• Restorative Dentistry and Endodontics
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• v.40 no.2
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• pp.104-112
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• 2015

Objectives: This study was performed to investigate the effects of different intracanal medicaments on chemical structure and microhardness of dentin. Materials and Methods: Fifty human dentin discs were obtained from intact third molars and randomly assigned into two control groups and three treatment groups. The first control group received no treatment. The second control group (no medicament group) was irrigated with sodium hypochlorite (NaOCl), stored in humid environment for four weeks and then irrigated with ethylenediaminetetraacetic acid (EDTA). The three treatment groups were irrigated with NaOCl, treated for four weeks with either 1 g/mL triple antibiotic paste (TAP), 1 mg/mL methylcellulose-based triple antibiotic paste (DTAP), or calcium hydroxide [$Ca(OH)_2$] and finally irrigated with EDTA. After treatment, one half of each dentin disc was subjected to Vickers microhardness (n = 10 per group) and the other half was used to evaluate the chemical structure (phosphate/amide I ratio) of treated dentin utilizing attenuated total reflection Fourier transform infrared spectroscopy (n = 5 per group). One-way ANOVA followed by Fisher's least significant difference were used for statistical analyses. Results: Dentin discs treated with different intracanal medicaments and those treated with NaOCl + EDTA showed significant reduction in microhardness (p < 0.0001) and phosphate/amide I ratio (p < 0.05) compared to no treatment control dentin. Furthermore, dentin discs treated with TAP had significantly lower microhardness (p < 0.0001) and phosphate/amide I ratio (p < 0.0001) compared to all other groups. Conclusions: The use of DTAP or $Ca(OH)_2$ medicaments during endodontic regeneration may cause significantly less microhardness reduction and superficial demineralization of dentin compared to the use of TAP.

• Journal of the korean academy of Pediatric Dentistry
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• v.24 no.4
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• pp.719-726
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• 1997

The aim of this study was to evaluate the in vitro effects of exposure to acidic beverages on microhardness of enamel and dentin. Thirty enamel specimens and thirty dentin specimens were obtained from extracted bovine maxillay incisiors. Enamel and dentin specimens were divided into three groups and treated with acidic beverages as follows; Group 1 : cola(pH 2.52), Group 2 : plain soda water(pH 2.93) and Group 3 : orange juice(pH 3.75). Erosive treatment was performed by storing each specimens for 5 min in 50ml solution of cola, soda water and orange juice. Average microhardness values(VHN) were determined before and after erosive treatment. All beverages produced significant loss of microhardness of enamel and dentin. Microhardness of enamel was reduced in the following order: Group 1 : $42.71{\pm}4.36(%)$, Group 2 : $37.09{\pm}6.25(%)$, Group 3 : $35.46{\pm}4.98(%)$. Microhardness of dentin was reduced in the following order: Group 1 : $17.14{\pm}3.42(%)$, Group 2 : $13.89{\pm}3.18(%)$, Group 3 : $13.82{\pm}3.50(%)$. The differences between group 1 and group 2, 3 were statistically significant(p< 0.05).

• Restorative Dentistry and Endodontics
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• v.29 no.1
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• pp.36-43
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• 2004

The purpose of this study was to compare the microhardness and the fluoride content of enamel and dentin around fluoride- or non fluoride-containing restorations. Forty extracted human teeth were used and prepared cervical cavities on proximal surface. Experimental teeth were divided into five groups . Group 1 : Prime & Bond NT and Z100, Group 2 Prime & Bond NT and F2000, Group 3 : Scotchbond Multi-purpose and Z100, Group 4 : Scothcbond Multi-purpose and F2000, Group 5 : Fuji II LC. The cavities were filled with dentin adhesives and restorative materials. After each tooth was bisected, one half was tested microharaness and the other half was analyzed the fluoride at the enamel and dentin by an EPMA-WDX device. The results were as follows; 1. There was no statistical difference among the microhardness of enamel surface in all group. 2. The microhardness at dentin of $100{\;}\mu\textrm{m}$ point in Group 2 and $20{\;}\mu\textrm{m}$ point in Grocup 4 was lower than that of normal dentin (p>0.05). 3. There was no statistical difference among the fluoride content of enamel surface in all group. 4. The fluoride content at the dentin of $30{\;}\mu\textrm{m}$ point in Group 2 and 5 were higher than those at $100{\;}\mu\textrm{m}{\;}and{\;}200{\;}\mu\textrm{m}$ point in Group 2 and normal dentin (p<0.05). 5. At the dentin of $30{\;}\mu\textrm{m}$ point, Group 2 showed higher fluoride content than Group 1 and 3, and Group 5 showed higher fluoride content than other groups.

• Restorative Dentistry and Endodontics
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• v.41 no.1
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• pp.12-21
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• 2016

Objectives: To evaluate the effects of three acids on the microhardness of set mineral trioxide aggregate (MTA) and root dentin, and cytotoxicity on murine macrophage. Materials and Methods: OrthoMTA (BioMTA) was mixed and packed into the human root dentin blocks of 1.5 mm diameter and 5 mm height. Four groups, each of ten roots, were exposed to 10% citric acid (CA), 5% glycolic acid (GA), 17% ethylenediaminetetraacetic acid (EDTA), and saline for five minutes after setting of the OrthoMTA. Vickers surface microhardness of set MTA and dentin was measured before and after exposure to solutions, and compared between groups using one-way ANOVA with Tukey test. The microhardness value of each group was analyzed using student t test. Acid-treated OrthoMTA and dentin was examined by scanning electron microscope (SEM). Cell viability of tested solutions was assessed using WST-8 assay and murine macrophage. Results: Three test solutions reduced microhardness of dentin. 17% EDTA demonstrated severe dentinal erosion, significantly reduced the dentinal microhardness compared to 10% CA (p = 0.034) or 5% GA (p = 0.006). 10% CA or 5% GA significantly reduced the surface microhardness of set MTA compared to 17% EDTA and saline (p < 0.001). Acid-treated OrthoMTA demonstrated microporous structure with destruction of globular crystal. EDTA exhibited significantly more cellular toxicity than the other acidic solutions at diluted concentrations (0.2, 0.5, 1.0%). Conclusions: Tested acidic solutions reduced microhardness of root dentin. Five minute's application of 10% CA and 5% GA significantly reduced the microhardness of set OrthoMTA with lower cellular cytotoxicity compared to 17% EDTA.

• Journal of Korean Dental Science
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• v.17 no.1
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• pp.36-44
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• 2024

Purpose: This study investigated the effect of dentin bonding agent acidity on surface microhardness of MTA. Materials and Methods: Forty cylindrical molds (3 mm×5 mm) were prepared, and three dentin bonding agents with different acidities: Adper Single Bond 2 (ASB), Single Bond Universal (SBU), and Clearfil SE bond 2 (CSE) were applied to the inner surface of the molds (n=10). No bonding agent was applied in the control group. MTA was mixed and inserted into the molds and sealed with a wet cotton pellet for 4 days. After setting, the Vickers microhardness (HV) test was done at 200, 400, 600 ㎛ from the inner surface of the mold. One-way ANOVA was conducted for all samples. A P-value of less than .05 was considered significant. Tukey HSD test was performed for post-hoc analysis. Results: The mean HV values and standard deviations were 67.02±11.38 (Con), 48.76±11.33 (ASB), 43.78±11.19 (CSE), 37.84±9.36 (SBU), respectively. The difference between the control group and the experimental groups was statistically significant (P<0.001). The difference between ASB and SBU was statistically significant (P<0.001), while the difference between SBU and CSE was not. There were no statistically significant differences between the various points from the inner surface of the mold within each group (P>0.05). Conclusion: Results of the current study indicate that use of dentin bonding agents with MTA can reduce the surface microhardness of MTA. Moreover, there is a direct relationship between the acidity of dentin bonding agents and the surface microhardness of MTA.

• Restorative Dentistry and Endodontics
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• v.29 no.1
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• pp.58-67
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• 2004

The objectives of this study was to evaluate current visible light curing units regarding microhardness and microleakage. Fourty samples of composite resin(Z-250, 3M) were cured by different light curing units (Flipo, LOKKI; Credi II, 3M; XL 3000, 3M: Optilux 500, Demetron) in acrylic blocks. Microhardness was measured using a calibrated Vickers indenter on both top and bottom surfaces after 24 hours of storage in air at room temperature. Class V cavities were prepared on buccal and lingual surfaces of fourty extracted human molars. Each margin was on enamel and dentin/cementum. Composite resin(Z-250, 3M) was filled in cavities and cured by four different light curing units (Flipo, LOKKl; Credi II, 3M; XL 3000, 3M: Optilux 500, Demetron). The results of this syudy were as follows: Microhardness 1. Flipo showed low microhardness compared to Optilux 500, Credi II significantly in upper surface. Flipo didn't show a significant difference compared to XL 3000. 2. The microhardness resulting from curing with Flipo was lower than that of others on lower surfaces. Microleakage 1. Dentin margin showed significantly high dye penetration rate than enamel margin in all groups(p<0.05). 2. No significant differences were found on both enamel and dentin margin regarding curing units.

• Journal of the korean academy of Pediatric Dentistry
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• v.40 no.3
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• pp.177-184
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• 2013

Calcium hydroxide mixture medicaments can nearly be considered to be the ideal primary tooth filling material. However, long-term application of calcium hydroxide combinations as an intra canal medicament softens dentin. The aim of this study was to evaluate the effect of calcium hydroxide on the microhardness of root dentin of primary tooth. For the study, 60 extractedprimary incisors were divided into 3 groups (no medicament, calcium hydroxide/iodorform mixture, and calcium hydroxide/distilled water mixture). After the cleansing and shaping of canals, calcium hydroxide medicaments were applied and stored for different periods of time (1, 7, 30, 90 days). The root was horizontally sectioned into 2 mm thick specimens and the microhardness was measured using Vickers microhardness tester. The results were as follows : Root dentin microhardness of primary teeth decreased with long term exposure to calcium hydroxide medicaments according to the experimental period and showed statistically significance (p < 0.05). Root dentin microhardness of primary tooth filled with calcium hydroxide mixed with distilled water showed more decrease than filled with Vitapex and showed statistically significance (p < 0.05). Root dentin microhardness of a control group without exposure to calcium hydroxide decreased according to the experimental period and showed statistically significance (p < 0.05).

• Restorative Dentistry and Endodontics
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• v.2 no.1
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• pp.38-49
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• 1976

Central and lateral incisors of 20, 40 and 60 age groups were bisected pararelly to long axis and middle portion of mesio-distal of teeth. And author measured the hardness of various areas in enamel and dentin with vickers hardness tester. Measured levels were divided into the labio-middle portion, middle portion of incisal edge and linguo-middle portion in enamel and dentin of all age groups. The results were as follows; 1) Total average hardness of enamel for 20, 40 and 60 age groups were respectively Hv. 366.5${\pm}$5.75, Hv. 372.9${\pm}$8.16 and Hv. 389.8${\pm}$10.27. 2) Total average hardness of dentin for 20, 40 and 60 age groups were respectively Hv. 51.0${\pm}$2.14, Hv. 54.0${\pm}$1.87 and Hv. 55.3${\pm}$2.23. 3) Total microhardness values in enamel and dentin of 60 age group was highered than 20 and 40 age groups. 4) The hardness values of enamel and dentin in all age groups were detected lower value on the middle portion of incisal edge than the labio-middle portion and linguo-middle portion. 5) Microhardness values of enamel was highered gradually from the dentinoenamel junction to the outer surface and it lowered at the outermost surface in all age groups. The microhardness values of dentin were the highest values at 600${\mu}$ from dentino-enamel junction and the lowest values at near the pulp chamber in all age groups.

• Journal of the korean academy of Pediatric Dentistry
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• v.23 no.4
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• pp.954-967
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• 1996

Laser application to modify healthy permanent dentin to improve microhardness and caries resistence has been previously reported but the physical modification and ablation thresholds of carious and sclerotic dentin has yet to be identified. This study determined the energy density required by modify (physical modification threshold, PMT) and remove (ablation threshold, AT) infected carious, affected and selerotic dentin compared to healthy permanent dentin. $1{\pm}0.25mm$ thick dentin sections(n=272) from extracted human teeth were used. Smear layer was removed 0.5M EDTA for 2 minutes. Utilizing three pulsed fiberopitc delivered contact lasers with different emission wavelengths($1.06{\mu}m$=Nd : YAG, $2.10{\mu}m$=Ho : YAG and $2.94{\mu}mEr$ : YAG). The energy density($J/cm^2$) was incrementally increased and the resulting tissue interaction classified on a scale from 0-6. A minimum of 5 repetitions/energy density were completed. Light microscopy(10-25X) was used to verify the physical modification(scale=3) and ablation thresholds(scale=4) of the various forms of dentin and the data were analyzed by logistic regression at the 95 % confidence interval. PMT and AT by the laser and the dentin types were: PMT and AT was lower in infected dentin than in sound dentin for all lasers. PMT and AT induced by Nd : YAG>Ho : YAG>Er : YAG for all forms of dentin. Microhardness was increased in sound dentin at PMT. Morphology of crater examined by light microscopy showed Nd : YAG was safe and effective for removing carious dentin and Er: YAG was effective for removing sound dentin. The PMT and AT for YAG lasers are different as a function of dentin type which may be utilized for selective modification and removal of dentin.

• Restorative Dentistry and Endodontics
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• v.16 no.2
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• pp.126-142
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• 1991

The purpose of this study was to evaluate the effect of various dentin surface treatments on shear bond strength, microhardness and fracture mode before and after thermocycling. Recently extracted 75 human molars were used. The teeth were sagittal sectioned faciolingually to obtain 150 specimens. They were randomly divided into six groups. Mesial and distal dentinal surfaces of specimens were exposed by grinding and treated respectively with GC-DENTIN CONDITIONER. 10-3 solution of 4-Meta, Cleansar and Primer of GLUMA, Scotchprep of Scotchbond 2, DENTIN CONDITIONER and PRIMER A, B of ALL BOND according to the manufacturers directions. Specimens of one group were not treated. Adhesive agent of Scotchbond 2, were applied and cured on the treated dentin surfaces. After P-50 were cured on them, specimens were stored in 31c water for 24 hours before shear bond strength measurement Shear bond strength was measured in 10 specimens of each group. 10 specimens of each group were thermocycled in $20^{\circ}C$, $60^{\circ}C$,$20^{\circ}C$, $4^{\circ}C$, $20^{\circ}C$ water in order, for 30 seconds respectively, 100 times a day for 7 days. After thermocycling shear bond strength was measured. Microhardness was checked on treated dentin surface and fractured dentin surface in 10 specimens respectievly. Francture modes were observed with SEM The following results were obtained. 1. Before thermocycling. shear bond strengths in the specimens treated with DENTIN CONDITIONER and PRIMER A, B of ALL BOND were significantly higher than those in other specimens(P<0.01). 2. After thermocycling. shear bond strengths in the specimens treated with Cleanser and Primer of GLUMA, Scotchprep of Scotchbond 2 and DENTIN CONDITIONER and PRIMER A, B of AIL BOND were significantly higher than those in specimens not: treated, treated with GC-DENTIN CONDITIONER and 10-3 solution of 4-Meta(P<0.01). Shear bond strengths in the specimens treated with GC-DENTIN CONDITIONER and PRIMER A, B of ALL BOND were significantly higher than those in other specimens except those treated with Scotchprep of Srotchbond 2(P<0.01). 3. Shear bond strengths after thermocycling were reduced in the specimens not treated, treated with GC-DENTIN CONDITIONER and 10-3 solution of 4-Meta and were increased in the specimens treated with Cleanser and Primer of GLUMA, Scotchprep of Scotchbond 2, without significance, compared with those before thermocycling. In the specimens treated with DENTIN CONDITIONER and PRIMER A, B of ALL BOND, shear bond strengths after thermocycling were significantly increased, compared with those before thermocycling(P<0.01). 4. Microhardnesses in the fractured surfaces after shear bond strength measurement were significantly increased in the specimens treated with 10-3 solution of 4-Meta and significantly decreased in the specimens treated with DENTIN CONDITIONER and PRIMER A, B of ALL BOND, compared with those in the treated dentin surfaces(P<0.01). 5. In the specimens treated with Cleanser and Primer of GLUMA, Scotchprep of Scotchbond 2 and DENTIN CONDITIONER and PRIMER A, B of ALL BOND, cohesive fracture modes were observed more than adhesive fracture modes.