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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.

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BACKGROUND: Since their introduction, there has been limited research regarding the mechanical properties of novel strength-gradient monolithic zirconia. In addition to that, studies evaluating the effect of different core-build materials on the strength of indirect restorations are scarce. Therefore, the aim of this study was to investigate the effect of using different core build-up materials on biaxial flexural strength of a new monolithic multilayered zirconia material. METHODS: Forty zirconia discs were fabricated from IPS e.max ZirCAD Prime (Ivoclar Vivadent AG, Schaan, Liechtenstein) and divided into 2 groups (n = 20). Forty composite discs were prepared from Tetric N-Ceram (Ivoclar Vivadent AG, Schaan, Liechtenstein) and MultiCore Flow (Ivoclar Vivadent AG, Schaan, Liechtenstein). The zirconia discs were adhesively cemented to the 2 types of composite forming 2 groups (Zirconia-Tetric N-Ceram and Zirconia-MultiCore Flow). Biaxial flexural strength was determined using a piston-on-3-ball test. The data were statistically analyzed with an independent t-test for significant differences (p = 0.05). RESULTS: Tetric N-Ceram had significantly higher strength than MultiCore Flow (p < 0.001) but no statistically significant differences were found in strength values between Zirconia-Tetric N-Ceram and Zirconia-MultiCore Flow bilayered samples (p = 0.27). CONCLUSIONS: It was concluded that although the tested composite core materials significantly differ in their biaxial flexural strength values, they had no influence on the biaxial flexural strength of the overlying zirconia.

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BACKGROUND: A posterior tooth's occlusal surfaces and the proximal surface can be restored by using an inlay, which is an intra-crown cast reconstruction without affecting the cusps of the tooth. When an inlay is prepared using an indirect approach, issues with traditional filling approaches, including poor morphology of the occlusal aspect or proximal aspect, inadequate resistance to wear, or subpar mechanical qualities of the directly inserted filler substance, are overcome. AIM: The current study was conducted in order to compare and assess the resistance to fracture of dental materials used in the preparation of inlay restorations indirectly, like composite restorations prepared by laboratories indirectly, inlays formed indirectly of monolithic translucent ceramic derived from zirconia, and inlays formed indirectly of traditional monolithic ceramic derived from zirconia. METHODS AND MATERIALS: For the investigation, 100 human premolars of the maxilla that were extracted recently were chosen. A self-polymerizing acrylic resin was used to incorporate the tooth roots in a band made up of polyvinyl chloride up to 2 mm below the cement-enamel junction. The dimension of the band was 1.3 cm by 1.9 cm. Five categories of 20 specimens of such teeth were formed. Category one, featuring teeth in good condition, acted as the positive control category. The remaining four categories of teeth received inlay tooth preparation. The research samples underwent thermocycling after having been preserved for a full week following the cementation of inlay replacements. Then, in a universal testing apparatus, every sample endured axial compressive force with a metal globe delivered vertically at a crosshead rate of 1 mm/minute. The amount of force necessary to cause a fracture was measured in Newtons (N). RESULTS: The mean values of resistance against fracture in specimens in categories 1-5 were 1208.87 N, 614.89 N, 733.05 N, 1179.14 N, and 1148.49 N, respectively. The values of fracture resistance in specimens where an inlay cavity preparation was done but not filled were lower than those in traditional monolithic ceramic derived from zirconia and tooth specimens with inlays formed of monolithic translucent ceramic derived from zirconia, and the difference was significant statistically (p=0.001). The values of fracture resistance in composite inlay restorations prepared by laboratories were indirectly lower than those of monolithic ceramic derived from zirconia and tooth specimens with inlays formed of monolithic translucent ceramic derived from zirconia, and the difference was significant statistically (p=0.004). CONCLUSION: Within the constraints of the current investigation, we can state that indirect zirconia-based ceramic products offer adequate fracture resistance, but additional research is needed to determine how well these materials hold up under different types of pressures before employing them in clinical tooth restoration.

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AIM: The aim of the present article is to describe a new method to reduce the undesirable loss of material thickness that results from overmilling due to the tool diameter compensation correction of common CAD/CAM software. MATERIALS AND METHODS: Today's CAD/CAM software (eg, 3Shape or Exocad) specifies the same tool diameter compensation for different ceramics. In the case of zirconia ceramics milled in the raw state, this leads to excessive milling of the inner surfaces of crowns, which results in unnecessarily large cementation gaps and a restoration that is thinned out from the inside. By manually reducing the preset correction in the digital design process by the volumetric sintering shrinkage factor specified by the manufacturer, excessive thinning of the zirconia can be avoided. RESULTS: The inner geometry of the restorations changes only slightly after manually reducing the preset tool diameter compensation correction. Consequently, a design of the restoration with the required minimum interocclusal thickness yet with accurate passive seating and marginal fit is possible without any further interventions. CONCLUSIONS: Understanding the specifics of the subtractive fabrication process as well as the properties of the restorative materials is a key factor in achieving optimal clinical outcomes with all-ceramic restorations fabricated with CAD/CAM technology. The use of monolithic zirconia combined with a calculated reduction in the preset tool diameter compensation correction might be beneficial in cases with thin or uneven geometry.

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Advances of digital technology are rapidly adopted in dental practice. This systematic review aimed to collect evidence on the accuracy of fit of different types of fixed dental prostheses (FDPs) fabricated through digital, conventional, or combination impression techniques. Data collection was based on the guidelines of the preferred reporting items for systematic reviews and meta-analyses (PRISMA). Two databases (PubMed, Scopus) were searched for articles in English published between 2010 and 2021 resulting in 480 articles. Of those, 35 studies fulfilled the inclusion criteria. These articles referred to three groups of materials/techniques including all-ceramic (zirconia; lithium disilicate) and porcelain-fused-to-metal (PFM) restorations. Results showed clinically acceptable marginal fit (< 120 µm) for all materials and impression techniques. Α fully digital workflow appears more promising for the construction of short-span zirconia FDPs. Nevertheless, most articles evaluated marginal/internal fit of single crowns or short-span FDPs in vitro, while clinical data are limited for long-span FDPs. The necessity for gingival retraction remains a major drawback of all impression techniques, increasing procedural time and patient discomfort. Besides, factors related to the fabrication process, including milling and 3D printing of working models significantly influence the outcome. Overall, there still some way to go before digital technology can be incorporated in complex treatment plans in prosthodontics.

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Background and Objectives: Modern esthetic dentistry is based on all-ceramic restorations. Dentists still have reservations about using these restorations due to a lack of understanding of the cementation technique, which depends on the type of ceramic used. The aim of the study is to evaluate the approaches and practices of clinicians regarding the adhesive cementation of all-ceramic restorations. Materials and Methods: An online questionnaire regarding the use of all-ceramic restorations and their bonding methods was designed by distinguishing the cementation of oxide and silica-based ceramics. The survey included dentists practicing in Timiș County, Romania. The questionnaire and the evaluation of the answers were designed based on the techniques and evidence from the literature. Results: Considering the work experience, we obtained two groups: group 1-1 to 6 years and group 2-6 to 9+ years. The results revealed significant values when comparing the two groups in the surface protocol and decontamination (p = 0.005), type of cement used (p = 0.002), and isolation techniques (p = 0.002). Conclusions: The results show that many clinicians need additional training to improve their cementing technique and avoid the confusion caused by insufficient information about the interrelationship between the type of ceramic and the cementation procedure.

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PURPOSE: Several studies have compared digital intraoral scanners and conventional impressions. The accuracy of these two methods in terms of marginal accuracy of lithium disilicate crowns is not well-established, yet. The purpose of this study was to systematically review available publications on marginal fit of single-unit, full-coverage, tooth-supported lithium disilicate restorations. METHODS: Pubmed, Web of Science, Cochrane, EMBASE, and Scopus were electronically searched along with a manual search. After critical appraisal, data from selected studies were extracted and mean marginal difference with a 95% confidence interval was calculated. Meta-analysis of the collected data was conducted using STATA software. RESULTS: The meta-analysis revealed similar marginal gap values in intraoral scanners with conventional groups (p>0.05) and in intraoral scanners with extraoral canners (p>0.05). CONCLUSION: No significant difference was seen between digital and conventional impressions or intra- and extraoral scanners for marginal accuracy of lithium disilicate crowns.

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Purpose: To evaluate the effect of different placing strategies performed in the connector area on fracture resistance and fracture behaviour of monolithic multi-layered translucent zirconia fixed dental prostheses (FDPs). Materials and Methods: Thirty 3-unit monolithic FDPs were produced and divided into three groups (n = 10) based on the different strategies for placing the connector area of FDPs in multi-layered zirconia blank with varying contents of yttria ranging from 4 to 5 mol%. The groups were as follows: FDPs with connectors placed in dentin layer with 4 mol% yttria content, FDPs with connectors placed in gradient layer, and FDPs with connectors placed in translucent layer with 5 mol% yttria content. A final group (n = 10) of conventional monolithic zirconia with a monolayer of yttria content (4 mol%) has been used as a control group. The specimens were artificially aged using thermocycling and pre-loading procedures and subsequently loaded to fracture using a universal testing machine. Fracture loads and fracture behaviour were analyzed using one-way ANOVA and Fisher's exact tests and statistically evaluated (p ≤ 0.05). Results: There were no significant differences in fracture loads among the groups based on the placing strategies of the connector area of the FDPs in the multi-layered translucent zirconia blank (p > 0.05). There was no significant difference in fracture loads between monolithic multi-layered translucent zirconia and conventional monolithic translucent zirconia materials (p > 0.05). Fracture behaviour of FDPs with connector area placed in translucent layer differed significantly compared to FDPs with connector area placed in dentin layer and FDPs in control group (p = 0.004). Conclusion: The placing strategies of the connector used in the computer aided design and manufacturing procedures do not considerably affect fracture resistance of monolithic FDPs made of multi-layered translucent zirconia. Monolithic FDPs made of multi-layered translucent zirconia show comparable strength to FDPs made of conventional translucent zirconia, but with different fracture behaviour.

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BACKGROUND: To determine the survival rates of endodontically treated posterior teeth (EDPT) restored with partial coverage all-ceramic crowns with or without the use of fiber posts. METHODS: MEDLINE and Cochrane searches were conducted in order to identify Randomized Clinical Trials (RCTs) related to endodontically treated posterior teeth restored with partial coverage crowns. The search period was extended until February 2020 and only in vivo, human, and studies in the English language were included. A manual search was also conducted and additional articles, if found, were included in the database. RESULTS: The initial search for the selected databases identified 495 studies, which were all screened for inclusion through titles, abstracts and full-text reading. Out of these 495 studies, only one article met the eligibility criteria and was included in this systematic review. Statistical analysis could not be performed. CONCLUSIONS: Only one RCT was identified in this systematic review. More clinical evidence is necessary to assess the survival rate of EDPT with partial-coverage crowns. This systematic review failed because it did not find scientific evidence to support the use of indirect bonded restorations on EDPT.

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The fatigue behavior and FEA analysis of different ceramic materials cemented over distinct substrates for implant-supported crowns were evaluated in this study. Discs of 10 mm in diameter of both restorative and substrate materials were made and randomly allocated into pairs (n = 15) considering the two study factors: 'restorative ceramic material' (1 mm thickness) - polymer-infiltrated ceramic network (PICN), lithium disilicate (LD), zirconia-reinforced lithium silicate (ZLS), or translucent zirconia (TZ); and 'foundation substrate' (2 mm thickness) - polyetheretherketone (Peek) or yttrium-stabilized zirconia (YZ). Adhesive cementation was made with a dual cure resin cement. Fatigue testing was run using the step-stress methodology: initial load of 200 N for 5000 cycles, followed by steps of 10,000 cycles starting at 400 N up to 2800 N or until failure, step size of 200 N, frequency of 20 Hz. Data were analyzed by the Kaplan Meier and log-rank post-hoc tests. Fractography analysis (stereomicroscope and SEM) and FEA were also performed. Both factors under study and their interaction statistically influenced the fatigue failure load (FFL), cycles for failure (CFF) and survival rates (p < 0.001). The restorative materials bonded to YZ had higher FFL and CFF than when adhering to Peek, while restorative materials with more crystalline content (TZ and ZLS) showed higher FFL and CFF than LD and PICN. The fractography analysis showed that all materials bonded to YZ resulted in failures starting at the occlusal surface (Hertzian cone cracks), while materials bonded to Peek had radial cracks from the ceramic-cement intaglio surface. FEA analysis showed that tensile stress concentration decreased in the intaglio surface when testing the restorative material over a stiffer (YZ) foundation substrate. In addition, the higher the restorative material's crystalline content, the more the stress is concentrated within the material (TZ > ZLS ≥ LD > PICN) when bonded to the same foundation substrate. Thus, it concluded that a stiffer foundation substrate (YZ) enhances the load-bearing capacity under fatigue of the restorative set; that restorative materials with higher crystalline content results in higher fatigue performance of the set, regardless of the foundation used; and that the foundation material influences the failure pattern of the restorative set.

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Purpose Under thin, partial coverage restoration the proper cement thickness to be clinically employed still remains an issue. The aim of this study was to determine the failure and success rates of simplified lithium disilicate occlusal veneers as a function of cement thickness. The null hypothesis was that cement thickness has no effect on the fatigue resistance.Methods Sound human molars were severed in a plane parallel to the occlusal surface to create a flat dentin surface surrounded by enamel edges. Forty-five occlusal veneers 1.0 mm thick (IPS e.max CAD LT) were luted to the teeth with Multilink Automix resin cement, creating 3 experimental groups (n=15) with cement thicknesses of 50, 100, and 200 µm. The restorations were fatigue-cycled using a ball mill machine containing zirconia and stainless steel spheres. Twelve 60 min cycles were performed. Survival statistics were applied to "failure" and "success" events, comparing the three groups using a log-rank Mantel-Cox test and a log-rank test for trends (alpha = 0.05).Results The failure and success rates were not significantly influenced by cement thickness (P = 0.137 and P = 0.872, respectively); thus, the null hypothesis was accepted. However, when log-rank test for trends was applied to failure events, the tendency to have less failures with increasing thicknesses was found statistically significant (P = 0.047).Conclusions The cement thickness within the range adopted here did not have a significant effect on the failure or success rate of lithium disilicate occlusal veneers when exposed to randomized impact stresses generating fatigue phenomena.

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OBJECTIVE: To assess the clinical and esthetic outcomes and patient satisfaction of screw-retained one-piece implant crowns fabricated with zirconia abutments after a 4.5- to 8.8-year follow-up. MATERIAL AND METHODS: Thirty-two patients (12 women and 20 men), who received 40 implant single crowns in anterior and premolar sites, were included in this prospective study. All restorations were based on ceramic hand-veneered customized CAD/CAM zirconia abutments. The follow-up consisted of clinical and radiological examinations. The pink esthetic score-white esthetic score (PES-WES) was used to evaluate the esthetic outcome. Patients' satisfaction was assessed via visual analog scale (VAS). RESULTS: Implant and prosthetic survival rates were 100% and 97.5%, respectively. Mean marginal bone loss was -0.17 mm (SD 1.16 mm). Probing depth was ≤4 mm in 98.7% and 5 mm in 1.3% of the sites; 8.3% of them were bleeding on probing positive. No technical or biological complications were observed except for one abutment fracture. The mean PES-WES scores were 7.0 and 7.1, respectively. VAS scores (10-point) of 9.41 for function and 9.26 for esthetics showed high patient satisfaction. CONCLUSION: After a mean observation period of 6 years and 7 months, screw-retained implant crowns based on veneered customized CAD/CAM zirconia abutments with conical connection showed very good clinical performance and may be recommended for the replacement of missing anterior and premolar teeth. (ClinicalTrials.gov # NCT04370314).

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OBJECTIVES: This survey evaluated dentists' use of adhesive bonding methods of all-ceramic restorations over a period of twelve years. This is a follow-up survey which had been undertaken in 2007, 2011, and in 2015 [1]. METHODS: A multiple choice questionnaire regarding adhesive bonding methods for all-ceramic restoration was developed and handed out in 2007 and 2019 to dentist participating in a local annual dental meeting in Northern Germany. The questionnaires were evaluated on the basis of evidence-based techniques from the scientific literature. RESULTS: Data from 93 questionnaires (2019) were compared with 90 evaluated questionnaires from 2007. Bonding of oxide ceramic had improved over the years of observation (7% to 62%) whereas evidence-based bonding of silicate ceramic restorations decreased from 66% to 38%; common mistakes were using air abrasion on silicate surface. Females showed better values for correct adhesive cementation than males (f: 39-50%, m: 22%-41%). A correlation between correct cementation and years of professional experience could not be revealed. CONCLUSION: Incorrect bonding of oxide ceramic restorations decreased within the 12 years investigated whereas there was no improvement of evidence-based bonding procedures of silicate ceramics. Still a high number of survey participants need additional training in bonding techniques.

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PURPOSE: To evaluate the influence of the framework designs on the stress distribution within tooth-supported partially veneered fixed dental prostheses (FDPs) made of translucent zirconia under simulated loads using a three-dimensional finite element analysis (3D-FEA). MATERIAL AND METHODS: For a linear 3D-FEA, simplified 3D solid models of prepared abutment teeth (first premolar and first molar) with different 3-unit FDPs were created. The models with different FDP designs-monolithic zirconia (control); semi-monolithic zirconia with 0.3 mm veneer thickness (SM0.3); semi-monolithic zirconia with 0.5 mm veneer thickness (SM0.5); semi-monolithic zirconia with 0.5 mm veneer thickness supported with cap design (SMC), and semi-monolithic zirconia with 0.5 mm veneer thickness supported with wave design (SMW)-were analyzed using 3D-FEA. The elastic properties of the components (bone, dentine, cement, translucent zirconia, and veneering porcelain) were obtained from the published data for FEA. Simulated static loading forces (300 N) were applied at 10° oblique direction over six points in the occlusal surfaces of the FDPs. Maximum principal stress, shear stress, and safety factor were calculated and analyzed among the different models. RESULTS: Semi-monolithic with cap design showed the smallest maximum principal stress levels in the veneering porcelain compared to all other models (SM0.3, SM0.5, SMW). The SM0.3 had lower maximum principal stress levels in the veneering porcelain compared to SM0.5. Regarding stresses in the zirconia framework, all models had comparable results in maximum principal tensile stresses, except SMW had a lower value. Maximum principal stress levels were located in the veneer component of SM0.3, SM0.5, and SMW, whereas, such levels were observed in the cervical areas of the zirconia frameworks of SMC and control. The SM0.3 had the highest maximum shear stress levels at the zirconia-veneer interface, while SMW had the lowest shear values. The 3D-FEA models with different FDP designs showed different minimum safety factor levels. CONCLUSIONS: Framework and veneer designs play a significant role in the stress distribution of the partially veneered zirconia FDPs under loading. The FDPs with zirconia frameworks with cap design minimize the maximum principal tensile stress in the veneering porcelain. The FDPs with 0.3-mm-veneering porcelain show low maximum principal tensile stress in the veneering porcelain, but highest maximum shear stress at the zirconia-veneer interface. The FDPs with wave design of zirconia frameworks minimize the maximum shear stress considerably.

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The aim of this study was to evaluate the effects of the kinds of veneering ceramics and veneering methods on the debonding/crack initiation and 3-point flexural strengths in bilayered zirconia core and veneering ceramic composites. Zirconia block was used as core material, and Cerabien ZR and Lava Ceram for the layering technique and IPS e.max ZirPress and Amber LiSi-POZ for the heat pressing technique were used as veneering materials. Both debonding/crack initiation and 3-point flexural strengths of bilayered zirconia core and veneering ceramic composites as well as the bi-axial flexural strengths of veneering materials, were higher when using heat pressing technique than layering technique. It was identified that not only bonding strength between zirconia core and veneering materials but also the intrinsic strength of veneering ceramic should be high to prevent chipping of veneering material.

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OBJECTIVES: Ceramics can simulate the visual character of the tooth substance successfully and are biocompatible materials. However, a wide range of ceramic materials and systems on the market are available for use in dentistry. Therefore, it is the aim of this article to provide an overview of dental ceramics, their classifications, methods of construction, and clinically relevant aspects that enable the reader to select the most appropriate ceramic for a particular clinical situation. MATERIAL AND METHODS: The PubMed (MEDLINE) search engine was used to gather the most recent information on dental ceramics. The search was restricted to a ten-year period (January 1, 2010-December 31, 2019) and only English-language studies. A Boolean search of the PubMed data set was implemented to combine a range of keywords: (ceramics OR all-ceramics OR dental porcelain OR polycrystalline OR porcelain fused to metal OR ceramometal OR procera OR e max OR zirconia OR In-ceram OR Inlays OR Onlays OR Overlays OR Endocrown) AND (survival rate OR success rate OR clinical outcomes OR classification) AND (humans). Studies were also obtained by manual searches and from Google Scholar. RESULTS: By using this process, 2173 articles and studies were obtained. More studies were also obtained by manual searches and from Google Scholar. The most relevant published studies were chosen and used in the current review. CONCLUSION: All-ceramic restoration use has increased in recent years. This increase has been attributed to patients' demand for good aesthetics and an improvement in the materials' mechanical and aesthetic properties as well as to required minimally invasive tooth preparation and the methods of fabrication. The success of ceramic restorations depends on several factors, such as selection of material, restoration design, occlusion, and cementation media.

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The development of dental restorative materials that mimic tooth-like properties provided by graded structures, aesthetics and properties such as strength, damping capacity and the ability for a continuous remodeling according to the biomechanical solicitation is a great challenge. In this work, damping capacity and dynamic Young's modulus of Y-TZP/porcelain composites for all-ceramic dental restorations were studied. These mechanical properties were assessed by dynamic mechanical analyses (DMA) at frequencies of 1, 5 and 10 Hz, over a temperature ranging from 0 to 60 °C, simulating extreme conditions when a cold or hot drink is experienced. The results showed that porcelain and porcelain-matrix composites exhibited higher damping capacity while Y-TZP and Y-TZP-matrix composites presented higher dynamic Young's modulus. Furthermore, while damping capacity is strongly influenced by the temperature, no significant difference in dynamic Young's modulus was found. For both damping and modulus properties, no significant influence of frequency was found for the tested materials. Based on the obtained results and also on the known advantages of the graded Y-TZP/porcelain structures over traditional bi-layer solutions (e.g., improved bending strength, enhanced mechanical and thermal stress distribution), a novel design of all-ceramic restoration with damping capacity has been proposed at the end of this study. A positive impact on the long-term performance of these all-ceramic restorations may be expected.

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OBJECTIVES: The objective of this clinical study was to compare and assess the clinical performance of tooth-supported and implant-supported zirconia single crowns with sintered veneering caps. METHODS: In this prospective study, 118 patients with a total of 220 single crowns placed on 106 teeth (69 vital teeth, 37 endodontically treated teeth) and 114 implants in molar and premolar regions were examined during a mean observation period of 42 months. The restorations were evaluated for technical failures such as veneering porcelain fractures (chipping), surface quality, marginal fit, and the interface quality of the coping and sintered veneering. The soft tissue status was assessed using the modified Silness and Löe's plaque and gingival index (mPI) and the modified Muhlemann sulcus bleeding index (mSBI). Tooth-supported crowns were checked for secondary caries and hypersensitivity during the follow-up period. Recalls were performed every 6 months. RESULTS: The 3-year Kaplan-Meier success probability was 98.2% and 100% for implant- and tooth-supported crowns, respectively. A significant difference could be detected between the implant-supported and tooth-supported zirconia single crowns, in terms of their chipping rate (p = 0.039). Veneering material fractures were recorded on two implant-supported restorations (1.8%). No veneering fractures occurred on tooth-supported single crowns. The plaque and gingival index and sulcus bleeding index showed stable and healthy soft peri-implant and periodontal tissues. Neither loss of vitality nor secondary caries occurred on tooth-supported crowns. CONCLUSIONS: Zirconia-based single crowns with a sintered veneering cap showed promising clinical results on both tooth and implant abutments; however, the dental implants were more prone to complications. In terms of clinical significance, high-strength ceramic with a sintered veneering cap can be recommended for prosthetic treatment of both tooth- and implant-supported single crowns in molar regions. CLINICAL RELEVANCE: This study provides valuable information for further application of all-ceramic restorations.

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RATIONALE: Advancements in dental biomaterials have led to the introduction and application of ceramic-based restorations in dental practice. Currently, ceramic restorations are used in crowns and fixed partial dentures. The optical properties of ceramic restorations are comparable to natural teeth in terms of light scattering and transmission. However, the translucency of ceramic restorations could be a limitation if cemented over metal posts or severely discolored dentin. Therefore, accomplishing the maximum esthetic outcome mandates adequate management of severely discolored foundation. PATIENT CONCERNS: The patient wanted to improve the esthetic of his anterior teeth. DIAGNOSIS: This case report describes a clinical case in which the patient had defective restoration in his upper anterior teeth and base-metal cast post and core in his left lateral incisor (tooth #22). INTERVENTIONS: Metal-free full crowns were used in the anterior zone of the maxilla with the help of e.max HO (high opacity) coping to mask the dark core buildup of the base-metal post and core on tooth #22. OUTCOMES: The color of the substrate was masked completely. The esthetic of the anterior teeth was improved and the patient was highly satisfied with the outcome. LESSONS: e.max HO coping offers clinically acceptable masking ability.

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PURPOSE: To investigate the load-bearing capacity and failure mode of monolithic zirconia fixed dental prostheses (FDPs) fabricated with different connector designs and embrasure shaping methods. MATERIALS AND METHODS: Seventy four-unit zirconia FDPs (with two premolar pontics) were fabricated and divided into seven groups (n = 10) according to the different connector designs gained by using different embrasure shaping methods. The groups were as follows: monolithic FDPs fabricated with sharp embrasures, monolithic FDPs fabricated with blunt embrasures, monolithic FDPs fabricated with blunt embrasures and no occlusal embrasures, two groups of monolithic FDPs fabricated with blunt embrasures and interproximal separations made with diamond discs at the soft stage and at the fully sintered stage, and monolithic FDPs fabricated with blunt embrasures and interproximal separation accentuated by localized porcelain build-up. A final group was used as a control group, where fully veneered traditional zirconia FDPs were fabricated with default milling settings. The FDPs were artificially aged and loaded to fracture. Load to fracture and failure modes were analyzed by one-way ANOVA, Tukey's post hoc test, and Fisher exact test (α = 0.05). RESULTS: The FDPs fabricated with interproximal porcelain separation showed significantly the highest load to fracture (1038 N ± 82) of all groups (p < 0.001), with no significant difference compared to the FDPs with no occlusal embrasures (934 N ± 175; p ˃ 0.29). The FDPs fabricated with blunt embrasures showed significantly higher load to fracture (873 N ± 115) compared to the FDPs in the control group (689 N ± 75) and the FDPs with sharp embrasures (417 N ± 87; p < 0.001). There were no significant differences between the FDPs with sharp embrasures (417 N ± 87) and the FDPs with interproximal disc separations (467 N ± 94; p ˃ 0.23). Failure mode of the FDPs fabricated with sharp embrasures and interproximal disc separations differed significantly compared to the FDPs in the other groups (p < 0.001). CONCLUSIONS: Sharp embrasures and interproximal separations made with diamond discs significantly decrease the load-bearing capacity of monolithic zirconia FDPs compared to FDPs made with blunt embrasures. Blunt embrasures in combination with localized porcelain build-up produce FDPs with high load-bearing capacity in relation to loads that might be expected under clinical use.

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