• The Journal of Korean Academy of Prosthodontics
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• v.29 no.2
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• pp.85-101
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• 1991

The purpose of this study was to determine the optimum range of laser energy density to the enamel surface of permanent incisors when they are irradiated with the pulsed Nd : YAG laser, Laser impacts on each experimental group were made at energy density of $20\sim50J/cm^2$ by 20 pulses of the pulse width 1.2 msec. The author investigated the enamel surface with the sunning electron microscope(SEM) and the surface roughness tester, and measured the shear bond strength between electrolytically etched Ni-Cr-Be alloy casting and composite resin. The obtained results were as follows: 1. The surface roughness of enamel after laser irradiation showed the significant difference level from the energy density $40J/cm^2(P<0.05)$. 2. The mean shear bond strength of etched-metal resin-bonded specimens were $154.23{\pm}33.30kg/cm^2$ at unlased enamel surface and $195.72{\pm}29.56kg/cm^2$ at lased energy density $30J/cm^2$, and showed a significant difference(P<0.05). 8. SEM photographs showed the irregular microcracks and the structural changes of lased enamel surface. 4. SEM photographs of the fracture surface after testing the shear bond strength showed the aspect of interfacial fracture between bonding agent and composite resin at the metal sides.

• Journal of Korean society of Dental Hygiene
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• v.14 no.2
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• pp.281-286
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• 2014

Objectives : The aim of this study is to evaluate the surface changes of enamel specimen, tooth structure by toothpastes in child and adult. Methods : Experimental teeth were collected from extracted human primary teeth. 120 enamel specimens were prepared by cutting the teeth into $2{\times}3{\times}2mm$ blocks using diamond saw and the specimens were assigned to 3 groups. Group 1 was used as control with no treatment. Group 2 was treated with child toothpaste and Group 3 was treated with adult toothpaste on primary enamel surface for 3 minutes daily over 4 weeks. The specimens were immersed into individual container having artificial saliva and the artificial saliva was changed every day. The electron probe micro analyzer(EPMA) provided weight percent(wt%) of calcium(Ca) and phosphorous(P) on enamel surface. The morphology was analyzed by scanning electron microscopy(SEM). Data were analyzed by one-way analysis of variance(ANOVA) and Tukey's test post-hoc test using SPSS(Version 20, SPSS Inc., Chicago, USA). Level of significance was set at 0.05. Results : The surface changes of the primary teeth revealed a significant difference during 4 weeks. Calcium(Ca) and phosphorous(P) levels were found the weight percent difference and a rough enamel surface was seen on SEM after adult toothpaste application. Conclusions : The changes in Ca and P and the morphological surface were affected by the primary tooth treated with adult toothpaste. Enamel surface showed significant differences during 4 weeks.

• Restorative Dentistry and Endodontics
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• v.27 no.2
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• pp.175-182
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• 2002

Dental caries is a chronic disease that causes the destruction of tooth structure by the interaction of plaque bacteria, food debris, and saliva. There has been attempts to induce remineralization by supersaturating the Intra-oral environment around the surface enamel, where there is incipient caries. In this study, supersaturated remineralized solution "R" was applied to specimens with incipient enamel caries, and the quantitative analysis of remineralization was evaluated using microradiography. Thirty subjects volunteered to participate in this study. Removable appliances were constructed for the subjects, and the enamel specimen with incipient caries were embedded in the appliances. The subjects wore the intra-oral appliance for 15 days except while eating and sleeping. The removable appliance were soaked in supersaturated solution "R", saline, or Senstime$^{\circledR}$ to expose the specimen to those solutions three times a day, 5 minutes each time. After 15 days, microradiography was retaken to compare and evaluate remineralization The results were as the following: 1. The ratio of remineralized area to demineralized area was significantly higher in the supersaturated solution "R" and Senstime$^{\circledR}$ than in the saline (p<0.05) 2. Remineralization in the supersaturated buffer solution "R" occurred in the significantly deeper parts of the tooth. compared to the Senstime$^{\circledR}$ group containing high concentration or fluoride. (p<0.05) As in the above results, the remineralization effect of remineralized buffer solution "R" on incipient enamel caries has been proven. For clinical utilization, further studies on soft tissue reaction and the effect on dentin and cementum are necessary In conclusion compared to commercially available fluoride solution. remineralization solution“R”showed better remineralization effect on early enamel caries lesion, so it is considered as effecient solution for clinical application.

• Restorative Dentistry and Endodontics
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• v.39 no.3
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• pp.172-179
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• 2014

Objectives: This study aimed to assess the effect of 38% carbamide peroxide on the microleakage of class V cavities restored with either a silorane-based composite or two methacrylate-based composites. Materials and Methods: A total of 96 class V cavities were prepared on the buccal surface of extracted human teeth with both enamel and dentin margins and were randomly assigned into three groups of Filtek P90 (3M-ESPE) + P90 system adhesive (3M-ESPE)(group A), Filtek Z250 (3M-ESPE) + Adper Prompt L-Pop (3M-ESPE)(group B) and Filtek Z350XT (3M-ESPE) + Adper Prompt L-Pop (group C). Half of the teeth were randomly underwent bleaching (38% carbamide peroxide, Day White, Discus Dental, applying for 15 min, twice a day for 14 day) while the remaining half (control) were not bleached. Dye penetration was measured following immersion in basic fuchsine. Data were statistically analyzed using Kruskal-Wallis and Mann-Whitney U tests at a level of 0.05. Results: No significant differences were found between composites in the control groups in enamel (p = 0.171) or dentin (p = 0.094) margins. After bleaching, microleakage of Z250 (in enamel [p = 0.867] or dentin [p = 0.590] margins) and Z350 (in enamel [p = 0.445] or dentin [p = 0.591]margins) did not change significantly, but the microleakage of P90 significantly increased in both enamel (p = 0.042) and dentin (p = 0.002) margins. Conclusions: No significant differences were noted between the bleached and control subgroups of two methacrylate-based composites in enamel or dentin margins. Microleakage of silorane-based composite significantly increased after bleaching.

• Proceedings of the KACD Conference
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• 2008.05a
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• pp.224-234
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• 2008

The purpose of this study was to compare the normal and two times of application time of six self-etching primers applied to enamel using microshear bond strength (uSBS) test and the finding of scanning electronic microscope (SEM). Crown of sixty human molars were bisected mesiodistally and buccal and lingual enamel of crowns were partially exposed and polished with 600 grit SiC papers. They were divided into one of two equal groups subdivided into one of six equal groups (n = 10) by self-etching primer adhesives. After the same manufacture's adhesive resin and composites were bonded on the enamel surface of each group, the bonded specimens were subjected to uSBS testing and also observed under SEM. In conclusion, generally two times of primer application time increased the enamel uSBS, especially with the statistical increase of bond strength in adhesives involving high-pH primers.

• Restorative Dentistry and Endodontics
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• v.25 no.3
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• pp.459-473
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• 2000

Dental caries is the most common disease in the maxillofacial area. There are many factors contributing to its development, but complete understanding and prevention is not fully known. Since the structure of the coronal and root portion of the tooth is different, the remineralization and demineralization process is also known to be different. In this study, by using a partially saturated buffer solution, we created artificial enamel and dentin caries and evaluated mineral loss. A remineralization solution with four different degrees of saturation (degree of saturation ; group 1, 0.268, group 2, 0.309, group 3, 0.339, group 4, 0.390, PH 4.3, F-2ppm) was used on a demineralized specimen. The mineral precipitating quantity and depth was evaluated by using microradiography. Using an atomic force microscope (AFM), hydroxyapatite crystals of normal, demineralized, and remineralized enamel and dentin were evaluated. The results were as follows: 1. As the degree of saturation of the remineralizing solution increased, the mineral precipitation in the enamel was increased. In group 4, mineral precipitation was limited near the surface. 2. As the degree of saturation of the remineralizing solution increased, the mineral precipitation in the dentin was decreased and it occurred in a deeper portion. In group 4, however, mineral precipitation occurred on the surface and its quantity increased. 3. There was a statistically significant interaction between enamel and dentin mineral content changes on specimens treated with remineralization and demineralization solution (demineralization r=0.44, remineralization r=0.44, p<0.05). 4. Demineralized hydroxyapatite crystals showed central and peripheral dissolving and widening of intercrystal spaces under the AFM. 5. In dentin remineralization small crystal precipitation occurred between the large crystals. We conclude that by adjusting acidulated buffer solution's degree of saturation, we can control enamel and dentin remineralization. In addition, the AFM is highly useful in evaluating changes in remineralized and demineralized hydroxyapatite crystals.

• Restorative Dentistry and Endodontics
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• v.33 no.3
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• pp.224-234
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• 2008

The purpose of this study was to compare the normal and two times of application time of six self-etching primers applied to enamel using microshear bond strength (uSBS) test and the finding of scanning electronic microscope (SEM). Crown of sixty human molars were bisected mesiodistally and buccal and lingual enamel of crowns were partially exposed and polished with 600 grit SiC papers. They were divided into one of two equal groups subdivided into one of six equal groups (n = 10) by self-etching primer adhesives. After the same manufacture's adhesive resin and composites were bonded on the enamel surface of each group, the bonded specimens were subjected to uSBS testing and also observed under SEM. In conclusion, generally two times of primer application time increased the enamel uSBS, especially with the statistical increase of bond strength in adhesives involving high-pH primers.

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.4
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• pp.438-445
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• 2000

The ideal restorative material should mimic the properties of the tissues it replaces. Dental composite resins have been used widely as restorative materials due to its advantages such as excellent esthetics and ease of manipulation. But inadequate wear resistance has been a major factor limiting the use of composite restorative materials. Improved manufacturing techniques have allowed the development of hybrid composites, with a greater percentage volume filler loading, which have improved physical and mechanical properties. However they are lacking in the study of wear resistance. The purpose of this study was to evaluate the wear of human enamel against ceromer by the use of a pin-on-disk type wear testers. Discs of ceromer(Targis ; lvoclar Vivadent, Amherst. NY) and discs of type III gold alloy as a control were used f9r test specimens. Intact cusp of premolar and molar were used for enamel specimens. The wear of enamel was determined by weigh-ing the cusp before and after each test, and the weight converted to volumes by average densi-ty of enamel. Surface profilometer was used to quantify wear of the ceromer and gold specimens. Vicker's hardness tester was used to evaluate the surface hardness of test specimens. The SEM was used to evaluate the wear surfaces The results were as follows; 1. Ceromer produced less enamel wear than gold(p<0.05) 2. The wear volume of ceromer was greater than that of gold(p<0.01) 3. The hardess of ceromer was lower than that of gold, but there was no correlation between the hardness and wear of the ceromer and gold. 4. SEM analysis revealed that there were many voids and microcracks in the wear tract of ceromer In gold group, many minute V-shaped grooves were examined.

• Restorative Dentistry and Endodontics
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• v.29 no.3
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• pp.205-211
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• 2004

This study evaluated the microleakage and interfacial gap between enamel and composite resin under the dry and wet condition of the enamel surface. V shaped class 5 cavities were prepared on the occlusal portion of extracted human molars. Samples were divided into three groups：D group (air dry for 10-15s), BD group (blot dry with moist cotton pellet), and DR group (air dry for 10-15s and rewet with Aqua-Prep F for 20s), Cavities were filled using Aelitefil composite resin after applied One-Step. Microleakage was tested by 2% methylene blue dye solution and the data were statistically analysed by Kruskal-Wallis test and Mann-Whitney test. Also Enamel-resin interface was observed under SEM. Group BD showed statistically lower microleakage than group D (p < 0.05). but there was no statistically significant difference between group BD and DR (p > 0.05). At the enamel-resin interface, group D showed the gap of $2{\;}{\mu}m$ thickness, but group BD and DR showed close adaptation. In conclusion, the use of blot dry and rewetting agent (Aqua-Prep F) resulted in decreased microleakage and improved adhesion between enamel and resin when using One-Step.

• The korean journal of orthodontics
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• v.25 no.2 s.49
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• pp.223-233
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• 1995

The purpose of this study was to evaluate the effects of surface conditioning with $10\%$ polyacrylic acid, etching with $38\%$ phosphoric acid, and polishing with a slurry of pumice on shear bond strengths of light-cured glass ionomer cement, chemically cured glass ionomer cement, and a composite resin to enamel, and to observe the failure patterns of bracket bondings. Shear bond strengths of glass ionomer cements were compared with that of a composite resin. Metal brackets were bonded on the extracted human bicuspids after enamel surface treatments, and samples were immersed in the $37^{\circ}C$ distilled water bath, and shear bond strengths of glass ionomer cements and a composite resin were measured on the Instron machine after 24hrs passed, and the deboned samples were measured in respect of adhesive remnant index. Scanning electron micrographs were taken of enamel surfaces after various treatments. The data were evaluated and tested by ANOVA and Duncan's multiple range test, and those results were as follows. 1. Shear bond strength of light-cured glass ionomer cement showed statistically higher than that of chemically cured glass ionomer cement. 2. Shear bond strengths of light-cured and chemically cured glass ionomer cements to enamel treated with $10\%$ polyacrylic acid and $38\%$ phosphoric acid showed statistically higher than those with a slurry of pumice. 3. According to scanning electron micrographs, enamel surface conditioned with $10\%$ polyacrylic acid is slightly etched and cleaned, that etched with $38\%$ phosphoric acid is severely etched, and that polished with a slurry of pumice is irregulary scretched and not completely cleaned. 4. After debonding, light-cured glass ionomer cement to enamel treated with $10\%$ polyacrylic acid showed less residual materials on the enamel solace than composite resin to enamel etched with $38\%$ phosphoric acid. 5. There was no significant difference in the shear bond strength of light-cured glass ionomer cement to enamel treated with $10\%$ polyacrylic acid and that of composite resin to enamel etched with $38\%$ Phosphoric acid.