Background and Objectives: Porcelain restorations are often ground for recontouring and occlusal adjustments. This removes the surface glaze layer and causes flaws that can grow in wet environments due to stress corrosion cracking and decrease the strength of porcelain and subsequently the longevity and clinical service of restoration. The aim of this study was to assess the effect of flaw size and surface treatments on biaxial flexural strength of feldspathicporcelain. Materials and Methods: Eighty feldspathicporcelain discs were fabricated, polished (P2000) and divided into two series (n=40) each with four subgroups (n=10); three subgroups in each series
Objectives: The aim of this study was to evaluate the effect of different acidic agents on surface roughness of feldspathicporcelain. Materials and Methods: In this study, totally 60 disc shaped Noritake and Ceramco 3 feldspathicporcelain were used. The samples were divided into five groups and immersed in five acidic agents (coke, orange juice, lemonade, mineral water and black-carrot juice). After 168 hours, the specimens were evaluated surface roughness with profi- lometer. Results: The results showed that the highest surface roughness value (4.46 ± 2.9 µm) was identified in lemonade at Noritake porcelain and the lowest surface roughness value (1.06 ± 0.56 µm) was identified in mineral water at Ceramco 3 porcelain. The result of two-way analysis of va- riance test showed that there were no statistically significant differences between acidic agents on surface roughness of feldspathicporcelain (p > 0.05). Conclusions: The obtained data presented that the acidic drinks affected the surface roughness of feldspathicporcelain.
The results of this study indicated that laser irra- diation with power output of 4W (200mJ/20 Hz) and the control group produced similar bond strength val- ues. Pedrazzi et al. reported that Er:YAG laser with low power energy cannot create consistent changes in the porcelain surface to improve the adhesion.  Also, the SBS of the irradiated specimens with power output of 3W (150mJ/20 Hz) and 2W (100mJ/20 Hz) was significantly less than even the control group. Shiu et al. also observed that Er:YAG laser irradiating of a feldspathicporcelain surface at 1W output power (100mJ/10 Hz) did not lead to adequate roughening of the surface due to the composition of the porcelain and its reflectance. Therefore, the extent of the superficial changes on the porcelain surface depends on both the energy density of the laser radiation and the type of irradiated porcelain.  In this study, a significant difference was also observed among different laser power outputs, thus the second null hypothesis was rejected.
Background: The objective of the present study was to evaluate the effect of repeated firings on the metal-ceramic bond strength of cast Ni-Cr and Co-Cr alloy. Materials and Methods: Feldspathicporcelain (VITA VM13 Zahnfabrik, Bad Sackinger, Germany) was fused to Ni-Cr alloy ( Wiron 99, Bego ) and Co-Cr alloy ( Wirobond C, Bego ). Thirty cylindrical specimens were cast for each alloy. Feldspathicporcelain was applied on the upper surface of the cylinders and fired according to manufacturers' instructions. In each group, specimens were divided into 3 subgroups based on repeated firings (3, 5, 7). Shear bond strengths were determined in a universal testing machine (INSTRON 3366, Norwood, USA), with a 2500-kgf load cell and crosshead speed of 1 mm/min), using a custom made steel apparatus. Failure loads were statistically analyzed first with the one-way ANOVA, and then compared with the Student t test. Results: One-way ANOVA test results showed no statistical differences between the metal-ceramic bond strength of Ni-Cr alloy (P = 0.127) and Co-Cr alloy (P = 0.087) after firing 3, 5, and 7 times. The mean shear bond load (N) for Ni-Cr alloy group (860.58 ± 40.81) was significantly higher (p=0.001) than Co-Cr alloy group (679.18 ± 43.31). Conclusion: The mean shear bond strength for the metal ceramic systems tested were not significantly affected by multiple firings and were considered as clinically acceptable for metal-ceramic restorations.
machine ( Fornax GEU, Bego, GERMANY) followed by divesting and finishing the casting to obtain test specimens of uniform dimensions of 10x10x2mm. The dimension of each test specimen was verified by measuring the length and breadth using a stainless steel ruler and the thickness with an Iwanson’s gauge. (Essago, GERMANY) (Fig.17). The acceptable specimens were then air abraded and subsequently steam cleaned to remove surface impurities. In this manner a total of forty metal substructures of standardized dimensions were obtained. These were randomly assigned into two main groups (Group I & Group II) with twenty samples in each test group. Group I & Group II samples were subsequently veneered with feldspathicporcelain and fluorapatite leucite porcelain systems respectively.
Dental ceramics are the preferred materials for oral restorations capitalising on its favourable characteristics, such as; adequate aesthetics, high fracture strength and chemical stability (Rosenblum and Schulman 1997). Dental ceramics may also be used to create crowns, veneers, inlays, onlays and denture teeth. A desirable feature of ceramics is that their appearance can be customised to simulate the colour, translucency and fluorescence of natural teeth. They are biologically and chemically inert, inherently brittle with a good resistance to abrasion. When ceramic powder is comprised of quartz, kaolin, pigments, opacifiers, and a suitable flux with distilled water, the product is traditionally known as dental porcelain. A more acceptable terminology is dental ceramics, however, these two terms are always used interchangeably (Jablonski 2001). The classification of dental porcelain based on composition include, feldspathic porcelains, leucite reinforced feldspathicporcelain, aluminous ceramics, glass infiltrated composites, alumina polycrystals,
Increasing advances in technology make it possible to allow the use of dental prostheses without the metal scene. But the prerequisite for success in any healing process is an exact match prosthesis remaining tooth structure (33). Based on the results of present study we carried that the level of the margin gap that feldspathicporcelain laminate veneers Du ceram system are not blind about the clinical ¼m 273 which is non-negligible, but the laminate veneers In ceram the inner core, rate gap margin around ¼m 115 was based on the study Mclean (1971) which showed the degree of mismatch edge to ¼m 120 in clinical is acceptable), seems to lack marginal in Duceram according to findings (1990 ) Hung SH (28) shrinkage and shrinkage porcelain firing cycle is over. They show that non-uniform deformation of porcelain during the firing phase correction, matching porcelain crowns without affecting the blind. However, the results Hilgert (2003) identified the correct baking In ceram porcelain system does not lead to a marginal reduction. In their study on the marginal adaptation of In ceram internal system 40 copping onto two metal have been finishing line chamfer and shoulder were calculated, then copping both groups under the two types of processes were sandblasting the statistical analysis was shown that the marginal adaptation of coping does not change the results of both studies confirmed our study 34 .
Addison O, Marquis PM, Fleming GJP (2006) 13 studied the impact of hydrofluoric acid surface treatments on the performance of a porcelain laminate restorative material. Sets of 30 Vitadur-Alpha discs were etched with HF acid of three different concentrations (5, 10 and 20%) and for three different etching periods (45, 90 and 180 s). Mean flexure strengths, standard deviations and the associated Weibullmoduli (m) and characteristic stress were determined using biaxial flexure (ball on ring). A significant reduction of the flexural strength of low fusing feldspathicporcelain has been demonstrated to result from etching. As a result it has been proposed that the longevity of porcelain laminate veneer restorations can be improved by adherence to optimizing the pre-cementation HF acid etching time and concentration.
and flexural strength of the veneer ceramic . There- fore, methods have been developed to overcome prob- lems with the veneer layer. These methods include sintering a high-strength CAD/CAM fabricated veneer- ing porcelain cap onto a zirconia coping . The full contour monolithic zirconia has certain advantages to previous zirconia restorations with increased use by clinician. Monolithic zirconia provides high esthetic re- sults as well as high fracture resistance even at a mini- mum thickness. There is no disadvantage to the use of a polished zirconia antagonist to the enamel and feld- spathic porcelain [2–4]. In the present study the mate- rials showed different mean ΔE. Generally, in full ceramic crowns, light transmission and translucency depend on the “crystal content, its chemical nature, particle size, and the thickness of the core” . In the current study, we used the same thickness of materials in each group. The high physical properties in the zir- conia group, may influence relative color stability of the material compared to feldspathicporcelain. However both materials included grain and small particles which might reduce surface roughness and susceptibility to discolor- ation. In addition, the crystalline structure of zirconia might decrease color changes compared to the feldspathic groups which contained more glass matrix .
After sandblasting and obtaining a homogenous oxide layer, coefficient of thermal expansion (CTE) compatibility between porcelain and alloy is mandatory. Otherwise, generated stresses may disrupt the bond by fracturing or debonding the porcelain [11,12]. The ceramic can no longer undergo viscous flow to relieve thermal incompatibility stresses . The adhesion forces between atoms of different materials induce a thermal expansion mismatch. Residual stress is induced in the bonded join upon cooling to room temperature, in the case where the framework contracts more than the bonded ceramic . Cooling metal is quicker because it has good thermal conductivity and dissipates heat rapidly. Due to its pure thermal conductivity, porcelain cools more slowly [24,25]. Zirconia has similar poor conductivity as porcelain. This represents the first important difference between zirconia and metallic framework materials . The thermal conductivity of zirconia stays 15 times smaller than that of alumina and around 100 times smaller than that of gold alloys [27,28]. This slow cooling of zirconia retards the balance between the internal and external temperatures. This results in high transitional temperature differences throughout the restoration, at the thicker and irregular layers and especially upon fast cooling. In the fast cooling method, the temperature gradient between the veneering ceramic and zirconia core may reach up to 140°C . This leads to a high residual tensile stress within the porcelain layer and results in high tempering/compressive residual stresses on the surface .
eighteenth-century European porcelain models, especially those executed in soft-paste porcelains. A soft-paste body was less capable of holding crisp sculptural detail when compared to true, hard-paste porcelain and the addition of polychrome decoration was often employed to create surface detail and compensate for this limitation in the sculptural medium. 247 But this use of colour does represent a radical departure from the white marble model upon which Willems‟ figure group is based and it is a detail difficult to reconcile with the notion that these figures were intended purely as Grand Tour souvenirs. The polychromy of the Red Anchor Pietà is mimetic in character and serves to enhance the naturalism of the group. The flesh tones of the Virgin and the angel are contrasted with the pallor of the dead Christ whose wounds seep red blood, a colour repeated in the robe of the Virgin whilst green grass and coloured flowers lie at her feet. Polychromy was employed in devotional sculpture from the Medieval through the Baroque periods where the very naturalism created by the use of colour served to heighten the affective devotional power of the work. 248 This was a notion explicitly articulated in the Tridentine decrees on the use of images in Catholic worship. 249 Cardinal Gabriele Paleotti‟s Discorso intorno alle immagini sacre e profane (1582), the most comprehensive and influential attempt to explain the rulings of the Council of Trent concerning sacred art, argued against the perceived distortions of Mannerist art and argued for an art that was naturalistic and direct. 250 The Spanish mystic St John of the Cross, who had spent a part of his youth in a sculptor‟s workshop, wrote of the value of polychrome sculpture
The xenolithic and coarse cognate assemblages here form one of the most varied, and best preserved, inclusion suites in Tasmania. As well as containing fragments from the Jurassic dolerite and underlying Permian sandstones and shales, ulrramafic mantle xenoliths, some cumulate textured ultramafic to mafic pyroxenites, disaggregated xenocrysts, and coarse pegmatoidal feldspathoidal and feldspathic crystallisations also occur. 1he mantle xenoliths
Despite the alteration, the Tarkwaian lands spared from the ductile shearing deformation clearly present primary sedimentological structures in terms of bedding. There is a bedding which is sometimes horizontal or tabular and rhythmic or laminate sometimes monoclinal or without any form of cross-bedded stratification. The thickness of the beds is of millimeter to centimeter order within thick decimeter to meter beds. The conglomerate sandstone beds and those of feldspathic sandstone in fine to coarse facies, sometimes silts show intercaltions of sandstone pudding however well exposed in the Zanawa region. In the Tarkwaian mounds of Intiédougou, the conglomeratic levels show lateral variations of facies marked by a decrease in the size and quantity of lithic pebbles.
In this research, petrographic and geochemical (major and trace elements) characteristics of siliciclastic rocks of the Mozduran Formation in the eastern Kopet- Dagh Basin have been carried out in order to reveal their provenance such as source area paleoweathering, parent rock composition and tectonic setting. Mozduran Formation is mainly composed of limestone and dolomite, with minor amounts of siliciclastic rocks and evaporites. Siliciclastics rocks (sandstone and shale) of Mozduran Formation are mainly present in the easternmost parts of the Kopet-Dagh Basin. Four stratigraphic sections of Mozduran Formation, namely Kole-Malekabad, Kale-Karab, Deraz-Ab and Karizak, were measured and sampled in the SE of the basin. Petrographic investigation showed that the sandstones are mostly classifies as litharenite and feldspathic litharenite. Geochemical data revealed that CIA values of Mozduran siliciclastic rocks confirm a medium weathering that can be due to semi-arid climatic condition in the source area. Felsic composition of parent rocks and quatzolithic petrofacies of Mozduran Formation sandstones and their constituents such as Qp, Qm, Ls, Lm and F, together with paleocurrent analysis show that these siliciclastic sediments may have derived from uplifted and trusted belt of sedimentary or sedimentary- metamorphic rocks of south Mashhad and metamorphic rocks of north Fariman region. Petrographic and geochemical analyses suggest that these sediments deposited in a continental rifting system.