• Journal of the korean academy of Pediatric Dentistry
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• v.35 no.1
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• pp.39-46
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• 2008

The purpose of this study was to assess the cariogenic potential of infant confectionaries. In vitro, as compaired with 10% sucrose solution and whole bovine milk. Buffering capability were determined by amount of 0.1N lactic acid consumed to titrate the 50ml specimen solutions to pH 4.0. The pH of the specimen solution inoculated by streptococcus mutans was measured by pH meter and the surface microhardness tester, before and after 48 hours incubation. The buffering capacity of infant confectionaries was higher than that of sucrose solution and lower than that of milk, and there were significant difference between infant confectionaries(p<0.05). The pH of infant confectionaries after 48 hours incubation was similar to 10% sucrose solution, and there were significant difference between infant confectionaries and milk(p<0.05). The microhardness change of primary tooth enamel of infant confectionaries group after 48 hours incubation was similar to that of 10% sucrose solution, and there were significant difference between infant confectionaries and milk(p<0.05). In conclusion, infant confectionaries seemed to have the ability to cause dental caries in primary teeth, and there were significant differences of cariogenic potential among infant confectionaries. Cooperative efforts of dentistry and manufacturers to reduce the cariogenic potential of infant confectionaries would be necessary to prevent the early childhood caries in children.

• The Journal of Korean Academy of Prosthodontics
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• v.42 no.5
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• pp.514-523
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• 2004

Statement of problem: All-ceramic restorations have been advocated for superior esthetics. Various post and core systems have been used to improve the strength of damaged teeth, but it is unclear whether they affect the final shade of finished all-ceramic restorations. Purpose: The influence of different types of post and core systems on light transmission through all-ceramic crowns was assessed by spectrophotometric analysis. Also the masking effect of different thickness of ceramic ingot was evaluated. Material and Methods : Forty-five sample disks (15mm in diameter) at several thickness(1.0, 1.5, 2.0mm) and value(shade 100, 200, 300) were made in heat pressed ceramic(IPS-Empress). Background specimens simulating gold-alloy cast posts(Type III casting gold alloy), metal posts(Ni-Cr casting alloy) and ceramic posts(CosmoPost) were fabrica-ted. Resin composite(Z250, A3 shade) was used as a tooth substrate reference. For each combination, the change in color was measured with a spectrophotometer. Readings were performed for 2 conditions (1) ability of ceramic to mask the core in relation to its thickness(1.0, 1.5, or 2.0mm) ; (2) influence of post and core types on the final color of the ceramic. Data were recorded according to the CIE $L^*a^*b^*$ systems and color difference($\Delta$E) was calculated. Results: 100 shade ingot: when ceramic thickness was 1.0mm, $\Delta$E value for ceramic post larger than 1 but $\Delta$E value for metal and gold post was larger than 2. For ceramic thickness of 1.5mm, only $\Delta$E value for metal was larger than 2, and the other samples' $\Delta$E value was smaller than 2. For ceramic thickness of 2.0mm, $\Delta$E values for all specimens was smaller than 2. 200 shade ingot: when ceramic thickness was 1.0mm, $\Delta$E value for ceramic post was smaller than 1 but $\Delta$E value for metal and gold post was larger than 2. For ceramic thickness of 1.5 mm, only the $\Delta$E value for metal was larger than 2, and the other samples' $\Delta$E value was smaller than 2. For ceramic thickness of 2.0mm, $\Delta$E values for all specimens was smaller than 1. 300 shade ingot: when ceramic thickness was 1.0mm, only $\Delta$E value for metal was larger than 2 and the other samples' $\Delta$E value was smaller than 2. For ceramic thickness of 1.5mm, $\Delta$E values for all specimens was smaller than 1. For ceramic thickness of 2.0mm, $\Delta$E values for all specimens was smaller than 1. Conclusion: The final esthetic result of the IPS-Empress glass-ceramic restoration was not affected by the presence of different core materials when the thickness was more than 2.0 mm. When ceramic thickness decreases to 1.5mm, it is advised to take the substrate aspects into consideration. If the ceramic thickness is less than 1.0mm, using the tooth color matched substrate is strongly recommended.

• The Journal of Korean Academy of Prosthodontics
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• v.48 no.2
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• pp.111-121
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• 2010

Purpose: This 3D-FEA study was performed to investigate the influence of marginal bone loss pattern around the implant to the stress distribution. Material and methods: From the right second premolar to the right second molar of the mandible was modeled according to the CT data of a dentate patient. Teeth were removed and an implant ($\Phi\;4.0{\times}10.0mm$) was placed in the first molar area. Twelve bone models were created; Studied bone loss conditions were horizontal bone loss and vertical bone loss, assumed bone loss patterns during biologic width formation, and pathologic vertical bone loss with or without cortification. Axial, buccolingual, and oblique force was applied independently to the center of the implant crown. The Maximum von Mises stress value and stress contour was observed and von Mises stresses at the measuring points were recorded. Results: The stress distribution patterns were similar in the non-resorption and horizontal resorption models, but differed from those in the vertical resorption models. Models assuming biologic width formation showed altered stress distribution, and weak bone to implant at the implant neck area seams accelerates stress generation. In case of vertical bone resorption, contact of cortical bone to the implant may positively affect the stress distribution.

• The Journal of Korean Academy of Prosthodontics
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• v.46 no.5
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• pp.443-454
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• 2008

Statement of problem: A clinically successful color match is one of the important factor to get an esthetic dental restoration. Dental shade guides are commonly used to evaluate tooth color in restorative procedure. But numerous reports have indicated that common shade guides do not provide sufficient spectral coverage of the natural tooth colors. To address issues associated with the shade guide, distinct avenues have been pursued objective spectrophotometric / colorimetric assessment. Purpose: This study compared the accuracy of tooth color selection of spectrophotometer with that of human visual determination. Three main factors were investigated, namely, the effect of light, the individual variation and the experience of the observer. Material and methods: At the first experiment, on ten patients, one operator independently selected the best matching shade to the unrestored maxillary central incisor, using a Vita Classical Shade Guide in the morning, at noon and in the afternoon. The same teeth were measured by means of a reflectance spectrophotometer. At the second experiment, on ten patients, ten operators (5 experts, 5 novices) selected and measured by the same method above at noon. At the third experiment, the results of the second experiment were divided into two groups, expert and novice, and analyzed. Results: 1. There was significant difference between visual and spectrophotometric assessment (mean ${\Delta}E$ values) in experiment 1, 2, 3 (P < .05). 2. There was no significant difference between experts and novices group, when comparing with each visual and spectrophotometric assessment (mean ${\Delta}E$ values). Conclusion: Spectrophotometer could be used to analyze the shade of natural tooth objectively. Thereby, this method offers the potential tominimize considerably the need for corrections or even remakesafter intraoral try-in of restoration. Furthermore, to achieve its advantage, both the shade-matching environment and communication between dentist and technician should be optimized with use of visual and instrumental shade-matching systems.

• The Journal of Korean Academy of Prosthodontics
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• v.51 no.1
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• pp.20-26
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• 2013

Purpose: The purpose of this study was to evaluate the bond strengths between the latest CAD/CAM ceramic inlay and various resin cements which are used primarily for esthetic restoration. Materials and methods: Cylindrical ceramic blocks(Height: 5 mm, diameter: 3 mm) were fabricated by using Cerec3 and bonded on the dentin of the ninety extracted caries-free molars using three different kinds of resin cement(Unicem$^{(R)}$, Biscem$^{(R)}$, and Variolink II$^{(R)}$) according to the manufacturer's instructions. Ninety specimens were divided into 3 groups according to three different kinds of resin cement. Half of each group were conducted thermocycling under the conditions of the $5-55^{\circ}C$, 5,000 cycle but the other half of them weren't. All specimens were kept in normal saline $37^{\circ}C$, for 24 hours before measuring the bond strength. The shear bond strength was measured by Universal testing machine with a cross head speed of 0.5 mm/min. The results were analyzed statistically by t-test and one-way ANOVA. Results: Unicem$^{(R)}$ group showed the highest shear bond strength despite a slight decline by thermocycling. The shear bond strength of Unicem$^{(R)}$ group and ValiolinkII$^{(R)}$ group were significantly influenced by thermocycling, whereas Biscem$^{(R)}$ group was not influenced (P<.05). There were no significant differences in the bond strength between the three groups without thermocycling, but there was significant differences between Unicem$^{(R)}$ group and Valiolink II$^{(R)}$ group with thermocycling(P<.05). Conclusion: It has been shown to be clinically effective when the self-adhesive resin cements Unicem$^{(R)}$ and Biscem$^{(R)}$ were used instead of the etch-and-rinse resin cement Valiolink II$^{(R)}$ during the bonding of CAD/CAM ceramic inlay restorations with teeth.

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.3
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• pp.512-521
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• 2001

Recently. the reintroduction of air-abrasion technology in dentistry has added a new potential method of pretreating teeth prior to placing sealants. The purpose of this in vitro study was to investigate microleakages of several pit and fissure sealants following various surface pre-treatment methods to the enamel, because there was a question concerning the validity of claim that this method was better than the conventional acid etching. Permanent molars were divided randomly into nine groups and treated accordingly: acid etching(group 1, 4, 7), air-abrasion(group 2, 5, 8), acid etching after air-abrasion(group 3, 6, 9). Then the authors placed and cured the three kinds of sealants(group $1\sim3$: Teethmate-F, group $4\sim6$: Ultraseal XT plus, group $7\sim9$: Denseal) according to the manufacturer's order. They were observed to determine the degree of microleakage. And these specimens were separated from the corresponding enamels and examined by Scanning Electron Microscope. The following results were obtained: 1. In comparing microleakage among tooth surface treatment methods, air-abrasion group(group 2, 5, 8) showed the greatest microleakage, while combination(air-abrasion + acid etching) group showed the least (p<0.05). However, no significant differences were found between group 7 and 9. 2. The mean microleakages were ranked as follows(p<0.05): In acid etching groups, group 7> group 4> group 1. In air-abrasive groups, group 8>groups 5> group 2. In combination groups, group 9>group 3> group 6. However, no significant differences were found between group 4 and 7 between group 2 and 5 and between group 3 and 6. 3. SEM showed that comparably longer resin tags were distributed regularly in acid etching groups and that shorter ones irregularly in air-abrasion groups. It also showed that these two kinds of tags were distributed simultaneously in combination groups.

• Journal of the korean academy of Pediatric Dentistry
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• v.29 no.4
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• pp.632-640
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• 2002

The objective of the study was to apply the vibration technique to reduce the viscosity of bonding adhesives and thereby compare the bond strength and resin penetration into dentinal tubules achieved with those gained using the conventional technique. Eighty-eight noncarious extracted human permanent molar teeth were sectioned to remove the coronal enamel and were embedded in 1-inch PVC pipe with acrylic resin. The occlusal surfaces were placed so that the tooth and the embedding medium were at the same level to form one flat surface, and the samples were subsequently polished with silicon carbide abrasive papers. The samples were randomly assigned to 4 groups(n=22). On Group 1 and 2, Single Bond(3M-ESPE, St. Paul, USA) was used, and on Group 3 and 4, One-Step(Bisco Inc., Schaumburg, USA) was used, and each was applied according to its manufacturer's instructions. For Group 2 and Group 4, vibration was applied with ultrasonic scaler for 10 seconds, and the adhesive was light-cured for 10 seconds. Resin composite was condensed on to the prepared surface in two increments using a mold kit(Ultradent Products Inc., USA) and each was light-cured for 40 seconds. After 24 hours in tap water at room temperature the specimens were thermocycled, and shear bond strengths were measured with a universal testing machine(Instron 4465, Canton, USA). To investigate infiltration patterns of the adhesive materials, the surface of specimen was examined with scanning electron microscope. The results were as follows. 1. The shear bond strengths of vibration groups(Group 2, Group 4) were significantly greater than those of the non-vibration groups(Group 1, Group 3)(p<0.05). 2. The shear bond strengths of Single Bond and One-Step were not significantly different (p>0.05). 3. The vibration groups showed greater number of resin tags in tubules and lateral branches under SEM.

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.3
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• pp.504-511
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• 2001

Preventive resin restoration, extended concept of occlusal pit and fissure sealing, is procedure composed of as follows. Cavity preparation is limited to areas of initial caries The cavity is then restored with composite resin, while other sound pits and fissures are sealed with pit and fissure sealant. If pit and assure sealant with which microrestoration is possible is used, it may be of great benefit to both patient and operator in case of difficult-to-control children s treatment. However study on preventive resin restoration using this kind of materials have been scarce. The purpose of this study was to compare the microleakage of four different modes of preventive resin restoration. Restoration using only composite resin was compared together Fifty-five bicuspids were prepared with small class I cavity preparation on the occlusal surface, divided into the following groups and restored accordingly. Group 1 : Cavity was restored with Z-100 composite resin Group 2 : Cavity was restored with Z-100 composite resin. Pits and fissures were then sealed with Teethmate F-1 Group 3 : Cavity was restored with Z-100 composite resin Pits and fissures were then sealed with Ultraseal XT-plus Group 4 : Cavity and pits and fissures were restored with Ultraseal XT-plus altogrether Group 5 : Cavity was restored with Ultraseal XT-plus. Pits and fissures were then sealed with the same material. After restoration, the samples were thermocycled 500 times between $5^{\circ}C$ and $55^{\circ}C$ with a dwell time of 30 seconds. After thermocycling, the samples were dipped into 1% methylene blue solution for 24 hours, then rinsed with tap water. The teeth were then embedded in resin and cut buccolingually along the tooth axis and observed with a stereomicroscope to determine the degree of microleakage. The results were as follows : 1. Group 4 showed the greatest microleakage, while group 3, showed the least. The mean microleakage decreased in the following order:4>1>5>2>3. 2. There was no stastically significant difference between group 1 and group 5(p>0.05). However, group 1 showed significantly greater microleakage compared to group 2 and 3(p<0.05) Group 1 showed significantly less microleakage compared to group 4(p<0.05). 3. Group 2 showed no statistically significant difference compared to group 3(p>0.05). However group 2 showed significantly less microleakage compared to group 4 and 5(p<0.05) 4. Group 3 showed significantly less microleakage compared to group 4 and 5(p<0.05). 5. Group 5 showed significantly less microleakage than group 4(p<0.05).

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.3
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• pp.345-354
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• 2001

The purpose of this study was to make public oral health plan more effective and the improvement of the hospital management system for better clinical dental practice. Distribution and trends were examined in all patients who had been examined and diagnosed at Department of Pedodontics, Dental Hospital, Chosun University over 10 year-period from 1990 to 1999 Results were as follows, 1. The number of patients per year was increasing trend after 1996 and higher visiting rate in male(55.9%) than in female(44.1%). 2. Age distribution had shown $3\sim4$ year-old cup being the largest (23.4%) and each percentage of $5\sim6,\;7\sim8,\;0\sim2,\;9\sim10,\;11\sim12,\;13\sim14,\;above\sim15$ year-old group was 19.9%, 17.7%, 14.6%, 12.6%, 8.0%, 3.3%. 0.5%. 3. Geographic distribution showed a majority of patients in Kwang-Ju (83.0%). Group in the suburbs of Kwang-Ju(Jang-Sung group) was 5.4%. 4. Dental caries showed the highest percentage(40.5%) in chief complaints and percentage of oral exam, orthodontic problem, oral pain, trauma, supernumerary teeth, swelling was 13.9% 12.6%, 8.8%, 7.4%, 5.5%, 4.9%. 5. In all patients with traumatic problem, crown fracture showed the highest percentage(41.4%) and percentage of subluxation was 19.4%. 6. Majority(78.7%) of patients were not refered, and percentage of patients refered from local clinic was 20.5%. 7. Patients who had periodic check-up comprised 19.6%, and percentage of after 3, 6, 9, 12, 18, 24month was 36.7%, 22.2%, 13.5%, 11.3%, 5.4%, 11.0%.

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.3
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• pp.464-470
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• 2001

The purpose of this study was to evaluate the tensile strength of light-cured restorative posterior resin-based composites. Five commercially available light-cured composites(Denfil : DF, P60 : PS, Unifil S : US, Z100 : ZH, Z250 : ZT) were used. Rectangular tension test specimens were fabricated in a teflon mold giving 5mm in gauge length and 2mm in thickness. Specimens were subjected to the 5,000 thermal cycles between $5^{\circ}C$ and $55^{\circ}C$ and the immersion time in each bath was 15 second per cycle. Tensile testing was carried out with Instron at a crosshead speed of 0.5mm/min and fractured surface were observed with scanning electron microscope. The obtained results were summarized as follows; 1. The tensile strength of PS was highest. PS was significantly higher than DF, US and ZH(p<0.05) but in the case of ZT was similar to PS(p>0.05). 2. The tensile strength DF was lowest. DF was significantly lower than PS, US, ZH and ZT(p<0.05). 3. The tensile strength of US and ZH were significantly lower than PS and ZT(p<0.05). but were significantly higher than DF(p<0.05). The tensile strength of US and ZH were similar(p>0.05).