Influence Of Ceramic Thickness Research Articles

Influence of ceramic thickness and dental substrate on the survival rate and failure load of non-retentive occlusal veneers after fatigue.

To investigate the effect of ceramic thickness and dental substrate (enamel vs. dentin/enamel) on the survival rate and failure load of non-retentive occlusal veneers. Human maxillary molars (n = 60) were divided into five test-groups (n = 12). The groups (named DE-1.5, DE-1.0, DE-0.5, E-1.0, E-0.5) differed in their dental substrate (E = enamel, DE = dentin/enamel) and restoration thickness (standard: 1.5 mm, thin: 1.0 mm, ultrathin: 0.5 mm). All teeth were prepared for non-retentive monolithic lithium-disilicate occlusal veneers (IPS e.max Press, Ivoclar). Restorations were adhesively cemented (Syntac Classic/Variolink II, Ivoclar) and exposed to thermomechanical fatigue (1.2 million cycles, 1.6 Hz, 49 N/ 5-55°C). Single load to failure was performed using a universal testing-machine. A linear-regression model was applied, pairwise comparisons used the Student-Newman-Keuls method (p < 0.05). Three dentin-based occlusal veneers (one DE-1.0, two DE-0.5) revealed cracks after fatigue exposure, which corresponds to an overall-survival rate of 95%. Load to failure resulted in the following ranking: 2142 N(DE-0.5) > 2105 N(E-1.0) > 2075 N(E-0.5) > 1440 N(DE-1.5) > 1430 N(DE-1.0). Thin (E-1.0) and ultrathin enamel-based occlusal veneers (E-0.5) revealed high failure loads and surpassed the standard thickness dentin-based veneers (DE-1.5) significantly (p = 0.044, p = 0.022). All tested monolithic lithium disilicate occlusal veneers obtained failure loads above physiological chewing forces. Thin and ultrathin enamel-based occlusal veneers outperformed the standard thick dentin-based occlusal veneers. Minimally invasive enamel-based occlusal veneer restorations with non-retentive preparation design may serve as a conservative treatment option.

Influence of ceramic thickness, background and cement shade on the translucency of zirconia reinforced lithium silicate and lithium disilicate ceramics.

Although, the influence of cement and background shade on the final color and translucency of zirconia reinforced lithium silicate (ZLS) and lithium disilicate (LDS) ceramics has been previously investigated, there is still little data on the translucency of LDS and ZLS ceramics in decreased thickness (0.4 and 0.6 mm). The aim of this study was to investigate ceramic thickness', background and cement shades' effects on the zirconia reinforced lithium silicate (ZLS) and lithium disilicate (LDS) ceramics' translucency. Totally 160 square-shaped A1 shade LDS and ZLS samples produced in 0.4 and 0.6 mm thicknesses were cemented with light and neutral shade resin cement on A2 and A3 shade composite resin backgrounds. The color notations of specimen were measured and translucency parameter (TP) values were calculated. Factorial ANOVA and Tamhane's T2 multiple comparison statistical analyzes were used. Highest TP values (11.82±0.97) were obtained in ZLS specimens that were 0.4 mm in thickness, cemented on A2 background with light shade resin cement. While, the lowest TP values (9.60±0.55) were calculated in LDS samples that had 0.6 mm thickness, cemented on A3 background with neutral shade resin cement. Material type, thickness, and background shade affected TP values of specimens. The cement and background shade used might change the final translucency of ZLS and LDS ceramics that had 0.4 and 0.6 mm thickness. Key words:Ceramics, lithium disilicate, spectrophotometry, zirconia, dental materials.

Influence of Ceramic Thickness and Luting Agent on the Survival of Bonded Ceramic Veneers. An in-Vitro Study

The purpose of thislaboratory study was to examine the compressive strength of ceramic veneers of different thicknesses bonded with two different resin cements.A total of 40 ceramic specimens (5x10mm) in dimensions were fabricated according to manufacturer’s instructions. Specimens were randomly divided according to their thicknesses (1 & 2 mm) into two groups (G1, G2), with 20 samples each. Each group was further subdivided two subgroups(RelyX, G-CemLinkAce) according to luting agent applied. All specimens went through thermocycling (1500 cycles between 5-55°C) and compressive test. According to the Kruskal-Wallis test (P<0.05), the highest mean compressive strength value was observed in the GC 2mm group (30.670 ± 2.992 MPa), whereas the lowest mean compressive strength value was observed in RelyX 1mm group 10.380 ± 3.278 MPa). The visual analysis data suggest that GC 2mm group was the only group that showed 100% failures as mixed.The ideal thickness of the veneer should be up to 1.0 mm for high translucency of the veneer andproper polymerization of the luting cement.

Influence of ceramic thickness and cavity design optimization on fracture resistance of partial coverage restorations.

Influence of ceramic thickness and cavity design optimization on fracture resistance of partial coverage restorations.

Transmitted irradiance through ceramics: effect on the mechanical properties of a luting resin cement.

The study aims to characterise the curing behaviour of a light-curing luting composite (Variolink® Aesthetic LC, Ivoclar Vivadent) polymerised at different exposure times (10s, 20s) through different ceramics (IPS Empress CAD and IPS e.max CAD, Ivoclar Vivadent) and ceramic thicknesses (no ceramic, 0.5, 1, 1.5 and 2mm). Curing units' (Bluephase Style, Ivoclar Vivadent) variation in irradiance delivered up to 10-mm exposure distance as well as the incident and transmitted irradiance and radiant exposure up to 6-mm ceramic thickness were assessed on a laboratory-grade spectrometer. A total of 216 (18 groups, n=12) thin and flat luting composite specimens of 500-μm thickness were prepared and stored after curing in a saturated vapour atmosphere for 24h at 37°C. Micro-mechanical properties (Vickers hardness, HV and indentation modulus, YHU) were determined by means of an automatic micro-hardness indenter. Within the study design, the radiant exposure received by the luting composite varied from 2.56 to 24.75J/cm2, showing a high impact on the measured properties. Comparing the effect of the parameters exposure time, ceramic thickness and type, the highest influence on the micro-mechanical parameters was identified for exposure time, while this influence was stronger on HV (p<0.001, η P2=0.452) than on YHU (p<0.001, η P2=0.178). The influence of ceramic type was significant but low (η P2=0.161 on HV and 0.113 on YHU), while the influence of ceramic thickness was the lowest (η P2=0.04 and 0.05, respectively). Slightly higher irradiance values were transmitted through Empress CAD up to a ceramic thickness of 3mm (p<0.001), while being comparable with e.max for thicker slices. Differences in translucency between ceramics were reflected in the micro-mechanical properties of the luting composite. The radiant exposure reaching the luting composite is determined by the incident irradiance, exposure time, ceramic type and ceramic thickness. At the analysed incident irradiance, exposure time was the most consistent parameter affecting the micro-mechanical properties of the luting composite, and this effect was strongly reflected in the more translucent ceramic Empress CAD. Within the curing conditions, an exposure time of 20s is recommended.

Influence of ceramic thickness and type on micromechanical properties of light-cured adhesive bonding agents

Objective. The aim of this study was to evaluate the micromechanical properties of different adhesive bonding agents when polymerized through ceramics. Materials and methods. Sixty sound extracted human third molars were selected and the crowns were sectioned perpendicular to the long axis in order to obtain dentin slices to be bonded with one of the following adhesives: Syntac/Heliobond (Ivoclar-Vivadent) or Adper-Scotchbond-1XT (3M-ESPE). The adhesives were cured by using a LED-unit (Bluephase®, Ivoclar Vivadent) with three different curing times (10 s, 20 s and 30 s) under two ceramics (IPS-e.max-Press, Ivoclar-Vivadent; IPS-Empress®CAD, Ivoclar-Vivadent) of different thicknesses (0 mm, 0.75 mm, 2 mm). Thirty groups were included, each containing 60 measurements. Micromechanical properties (Hardness, HV; indentation modulus, E; and creep, Cr) of the adhesives were measured with an automatic microhardness indenter (Fisherscope H100C, Germany). Data were statistically analyzed by using one-way ANOVA and Tukey's post-hoc test, as well as a multivariate analysis to test the influence of the study parameters (SPSS 18.0). Results. Significant differences were observed between the micromechanical properties of the adhesives (p < 0.05). The ceramic type showed the highest effect on HV (Partial-eta squared (η2) = 0.109) of the tested adhesives, while E (η2 = 0.275) and Cr (η2 = 0.194) were stronger influenced by the adhesive type. Ceramic thickness showed no effect on the E and Cr of the adhesives. Conclusions. The adhesive bonding agents used in this study performed well by curing through different thicknesses of ceramics. The micromechanical properties of the adhesives were determined by the adhesive type and were less influenced by ceramic type and curing time.

Influence of ceramic thickness on residual stress and bonding strength for plasma sprayed duplex thermal barrier coating on aluminum alloy

NiCoCrAlY/8wt.%Y2O3–ZrO2 coating was plasma sprayed on aluminum alloy to evaluate the effect of ceramic thickness on residual stress and bonding strength. A new stress calculation method based on Stoney equation and substrate-removal technique was proposed. Stress in both bond coat and ceramic was studied. With the increase of ceramic thickness, the residual stress in both layers was firstly compressive then turned tensile. The large thermal expansion coefficient of the substrate played an important role in residual stress formation when the ceramic was thin. However, the intrinsic deposition stress took a dominant position when the ceramic coating turned thicker. The bonding strength decreased and the location of the fractured surface moved toward the ceramic surface. The moving of the surface was mainly resulted from the variation of stress gradient and the weakness of high porosity zone near the bond coat–ceramic interface.

Influence of ceramic thickness and curing mode on the polymerization shrinkage kinetics of dual-cured resin cements

Objectives The purpose of this study was to assess how ceramic disc thickness and curing mode (light or chemical) affects the polymerization shrinkage of dual-cured resin cements and to evaluate the effect of the ceramic discs on the curing speed of the cements during light exposure. Methods Six commercial resin cements, RelyX ARC, Bistite II, Duolink, Panavia F, Variolink II and Choice were used. Filler weight contents were determined by the ash method. Four ceramic discs with thicknesses of 0.5, 1, 2 and 4 mm, respectively, were made. The attenuation of light intensity due to the ceramic discs was measured using a radiometer. The polymerization shrinkage kinetics of the resin cements by chemical or light cure through the different ceramic discs was measured using a bonded-disc method. Results There were differences in filler content among brands of resin cement. The polymerization shrinkage without ceramic disc was 2.61–4.59% by chemical cure and 2.93–4.66% by light cure. The polymerization shrinkage of RelyX ARC and Panavia F by chemical cure was statistically lower than by light cure ( p < 0.05). Polymerization shrinkage and filler weight were inversely related ( R = −0.965). Both the transmitted light intensity and polymerization shrinkage decreased with increasing thickness of ceramic discs ( p < 0.05). The time to reach the maximum shrinkage rate of the resin cements increased with increasing ceramic thickness. The cure speed by light cure was 15–322 times faster than by chemical cure. Significance The polymerization shrinkage kinetics of dual-cured resin cements significantly differed between brands under various curing conditions. Clinicians should be aware of the setting characteristics of the cements, so they can choose the optimal materials for different clinical situations.

Partial Ceramic Crowns: Influence of Ceramic Thickness, Preparation Design and Luting Material on Fracture Resistance and Marginal Integrity In Vitro

This in vitro study tested the effects of two different ceramic thicknesses, two preparation designs and two different luting agents on the marginal integrity and fracture resistance of partial ceramic crowns (PCC). Eighty extracted human molars were prepared according to the following preparation designs: a) Coverage of functional cusps/butt joint (n=40), b) Horizontal reduction of functional cusps (n=40). PCC (Vita Mark II, Cerec3 System) were fabricated and the ceramic thickness of the functional cusps was adjusted to (1): 0.5-1.0 mm and (2): 1.5-2.0 mm. PCC were adhesively luted to the cavities with either Excite/VariolinkII (VL) or RelyX Unicem (RX). The specimens were exposed to thermocycling and central mechanical loading (5000 x 5 degrees C-55 degrees C; 30 second/cycle; 50,0000 x 72.5N, 1.6Hz). Marginal integrity was assessed by evaluating dye penetration (fuchsine) on multiple sections in the bucco-oral direction by relating the actual penetration distance to the maximal length of the corresponding cavity wall (100%). Restoration/luting agent (RL)--and tooth/luting agent (TL) interfaces were evaluated separately. The data were statistically analyzed with the Mann Whitney U-test and the Error Rates Method (ERM), and the fracture rates were analyzed with the chi2-test. Dye penetration data indicated that ceramic thickness and luting agent had a statistically significant influence upon marginal integrity in general, irrespective of all other parameters (ERM): RX showed significantly lower microleakage along the RL interface than VL. VL revealed significantly lower microleakage at the TL interface than RX. Fifteen PCC of group 1 (0.5-1.0 mm) and two PCC of group 2 (1.5-2.0 mm) were fractured after thermocycling and central mechanical loading, with the difference being statistically significant. PCC fabricated from industrially sintered feldspathic ceramic should have at least a thickness of 1.5-2.0 mm in stress-bearing areas.

Influence of ceramic thickness and polymerization mode of a resin luting agent on early bond strength and durability with a lithium disilicate-based ceramic system

Influence of ceramic thickness and polymerization mode of a resin luting agent on early bond strength and durability with a lithium disilicate-based ceramic system

MODELING PENETRATION OF CERAMIC/METAL LIGHTWEIGHT —1 ARMOURS BY SMALL AND MEDIUM CALIBER PROJECTILES

In this paper, an analytical model is developed to describe the penetration of ceramic/metal lightweight armours by small and medium caliber-projectiles, 4 respectively. Both the projectile and back plate materials are assumed to behave as rigid-perfectly plastic with respect t9, .their nominal stress-engineering strain relationships. Two modes are associated with the back plate and the projectile, respectively, during the penetration 'Ptocess; these are erosion and rigid The model identifies three main phases for the penetration of a lightweight armour; these are: (i) ceramic fragmentation, (ii) penetration of fragmented ceramic and (iii) penetration of back plate. Phase (i) consists mainly of one stage, whereas the other two, i.e. phase (ii) and phase (iii), consist mainly of different penetration stages, respectively. The current penetration stage is ascertained according to the relative velocities between the projectile mass and the mass of remaining ceramic and/or the mass of the back plate ahead of projectile. The main equations representing each penetration stage are derived based on momentum conservation principle. The present model is capable of predicting the time-histories of the velocities of the moving masses and the projectile penetration depth through ceramic/metal lightweight armour as well as post-perforation results. Matching predicted results of the present model with the experimental and numerical results of other investigators serves to determine the flow stress of the ceramic material globally. The present results are concerned with design optimization of ceramic/metal lightweight armours capable of defeating small and medium caliber projectiles. The influence of ceramic thickness and strength as well as back plate thickness and strength on the ballistic limit of the armours considered is presented and discussed. Moreover, the effect of ceramic thickness on projectile remaining mass and residual velocity are discussed.