Comparison of Marginal and Internal Adaptation in Endocrowns Milled from Translucent Zirconia and Zirconium Lithium Silicate

Purpose. This study aimed to compare marginal and internal adaptation in endocrowns made from translucent zirconia and zirconium lithium silicate using CAD-CAM technology. Materials and Methods. Twenty-eight freshly extracted upper molars were mounted in acrylic resin and underwent root canal therapy and endocrown preparation up to 2 mm above the cementoenamel junction. Endocrowns were CAD-CAM milled from zirconium lithium silicate (ZLS) and translucent zirconia (Zr). Internal and marginal adaptation was assessed by the replica technique before cementation. Marginal adaptation was evaluated by a stereomicroscope (×32) before and after cementation and also after thermomechanical aging. Results. The ZLS group showed significantly higher internal adaptation compared to the Zr group ( P = 0.028), while the marginal adaptation differences, at different times with different methods, were not statistically significant ( P > 0.05). Axiomarginal angle had the highest and axiopulpal angle showed the lowest adaptation in both groups. The cementation process and thermomechanical aging increased the marginal gap in both groups significantly ( P < 0.001). The marginal gap assessed by the replica technique before cementation was 7.11 µm higher than direct view under a stereomicroscope with intraclass correlation coefficient of 0.797. Conclusion. Zirconia seems to be an acceptable material for endocrown with comparable internal and marginal adaptation to ZLS. Cementation and thermomechanical aging had significantly negative effects on marginal gap. The marginal gap assessed by the replica technique was higher than direct view under the stereomicroscope technique.

Laser-induced optical nonlinearity in a Li-rich glass

The selective crystallization of a photosensibilized lithium silicate glass after a light emitting diode (280 nm) and a nanosecond laser (355 nm) UV irradiation and subsequent heat treatment was studied. Using a focused beam of the laser allows successive drawing regions in which the formation of silver nanoparticles after 500°C heat treatment of the glass co-doped with silver and cerium ions takes place. It is shown that this treatment is a necessary step for the growth of sodium metasilicate crystals under the second thermal treatment of the glass at 600 °C, while these regions demonstrate second optical harmonic generation of 1064 nm nanosecond laser radiation.

Impact of cement type and abutment height on pull-off force of zirconia reinforced lithium silicate crowns on titanium implant stock abutments: an in vitro study

Background Pull-off forces of cement-retained zirconia reinforced lithium silicate (ZLS) in implant-supported single crowns on stock titanium abutments with respect to abutment height and implant cement were evaluated and compared. Methods Pull-off force of ZLS crowns on stock titanium abutments was evaluated concerning dental cement and abutment height. A total sample size of 64 stock abutments with heights of 3 mm (n = 32) and 5 mm (n = 32) was used. The ZLS crowns were cemented with four different types of cement (one temporary, two semi-permanent, and one permanent). After cementation, water storage, and thermocycling each sample was subjected to a pull-off test using a universal testing machine. Results The temporary cement showed the least pull-off force regardless of abutment height (3/5 mm: means 6 N/23 N), followed by the semi-permanent methacrylate-infiltrated zinc oxide cement (28 N/55 N), the semi-permanent methacrylate-based cement (103 N/163 N), and the permanent resin composite cement (238 N/820 N). Results of all types of cement differed statistically significantly from each other (p ≤ .012). The type of implant cement has an impact on the pull-off force of ZLS crowns and titanium abutments. Conclusions Permanent cements present higher retention than semi-permanent ones, and temporary cements present the lowest values. The abutment height had a subordinate impact.

Comparison of Retention and Fracture Load of Endocrowns Made from Zirconia and Zirconium Lithium Silicate After Aging: An in-Vitro Study

Background: This study aimed to compare retention and fracture load in endocrowns made from zirconium lithium silicate and translucent zirconia.Methods: Fifty-six intact human maxillary molars after being mounted in acrylic resin, were scanned to acquire biogeneric copies. Specimens underwent standard endodontic treatment and were prepared for endocrown up to 2 mm above the cementoenamel junction. The specimens were randomly divided into two groups of 28 and endocrowns were designed using biogeneric copies and milled from high-translucent zirconia disks (Zr) and zirconium lithium silicate blocks (ZLS). After cementation with dual cure resin cement, all the specimens underwent thermomechanical aging and pull-out retention test and compressive test were conducted (14 specimens were used for each test in each group, n=14) and failure modes in both tests were evaluated.Results: Independent samples t-test showed significant difference between the retention of Zr (271.5 N ±114.31) and ZLS (654.67 N ±223.17) groups (p value = 0.012). Compressive test results were also significantly different between Zr (7395.07 N ±1947.42) and ZLS (1618.3 N ±585) (p = 0.002). Failure mode of retention test was primarily adhesive failure at the cement-restoration interface in Zr group and cement-tooth interface in ZLS group. Failure modes of fracture test for Zr group were 7 non-restorable fractures and one restorable fracture while 6 specimens resisted compressive loads up to 8500 N without fracture. ZLS group showed 7 restorable and 7 non-restorable failures.Conclusions: Zr endocrowns showed significantly lower retention and higher fracture strength. Both materials seem to be suitable for fabrication of endocrown in clinical setup.

The Influence of Three Different Digital Cement Spacers on the Marginal Gap Adaptation of Zirconia-Reinforced Lithium Silicate Crowns Fabricated by CAD-CAM System

Background: This study compared the influence of three different radial spacers (60,90,120 microns) on the marginal gap adaptation by using computer-aided manufacturing (CAD-CAM) for producing monolithic zirconia reinforced lithium silicate (ZLS) ceramic crowns. Methods: A total of 45 abutment acrylic teeth were divided into three groups of different radial spacers (60, 90, and 120 microns). In each group 15 teeth were scanned by Omnicam intra oral scanner and ZLS crowns were ground. For each unit the marginal gap was evaluated at four regions of interest by scanning electronic microscope (SEM). To compare the marginal gap between the three groups a one-way ANOVA with post-hoc Bonferroni test was preformed (α = 0.05). Results: The marginal gap for a 60 microns (162.99 ± 16.25 µm) radial spacer was found significantly higher than 90 (41.85 ± 3.57 µm) and 120 (41.85 ± 5.3 µm) microns radial spacers (p < 0.05). Between 90- and 120-micron radial spacers no difference was obtained. (p < 0.05). Conclusions: A radial spacer of 60 microns showed a significantly higher marginal gap compared to 90 and 120 microns and was not clinically accepted (>120 microns). For both 90 and 120 microns the marginal gap was clinically accepted (<120 microns) with no difference between the groups. The radial spacer which should be optimum for CELTRA® DUO crowns is 90 microns.

Preparation of Composite Electrodes for All-Solid-State Batteries Based on Sulfide Electrolytes: An Electrochemical Point of View

All-solid-state batteries (ASSBs) are a promising response to the need for safety and high energy density of large-scale energy storage systems in challenging applications such as electric vehicles and grid integration. ASSBs based on sulfide solid electrolytes (SEs) have attracted much attention because of their high ionic conductivity and wide electrochemical windows of the sulfide SEs. Here, we study the electrochemical performance of ASSBs using composite electrodes prepared via two processes (simple mixture and solution processes) and varying the ionic conductor additive (80Li2S∙20P2S5 and argyrodite-type Li6PS5Cl). The composite electrodes consist of lithium-silicate-coated LiNi1/3Mn1/3Co1/3O2 (NMC), a sulfide SE, and carbon additives. The charge-transfer resistance at the interface of the solid electrolyte and NMC is the main parameter related to the ASSB’s status. This value decreases when the composite electrodes are prepared via a solution process. The lithium silicate coating and the use of a high-Li-ion additive conductor are also important to reduce the interfacial resistance and achieve high initial capacities (140 mAh g−1).