Lithium Disilicate Specimens Research Articles

Can a Self-etching Primer be Effective in Bonding Aligner Attachments to Different Types of Ceramics?

This in vitro study aimed to evaluate the effectiveness of pretreatment with a self-etching primer for bonding aligner attachments to lithium disilicate (LD) and monolithic zirconia (MZ) ceramics. Forty ceramics, including LD (n=20) and MZ (n=20), were divided into four study groups according to the surface pretreatments: LD specimens pretreated with universal primer (Monobond Plus, MP) after hydrofluoric acid etching (Group 1); MZ ceramics pretreated with MP after sandblasting (Group 2); LD ceramics pretreated with self-etching ceramic primer (Monobond etch & prime, MEP) (Group 3); and MZ ceramics pretreated with MEP after sandblasting (Group 4). The aligner composite (GC Aligner Connect) and universal adhesive (GPremio Bond) were used to prepare the resin attachments. The bond strength was evaluated by micro-shear bond strength (SBS) testing (0.1 mm/min) after thermocycling, and the remnant adhesive was scored according to the resin attachment remnant index (RARI). The SBS data were analyzed using ANOVA and Tukey tests, and the RARI scores were analyzed using the chi-square test. Group 1 had the lowest SBS, and group 2 had the highest SBS. There were significant differences between the groups in terms of bond strength (p<0.05). The RARI scores showed no significant differences, regardless of the pretreatment and ceramic type. The use of a self-etching primer increased the bond strength of resin attachments on LD ceramics. For zirconia ceramics, both ceramic primers are recommended for aligner attachment bonding.

Shear bond strength of MDP-containing light-cured veneer adhesive system to zirconia with different surface preparations

This study aimed to evaluate the effects of different surface preparation techniques on the surface microstructure, the shear bond strength (SBS) between zirconia and an MDP-containing light-cured veneer adhesive system, and the adhesive failure mode. Sixty-four zirconia specimens were divided into four groups based on surface preparation methods (n = 16), including zirconia sandblasting (ZSB), zirconia vitrification or glaze-on (ZVG), zirconia surface architecture technique (ZSAT), and ZSAT-ZVG combined technique (ZSATVG) groups. Sixteen lithium disilicate specimens prepared by etching with hydrofluoric acid (HF) were used as a positive control group (LDE). Surface roughness measurement and scanning electron microscopy (SEM) evaluation were performed before and after surface preparation. All specimens were then bonded with an MDP-containing light-cured adhesive system, followed by SBS testing and adhesive failure mode analysis. The ZVG and ZSATVG groups showed the greatest differential roughness value and microscopic irregularities, while the ZSAT and LDE groups had the least surface change but the most micromechanical retentive structures for resin infiltration. SBS values were significantly different among groups (p < 0.001) with the highest SBS observed in the ZSAT group, followed by the ZSB group, LDE group, ZSATVG group, and lastly, the ZVG group. There was a statistically significant difference in failure types among the surface preparation groups (p < 0.001). The ZSAT group had the highest frequency of mixed failure, followed by the ZSB group, LDE group, and the ZSATVG and ZVG groups. Establishing direct micromechanical retention within zirconia itself yields a higher bond strength than indirect micromechanical retention within a glass ceramic layer.

Masking capacity of minimally invasive lithium disilicate restorations on discolored teeth-The impact of ceramic thickness, the material's translucency, and the cement color.

To evaluate minimally invasive restorations' capacity to mask discolored teeth and explore the impact of ceramic thickness, translucency, and cement color. Twenty-four assessment pairs of naturally colored and discolored bovine dentin samples were formed, using lithium disilicate specimens in six different thicknesses (0.3-0.8 mm), two different translucencies (high, low), and two cements (transparent, tooth-colored). Evaluators assessed the color differences in each assessment pair, and the threshold for detecting a color difference was determined using sequential testing and the Bonferroni-Holm method. A thickness of 0.6 mm effectively masked color differences using high translucent ceramic with transparent cement, detectable differences were still observed at 0.7/0.8 mm. A threshold thickness of 0.4 mm was seen using high translucent ceramic and tooth-colored cement, with color differences still discernible at 0.5 and 0.8 mm. A threshold thickness of 0.4 mm was detected using low translucent ceramic and transparent cement, while detectable differences persisted at 0.5, 0.7, and 0.8 mm. A 0.5 mm threshold thickness was observed when using low translucent ceramic and tooth-colored cement, and no detectable color differences were detected beyond this thickness. Masking can be achieved with a thickness of 0.4-0.5 mm using a low translucent material and tooth-colored cement. Understanding the impact of ceramic thickness, translucency, and cement color can aid clinicians in making informed decisions for achieving the best esthetic outcomes while preserving tooth structure. Effective masking can be accomplished with ceramic thicknesses starting at 0.4 mm, especially when employing a low translucent material and tooth-colored cement. However, clinicians should be aware that discolorations may still be detectable in certain scenarios when using minimally invasive lithium disilicate restorations.

Effects of Ceramic Translucency and Thickness on Polymerization of a Photosensitive Resin Cement

We investigated the effects of lithium disilicate ceramic thickness and translucency on the degree of polymerization of light-cured resin cement using the measure of hardness. Lithium disilicate specimens of three translucencies (low, medium and high) were prepared to four thicknesses (0.5, 1.0, 2.0 and 3.0 mm). A light-cured resin cement was cured through each of the ceramic specimens using a handheld curing light for 50 s. A 3D printed jig was used to achieve a uniform thickness of the resin cement. Directly cured resin cement was used as the control. Hardness was measured using nano-indentation to determine the degree of polymerization of the resin cement. Two-way ANOVA and Tukey post hoc tests were used to evaluate interaction between translucency and thickness. Hardness values from control specimens were assessed using the two-tailed t-test with the Bonferroni approach. The translucency of the specimens significantly influenced the hardness (p &lt; 0.001), where a negative linear relationship between cement hardness and ceramic thickness was present for low translucency and high translucency. However, at a 0.5 mm thickness, all specimens showed similar hardness regardless of the translucency. The translucency of ceramics affected the hardness, and hence polymerization, of light-cure resin cement. However, the effect of increased thickness was a more significant factor.

Wear of lithium disilicate opposed by various ceramic materials.

To compare volumetric wear of lithium disilicate against different ceramic (3 mol% yttria-stabilized (3Y) zirconia, 5 mol% yttria-stabilized (5Y) zirconia, lithium disilicate, porcelain and enamel antagonists). Forty lithium disilicate (e.max CAD) specimens (n = 8/antagonist) were wet sanded to 1200grit SiC and mounted into a UAB wear device. Antagonist spheres (diameter = 4.75 mm) were made from polished 3Y zirconia, 5Y zirconia, lithium disilicate, porcelain and human enamel. A two-body wear test was performed with 20 N load and 1.5 mm slide for 400,000 cycles at 1 Hz. 33% glycerin was used as a lubricant. Wear facets were measured with optical profilometry. Wear scar areas of antagonists were measured with digital microscopy. Scanning electron microscopy was performed on wear facets and scars. Vicker's microhardness was measured of all antagonist materials. All data were compared with 1-way ANOVA and Tukey post-hoc analysis. Significant differences in lithium disilicate volumetric wear (mm3 ) occurred with various antagonist materials: 0.38 ± 0.01a (3Y zirconia), 0.33 ± 0.01b, (5Y zirconia), 0.16 ± 0.01c (lithium disilicate), 0.11 ± 0.03d, (enamel), and 0.07 ± 0.01e (porcelain). The lithium disilicate antagonist demonstrated a larger wear scar than other materials. Zirconia was the hardest material and enamel the least hard. Zirconia causes significant wear on lithium disilicate and lithium disilicate causes significant wear against itself. When selecting a material to oppose an existing lithium disilicate crown, a porcelain or lithium disilicate surface would cause significantly less wear to the existing crown. If an existing zirconia crown exists opposed to a prepared tooth, lithium disilicate may not be an ideal material selection to restore the tooth.

Evaluation paste removal method and bond strength between resin cement and lithium disilicate ceramic: An in vitro study

Statement of problemAfter the use of evaluation paste, residue can remain on the bonding surface. However, how adhesion to lithium disilicate ceramic is affected is unclear. PurposeThe purpose of this in vitro study was to determine the effectiveness of lithium disilicate cleaning after contamination with an evaluation paste and before the application of a resin cement. Material and methodsRectangular lithium disilicate (IPS e.max CAD) specimens were obtained with a simulated milled surface, crystallized, etched with 5% hydrofluoric (HF) acid, and contaminated with an evaluation paste. The cleaning methods tested were air-water spray (SPRAY), 37% phosphoric acid (HPO), ultrasonic bath (ULT), cleaning paste (IVOC), and a conventional surface treatment (HF + silane–HF+SIL). The control (CTRL) group was not contaminated. After silane had been applied, resin cement cylinders were fabricated and light polymerized. Half of the cylinders (n=56) were tested for microshear bond strength at baseline (24 hours), and the other half after 210 days of water storage and 25 000 thermal cycles. Surface roughness, failure analysis, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) were performed. Statistical analysis was performed with the Kruskal-Wallis and Mann-Whitney tests for surface roughness and the 2-way ANOVA and Bonferroni post hoc tests for bond strength (α=.05). ResultsAt baseline, only SPRAY did not restore the bond strength compared with CTRL. After aging, the bond strengths of SPRAY and IVOC were lower than of CTRL (P<.05); no significant difference was found between CTRL, HPO, ULT, and HF+SIL (P>.05). EDS demonstrated the presence of carbon in the SPRAY and ULT groups, probably remnants of the evaluation paste. SEM analysis identified such remnants in the SPRAY group only. ConclusionsFor optimal bond strength between lithium disilicate and resin cement after evaluation paste use, cleaning the ceramic surface with 37% phosphoric acid, ultrasonic bath, or with hydrofluoric acid worked best.

Impact of polishing system on surface roughness of different ceramic surfaces after various pretreatments and bracket debonding

ObjectiveEvaluating various polishing methods after bracket debonding and excessive attachment material removal for different ceramics and pretreatments.Material and methodsZirconia (ZrO2), leucite (LEU) and lithium disilicate (LiSi) specimens were pretreated with a) silica coated alumina particles (CoJet); LEU and LiSi additionally with b) hydrofluoric acid (HF), c) Monobond Etch&Prime (MEP), d) silicium carbide grinder (SiC) before bracket bonding, shearing off, ARI evaluation, excessive attachment material removal and polishing with i) Sof-Lex Discs (Soflex), ii) polishing paste (Paste), iii) polishing set (Set). Before/after polishing surface roughness (Ra) was measured with a profilometer. Martens hardness parameter were also assessed.ResultsIrrespective of pretreatment Ra of LEU increased the most, followed by LiSi and ZrO2 (p < 0.001, SiC: p = 0.012), in accordance with the measured Martens hardness parameter. CoJet/SiC caused greater roughness as HF/MEP (p < 0.001). The ZrO2 surface was rougher after polishing with Paste/Set (p < 0.001; p = 0.047). Ra improved in the LEU/CoJet, LEU/SiC and LiSi/SiC groups with Soflex/Set (p < 0.001), in the LiSi/CoJet and LEU/HF groups by Soflex (p = 0.003, p < 0.001) and worsened by Paste (p = 0.017, p < 0.001). Polishing of HF or MEP pretreated LiSi with Set increased Ra (p = 0.001, p < 0.001), so did Paste in the LEU/MEP group (p < 0.001).ConclusionsPaste couldn’t improve the surfaces. Soflex was the only method decreasing Ra on rough surfaces and not causing roughness worsening. Polishing of LEU/LiSi after MEP, LEU after HF pretreatment doesn´t seem to have any benefit.Clinical RelevanceTo avoid long-term damage to ceramic restorations, special attention should be paid to the polishing method after orthodontic treatment.

Effect of pattern materials and fabrication techniques on the color of a pressed lithium disilicate ceramic: An in vitro study

Statement of problemPattern materials and their fabrication techniques have been reported to affect the marginal accuracy and internal fit of pressed lithium disilicate ceramic restorations. However, information regarding their effect on the color of such restorations is lacking. PurposeThe purpose of this in vitro study was to evaluate the color of a pressed lithium disilicate glass-ceramic fabricated from wax or resin patterns by using conventional and milling techniques. Material and methodsFifty-six Ø14×1.5-mm disk pattern specimens were divided into 4 groups based on the pattern material and fabrication technique: conventional wax pattern group (CW), conventional resin pattern group (CR), milled wax pattern group (MW), and milled resin pattern group (MR). Lithium disilicate specimens were fabricated by using the lost wax technique. The CIELab values were measured with a spectrophotometer (VITA Easyshade Advance). The ΔE00 values were calculated and compared with perceptibility (ΔE00=0.8) and acceptability (ΔE00=1.8) thresholds to interpret the color differences. The 2-way ANOVA and Tukey post hoc tests were used to analyze data (α=.05). ResultsTwo-way ANOVA revealed that ΔE00 was significantly affected by the pattern material (P<.001), fabrication technique (P=.034), and their interaction (P<.001). The ΔE00 of the CW group (0.76 ±0.04) was clinically imperceptible. No significant difference in the ΔE00 values was found between the reference and the MW (1.48 ±0.13) and MR (1.51 ±0.15) groups (P=.926), which were both clinically perceptible and acceptable. The highest ΔE00 was that of the CR group (2.06 ±0.22). ConclusionsThe color of the pressed lithium disilicate ceramic was influenced by the wax and resin pattern materials fabricated by using conventional or computer-aided design and computer-aided manufacturing (CAD-CAM) techniques. Only the CW pattern group showed color differences below the clinically perceptible threshold (ΔE00=0.8). The CR pattern group showed the highest color differences, which were not clinically acceptable.

The Effecacy of Different Surface Conditioning on Shear Bond Strength of Orthodontic Bracket Bonded to Lithium Disilcate Crowns; An in Vitro Study

Background and objective: Lithium disilicate widely used, and it is important to correctly bond orthodontic brackets to such materials. This study aimed to assess the impact of various types of surface conditioning methods on the shear bond strength (SBS) of orthodontic metal brackets to lithium disilicate crown. Materials and methods: In this in vitro study, 30 lithium disilicate specimens were prepared based on the type of surface conditioning into three surface conditioning groups (n=10 for each group). First group the semi-crowns surface was conditioned with 10% hydrofluoric acid etching, the second group was micro-etched with sandblast particles (50 um aluminum oxide particles) and the last group was conditioned with ultrasonic scaler. Valo light cure was utilized with 3200mw/cm2 light intensity. SBS was measured using a universal testing machine. The findings were statistically examined. Result: The results showed significant difference among the three groups where the sandblasting group had the higher mean of SBS, while the hydrofluoric acid etching group had the lower value and in between, the mean of ultra-sonic intermediate. &nbsp;&nbsp;&nbsp; &nbsp;Conclusions: &nbsp;Although the means of the three types of surface conditioning were significantly different, shear bond strength was positively affected by all of them and subsequently all types may be considered recommended techniques for reliable shear bond strength

Effect of yellow anodization of titanium on the shade of lithium disilicate ceramic with different thicknesses

Statement of problemThe color of the titanium abutment can affect the shade of the definitive restoration. Methods such as anodic oxidation, which changes the gray color of implant abutment to yellow, have been advocated to mask the unesthetic gray color of the abutment. However, whether a yellow anodized titanium abutment can prevent discoloration of translucent ceramic restorations is uncertain. PurposeThe purpose of this in vitro study was to evaluate the effect of the yellow anodization of titanium on the shade of lithium disilicate ceramic with different thicknesses by using CIEDE 2000 formulas. Material and methodsSixty grade V titanium backgrounds were fabricated and divided into 2 test groups (n=30): group A was anodized to a yellow color, and group U was unanodized. Each group was subdivided into 3 subgroups (n=10) according to the thickness of the lithium disilicate ceramic cemented over it: subgroup 1 with 1-mm-thick lithium disilicate, subgroup 1.5 with 1.5-mm-thick lithium disilicate, and subgroup 2 with 2-mm-thick lithium disilicate. Each titanium background was cemented to its corresponding lithium disilicate block by using translucent resin cement. For the control group, 5-mm-thick lithium disilicate specimens were fabricated. Color measurements of the specimens were made with a spectrophotometer, and differences were calculated by using CIEDE 2000 formulas (ΔE00). Comparisons between the 2 study groups were done by using independent samples t test. Two-way ANOVA was used to assess the effect of anodization and thickness on ΔE00 with calculation of adjusted means and 95% confidence intervals (α=.05). ResultsStatistically significant differences were found among the mean values between yellow anodized and unanodized groups in all ceramic thicknesses (P<.001 for 1 mm, P<.001 for 1.5 mm, and P<.046 for 2 mm). Yellow anodization of titanium and increasing the ceramic thickness from 1 to 2 mm decreased the ΔE00 values. ConclusionsThe restoration shade appeared to be improved by titanium anodization to a yellow color and by increasing the thickness of the machinable high-translucent lithium disilicate.

The Correlation of Surface Roughness Parameters of Zirconia and Lithium Disilicate with Steatite Wear.

Various surface roughness parameters are utilized to describe the surface in the tooth to ceramics abrasion and to assess the resulting wear. The use of three-dimensional parameters may offer a better estimation for wear and an improved deduced clinical surface treatment. The aim of this study was to determine the influence of various surface roughness parameters of zirconia and lithium disilicate ceramics on the wear of steatite antagonists. Forty zirconia specimens with a diameter of 7 mm and a thickness of 3 mm and 40 lithium disilicate specimens with the dimensions 10×10×4 mm were each divided into five subgroups. Two subgroups were treated with different clinically established diamond burs; a third subgroup was treated with a silicone polishing set. Two additional subgroups were produced by glazing the surfaces after treatment. Surface roughness parameters were determined by laser scanning microscopy. All specimens underwent 1.2 million loading cycles using steatite antagonists. After regular intervals of cycles, precision impressions were made to assess the wear. The correlation between wear and different roughness parameters was evaluated using the Spearman correlation test. For the glazed zirconia, unglazed zirconia, and glazed lithium disilicate specimens no significant correlations (p > 0.05) between the investigated roughness parameters and antagonist wear could be found. In the unglazed lithium disilicate groups, significant (p ≤ 0.05) correlations with steatite substance loss could be found for several roughness parameters after 1.2 million cycles. For lithium disilicate, it seems not sufficient to use only one roughness parameter to indicate the wear behavior of the surface. There was no correlation between wear and the tested roughness parameters of zirconia surfaces.

Effect of artificial aging on the translucency of monolithic zirconia materials sintered at different temperatures

Statement of problemTranslucent zirconia materials were developed as an alternative to lithium disilicate materials. However, the effect of sintering temperature and artificial aging on the translucency of zirconia materials is unclear. PurposeThe purpose of this in vitro study was to investigate the translucency of recently developed zirconia materials after different sintering temperatures and the effect of artificial aging. Material and methodsDisk-shaped specimens (Ø15×1 mm) of 3 different monolithic zirconias (Katana UTML, Prettau Anterior, VITA YZ XT) and a control lithium disilicate reinforced glass-ceramic (IPS e.max CAD LT) were evaluated. The zirconia specimens were divided into 2 subgroups with different sintering temperatures (1450 °C, 1550 °C) (n=5, N=35). The specimens were artificially aged in a thermocycle tester and a mastication simulator. The translucency parameter (TP) was calculated by measuring with a spectrophotometer. Kruskal-Wallis and Wilcoxon signed-rank tests were used to analyze the data (α=.05). ResultsWhile the overall TP of monolithic zirconia increased after artificial aging, the lithium disilicate specimens did not show a statistically significant difference (P=.35). The Prettau Anterior and VITA YZ XT specimens had a statistically significant higher TP than Katana UTML (P=.009). Sintering temperature did not have a statistically significant effect on the TP value of monolithic zirconia materials (P>.05). ConclusionsArtificial aging increased the TP, and the sintering temperature did not affect the TP of monolithic zirconia. The use of fully stabilized zirconia may be an alternative to lithium disilicate in esthetic restorations in clinical practice.

Shear Bond Strength of Lithium Disilicate Bonded with Various Surface-Treated Titanium.

Purpose Retention is one of the most important factors for fixed dental prostheses, especially in implant dentistry. Accordingly, the goal of this study was to evaluate the level of shear bond strength between titanium (Ti) subjected to different surface treatments and lithium disilicate glass-ceramics. Materials and Methods In this work, 90 titanium alloy specimens were divided into six groups as follows: the control group (CT), 50 μm alumina airborne-particle abrasion group (SB), silica-coated group (CJ), anodization group (AN), anodization followed by alumina 50 μm airborne-particle abrasion group (ANSB), and anodization followed by silica coating group (ANCJ). Titanium specimens were bonded to lithium disilicate specimens with resin cement (Multilink N). The specimens were restored in water at 37°C for 24 h, and then, shear bond strength (SBS) tests were performed using a universal testing machine (Shimadzu, Japan). The SBS values were statistically analyzed. The failure mode of the debonded titanium was classified after viewing the samples under a stereoscope. Results The results demonstrated that the mean SBSs of CT and AN were significantly lower than those of the other groups (p < 0.05). The SB group showed the highest SBS (29.47 ± 2.41 MPa); however, there was no significant difference between SB, ANSB, ANCJ, and CJ. The stereoscopic analysis demonstrated that the failure mode of AN was predominantly adhesive failure; whereas, the other groups showed cohesive and mixed failures. Conclusions In this study, it was found that the surface treatment with 50 μm alumina airborne-particle abrasion, silica coating with Cojet™ sand, anodization followed by 50 μm alumina airborne-particle abrasion, and anodization followed by silica coating with Cojet™ sand improved the SBS between titanium and lithium disilicate luted with Multilink N resin cement.

Translucency and masking ability of translucent zirconia; comparison with conventional zirconia and lithium disilicate.

The purpose of this study is to evaluate translucency and masking ability of translucent zirconia compared to conventional zirconia and lithium disilicate materials. Three types of zirconia blocks with different yttria contents (3Y, 4Y, 5.5Y) and LS blocks (Rosetta SM) were used. Ten specimens for each group were fabricated with 10 mm diameter, with both 0.8 mm and 1.5 mm thicknesses (± 0.02 mm). All groups of zirconia specimens were sintered and polished according to the manufacturer's instructions. To calculate the translucency parameter (TP), CIELAB value was measured with a spectrophotometer on black and white backgrounds. To investigate the color masking abilities, background shades of A2, normal dentin, discolored dentin, and titanium were used. The color difference (ΔE) was calculated with the CIELAB values of A2 shade background as a reference compared with the values in the various backgrounds. One-way ANOVA and Bonferroni tests were conducted (P < .05). The TP values of zirconia specimens increased as the yttria content increased. All materials used in the study were able to adequately mask normal dentin shade (ΔE < 5.5), but were incapable of masking severely discolored dentin (ΔE > 5.5). On the titanium background, all materials of 1.5 mm thickness were able to mask the background shade, but with a thickness of 0.8 mm, only 3Y-TZP and 4Y-PSZ were able to mask titanium background. All zirconia materials and lithium disilicate specimens used in this study were unable to adequately mask the shade of severely discolored dentin. It is recommended to use 3Y-TZP or 4Y-PSZ with a sufficient thickness of 0.8 mm or more to mask titanium.

Effectiveness of different orthodontic adhesives and a universal bonding resin on the bond strength of brackets to different ceramics

Objective: The aim of this study was to evaluate the effectiveness of different adhesives on the shear bondstrength (SBS) of brackets bonded to different ceramic materials. Material and Methods: Fifty disk-shapedspecimens were produced from lithium disilicate (IPS e.max CAD) and monolithic zirconia (Cercon) materials.Each specimen was polished with a three-step diamond polishing system. The polished ceramic surfaces wereconditioned with universal bonding resin (Assure Plus) without pre-treatment, except for two specimens.Central brackets were bonded onto different ceramic specimens with different adhesives as follows: group 1:conventional adhesive onto the lithium disilicate; group 2: one-step adhesive onto the lithium disilicate; group3: conventional adhesive onto the monolithic zirconia; group 4: one-step adhesive onto the monolithic zirconia.After thermal cycling, the specimens were subjected to the SBS test. The adhesive remnant index (ARI) scoreswere also recorded to evaluate bond failure type. Kruskal–Wallis and Mann-Whitney U tests were used forstatistical analysis. Results: There were statistically significant differences among the SBS values (p&lt;0.05). Themonolithic zirconia group with universal bonding resin and conventional orthodontic adhesive demonstratedthe highest SBS value (6.34 MPa) and ARI scores. The lithium disilicate group showed the lowest SBS value(2.17 MPa) with the same protocol. No adhesive remained on the lithium disilicate specimens. Conclusion: Onestepadhesive and universal bonding resin combination should not be considered as an alternative for lithiumdisilicate and monolithic zirconia restorations. Conventional adhesive and universal bonding resin applicationcan be effective on non-pretreated ceramic surfaces during orthodontic bonding.KEYWORDSBracket; Ceramics; Hydrophilic bonding resin; One-step adhesive.

A comparative evaluation of different saliva cleaning regimens on the shear bond strength of two different ceramics with resin cement

Contamination of all-ceramic restorations with oral fluids during clinical try-in can have a detrimental effect on their clinical performance. Objective: The aim of this study was to compare the efficiency of four different saliva cleaning regimens on the shear bond strength (SBS) of lithium disilicate and zirconia with resin cement. Materials and Methods: Ten cubic samples of lithium disilicate pressable ceramic (Group A) and monolithic zirconia (Group B) were fabricated. Four surfaces from each sample were coated with saliva, washed with water, and dried. These surfaces were subsequently treated with four different cleaning protocols (water [A1, B1], isopropyl alcohol [A2, B2], sodium hypochlorite [A3, B3], and Ivoclean™ [A4, B4]) and bonded to composite cylinders using dual-cure resin cement. The specimens were then tested for SBS. Results: Group A, subgroup A4 had a significantly higher mean SBS compared to other groups, and for Group B, subgroup B4 had a significantly higher mean SBS compared to other groups. The mean difference in the SBS for subgroup A1 and B1 was −3.862 at P = 0.01; for subgroup A2 and B2, it was −4.164 at P = 0.03; for A3 and B3, it was −4.845 at P &lt; 0.001; and for subgroup A4 and B4, it was −24.990 at P &lt; 0.001. Conclusion: Monolithic zirconia specimens showed significantly more SBS compared to lithium disilicate specimens in all subgroups. The mean SBS was highest for surfaces cleaned using Ivoclean in both groups.

Strength and flexibility of lithium disilicate bonded to polyetherketoneketone

Statement of problemPolyetherketoneketone (PEKK) is a high-performance polymer gaining popularity in dentistry for the fabrication of crowns, fixed partial dentures, removable partial denture frameworks, and frameworks for implant-supported fixed complete dentures. Despite a lack of performance data, lithium disilicate crowns have been bonded to retentive elements in PEKK frameworks. PurposeThe purpose of this in vitro study was to compare the bond strengths and flexibility of lithium disilicate to PEKK or zirconia. Material and methodsForty-five PEKK, 15 zirconia, and 60 lithium disilicate beam-shaped specimens (12.5×2×2 mm) were fabricated. The ends of the PEKK beams were subjected to 3 different surface treatments before the application and light polymerization of a primer: 50-μm aluminum oxide airborne-particle abrasion, nonthermal air plasma, and argon-oxygen plasma. The zirconia specimen bonding surfaces were prepared with 50-μm aluminum oxide airborne-particle abrasion and the application of primer. Lithium disilicate specimens were etched with 4.5% hydrofluoric acid, and primer was applied. The lithium disilicate specimens were luted with an adhesive resin cement to the PEKK and zirconia specimens by using light-activated and chemically activated polymerization. Fifteen monolithic specimens of PEKK, lithium disilicate, and zirconia (25×2×2 mm) were also fabricated. All specimens were incubated overnight in 100% humidity before testing. Bonded and monolithic specimens were loaded in a universal testing machine, and 4-point bend tests were conducted until failure (n=15). The flexural modulus and strength were calculated and statistically analyzed with 1-way analysis of variance and Student-Newman-Keuls post hoc tests (α=.05). ResultsAll bonded specimens failed at the adhesive interface. The zirconia-lithium disilicate bond strength was approximately twice that of the strongest group of PEKK (airborne-particle abrasion group) bonded to lithium disilicate (42 ±12 MPa and 24 ±13 MPa, respectively) and was approximately 9 times more rigid (71 ±19 GPa and 8 ±2 GPa, respectively). Monolithic PEKK fractured at 238 ±22 MPa, monolithic zirconia at 771 ±128 MPa, and monolithic lithium disilicate at 173 ±26 MPa. Monolithic PEKK was approximately 30 times more flexible than monolithic zirconia (6 ±1 GPa and 178 ±16 GPa, respectively). All values were statistically significantly different (P<.05), except for the bond strength between lithium disilicate and PEKK treated with airborne-particle abrasion and nonthermal air plasma and the flexural moduli of PEKK to lithium disilicate. ConclusionsBond strength between PEKK and lithium disilicate was significantly weaker than that between zirconia and lithium disilicate. Monolithic PEKK was significantly more flexible than monolithic zirconia.

Orthodontic bonding to silicate ceramics: impact of different pretreatment methods on shear bond strength between ceramic restorations and ceramic brackets

ObjectiveThe study aims to investigate the shear bond strength (SBS) between silicate ceramic restorations and ceramic brackets after different pretreatments and aging methods.Material and methodsLeucite (LEU) and lithium disilicate (LiSi) specimens were pretreated with (i) 4% hydrofluoric acid + silane (HF), (ii) Monobond Etch&Prime (MEP), (iii) silicatization + silane (CoJet), and (iv) SiC grinder + silane (SiC). Molars etched (phosphoric acid) and conditioned acted as comparison group. SBS was measured after 24 h (distilled water, 37 °C), 500 × thermocycling (5/55 °C), and 90 days (distilled water, 37 °C). Data was analyzed using Shapiro–Wilk, Kruskal–Wallis with Dunn’s post hoc test and Bonferroni correction, Mann–Whitney U, and Chi2 test (p < 0.05). The adhesive remnant index (ARI) was determined.ResultsLEU pretreated with MEP showed lower SBS than pretreated with HF, CoJet, or SiC. LiSi pretreated with MEP resulted in lower initial SBS than pretreated with HF or SiC. After thermocycling, pretreatment using MEP led to lower SBS than with CoJet. Within LiSi group, after 90 days, the pretreatment using SiC resulted in lowest SBS values. After HF and MEP pretreatment, LEU showed lower initial SBS than LiSi. After 90 days of water storage, within specimens pretreated using CoJet or SiC showed LEU higher SBS than LiSi. Enamel presented higher or comparable SBS values to LEU and LiSi. With exception of MEP pretreatment, ARI 3 was predominantly observed, regardless the substrate, pretreatment, and aging level.ConclusionsMEP pretreatment presented the lowest SBS values, regardless the silicate ceramic and aging level. Further research is necessary.Clinical relevanceThere is no need for intraoral application of HF for orthodontic treatment.

Analysis of Biofilm Adhesion on CAD/CAM Lithium Disilicates Under Different Types of Intraoral Polishing.

To evaluate the adhesion of Streptococcus mutans (S. mutans) on lithium disilicate ceramics, submitted to different intraoral polishing protocols, and the degree of surface smoothness obtained. Fifty lithium disilicate specimens were divided into 5 groups (n=10): G1-Glaze Group (positive control); G2-Glaze Group + Wear + Glaze; G3-Wear Group (negative control); G4-Ceramisté Wear Group; G5-Optrafine Wear Group. Surface roughness (Ra - μm) was evaluated and the surface characteristics were assessed using a scanning electron microscope (SEM); to assess S. mutans biofilm, the number of cultured cells was evaluated by counting colony-forming units (CFU/mL). The data underwent one-way ANOVA followed by Tukey's test (P⟨.05). There was a significant difference in the surface roughness of all groups compared with G3. There was no significant difference between the G4 and G5 groups that received polishing. G1 group had the lowest mean roughness values. There was a difference in Log values (CFU/mL) between the G3 group and the groups that received glaze (G1 and G2). The G3 group had the highest adhesion of S. mutans (4.53 Log). The most effective polishing protocol after wear is glazing, presenting the lowest roughness and CFU/mL values.

The Bond Strength of a Universal Adhesive System with Silane to Lithium Disilicates in Comparison with an Isolated Silane Coupling Agent.

The aim of this in vitro study was to evaluate the effects of different durations of silane coupling agent application compared to a universal adhesive system regarding the shear bond strength of two ceramic materials. A total of 120 human molars were ground to the dentinal coronal third and then fixed into an acrylic resin holder. Lithium disilicate specimens were divided into two main groups according to the ceramic type: computer-aided design/computer-aided manufacturing IPS e.max CAD and heat-pressed Initial LiSi Press GC (dimensions of 4 × 3× 3 mm). Each main group was subdivided into 6 subgroups (n = 10) according to the duration of the silane and universal adhesive system application (20, 60, or 120 seconds) on the ceramic surface before cementation; then, the cementation procedures were performed. All specimens were subjected to 5000 thermal cycles at 5 and 55°C before testing. The shear bond strength was measured using a universal testing machine. ANOVA and Scheffe post hoc test multiple comparisons tests were conducted (α = 0.05). The shear bond strength increased as the duration of the silane and universal adhesive system application increased. The highest bond value for each material was found for the silane application at 120 seconds, with a significant difference between 120 and 60, and 20 seconds for both e. max CAD and Initial LiSi materials (p = 0.029 and p ˂ 0.001, respectively). No significant difference was found between 60 and 20 seconds when silane and universal adhesive system were applied for both e. max CAD and Initial LiSi materials (p = 0.169 and p = 0.120, respectively). All groups treated with the silane primer showed significantly higher values than the universal adhesive system for each application time (p ˂ 0.001). Increasing the duration of the silane coupling agent and universal adhesive system application to 120 seconds on the ceramic surface before cementation improved the shear bond strength of the ceramic-cement interface. Ceramic pretreatment with silane could be an essential step for bonding ceramic to dentin regardless of silane presence in the universal adhesive system.