Lithium Disilicate Ceramics Research Articles

Effect of Self-Adhesive Resin Cement Film Thickness on the Shear Bond Strength of Lithium Disilicate Ceramic–Cement–Tooth Triplex

Cement film thickness may have an impact on the shear bond strength (SBS) of lithium disilicate dental ceramics luted to human enamel with resin cement. The objective of this study was to evaluate SBS of lithium disilicate ceramics adhered to enamel using resin cement at different thicknesses. In total, 50 ceramic specimens (3 × 3 × 3 mm) and 50 premolar teeth were prepared and randomly assigned to 5 groups (n = 10 each). Ceramic specimens were designed with five cement film thicknesses (50 μm; 100 μm; 150 μm; 200 μm; and 300 μm). Teeth surfaces (4 × 4 mm) were prepared with a high-speed handpiece mounted on a dental surveyor. Ceramic specimens were cemented to teeth with resin cement (3MTM RelyXTM U200, Resin-Self-Adhesive-Cement). The specimens were then thermocycled for 6000 cycles with a 30 s dwell time and a 5 s transfer time in water (5 °C and 55 °C). A Universal-Testing-Machine was used to measure SBS (MPa). Statistical analysis in SPSS included Anova and Tukey’s tests. The SBSs of ceramics adhered to teeth revealed significantly different values across all test groups (p = 0.000). The findings showed that as cement layer thickness increased, so did the SBS. The cement spaces at 50 and 300 μm had the lowest SBS (9.40 + 1.15 MPa) and maximum SBS (21.98 + 1.27 MPa), respectively. The SBS of the lithium disilicate ceramic luted to natural human enamel increased along with the cement layer thickness.

Experimental Study to Evaluate the Internal Fit between Computer Aided Designing/Computer Aided Manufactured (CAD-CAM) Zirconia Coping and Pressable Ceramic Coping

Marginal fit of the dental restoration is important to prevent microleakage and periodontal problems so as to avoid secondary caries around the abutment teeth. The purpose of the study was to compare and evaluate the internal fit of copings manufactured using a CAD/CAM-system and laboratory-made heat-pressed ceramics. For this research, typodont mandibular left first molar was prepared about 1.5mm occlusal reduction and 6˚ taper both mesiodistally and buccolingually with shoulder finish line of 1.0mm width to receive all ceramic crown which was duplicated in silicone impressions and the respective working casts were formed using Type IV die stone and the restorations were made by CAD-CAM system for zirconia coping and wax pattern for heat-pressable lithium disilicate ceramics. Total of 20 dies were made and divided into Group I- zirconia copings and Group II - heat pressable lithium disilicate ceramics, in which 10 crowns were made in each group. The crowns were cemented to the respective dies with cyanoacrylate cement using finger pressure. The samples were then sectioned facio-lingually and the three zones measured were 2mm above the marginal finish line in both lingual and buccal side and one in the center of the occlusal surface. The mean horizontal and the vertical internal adaptation discrepancies statistically analyzed using Mann-Whitney test. It was concluded that CAD-CAM milled zirconia copings showed closer adaptation in the axial walls than heat pressed ceramic copings. But in the mid occlusal level where the adaptation was closer in heat pressed ceramic copings than the CAD-CAM milled zirconia copings.

Investigation of Microscopic Structure, Translucency Parameters, and Fracture Toughness of Two Pressable Lithium Disilicate Glass-Ceramic Materials.

To investigate the microscopic structure and fracture toughness of two pressable glass-ceramics comprising GC Initial LiSi Press (LiSi) and IPS e.max Press (e.max) with different levels of translucency. Four groups of LiSi and e.max with medium opacity and high translucency levels were examined. The crystal morphology of acid-etched specimens was observed under a scanning electron microscope (SEM). Six specimens in each group were fabricated in square shape (12 mm '12 mm ' 1.5 mm) to measure translucency parameters (TP) using a spectrophotometer. Ten bar-shaped specimens each group with dimension of 23 mm ' 2 mm ' 4 mm were determined the fracture toughness (KIc) by a surface crack in flexure (SCF) using a universal testing machine. One-way ANOVA and Scheffe post-hoc tests were used for statistical analysis. LiSi showed fine dense crystals 1 - 1.5 µm in size, while e.max showed long rod-shaped crystals 3 - 4 µm in size. The TP values of all specimens were coincided with their translucency levels.There was no statistical difference in the KIc between different translucency for both ceramics (p<0.05). However, the KIc of e.max was significantly higher than that of LiSi at both translucency levels. As a result of larger and longer crystals in e.max, it could provide better crack deviation mechanism to resist the fracture. Within the limitations of this study, the translucency levels of both lithium disilicate ceramics did not affect the fracture toughness of the materials. The fracture toughness of e.max was statistically higher than LiSi.

Retrospective evaluation of factors affecting long-term clinical performance of CAD-CAM laminate veneers.

The purpose of the study was to assess the clinical performance of CAD-CAM laminate veneers placed by a single operator and systematically evaluated for up to 10 years. A total of 197 laminate veneers fabricated using either feldspathic ceramic (VMII) or lithium disilicate ceramic (EmaxCAD) were followed up to 10 years in 32 patients. Technical, esthetical, and biological findings of each restoration were evaluated using modified United States Public Health Service criteria. The survival and complication rates were assessed using Kaplan-Meier survival analysis and compared using the Log Rank test. Statistical significance was set at p<0.05. The estimated Kaplan-Meier survival rate was 91.9% after the mean observation period. According to ceramic system used, the estimated Kaplan-Meier survival rate amounted to 92.7% for Emax-CAD and to 89.1% for VMII. Survival rates were significantly affected by the location of veneer according to Log Rank test (p < 0.05). A range of survival rates between 83.3% and 98.6% were observed based on the location of veneer. CAD-CAM laminate veneers milled of feldspathic or lithium disilicate ceramics have comparable long-term survival rates. Oral positioning affects the survival of veneer. Veneers of incisors have higher survival rates than the veneers of maxillary canines and premolars.

The 'One Customized Abutment One Time' concept - An innovative technique for optimizing immediacy and digital protocols.

Disconnection and reconnection of abutments multiple times have known to affect the mucosal barrier around implants leading to marginal bone loss. This clinical report describes a novel technique that amalgamates the benefits of digital technologies encompassing the fabrication of surgical guides for implant placement, customized hybrid zirconia abutments and all ceramic lithium disilicate crowns prior to implant placement. A correct 3-dimensional implant positioning along with immediate placement of the definitive hybrid customized abutment and a lithium disilicate crown has the potential to reduce treatment time, visits and costs while delivering optimal esthetic outcomes.

Evaluation of Er:YAG laser energy transmitted through novel dental zirconia ceramics.

Erbium:yttrium-aluminum-garnet (Er:YAG) laser debonding is a promising removal method in prosthodontics. This study aimed to assess Er:YAG laser energy transmission through novel zirconia ceramics. Five types of ceramic samples: lithium disilicate ceramic (LDC), self-glazed zirconia (SGZ), 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP), 4Y-TZP and 5Y-TZP with 5 thicknesses (0.5, 1.0, 1.5, 2.0, 2.5 mm) and 2 shades (A1, A3), 50 specimens total, were made. Fourier transformation infrared absorption spectra were obtained for each ceramic type, and Er:YAG laser energy transmission tests were conducted for each specimen. The novel zirconia ceramic (SGZ, 4Y-TZP, 5Y-TZP) transmission ranged from 40%-60%. The transmitted laser energy decreased with increasing ceramic thickness, and the differences between different shades were significant (p<0.05). The novel zirconias had a higher translucency than 3Y-TZP at any given thickness and shade, and when the thickness was >1.5 mm, the novel zirconias had a higher translucency than LDC.

IN VITRO SURVIVAL AND FRACTURE FORCE OF LITHIUM DISILICATE HYBRID ABUTMENT CROWNS.

To evaluate the behavior of hybrid abutment crowns fabricated from monolithic lithium disilicate ceramic (LDC) and to compare the influence of different in vitro artificial aging protocols. A total of 32 monolithic hybrid abutment crowns of monolithic LDC were fabricated. Of these, 24 were artificially aged using three different protocols up to a 20 year simulation (1.2 × 106, 2.4 × 106, 4.8 × 106 chewing cycles, thermocycling), a control group underwent no artificial aging (n &#61; 8, N &#61; 32). Load-to-failure tests were conducted for all specimens, and failure values were compared (P < .05). All specimens passed in vitro aging. Mean failure load values between 532.6 and 562.8 N were found but did neither differ significantly among the test groups nor from the control group. Within the limitations of this in vitro pilot study, hybrid abutment crowns manufactured from monolithic LDC seem to offer appropriate long-lasting mechanical stability over a simulation period up to 20 years. The failure values and complication pattern seem to be independent of several aging protocols in this test set-up.

Clinical performance of monolithic polymer-infiltrated ceramic and lithium disilicate posterior crowns: A controlled, randomized, and double-blind clinical trial

The success rate of monolithic polymer-infiltrated ceramic posterior crowns after 1 year is unclear. The purpose of this controlled, randomized, and double-blind clinical trial was to evaluate the performance of posterior complete crowns in polymer-infiltrated and lithium disilicate ceramics and to assess the impact of oral rehabilitation on esthetic satisfaction, quality of life, and periodontal health. A total of 33 crowns were provided in 18 participants allocated to 2 groups: Control (Lithium disilicate-IPS e.max CAD; Ivoclar AG) and Experimental (Polymer-infiltrated ceramic-Vita Enamic; Vita Zahnfabrik). The crowns were evaluated before treatment (T0) and after 1 (T1), 6 (T2), and 12 (T3) months by using modified United States Public Health Service (USPHS) criteria, visual analog scales (VASs), oral impacts on daily performances (OIDP), and periodontal parameters. Survival analysis was performed by using Kaplan-Meier followed by the log-rank test (α=.05). The OIDP and USPHS data were analyzed descriptively while VASs for esthetic satisfaction and periodontal parameters were statistically evaluated by using the Mann-Whitney Friedman, and Wilcoxon post hoc tests. For 18 participants with a mean age of 47.2 years, 19 crowns were manufactured in lithium disilicate and 14 in polymer-infiltrated ceramic. The Kaplan-Meier test revealed similar survival rates of 92.5% for polymer-infiltrated ceramic and 94.7% for lithium disilicate (P>.05). The analysis of periodontal parameters revealed a significant increase in the bleeding on probing (BOP) for polymer-infiltrated ceramics (P=.032) but for lithium disilicate, it was not significant (P=.387). Survival rates between the evaluated materials were not significantly different, with acceptable clinical performance after 1 year of follow-up.

Influence of Finishing Procedures on the Color Stability and Surface Roughness of Lithium Disilicate and Monolithic Zirconia Oxide

Aim: This study aimed at evaluating the impact of different adjustments and artificial aging on the color change (ΔE) and surface roughness (Ra) of monolithic zirconia (MLZ) and lithium disilicate (LD) ceramics. Materials and methods: Forty discs were prepared from two types of MLZs, including ceramill monolithic Zr (CM-Zr) and Prettau PSZ Zr (PP-Zr), and one LD (IPS e.max-LD, IPS-LD). After different clinical adjustments (performed with glazing, bur, bur + glazing, and bur + polishing) and artificial aging (in-vitro coffee immersion), the ΔE was assessed using a spectrophotometer. The roughness (Ra) was also evaluated after these adjustments. The ANOVA and multiple com-parisons test were used to compare the groups statisitcally and the level of significance was set at 5%. Results: In the CM-Zr group, the greatest ΔE was observed after bur adjustment (3.32, p &lt; 0.05) while the lowest ΔE was seen after the glaze treatment (2.11, p &lt; 0.05). In the PP-Zr group, the highest ΔE was observed after bur treatment (2.70, p &lt; 0.05) while the lowest ΔE was seen after the glaze treatment (1.25, p &lt; 0.05). Lastly, for the IPS-LD group, the highest ΔE was again observed after bur treatment (2.91, p &lt; 0.05) while the lowest ΔE was seen after glaze treatment (1.0, p &lt; 0.05). After coffee immersion, it was observed that the highest overall ΔE was observed for CM-Zr after the bur and polish treatment (3.45), while the lowest overall ΔE was observed in IPS-LD after the glaze treatment (2.10). All the ΔE values were within the clinical acceptable range. The highest overall Ra was witnessed for CM-Zr after bur adjustment (1.64), while the lowest overall Ra was seen for IPS-LD after glaze treatment (0.26). Different clinical adjustments and artificial aging influence the colour stability of different ceramic materials (CM-Zr, PP-Zr, and IPS-LD). Compared to the MLZ, IPS-LD ceramics were more stable as they presented with lower ΔE after surface adjustments and coffee immersion. Conclusions: The surface adjustment that minimally affected the colour of these ceramics was glaze treatment, while the ceramics were most affected by bur adjustments. Coffee aging affected colour stability of all ceramic materials. IPS-LD ceramics presented the lowest Ra values after different clinical adjustments.

Evaluation of Fracture Resistance of Occlusal Veneers Made of Different Types of Materials Depending on Their Thickness.

The aim of this study is to assess the fracture resistance of occlusal veneers made of various materials depending on their thickness. In total, 120 occlusal veneers were examined. The restorations were made of four ceramics: leucite LC (IPS Empress Esthetic), hybrid HC (Vita Enamic), lithium disilicate LDC (IPS e.max Press), and zirconium oxide ZOC (Ceramill Zolid HT). A total of 30 veneers were made of each material, 10 for each of the three thicknesses: 1 mm, 1.5 mm, 2 mm. The restorations were cemented on identical abutments duplicated from the developed phantom tooth 35 (KaVo) with composite cement (All Bond Universal). The samples prepared in this way were subjected to a compressive strength test in a universal testing machine. Statistical analysis of the results was performed. The average fracture resistance of occlusal veneers made of zirconium oxide ceramic was 1086-1640 N, of lithium disilicate ceramics 456-1044 N, of hybrid ceramics 449-576 N, and of leucite ceramics 257-499 N. Occlusal veneers made of ceramics, zirconium oxide and lithium disilicate, had the highest resistance to fractures. Restorations made of leucite ceramics turned out to be the least resistant to forces. The greater the thickness of the ceramic occlusal veneers, the greater their fracture resistance.

Zirkonya ile Güçlendirilmiş Lityum Silikat, Zirkonya ve Lityum Disilikatın Translüsensi ve Bükülme Dayanımının Karşılaştırılması

Objectives: Optimal mechanical and aesthetic properties are expected from all ceramic restorations in dentistry to maintain good prognosis. Zirconia restorations have had mechanical advantages and lithium disilicate ceramics have provided aesthetic advantages. This study intended to compare the four-point flexural strength and translucency of zirconia reinforced lithium silicate with solid zirconia and lithium disilicate. &#x0D; Material and Methods: 90 bars (1x4x18 mm) for flexural strength test (n=30) and 30 square shaped (1x10x10 mm) samples for translucency measurement (n=10) were obtained from solid zirconia (BR-BruxZir), zirconia reinforced lithium silicate (VS-Vita Suprinity) and lithium disilicate (EM-Emax CAD) blocks. All BR samples were sintered, VS and EM were crystallized according to the manufacturer's recommendations. These samples were grinded and polished. Subsequently, they were ultrasonically cleaned and flexural strength values (MPa) were obtained in a universal test device. Color measurements were performed with a dental spectrophotometer using black and white backgrounds to determine the translucency values. Statistical analysis was performed using one-way ANOVA and Tukey HSD tests. Results: BR showed the highest mean flexural strength. There was no significant difference between EM and VS (p&gt;0.05), while BR showed significantly different flexural strength (p

The Impact of Riboflavin, Nd: YAG Laser, and Ceramic Primer Pretreatment on Surface Roughness, Bond Failure, and Adhesive Strength of Resin Composite to Lithium Disilicate Ceramics: A Scanning Electron Microscopy (SEM) Analysis

Aim: Adhesive bond integrity and surface roughness (Ra) of LDS ceramics following the application of various surface treatments. Material and Method: Forty disks of LDS ceramics were prepared and randomly distributed into different groups based on the method of pretreatment. Group 1: HF (hydrofluoric acid) + S (Silane), Group 2: RFP (riboflavin photosensitizer) S, Group 3: SECP (selfetch ceramic primer and Group 4: Nd: YAG laser. Following conditing LDS ceramic was assessed for Ra and Scanning electron micrographs. All LDS ceramics were bonded and the strength of the resin-ceramic interface was tested using a universal testing machine. The debonded samples were examined under a stereomicroscope. The failure modes were categorized as cohesive, admixed, and adhesive interfaces. Ra and bond integrity values were tested using, two-way ANOVA, and Tukey post hoc tests. (p = 0.05). Results: The highest Ra and bond values were exhibited by samples pretreated using HF + S. Nevertheless, group 2 (RFP + S) demonstrated the lowest bond integrity (12.37 ± 1.98 MPa). No significant differences in the bond integrity outcomes between group 1, group 3 (SECP), and group 4 (Nd: YAG laser + S) (p &gt; 0.05). Conclusion: Nd: YAG and SECP have the potential to be used as an LDS ceramic conditioner alternative to HFA for adequate bond scores.

Argon Plasma Treatment Effects on the Micro-Shear Bond Strength of Lithium Disilicate with Dental Resin Cements.

The low bond strength of lithium disilicate (LD) ceramics to dental resin cements remains a critical issue for dental applications because it leads to frequent replacement and causes tooth tissue destruction and consumption. The objective of this study was to examine the effects of atmospheric non-thermal argon plasma (NTP) treatment on LD to improve its micro-shear bond strength (μSBS) with dental resin cements because LD mostly experiences shear stress for its commonly used dental applications as crowns or veneers. Argon plasma treatment was performed on hydrofluoric (HF) acid-etched LD surfaces, and then commercial resin cements were subsequently applied to the treated LD surfaces. The plasma treatment significantly reduced the water contact angle of the LD surface to less than 10° without changing the surface morphology. The μSBS test was performed with cement-bonded LD samples after 24 h and 30 days, as well as after 1000 cycles of thermal cycling. The test results show that, as compared with the untreated controls, 300 s of plasma treatment significantly improved the LD-resin cement bond strength by 59.1%. After 30 days of storage in DI water and 1000 cycles of thermal cycling, the plasma-treated LD samples show 84.2% and 44.8% higher bond strengths as compared to the control samples, respectively. The plasma treatment effect on LD surfaces diminished rapidly as the bond strength decreased to 25.5 MPa after aging in the air for 1 day prior to primer and cement application, suggesting that primers should be applied to the LD surfaces immediately after the plasma treatment. These results demonstrate that, when applied with caution, plasma treatment can activate LD surfaces and significantly improve the SBS of LD with dental resin cements in both short-term and long-term periods.

Effects of over-the-counter at-home whitening products with LED light on surface roughness of partially- and fully crystalized CAD/CAM lithium disilicate ceramics.

The aim of this study is to evaluate the effect of over-the-counter (OTC) at-home whitening products with LED light on partially- and fully-crystalized CAD/CAM lithium disilicate ceramics. Two partially-crystalized CAD/CAM lithium disilicate ceramics, Amber Mill and IPS e.max CAD, and one fully-crystalized CAD/CAM lithium disilicate ceramic, n!ce Straumann, were used. The specimens were divided based on treatment with OTC whitening products: no treatment provided, Colgate Optic, Crest 3D and Walgreens Deluxe. The surface roughness of the specimens was evaluated with an optical profilometer and scanning electron microscopy. The three LED whitening products significantly increased the surface roughness and changed surface morphology of Amber Mill and IPS e.max CAD but no differences for n!ce Straumann. OTC at-home whitening products with LED light can significantly increase the surface roughness of restorations fabricated with these partially-crystalized CAD/CAM lithium disilicate ceramic restorations. However, these products do not increase the surface roughness of restorations fabricated with this fully-crystalized lithium disilicate ceramic.

Minimally invasive treatment of erosions to regain health, function and aesthetics with indirect restorations

This article discusses the treatment of tooth structure loss due to erosion using indirect lithium disilicate ceramic restorations. Minimally invasive approaches, in which the eroded teeth are conservatively prepared and restored with minimally invasive restorations, are recommended. Lithium disilicate ceramics are currently the material of choice for this type of treatment as they can withstand maximum occlusal forces in the posterior region. The restorative process should be guided by diagnostic procedures that define the clinical therapeutic goal at the beginning of treatment. Adhesive cementation with the correct protocol is crucial for full mechanical strength of the restoration. At the end of the treatment, in addition to preventive measures, an overnight protective splint is recommended to ensure long-term clinical stability.

Effect of the application of a hydrogen peroxide home bleaching agent on the cytotoxicity of different CAD-CAM restorative materials.

The information regarding the cytotoxicity of ceramic and resin-matrix ceramic materials subjected to over-the-counter bleaching agents is limited in the literature. The aim of the present study was to investigate the cytotoxic effects of lithium disilicate ceramic (LDC), resin nano-ceramic (RNC) and nano-hybrid composite (NHC) computer-aided design/ computer-aided manufacturing (CAD-CAM) block materials subjected to a home bleaching agent and artificial saliva. A total of 432 specimens were prepared from 3 different CAD-CAM materials. Each material group was divided into 4 groups according to the storage medium (phosphate-buffered saline (PBS) or artificial saliva), and whether the specimens were subjected to a bleaching agent or not. For the bleached groups, hydrogen peroxide (10%) was applied to the specimens for 30 min/day for 15 days, and the specimens were immersed in PBS or saliva after bleaching. The viability of epithelial cells was detected using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay at the end of the 5th, 10th and 15th day of the study. The data was statistically analyzed. Regardless of the storage medium and the time period, all restorative materials decreased the viability of cells. The highest cytotoxicity levels were determined on the 15th day of the study. The application of a bleaching agent increased the cytotoxicity of the LDC specimens stored in artificial saliva. The RNC material stored in PBS demonstrated significantly higher cell viability than the LDC and NHC groups. The LDC and RNC specimens stored in artificial saliva did not show any significant difference in cytotoxicity. When the materials were subjected to bleaching, NHC demonstrated the highest cytotoxicity during all periods. No significant difference was found between the LDC and RNC specimens subjected to both artificial saliva and bleaching in terms of cytotoxicity. The type of restorative material, the immersion medium, the application of a bleaching agent, and the application period affected the cytotoxicity of the materials. Over-the-counter home bleaching agents may induce cellular cytotoxicity due to the existing restorations, and patients should be informed about this potential biological response.

Decontamination of lithium disilicate ceramics using various photosensitizers, herbal and chemical disinfectants, and the effect of surface conditioners on bond strength values

AimTo assess and compare the antimicrobial efficacy of disinfectants on lithium disilicate ceramic (LDC) used in dental applications and shear bond strength (SBS) of LDC after using different conditioners hydrofluoric acid (HF), self-etching ceramic primers (SECP) and Neodymium-doped yttrium orthovanadate (Nd: YVO4). Materials and methodsOne hundred and twenty LDC discs were fabricated by auto-polymerizing acrylic resin using the lost wax technique. S. aureus, S. mutans, and C. albican were inoculated on thirty discs (n = 30 each). Each group was further divided into three subgroups based on different disinfecting agents used (n = 30) Group 1: Garlic extract, Group 2: Rose Bengal (RB) activated by PDT, and Group 3: Sodium hypochlorite (NaOCl). An assessment of the survival rate of microorganisms was performed. The remaining thirty samples were surface treated using three different LDC surface conditioners (n = 10) Group 1: HF + Silane (S), group 2: SECP, and Group 3: Nd: YVO4 laser+S. SBS and failure mode analysis were performed using a universal testing machine and stereomicroscope at 40x magnification, The statistical analysis was conducted using one-way ANOVA and Post Hoc Tukey test. ResultsGarlic extract, RB, and 2% NaOCl sample displayed comparable outcomes of antimicrobial potency against C. albicans, S aureus, and S. mutans (p > 0.05). Furthermore, SBS analysis showed HF+S, SECP, and Nd: YVO4+S exhibited comparable outcomes of bond strength (p > 0.05). ConclusionGarlic extract and Rose bengal activated by PDT can be contemplated as alternatives to the chemical agent NaOCl used for LDC disinfection. Similarly, SECP and Nd: YVO4 possess the potential to be used for the surface conditioning of LDC to improve the bond integrity with resin cement.

Fracture strength and three-dimensional marginal evaluation of biocompatible high-performance polymer versus pressed lithium disilicate crowns

Statement of problemDespite the acceptable physical properties of biocompatible high-performance polymer (BioHPP), little is known about the marginal accuracy and fracture strength of restorations made from this material. PurposeThis in vitro study assessed the marginal and internal adaptation and fracture strength of teeth restored with lithium disilicate (LD) ceramics and BioHPP monolithic crowns. Material and methodsTwenty-four extracted premolars were prepared for complete coverage crowns and divided into 2 groups to receive pressed IPS e.max LD, or computer-aided design and computer-aided manufacturing (CAD-CAM) BioHPP monolithic crowns. After adhesive cementation, the marginal and internal adaptations of the restorations were evaluated by microcomputed tomography at 18 points for each crown. Specimens were subjected to 6000 thermal cycles at 5 °C and 55 °C and 200 000 load cycles of 100 N at a frequency of 1.2 Hz. The fracture strength of the restorations was then measured in a universal testing machine at a crosshead speed of 0.5 mm/min. Data were analyzed via an independent-sample t-test (α=.05). ResultsThe mean ±standard deviation of marginal gap was 138.8 ±43.6 μm for LD and 242.1 ±70.7 μm for BioHPP groups (P=.001). The mean ±standard deviation value of absolute marginal discrepancy was 193.8 ±60.8 μm for LD and 263.5 ±97.6 μm for BioHPP groups (P=.06). The internal occlusal and axial gap measurements were 547.5 ±253.1 μm and 197.3 ±54.8 μm for LD (P=.03) and 360 ±62.9 μm and 152.8 ±44.8 μm for BioHPP (P=.04). The mean ±standard deviation of internal space volume was 15.3 ±11.8 μm³ for LD and 24.1 ±10.7 μm³ for BioHPP (P=.08). The mean ±standard deviation of fracture strength was 2509.8 ±680 N for BioHPP and 1090.4 ±454.2 MPa for LD groups (P<.05). ConclusionsThe marginal adaptation of pressed lithium disilicate crowns was better, while BioHPP crowns displayed greater fracture strength. Marginal gap width was not correlated with fracture strength in either group.

Final Color of CAD-CAM Produced Thin Lithium Disilicate Ceramics Cemented with Different Colored Resin Cements on Darker Backgrounds

Aim: The aim of the present study was to evaluate the final color of CAD-CAM produced thin lithium disilicate ceramics cemented with A2, opaque, and bleach resin cements on darker backgrounds. Materials and Method: Nine different experimental groups (n=10) were generated according to the colors of resin backgrounds (ND3:A3, ND4:A3.5, and ND8:A4) and cements (A2, opaque, and bleach). Target specimen was prepared by cementing lithium disilicate ceramic layer onto ND2 (A2) background by using translucent resin cement. The color difference values between experimental groups and target specimen were calculated according to CIEDE2000 formula. The data were statistically analyzed by using Kruskall Wallis test (α=0.05). Results: The results showed that most of the experimental groups had higher color difference values than acceptability threshold (1.8) except ND3-A2 and ND3-opaque groups. It was observed that when the background got darker, the color difference values increased. Conclusion: The darker backgrounds (A3, A3.5, and A4) and resin cement color (A2, opaque, and bleach) affected the final color of the lithium disilicate ceramics in 1 mm thickness. Color difference values were found in clinically acceptable limits for cementing lithium disilicate ceramics with A2 and opaque resin cements on A3 background.

Influence of the Application Time of Silane for the Bonding Performance between Feldspar or Lithium Disilicate Ceramics and Luting Resin Composites.

A correct silanization time is essential for successful surface functionalization and sufficient bonding to dental ceramics. The shear bond strength (SBS) of lithium disilicate (LDS) and feldspar (FSC) ceramics and luting resin composite was investigated with respect to different silanization times, taking into account the physical properties of the individual surfaces. The SBS test was performed with a universal testing machine, and the fracture surfaces were evaluated by stereomicroscopy. The surface roughness of the prepared specimens was analyzed after etching. Changes in surface properties due to surface functionalization were evaluated by surface free energy (SFE) via contact angle measurement. Fourier transform infrared spectroscopy (FTIR) was used to determine the chemical binding. The roughness and SBS of the control group (no silane, etched) were higher for FSC than for LDS. Regarding the SFE, the dispersive fraction increased and the polar fraction decreased after silanization. FTIR confirmed the presence of silane on the surfaces. The SBS of LDS showed a significant increase from 5 to 15 s, depending on the silane and luting resin composite. For FSC, cohesive failure was observed for all samples. For LDS specimens, a silane application time of 15 to 60 s is recommended. Based on clinical conditions, no difference between the silanization times was observed for FSC specimens, indicating that etching alone produces sufficient bonding.