No abstract available.

No abstract available.

No abstract available.
Dental Porcelain* ; Fatigue* ; Fractures, Stress*

No abstract available.
Dental Enamel* ; Lasers, Solid-State*

No abstract available.
Composite Resins* ; Dental Porcelain*

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.
Adhesives ; Crowns* ; Dental Instruments ; Dentin ; Glass Ionomer Cements ; Humans ; Polycarboxylate Cement ; Resin Cements ; Tooth Preparation ; Tooth* ; Zinc Phosphate Cement

No abstract available.

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.
Aluminum Oxide ; Ceramics* ; Crowns* ; Dental Porcelain ; Fatigue* ; Glass ; Water

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.
Ceramics* ; Glass ; Hydrofluoric Acid* ; Lithium* ; Resin Cements*

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.
Alloys ; Aluminum ; Animals ; Connective Tissue ; Hot Temperature ; Hydrogen-Ion Concentration ; Mice ; Stainless Steel ; Titanium* ; Tooth, Artificial ; Water