Lithium Disilicate Ceramic Material Research Articles

Instrumental Color Evaluation of Ceramic Materials by Using Two Dental Spectrophotometers

Objectives: The aim of the present study was to evaluate the precision of two dental spectrophotometers in evaluating the color parameters of ceramic materials and to assess the accuracy of a dental spectrophotometer (Shade Pilot, Degudent) for analyzing color parameters of lithium-disilicate ceramic materials. Methods: The CIE L*a*b* color parameters, chroma and hue angle of 6 groups of lithium-disilicate ceramic ingots were recorded: MO0, HO0, LTA1, HTA1, LTBL1, HTBL. The measurements were performed in a viewing-booth under a D65 illuminant. Statistical analysis was performed to assess the precision and differences between the two color-measuring devices. Results: Significant differences were found between all color parameters recorded (p<0.001). The difference varied depending on the type of ceramic ingot assessed. The HO0 ingot showed the highest color difference (ΔE=19.18), while the smallest color difference was found for the MO0 ingot (ΔE=5.62). Conclusions: Color parameters of ceramic materials can be recorded with both color-measuring devices, the VEA showing the highest precision.

Flexural properties of leucite and lithium disilicate ceramic materials after repeated firings

Background/purposePressable all-ceramic materials are widely used in dentistry. Determining the effect of repeated firing on flexural strength will help to improve these materials so that they can remain resistant to fracture in restorative work. The aim of this study was to determine the change in the flexural strength of pressable all-ceramic materials after repeated firings, which may be unavoidable when color and shape corrections are necessary for use in dental restorations. Materials and methodsForty disc specimens (15.5 mm × 2.1 mm) were prepared for each of four pressable ceramic materials (Empress 2, Finesse, Cergo, and Evopress) according to the manufacturers' instructions. Each group of specimens was tested for biaxial flexural strength (piston on three balls test) after the first (n = 10), third (n = 10), fifth (n = 10), and seventh (n = 10) firing periods. The data were analyzed using one-way analysis of variance. The Tukey multiple comparison test was then used to compare the strength of the different materials, and the Newman–Keuls multiple comparison test was used to compare the strength at each firing interval measured (α = 0.05). ResultsThe strengths of all of the pressable ceramic materials were decreased by repeated firings, especially after the seventh firing period, the only case in which the decrease was statistically significant. The flexural strength of the leucite-reinforced ceramic (Cergo) after the seventh firing was significantly lower than after the first firing (P = 0.04). The other materials were not significantly affected by repeated firings (P > 0.05). ConclusionThe number of firings does not appear to significantly affect the flexural strength of pressable all-ceramic materials.

A Different Pontic Design for Fiber-Reinforced Composite Bridgeworks: A Clinical Report

This clinical report describes a relatively simple but esthetic, non-invasive and functional prosthodontic treatment option for a patient with missing tooth. A patient with a missing maxillary left canine was non-invasively treated with a fiber reinforced composite (FRC) bridgework with an all ceramic (Empress II, Ivoclar Vivadent, Schaan, Liech-tenstein) pontic design, using laboratory technique. The restoration has served the patient for 2 year, seemingly without discomfort, and it has not required any maintenance. The patient has kept up with his oral hygiene. Although additional clinical experience is necessary, fiber-reinforced composite materials can be used in combination with a lithium disilicate ceramic material in fixed partial dentures.

Adhesive bonding of a lithium disilicate ceramic material with resin‐based luting agents

This study evaluates the bonding characteristics of a lithium disilicate-based ceramic material (IPS Empress 2). Two sizes of disk specimens of the material were made, and three groups of disk pairs were separately surface-prepared using three techniques; etching with phosphoric acid, etching with hydrofluoric acid, and air-abrasion with alumina. Each group was further divided into four sub-groups; group (i) was bonded with the Variolink II composite, (ii) was treated with the Monobond-S silane primer and bonded with the Variolink II composite, (iii) was bonded with the Super-Bond acrylic adhesive and (iv) was treated with the Porcelain Liner M silane primer and bonded with the Super-Bond acrylic adhesive. Shear bond strengths were determined before and after 100 000 thermocycles. Bond strength varied from 10.6 to 71.5 MPa before thermocycling, whereas post-thermocycling bond strength ranged from 0 to 61.2 MPa. Among the three surface preparations, hydrofluoric acid etching (HF) was most effective in enhancing bond strength of both luting materials, especially for unsilanized specimens. Application of the silane primer elevated bond strength of both luting agents regardless of surface preparation method. It can be concluded, for both luting agents, that durable bond to the Empress 2 ceramic material can be achieved through the combined application of HF and the proprietary silane primer.