investigated by SEM. The results were as follows; 1. The diametral tensile strength was tendency to increase in crushed silica group, but not in spherical silica group. The highest diametral tensile strength was found in 20% filler fractions of two groups. 2. The compressive strength was higher in 15%(w/w) and 20%(w/w) in spherical silica group than in crushed silica group, but not in spherical silica group. 3. The significant correlation was noticed in increase in shear bond strength in crushed silica group, but not in spherical silica group. 4. The significantly highest shear bond strength was noticed in 50% filler concentration in crushed silica group, and in 15% filler concentration in spherical silica group, it was not significant in relation. 5. In crushed silica group, cut surface of resin matrix and the interface between resin and filler is obvious. In spherical silica group, fractures that occurred through the filler particles were round in shape.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.34 no.5
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• pp.532-536
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• 2008

Purpose: This study was designed to evaluate effect of EMD on proliferation of HPDLCs and MC3T3-E1 cells in high glucose condition in vitro. Material and method: The Human PDL fibroblasts(HPDLCs) were obtained through typical way and the cells used in this experiment were divided in 4 groups. $1{\times}10^4/ml$ HPDLCs suspension was cultured in typical DMEM and assigned to group 1. The cells cultured in DMEM which included 400mg/dl glucose are allocated to group 3. Group 2 and 4 are established by adding EMD to group 1 and 3 respectively. These control and experimental groups had been cultured for 24 and 48 hours, and MTT assay was conducted. The differences of each group in cellular proliferation was evaluated. The same experiment was conducted for preosteoblast (MC3T3-E1) with adding $25\;{\mu}g/ml$ EMD. Results: EMD had the same effect on both PDL cells and MCT3T3-E1 cells. The experimental group had more meaningful differences and active cellular proliferation than the control group did. The EMD accelerated cellular proliferation not only in normal glucose condition but also in high glucose condition. The same results were observed via MTT assay; EMD-added experimental group had more meaningful differences and showed higher cellular activity than control group did. Each experimental and control group was inspected for statistical significance through Kruskal-Wallis Test. Statistical significances were observed among these groups. (SPSS 12.0 Chicago, IL, USA, p=0.008, p=0.011) Conclusion: EMD is considered to accelerate proliferation of PDL cells and MC3T3-E1 cells in high glucose condition as well as normal glucose condition.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.8
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• pp.176-182
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• 2018

One of the most important factor of esthetic prosthesis is the color of the teeth. Zirconia is produced in the process of design, milling, coloring, drying, and sintering. The effect of the drying degree of zirconia colorant on the color tone is examined. For the experiment, a total of 45 zirconia specimens(15 for each) were fabricated by using cad/cam system. The zirconia specimens(L block(LAZOR), Z block(Zircos-E block posterior), A block(AlphaZ)) were then subjected to zirconia sintering in accordance with the manufacturer's instructions, using a chemical coloring agent to Non-drying(0sec), intermediate (10sec), and completely dried (10min) temperature holding times. The color tone was measured using a spectrophotometer. The results were analyzed with a One-way analysis of variance and the Tukey post-hoc test (${\alpha}=.05$) The $L^*$ values of L, A specimens, $a^*$ values of A specimens, and $b^*$ values of Z specimens were not statistically different according to the degree of drying (p>0.05), While the $L^*$ value of Z specimen, $a^*$ value of L, Z specimen, $b^*$ values of L, A specimens were statistically different according to the degree of drying(p <0.05). In conclusion, the drying of zirconia colourants improves zirconia brightness and increases the optical properties of the enamel.

• The korean journal of orthodontics
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• v.25 no.5 s.52
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• pp.605-611
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• 1995

The purpose of this study was to evaluate effects of time on shear bond strengths of a light-cured glass ionomer cement and chemically cured resin cement to enamel, and to observe the failure patterns of bracket bondings. Shear bond strength of a light-cured glass ionomer cement were compared with that of a resin cement. Metal brackets were bonded on the extracted human bicuspids. Specimens were subjected to a shear load(in an Instron machine) after storage at room temperature for 5 and 15 minutes; after storage in distilled water at $37^{\circ}C$ for 1 or 35 days. The deboned specimens were measured In respect of adhesive remnant index. The data were evaluated and tested by ANOVA, Duncan's multiple range test, and t-test, and those results were as follows. 1. The shear bond strength of light-cured glass ionomer cement is higher than that of resin cement at 5 and 15 minutes. 2. The shear bond strengths of both light-cured glass ionomer cement and resin cement increase with time. There was no significant difference in those of both 1 day group and 35 day group 3. Light-cured glass ionomer cement is suitable as orthodontic bracket adhesives

• The korean journal of orthodontics
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• v.39 no.2
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• pp.105-111
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• 2009

Objective: To estimate the effects of bracket material type on enamel decalcification during orthodontic treatment, this study analyzed the adhesion level of mutans streptococci (MS) to orthodontic bracket materials in vivo. Methods: Three different types of orthodontic bracket materials were used: stainless steel, monocrystalline sapphire, and polycrystalline alumina. A balanced complete block design was used to exclude the effect of positional variation of bracket materials in the oral cavity. Three types of plastic individual trays were made and one subject placed the tray in the mouth for 12 hours. Then, the attached bacteria were isolated and incubated on a mitis salivarius media containing bacitracin for 48 hours. Finally, the number of colony forming units of MS was counted. The experiments were independently performed 5 times with each of the 3 trays, resulting in a total of 15 times. Mixed model ANOVA was used to compare the adhesion amount of MS. Results: There was no difference in colony forming units among the bracket materials irrespective of jaw and tooth position. Conclusions: This study suggested that the result of quantitative analysis of MS adhesion to various orthodontic bracket materials in vivo may differ from that of the condition in vitro.

• Journal of Oral Medicine and Pain
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• v.25 no.4
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• pp.415-425
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• 2000

In order to obtain the basic data concerning the optimal lasing conditions in using Nd:YAG laser as an adjunctive modality of periodontal therapy of root planing without irreversible structural deterioration of cervical cementum, the author selected 36 human teeth having no cervical abrasion and caries (; 12 anteriors, 12 premolars. 12 molars) extracted due to periodontal diseases, and divided them into 4 groups as Group I, II, III and IV (; each group of 3 anteriors, 3 premolars, 3 molars), and prepared a cementum specimen with thickness of $1.0mm{\pm}0.2mm$ sectioned longitudinally at the middle of mesio-distal thickness (; Group I) or horizontally at 1mm-2mm below the cemento-enamel junction (; Group II, III, IV) from each tooth of each group by low speed diamond wheel saw, and treated them with 0.5 M ethylene diamine tetraacetic acid (; EDTA, pH=7.4) for 2 minutes for elimination of remnants during tooth-sectioning. And the author applied the laser energy from a fiberoptic delivered, free running, pulsed Nd:YAG laser (; wavelength 1064nm. pulse duration $120{\mu}sec$, fiber diameter $320{{\mu}m}$) to cementum surfaces in triplicates of one experiment under the following lasing conditions: 1. stationary mode of fiber in contact to cementum surfaces without air-spray (; Group I )/with air-spray (; Group II), 2. unidirectional moving mode of fiber in contact to cementum surfaces under speed of 3mm-4mm/sec without air-spray (; Group III)/with air-spray (; Group IV), 3. energy per pulse (mJ/pulse) [; energy density ($J/cm^{2}$)] in order of 1.0W/10Hz (100J/pulse); $124J/cm^{2}$, 0.5W/10Hz (50mJ/pulse); $62J/cm^{2}$, 0.4W/10Hz (40mJ/pulse); $50J/cm^{2}$, 0.3W/10Hz (30mJ/pulse); $37J/cm^{2}$, 4. exposure time of 1 second. And the author applied the platinum coating on surfaces of cementum specimens, and evaluated the characteristics of ultrastructural change on surfaces of cementum using the scanning electron microscopy. In general the ultrastructural loss of cervical cementum irradiated under the same lasing condition of laser energy density occurred least in specimens of Group IV. And especially, the ultrastructural loss of cervical cementum irradiated under the laser energy density of $37J/cm^{2}$ almost did not occur in specimens of Group IV. Therefore, it is considered that the pulsed Nd:YAG laser should be applied with the lasing conditions of unidirectional moving mode of fiber in contact to cementum surfaces under speed of 3mm-4mm/sec with air-spray and of laser energy density within $37J/cm^{2}$ as an adjunctive modality of periodontal therapy of root planing without irreversible structural deterioration of cervical cementum.

• Journal of dental hygiene science
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• v.14 no.4
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• pp.589-596
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• 2014

This study was designed to investigate the using status and awareness of pit and fissure sealant, and how it affects on secondary caries when performed on above of initial caries. After classifying 446 occlusal surface into four groups, performed pit and fissure sealant, induced artificial caries, used DIAGNOdent (Kavo) to measure degree of secondary caries. Also, distributed a questionnaire on dental clinic in metropolitan area to find out using status and awareness of pit and fissure sealant, the following results were obtained. 1) On inspection and percussion, Group 4 corresponding to the enamel caries showed the highest secondary caries after sealant and was statistically significant difference in the order of initial group, stained group, sound group (p<0.05). 2) Inspection showed the highest percentage on tooth fissure caries diagnostic methods before sealant. 3) 56.6% didn't know about DIAGNOdent, 91.6% didn't have it. 4) In clinically, the most cause of secondary caries after sealant was a broken sealant, making caries on the downward. Based on the results of above study, degree of caries under sealant could affect on secondary caries, needs publicity about the use and necessity of objective fluorescence device.