Effects of hydrofluoric acid concentration and etching time on the shear bond strength between lithium disilicate ceramic and resin cement / 대한치과보철학회지

PURPOSE: The objective of this study was to evaluate the effects of hydrofluoric acid concentration & etching time on the shear bond strength between IPS Empress 2 ceramic and resin cement. MATERIAL AND METHODS: Thirty three rectangular shape ceramic specimens(20x12x5mm size, IPS Empress 2 core materials) were used for this study. The ceramic specimens divided into ten experimental groups with three specimens in each group and were etched with hydrofluoric acid(4%, 9%) according to different etching times(30s, 60s, 90s, 120s, 180s). Etched surfaces of ceramic specimens were bonded with resin cement(Rely X Unicem) using acrylic glass tube. All cemented specimens were tested under shear loading until fracture on universal testing machine at a crosshead speed of 0.5mm/min and the maximum load at fracture(kg) was recorded. Collected shear bond strength data were analyzed with one way ANOVA and Duncan tests. All etched ceramic surfaces were examined morphologically using SEM(scanning electron microscopy). RESULTS: Shear bond strength of etching group(35.89~68.01 MPa) had four to seven times greater than no-etching group(9.53+/-2.29 MPa). The ceramic specimen etched with 4% hydrofluoric acid for 60s showed the maximum shear bond strength(68.01+/-11.78 MPa). Ceramic surface etched with 4% hydrofluoric acid for 60s showed most retentive surface texture. CONCLUSION: It is considered that 60s etching with 4% hydrofluoric acid is optimal etching methods for IPS Empress 2 ceramic bonding.

Shade perception ability among different dental personnel / 대한치과보철학회지

Statement of problem: Many factors influence shade determination in clinical practice and shade matching is highly affected by the viewing conditions. Purpose: This study investigated the differences in shade perception among distinct groups of dental personnel (10 prosthodontists, 10 general practitioners, 10 last-year dental students and 10 dental technicians). Material and method: Four groups of dental personnel were investigated. They were tested to eliminate color blindness. To compare shade selection ability, they were asked to match four test tabs of shades A3, B2, C2 and D4 (VITAPAN. Classical shade guide. The identification codes of the shade tabs were masked to prevent shade memory.) against another full set of VITAPAN. Classical shade guide under similar lighting conditions. Shade selections were randomly repeated five times every week and then the repeatability between dental personnel was evaluated. To compare value perception ability, they were asked to arrange randomly selected five test tabs (B1, A2, D2, C3, A4) in descending order from the brightest to the darkest. To compare hue determination ability, they were asked to divide selected eight test tabs (A2, A3, B2, B3, C2, C3, D2, D3) into four groups by manufacturer as follows: Group A-Reddish brown, Group B-Reddish yellow, Group C-Grey, Group D-Reddish grey. Results and conclusion: The obtained results were as follows: 1. For the value perception ability and hue determination ability, there was no significant difference among 4 groups: prosthodontists, general practitioners, dental students, dental technicians(P>.05). 2. For shade selection ability, the prosthodontists and dental technicians were significantly higher than dental students(P<.05). 3. The repeatability of selected shade in the dental technicians was significantly higher than that of general practitioners and dental students(P<.05). 4. The prosthodontists and dental technicians had significantly higher selection ability than dental students for shade B2(P<.05).

Effect of chemical treatment on the bioactivity of titanium / 대한치과보철학회지

STATEMENT OF PROBLEM: Titanium is widely used as an implant material for artificial teeth. Also, studies on surface treatment to form a fine passive film on the surface of commercial titanium or its alloys and improving bioactivity with bone have been carried out. However, there is insufficient data about the biocompatibility of the implant materials in the body. PURPOSE: The purpose of this study was to examine whether the precipitation of apatite on titanium metal is affected by surface modification. MATERIALS AND METHODS: Specimens chemically washed for 2 minute in a 1:1:1.5 (in vol%) mixture of 48% HF, 60% HNO3 and distilled water. Specimens were then chemically treated with a solution containing 97% H2SO4 and 30% H2O2 at 40 degrees C for 1 hour, and subsequently heat-treated at 400 degrees C for 1 hour. All specimens were immersed in the HBSS with pH 7.4 at 36.5 degrees C for 15 days, and the surface were examined with TF-XRD, SEM, EDX and XPS. Also, commercial purity Ti specimens with and without surface treatment were implanted in the abdominal connective tissue of mice for 4 weeks. Conventional aluminium and stainless steel 316L were also implanted for comparison. RESULTS AND CONCLUSIONS: The results obtained were summarized as follows. 1. An amorphous titania gel layer was formed on the titanium surface after the titanium specimen was treated with a H2SO4 and H2O2 solution. The average roughness was 2.175 micrometer after chemical surface treatment. 2. The amorphous titania was subsequently transformed into anatase by heat treatment at 400 degree C for 1 hour. 3. The average thickness of the fibrous capsule surrounding the specimens implanted in the connective tissue was 46.98 micrometer in chemically-treated Ti, and 52.20, 168.65 and 100.95 micrometer, respectively in commercial pure Ti, aluminum and stainless steel 316L without any treatment.

The influence of porcelain layer thickness and color on the final shade of ceramic restorations / 대한치과보철학회지

STATEMENT OF PROBLEM: Ceramic restorations should be made of porcelain layers of different opacity, shade, and thickness in order to provide a natural appearance. Lithium disilicate glassceramic system has superior color reproducibility, because it uses the ceramic ingot which is similar to teeth shade and uses the staining technique and layering technique. However, staining technique has a fault of discoloration. Also, porcelain is divided core and dentin layer, it is not enough to study about the influence of porcelain layer thickness and shade on the shade of ceramic restorations. PURPOSE: The purpose of this study was to evaluate the influence of porcelain layer thickness and color on the final shade of ceramic restorations. MATERIALS AND METHOD: The CIE L*a*b*(CIELAB) values of 72 assembled specimens, each consisting of 3 discs (enamel porcelain 0.2 mm/dentin porcelain - 1.2, 0.9, 0.7, 0.5 or 0.3 mm/ceramic core - 0.3, 0.5, 0.7, 0.9 or 1.2 mm, diameter is 1.0 mm) were evaluated with a spectrophotometer (Model Chromaview 300, Spectron Tech Co, Korea) for the shade A1, A2, A3 and A4. Distilled water (refractive index: 1.7) was used to attain optical contact between the layers. White, white gray, and white brown backgrounds were used to assess the influence of the background on the final shade. And the mean color difference value(delta E) was calculated. RESULTS AND CONCLUSION: The results obtained from this study were as follows. 1. There was a significant correlation between the thickness ratio of the ceramic core/dentin porcelain system and L*, a* and b* values when the total thickness of specimen combination was smaller than 1.4 mm( p<0.05). 2. The specimen which the ceramic core thickness was more than 0.7 mm had the best masking effect against background colors. 3. The mean color difference value(delta E) is smaller than 2 (delta E<2) when the ceramic core thickness was larger than 0.7 mm and the total thickness of specimen was more than 1.4 mm.

Effect of etching time on shear bond strength of resin cements to reinforced all-ceramic crowns / 대한치과보철학회지

PURPOSE: The purpose of this study was to evaluate the effects of etching time on shear bond strength of four resin cements to IPS Empress 2 ceramic. MATERIAL AND METHODS: Forty rectangular shape ceramic specimens (10x15x3.5mm size) were used for this study. The ceramic specimens divided into four groups and were etched with 10% hydrofluoric acid for 0, 10, 30, 60, 180, 300, 420, 600, and 900 seconds respectively. Etched surfaces of ceramic specimens were coated with ceramic adhesive system and bonded with four resin cement (Variolink II, Panavia F, Panavia 21, Super-Bond C & B) using acrylic glass tube. All cemented specimens were tested under shear loading untill fracture on universal testing machine at a crosshead speed 1mm/min; the maximum load at fracture (kg) was recored. Shear bond strengh data were analyzed with oneway analysis of variance and Tukey HSD tests (p<.05). Etched ceramic surfaces (0-, 60-, 300-, and 600-seconds etching period) and fracture surfaces after shear testing were examined mophologically using scanning electron microscopy. RESULTS: Ceramic surface treatment with 10% hydrofluoric acid improved the bond strength of three resin cement except for Super-Bond C&B cement. Variolink II (41.0+/-2.4 MPa) resin cement at 300-seconds etching time showed ststistically higher shear bond strength than the other resin cements (Panavia F: 28.3+/-2.3 MPa, Panavia 21: 21.5+/-2.2 MPa, Super-Bond C&B: 16.7+/-1.6 MPa). Ceramic surface etched with 10% hydrofluoric acid for 300 seconds showed more retentive surface texture. CONCLUSION: Within the limitation of this study, Variolink II resin cement are suitable for cementation of Empress 2 all-ceramic restorations and etching with 10% hydrofluoric acid for 180 to 300 seconds is required to enhance the bond strength.

Influence of several posts and IPS-Empress ingot thickness on the final shade of all-ceramic crowns / 대한치과보철학회지

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(IPSEmpress). Background specimens simulating gold-alloy cast posts(Type III casting gold alloy), metal posts(Ni-Cr casting alloy) and ceramic posts(CosmoPost) were fabricated. 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, 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.

Effect on the Color Stability of Stained Porcelain due to Tooth Brushing / 대한치과보철학회지

This study is going to compare the degree of color change which occurs in the following two cases of the factors which cause the color change of extra-staining,one is during glazing by the dental technician,the other is tooth brush abrasion which makes the biggest influence on color change. To compare the degree of color change before and after glazing,a sample was made with vintage incisal porcelain No.59 OPAL(Shofu Inc,Japan),after that it was painted with three colors of porcelain stainers,then the degree of color was measured with a spectrophometer(Model Chromaview 300,Spectoron Tech Co.Korea)after it had been treated with firing only and glazing after firing. 40,000-cycle and 80,000-cycle of tooth brush abrasion test were carried out in order to simulate the brushing effect of 4 years and 8 years by using the abrasion tester.The colors were mesured before the test,and after the 40,000-cycle and 80,000-cycle operations and the surfaces were examined by SEM. The results of this study were as follows ; 1.The color change before and after glazing was not great enough to have a clinical significance but the orange color was changed more significantly statistically than the blue and light brown(P<0.05). 2.In the case of the color change of stained porcelain by tooth brushing,carrying out staining and glazing with two-times firings resulted in statically less color change than one firing only(P<0.05). 3.In the case of the difference in the stainer's color,the orange color which has higher chroma was statically more sensitive than the blue color(P<0.05). 4.In the case of the color change after the 80,000-cycle abrasion,all showed color change when there was one firing and the orange stainer showed some color change with clinical significance when firings were done two times.

ANALYSIS OF OPTICAL TRANSMISSION CHARATERISTICS BY VISIBLE LIGHT INTO SHADE GUIDES / 대한치과보철학회지

The purpose of this study was the evaluation of spectral transmission of the commercial three shade guides and the relationship of hue, value, and chroma according to the transmission rate. The spectral transmittance of three shade guides - Vita Lumin Shade Guide, Vintage and Unibond Shade Guide, and Vitapan 3D-Master Shade Guide - were measured. For direct transmission measurements, each shade tabs were placed at the entrance port of the 1mm diameter intergrating sphere. The intensity of the light source passing through the shade tabs to the right angle was continuously recorded for wavelength from 400 to 700 nm. A transmission spectrum and digital data were obtained for each measurement and they were evaluated using Microcal Origin program. The obtained results of this study were as follows 1. In Vita Lumin Shade Guide, sum of the transmission rate of the shade tabs at the wavelength 400-700nm was decreased in agreement with the arrangement order at each A, B, C, D group, except D4 shade tab. However, there were no relationships between the transmission rate of the shade tabs and the value-oriented. 2. In Vintage and Unibond Shade Guide, sum of the total transmission rate of the shade tabs was decreased in agreement with the arrangement order at each A, B, C, D group. When all shade tabs arranged in value-oriented, transmission rate was accord with the order, except D4 shade tab. 3. When shade tabs of the Vitapan 3D-Master Shade Guide have the same value and hue, sum of their total transmission rate decreased in accordance with the chroma-oriented. When the shade tabs have the same value and chroma, there were no differences from the order of the transmission rate to the various hue type. However, in the "R" tabs of reddish hue type, the transmission rate increased at the long wavelength range area. In conclusion, we need the quantitative analyzing instruments in transmission determination. Vitapan 3D-Master Shade Guide covers the tooth color space taking into account the parameters of the systematic value, chroma, hue oriented, and the transmission rate relatively accorded with that sequence.

INFLUENCE OF TOOTH SURFACE ROUGHNESS AND TYPE OF CEMENT ON RETENTION OF COMPLETE CAST CROWNS / 대한치과보철학회지

Bond strength of luting cements to dentin is a critical consideration for success of complete cast crowns. This study was performed to evaluate the relationship between surface characteristics of teeth prepared for complete cast crowns and retention of cemented restorations. Eighty artificial crowns were cast for standardized complete crown tooth preparations accomplished with the use of a special device on recently extracted human teeth. Coarse diamond(#102R, Shofu) and superfine finishing diamond(#SF102R, Shofu) burs of similar shape were used. Crowns in each group were randomly subdivided into four subgroups of 10 for luting cements selected for this study: zinc phosphate cement (FLECK'S), polycarboxylate cement (Poly-F), reinforced glass ionomer cement (Fuji PLUS), and adhesive resin cement (Panavia 21). Retention was evaluated by measuring the tensile load required to dislodge the artificial crown from tooth preparations with an Instron testing machine, and analysed by one-way ANOVA and Student's t-test. The obtained results were as follows ; 1. When tooth preparation was done with coarse diamond bur, retentive force was diminished in order of Panavia 21, Fuji PLUS, FLECK'S, and Poly-F. Retentive forces showed the significant difference between Fuji PLUS group and FLECK'S group(p<0.001). 2. When tooth preparation was done with superfine diamond bur, retentive force was diminished in order of Fuji PLUS, Panavia 21, FLECK'S and Poly-F. Retentive forces showed the significant difference between Panavia 21 group and FLECK'S group(p<0.001). 3. Retentive force in coarse tooth surfaces was significantly higher than that in superfine tooth surface with all luting cements(p<0.001), and cement residues were almost retained with in the cast crown in all groups.

AN EVALUATION OF DYNAMIC FATIGUE CHARACTERISTICS OF DENTAL CERAMICS FOR ALL-CERAMIC CROWN / 대한치과보철학회지

This study was performed to evaluate the dynamic fatigue characteristics of the dental ceramics for all-ceramic crown. A feldspathic porcelain of VMK68, glass ceramic of IPS-Empress, and glass infiltrated alumina ceramic of In-Ceram were used. Disc specimens were prepared to the final dimensions of 12 mm in diameter and 1 mm in thickness. The biaxial flexure test was conducted using a ball-on-three-ball method. 240 specimens were tested in 37degrees C water by testing 20 samples at each of four loading rates:0.05, 0.2, 1, and 5mm/min. 60 specimens were tested in a moisture-free environment by testing 20 samples at 5mm/min. The inert strength of VMK68 was 80.25MPa, and the fatigue parameters were n=29.1, sfo=52.90MPa. The inert strength of IPS-Empress was 104.76MPa, and the fatigue parameters were n=32.46, sfo=67.52MPa. The inert strength of In-Ceram was 429.33MPa, and the fatigue parameters were n=31.46, sfo=258.36MPa. 10-year failure stresses of VMK68, IPS-Empress, and In-Ceram were 20.3MPa, 24.8MPa, and 93.6MPa, respectively. failure strength and fatigue life showed the highest value in In-Ceram, and then, IPS-Empress and VMK68.

EFFECTOF SOLDERING CONDITION ON THE TENSILE STRENGTH TITANIUM SOLDER JOINT WITH 14K GOLD SOLDER / 대한치과보철학회지

This study was performed to evaluate the tensile strength of solder joint in titanium and the wettability of 14K gold solder on titanium. Two pieces of titanium rod 30 mm in length and 3mm in diameter were butt-soldered with a 14K gold solder using the electric resistance heating under flux-argon atmosphere, the infrared heating under argon atmosphere, and the infrared heating under vacuum-argon atmosphere. A tensile test was performed at a crosshead speed of 0.5mm/min, and fractere surfaces were examined by SEM. To evaluate the wettability of 14K gold solder on titanium, titanium plates of a 17x17x1mm were polished with #80-#2000 emery papers, and the spreading areas of solder 10mg were measures by heating at 840 * for 60 seconds. The solder-matrix interface regions were etched by the solution of 10% KCN-10%(NH4)2S2O8, and analyzed by EPMA. The results obtained were summarized as follows: 1. The maximun tensile strength was obtained when the titanium surface was polished with #2000 emery paper and soldered using the electric resistance heating under fluxargon atmosphere. Soldering strengths showed the significant difference between the electric resistance heating and the infrared heating(p<0.05). 2. The fracture surfaces showed the aspect of brittle fracture, and the failure developed along the interfaces of solder-matrix reaction zone. 3. The EPMA data for the solder-matrix interface region revealed that the diffusion of Au and Cu occurred to the titanium matrix, and the reaction zone showed the higher contents of Au, Cu and Ti than others.

An experimental study on the fatigue fracture of laminate porcelain / 대한치과보철학회지

No abstract available.

The effects of porcelain primers on the bonding of composite resins to porcelain / 대한치과보철학회지

No abstract available.

A study on the correlationship between pantographic reproducibility index and patterns of mandibular movements using mandibular kinesiograph / 대한치과보철학회지

No abstract available.

A study on the metal surface treatment of resin bonded retainers / 대한치과보철학회지

No abstract available.

An experimental study on the residual stress and bond strength of ceramo-metal system / 대한치과보철학회지

No abstract available.

A study on the effect of pulsed Nd: YAG laser impacts to the enamel surface and bond strength with composite resin / 대한치과보철학회지

No abstract available.