Zirconia-reinforced Lithium Silicate Ceramics Research Articles

Effects of polishing or glazing on surface roughness and microhardness after milling CAD-CAM ceramic materials

Objective: This study aimed to evaluate the surface roughness and microhardness of CAD-CAM ceramic blocks after different surface finishing protocols. Materials and methods: Three ceramics were evaluated: lithium disilicate, leucite-reinforced feldspathic and zirconia-reinforced lithium silicate. Ninety specimens were obtained and distributed into 3 groups (n=10): polishing (specimens were polished with an abrasive rubber kit); conventional glaze (according to the manufacturer's recommendations); and, extended glaze (the specimens were kept for 15 minutes at maximum firing temperature and the furnace was kept closed until reaching 200ºC). In all specimens, a drill was used to simulate the milling machine and thus obtain the initial roughness. Surface roughness was evaluated before and after the finishing protocols, while Vickers microhardness was performed only after the finishing protocols. Roughness data were analyzed to repeated measures two-way ANOVA and Bonferroni post-hoc test and ANOVA with Welch correction and Games-Howell test were used to analyze microhardness data (α = 0.05). Results: Both conventional and extended glazes showed greater smoothness for lithium disilicate and zirconia-reinforced lithium silicate ceramics, while for Empress, extended firing of the glaze provided greater surface smoothness. Regarding microhardness, there was no statistically significant difference among the protocols for the same material. The conventional glaze group made from lithium disilicate did not show a significant difference in microhardness values in relation to the other groups. Conclusion: The application of glaze improves the surface smoothness of the ceramics after milling procedure. There is no change in microhardness with different surface finishing protocols.

Effect of 4-META on microtensile bond strength of cements to ceramics

Background: This study assessed the effect of different concentrations of 4-methacryloyloxyethy trimellitate anhydride (4-META) added to silane on microtensile bond strength (µTBS) of light-cure and dual-cure resin cement to hybrid and zirconia-reinforced lithium silicate ceramics. Materials and Methods: This in vitro, experimental study was conducted on 32 Celtra Duo and 32 VITA Enamic ceramics bonded to Allcem Veneer light-cure and Allcem dual-cure resin cements using silane impregnated with 4-META in 0%, 2.5%, 5%, and 10 wt% concentrations in 16 groups (n = 4). The µTBS of specimens was measured by a universal testing machine and analyzed by the Kruskal–Wallis and Mann–Whitney tests, and the mode of failure was determined under a stereomicroscope and analyzed by the Chi-square test (alpha = 0.05). Results: The lowest mean µTBS was recorded in the Enamic ceramic group with 4-META (0%) bonded to dual-cure cement (14.26 MPa), and the highest mean µTBS was recorded in Enamic ceramic with 4-META (10%) bonded to light-cure cement (18.59 MPa) (P < 0.001). The µTBS of Celtra Duo was significantly higher than that of Enamic in bonding to light-cure cement using 4-META (2.5%) (P = 0.003). All failures (100%) were adhesive in most groups. The frequency of adhesive failure was the lowest (90%) in Celtra Duo bonded to dual-cure cement with 4-META (5%). Conclusion: According to the results of this pilot study, the addition of 4-META (10%) to silane caused a significant improvement in µTBS to light-cure cement. The addition of 4-META in all concentrations significantly improved the µTBS to Enamic ceramic in the use of dual-cure cement; however, it had no significant effect on µTBS of Celtra Duo. Nonetheless, the results should be interpreted with caution due to the relatively small sample size.

Effects of Various Laser Treatments on Surface Characterization and Repair Bond Strength of Zirconia-Reinforced Lithium Silicate Ceramics.

To evaluate the effects of two different lasers and their use in combination with hydrofluoric acid (HF) etching on the surface roughness of zirconia-reinforced lithium silicate (ZLS) ceramics and their shear bond strength (SBS) to composite resin. The five study groups were as follows: (1) Group H = HF etching; (2) Group N = Nd:YAG (neodymium: yttrium-aluminum-garnet) laser; (3) Group NH = Nd:YAG laser + HF gel; (4) Group E = Er:YAG (erbium: yttrium-aluminum-garnet) laser; and (5) Group EH = Er:YAG laser + HF gel. Surface roughness was assessed using a noncontact profilometer, and SBS tests were conducted with a universal testing machine. The mean SBS values were 16.23 ± 1.77 MPa for Group H, 17.1 ± 1.65 MPa for Group N, 16.65 ± 1.11 MPa for Group NH, 8.08 ± 1.12 MPa for Group E, and 11.58 ± 0.82 MPa for Group EH. There were significant differences between groups E and EH (P < .001) but no significant differences (P > .05) among the other groups. Clinicians may prefer Nd:YAG laser or the combination of Nd:YAG and HF to intraorally repair fractured areas.

Effect of Artificial Aging on Translucency of Zirconia Reinforced Lithium Silicate and Lithium Disilicate Ceramics: A Systematic Review.

Digital dentistry and advanced ceramic materials have been widely used but which material has a better esthetically durable outcome needs to be evaluated. The purpose of this systematic review and meta-analysis was to evaluate the difference in the translucency of CAD zirconia-reinforced lithium silicate and CAD lithium disilicate glass ceramics after being subjected to artificial aging. Two independent reviewers searched the MEDLINE/ PubMed, Embase, and EBSCO databases and the Google Scholar search engine for in-vitro studies published from January 2010 to May 2023 to identify relevant studies measuring the translucency of CAD ZLS and CAD lithium disilicate glass ceramics after being subjected to different artificial aging conditions using the coffee solution, 4% acetic acid, distilled water and UV aging. For qualitative synthesis, 10 studies were included. A statistically significant difference was observed between CAD zirconia-reinforced lithium silicate and CAD lithium disilicate glass ceramics (P⟨0.05, mean difference=-0.25 [-0.38,-0.11]). Translucency of CAD ZLS was less than CAD lithium disilicate glass ceramics. Artificial aging has decreased the translucency of glass ceramics. For fixed prosthetic rehabilitation clinicians can opt for CAD lithium disilicate glass-ceramic as a more esthetically pleasing and durable material in oral environment.

Zirconia-Reinforced Lithium Silicate Ceramic in Digital Dentistry: A Comprehensive Literature Review of Our Current Understanding.

Zirconia-reinforced lithium silicate (ZLS) ceramic is a new innovative dental material with unique a chemical composition that is designed to combine harmoniously with the appropriate optical properties of lithium disilicate and the enhanced mechanical strength of zirconia. A thorough understanding of ZLS materials is essential for both clinicians and dental technicians. At present, the mechanical behavior and optical properties of the ZLS ceramic system have not been extensively researched, and there is still a lack of consensus regarding the fabrication process and clinical behavior of ZLS all-ceramic restorations. The aim of the present study was to present a selection of comprehensive information concerning zirconia-reinforced lithium silicate ceramics and their optical and mechanical properties, as well as to assess data regarding cementation procedures and clinical outcomes for ZLS all-ceramic restorations. Three electronic databases (PubMed, Web of Science, and the Cochrane Library) were used for the research by two independent reviewers. The search was limited to articles published in the English language, as well as clinical and in vitro studies of color and studies on mechanical behavior and the cementation procedures of ZLS restorations. The exclusion criteria comprised abstracts, questionnaire-based studies, case reports, literature reviews, and studies that were not available in English. Zirconia-reinforced lithium-silicate-based ceramic presents a unique and complex microstructure that increases mechanical resistance but decreases aesthetic appearance, especially its translucency, due to tetragonal zirconia content. A material's thickness, the color of the underlying tooth structure, and the resin cement shade are important factors that influence the final shade and aesthetic appearance of ZLS restorations. Mechanical properties, which are defined by the fracture toughness, flexural strength, elastic modulus, and hardness of ZLS ceramic are higher compared to feldspathic, lithium disilicate, and hybrid ceramics, as well as resin nanoceramics; however, they are lower than translucent or high-translucency zirconia. Acid etching, sandblasting, and laser etching represent the most used methods to prepare the ZLS restoration surfaces for proper bonding procedures.

Comparative analysis of endocrown fracture resistance and marginal adaptation: CAD/CAM technology using lithium disilicate vs. zirconia-reinforced lithium silicate ceramics

AimsThe present study aimed to compare the fracture resistance and marginal adaptation of endocrowns fabricated using lithium disilicate (LDS) and zirconia-reinforced lithium silicate 9ZLS) ceramics by the computer-aided design and computer-aided manufacturing (CAD/CAM) technology. Materials and MethodsIn this in vitro experimental study, 24 extracted mandibular first molars received standard endocrown preparation and were randomly assigned to two groups (n = 12) for the fabrication of endocrowns with ZLS (Suprinity) and LDS (IPS e.max CAD) ceramics. After scanning the teeth with a CAD scanner, endocrowns were designed by inLab Software version 15 (inLab SW 15) and prepared by an imes-icore 350i milling machine. The vertical marginal gap of endocrowns was measured under a stereomicroscope at three steps before and after cementation and after thermomechanical cycles. The fracture resistance of specimens was then measured by load application at a 45° angle. Mode of failure was also determined as reparable or irreparable. Data were analyzed using Pearson’s correlation test and t-test. ResultsThe mean fracture resistance of ZLS endocrowns was significantly higher than that of LDS endocrowns (P = 0.000). The reparability of ZLS endocrowns was zero, while that of LDS endocrowns was 83.33 %. The vertical marginal gap was significantly smaller in ZLS than in LDS endocrowns at all three time points (P < 0.05). Also, the marginal gap increased by cementation and thermomechanical cycles in both groups. ConclusionZLS and LDS endocrowns both showed acceptable vertical marginal adaptation. ZLS had superior marginal adaptation and higher fracture resistance.

Influence Of Surface Treatment On The Physical Properties And Biofilm Formation Of Zirconia-Reinforced Lithium Silicate Ceramics: In Vitro Trial.

To evaluate the performance of fully (Celtra Duo, Dentsply Sirona) and partially (VITA Suprinity, VITA) crystallized zirconia-reinforced lithium silicate and partially sintered lithium disilicate (IPS e.max CAD, Ivoclar Vivadent) glass-ceramics submitted to polishing, glazing, or no surface treatment after aging. Specimens of each glass-ceramic were subjected to polishing with rubber cups (POL), glazing (GL), or control (C; no treatment) and afterwards aged with 18,000 thermal cycles (5°C to 55°C). The average roughness (Ra), 2D and 3D morphology, contact angle, multispecies biofilm formation (Streptococcus mutans and Candida albicans), and mechanical strength were evaluated by atomic force microscopy (AFM, n = 5), sessile-drop goniometry (n = 5), spectrophotometry (n = 5), and flexural strength test (n = 10), respectively. Data were analyzed using two-way analysis of variance and Tukey test (α = 5%). POL promoted lower Ra than glazing, and Celtra Duo presented higher Ra than IPS e.max CAD (P < .05). Surfaces without polishing promoted higher Ra than the POL group (P < .001), greater contact angle (P < .001), and significant morphologic changes, regardless of the glass-ceramic. Irrespective of the treatment, the contact angle was higher in Celtra Duo, and regardless of the material, there was higher biofilm formation and lower flexural strength of unpolished compared to POL or GL ceramics. Polishing with rubber cups promoted lower roughness and minor morphologic surface alterations, but biofilm formation and flexural strength were similar to the glazed surface. In general, Celtra Duo and VITA Suprinity showed similar behavior to IPS e.max CAD, which makes zirconia-reinforced lithium silicate glass-ceramics a good option for indirect restorations.

Effects of Surface Treatment and Thermocycling on the Shear Bond Strength of Zirconia-Reinforced Lithium Silicate Ceramic.

To investigate the effects of different surface treatments and thermocycling on shear bond strength (SBS) be-tween resin cement and zirconia-reinforced lithium-silicate (ZLS) ceramic. 96 ZLS ceramic specimens were randomly allocated to four different surface treatment groups: etch and silane (ES), etch and universal primer (EUP), self-etching primer (SEP), and sandblasting and silane (SS). Stan-dardized composite cylinders were bonded to surface-treated ZLS ceramic, after which SBS was obtained either after 24-h water storage only or with an additional 5000 thermal cycles (TC), resulting in eight subgroups (n = 12). After evaluation of failure mode under a stereomicroscope, representative SEM images were acquired. To examine areal average surface roughness (Sa), additional ZLS specimens were prepared and randomly allocated to 3 groups: hydrofluoric acid etching, self-etching primer, and sandblasting (n = 10). Supplementary specimens were examined using field-emission scanning electron microscopy (FE-SEM) (n = 2) and atomic force microscopy (AFM) (n = 2) to investigate their surface topographies. ANOVA showed a statistically significant difference in SBS following different surface treatment protocols after 24-h water storage (p < 0.001). However, TC groups revealed no statistically significant difference in their SBS (p = 0.394). All surface treated groups were significantly affected by TC (p < 0.001), except for the SS group (p = 0.48). Sa was signifi-cantly influenced by the different surface treatment protocols (p < 0.001). The ability of self-etching primer to achieve comparable bond strength with a less technique-sensitive ap-proach makes it a favorable alternative to ES for the surface treatment of ZLS ceramics.

Comparative Evaluation of Micro Shear bond Strength of Self-Adhesive Resin Cement to Two Commercially Available Zirconia-Reinforced Lithium Silicate Ceramics

Comparative Evaluation of Micro Shear bond Strength of Self-Adhesive Resin Cement to Two Commercially Available Zirconia-Reinforced Lithium Silicate Ceramics

Flexural Strength Properties of Five Different Monolithic Computer-Aided Design/Computer-Aided Manufacturing Ceramic Materials: An In Vitro Study.

Objective The purpose of this in vitro study is to compare the flexural strength and Weibull modulus of 5 different monolithic computer-aided design/computer-aided manufacturing (CAD/CAM) ceramics. Methods A total of 50 specimens were fabricated, 10 from each of the following materials: lithium disilicate-based ceramic (IPS e.max CAD), zirconia -reinforced lithium-silicate ceramic (Vita Suprinity), leucite-based glass ceramic (IPS Empress CAD), and two zirconia-based ceramics (Zenostar and CopraSmile). The specimens were 4 mm wide, 2 mm thick, and 16 mm long. Flexural strength test was executed using a universal testing machine (Model 5980, Instron Industrial Products, Norwood, MA, USA). The two-parameter Weibull distribution function was used to analyze the variability of flexural strength values. Statistical analysis was performed on SPSS Version 23 (IBM Corp., Armonk, NY, USA) using one-way analysis of variance (ANOVA) and post-hoc Tukey's test. Results Suprinity had the highest Weibull modulus value, while Empress CAD displayed the lowest value. One-way ANOVA showed significant difference in the flexural strength between the different materials tested (p<0.05). Post-hoc analysis revealed significant differences among all the test groups in terms of flexural strength. Zenostar presented the highest mean flexural strength value (1033.90 MPa), while Empress CAD had the lowest value. Conclusion High-translucency zirconia had superior flexural properties than translucent zirconia, lithium disilicate ceramics, zirconia-reinforced lithium silicate ceramics, and leucite-based glass ceramics.

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.

Three-year clinical evaluation of zirconia and zirconia-reinforced lithium silicate crowns with minimally invasive vertical preparation technique

ObjectivesLarge part of the tooth is required to be removed during crown preparation. A minimally invasive method for preparing single crowns is required to increase the durability of teeth. The aim of this study was to evaluate the clinical performance of two ceramic systems fabricated with minimally invasive vertical preparation.Materials and methodsForty endodontically treated maxillary premolars were prepared with vertical preparation and received temporary crowns for a period of 21 days. Twenty zirconia-reinforced lithium silicate (Celtra Duo HT, Dentsply Sirona, Germany) and 20 monolithic high translucency zirconia (Katana HT, Kuarary Noritake, Japan) crowns were fabricated by CAD/CAM and cemented with dual-polymerizing luting resin. The crowns were evaluated clinically and radiographically for 36 months following modified FDI criteria. Statistical analysis was conducted with t Student test (Cochran Q).ResultsOver the follow-up period, there was no need to replace any of the study’s crowns. The overall survival rate of the 40 crowns was 100% according to the Kaplan–Meier survival method. The clinical quality of all crowns and the patient’s satisfaction were high. No caries was detected and no adverse soft tissue reactions around the crowns were observed. Periodontal probing depth was reported to be increased at mesial and distal sites more than the facial one in the 36-month follow-up with no statistically significant difference between both materials (P = 0.186).ConclusionsZirconia and zirconia-reinforced lithium silicate could be used as a material for restoration of teeth prepared with vertical preparation technique. Both ceramic materials achieved good esthetic results, promotes healthy and stable soft tissues with no mechanical complications after 3 years of clinical evaluation.Clinical relevanceMonolithic high translucency zirconia and zirconia-reinforced lithium silicate ceramics can be used for the restorations of minimal invasive vertical preparation in premolar area with 0.5 mm margin thickness.

Effect of surface treatments on bond durability of zirconia-reinforced lithium silicate ceramics: An in vitro study

Statement of problemThe influence of surface treatments on the bond durability of zirconia-reinforced lithium silicate ceramics (ZLS) is unclear. PurposeThe purpose of this in vitro study was to evaluate the effect of different surface treatments on the bond durability of zirconia-reinforced lithium silicate ceramic after long-term thermocycling. Material and methodsFive computer-aided design and computer-aided manufacturing (CAD-CAM) dental ceramic blocks, including 2 zirconia-reinforced lithium silicate ceramic materials (Vita Suprinity/VS and Cetra Duo/CD), 2 commonly used glass-ceramic materials (e.max CAD/EM and Empress CAD/EP), and 1 yttria-stabilized zirconia (Y-TZP, Zenostar/ZS) were tested. Rectangular ceramic blocks were divided into 6 groups and subjected to different surface treatments: group Control (no treatment), group Uni (universal adhesive), group HF (hydrofluoric acid), group CoJet, group HF+Uni (HF and universal adhesive), and group CoJet+Uni (CoJet and universal adhesive). Subsequently, the specimens were cemented to composite resin blocks, sectioned into rectangular microbars of approximately 2×2×12 mm in size, and assigned to 2 groups with and without 100 000 thermal cycles (n=15 per group). The microtensile bond strength (μTBS) test was performed using a universal testing machine. Failure modes were observed with a stereomicroscope and scanning electron microscope (SEM). Three-way analysis of variance (ANOVA) followed by post hoc pairwise comparisons was performed to evaluate the effects of surface treatments, ceramics, and thermocycling on μTBS (α=.05). ResultsThe μTBS (MPa) was affected by the surface treatment (P<.001), ceramic type (P<.001), and thermocycling (P<.001). The bond strength after HF etching and universal adhesive treatment was highest in glass-ceramic groups (VS, CD, EP, and EM), while CoJet combined with universal adhesive indicated the highest bond strength in the ZS group before (34.3 ±4.2 MPa) and after thermocycling (16.0 ±2.9 MPa). No significant differences for μTBS were found among ZLS (VS and CD), lithium disilicate ceramic group (EM), and leucite-based ceramic group (EP, P>.05), but they demonstrated better bond strength than zirconia (ZS group, P<.01) after thermocycling. Adhesive failure increased in all groups, and the cohesive failure of glass-ceramic decreased after thermocycling. ConclusionsZLS showed similar μTBS with traditional glass-ceramics, including lithium disilicate ceramic and leucite-based ceramic, and more durable bonding than zirconia to resist thermocycling. Moreover, the combination of HF and universal adhesive treatments was the most effective method for ZLS among all the different surface treatments in this study.

On the durability of zirconia-reinforced lithium silicate and lithium disilicate dental ceramics under severe contact

Zirconia-reinforced lithium silicates (ZLS) are a novel generation of aesthetic, lithium-based ceramics intended for use in dental restorations at high loads due to their enhanced fracture strength compared to the previous lithium disilicate (LS2) materials. However, under severe dental conditions, material durability in service may be limited by wear from repetitive, frictional contacts. Here, a comparison is made between commercial ZLS and LS2 dental ceramics of their severe wear behavior under sliding contact against hard zirconia antagonists by means of in-vitro pin-on-disk tests. Specific wear rates greater than 10−6 mm3/N⋅m are obtained. The mechanisms responsible for material removal are a combination of deformation and fracture. Results are discussed in terms of the materials’ microstructure and mechanical properties. In combination with analytical modelling, ZLS dental ceramics are estimated to be up to 5 times less durable than LS2 under conditions modelling heavy chewing/bruxism. Finally, implications for the microstructural design of novel lithium silicate/disilicate materials with improved durability are considered.

FARKLI ŞEKİLLERDE POLİMERİZE OLAN İKİ REZİN SİMANIN DEĞİŞİK SERAMİK SİSTEMLER İLE ÜRETİLEN LAMİNATE VENEERLERİN BAĞLANMA DAYANIMLARINA ETKİSİ

Amaç: Bu çalışmanın amacı; ışıkla ve dual olarak polimerize olan iki rezin simanın farklı seramik sistemleri ile üretilmiş laminate veneerlerin mikroçekme bağlanma dayanımları üzerindeki etkilerini karşılaştırmalı olarak incelemektir. Yöntemler: Altmış maksiller santral diş mine-sement birleşiminin 2 mm apikalinden akrilik rezin içine gömüldü ve laminate veneer preparasyonları tamamlandı. Restorasyonların mum modelajları 3B yazıcı yardımıyla üretildi. Dişler rastgele 3 gruba ayrıldı (n = 20) ve lityum disilikat, yüksek yoğunluklu mikronize lityum disilikat ve zirkonya ile güçlendirilmiş lityum silikat seramiklerden restorasyonlar üretildi. Seramik örnekler ayrıca rezin siman tipine göre ışıkla polimerize ve dual polimerize rezin siman olarak 2 alt gruba (n = 10) ayrıldılar ve simantasyonları yapıldı. Daha sonra dişler 1 yıllık klinik kullanıma eşdeğer hızlandırılmış yapay yaşlandırmaya maruz bırakıldı. Her dişin kronunun tam ortasından 1’er tane mikrobar elde edildi (n = 10) ve örneklere kopma gerçekleşene kadar 0,5 mm/dk yükleme hızında çekme kuvveti uygulandı. İstatistiksel analizler iki yönlü varyans analizi ve Tukey's Post-hoc testi kullanılarak yapıldı (P ≤ ,05). Bulgular: Seramik ve rezin siman alt grubundaki örnekler karşılaştırıldığında aralarında istatistiksel olarak anlamlı fark bulunmuştur (P < ,001). Zirkonya ile güçlendirilmiş lityum silikat seramiklerin mikroçekme bağlanma dayanımları hem ışıkla polimerize olan hem de dual polimerize olan rezin siman gruplarında lityum disilikat seramiklere göre anlamlı seviyede düşük bulunmuştur (P < ,001). Dual polimerize olan rezin siman grubunun bağlanma dayanımı, ışıkla polimerize olan rezin siman grubundan istatistiksel olarak anlamlı seviyede düşük bulunmuştur (P < ,001). Sonuç: Lityum disilikat laminate veneerler, zirkonya ile güçlendirilmiş lityum silikat veneerlerden daha yüksek bağlanma dayanımı göstermiştir. Yine ışıkla polimerize olan rezin siman, dual polimerize olan rezin simana göre daha etkili bağlanma dayanımı sağlamıştır. Anahtar Kelimeler: Laminate veneer, lityum disilikat, mikro gerilim bağlanma dayanımı, rezin siman, zirkonya ile güçlendirilmiş lityum silikat Abstract Objective: The aim of this study was to compare the effects of two resin cements polymerized in different ways on the microtensile bond strength of laminate veneers produced with different ceramic materials. Methods: Sixty maxillary central incisor teeth were embedded in an acrylic resin 2 mm below the enamel-cement junction and laminate veneer preparations were completed. The wax models of the restorations were produced with a 3D printer. The teeth were randomly divided into 3 groups (n = 20) and restorations were produced with lithium disilicate, high-density micronized lithium disilicate and zirconia reinforced lithium silicate ceramics. Ceramic specimens were further divided into two groups (n = 10) according to the resin cement type as light-cure and dual-cure resin cement, and their cementation was performed. The teeth were then subjected to accelerated artificial aging equivalent to 1 year of clinical use. One microbar was obtained from the middle of the crown of each tooth (n = 10) and tensile force was applied to the specimens at a loading speed of 0.5 mm/min until the fracture occurred. Statistical analyzes were performed using two-way analysis of variance and Tukey's Post-hoc test (P ≤ .05). Results: Statistically significant difference was found between the ceramic type and resin cement subgroups (P < .001). The bond strength of laminate veneers produced with zirconia reinforced lithium silicate ceramic group was found significantly lower than that of lithium disilicate ceramic’s groups in both light-cured and dual-cured resin cement groups (P < .001). The dual-cure resin cement groups showed statistically significantly lower bond strength than the light-cure resin cement groups (P < .001). Conclusion: The laminate veneers fabricated from lithium disilicate ceramics showed higher bond strength than that of zirconia reinforced lithium silicate veneers. Also, the light-cure resin cement provided more effective bond strength than dual-cure resin cement. Keywords: Laminate veneer, lithium disilicate, microtensile bond strength, resin cement, zirconia reinforced lithium silicate

Comparison Of The Effect Of Surface Conditioning Methods On The Bond Strength Of Different Zirconia Reinforced Lithium Silicate And Hybrid Ceramics To Resin Cement

OBJECTIVE. The objective of this study was to evaluate the effect of surface conditioning methods on shear bond strength (SBS) of a resin composite bonded to CAD/CAM materials.&#x0D; &#x0D; METHODS. The zirconia-reinforced lithium silicate (Vita Suprinity VS, and Celtra Duo CD) and hybrid ceramics (Vita Enamic, VE and Nacera Hybrid NH) were used. 80 specimens from each material were fabricated following the manufacturer’s instructions and divided into 8 groups according to surface treatments. These were; Gr 1 (control, no treatments (K)), Gr 2 (hydrofluoric acid H), Gr 3 (H+ Silane S), Gr 4 (abraded with 50-micron alumina particles A), Gr 5 (A+ S), Gr 6 (abraded with 30-micron Cojet sand C), Gr 7 (C+S), Gr 8 (S). The average surface roughness (SR) of the specimens was measured. Surface treated specimens were cemented to the resin cement (Panavia F 2.0) for testing the adhesion using the shear bond strength SBS test and were tested. Mean SR and SBS results were analyzed by 2-way ANOVA with the material type and surface treatments as the independent variables. &#x0D; &#x0D; RESULTS. The highest surface roughness values were observed in the A and AS groups. Both hybrid ceramics VE and NH showed the highest SR values among surface treatments. The highest SBS values were found usually on the H and HS treated surfaces. The highest values were observed on the CD material in the HS group (18,01MPa) and followed by the VE material (16,25 MPa) in the CS group. The failure mode for CD and VS materials was found adhesive and cohesive failures and for VE and NH materials adhesive, and mixed cohesive failure was observed.&#x0D; &#x0D; CONCLUSION. The surface treatment showed a significant effect on the SR and SBS values. Although, the SR values of the materials are high in the A and AS group, the highest SBS values were observed in the H and HS treated surfaces.

Colour agreement between try-in paste and resin cement: effect of background on zirconia-reinforced lithium silicate.

To investigate colour agreement between different shades of Panavia V5 resin cement and their try-in pastes under zirconia-reinforced lithium silicate ceramics. Forty-four zirconia-reinforced lithium silicate ceramic specimens were prepared at 0.8 ± 0.01 mm thickness. Composite resin tooth-shaded background specimens were obtained in two shades. Resin cement specimens were fabricated at 0.1-mm thickness. Colour difference values (ΔE) between Aquagel and both the try-in paste and resin cement were calculated using the CIE-Lab system. The CIEDE2000 (ΔE00) colour formula was used to determine colour differences. The three-way ANOVA test and a multiple comparisons test were used for statistical analysis (α = 0.05). A statistically significant difference was found between the ΔE00 values obtained from the cement shade colour measurements for all specimens (P < 0.05). According to the three-way ANOVA test, lower ΔE00 values were observed in the try-in paste group compared to the resin cement group. The ΔE00 values were significantly affected by the cement shade and tooth-shaded background (P < 0.05). The colour agreement between the try-in pastes and the corresponding resin cement differed, and the try-in pastes could not mask the dark dental background as much as the corresponding resin cement.

Evaluation of Marginal and Internal Fit of CAD/CAM Endocrowns with Different Cavity Tapers.

To evaluate the effect of cavity tapering on marginal and internal adaptation of endocrowns fabricated from two different ceramic materials. Two mandibular molar model teeth were prepared with two different cavity tapers (5 and 10 degrees). A total of 40 endocrowns (four groups of 10 each) were milled using lithium disilicate and zirconia-reinforced lithium silicate ceramics for each cavity taper. The marginal and internal adaptation of endocrowns were measured by a stereomicroscope (×30) at 18 different points. The data were statistically analyzed using independent t test (P < .05). A statistically significant difference was shown among the tested groups at 10 degrees of taper (P < .001). At 5 degrees of taper, the difference was insignificant. The greatest internal gap was observed at the pulpal floor in all tested groups. All materials had clinically acceptable internal and marginal gaps; however, lithium disilicate ceramic had significantly better adaptation at 10 degrees of taper. Int J Prosthodont 2023;36:189-193. doi: 10.11607/ijp.6877.

Fracture strength of endodontically treated teeth restored with novel CAD/CAM ceramic post systems

Aim: The purpose of this study was to investigate the fracture strength (FS) and fracture types of endodontically treated teeth that restored with CAD/CAM made novel ceramic posts.Materials and Methods: Seventy human maxillary central incisors were selected, endodontically treated and expanded to 1.8 mm diameter with leaving of 2-3 mm canal filling. The teeth were randomly divided into 7 post restoration groups (n=10); a glass fiber post system as control (GFbr), monolithic zirconia (GMzr), lithium disilicate (GLds), zirconia-reinforced lithium silicate (GZr_Lds) ceramics, nanoparticle-filled (GRmc_Cer), resin nano-ceramic (GRmc_Lu), and polymer-infiltrated (GRmc_En) resin matrix ceramic groups. Then composite cores were build-up, crown restorations fabricated, and incubated in a water bath (37 ± 10C, 24 hours). A dynamic load was applied at 135° to the long axis of each specimen with a crosshead speed of 1 mm/min. FS and fracture types (favorable-catastrophic) were recorded. The FS values were statistically analyzed with one-way ANOVA and Tukey HSD tests (α=.05). Results: While the FS values of GMzr (365.62 ± 28.52 N) was significantly higher than GFbr (261.07 ± 24.51 N), all other groups (167.09-191.64 N) significantly lower, according to the Tukey HSD (P.05). Catastrophic fractures were observed only for GMzr. Conclusion: The results of this study suggest that the novel CAD/CAM ceramic materials substantially be suitable for the rehabilitation of severely damaged teeth with composite resin core build-up in the anterior region. However, only the monolithic zirconia post restorations may be more durable than the glass fiber post systems.

Impact of Chemical Aging on the Fracture Resistance of Two Ceramic Materials: Zirconia-Reinforced Lithium Silicate and Lithium Disilicate Ceramics

BACKGROUND: The reason for the development of high strength zirconia is that zirconia offers enough high strength of about 1000 MPa and high strength glass ceramic in the range of 360–400 MPa, to provide safely ceramic options for many indications.&#x0D; AIM: This study aims to evaluate the fracture resistance of zirconia-reinforced lithium silicate (ZLS) ceramic and lithium disilicate ceramic restorations.&#x0D; MATERIALS AND METHODS: In this in vitro study, forty crowns were fabricated by CAD/CAM technology, all samples were divided into two groups (n = 20) according to ceramic material used: Group Z ZLS ceramic (celtra due) and Group L lithium disilicate ceramic blocks (IPS E-MAX). Further subdivided into two subgroups according to the aging procedure (n = 10): (a) Subgroup – ZA: Aging. (b) Subgroup – ZB: No aging. (c) Subgroup – LA: Aging. (d) Subgroup – LB: No aging. All samples were subjected to universal testing machine (Instron) to evaluate the effect of the chemical aging on the fracture resistance.&#x0D; STATISTICAL ANALYSIS: One-way ANOVA analysis was used to compare measurements among groups.&#x0D; RESULTS: ZLS showed higher fracture resistance than lithium disilicate, but there was no statistical difference between them. Aging affected on the fracture resistance of two different ceramic materials but within an acceptable range.&#x0D; CONCLUSION: ZLS gave rise to higher fracture resistance than lithium disilicate and aging decrease fracture resistance of both types of ceramic. The postulated hypothecs of this study were zirconia reinforced, lithium silicate will be higher fracture resistance than lithium disilicate, and chemical aging will have a huge effect.