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Papers by Bogna Stawarczyk

Quintessence International, 2017

This article presents the historical development of the different generations of zirconia and the... more This article presents the historical development of the different generations of zirconia and their range of indications, from veneered to monolithic zirconia restorations. Because of the large extent of this topic, it is divided into two parts. In Part I, the mechanical and optical properties of the three generations of zirconia materials are discussed critically and theoretically. A short summary is given of the current scientific literature, investigating the third generation of zirconia comparatively regarding the properties discussed.

Bending moment of implants restored with CAD/CAM polymer-based restoration materials with or without a titanium base before and after artificial aging

Dental Materials, Sep 1, 2022

Zirkonoxidabutment auf Titanklebebasis – eine aktuelle Literaturübersicht

ZWR, Aug 1, 2018

Fracture load of different veneered and implant-supported 4-UNIT cantilever PEEK fixed dental prostheses

Journal of The Mechanical Behavior of Biomedical Materials, May 1, 2022

OBJECTIVES To determine the fracture load before and after artificial aging of implant-supported ... more OBJECTIVES To determine the fracture load before and after artificial aging of implant-supported 4-unit cantilever fixed dental prostheses (FDP) with frameworks made of two differently filled polyetheretherketone (PEEK) compounds and veneered using three different techniques. METHODS A total of 120 duplicate 4-unit FDP frameworks were produced (n = 60 milled from PEEK, 20% TiO2 filled and n = 60 pressed from PEEK, 30% TiO2 filled) and veneered using three different techniques: (i) digital veneerings, (ii) conventional resin composite veneerings and (iii) prefabricated veneers (n = 20 per subgroup). The FDPs were adhesively bonded to titanium abutments and the fracture load was measured in a universal testing machine (1 mm/min) before and after artificial aging in a mastication simulator (1,200,000 cycles, 50 N, TC: 5/55 °C, 6000 cycles). The fracture patterns were analyzed using digital microscopy. Data were analyzed using the Kolmogorov-Smirnov test, two-way ANOVA, post hoc Scheffé, Chi2-test (p < 0.05), and Weibull modulus m, as well as fracture patterns using the Ciba-Geigy table. RESULTS Veneering technique and filler content significantly affected the fracture load (p < 0.001). Prefabricated veneers showed higher fracture load (p ≤ 0.001) whereas digital and conventional veneerings were similar (p = 0.451). PEEK with 30% filler content presented higher fracture load (p < 0.001) compared with PEEK with 20%. Aging showed no effect on fracture load (p = 0.176). Regarding fracture types, no significant differences were found among the groups (p = 0.055). CONCLUSIONS Filler content of PEEK compound as well as veneering technique influenced fracture load while aging had no effect on fracture load. FDPs made of PEEK with 30% of filler content veneered using prefabricated veneers had the highest fracture resistance.

Journal of Prosthetic Dentistry, Apr 1, 2021

With favorable esthetics and long-term survival, fixed dental prostheses (FDPs) with tooth-colore... more With favorable esthetics and long-term survival, fixed dental prostheses (FDPs) with tooth-colored veneers are considered the gold standard in restorative dentistry. The conventional material combination of a ceramic veneer fused to an alloy framework has been successfully used for many decades. With the development of new manufacturing processes, the use of base metal alloys such as cobalt chromium (CC) or titanium (TIT) is on the rise. Computer-aided design and computer-aided manufacturing (CAD-CAM) milled metal-ceramic crowns show high mechanical stability, especially for multiunit FDPs. 2 Zirconia (ZIR) has been investigated as a suitable framework material for veneered FDPs. The advantages consist of a rapid and cost-effective manufacturing process, excellent esthetics and biocompatibility, and improved mechanical properties compared with other ceramics. Although chipping of the ceramic veneer is a common technical complication for all veneered FDPs, ZIR restorations F.W. and M.K. contributed equally to this work.

Comparison of mechanical properties of different reinforced glass-ceramics

Journal of Prosthetic Dentistry, 2022

STATEMENT OF PROBLEM Data concerning the mechanical properties of the newly developed lithium dis... more STATEMENT OF PROBLEM Data concerning the mechanical properties of the newly developed lithium disilicate ceramic HS10PC are lacking. PURPOSE The purpose of this in vitro study was to investigate the flexural strength (FS), Martens hardness (HM), indentation modulus (EIT), fracture load (FL), and wear resistance (WR) of HS10PC compared with those of the established glass-ceramics IPS e.max Press and IPS Empress Esthetic. MATERIAL AND METHODS Four pressable glass-ceramics were examined: HS10PC (estetic ceram ag), IPS e.max Press low translucency (LT) and high translucency (HT; Ivoclar Vivadent AG), and IPS Empress Esthetic (ES; Ivoclar Vivadent AG). For each material, a total of 85 specimens were fabricated. Specimens were subdivided into 4 groups for FS (n=30), HM, EIT (n=10), and FL measurement according to the Voss test after artificial aging in an autoclave (n=15), artificial aging in a mastication simulator (n=15), and no artificial aging (n=15). In addition, WR (n=10) was measured after 240 000, 600 000, and 1 200 000 masticatory cycles. Data were statistically analyzed using the global univariate ANOVA, the Scheffé post hoc and paired t tests, and Weibull distribution (α=.05). RESULTS HT showed the highest FS, while ES presented the lowest FS of all groups (P<.001). ES showed lower values for HM (P<.001), EIT (P<.001), and FL for specimens treated in an autoclave and mastication simulator (P<.001) compared with all other groups. An increase in the wear of the ceramic and enamel antagonist between 240 000 and 1 200 000 masticatory cycles was observed for all groups (P<.001). After 1 200 000 masticatory cycles, HS10PC presented less wear of the ceramic than the other 3 materials (P=.003). CONCLUSIONS The newly developed lithium disilicate ceramic HS10PC showed comparable results with the established IPS e.max Press for FS, HM, EIT, FL, and WR. Lithium disilicate ceramics presented higher mechanical results than the leucite-reinforced ES, with all the ceramics showing similar results for the WR of the enamel antagonist.

$Research paper thumbnail of Comparison of fracture toughness measurements for zirconia materials using two test methods$

Dental Materials Journal, Sep 27, 2019

To determine the influence of the fracture toughness (KIC) methods [single-edge-V-notch-beam (SEV... more To determine the influence of the fracture toughness (KIC) methods [single-edge-V-notch-beam (SEVNB) and chevron-notch-beam (CNB)] as well as an optional heat treatment on the KIC of three different zirconia generations (1st: ZI, 3rd: FX, 4th: HT). One hundred and twenty specimens each (3×4×45 mm) were fabricated, sintered, notched (n=360) and half of them heat treated before KIC measurements with 4-point-flexural-strength test. SEM images of the notches were recorded. Highest KIC was found for ZI followed by HT and FX. SEVNB resulted in significantly higher KIC than CNB. Heat treatment resulted in decrease for SEVNB and increase for CNB of KIC (except for FX). Groups tested using CNB showed higher reliability of values (Weibull modulus) than tested using SEVNB. SEM images present crack path and fracture surface. Different zirconia materials lead to different KIC values. The test method and a prior heat treatment showed an influence on the KIC values and their reliability.

Bonding Behaviour of Polyetherketoneketone to Methylmethacrylate- and Dimethacrylate-based Polymers

Journal of Adhesive Dentistry, 2017

PURPOSE To investigate the impact of pretreatment and conditioning on bonding behavior of polyeth... more PURPOSE To investigate the impact of pretreatment and conditioning on bonding behavior of polyetherketoneketone (PEKK) to methylmethacrylate(MMA)- and dimethacrylate(DMA)-based polymers. MATERIALS AND METHODS 1200 PEKK substrates (Pekkton ivory) were fabricated, air abraded (110 µm, Al2O3) and divided into 8 pretreatment groups as follows: 1. Visio.link (VL); 2. VL+ opaquer; 3. Pekk Bond (PB); 4. PB + opaquer; 5. plasma; 6. plasma + opaquer; 7. plasma + VL+ opaquer; 8. plasma + PB + opaquer. A low-density cold oxygen plasma was used to treat specimens in groups 5-8. All pretreated PEKK substrates were bonded with either MMA-based polymers (denture acrylic: "Anaxdent acryline") or DMA-based polymers (veneering composites: flowable "Anaxdent dentin flow" or packable "Anaxdent dentin paste"). On denture acrylic, the anaxgum opaquer paste was applied, and on veneering composites, the anaxblend opaquer paste. All specimens were stored in water for 24 h at 37°C, and 20 specimens of each subgroup were additionally thermocycled (5°C/55°C, 10,000x). Tensile bond strength (TBS) was measured and analyzed with the general linear model analysis, Kaplan-Meier survival estimates, and Breslow-Gehan tests. RESULTS The combination of plasma and VL showed the highest TBS results, followed by VL and the combination of plasma and PB. The lowest TBS was observed among PEKK specimens treated with plasma and without pretreatment, followed by specimens conditioned with PB. The application of an opaquer layer increased the TBS. Bonding to PEKK with MMA-based polymers showed higher TBS results than with DMA-based polymers. Among DMA-based polymers, the flowable polymer bonded significantly better to PEKK compared to paste polymer. After thermocycling, the TBS decreased. CONCLUSION Sufficient bonding to PEKK is possible when plasma treatment is used in combination with the tested adhesives and an opaquer layer.

Modern CAD/CAM silicate ceramics, their translucency level and impact of hydrothermal aging on translucency, Martens hardness, biaxial flexural strength and their reliability

Journal of The Mechanical Behavior of Biomedical Materials, Jun 1, 2021

OBJECTIVES To investigate the impact of hydrothermal aging on Martens parameter (Martens hardness... more OBJECTIVES To investigate the impact of hydrothermal aging on Martens parameter (Martens hardness: HM/elastic indentation modulus: EIT) and biaxial flexural strength (BFS) of recently available CAD/CAM silicate ceramics. METHODS 220 specimens (diameter: 12 mm, thickness: 0.95 mm) were fabricated from six CAD/CAM ceramics in two translucency levels (LT/HT): (a) two lithium disilicate (Amber Mill, ABM; IPS e.max CAD, IEM), (b) one lithium metasilicate (Cetra Duo, CEL), (c) one lithium alumina silicate (n!ce, NIC), and (d) two leucite ceramics (Initial LRF Block, LRF; IPS Empress CAD, IPR). HM/EIT and BFS were measured initially and after hydrothermal aging (134 °C/0.2 MPa/100 h) in an autoclave. The Kolmogorov-Smirnov-test, t-test, one-way ANOVA with post-hoc Scheffé test, Kruskal-Wallis-test, Mann-Whitney-U-test with Bonferroni correction and Weibull statistics were performed (α = 0.05). RESULTS CEL and IEM showed the highest and the leucite ceramics the lowest Martens parameter. Within HT, ABM and NIC were in same initial HM value range with CEL and IEM. ABM and NIC showed lower initial EIT values than CEL and IEM, however higher than IPR. The lowest aged values were analyzed for ABM. After aging, Martens parameter decreased for LRF, ABM, and CEL. IEM showed the initial highest BFS, followed by ABM. NIC and LRF showed the lowest BFS. IEM and ABM presented the highest aged BFS. Hydrothermal aging increased BFS values for LRF (HT), IPR, CEL (HT), and NIC (HT) compared to the initial values. CAD/CAM leucite ceramics showed higher Weibull modul values compared to lithium silicate ceramics. SIGNIFICANCE The well-considered selection of ceramics in relation to the areas of indication has the highest influence on the long-term stability of restorations: CAD/CAM lithium disilicate ceramics presented the highest and leucite ceramics the lowest mechanical properties, whereas the reliability was better for leucite than for lithium silicate ceramics.

Journal of Adhesive Dentistry, Dec 1, 2012

Purpose: To investigate the influence of caries infiltrant application on the shear bond strength... more Purpose: To investigate the influence of caries infiltrant application on the shear bond strength of different adhesives on sound and demineralized enamel. Materials and Methods: Sound and artificially demineralized (14 days, acidic buffer, pH 5.0) bovine enamel specimens were treated with a caries infiltrant (Icon, DMG), three different commercial adhesives (unfilled etchand-rinse adhesive: Heliobond, Ivoclar Vivadent; filled etch-and-rinse adhesive: Optibond FL, Kerr; or self-etching adhesive: iBOND Self Etch, Heraeus Kulzer) or a combination of caries infiltrant and adhesive. The shear bond strength of a nanohybrid composite was analyzed after thermocycling (5000x, 5°to 55°C) at a crosshead speed of 1 mm/min. Failure mode was inspected under a stereomicroscope at 25X magnification. Results: In both sound and demineralized enamel, the shear bond strength of the caries infiltrant was not significantly different from the etch-and-rinse adhesives, while the self-etching adhesive showed significantly lower values compared to all other groups. Pretreatment with the caries infiltrant significantly increased the bond strength of the self-etching adhesive in both substrates and of the filled etch-and-rinse adhesive in demineralized enamel. While shear bond strength was not significantly different between the two substrates, cohesive failures were more likely to occur in demineralized than sound specimens. Conclusion: The shear bond strength of the caries infiltrant was similar to the etch-and-rinse adhesives. The caries infiltrant did not impair bonding to sound or demineralized enamel, and even increased adhesion of the selfetching agent.

The effect of different pretreatment methods of PMMA-based crowns on the long-term tensile bond strength to dentin abutments

Clinical Oral Investigations, Mar 2, 2014

The objective of the study was to test the effect of different pretreatments on tensile bond stre... more The objective of the study was to test the effect of different pretreatments on tensile bond strength (TBS) of adhesively bonded CAD/CAM-generated polymethyl methacrylate (PMMA) crowns to dentin. Two hundred human molars were prepared and divided into 20 groups (n = 10/group). PMMA crowns were pretreated thusly: Monobond Plus/Heliobond (MH), Visio.link (VL), Ambarino P60 (AM), VP connect (VP), and nontreated as control groups (CG). Two resin cements were used for cementation of crowns: Clearfil SA Cement (CSA) and Variolink II (VAR). TBS was measured initially (24 h water storage, 37 °C) and after aging (5,000 thermal cycles, 5/55 °C). TBS was analyzed using one-way ANOVA with Scheffé post hoc, unpaired Student t, Mann-Whitney U, Kruskal-Wallis H, and chi-squared tests. Within CSA, pretreatment with MH and VL showed higher initial TBS compared with AM-treated groups. All other groups showed no statistical differences. For MH, VL, AM, and VP in combination with CSA, a negative impact of aging was observed (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.001), whereas in all VAR groups, no impact was measured. Pretreatment with MH (p = 0.001) and VP (p = 0.008) presented higher initial TBS for CSA than for VAR. After aging, MH (p = 0.025) and VL (p = 0.034) cemented with VAR showed higher results than CSA. All tested groups showed very low TBS values. Pretreatments with MH, VL, and VP have minimally improved the tensile strength after aging. Although the tensile strength results were low, crowns adhesively cemented with pretreatments with MH, VL, and VP showed, after aging, a higher tensile strength than nontreated groups.

International Journal of Adhesion and Adhesives, 2018

Objectives: To investigate the impact of polyetheretherketone (PEEK) surface modification on tens... more Objectives: To investigate the impact of polyetheretherketone (PEEK) surface modification on tensile bond strength (TBS), acidity parameters (D) and surface properties. Methods: For TBS, 486 PEEK specimens were fabricated and air-particle abraded with 50 μm Al 2 O 3 according to varying pressure: 0.05, 0.2 or 0.4 MPa. Specimens were directly conditioned (n = 18/group): 1. Scotchbond Universal (SBU); 2. Clearfil Universal Bond (CUB); 3. Futurabond U (FBU), 4. Adhese Universal (AU), 5. G-Premio Bond (GPB), 6. Pekk Bond (PB), 7. visio.link (PCG/positive-control-group), 8. without conditioning (NCG/negative-control-group) and luted with Clearfil SA Cement. After thermal cycling (5,000x) TBS was measured. On air-particle abraded PEEK surfaces and different adhesive systems (n = 6/pretreatment) D was analysed by contact angle measurement, surface roughness tactile by profilometer and optical by SEM with 3Dimages followed by surface topography, EDX-and XRD-analysis. Data was analysed using 2-/1-way ANOVA, Kruskal-Wallis H-, Mann-Whitney-U-, Kaplan-Meyer-, Chi²-and Spearman-Rho-test. Results: PCG followed by SBU and AU showed the highest TBS and survival rates. PB air-particle abraded with 0.4 MPa presented comparable TBS with PCG. NCG and GPB showed lowest TBS. Specimens air-particle abraded with 0.05 MPa presented lower D-values than those with 0.2 or 0.4 MPa. PCG followed by PB showed higher Dvalues compared to SBU, CUB, FBU, AU and GPB. All air-particle abraded specimens showed embedded Al 2 O 3particles and for 0.2 and 0.4 MPa more roughened surface areas. Significance: The pressure during air-particle abrasion of PEEK restorations must be matched to the adhesive system. A general recommendation is not possible. Universal adhesives might be an alternative conditioning for cementation of PEEK compared to PCG.

$Research paper thumbnail of Impact of high-speed sintering, layer thickness and artificial aging on the fracture load and two-body wear of zirconia crowns$

Impact of high-speed sintering, layer thickness and artificial aging on the fracture load and two-body wear of zirconia crowns

Dental Materials, Jul 1, 2020

OBJECTIVE To investigate the impact of high-speed sintering, layer thickness and artificial aging... more OBJECTIVE To investigate the impact of high-speed sintering, layer thickness and artificial aging in a chewing simulator on the fracture load (FL) and two-body wear (2BW) of 4Y-TZP crowns. METHODS 4Y-TZP crowns (Ceramill Zolid HT+, Amann Girrbach AG) in three different layer thicknesses (0.5, 1.0, 1.5; N=192, n=64/group) were manufactured using CAD/CAM technology and sintered at 1580°C (high-speed sintering) or 1450°C (control group). Specimens were polished in two-steps and bonded to standardized CoCr abutments with Multilink Automix (Ivoclar Vivadent). 2BW after 6000 thermo- and 1,200,000 chewing-cycles employing enamel antagonists was determined using best fit machining. FL was tested before and after artificial aging. Univariate ANOVAs, post hoc Scheffé, unpaired t-, Kruskal-Wallis- and Mann-Whitney-U-test were computed (p<0.05). RESULTS High-speed sintering resulted in less 2BW of the zirconia than the control group (p=0.013). High-speed sintering (p=0.001-0.006) and an increase in layer thickness (p<0.001-0.012) resulted in higher FL values, while artificial aging led to a reduction of FL (p<0.001). SIGNIFICANCE As high-speed sintering resulted in less two-body wear of the zirconia and comparable or even higher fracture load results than the control group, this cost- and time efficient alternative presents promising mechanical results.

Impact of Recently Developed Universal Adhesives on Tensile Bond Strength to Computer-aided Design/Manufacturing Ceramics

Operative Dentistry, Jul 1, 2019

SUMMARY Objectives: The aim of this investigation was to test the tensile bond strength (TBS) bet... more SUMMARY Objectives: The aim of this investigation was to test the tensile bond strength (TBS) between different computer-aided-design/manufacturing (CAD/CAM) ceramics after conditioning using different universal adhesive systems and resin composite cement. Methods and Materials: Substrates of four CAD/CAM ceramics—1) VITABLOCS Mark II, 2) Initial LRF, 3) Celtra Duo, and 4) IPS e.max CAD (N=648, n=162)—were fabricated. VITABLOCS Mark II and Initial LRF were etched using 9% hydrofluoric acid for 60 seconds, Celtra Duo for 30 seconds, and IPS e.max CAD for 20 seconds. Substrates for conditioning using Monobond Etch & Prime were untreated. The following adhesive systems were used: All-Bond Universal (ABU), Clearfil Universal Bond (CUB), G-Multi Primer (GMP), iBond Universal (IBU), Monobond Etch & Prime (MEP), Monobond Plus (MBP), One Coat 7 Universal (OCU), Prime&Bond Active (PBA), and Scotchbond Universal (SBU). Conditioned substrates were bonded using a resin composite cement (Variolink Esthetic DC), thermal cycled (20,000×, 5°C/55°C), and TBS was measured using a universal testing machine. Data were analyzed using univariate analysis with partial eta-squared, Kolmogorov-Smirnov, Kruskal-Wallis, Mann-Whitney U, and Spearman-Rho tests (α=0.05). Results: ABU, MEP, and MBP obtained the significantly highest TBS, while CUB, IBU, and OCO resulted in the lowest, regardless of the CAD/CAM ceramic. SBU showed varying TBS results depending on the CAD/CAM ceramic used. ABU, MEP, and MBP showed no impact of CAD/CAM ceramic on TBS values. ABU, GMP, MEP, and MBP showed predominantly cohesive failure types in luting composite, while CUB and OCU demonstrated adhesive failure types.

International Journal of Adhesion and Adhesives, Oct 1, 2013

This study investigated whether the adhesion of novel generation of polymeric CAD/CAM resins to l... more This study investigated whether the adhesion of novel generation of polymeric CAD/CAM resins to luting cements would improve after use of different conditioning methods, and to evaluate the failure types after debonding. Two CAD/CAM resins (PMMA-and composite-based) were obtained (N¼ 600, n ¼15 per test group). The specimens were conditioned as follows: MH: Monobond Plus/Heliobond, VL: Visio.link, AM: Ambarino P60, VP: VP connect, CG: no conditioning as control group, and luted with conventional (Variolink II) or self-adhesive luting cement (Clearfil SA Cement). Two types of storage were performed: after 24 h water storage (37 1C) and additional 5000 thermal cycles (5 1C/55 1C). Tensile bond strength (TBS) was measured and data were analysed using 4/1-way ANOVA (Scheffé test), independent twosample t-test and Chi 2 test (alpha ¼ 0.05). For both CAD/CAM resins, no or lower bonding was observed for the non-conditioned or AM groups, regardless of the luting cement. The conditioning with MH, VL and VP showed significant increase of TBS. In general, bonding on exp. CAD/CAM composite presented significant higher values compared to PMMA-based artBloc Temp. Variolink II showed higher TBS in combination with artBloc Temp. After conditioning with MH and VL predominantly cohesive failures in the luting cement were observed. All other groups showed adhesive failure. Aging level did not affect the TBS. The bonding properties of the CAD/CAM resin materials are dependent of the targeted selection of the conditioning method and luting cement. Composite-based materials showed higher bonding properties to luting cements than PMMA-based.

Evaluation of modern bioactive restoratives for bulk-fill placement

Journal of Dentistry, Jun 1, 2016

To investigate the impact of storage up to one year on the micro-mechanical properties of dental ... more To investigate the impact of storage up to one year on the micro-mechanical properties of dental bioactive restoratives (R) used for bulk-application and their intermediate layer (IL) to dentin (D). One giomer bulk-fill resin composite (RBC) and one glass-ionomer cement (GIC) were applied in 5-mm deep Class I cavities, which were prepared in 50 sound human molars. Specimens were stored in distilled water at 37°C for 24h, one week, one month, three months and one year. The variation in micro-mechanical properties (indentation modulus (YHU) and Vickers hardness (HV)) were determined in 100-μm steps in line-profiles located parallel to the tooth axis, starting 0.1mm from the filling surface, through the IL in between R and D, and ending 300μm in D. HV and YHU were influenced by the material (p&amp;lt;0.001, partial eta-squared [Formula: see text] =0.011 and [Formula: see text] =0.395), immersion duration ( [Formula: see text] =0.081, [Formula: see text] =0.081) and depth ( [Formula: see text] =0.050, [Formula: see text] =0.091). The micro-mechanical properties progressively increased with immersion time in both restoratives, with a comparable time-dependency pattern, but to a different extent. IL showed weaker mechanical properties compared to more superficial cavity areas, which were maintained in RBC and even enhanced in GIC during storage. After one year of storage HV ranked in the following sequence: GIC: D: 61.4±7.25-N/mm(2), IL: 86.0±23.63-N/mm(2), R: 112.3±30.36-N/mm(2) and RBC: D: 67.2±11.55-N/mm(2), IL: 76.7±18.88-N/mm(2), R: 94.1±12.28-N/mm(2). No degradation with aging was identified in the giomer restorative. The gradual ascending transition in micro-mechanical properties from D through R identified in both restoratives might have a positive effect on the bond quality. Giomers represent a new category of restoratives with promising clinical behavior and good mechanical stability up to one year of aging under simulated clinical conditions.

Journal of Prosthetic Dentistry, Mar 1, 2021

Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) is classified as the most robust restor... more Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) is classified as the most robust restorative ceramic 1 and is characterized by exceptional mechanical properties and biocompatibility. 2 By adding different additives and dopants such as yttria (Y 2 O 3 ) and alumina (Al 2 O 3 ), several variants of Y-TZP have been developed. The development proceeded from a framework material for fixed dental prostheses in the anterior and posterior regions to monolithic posterior restorations and then to monolithic anterior restorations. The substantial improvement in optical properties was achieved with the aim of preserving the mechanical properties. According to ISO 6827, 5 a minimum flexural strength of 500 MPa is required to fulfill the requirements for a class 4 material

$Research paper thumbnail of Flexural strength, fracture toughness, three-body wear, and Martens parameters of pressable lithium-X-silicate ceramics$

Dental Materials, Mar 1, 2020

Objectives. To test and compare five pressable lithium-X-silicate-ceramics on their mechanical an... more Objectives. To test and compare five pressable lithium-X-silicate-ceramics on their mechanical and wear properties. Methods. Specimens were pressed and prepared from: i. Amber Press (AP), ii. Celtra Press (CP), iii. Initial LiSi Press (IL), iv. Livento Press (LP), and v. IPS e.max Press (IE). Four-point flexural strength (FS), SEVNB fracture toughness (K IC ), three-body wear (3BW), Martens hardness (HM) and indentation modulus (E IT ) were measured. For CP, FS and HM were measured with and without additional Power Firing. Each subgroup contained 15 specimens. Data were analyzed using Kolmogorov-Smirnov, one-way ANOVA followed by Scheffé test, Kruskal-Wallis-H-, Mann-Whitney-U-, and Spearman-Rho-test (p < 0.05). The Weibull modulus was calculated using the maximum likelihood estimation method. Results. AP and CP presented higher FS than IL. LP presented the highest Weibull modulus. CP showed lower K IC values than AP, and AP was not significant compared to LP and IE. The most 3BW material loss was observed for CP. CP revealed higher HM values than the remaining ceramics. IL presented lower E IT compared to AP and CP. The following correlations were observed between the test parameters: 3BW with FS (r = 0.279, p = 0.015), with HM

Dental Materials, Oct 1, 2019

OBJECTIVE To test the impact of zirconia pretreatment and aging on flexural strength and phase st... more OBJECTIVE To test the impact of zirconia pretreatment and aging on flexural strength and phase structure. METHODS For flexural strength measurements, 180 3Y-TZP 0.25 specimens were fabricated and pretreated: (i) air-abraded (105-m alumina, 0.25MPa), (ii) air-abraded (50-m alumina, 0.25MPa), (iii) air-abraded (30-m silica-coated alumina, 0.28MPa) (iv) non-pretreated. Each pretreated group (n=15) was aged: (a) hydrothermal (134°C, 0.23MPa, 2h) (b) in a mastication simulator (1,200,000×, 5/55°C) and (c) not aged. The fractured specimens were stored dry for 5 years (23°C) for analysis of phase transformation. Additionally, specimens were fabricated from 3Y-TZP 0.25 (n=12) and 3Y-TZP 0.05 (n=8), pretreated (i, ii, iii, iv), and hydrothermally aged. Each air-abrasion method was alternated using 0.05, 0.25 and 0.4MPa pressure. The phase transformation was examined by Raman spectroscopy and surface topography by scanning electron microscope. Data were analyzed using univariate ANOVA with the Scheffé post hoc test and partial-eta-squared ( p ²) (=0.05). RESULTS The highest impact on flexural strength was exerted by the pretreatment ( P ²=0.261, p<0.001), followed by interactions between pretreatment and aging ( P ²=0.077, p=0.033). Non-pretreated and non-aged specimens showed the lowest monoclinic percentage. Hydrothermal aging and 5 years of storage at room temperature increased the monolithic percentage of 3Y-TZP 0.25 . The highest phase transformation was observed in groups air-abraded with 105-m alumina particles. Increasing pressure during the air-abrading process increased the content of the monoclinic phase in zirconia surfaces. SIGNIFICANCE Air-abrasion with 30m silica-coated alumina powder can be recommended for pretreatment of 3Y-TZP 0.25 and 3Y-TZP 0.05 . For air-abrasion using alumina powder lower pressure should be used.