Lithium Disilicate Research Articles

Comparison of optical properties and bond strength of new CAD/CAM ceramic materials

Objective. To compare the shear bond strength values of current CAD/CAM materials and to evaluate the color changes resulting from immersion in coloring solutions. Material and Methods. A total of 160 specimens were prepared from 4 CAD/CAM blocks; lithium disilicate glass ceramic (IPS E.max CAD[EC]), zirconia reinforced lithium silicate ceramic (Vita Suprinity[VS]), polymer infiltrated glass ceramic (Vita Enamic[VE]) and hybrid ceramic (GC Cerasmart [GC]). The ceramic specimens were immersed in tea, coffee, cherry juice and distilled water solutions. Color measurements were made. To compare the shear bond strength values, all specimens were bonded to resin cement. Then the specimens were aged with 5000 thermocycling. The failure modes were classified according to stereomicroscope analysis and than scanning electron microscopy images for surface topography were obtained. Results. The color change values were significantly greater in coffee compared to other solutions and the highest color change was seen in GC and VE. The highest bond strength values were seen in VS and VE. The shear bond strength values are listed as follows: VS>VE>EC>CS. Conclusions. EC and VS can be used, especially in aesthetic restorations, due to their high color stability. Additionally, considering the bond strength values of VS, it appears to be a highly satisfactory material.

Long-Term Bonding Efficacy of CAD/CAM Hybrid Restorative Materials and Universal Adhesives.

In-office and lab milled prostheses are the staple for indirect restorations. It is therefore critical to determine their long-term bonding durability. CAD/ CAM blocks of two classes of restorative materials: 1) a nano-ceramic reinforced polymer matrix (NCPM) and, 2) a polymer-infiltrated ceramic network (PICN) were bonded using four different universal adhesives (UA) and silane systems. A lithium disilicate glassceramic (LDS) was used as a reference. The blocks were bisected and bonded with different UA/resin-cement pairs. Bonded blocks were then cut into 1.0x1.0x12.0 mm bar specimens for microtensile bond testing. Half the bars were subjected to bond strength testing immediately and the other half after aging by 50,000 thermal cycles between 5°C and 55°C. ANOVA and post-hoc tests were used to compare mean bond strength among groups. NCPM presented consistently high bond strength regardless of bonding techniques, while the bond strength of PICN and LDS were lower when bonded with UA relative to traditional silanes. The more hydrophilic UA produced higher bond strengths. Glass-ceramics exhibited lower bond strength with UA than the conventional etch-rinse-silane techniques. However, UAs preserved bonding interface in the long-term. NCPM displayed superior bond strength relative to PICN and LDS regardless of the type of adhesives and bonding techniques.

Clinical Success Evaluation of Ultrathin Ceramic Veneers Bonded to Nonprepared Teeth: An Observational Prospective Cohort Study.

Patients' increasing interest in achieving optimal cosmetic outcomes and the widespread use of ultrathin ceramic veneers offer advantages such as high esthetic results and long-term durability. Several issues related to tooth preparation have been raised, including dental sensitivity, periodontal diseases, and increased treatment phases, in addition to complications associated with previous procedures, the treatment of which remains controversial to date. With the advancement of dental ceramic and its manufacturing techniques, it was widely used to manufacture ultrathin ceramic veneers with minimal preparation. Issues such as fracture and abfraction are the most common in ceramic veneers made of feldspathic ceramic due to their weak mechanical properties against various forces, which led to the emergence of lithium disilicate glass-ceramic manufactured using the heat-press technique. This has resulted in ultrathin ceramic veneers with a thickness of up to 0.1-0.2 mm easily bonded and finished as they have high mechanical properties and esthetic qualities that mimic natural tooth color and shape. The current cohort study aimed to evaluate the success rates of this kind of treatment for patients treated at our department. This observational cohort study's sample comprised 60 ultrathin ceramic veneers manufactured from lithium disilicate glass-ceramic bonded to nonprepared upper teeth. The clinical performance of the studied sample was evaluated and monitored at monthly intervals (one month, three months, six months, and one year) using the clinical success evaluation based on Walton's principles adopted for evaluating the success and failure of fixed restorations. Ultrathin ceramic veneers made from lithium disilicate glass-ceramic, bonded to nonprepared teeth, proved to be a successful clinical and esthetic treatment option, with a clinical success rate of 100% during the entire follow-up period. This study's findings indicate that ultrathin ceramic veneers made from lithium disilicate glass-ceramic, bonded to nonprepared teeth, area successful clinical and esthetic treatment option, with a clinical success rate of 100% during the entire follow-up period.

Efficiency of dry versus wet Er,Cr:YSGG laser debonding of lithium disilicate veneers using different power outputs

Since water is the chromophore for the erbium, chromium-yttrium scandium gallium garnet (Er,Cr:YSGG) laser, the laser energy reaching the restoration decreases as part of it is absorbed by water. Theoretically, reducing the water or implementing dry debonding could reduce the energy consumed by water, increasing laser efficiency. Studies on whether it is suitable for removing veneers without using coolant are lacking. The purpose of this in vitro study was to evaluate the debonding time, intrapulpal temperature, and translucency of veneers during wet versus dry debonding with an Er,Cr:YSGG laser using different power outputs. Sixty-three maxillary central incisors were flattened labially to receive ceramic specimens. After cementation, ceramic specimens were irradiated with an Er,Cr:YSGG laser for debonding with different power outputs and water percentages (N=70): subgroup A1, 4W and 1% water; A20, 4W and 20% water; A40, 4W and 40% water; B1, 5W and 1% water; B20, 5W and 20% water; B40, 5W and 40% water; C1, 6W and 1% water; C20, 6W and 20% water; C40, 6W and 40% water, and a control group of unbonded ceramic specimens. During debonding, the temperature rise and debonding time were evaluated, followed by the evaluation of the translucency and surface topography of the debonded specimens. Two-way analysis of variance (ANOVA) and the Dunnett test were used to analyze the data (α=.05). The mean intrapulpal temperature rise varied significantly among groups B and C (P<.001), with the highest mean temperature rise found in subgroup B1 (4.00 ±0.00 ºC) and the lowest mean temperature rise in subgroup C20 (1.20 ±0.45 ºC). For the debonding time, the mean values of time required for debonding varied significantly among different groups (P<.001), with the longest time recorded in subgroup A1 (333.4 ±74.8s) and the shortest time recorded in subgroup C20 (17.0 ±6.0s). Only subgroups C1 (18.89 ±0.2) and C40 (18.60 ±0.2) showed a significantly lower translucency than the control group (19.44 ±0.06) (P<.001). Dry Er,Cr:YSGG laser debonding resulted in increased intrapulpal temperature when using high power outputs, but without exceeding the critical threshold of dental pulp temperature. Dry debonding also limited the transmission of laser energy, affecting the debonding efficiency. A power output of 5W and 20% water can be considered efficient and safe laser parameters for debonding lithium disilicate veneers if their reuse is intended.

Effect Of Adhesive Application Protocols On Bond Strength Of Ceramic Veneer Thickness

Aim: The aim of this study is to evaluate Shear Bond Strength of lithium disilicate ceramic veneers usingthree adhesive application protocols (pre-curing, co-curing and no adhesive application) using two resin cements (light cure total etch and dual cure self-etch). Material and Methods: By using CAD/CAM milling machine, 42 ceramic disc samples of dimensions 4X 4 mm in diameter and 0.5mm in thickness from Lithium disilicate ceramic material (Up-cad blocks). Buccal surface of 42 premolar teeth were flattened and etched then divided into 3 groups first group(P) received bonding agent then curing, second group (C) received bonding agent with no curing, third group(N)did not receive any bonding agent. Then each group is further subdivided into two subgroups according type of cement: light-cured luting cement total etch and a dual-cured self-adhesive resin cement.. All specimen underwent thermocycling aging and then shear bond strength test was carried out. A stereo microscope wasused to measure mode of failure of each specimen. Results: Regardless of type of cement co-curing application protocol had highest bond strength, followed by Noadhesive application protocol, while pre-curing application protocol had the lowest bond strength. Regardless of adhesive application protocol Self-etch dual-cured cement had a higher bond strength than the total-etch light-cured cement. While for mode of failure statistical analysis, there was no significant difference in adhesive application protocol and cement types. Conclusions: To Increase adhesive protocol the Co-curing is better than other methods. With regards toCement types, self-etch dual cure cement gave a more reliable bond than the total etch light cure cement

Evaluation of Cleaning Methods for Lithium Disilicate Ceramic Post Try-In Paste Application: An SEM Analysis.

This in vitro study assessed the efficacy of three cleaning methods on lithium disilicate ceramic after the application of different try-in pastes through SEM analysis. Ten rectangular specimens of IPS e.max CAD were prepared using a diamond disc, crystallized, etched with 5% hydrofluoric acid, and subjected to three try-in pastes-Calibra ©, Variolink (V), RelyX Veneer®-and three cleaning techniques-air-water spray (RD), ultrasonic bath in distilled water for five minutes (ULT/W), and ultrasonic bath in distilled alcohol for five minutes (ULT/A). A control specimen was also included. After one-minute paste application and subsequent cleaning method application, SEM evaluation was conducted. The results indicate that RD was as effective as CTRL in removing remnants from R-RD, V-ULT/W and V-ULT/A samples, but ineffective for all Calibra paste-contaminated specimens. In conclusion, the optimal removal of try-in paste residues from lithium disilicate restorations is paste-dependent; however, ultrasonic baths with distilled water or alcohol proved effective for most pastes tested.

The impact of Streptococcus mutans biofilms on the color stability and topographical features of three lithium disilicate ceramics.

Secondary caries around ceramic restorations is the most common reason for the replacement of fixed dental prostheses (FDPs). Therefore, it is important to examine the susceptibility of different ceramic materials to biofilm formation. This study aimed to evaluate biofilm development and associated roughness and color alterations in three lithium disilicate ceramics: Emax CAD (EC), Emax Press (EP), and LiSi Press (LP). Streptococcus mutans biofilms were grown on the three ceramics (n = 10 per group) for 7 days. Surface roughness values and color alteration were assessed before and after the biofilm using a non-contact profilometer and spectrophotometer, respectively. Biofilm growth was evaluated using colony-forming units (CFUs) and scanning electron microscope (SEM) images. The data were analyzed using one-way ANOVA and Tukey tests. There was a significant (p≤0.001) growth of S. mutans colonies on EC (6.75 ± 0.56) and EP (6.72 ± 0.54) specimens compared to LP, which showed no biofilm growth. The change in average surface roughness (∆Ra, nm) was significantly lower (p < 0.001) in the EC specimens (0.029 ± 0.003) compared to the EP (0.055 ± 0.012) and LP (0.041 ± 0.010). When the changes in the Rv and Rt values were investigated, no significant difference was observed among the groups. Following the biofilm challenge, the change in color (∆E00) was significantly lower (p = 0.005) in the LP group (1.68 ± 1.45) compared to the EC group (3.89 ± 1.50) and no significant difference was observed between the EP group (2.74±1.01) and the other two ceramics (p ≥ 0.05). LP ceramics exhibited superior resistance to S. mutans biofilm formation and associated changes in surface roughness and color compared to the Emax CAD and Emax Press ceramics. These findings suggest that the LiSi Press material may be more favorable to mitigate the risk of secondary caries.

Comparison of Mechanical Properties Between Zirconia-reinforced Lithium Silicate Glass-ceramic and Lithium Disilicate Glass-ceramic: A Literature Review

Lithium disilicate glass-ceramic (LDS) is increasingly being adopted for use in therapeutic restorative procedures. Concurrently, zirconia-reinforced silicate glassceramics (ZRS) are becoming broadly utilized in dental applications. The purpose of this study was to evaluate and compare the mechanical properties of zirconia-reinforced lithium silicate glass-ceramics and lithium disilicate-based glass-ceramics, with a focus on their application in CAD/CAM technologies. In this review, the researchers conducted a search of the PubMed (MEDLINE) database to identify studies related to LDS and ZRS. This search was limited to articles published in English over a seven-year period, from January 1, 2015, to December 31, 2022. Additional studies were sourced from Google Scholar and through manual exploration. Key published works were identified and included in the literature review. The findings concluded that ZRS exhibits superior mechanical properties, including higher flexural strength, fracture toughness, and hardness, compared to LDS. Furthermore, ZRS combines desirable esthetic qualities with robust mechanical strength, rendering it an excellent material for single tooth aesthetic restorations such as inlays, onlays, crowns, and veneers, applicable to both tooth and implant supports. Currently, there is a notable scarcity of data concerning the mechanical properties and clinical efficacy of ZRS. Therefore, it is imperative to conduct long-term clinical studies to verify the optical and mechanical properties, clinical applications, limitations, and long-term effectiveness of ZRS.

Shelf-life effect of silane-containing universal adhesive on bonding effectiveness to glass-ceramic

ObjectiveTo evaluate the shelf-life effect of a silane-containing universal adhesive (UA) on its shear bond strength (SBS) to lithium disilicate glass-ceramic (LiSi2). MethodsSBS to mirror-polished (‘MP’) and hydrofluoric acid-etched ground (‘HF’) lithium disilicate glass-ceramic (Initial LiSi, GC) with/without prior separate ceramic primer application (G-Multi Primer, GC: ‘G-MP’) was measured. Scotchbond Universal Plus (‘SBUp’) (3M Oral Care) was used 33 (‘fresh’) and 6 (‘expiring’) months before the expiration date. ‘MP’ specimen preparation involved (1) ‘G-MP’ priming (or not), (2) ‘SBUp’ application, (3) composite (Clearfil AP-X, Kuraray Noritake) placement, and (4) 20 s light-curing (SmartLite Pro, Dentsply Sirona). ‘HF’ specimen preparation involved (1) HF (Porcelain Etch, Ultradent) etching, (2) phosphoric acid (K-Etchant, Kuraray Noritake) post-etching, with (3) and (4) being the same as for ‘MP’. Upon light-curing, all specimens were stored in 37 °C water for either 1 week (‘immediate’) or 3 months (‘aged’) prior to SBS measurement. Statistics involved Linear Mixed-Effects modelling (α = 0.05). ResultsSBS was not significantly affected by SBUp's shelf life, except for a significantly higher SBS recorded for ‘fresh’ SBUp applied on HF-etched and separately silane-primed LiSi2. Aging did not significantly decrease SBS. In fact, a significant increase in SBS upon aging was recorded for HF-etched LiSi2 that was not separately silane-primed. The significantly highest bond strength was measured when LiSi2 was HF-etched followed by separate silane-priming. SignificanceDespite the UA investigated has silane in its formulation, the most effective and durable bonding to LiSi2 was achieved by HF-etching followed by separate silane-priming, irrespective of the UA's shelf life.

Three-Dimensional Optical Study on the Effects of Microwave Glazing on Surface Roughness of Zirconia-Reinforced Glass Ceramic.

BACKGROUND This 3-dimensional (3D) optical study aimed to evaluate the effects of microwave glazing on the surface roughness of zirconia-reinforced glass. Glazed surfaces of ceramic provide a smooth and esthetically superior restoration. There are many methods of glazing. However, this study aims to evaluate the effect of microwave glazing on ceramic restorations over conventional oven and hand polishing. MATERIAL AND METHODS A sample size of 90 ceramic material tiles was derived according to the standard sample size formula. The 3 dental ceramics used were IPS e.max CAD (lithium disilicate ceramic; IvoclarVivadent), Suprinity (zirconia-reinforced lithium silicate; VITA Zahnfabrik), and Celtra Duo zirconia-reinforced lithium silicate; Dentsply Sirona). Each group was further divided equally to undergo conventional oven glazing, hand polishing, and microwave glazing. The final glazed surfaces were then evaluated for surface roughness with the Ra parameter, using a Contour GT 3D Optical Microscope (Bruker) and 3D non-contact surface metrology with interferometry. RESULTS The ANOVA test for intergroup comparison showed microwave glazing was a significantly better glazing method than conventional oven and hand polishing (P<0.05). A statistically significant difference was shown between conventional and microwave glazing; however, the difference was greater between conventionally glazed and hand-polished specimens. Furthermore, a highly significant difference between microwave-glazed and hand-polished specimens was observed. CONCLUSIONS Results showed that irrespective of the ceramic, microwave-glazed ceramics were better than traditional oven-glazed ceramics, and hand-polishing resulted in a rougher surface than glazing. Irrespective of the surface treatment methods, IPS e.max CAD ceramic showed a relatively smoother surface than did Suprinity and Celtra Duo.

Impact of Er,Cr:YSGG Laser Debonding on the Mechanical Properties of Aged and Non-aged Lithium Disilicate Ceramics

Aim: The aim of this study is to evaluate the effects of Er,Cr:YSGG laser debonding on the mechanical properties of aged and non-aged lithium disilicate ceramics. Material and Methods: A total of 36 lithium disilicate samples with dimensions of 14x4x1 mm were prepared. Half of the samples underwent 5000 thermal cycles to simulate artificial aging. The aged and non-aged samples were divided into two subgroups: one subgroup was designated as the control group and did not receive laser treatment, while the other subgroup was treated with Er,Cr:YSGG laser for debonding (n=9). The flexural strength and modulus of the lithium disilicate samples were assessed using three-point bending tests before and after artificial aging. The surface roughness of a sample that did not undergo the three-point bending test was measured with AFM, its microhardness was assessed using Vickers hardness tests, and surface morphology was examined with FESEM. Two-way ANOVA and Bonferroni correction to determine the significance of the results were used for statistical analysis. Results: The results indicated that aging significantly reduced the flexural strength (p=0.031), however, laser debonding did not have a significant effect on the flexural strength or modulus of either aged or non-aged samples. Conclusion: Laser debonding effectively removes lithium disilicate restorations without compromising their mechanical properties, supporting their reuse in clinical practice. It is important to note that aging reduces the flexural strength of lithium disilicate ceramics.

Effectiveness of a silane coupling agent in a resin luting cement

The objective of this study was to investigate a new silane-containing self-adhesive resin luting cement with both shear bond strength and contact angle studies to determine if silane in a resin cement would chemically bond to a lithium disilicate surface. The silane-containing cement, Panavia SA Cement Universal (Kuraray, Tokyo, Japan) was tested against a control case where a traditional silane treatment was paired with resin-luting cement, Duo-Link Universal (Bisco Inc., Schaumburg, IL, USA) with immediate shear bond strength testing on both polished and etched lithium disilicate, as well as after thermocycling. It was determined that micromechanical retention provided a substantial contribution to bond strength. However, after an aging study with 20,000 thermocycles and then storage for 6 months in 37 °C water, the silane-containing, self-adhesive resin cement significantly decreased in shear bond strength when compared to the control. From contact angle studies, while it was shown that the paste containing the silane did effectively increase hydrophobicity of the treated lithium disilicate surface, it required over 3 h contact time, which was not representative of clinical use.

Effects of Artificial Aging of Direct Resin Nano-Hybrid Composite on Mean Bond Strength Values for Veneer Ceramic Samples.

BACKGROUND This study investigates the effect of artificial aging of direct resin nanohybrid composites on mean bond strength values for veneer ceramic samples. MATERIAL AND METHODS Ninety direct nanohybrid composite resin (Tetric N-Ceram) cylindrical discs were divided into 5 groups (n=18 each) based on aging cycles (thermocycling), as follows: TC=no aging (control), T1=850, T3=2500, T6=5000, and T12=10000 cycles, representing 1, 3, 6, and 12 months of clinical usage, respectively. Lithium disilicate glass ceramic (IPS e.max Press) cylindrical discs were cemented to resin discs using resin cement (Variolink N) after surface treatments (ceramic etching, silaning, composite abrasion). Differences in means between subgroups were calculated using one-way ANOVA, followed by the Tukey honestly significant differences post hoc test. Differences were considered statistically significant with a P value ≤0.05. RESULTS The highest SBS between ceramic and aged composite was observed at 1 month (m=20.35) but did not differ significantly from the control group (m=20.97). For all other subgroups (3, 6, 12 months) SBS was significantly less than that of the control (P≤0.05). At 1 and 3 months, cohesive failures were more common, whereas adhesive failures were more common in 6- and 12-month-old composites. CONCLUSIONS SBS of aged composites was less than that of non-aged composites, with SBS decreasing proportionally as the resin aged. When cementing a ceramic restoration over existing composite restorations, those older than 1 month should be removed and replaced with new ones.

Qualitative surface roughness of lithium disilicate endo-crown for pulpotomized primary molars

Rehabilitation of pulpotomized primary molars with an appropriate restoration is essential for recovering function and safeguarding the durability of the treatment. This study aimed to assess and compare the surface roughness of stainless steel (ST) crowns, zirconia (ZR) crowns, fiberglass (FG) crowns, and lithium disilicate (LD) endo-crowns as a restoration for pulpotomized primary molars also, evaluating the surface roughness of their antagonists. Sixty pulpotomized primary mandibular first molars were used for qualitative surface roughness evaluation and divided into four groups (n = 15/group) according to the crown type (group-ST, group-ZR, group-FG, group-LD). While the other sixty sound, unprepared primary maxillary first molars were used for evaluation of their surface roughness against the tested crowns. Specimens’ preparation and cementation were carried out according to each crown type and manufacturer’s instructions. The surface roughness was done using a two-body wear test. The data were statistically analyzed. All tested crowns showed an increased change in surface roughness, except group-ZR, which had the least change in surface roughness after mechanical wear with no statistically significant difference(P = 0.681). All crown types significantly increased the surface roughness of their antagonists after mechanical wear, except group-ST which showed insignificant affection (p ≥ 0.05). Zirconia crowns and lithium disilicate endo-crowns had the least change in surface roughness compared to other groups while SSCs showed the least tooth loss in the antagonist enamel.

Long-Term Bonding Performance of One-Bottle vs. Two-Bottle Bonding Agents to Lithium Disilicate Ceramics.

The aim of this study was to compare the long-term bonding performance to lithium disilicate (LDS) ceramic between one-bottle and two-bottle bonding agents. Bonding performance was investigated under these LDS pretreatment conditions: with hydrofluoric acid (HF) only, without HF, with a two-bottle bonding agent (Tokuyama Universal Bond II) only. Shear bond strengths between LDS and nine resin cements (both self-adhesive and conventional adhesive types) were measured at three time periods: after one-day water storage (Base), and after 5000 and 20,000 thermocycles (TC 5k and TC 20k respectively). Difference in degradation between one- and two-bottle bonding agents containing the silane coupling agent was compared by high-performance liquid chromatography. With HF pretreatment, bond strengths were not significantly different among the three time periods for each resin cement. Without HF, ESTECEM II and Super-Bond Universal showed significantly higher values than others at TC 5k and TC 20k when treated with the recommended bonding agents, especially at TC 20k. Difference in degradation between one- and two-bottle bonding agents containing the silane coupling agent was compared by high-performance liquid chromatography (HPLC). For both cements, these values at TC 20k were also not significantly different from pretreatment with only Tokuyama Universal Bond II. For LDS, long-term bond durability could be maintained by pretreatment with Tokuyama Universal Bond II instead of the hazardous HF.

Evaluation of vertical marginal discrepancy and load-to-failure of monolithic zirconia and lithium disilicate laminate veneers manufactured in different thicknesses

ObjectivesThis study aimed to evaluate the feasibility of monolithic zirconia laminate veneers (MZLV) compared to lithium disilicate laminate veneers (LDLV).Materials and methodsSixty resin replicas, each prepared with depths of 0.5 mm, 0.7 mm, and 1 mm, were produced using a 3D printer from acrylic teeth. Laminate veneers of these thicknesses were milled from pre-sintered monolithic zirconia (3rd generation) and lithium disilicate blocks. The intaglio surface of MZLV was treated with air abrasion using 110 μm diameter silica-modified aluminium oxide particles and ceramic primer, while LDLV was etched with etchant gel and treated with the ceramic primer before cementation with resin cement. Vertical marginal discrepancy (VMD) was assessed using a stereomicroscope, and a load-to-failure test was conducted using a universal testing machine. Failure modes were evaluated macroscopically on fractured surfaces. Data were analysed statistically using Two-way ANOVA and Bonferroni correction (α = 0.05).ResultsLDLV samples exhibited significantly larger VMD compared to MZLV samples across all thicknesses, especially in cervical, palatal, and mean data. Within the LDLV group, load-to-fracture values for 0.7 mm and 1.0 mm thicknesses were similar, whereas for 0.5 mm thickness, it was significantly lower. In the MZLV group, load-to-fracture values were lower for 0.7 mm and 1.0 mm thicknesses compared to LDLV, but higher for 0.5 mm thickness.ConclusionsMaterial choice and restoration thickness significantly influence laminate veneer restorations’ success. MZLV generally exhibits superior vertical marginal fit compared to LDLV, with varying load-to-failure values across different thicknesses. Clinical management of debonding in MZLV is simpler compared to restoration fracture in LDLV.Clinical relevanceConsidering clinical factors, MZLV may be a preferable option to LDLV for this restoration with the thickness of 0.5 mm.

Does the internal surface treatment technique for enhanced bonding affect the color, transparency, and surface roughness of ultra-transparent zirconia?

To investigate the effects of different surface treatments and thicknesses on the color, transparency, and surface roughness of ultra-transparent zirconia. A total of 120 Katana ultra-translucent multi-layered zirconia specimens were divided into 12 groups according to the thickness (0.3, 0.5, and 0.7mm) and surface treatment (control, airborne particle abrasion [APA], lithium disilicate coating, and glaze on). Color difference (ΔE00) and relative translucency parameter (RTP00) were calculated using a digital spectrophotometer. The surface roughness (Ra, Rq, Sa, and Sq) was measured using a non-contact profile scanner. The surface morphologies and microstructures of the samples were observed using a tungsten filament scanning electron microscope. Statistical analyses were performed by one-way and two-way analysis of variance (ANOVA) followed by post hoc multiple comparisons and Pearson's correlation (α = 0.05). The results showed that the surface treatment, ceramic thickness, and their interactions had significant effects on ΔE00 and RTP00 (p < 0.001). The surface treatment significantly altered the micromorphology and increased the surface roughness of the ceramic samples. APA exhibited the lowest transparency, largest color difference, and highest surface roughness. Zirconia with 0.3mm and 0.7mm thicknesses showed strong negative correlations between Sa and RTP00. The three internal surface treatments significantly altered the surface roughness, color difference, and transparency of ultra-transparent zirconia. As the thickness increased, the influence of the inner surface treatment on the color difference and transparency of zirconia decreased. For new zirconia internal surface treatment technologies, in addition to considering the enhancement effect on the bonding properties, the potential effects on the color and translucency of high-transparency zirconia should also be considered. Appropriately increasing the thickness of zirconia restorations helps minimize the effect of surface treatment on the optical properties.

Bond strength and surface roughness assessment of novel antimicrobial polymeric coated dental cement

Resin cement integrated with zein-incorporated magnesium oxide nanoparticles has previously been found to inhibit oral microbes and decrease bacterial biofilm. However, the bond strength and surface features of this biomaterial have yet to be investigated. The objective of this study was to evaluate the shear bond strength, mode of fracture, and surface roughness of resin cement modified with zein-incorporated magnesium oxide nanoparticles. Characterization of the cement was performed by X-ray diffraction, field emission scanning electron microscopy, and Fourier transform infrared spectroscopy. 126 human teeth were divided into 3 groups and cemented to lithium disilicate ceramic using resin cement with zein-incorporated magnesium oxide nanoparticles at concentrations of 0%, 1%, and 2% (n = 42). 21 samples of each group were subjected to the shear bond strength test, while the other 21 underwent thermocycling for 10,000 cycles before the test, after which all samples were evaluated for the mode of fracture. To assess surface roughness, resin cement disks were analyzed by a profilometer before and after undergoing thermocycling for 10,000 cycles. The shear bond strength of the cement with 1% and 2% nanoparticles was significantly higher than the control before thermocycling. The mode of fracture was found to be mainly adhesive with all groups, with the unmodified cement presenting the highest cohesive failure. There was no significant difference in surface roughness between the groups before or after thermocycling. The addition of zein-incorporated magnesium oxide nanoparticles to resin cement improved or maintained the shear bond strength and surface roughness of the resin cement.Graphical abstract

Comparative Invitro Testing of the Tensile Bond Strength Under Artificial Aging Between Different Lithium Disilicate Ceramics to Composite Substrate: A Novel Methodology.

Objective The purpose of this study is to compare the tensile bond strength values to composite substrate pre- and post-aging between IPS E.max CAD and Initial LiSi. Methods The study utilized four blocks of IPS E.max CAD LT/B1 C14 (Ivoclar Vivadent, Liechtenstein, Germany) (referred to as E) and four blocks of Initial LiSi LT/B1 (GC, Tokyo, Japan) (referred to as L). These blocks were milled to produce 76 ceramic bars measuring 2 mm × 2 mm × 10 mm (E = 38, L = 38/n = 19). After acid etching with hydrofluoric acid (BISCO, Schaumburg, IL, USA) and silane application (BIS-SILANE, BISCO), the specimens were embedded in putty (Express STD, 3M, Decatur, AL, USA) to create a mold for the resin cement (RelyX U200, 3M). Subsequently, one group of each brand underwent mechanical tensile testing (E0 and L0), while the other groups were subject to tensile testing after artificial aging involving 500 thermal cycles between 5 and 55°C (E5 and L5). The mean tensile strength for each group (E0, E5, L0, and L5) was determined using the Brown-Forsythe one-way ANOVA and Tamhane's post hoc tests. Results Initial LiSi showed a superior pre-aging mean (11.7 MPa). However, both materials had identical post-aging means (7.6 MPa). There were no statistically significant differences, except between the dependent Initial LiSi groups (L0-L5).Most failure modes were mixed (cohesive cement and adhesive). There were no cohesive failures on the cement side except in three specimens of Initial LiSi post-aging. Conclusion The tested conditions have shown that Initial Lisi exhibited the highest pre-aging mean; however, it exhibited inferior bond stability under aging conditions compared to IPS E.max CAD. Analyzing the microstructure before and after aging may provide insights into the greater decrease in bond strength observed in the Initial LiSi specimens.

Evaluating Retention of Onlay Versus Complete Coverage Using E.Max-Restoration

This study compared the retention of different types of indirect restorations (only or full coverage) utilized on endodontically treated molars. Fourteen patients requiring restoration of endodontically treated molars were randomly allocated into two groups (n = 7) according to the type of restoration used. lithium disilicate ceramic crowns were given to the control group. While lithium disilicate ceramic onlays were given to the intervention group. The heat pressing technique was used for the fabrication of both restorations. Following the final cementation with adhesive resin cement, the restoration was assessed at three, six, twelve, and twenty-four months using the modified USPHS criteria. Statistical analysis was performed using the chi-square test. Results: At all intervals, there was no statistically significant difference in retention (P &gt; 0.05) between the two tested groups. Both groups showed comparable results, with full coverage showing somewhat higher retention after 2 years. Regardless of the type of restoration, the emax-press produced high clinical performance in terms of retention. Compared to full coverage, onlay has proven to be a trustworthy substitute.