Zirconia-reinforced Lithium Silicate Research Articles

Effectiveness of Porcelain Polishing Methods on the Roughness and Color Stability of CAD-CAM Ceramics after Orthodontic Bracket Debonding.

Increased utilization of all ceramic restorations for aesthetic consideration in combination with routine adult orthodontic practice has led to numerous clinical challenges. Obtaining adequate bond strength between the orthodontic bracket and all-ceramic restoration and damage to the ceramic surface during the bracket debonding procedure needs to be better understood. This study analyzed the surface texture and color change of glazed and bracket-debonded ceramic CAD-CAM materials and the efficiency of porcelain polishing systems in restoring surface morphology and color. A total of 30 rectangular test specimens from each lithium disilicate CAD (LD-CAD), polymer-infiltrated ceramic (PICN), zirconia-reinforced lithium silicate glass ceramic (ZLS), and 5YTZP zirconia (5YZP) were prepared. The ceramic samples were embedded within acrylic resin, and baseline surface roughness and color were recorded using an optical profilometer and a reflected color spectrophotometer. The porcelain samples were bonded with lower incisor ceramic brackets. The samples were thermocycled 2000 times between 5 and 55 °C. Afterward, the brackets were peeled with bracket-removing pliers. The resin adhesive from the debonded surface was eliminated with tungsten carbide bur, and samples were randomly divided into three subgroups of (n = 10) to be polished with Diapol-twist (DT), a Keramik-Politur 4313B Komet polishing kit (KK), and a Horico diamond polisher (HDP). The polished surface roughness and color were recorded. The data were statistically analyzed using a two-way analysis of variance at p < 0.05. The debonded porcelain surfaces across the groups displayed significantly higher mean surface roughness (Ra) compared to glazed surfaces. The debonded 5YZP showed the least Ra at 0.661 (0.09), while the highest Ra was recorded by PICN at 4.057 (0.82). All of the polishing systems evaluated in the study significantly reduced the surface roughness. However, they were unsuccessful in regaining the surface topography of the glazed surface. The flexible discs (DT) produced the smoothest surface, followed by the diamond-impregnated rubber points (KK). Unpolished porcelain surfaces had a discernable mean color difference from glazed surfaces. Polished surfaces from the different polishing systems among the all-ceramic groups achieved a clinically acceptable mean color difference. Polishing debonded rough porcelain surfaces is imperative, and flexible discs performed better in all of the tested CAD-CAM ceramic materials.

Fracture Strength of Endocrowns Fabricated From Three Different Computer-Aided Design/Computer-Aided Manufacturing Ceramic Materials: An In-Vitro Study.

Endocrown restorations have increased in popularity in recent years due to the advancement of both adhesive and restorative materials. The clinical success of endocrowns depends on several factors, including preparation design, material selection, fracture resistance, and marginal adaptation. The aim of this in vitro study was to compare the fracture strength of endocrown restorations fabricated from three different computer-aided design (CAD)/computer-aided manufacturing (CAM) materials. Thirty extracted mandibular first molars were selected. The teeth underwent conventional root canal treatment before being prepared for endocrown restoration. The teeth were allocated to three groups (n=10), corresponding to each of the three ceramic materials used to fabricate the endocrowns they would receive. The ceramic materials used were zirconia-reinforced lithium silicate glass-ceramic (VITA Suprinity, VITA Zahnfabrik, Bad Säckingen, Germany), polymer-infiltrated hybrid ceramic (VITA Enamic, VITA Zahnfabrik, Bad Säckingen, Germany), and lithium disilicate glass-ceramic (IPS e.max CAD, Ivoclar Vivadent, Schaan, Liechtenstein). The specimens were scanned, and the digital impressions were transferred into design software to construct the endocrowns. The endocrowns were then milled and cemented. A universal testing machine (5969L3504, Instron, USA) was used for the fracture strength test at a crosshead speed of 1 mm/min until catastrophic failure occurred. Statistical analysis was performed using IBM Corp. Released 2015. IBM SPSS Statistics for Windows, Version 23.0. Armonk, NY: IBM Corp. The one-way analysis of the variance test indicated a significant difference in the fracture strength between the different ceramic groups tested (P=0.037). The Tukey posthoc test showed that the IPS e.max CAD group had marginally higher fracture strength values than the VITA Enamic group (P=055). No significant differences in fracture strength values were found between the VITA Enamic and VITA Suprinity groups or between the VITA Suprinity and IPS e.max CAD groups (P>0.05). The reported fracture strength values for all the tested materials were higher than the strength required to resist masticatory forces. Therefore, endocrowns fabricated using VITA Enamic, IPS e.max CAD, and VITA Suprinity CAD/CAM materials present restorations with a clinically acceptable fracture strength.

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.

Evaluation of Marginal Accuracy and Microstructure of Heat Pressed Lithium Disilicate and Zirconia Reinforced Lithium Silicate Crowns after Thermal Tempering

Evaluation of Marginal Accuracy and Microstructure of Heat Pressed Lithium Disilicate and Zirconia Reinforced Lithium Silicate Crowns after Thermal Tempering

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.

A Comparative Study of the Marginal Fit of Endocrowns Fabricated From Three Different Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) Ceramic Materials: An In Vitro Study.

The marginal seal and adaptation are important factors for successful restoration. An inadequate marginal seal can lead to bacterial microleakage, plaque accumulation, and eventually treatment failure This in vitro study aimed to compare the marginal gap of endocrowns fabricated from three different computer-aided design/computer-aided manufacturing (CAD/CAM) ceramic materials. Thirty extracted mandibular molars were selected for the study. Endocrown preparations were completed after root canal treatment. Teeth were divided into three groups to receive endocrowns fabricated of lithium disilicate ceramic (IPS-e.max CAD, Ivoclar Vivadent AG, Schaan, Liechtenstein), zirconia-reinforced lithium silicate ceramic (VITA Suprinity®, VITA Zahnfabrik, Bad Säckingen, Germany), and polymer-infiltrated ceramic (VITA Enamic®, VITA Zahnfabrik). The digital impressions were transferred to the design software to construct the endocrowns. The endocrowns were milled and cemented. The marginal fit was examined using a digital camera stereomicroscope at a magnification of 80X. Images were transferred to Image-J software (National Institutes of Health, Bethesda, Maryland, United States) to measure the marginal gap. One-way ANOVA showed a significant difference in the marginal gap between the different ceramic groups (P=0.006). Tukey's Honest Significant Difference (HSD) post-hoc test showed that VITA Suprinity had significantly higher gap width values than VITA Enamic (P=0.005). No significant differences in gap width values were found between VITA Enamic and IPS e.max CAD or between VITA Suprinity and IPS e.max CAD (P>0.05). The marginal gap of endocrown restorations varies with different CAD/CAM materials (zirconia-reinforced lithium silicate glass-ceramic, polymer-infiltrated hybrid ceramic, and lithium disilicate glass-ceramic), but are all within clinically acceptable marginal gap width.

Clinical outcome of CAD/CAM overlays of MIH affected young permanent molars

BackgroundRestoration of first permanent molars with MIH is considered a challenge for dentists because the enamel has less flexibility and hardness with increased porosity and organic content. Materials and methodsThe current study was a randomized control trial in which fifty-two first permanent molars were distributed equally into two groups (Z) teeth that received zirconia overlays and (EC) teeth that received IPS e.max CAD overlays. Clinical assessments were carried out at baseline, 6, and 12 months using modified FDI World Dental Federation criteria. ResultsAfter the observational period of one year, all restorations were still in function with no significant differences in the esthetic, functional, and biological performance of overlays fabricated with zirconia and IPS e.max CAD except one case have been fractured in the group (EC) and three cases have been de-bonding in the group (Z). ConclusionsUsing monolithic zirconia and IPS e.max CAD overlays could be a viable selection for restoring MIH-affected posterior teeth. In further studies, it is advisable to assess the restoration that combines strength with adhesive properties like zirconia-reinforced lithium silicate glass ceramic restoration.

Effect of staining layer on roughness after progressive wear of monolithic ceramics.

The aim of this study was to evaluate staining layer behavior applied to high-translucency zirconia (YZHT), feldspathic ceramics (FD), and zirconia-reinforced lithium silicate (ZLS) surfaces against different antagonists. Monolithic ceramic discs (n = 120) (ø 12 mm; thickness, 1.2 mm; ISO 6872) were obtained, 30 from YZHT and FD, and 60 from ZLS CAD/CAM blocks (staining layer applied before or after the crystallization procedure). The specimens were divided into 12 subgroups (n = 10) according to the antagonists: steatite, polymer-infiltrated ceramic, or zirconia. Mechanical cycling (1.5 × 104 cycles; 15 N; horizontal displacement, 6 mm; 1.7 Hz) and flexural strength tests (1 mm/min-1000 kg cell) were performed. The differences between final and initial roughnesses (Ra, Rz, and Rsm), the mass loss, and the flexural strength data were individually analyzed by two-way ANOVA and Tukey's test (α = 0.05). The roughnesses of all ceramics did not present a statistically significant difference before wear simulation: Ra (p = 0.3348), Rz (p = 0.5590), and Rsm (p = 0.5330). After the wear simulation, the Ra parameter was not affected by an interaction between ceramic and antagonist (p = 0.595). The Rz and Rsm parameters were affected only by the antagonist pistons (both, p = 0.000). The ceramics used in this study showed statistically significant differences in mass loss after the wear test (p < 0.0001). The additional firing (2 steps) of the ZLS2 led to a higher lost mass quantity. All ceramics presented similar initial roughnesses and similar roughnesses after the wear simulation. The zirconia antagonist showed better performance against ceramics with high crystalline content. It is clear that restorative materials must be carefully selected by dental practitioners according to indications, properties, and antagonists. The steatite antagonist, that is, an enamel analog, showed better performance against vitreous ceramics, while the zirconia antagonist showed better performance against ceramics with high crystalline content. Wear affects the surface roughnesses of the ceramics. Additional firing for the staining of the zirconia-reinforced lithium silicate ceramic led to a greater loss of mass.

Wear characteristics of esthetic resin matrix and zirconia reinforced lithium disilicate CAD/CAM materials: two-body wear and surface topography analysis.

This in vitro study assessed the wear behavior of different CAD-CAM blocks and the abrasion of the enamel antagonist against these materials. 64 disk-shaped specimens were prepared from 8 different CAD/CAM blocks as follow: one lithium disilicate glass ceramics block "IPS Emax CAD" as control group, two zirconia reinforced lithium silicate "Vita Suprinity & Celtra DUO," one interpenetrating network ceramic block "Vita Enamic," Three resin-based block composites "Lava Ultimate, Cerasmart & Brilliant-crios" as well as one hybrid nanoceramic "Shofu block HC". All specimens were mounted against canine and tested for two body wear analysis using a chewing simulating loading machine (100,000 cycles, 50 N, 5/55 °C). The amount of wear loss was measured for each specimen using a digital precise scale. Wear area before and after the chewing simulation were evaluated using an optical profilometer. Data analysed using one-way ANOVA test followed by Tukey's post hoc. The results showed a significantly higher wear loss in resin matrix ceramics in comparison to glass ceramics. However, for tooth wear glass ceramics had significantly higher value than hybrid ceramics. Resin based CAD/CAM Blocks gives a superior result when evaluating the wear behavior and its effect on the opposing tooth surface.

Glass ceramics behave like selectively etched enamel on interfaces produced with self-adhesive/ self-curing resin cement

This work aimed at analyzing the bond strength of different ceramic compositions and dental substrates to a self-adhesive/curing resin cement to determine the reliability of the bonded interfaces. The study groups were Lithium Disilicate (LD), Zirconia reinforced Lithium Silicate (ZLS), Conventional Yttria-stabilized Polycrystalline Tetragonal Zirconia (Y-TZP C), Translucent Yttria-stabilized Polycrystalline (Y-TZP T), Selective Etched Enamel (E + E); unetched Enamel (E); and Dentin (D). Twenty 2 mm thick slice specimens of each group were obtained from a cutting machine, under high speed and refrigeration, followed by polishing and inclusion in PVC tubes with acrylic resin, with their flat surfaces exposed. The self-adhesive/curing resin cement was inserted in a plastic matrix on the surface of each specimen, resulting in cylinders with an internal 1.40 mm diameter x 1 mm height. The specimens were subjected to microshear bond strength test. Qualitative failure analysis was performed by stereomicroscope and scanning electron microscope (SEM). Weibull statistical analysis was performed to obtain the following metrics: probability of failure, Weibull modulus (m) (reliability) and characteristic strength (σ0). The E + E group achieved the highest median value (24.88 MPa), lower probability of failure, greater reliability, and greater characteristic strength among all the study groups. ZLS presented the highest bond strength values (20.07 MPa) and characteristic strength but also the highest data variability. LD group presented greater reliability among ceramic materials. Dentin presented the lowest median (4.51 MPa) among all substrates evaluated. The adhesive failure mode was predominant among the failure types. Adhesive interfaces of glass ceramics presented higher characteristic strength, lower probability of failure and greater reliability, being similar to selectively etched enamel.

Effect of incisal preparation design on the fracture strength of monolithic zirconia-reinforced lithium silicate laminate veneers.

This study aimed to assess the fracture resistance of monolithic zirconia-reinforced lithium silicate laminate veneers (LVs) fabricated on various incisal preparation designs. Sixty maxillary central incisors with various preparation designs were 3D-printed, 15 each, including preparation for: (1) LV with feathered-edge design; (2) LV with butt-joint design; (3) LV with palatal chamfer; and (4) full-coverage crown. Restorations were then designed and manufactured from zirconia-reinforced lithium silicate (ZLS) following the contour of a pre-operation scan. Restorations were bonded to the assigned preparation using resin cement and following the manufacturer's instructions. Specimens were then subjected to 10,000 thermocycles at 5 to 55°C with a dwell time of 30s. The fracture strength of specimens was then assessed using a universal testing machine at a crosshead speed of 1.0mm/min. One-way ANOVA and Bonferroni correction multiple comparisons were used to assess the fracture strength differences between the test groups (α=0.001). Descriptive fractographic analysis of specimens was carried out with scanning electron microscopy images. Complete coverage crown and LV with palatal chamfer design had the highest fracture resistance values (781.4±151.4 and 618.2±112.6N, respectively). Single crown and LV with palatal chamfer had no significant difference in fracture strength (p>05). LV with feathered-edge and butt-joint designs provided significantly (p<05) lower fracture resistance than complete coverage crown and LV with palatal chamfer design. The fracture resistance of chairside milled ZLS veneers was significantly influenced by the incisal preparation designs tested. Within the limitation of this study, when excessive occlusal forces are expected, LV with palatal chamfer display is the most conservative method of fabricating an indirect restoration.

Effect of Different Scaling Methods on the Surface Topography of Different CAD/CAM Ceramic Compositions.

This study evaluated the effect of ultrasonic and manual scaling using different scaler materials on the surface topography of computer-aided designing and computer-aided manufacturing (CAD/CAM) ceramic compositions. After scaling with manual and ultrasonic scalers, the surface properties of four classes of CAD/CAM ceramic discs: lithium disilicate (IPE), leucite-reinforced (IPS), advanced lithium disilicate (CT), and zirconia-reinforced lithium silicate (CD) of 1.5 mm thickness were evaluated. Surface roughness was measured before and after treatment, and scanning electron microscopy was used to evaluate the surface topography following the performed scaling procedures. Two-way ANOVA was conducted to assess the association of the ceramic material and scaling method with the surface roughness. There was a significant difference in the surface roughness between the ceramic materials subjected to different scaling methods (p < 0.001). Post-hoc analyses revealed significant differences between all groups except for IPE and IPS where no significant differences were detected between them. CD showed the highest surface roughness values, while CT showed the lowest surface roughness values for the control specimens and after exposure to different scaling methods. Moreover, the specimens subjected to ultrasonic scaling displayed the highest roughness values, while the least surface roughness was noted with the plastic scaling method.

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

The Effect of Thermal Tempering on Fracture Resistance and Surface characterization‏ of Lithium Disilicate and Zirconia Reinforced Lithium Silicate Crowns

The Effect of Thermal Tempering on Fracture Resistance and Surface characterization‏ of Lithium Disilicate and Zirconia Reinforced Lithium Silicate Crowns

Effect of surface finish and acidic medium on hardness and fracture toughness of zirconia reinforced lithium silicate (An In-vitro study)

Effect of surface finish and acidic medium on hardness and fracture toughness of zirconia reinforced lithium silicate (An In-vitro study)

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.

Comparison and Effect of Common Beverages on Color Stability of Different Esthetic Restorative Materials: An In Vitro Study.

The aim of this in vitro study is to assess the color stability of different esthetic veneer restorative materials (feldspathic ceramic, hybrid ceramic, zirconia-reinforced lithium silicate glass ceramic, and composite resin) after being exposed to commonly consumed beverages that have staining potential. Sixty specimens were prepared into rectangular blocks with fixed dimensions of 10 × 12 × 2.5 mm. Machinable feldspathic ceramic (FC), zirconia-reinforced lithium silicate glass ceramic (LS), and a hybrid ceramic (HC) were milled using CAD/CAM (n = 15), and specimens of microparticle composite resin (MPC) were manually prepared by with the same dimensions (n = 15). All specimens were randomly divided into three subgroups (= 5) according to immersing solutions used (coffee, black tea, and red wine). All specimens were immersed for a period of 72 hours. A colorimetric evaluation was done for each specimen before and after immersion using a spectrophotometer and the difference in color was calculated according to the CIE-Lab system. To analyze the data, two-way ANOVA and one-way ANOVA tests of significance were used to compare between the different study groups, followed by pairwise comparisons using post hoc test (Tukey). Different restorative materials showed statistical significance regarding color change after staining (p < 0.001); however, no statistical significance in color change (p > 0.05) was found between the different beverages used. All tested ceramic materials had better color stability compared with composite resin. All the staining beverages used in the current study might cause a significant color change in the tested restorative materials. The color stability of esthetic restorative materials affects their clinical performance in the oral cavity, where the restorative materials are usually exposed to staining beverages that are frequently consumed by patients. Therefore, it is important to understand the staining effect of the different beverages on esthetic restorative materials.

Effects of repetitive firings on mechanical, optical, and phase formation changes of ceramic materials

Statement of problemStudies are sparse on how rapid heating and cooling negatively affect optical properties, including color and transparency, and mechanical properties, including hardness and durability, that affect esthetics and shorten the clinical usage period of the ceramics. PurposeThe purpose of this in vitro study was to determine the effects of repeated firing on the color difference, mechanical properties, and phase formation of different ceramic materials. Material and methodsA total of 160 disks (12×1.35 mm) were produced from 4 different ceramic materials: lithium disilicate glass-ceramic, zirconia-reinforced lithium silicate ceramic, zirconia core, and monolithic zirconia. Specimens from all groups were divided into 4 groups (n=10) with a different number of veneer porcelain firings (1 to 4) by simple randomization. After the firings, color measurement, X-ray diffraction analysis, environmental scanning electron micrograph analysis, surface roughness evaluation, Vickers hardness evaluation, and biaxial flexural strength tests were performed. Data were analyzed with analysis of variance (2-way ANOVA) (α=.05). ResultsRepeated firing did not affect the flexural strength of the specimens in any of the groups (P>.05), while the color, surface roughness, and surface hardness were significantly affected (P<.05). The specimens fired 4 times showed the highest mean Vickers hardness and ΔE00 values but the lowest mean surface roughness values. Zirconia core specimens showed the highest mean ΔE00 and flexural strength values, and lithium disilicate glass-ceramic specimens had the highest mean Vickers hardness values. ConclusionsThe increase in the number of firings affected the color, mechanical properties, and phase formation of the specimens; this change differed according to the ceramic tested.

Effects of 16% Carbamide Peroxide on Optical Properties of Thermally Aged Monolithic CAD-CAM Glass Ceramics with Different Surface Treatments.

This study aimed to investigate the effects of 16% carbamide peroxide (CP) on the relative translucency parameter (RTP) and color stability of thermally aged CAD-CAM glass-ceramics with glazing or polishing. Three different CAD-CAM blocks-feldspathic (VM), lithium disilicate (IPS), and zirconia-reinforced lithium silicate ceramic (VS)-were used in this study. The specimens were divided into two groups (n=10) according to surface treatments (glazing or polishing). Bleaching treatment with 16% CP was applied to the thermally aged specimens. A spectrophotometer (VITA Easyshade Advance) was used to measure the CIE L*a*b*coordinates of the specimens on white and black backgrounds, and RTP and color difference (ΔE00) values were calculated. The surface topography of the specimens and the atomic weight of the elements were analyzed with scanning electron microscopy and energy-dispersive x-ray. The data were analyzed by using the two-way ANOVA test for ΔE00 values and two-way repeated measures ANOVA test for RTP and color parameters values (a=0.05) and the Tukey post-hoc test was used for multiple comparisons of the groups. RTP values were statistically influenced by material type, bleaching, and finishing technique, and the interaction among these factors was found to be significant (p<0.05). ΔE00 values were statistically influenced by material type, finishing technique, and the interaction among these factors was also found to be significant (p<0.05). IPS presented significantly lower RTP and ΔE00 values for both glazed and polished surfaces (p<0.05). 16% CP bleaching agent caused changes in translucency of aged VM and IPS at different levels. Glazed surfaces presented higher color stability in comparison to mechanically polished surfaces for VS (p<0.05).

Repair bond strength of different CAD-CAM ceramics after various surface treatments combined with laser irradiation.

The aim of this study was to evaluate the effect of different surface treatments combined with laser irradiation on the shear bond strength of different CAD-CAM ceramics to composite resin. A total of hundred forty-seven ceramic specimens with thicknesses of 2.5mm were prepared from three different CAD-CAM ceramics (an yttrium oxide partially stabilized tetragonal zirconia polycrystal (Y-TZP); a zirconia-reinforced lithium silicate glass ceramic (ZLS); and a lithium disilicate-strengthened lithium aluminosilicate glass ceramic (LD-LAS)) and subjected to seven groups of treatment (n = 7): (1) control (no treatment), (2) Er:YAG laser irradiation, (3) Nd:YAG laser irradiation, (4) etching with hydrofluoric acid (HFA), (5) Er:YAG + HFA, (6) Nd:YAG + HFA, and (7) sandblasting. After surface treatment procedures, a ceramic primer (Clearfil Ceramic Primer Plus, Kuraray, Japan) was applied to the ceramics. Bonding agent (Single Bond Universal Adhesive, 3M ESPE, USA) was then applied, and the composite resin (Estelite Sigma Quick, Kuraray, Japan) was layered on the ceramic surfaces. The shear bond strength test was performed using a universal testing machine at a load of 0.5mm/min. Data were analyzed by 2-way analysis of variance (ANOVA), and the Bonferroni correction was used for pairwise comparisons (α = 0.05). Compared to the bond strength of the control group, irradiation by Er:YAG and Nd:YAG lasers alone improved the bond strength of the composite resin to the Y-TZP (P < 0.001) but did not change the bond strength of composite resin to the ZLS and LD-LAS (P > 0.05). Compared to the bond strength of the control group, etching with HFA alone increased the bond strength of the composite resin to the ZLS and LD-LAS (P < 0.001) but did not affect the bond strength of the composite resin to the Y-TZP (P > 0.05). The highest bond strength of ZLS was obtained using HFA + Er:YAG, and the highest bond strength for LD-LAS was obtained using HFA + Nd:YAG. It was concluded that Er:YAG and Nd:YAG laser treatments presented the highest repair bond strength between the composite resin and Y-TZP ceramics. Er:YAG and Nd:YAG laser treatments in conjuction with HFA presented the highest repair bond strength between the composite resin and the glassy ceramics, ZLS, and LD + LAS.