Hybrid Ceramics Research Articles

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

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

Pretreatment of Hybrid Ceramics Using Alumina (Al2O3) Nanoparticles, Hydrofluoric Acid, and Holmium: YAG Laser for Optimizing Surface Roughness, Shear Bond Strength, and Topography

Evaluation of different conditioning regimes i.e., hydrofluoric acid (HFA), sandblasting (SB), selfetching ceramic primer (SECP), and Holmium: YAG (Ho: YAG) laser on the surface roughness (Ra) and shear bond strength (SBS) of hybrid ceramics. One hundred and ten hybrid ceramic discs were fabricated using the CAD-CAM technique. The discs were randomly allocated into five groups. Group 1: No Conditioning (Control), Group 2: HFA etching, Group 3: SB, Group 4: SECP and Group 5: Ho: YAG laser. The quantitative measurement of the roughness (Ra) (n = 10) from each group was conducted using a profilometer. The dual cure resin cement was bonded on the remaining fifty samples. Shear bond strength (SBS) and failure analysis were performed using a universal testing machine (UTM) and stereomicroscope. One-way analysis of variance (ANOVA) with post hoc Tukey tests was used to assess and compare the mean values of Ra and SBS among study groups. Specimens pretreated with SB displayed the maximum Ra value and bond scores. The control specimens exhibited minimum Ra and SBS. Intergroup comparison analysis indicated that HFA and Ho: YAG laser-treated groups displayed comparable outcomes of Ra and bond integrity. Sandblasting using alumina particles proved to be the most favorable pretreatment modality for hybrid ceramic surface pretreatment for attaining optimum surface roughness and shear bond strength.

Comparison of Screw Loosening and Fracture Resistance in Different Hybrid Abutment Crown Restorations After Thermomechanical Aging.

To investigate the screw loosening and fracture resistance of different hybrid abutment crown restorations after thermomechanical aging. Restorations were produced from zirconia, lithium disilicate, and hybrid ceramics with a CAD/CAM system (n &#61; 10). Restorations and titanium bases (Ti-bases) were cemented, and the abutment screws were torqued to 30 Ncm. They were retorqued after 10 minutes, and then the removal torque values (RTVs) were measured. After 250,000 and 500,000 cycles of thermomechanical aging were completed, the RTVs were measured again, and removal torque loss (RTL) ratios were calculated. The specimens were subjected to a fracture resistance test after 750,000 cycles of thermomechanical aging, and the load at failure was recorded as the fracture resistance (N). The results were statistically analyzed (α &#61; .05). Aging was effective on the RTVs and RTL ratios (P < .001). The highest RTV was observed before aging; however, the RTVs significantly decreased and RTL ratios significantly increased after aging (P < .05). The fracture resistance values significantly differed among the ceramic materials. All lithium disilicate and hybrid ceramic specimens showed restoration fracture and most of the zirconia specimens showed Ti-base-related failure. Hybrid abutment crowns made of zirconia, lithium disilicate, and hybrid ceramics can withstand the average occlusal forces in the molar region; however, the ceramic type may affect the failure type. Retightening of the abutment screws after 10 minutes following the first tightening and annually may be beneficial to prevent the adverse effects of screw loosening on the integrity of the implant-abutment connection.

Survival Rates of Glass versus Hybrid Ceramics in Partial Prosthetic Restorations: A Scoping Review with Emphasis on Adhesive Protocols.

As dental practices and methodologies evolve, the emergence of novel materials adds complexity to clinical choices. While glass ceramics, particularly those based on lithium disilicate and leucite-reinforced variants, have been extensively researched and are well regarded for their attributes, hybrid ceramics remain relatively recent area of research that is less investigated. This review aims to evaluate the durability of glass and hybrid ceramics while assessing the role of various adhesive techniques on restoration longevity. Using a comprehensive search of PubMed and EMBASE, 84 articles from the past decade were found. Only eleven met the set criteria for analysis. The results underscore the urgent need for the extended monitoring of partial prosthetic restorations. The existing literature has significant gaps, hindering the attainment of dependable insights about these materials' long-term performance. For a clearer understanding of how different ceramic systems affect restoration survival rates, rigorous research involving more participants and uniform outcome documentation is vital.

Color Stability of Resin Hybrid Ceramic Materials in Comparison to Zirconia-Reinforced Lithium Silicate Ceramic.

Objectives: This in vitro study aimed to compare the effect of external staining agents (black tea and grape juice) on the color change of three hybrid ceramics including a new material in comparison to zirconia-reinforced lithium silicate. Materials and Methods: Ten samples of two hybrid dental ceramics including Vita Enamic (Vita Zahnfabrik) and Crystal Ultra (Digital Dental) in addition to a resin nanoceramic, Lava Ultimate (3M ESPE); and a zirconia-reinforced lithium silicate glass ceramic, Vita Suprinity (Vita Zahnfabrik) were prepared and immersed in black tea or grape juice for 30 days. A spectrophotometer was used to evaluate color change. All samples were carefully chosen in A3 shades or their equivalent. Two-way ANOVA and Bonferroni tests were used to analyze the color differences (ΔE00) among the materials and the staining solutions at a significant level of 0.05. Results: Significant color changes were observed in Vita Enamic and Lava Ultimate groups after immersion in both solutions (P<0.001). The least color changes (ΔE00) belonged to the Vita Suprinity (1.34) and Crystal Ultra (1.92) groups, respectively. Conclusion: The color changes of Vita Enamic and Lava Ultimate materials were beyond clinical acceptability. However, the mean color changes of Vita Suprinity and Crystal Ultra groups were clinically acceptable.

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.

Preheated Composite as an Alternative for Bonding Feldspathic and Hybrid Ceramics: A Microshear Bond Strength Study.

To evaluate the bond strength between alternative or conventional luting agents and indirect restorative materials. Blocks of a polymer-infiltrated ceramic network (PICN, Vita Enamic) and a feldspathic ceramic (FEL, Vita Mark II) were sliced and divided according to the luting agent: resin cement (PICN-RC, FEL-RC), flowable composite (PICN-FC, FEL-FC), or preheated composite (PICN-PH, FEL-PH). The ceramic surfaces were polished, etched with 5% hydrofluoric acid for 60 s, and then a silane layer was applied. Cylinders of the luting agents were built up on the ceramic surfaces. In half the samples, the microshear bond strength (µSBS) was tested after 24 h (baseline). The other half was tested after 5000 thermocycles (5°C-55°C) (aging). The failure modes were determined using a stereomicroscope, and the ceramic surfaces were analyzed using a scanning electron microscope. Data were statistically analyzed with two-way ANOVA. Thermocycling reduced the bond strength values of all experimental groups. Regarding FEL, the preheated composite obtained the highest results. Resin cement showed results similar to the flowable composite at baseline and after aging. The highest results of PICN were obtained from the preheated composite followed by resin cement and flowable composite. Significant differences among the three luting agents were observed before and after aging. The most frequent failures among the experimental groups were adhesive and cohesive in the ceramic. Bond strength results indicate that the preheated composite can be an alternative for adhesive cementation when applied on the tested feldspathic ceramic or PICN.

Advanced Hybrid Ceramics for Nuclear and Hydrogen Energy Applications

AbstractGlobal energy crisis has encouraged the need for sustainable energy resources, which is the viable alternate of providing effective energy operations and considered as remedy for the ongoing energy crisis. Development in the science and technology eases out plenty of issues that were once thought to be uphill. Presently, earth is being subjected to several grave issues which need to be addressed as soon as possible. Nuclear and hydrogen energy are the important areas which promise the optimistic way of handling the existential energy crisis due to cost, scarcity of resources and unavailability of considerable feedstock. Ceramics are the diverse inorganic materials which offer tremendous chemical and physical characteristics. Due to their structural, compositional and morphological versatility, advanced ceramics based hybrid materials can be exploited in nuclear and hydrogen energy applications as discussed in this review. Extensive survey outlined the applicability of ceramics in various nuclear science based applications as they include fissionable species and possess higher thermal conductivity, their enormous resistance towards radiation and refractoriness in fuels and in waste residuals due to their potential to hold radio nuclides and surveyed the scope of several metal oxides ceramics in carrying out hydrogen energy operations via overall water splitting.

Hybrid ceramic repair strength, surface roughness, and bond failure, using methylene blue-activated low-level laser therapy, Carbon dioxide, and Ti: Al2O3 laser

AimsTo evaluate the impact of various pretreatment regimes (LLLT, Ti-sapphire laser, CO2, and HFA-S) on hybrid ceramics, specifically focusing on their ability to enhance repair strength and minimize surface roughness (Ra). Material and methodsDiscs were made from hybrid ceramics and after disinfection were randomly divided into four groups based on different surface conditioning techniques. Each group consisted of 15 discs, resulting in a total sample size of 60. dics in group 1 was surface treated with Low-level laser therapy (LLLT) using methylene blue (MB), Discs in group 2 with Ti-sapphire laser, Discs in group 3 with CO2 laser, and discs in group 4 with HFA-S. Five samples from each group were assessed for Ra. The remaining 10 samples from each group underwent repair using a porcelain repair kit in adherence to the planned instructions. The bond strength of each sample in all groups was measured using a universal testing machine. Following the bond strength testing, the specimens from all study groups were analyzed to determine the mode of failure. To evaluate the data, a two-way analysis of variance (ANOVA) was used, followed by post hoc multiple comparisons. ResultsThe highest repair bond strength was observed in group 4 hybrid ceramics pretreated with HFA-S (19.05±0.79 MPa). The lowest repair bond scores were observed in group 1 hybrid ceramics preconditioned with LLLT in the presence of Photosensitizer (13.41±0.36 MPa). The highest Ra scores were exhibited in group 2 surface treated with Ti-sapphire laser (0.0515±0.16 µm) and the lowest Ra scores were observed in Group 4 HFA-S (0.0311±0.79 µm). Predominant bond failure among different investigated groups was cohesive. ConclusionThe current gold standard for hybrid ceramic conditioning is the use of hydrofluoric acid (HFA) combined with a silane coupling agent. Low-level laser therapy with methylene blue photosensitizer is not recommended for the treatment of hybrid ceramics.

SiO2/PDMS functionalized hybrid ceramics: effect of functional group on hydrophobic behavior

In this paper, the hydrophobic effect of the functional group in a hybrid ceramic synthesized from tetraethyl orthosilicate (TEOS) and polydimethylsiloxane (PDMS) is investigated. The hybrid ceramics were synthesized using di-butyl-di-di-tin laurate (DBTL) as a polycondensation catalyst and different concentrations of the polysiloxane chain varying from 20-40%w. Infrared spectroscopy confirmed the formation of the hybrid material, observing the corresponding signals for the siloxane bond (Si–O–Si) corresponding to the silica network, inorganic fragment (1100 cm–1 ) and those corresponding to the polymer chain (785 cm–1 ) besides, the Si–C bond of the polymer is presented at 1250 cm–1 . The amino functional group was identified as a low intensity signal at 1300 cm–1 (N–C) and 1204 cm–1 (Si– N); on the other hand, the phenyl group was present at 3080 cm–1 for the C–H group of the aromatic ring and with the C=C bond of the ring at 1429, 794 and 845 cm–1 . While the hydrophobic character was evaluated with the contact angle  obtaining a hydrophobic to superhydrophobic behavior with  de 110-130º.

Bond durability of a silane-containing self-adhesive and conventional resin cements to CAD/CAM glass and hybrid ceramics

To evaluate the effect of CAD/CAM materials surface treatments for bonding of different cementing systems on shear bond strength, including conventional and silane-containing resin cements, after 24 h and one year of water storage. Samples (12 mm × 6 mm × 1 mm) of each CAD/CAM material (IPS E.Max; Suprinity; Enamic; Cerec Bloc; IPS Empress) were divided into 4 groups: G1) 4.5% hydrofluoric acid (HFA) + silane + adhesive + RelyX Veneer (conventional); G2) HFA + Clearfil Ceramic Primer + Tooth Primer + Panavia V5 (conventional); G3) HFA + Panavia SA Cement Universal; G4) blasting with Al2O3 + Panavia SA Cement Universal. After the bonding procedures, two resin cement cylinders (1.5 mm × 1.5 mm) were constructed on each sample and tested after 24 h or one year of water-storage, using shear bond strength testing (n = 10). Data were submitted to generalized linear models’ analysis (p < .05). The conventional treatment for glass ceramics with HFA and silanization or priming (G1 and G2) did not necessarily yielded higher bond strength than the simplified technique (G3 and G4). For IPS E.Max and Suprinity, all protocols had bond strength reduction after one year. For Enamic, Cerec Bloc and IPS Empress, G3 did not reduced statistically at one year. Panavia SA Cement Universal seemed not appropriate when IPS E.Max and Suprinity were blasted with Al2O3. On the other hand, the bond strength to etched or blasted with Al2O3 Enamic, Cerec Bloc and IPS Empress showed no difference or was higher than conventional luting protocols.

Effect of hydrogen peroxide-based bleaching agents on the color dimensions and surface roughness of different milled restorative dental materials.

To compare the color dimensions, color discrepancies (ΔE00), and surface roughness of milled materials before and after the application of a bleaching agent. A total of 10 extracted molars were obtained. Each tooth was cut in transversal sections, to create discs (3 mm thick, 10 mm diameter) (control group). Disk specimens of 8 materials were fabricated: polymethyl methacrylate (PMMA) interim material (PMMA-Telio group), 2 resin nanoceramics: (RNC-Ultimate group) and (RNC-Cerasmart group), 2 hybrid ceramics: (HC-Shofu group) and (HC-Enamic group), lithium disilicate (LD-Emax group), zirconia reinforced glass ceramic (ZGC-Suprinity group), and zirconia (Zr group) (n=10). Color measurements were obtained using a spectrophotometer before and after applying 35% hydrogen peroxide-based bleaching agent. Pre- and post-bleaching surface roughness analysis were completed using a profilometer. Significant L*, a*, b*, and ΔE00 values differences were found (P < .05). Color discrepancies (ΔE00) ranged from 0.30 ± 0.14 to 4.82 ± 0.10. The highest color discrepancies were measured on the PMMA-Telio group, while the lowest color discrepancies were computed on the ZGC-Suprinity, RNC-Ultimate, and RNC-Cerasmart. Significant surface roughness differences were found (P <.05). The largest increase of surface roughness values between the pre- and post-bleaching measurements was obtained in the PMMA-Telio group with a mean ΔSa value of 4.73 ± 3.02, while the largest decrease of surface roughness values between the pre- and post-bleaching measurements was obtained in the Zr-InCeram group with a mean ΔSa value of -1.58 ± 0.10. The milled materials tested showed significant pre- and post-bleaching color and surface roughness discrepancies. Int J Prosthodont. doi: 10.11607/ijp.8359.

Er, Cr: YSGG, Nd: YVO4, and Ti: Sapphire Lasers for Surface Treatment of Hybrid Ceramics on Bond Durability, Surface Texture, and Debonding to Resin Cement: A Scanning Electron Microscopy (SEM) Analysis

Aims: To assess composite ceramics treated with Er, Cr: YSGG (ECL), Nd: YVO4, and Ti: Sapphire lasers to samples treated with hydrofluoric acid (HF) and silane (S) for shear bond strength (SBS) and surface roughness (Ra). Material and Methods: 60 disc-shaped HRC specimens. Surface conditioning techniques divided HRC-prepared discs into four groups. Samples in Group 1: HRC pretreated with normal 9.5% HF, Group 2: ECL, Group 3: Ti-Sapphire, Group 4: Nd: YVO4. The profilometer measured all ceramic discs’ average surface Ra. Universal testing machines tested the resin-ceramic interface SBS. Surface topography was assessed using SEM. Shear bond scores and Ra were compared using a one-way ANOVA. A Tukey’s post hoc test assessed several group comparisons. Results: Group 2 (Ti Sapphire Laser+S) samples scored highest in Ra and SBS. Group 4 Nd: YVO4+S had the lowest Ra and SBS values. HF 20 sec+S, (Ti Sapphire Laser+S), (ECL+S), and (Nd: YVO4+S) had comparable SBS and Ra values (p&gt;0.05). Conclusion: Laser-conditioned hybrid ceramics Er, Cr: YSGG, Nd: YVO4, and Ti-Sapphire lasers have shear bond strength and surface roughness comparable to 9.6% hydrofluoric acid.

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

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

Marginal accuracy of Cad/Cam occlusal veneers fabricated from glass and hybrid ceramics with two preparation designs: An in vitro study

Statement of the problem: Treatment of posterior teeth with occlusal wear is complex. Treatment involving more tooth reduction in these cases may be inappropriate. Occlusal veneers are less invasive approach. However, there is insufficient information available regarding the impact of the design of preparation and the type of ceramic material on the marginal adaptation of such occlusal veneers.Aim: This study aimed to examine marginal accuracy of occlusal veneers fabricated from two ceramic materials (Glass and Hybrid) with two designs of preparation (Planar and chamfer).Materials and Methods: Two mandibular first molar typodont teeth were prepared to receive 24 occlusal veneers. They were split into 2 equal groups (n=12) based on the material (Group (I): Lithium disilicate (Rosetta SM) occlusal veneers and Group (II): Hybrid ceramics (VITA ENAMIC) occlusal veneers). According to the preparatory design, each group then split into 2 subgroups (n=6)) (planar and finish line). Preparations were scanned, occlusal veneers were designed, milled and checked for seating under magnification. The vertical gaps between the cervical margin of the occlusal veneers and the outermost part of the finish line were measured using an optical microscope and image analysis software (20 readings per specimen). The mean vertical gap for each occlusal veneer was then calculated.Results: The Rosetta group showed a statistically non-significant higher gap mean value (26.32±3.61µm) than the Enamic group (23.15±5.15 µm) in the planar preparation design based on the results of student t-test (P=0. 2446 > 0.05). While for finish line preparation design, the Rosetta group recorded higher gap mean value (27.38±3.42 µm) than Enamic group (19.71±3.73 µm) and the difference was statistically significant confirmed by Student's t test (P = 0.004 < 0.05).Conclusion: Lithium disilicate ceramic and hybrid ceramic materials can be used to fabricate occlusal veneers. Superior vertical marginal fit was demonstrated using hybrid ceramic. More important than the preparation design is the veneer's material in terms of marginal accuracy.

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

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

Effectiveness of surface polishing after debonding of metal brackets from different CAD-CAM materials.

The purposes of this study were to compare and evaluate the surface texture of different restorative computer-aided design and computer-aided manufacturing (CAD/CAM) materials before bonding and after debonding of metal orthodontic brackets. Atotal of 60rectangular ceramic test specimens (n = 20 in each group) were prepared using feldspathic ceramic blocks (FLD; served as control), hybrid ceramic blocks (HC), and lithium disilicate ceramic blocks (LDC). Surface roughness (Ra) analysis was conducted using aprofilometer before bonding the metal brackets. After the debonding and polishing procedures, asecond surface roughness analysis was conducted on each specimen. The shear bond strength (SBS) test was applied to each specimen using auniversal test machine for debonding the metal brackets. The debonded specimens were examined under astereomicroscope and scored using a4-step adhesive remnant index (ARI). The Ra and SBS values and the ARI scores were saved, and the data were analyzed statistically at asignificance level of 0.05. One specimen from each group was examined under atomic force microscopy to visualize surface roughness. Furthermore, one specimen from each group was additionally prepared for scanning electron microscopy analysis. Statistically significant differences in SBS measurements were observed between all three groups. The highest SBS values were obtained from the FLD group, the lowest from the LDC group. The HC group showed significantly (P = 0.001) lower Ra values than the LDC and FLD groups after debonding and polishing. No significant differences were observed in the ARI scores between the groups. Hybrid ceramics could be asuitable alternative for fixed restorations in adult patients receiving subsequent treatments with fixed orthodontic appliances.

An In Vitro Comparison of Zirconia and Hybrid Ceramic Crowns With Heavy Chamfer and Shoulder Finish Lines.

Purpose This in vitro study aimed to compare the marginal fit and internal adaptation of computer-aided designed and computer-aided manufactured (CAD-CAM) zirconia and hybrid ceramic crowns on heavy chamfer and shoulder finish line designs using silicon replica method. Materials and methods Forty die samples were divided into four groups of 10 dies each. Out of 40 diecasts scanned, zirconia crowns were milled on 20 casts (10 prepared with shoulder and 10 prepared with heavy chamfer finish line design), whilehybrid ceramic crowns were milled on the rest of the 20 casts. After milling crowns, the silicone replica technique measured the marginal fit and internal adaptation. Results The heavy chamfer finish line design provided a better marginal fit than the shoulder finish line design for zirconia and hybrid ceramic crowns. Hybrid ceramic crowns had a better marginal fit and internal adaptation than zirconia crowns, both at heavy chamfer and shoulder finish line design. The gap at the margin was less than the axial and occlusal walls, and the maximum gap was observed in the occlusal area. In addition, the marginal gap was less than the internal gap, which showed a positive correlation with each other. Conclusion The study concluded that the difference in CAD-CAM materials and finish line designs influences marginal fit and crown restoration's internal adaptation.A heavy chamfer finish line design provides a better marginal fit for zirconia and hybrid ceramic crowns than a shoulder finish line design. Hybrid ceramic crowns have a better marginal fit and internal adaptation than zirconia crowns in heavy chamfer and shoulder finish lines.

Mechanical behavior of different machinable ceramic crowns using vertical and horizontal preparations: an in-vitro study

Objective: the aim of this study was to compare the mechanical behavior of different ceramics when used in thinvertical preparations versus traditional horizontal preparation. Material and Methods: two stainless-steel dieswere milled to simulate a minimally invasive vertical preparation (VP) and a traditional horizontal preparation(HP) for an all-ceramic crown of a maxillary first premolar. The stainless-steel dies were duplicated using epoxyresin. Eighty monolithic crowns were milled and divided into 2 groups according to preparation design. Eachdesign group was subdivided into 4 sub-groups according to material (n=10): IPS e.max CAD (lithium disilicate),Bruxzir shaded zirconia (full contour zirconia), CeraSmart (resin nanoceramic) and CEREC Tessera (advancedlithium disilicate). The crowns were cemented on their relevant epoxy resin dies using self-adhesive resin cement.All specimens were subjected to 15,000 thermocycles and then loaded to fracture in a universal testing machine.Data were analyzed using two-way ANOVA and Tukey pair wise comparison test. Results: the fracture resistancemean values of the VP (1344 + 118 N) was significantly lower than the HP design (1646 + 191 N). Ceramiccrowns made of full contour zirconia had higher fracture resistance mean values (2842 + 380 N) than advancedlithium disilicate (1272 + 125 N) followed by lithium disilicate crowns (983 + 52 N) and resin nanoceramic(882 + 61 N). Conclusion: both vertical and horizontal preparations, regardless the different ceramic materials,showed clinically acceptable fracture resistance values. KEYWORDSDental crown; Prosthodontics; Zirconia; Lithium disilicate; Hybrid ceramics.

10 - Translucency 0 f Zirconia and Hybrid Ceramic Monolithic Crowns

10 - Translucency 0 f Zirconia and Hybrid Ceramic Monolithic Crowns