Ormocer has organic-inorganic compound polymers. One of advantages of ormocer is reduced polymerization shrinkage. The purpose of this study was to compare the amount of contraction shrinkage of composite resins and ormocers. Additionally, the time of each material when there is no further change of contraction shrinkage was analysed. Four brands of composite resins (P-60, Surefil, Z-250 and Denfil) and two brands of ormocers (Definite and Admira) were used. 20 seconds, 40 seconds and 60 seconds of curing times were given. Contraction shrinkage of them were measured using a linometer for 80 seconds. The effect of material and curing time to contraction shrinkage at the time of 80 seconds was analysed by two-way ANOVA. The effect of time to contraction shrinkage was analysed by one-way ANOVA, and the time when there was no further change of the contraction shrinkage was analysed. The results are as follows : 1. P-60, Definite, Z-250 and Denfil had no further change of contraction shrinkage from the time of 20 seconds, and Surefil and Admira had no further change of contraction shrinkage from the time of 10 seconds. 2. Statistical analysis revealed volumetric shrinkage varied among material (p<0.05). No significant difference of contraction shrinkage among different curing times was found, and there was no effect of interaction between materials and curing times to contraction shrinkage. 3. Definite and Admira showed the statistically same contraction shrinkage with those of Z-250 and P-60, which is higher than that of Surefil and lower than that of Denfil (p<0.05).
Composite Resins* ; Organically Modified Ceramics* ; Polymerization ; Polymers

The purpose of this study was to evaluate the color stability of light cured composite resins according to the resin matrices. Three kinds of resin matrices such as Bis-GMA (Venus® Diamond; VD), Silorane (FiltekTM P90; P90), and Ormocer (Admira; Ad) were selected. Each of them were used to prepare 30 specimens. The initial CIE L*a*b* values were measured by means of a Spectrophotometer (NF999, Nippon Denshoku, Japan). For accelerated aging process, the specimens were immersed in a circulating water bath with distilled water at 60℃. Spectrophotometric analyses were made after immersion of 8, 16, 24, 41 days and the color difference (ΔE*) was calculated. The L* value increased compared with initial L* value. VD had the greatest L* value change and Ad had the smallest L* value change (p<0.05). Ad had the greatest a* value change and VD had the smallest a* value change (p<0.05). The b* value of P90 increased steadily in positive value (+)(p<0.05). ΔE* of Ad had the smallest value and that of P90 had the greatest change with time. According to this study, the value of light cured composite resins was increased with water sorption and color of those changed into greenish and yellowish. And according to the evaluation of color stability, Ad with Ormocer as resin matrices had the best color stability with time in oral environment and P90 with Silorane as resin matrices had the lowest color stability with time. And VD had the greatest initial ΔE*.
Aging ; Baths ; Bisphenol A-Glycidyl Methacrylate ; Composite Resins ; Diamond ; Immersion ; Organically Modified Ceramics ; Silorane Resins ; Water

PURPOSE: The most common failure seen in restorations with a zirconia core is total or layered delamination of the ceramic veneer. In the present study, the shear bond strengths between veneering ceramics and colored zirconia oxide core materials were evaluated. MATERIALS AND METHODS: Zirconia discs (15 x 12 x 1.6 mm) were divided into 11 groups of 12 discs each. Groups were colored according to the Vita Classic scale: A3, B1, C4, D2, and D4. Each group was treated with the recommended shading time for 3 s, or with prolonged shading for 60 s, except for the control group. Samples were veneered with 3 mm thick and 3.5 mm in diameter translucent ceramic and subjected to shear test in a universal testing machine with a crosshead speed of 1 mm/min. One-way analysis of variance (ANOVA) and Tukey's HSD tests were used for comparisons of the groups having the same shading times. A paired t-test was used for groups of the same color (3 s/60 s). RESULTS: Among the 11 groups investigated C4 (3 s) had the highest bond strength with a value of 36.40 MPa, while A3 (3 s) showed the lowest bond strength with a value of 29.47 MPa. CONCLUSION: Coloring procedures can affect zirconia/ceramic bond strength. However, the results also showed that bond strengths of all the investigated groups were clinically acceptable.
Ceramics*

PURPOSE: The aim of this study was to compare the translucency of two different laminate ceramic veneers with and without glazing. MATERIALS AND METHODS: Ten millimeter side square-shaped specimens in 0.3 mm and 0.6 mm thick were fabricated for the following materials with and without glazing (n=80): A1 shade IPS e.maxPress (IEM) and Styleveneers (STV). The color coordinates (CIE L* a* b*) of the specimens were measured with a colorimeter. The Translucency parameter (TP) was calculated from the color difference of the material on a black versus a white background. For comparisons between materials and between the' not glazed'and' glazed'groups, unpaired t-test was used to analyze the data (P=.05). RESULTS: The TP (Mean +/- SD) of' not-glazed'and' glazed'group of IEM specimens at 0.3 mm thickness were 45.99 +/- 3.00 and 49.53 +/- 2.28 and the TP at 0.6 mm thickness were 32.82 +/- 2.59 and 43.02+/-0.98, respectively. Likewise, the TP of' not-glazed'and' glazed'group of STV specimens at 0.3 mm thickness were 47.03 +/- 3.65 and 50.95 +/- 3.05 and the TP at 0.6 mm thickness group were 34.48 +/- 1.28 and 43.39 +/- 1.20, respectively. As the glazing of ceramic veneer differed, the TP of each ceramic veneer showed statistically significant difference. But, the result between the products was not statistically different. CONCLUSION: Within the limitations of this study, we are concluded that the glazing process changed translucency of laminate ceramic veneers and the TP would not be affected by products.
Ceramics*

PURPOSE: This study aimed to evaluate the fit of zirconia ceramics before and after veneering, using 3 different veneering processes (layering, press-over, and CAD-on techniques). MATERIALS AND METHODS: Thirty standardized zirconia CAD/CAM frameworks were constructed and divided into three groups of 10 each. The first group was veneered using the traditional layering technique. Press-over and CAD-on techniques were used to veneer second and third groups. The marginal gap of specimens was measured before and after veneering process at 18 sites on the master die using a digital microscope. Paired t-test was used to evaluate mean marginal gap changes. One-way ANOVA and post hoc tests were also employed for comparison among 3 groups (alpha=.05). RESULTS: Marginal gap of 3 groups was increased after porcelain veneering. The mean marginal gap values after veneering in the layering group (63.06 microm) was higher than press-over (50.64 microm) and CAD-on (51.50 microm) veneered groups (P<.001). CONCLUSION: Three veneering methods altered the marginal fit of zirconia copings. Conventional layering technique increased the marginal gap of zirconia framework more than pressing and CAD-on techniques. All ceramic crowns made through three different veneering methods revealed clinically acceptable marginal fit.
Ceramics ; Crowns ; Dental Porcelain

The purpose of this study was to evaluate the shear bond strength and failure mode of ceramic brackets according to the surface treatment of porcelain. Sixty porcelain samples were randomly divided into six groups of ten samples. Then they were treated as follows: Group 1(silane only), Group 2(etching + silane), Group 3(stone + silane), Group 4 (sandblasting + silane), Group 5(stone + etching + silane), Group 6(sandblasting + etching + silane) After surface treatment of porcelain, sixty Transcend 6000 brackets were bonded to the prepared porcelain surface and they were stored in 37 degrees C saline for 24 hours. An Instron universal testing machine was used to test the shear bond strength of ceramic brackets to porcelain. After debonding, bases of ceramic brackets and porcelain surfaces were examined under scanning electron microscope(SEM) to determine failure mode. Statistical analysis of the data was carried out with one-way ANOVA and Duncan's multiple range test. The results were as follows: 1. The shear bond strength of surface-treated groups 2 to 6 was higher than that of only silane-treated group 1, and there was statistical significance. (P<0.05) 2. There was no significant difference among the groups 3 to 6. (P <0.05) 3. The shear bond strength of etching-surface treated group 2 was significantly lower than those of sandblasting-surface treated group 4, complex surface treated group 5 and group 6. 4. According to the scanning electromicroscopic images, the surface roughness of sandblasting-surface treated group 4 was less than those of the group 5 and 6, but there was no significant difference in the shear bond strength. (P >0.05) As a conclusion we can have a clinically adequate bond strength when an application of silane is done after the treatment of porcelain surface with more than one way to bond ceramic bracket on the porcelain. Also, it is considered that the sandblasting and application of silane is effective for the simplication and convenience of the treatment.
Ceramics* ; Dental Porcelain*

PURPOSE: Surface color is one of the main criteria to obtain an ideal esthetic. Many factors such as the type of the material, surface specifications, number of firings, firing temperature and thickness of the porcelain are all important to provide an unchanged surface color in dental ceramics. The aim of this study was to evaluate the color changes in dental ceramics according to the material type and glazing methods, during the multiple firings. MATERIALS AND METHODS: Three different types of dental ceramics (IPS Classical metal ceramic, Empress Esthetic and Empress 2 ceramics) were used in the study. Porcelains were evaluated under five main groups according to glaze and natural glaze methods. Color changes (DeltaE) and changes in color parameters (DeltaL, Deltaa, Deltab) were determined using colorimeter during the control, the first, third, fifth, and seventh firings. The statistical analysis of the results was performed using ANOVA and Tukey test. RESULTS: The color changes which occurred upon material-method-firing interaction were statistically significant (P<.05). DeltaE, DeltaL, Deltaa and Deltab values also demonstrated a negative trend. The MC-G group was less affected in terms of color changes compared to other groups. In all-ceramic specimens, the surface color was significantly affected by multiple firings. CONCLUSION: Firing detrimentally affected the structure of the porcelain surface and hence caused fading of the color and prominence of yellow and red characters. Compressible all-ceramics were remarkably affected by repeated firings due to their crystalline structure.
Ceramics* ; Crystallins ; Dental Porcelain ; Fires*

Titanium requires special ceramic system for veneering. Low fusing dental ceramics with coefficients of thermal expansion matching that of titanium have been developed. The purpose of this study was to determine the bond strengths between cast and noncast pure titanium and two commercial titanium porcelains, and to compare the results with a conventional nickel-chromium alloyceramic system. The bond strengths were determined using a 3-point flexure test. Three-point flexure specimens 25x3x0.5mm were prepared. After removal of alpha-case layer, they were veneered with 8x3x1mm of ceramics at the center of the bar. Specimens were tested in a universal testing machine. Within the limits of this study, the following conclusions were drawn: 1. The bond strengths between pure titanium and two commercial porcelains exceeded th lower limit of the bonding strength value in ISO 9693(25MPa). 2. There was no significant difference between cast and noncast titanium-porcelain bonds. 3. There was no significant difference between two commercial titanium porcelains. 4. The bond strengths of the titanium-porcelain systems ranged from 73% to 79% of that of the Ni-Cr-conventional porcelain system.
Alloys* ; Ceramics* ; Dental Porcelain ; Titanium*

This study evaluated the effect of dagassing on the ceramic bond strength of two Ni-Cr alloys under varying holding time at the upper limit temperature and atmospheric conditions. Metal specimens were divided into 5 groups for each alloy according to degassing conditions prior to porcelain application : no degassing, degassing under vacuum without hold, degassing under vacuum with hold for 5min. and 10 min. respectively at the upper limit temperature and degassing in air. Total number of metal ceramic specimens was eighty and each group had eight specimens : The ceramic bond strength was measured by four-point flexural test using Instron and the fractured surface was examined under SEM. The results obtained were as follows. 1. Degassing in air improved the ceramic bond strength of Ni-Cr alloys. 2. in degassing under vacuum, hold at the upper limit temperature was advantageous to the ceramic bonding of Ni-Cr alloys. 3. After ceramic metal bond test, metal surfaces were partially covered with the thin porcelain layer, and the cohesive failures in porcelain were predominant in groups showing higher ceramic bond strength.
Alloys* ; Ceramics* ; Dental Porcelain ; Vacuum

OBJECTIVETo evaluate the aesthetic outcomes of all-ceramic restorations by using four different porcelain materials on mimic-tetracycline pigmentation backgrounds.

METHODSThe translucency parameters (TP) of four different all-ceramic restorations (IPS e.max, Cercon, Lava, and Girrbach) were measured under white and black back grounds by using Datacolor 600, and the TP of each group (n = 8) was calculated. Five different mimic-tetracycline pigmentation teeth were printed with different colors by using a colorized printer as the prepared teeth backgrounds, under which the color parameters of each group were measured. The color differences with a standard 2M2 sample were calculated.

RESULTSThe TP values of the all-ceramic restorations were 15.67 +/- 0.58 for IPS e.max, 9.73 +/- 0.43 for Girrbach, 9.55 +/- 0.25 for Lava, and 7.56 +/- 0.43 for Cercon. The TP value of the IPS e.max group was significantly higher than those of the other three groups (P < 0.001). The deltaE of the IPS e.max group was 1.33 national bureau of standards (NBS) on the yellow background, and the deltaE of the Lava and Girrbach groups were 0.75 NBS to 1.47 NBS on the mimic-tetracycline pigmentation backgrounds of gray, dark gray, dark red, and light red.

CONCLUSIONThe IPS e.max group has favorable TP. IPS e.max shows better aesthetic effects than the others when restoring mimic-tetracycline pigmentation teeth (on yellow background). Lava and Girrbach show better aesthetic effects on mimic-tetracycline pigmentation teeth (on gray, dark gray, dark red, and light red backgrounds).