No abstract available.

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

No abstract available.

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

No abstract available.
Composite Resins* ; Dental Porcelain*

No abstract available.

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

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*

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

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.
Ceramics ; Crowns* ; Esthetics ; Hot Temperature ; Masks ; Reading ; Tooth