• The Journal of Korean Academy of Prosthodontics
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• v.54 no.2
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• pp.146-151
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• 2016

In patients with fully edentulous maxilla, fabrication of implant-supported overdenture can be a viable treatment option, when a minimum of six implants were strategically placed. Among several attachment systems used for implant-supported overdentures, milled-bars prevent rotational movement of denture, thus showing great stability, and have the advantage of splinting multiple implants with each other. In this case report, a milled-bar supported overdenture was fabricated for a patient suffering from condition of fully edentulous maxilla with severe ridge resorption in the anterior residual ridge. Seven implants composed of three different systems were effectively utilized by CAD/CAM customized abutment and cement-retained milled bar.

• The Journal of Advanced Prosthodontics
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• v.3 no.3
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• pp.126-131
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• 2011

PURPOSE. The aim of this in vitro study was to examine the curing efficiency of various resin-based materials polymerized through ceramic restorations with 3 different thicknesses. Curing efficiency was evaluated by determining the surface microhardness (VHN) of the resin specimens. MATERIALS AND METHODS. Four kinds of resin materials were used. Z350 (3M ESPE $Filtek^{TM}$ Z350: A2 Shade), Z250 (3M ESPE $Filtek^{TM}$ Z250: A2 Shade) and $Variolink^{(R)}$ II (VL: Ivoclar vivadent, base: transparent) either with or without a self-curing catalyst (VLC: Ivoclar vivadent, catalyst: low viscosity/transparent) were filled into the silicone mold (10 mm diameter, 1 mm thick). They were cured through ceramic discs (IPS e.max Press MO-0 ingot ivoclar vivadent, 10 mm diameter, 0.5, 1 and 2 mm thicknesses) by LED light-curing units for 20 and 40 seconds. Vicker's microhardness numbers (VHNs) were measured on the bottom surfaces by a microhardness tester. Data were analyzed using a 3-way analysis of variance (ANOVA) at a significance level of 0.05. RESULTS. The thickness of ceramic disc increased, the VHNs of all four resin types were decreased (P<.05). The mean VHN values of the resins light cured for 40 seconds were significantly higher than that of LED for 20 seconds in all four resin materials (P<.05). VLC showed significantly higher VHN values than VL regardless of other conditions (P<.05). Z350 and Z250 showed higher values than VL or VLC (P<.01). CONCLUSION. Thinner ceramic disc with increased curing time resulted higher VHN values of all resin materials. The use of a catalyst produced a greater hardness with all polymerization methods. Restorative resin materials (Z350, Z250) showed higher VHN values than resin cement materials (VL, VLC).

• Journal of Korean Society for Quality Management
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• v.45 no.4
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• pp.995-1002
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• 2017

Purpose: The purpose of this study was to evaluate the color stability of composite resins used for splinting teeth by comparing a self-cure resin cement (Superbond C&B, SB), a flowable composite resin (G-aenial Universal Flo A2, GU), and a composite resin exclusively used for splinting teeth (G-Fix, GF) before and after aging in NaOCl. Methods: Resin samples were fabricated to a size of 2 mm thickness and 8.5 mm diameter and light-cured with an LED light curing unit (G-Light, n = 12). Immediately after fabrication, CIE L*a*b* values of the resin samples were measured with a spectrophotometer (CM-5) as baseline. Then, the resin samples were immersed in 5% NaOCl at $60^{\circ}C$ and the color was measured after 23 hours every day for 4 days. Data were analyzed with one-way ANOVA followed by Duncan post hoc test (p<0.05), and color differences (${\Delta}E$) of resin samples before and after NaOCl aging were also calculated. Results: For SB, there were no changes in L* and a* values but changes were observed in b* values. For GU, there were no changes in L* and b* values but in a* values. For GF, changes were observed in L*, a*, and b* values. All resin samples showed highest ${\Delta}E$ between baseline and the 1st day of NaOCl immersion. ${\Delta}E$ of SB, GU, and GF was 4.6 - 5.8, 4.9 - 7.9, and 9.9 - 16.9, respectively. GF showed highest color change during NaOCl aging. Conclusion: The results of this color quality evaluation showed that the composite resin exclusively used for splinting teeth might be more vulnerable to color change during intraoral service.

• The Journal of Advanced Prosthodontics
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• v.6 no.6
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• pp.444-450
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• 2014

PURPOSE. To compare the accuracy of marginal and internal adaptation of zirconia (Zr) copings fabricated on anatomic (A), semi-anatomic (SA) and non-anatomic (NA) occlusal surface preparations. MATERIALS AND METHODS. 45 extracted bicuspid teeth were prepared for receiving zirconia crowns, with different occlusal preparation designs A=15, SA=15 & NA=15. The Zr copings were fabricated by using CAD4DENT, CAD/CAM. The copings were adjusted, cemented and were cross sectioned centrally from buccal cusp tip to lingual cusp tip into mesial and distal halves. The copings were examined under electron microscope at ${\times}200$ magnification and the measurements were recorded at 9 predetermined areas in micrometers. RESULTS. Overall mean gap values for the three groups was found to be $155.93{\pm}33.98{\mu}m$ with Anatomical Occlusal preparation design having the least gap value of $139.23{\pm}30.85{\mu}m$ showing the best adaptation among the groups. Post Hoc Tukey's test showed a statistically significant difference (P=.007) between the means of gap for A & NA preparation designs. Measurements recorded at 9 predetermined points showed variations for the three groups. CONCLUSION. Anatomical occlusal preparation designs resulted in better marginal and internal adaptation of Zr copings. There is a considerable variation between the measured marginal and internal gap values for the Zr copings fabricated by the (CAD4DENT-CAD/CAM). This variation may be associated with the lack of standardization of the preparation of teeth, computerized designing of the coping for each tooth, cement used, uniform pressure application during the cementation of the copings, sectioning of the copings and the microscopic measurements.

• The Journal of Advanced Prosthodontics
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• v.6 no.6
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• pp.491-497
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• 2014

PURPOSE. This study evaluated the influence of abutment materials on the stability of the implant-abutment joint in internal conical connection type implant systems. MATERIALS AND METHODS. Internal conical connection type implants, cement-retained abutments, and tungsten carbide-coated abutment screws were used. The abutments were fabricated with commercially pure grade 3 titanium (group T3), commercially pure grade 4 titanium (group T4), or Ti-6Al-4V (group TA) (n=5, each). In order to assess the amount of settlement after abutment fixation, a 30-Ncm tightening torque was applied, then the change in length before and after tightening the abutment screw was measured, and the preload exerted was recorded. The compressive bending strength was measured under the ISO14801 conditions. In order to determine whether there were significant changes in settlement, preload, and compressive bending strength before and after abutment fixation depending on abutment materials, one-way ANOVA and Tukey's HSD post-hoc test was performed. RESULTS. Group TA exhibited the smallest mean change in the combined length of the implant and abutment before and after fixation, and no difference was observed between groups T3 and T4 (P>.05). Group TA exhibited the highest preload and compressive bending strength values, followed by T4, then T3 (P<.001). CONCLUSION. The abutment material can influence the stability of the interface in internal conical connection type implant systems. The strength of the abutment material was inversely correlated with settlement, and positively correlated with compressive bending strength. Preload was inversely proportional to the frictional coefficient of the abutment material.

• Journal of Dental Rehabilitation and Applied Science
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• v.23 no.4
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• pp.269-281
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• 2007

Fluoric acid etching is an essential procedure in cementation of reinforced ceramics to tooth surface. But there have been few studies about the changes of surface structure and flexural strength of IPS $Empress^{(R)}$ 2 ceramic according to the etching time. The objectives of this study were to examine the surface structure changes and the difference in biaxial flexural strength of IPS $Empress^{(R)}$ 2 ceramic according to various etching times. Sixty one disk-shaped specimens of IPS $Empress^{(R)}$ 2 ceramic($14mm{\times}1.2mm$) were fabricated for the biaxial flexural strength test and SEM analysis according to the manufacturer's recommendations. Sixty specimens were divided into 6 groups(n=10) according to the time of HF acid etching(0, 20, 180 and 300s)and silane/resin cement application. Each disk was loaded using a piston-on-3 ball biaxial configuration in a universal testing machine. The failure loads(N) were recorded, and the biaxial flexural strength for each disk was calculated. A one-way analysis of variance and independent t-test on transformed fracture strength data were used to determine significant differences between groups. The groups of no cementation showed a trend toward progressive weakening with increasing the etching time. However, this was not statistically significant at p=0.05 level. The groups of resin cementation exhibited no apparent trend in their mean strength values. SEM photomicrographs showed very different results of etching. Within the conditions of this study, alteration of surface topography by acid etching does not have a deleterious effect on the biaxial flexural strength of IPS $Empress^{(R)}$ 2 ceramic.

• Journal of Dental Rehabilitation and Applied Science
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• v.19 no.3
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• pp.207-217
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• 2003

The purpose of this study was to compare the fracture strength of the IPS Empress ceramic crown according to the incisal depth (1.5mm, 2.0mm, 2.5mm) and axial inclination ($4^{\circ}$, $8^{\circ}$, $12^{\circ}$) of the lower central ncisor. After 10 metal dies were made for each group, the IPS Empress ceramic crowns were fabricated and each crown was cemented on each metal die with resin cement. The cemented crowns mounted on the testing jig were inclined 30 degrees and a universal testing machine was used to measure the fracture strength. The results of this study were as follows : The fracture strength of the ceramic crown with 2.0mm depth and $12^{\circ}$ inclination was the highest (648 N). Crowns of 1.5mm depth and $4^{\circ}$ inclination had the lowest strength (482 N). There were no significant differences of the fracture strength by axial inclination in same incisal depth group. The fracture mode of the crowns was similar. Most of fracture lines began at the loading area and extended through proximal surface perpendicular to the margin irrespective of incisal depth. There had correlation between fracture strength and fractured surface area.

• The Journal of Korean Academy of Prosthodontics
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• v.30 no.3
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• pp.379-400
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• 1992

The purpose of this study was to analyze the magnitude and distribution of stress using a photoelastic model from the mandibular distal extension removable partial dentures with the mesial or distal placement of the occlusal rest and the mesial or distal connection in the back-action clasp with the five various designs of the back-action clasp, that is, the mesial connection and the distal rest, the distal connection and mesial rest, the mesial connection and mesial rest, the distal connection and the mesial and distal rest, and the mesial connection, and the mesial and distal rest. A photoelastic model was made of the epoxy resin(PC-1) and the hardner(PLH-1) with the acrylic resin teeth used and was coated with the plastic cement-1 at the lingual surface of the model and then five kinds of the removable partial dentures on the photoelastic model were set. A unilateral vertical load of 12.5 kg was applied on the central fossa of the first molar with the use of specially designed loading device and the pattern and distribution of the stress of the photoelastic model under each condition was analyzed by the reflective circular polariscope. The following results were obtained. 1. In the back-action clasp with the mesial connection and mesial rest of the case 3, the effect of the stress distribution was the most favorable. 2. In the back-action clasp with the mesial and distal rest, of the case 4 and 5, the stress distribution was more greatly showed in the terminal abutment. 3. Generally, the stress distribution was more favarable in the mesial connection than in the distal connection. 4. In the back-action clasp with the mesial connection of the case 1, 3 and 5, the stress distribution was the most favorable in the mesial rest.

• Restorative Dentistry and Endodontics
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• v.40 no.3
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• pp.209-215
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• 2015

Objectives: The aim of this study was to evaluate the fluoride release of conventional glass ionomer cements (GICs) and resin-modified GICs. Materials and Methods: The cements were grouped as follows: G1 (Vidrion R, SS White), G2 (Vitro Fil, DFL), G3 (Vitro Molar, DFL), G4 (Bioglass R, Biodinamica), and G5 (Ketac Fil, 3M ESPE), as conventional GICs, and G6 (Vitremer, 3M ESPE), G7 (Vitro Fil LC, DFL), and G8 (Resiglass, Biodinamica) as resin-modified GICs. Six specimens (8.60 mm in diameter; 1.65 mm in thickness) of each material were prepared using a stainless steel mold. The specimens were immersed in a demineralizing solution (pH 4.3) for 6 hr and a remineralizing solution (pH 7.0) for 18 hr a day. The fluoride ions were measured for 15 days. Analysis of variance (ANOVA) and Tukey's test with 5% significance were applied. Results: The highest amounts of fluoride release were found during the first 24 hr for all cements, decreasing abruptly on day 2, and reaching gradually decreasing levels on day 7. Based on these results, the decreasing scale of fluoride release was as follows: G2 > G3 > G8 = G4 = G7 > G6 = G1 > G5 (p < 0.05). Conclusions: There were wide variations among the materials in terms of the cumulative amount of fluoride ion released, and the amount of fluoride release could not be attributed to the category of cement, that is, conventional GICs or resin-modified GICs.

• Restorative Dentistry and Endodontics
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• v.45 no.2
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• pp.11.1-11.9
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• 2020

Objectives: This study compared the flow and filling of several retrograde filling materials using new different test models. Materials and Methods: Glass plates were manufactured with a central cavity and 4 grooves in the horizontal and vertical directions. Grooves with the dimensions used in the previous study (1 × 1 × 2 mm; length, width, and height respectively) were compared with grooves measuring 1 × 1 × 1 and 1 × 2 × 1 mm. Biodentine, intermediate restorative material (IRM), and mineral trioxide aggregate (MTA) were evaluated. Each material was placed in the central cavity, and then another glass plate and a metal weight were placed over the cement. The glass plate/material set was scanned using micro-computed tomography. Flow was calculated by linear measurements in the grooves. Central filling was calculated in the central cavity (㎣) and lateral filling was measured up to 2 mm from the central cavity. Results: Biodentine presented the least flow and better filling than IRM when evaluated in the 1 × 1 × 2 model. In a comparison of the test models, MTA had the most flow in the 1 × 1 × 2 model. All materials had lower lateral filling when the 1 × 1 × 2 model was used. Conclusions: Flow and filling were affected by the size of the test models. Higher grooves and materials with greater flow resulted in lower filling capacity. The test model measuring 1 × 1 × 2 mm showed a better ability to differentiate among the materials.