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: 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).
Color Vision Defects ; Dental Technicians ; General Practitioners ; Humans ; Masks ; Perception* ; Students, Dental